solar still

JP7 DIY Solar Stills.

solar still marine survival DIY make making Always try to improve society rather than just take from it. Until then, lawyer stuff. Copying, duplication or transmission of this material whole or in part is not permitted without the written permission of the author. The contents of this text are for illustrative purposes only. Do not act on this information. Errors and omissions excepted. Contents subject to change without notice. All material herein is subject to copyright, patent and other intellectual property rights. All rights reserved. Copyright (C) J.Partridge. 2003 2005.

Please note: In these days of litigation taking the place of natural justice, it is necessary that those wishing to read the monograph must understand that they must not, nor will ever hold the author responsible for any damage or injury. I put my knowledge on the web to help make a better world, not so that some damn fool can sue me. Many websites are being shut down through legal threats from parasitic lawyers. One of my favourite websites on airfoil design has recently shut down simply because of lawyers. As lawyers get richer the rest of society gets poorer. Always vote to keep lawyers out of politics. Have a nicer day :) Due to a plague of parasitic lawyers, no one may read this. Stop reading now.

Solar Stills.Version 1d. Dec 2007. Contents. Introduction. Design. Types of inflation designs. Types of supported designs. Welding plastics. A basic inflatable solar still. Adding the pipes and tether. Flat base. Keel type. Testing. Water storage. Variations on the theme. A strong inflatable solar still. A thin piano wire solar still. Survival solar still. Beach solar still. A solar still for the side of a life raft. Desert still. Inner tube still.http://www.btinternet.com/~jhpart/bksolar1.htm (1 of 29) [2008-03-25 22:34:32]


Begging. Preamble: Unfortunately evaporation or osmosis are the only commonly used and reliable methods at present for turning sea water into drinking water. It is a pity that modern chemists have not developed a tablet or powder which can combine with dissolved salt and turn it into a harmless sediment. Carrying this in compact, pint sized, sealable plastic pockets could hopefully turn undrinkable sea water into safe drinking water. Adding a micro fine particulate filter would also help. Do not hold your breath, as the elements of sodium and chlorine are very tightly bonded and therefore are not going to change the laws of nature easily. The solution (no pun intended) may well be to bond this difficult molecule with something which will allow sedimentation, evaporation or filtration by using inherent energy or mild human power. A chemical method is available but rather bulky. If there are any genius chemists out there wanting to make a fortune, please do so. I am also reconsidering the osmosis designs as they leave a lot to be desired. Day after day, day after day, We stuck, nor breath nor motion; As idle as a painted ship Upon a painted ocean. Water, water, every where, And all the boards did shrink; Water, water, every where, Nor any drop to drink. (Rime of the Ancient Mariner. S.T.Coleridge.) Introduction. A solar still is a means of turning undrinkable sea water into drinkable fresh water. Solar stills are renown for low production rates, and are an emergency backup item, but because they are small and compact, a handful are easily made and carried for when the situation becomes truly desperate. commercial designs cost money and therefore considered by many as almost a luxury, but they are very cheap to make at home, as described here. So make yours and store them safely with the liferaft or emergency grab bag on your boat. Even if you have solar still in your liferaft kit, there is every reason why you should add a few more. Solar stills work by evaporating the water molecules in the sea water reservoir, leaving the salt behind. The evaporated water vapour is then condensed back into pure water on a cold surface, then gathered for use. It is possible to drink salt water, but it is detrimental to the human body in any but the smallest quantities. Salt water can be used to swill out a drying mouth, but drinking it can lead to vomiting andhttp://www.btinternet.com/~jhpart/bksolar1.htm (2 of 29) [2008-03-25 22:34:32]


worse. Drinking sea water is dangerous and some means to make drinking water without the salt and any other impurities is needed for long term survival over a few days or more. There are many ways to obtain drinkable water, such as using blue ice in Arctic and Antarctic climes, where the salt content is safely low or zero. Catching rain is also possible, but a large catchment area is important and also storage containers. The problem with solar stills is that they are expensive and rarely used, so buying a commercial item for a mariners grab bag is not always a high priority. Worse still, they are expensive and you may well need plenty of them. By making your own and testing, you can decide how many you need after the first one has been successful, then make them easily and for pennies. Likewise, for non-maritime survival kits, a solar still is rarely a top item when there are exected to be other means of gaining water, where food and shelter are normally top of the list of a land survival kit. So most people have a problem, that solar stills are desperately needed in just a few situations, or are too expensive. The obvous answer of course, is to carry the equipment, or be able to make a solar still from whatever is available locally or by carrying minimal components. Like all the best survival skills, they are carried in the head, which is always with you and takes up no room or weight. This is the aim of the page, to get the reader to understand the basics and skills, then be able to survive with whatever is carried or found. Carry your survival in your head. Therefore this web page assesses the possibilities for making solar stills as an affordable addition to a sailors grab bag and perhaps used in land based situations. Also included is a rough survival approach to making your own stills from whatever is left lying around on the beach. Please remember that solar stills are just one string to the survival bow. In polar latitudes, then icebergs become a good source of fresh water, especially if you can smash them into sizeable chunks and keep them floating alongside in bin bags as they melt. There is also the option of collecting rain by spreading out a large sheet above any raft to collect the rain water into plastic bags. Some fresh water can be obtained from fish, especially their eyes, but this also cannot ensure long term health. None of these methods are guaranteed, so being able to make drinking water from sea water is still of paramount importance. The reverse osmosis pump will make drinking water from the sea, but needs a lot of pressure to work. In my opinion, some commercial osmosis pumps are very poorly designed, and are recommended for use at night, when exertion is less conducive to sweating. So always modify them if needed, before they arehttp://www.btinternet.com/~jhpart/bksolar1.htm (3 of 29) [2008-03-25 22:34:32]


packed away. The modifications can be simple but very effective. I have redesigned and modified some of the worlds best equipment to be much more affordable, reliable, safer and easier to use and I recommend you also take an open minded approach to survival kit. My valve block for the Katadyn filter is easier to use, far more reliable and survives much better. In many survival situations, a solar still will be needed. The 12 stages of dehydration. 1 Thirst. 2 Discomfort. 3 Loss of appetite. 4 Nausea. 5 Headache. 6 Dizziness. 7 Speech difficulty. 8 Breathing difficulty. 9 Inability to walk. 10 Failing senses. 11 Inability to swallow. 12 Collapse. Making your own solar still comes into two main forms. Either through forethought, such as a mariner intending to add extra water capacity to their survival grab bag, or as in all survival situations, where any available item must be used. Knowing how to make a solar still not only makes it easier to create one in a survival situation, but also to keep it working while any chance of life exists. Before looking at making a solar still, let's first look at what it is and how it works. The solar still is just like any other still, insofar as it uses heat to turn a liquid to vapour. The vapour is then moved to a cool surface and cooled (condensed) back into a liquid. This is called distillation. The vapour for marine use is evaporating sea water to make pure water vapour and leaving the salt behind. The vapour is allowed to rise, then condense against a cooler surface where it turns back into a drinkable liquid. The main purpose of a still is that it tends to leave all impurities behind, such as reducing the water content of alcohol, as in pocheen, or leaving the heavier fractions as in an oil refinery wanting to distilhttp://www.btinternet.com/~jhpart/bksolar1.htm (4 of 29) [2008-03-25 22:34:32]


out the lighter fractions such as petrol and paraffin. (the lighter fractions on the heated tar rise up the tall metal towers we see in oil distilleries.) Likewise in a solar still, the user wants the sea water to be turned into pure water by vaporisation then condensation. The distillation process requires some special features, but they are always fairly easy to make and perhaps add a few subtleties to encourage them to perform well. The first is to create a heating area. For the sailor, this is usually a large inflatable clear plastic ball, acting like a greenhouse to capture the sun's radiation. Into the heating greenhouse area is placed a source of impure water, such as sea water, and this has to be presented such that the surface water evaporates easily, usually a wick. The solar still also needs a condensing surface. This is usually the outer surface of the balloon, where the cooler outer air wafts over it. The fresh water condensate must then be collected and stored in a safe manner. General design features. A typical solar still will have the following design aspects. It must be there when needed. - Therefore it must be affordable and be packed safely in the grab bag or with the life rafts or life belts. (An expensive solar still no-one can afford, is of no use.) It needs a large surface area, so the internal heating area does not loose heat, this also presents a larger outer surface cooling surface for condensation. (This is usually created by making an inflatable balloon design because it can be packed really small and will float on the sea.) A means to evaporate the sea water. The primary water source is often a wicking cloth which sits inside a pool of sea water inside the 'glasshouse' area and allows a large area for the salt water evaporation. the wick is usually a dark colour to absorb the radiant power of the sun, thereby allowing faster evaporation. A means to introduce and remove the two liquids. Small plastic pipes are used to introduce the sea water and extract the fresh water. A means to remain in a safe working position. The balloon type of still will often need a keel or weight to keep it upright and to prevent the condense from spilling in mildly rough seas. The disadvantages of the typical design are in the limited use of the solar still; it only works well in good sunshine or where the suns rays are reasonable. It tends to buck about in the waves, so needs a stabilising or other device so that the sea and fresh waters do not spill inside. It is easily prone to puncture and therefore a puncture repair outfit is needed. It needs to be affordable or easily made from simple components.

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Therefore the output of a solar still is not very good, and is only a back up solution unless many are used and if fresh water storage is included for overcast days. The biggest problem is therefore affording a few solar stills, or being able to create one in any survival situation. The science is not difficult, neither is the technology or manufacturing skills. This web page takes various approaches to solar stills and they are all cheap, because an expensive solar still that is never available is useless. This monograph considers the materials and the manufacturing skills that are easily available to everyone, no matter where they are in the world, rich or poor. Simple solar stills are one of my minor technology projects for secondary school kids. I'm an unemployed teacher of technology looking for work in Plymouth, a maritime city with lots of poor people. - I'm just one of thousands of British B.Ed. B.Sc, etc, looking for work - gizzajob, please ! Be warned: Solar stills do not make much water, especially in colder climes and therefore must be considered only as part of an overall strategy for finding drinking water. Their main advantage is that they can create drinking water where it is desperately needed; in hot climates, far from rain bearing skies. No matter what the survival situation is, it is imperative to remain with the last known radioed position, and later to row or sail or drift, judicially using a sea anchor towards any known shipping lanes or coastline. See my lifejackets monograph. Inflation versus a structural support. The solar still needs a large internal volume. This can be either an inflatable design, or have a central pole and mid point ring or a bendy arch design or other variations on creating large internal volume with minimal packed size or complexity. The inflatable design and simple supported designs are ideal for prepared survival equipment, where people are to survive such as in a raft. A hoop or pole and ring or flat panel are ideal for designs made from parts found from a coastline and from any trees or bamboo. An important design concern is if the solo user is injured, where anything other than an inflatable design may be difficult to get working, especially in moderately rough seas. You may wish to consider the inflatable type for solo use, such as a mariners grab bag. The inflatable design is also light, compact when folded. The main approach of this monograph will often require some plastic welding skills and therefore a soldering iron or a hot metal stick will be needed, although I've kept this down to the minimum for ease and reliability, with a few basic designs using no technical skills, as described later. There are other approaches to making a solar still and some of these approaches will assume a dire survival situation, or simply bored on a sunny beach.http://www.btinternet.com/~jhpart/bksolar1.htm (6 of 29) [2008-03-25 22:34:32]


The simplest solar still is a sheet of clear plastic over a large, wide hole scraped in a damp piece of ground, preferably in sunshine to heat up the damp ground, and a cool breeze to help condensation. Place a stone in the centre of the sheet, so the condensation drips down to the centre and over a water container. Do not expect too much water. the requirements for a basic home made solar still. This section assumes a prepared still for a precarious maritime environment and will require the solar still to float in the sea. The design must be able to float, therefore it will probably be either an inflatable design, or a self supporting volume. As the inflatable design is considered first as it will pack down easily and easy to deploy. The design needs to be reasonably large, as it will otherwise be unable to sustain enough water production for an otherwise lost soul. The volume is to be the same as most commercial designs and thus be about two or three feet in diameter, although a lot of leeway in overall scale is perfectly acceptable. This general scale will give a reasonable heat regime between the cooler outer surface and the inner heating area. Because this is inflated, then the sealed nature of the design will need the user to replace the condensate removed with similar amount of sea water, and to occasionally replace the reservoir of increasingly saline water. Likewise the condensate must be able to collect separately and be regularly sucked out without deflating the solar still. they may be capsized by a gust, or rouge wave and loose the precious condensate, so regular collection is important. When bad weather approaches, the still must be deflated and packed safely away.- We all delude ourselves and assume we will be floating in warm, calm waters, but this is rarely the case. Nor should it ever be assumed. - Always plan for the worst scenarios. To maintain stability in the waves, a keel of some form is often needed to prevent undue wobbling around and to ensure the condensate can be retained separate from the sea water reservoir in a roughly upright design. Some bobbing around, or rotation around a central point can help encourage condensation to run down the inside, and hopefully keep the still at maximum production. Therefore the design must be moderately stable in the sea. The extremes of design include 'buoy' designs, with a long vertical lower axis with a keel low in the water. This vertical alignment would encourage the condensate to flow easily down to the collection area. The other extreme is if the solar still was wide and flat, then the still would wobble too much and some condensate may drip back to the saline reservoir unless a suitably curved shape is used. Every drop counts. With a basic design, the options for plastic designs will come down to using a long, clear plastic tube, then taper the ends as needed. Alternatively, the design can be made from flat plastic sheet, which is then welded to shape into something akin to a beach ball.



The use of clear industrial plastic tube is of course, much stronger and easier to make good DIY welds. Finding plastic tube of this diameter and gauge (thickness) is harder to find, so keep your eyes open, such as packaging for various of the larger domestic goods. Nose around building sites or their suppliers, where temporary air venting is needed, where long plastic tubing is often used. A 20 quid roll could probably make fifty solar stills - 40p each. When only flat sheet is available, then it may be time to learn how to weld plastic as described later. The common plastic of choice for clear solar cells is polyethylene, or polythene as it is commonly called. There are tougher plastics, but are harder to weld, so consider these when you have perfected your skills. Polythene sheet is available many gauges (thicknesses), so it is up to the user to decide the best compromise between strength and compactness. A grab bag may prefer a few, thin sheet stills, while a six person raft may have the room to fulfil the needs of larger stills made from stronger materials. Usually the thickness will vary with the diameter of the original tubing, so the compromise is fairly well balanced for most uses. The internal components are minimal, but must be carefully designed and made well. The internal components consist of a partially sealed salt water reservoir, so that the cloth wick can be kept moist. This must wick up to the heating area, and around this will be the means to capture the warmed water vapour as condensate. The central cloth must be a wickable item; towelling, pertex or similar. The wick must also be dark, as this must absorb most of the suns radiant heat. Many modern hiking fabrics are light and wickable, but do not hold much water, so three or four layers of this makes a much better wick, so the salt water source gets a chance to absorb across the wick for greater evaporation. Cotton tends to rot after a few years if not completely dried after testing. If deciding upon a cotton wick, or any biodegradable materials, then the solar still must be packed completely dry and airtight to prevent it rotting in the many years before it may be needed. Always choose good, dark wicking materials. The wick must be able to wick moisture upon to a reasonable level, so check your options by testing various fabrics held above a saucer of water, with their ends in water to see how well they get wet to the best heights. Drape strips of potential materials over a bar and dip the ends in a bowl of inky water to highlight the true height of the moisture. After half an hour, measure the appropriate height of the wicked moisture. Preferably do this inside a sealed container, so the environment is very humid, thus will not give false readings of excessive evaporation, which may make a perfect material look as it its not so effective as it really is. The simplest test rig is a 4 pint, (2l) clear fizzy drinks bottle, left out in the garden in sunlight. A few close layers of finer weave can often work better, but always test to be sure. If this section is omitted, then the still will not work efficiently. The wick must present as much damp area to generate the maximum amount of water vapour.



Do not confuse good evaporation in dry, sunnier climes where the wick does not get wet at the top, as having poor wicking properties. In most cases, the water vapour will keep the wick damp across all its surface, but always check how far up the water permeates in the initial minutes, preferably in a very humid zone to mimic the internal conditions of a solar still. The wick will allow the salt water to evaporate, then the water vapour will condense against the cooler outer walls. The condensate will then run down the inside of the outer surface to collect in a ring around the base of the clear upper section, ready for drinking. The design of the collection area is vitally important because it will be bobbing around in the sea for hours and must restrain and contain the drinking water without contaminating it with the central sea water reservoir. The vital condensate will be a small amount, so a small drainage area or pocket in the side of the still can make safe collection and removal easier. To safely collect the condensate as it runs down the inside, a skirt is needed, so the liquid is safely trapped and guided to the outer collection ring. The internal skirt must have a perfect waterproof seal with the outside surface and making this join can be a problem. An alternative is to simply tuck the lower part of the main tube back inside itself to make a perfect collection area. This will allow a heavier lower tube to be welded or tied to the upper part and ensue the chance of greater survivability from flotsam and jetsam. Or if a very long piece of tube, then the base of this folded design can make the skirt and the lower area gathered and tied to make the base of the solar still as shown in the drawing below. The size of the inner hole of the condensate collection skirt must allow the cloth wick to have its base in the salt water, but also allow the upper part of the cloth to catch the maximum amount of sunlight for heat absorbtion. Therefore the wicking cloth should present the maximum area to the sun, but without causing contamination of the fresh water. The central skirt hole is therefore not small, with the wick protruding and presenting plenty of area. As the wick is driest at the tips, then this is not going to contaminate the condensate. But the splayed cloth will need to be supported in some way which can be folded easily for storage. This will need either a set if internal lugs to support the wick, or some form of lightweight springy frame tied to the apex. Some commercial solar stills use a wick which is flat and spread across the base of the glasshouse area, with the condensate collecting in a small ring around the sides, but this does not allow such good efficiency at lower sun positions or in rough seas and only works best at midday in equatorial waters. It is also harder to make. A variation on this is to have the wick as a large diameter central dual cone tube, with the skirt attached low on the wick, so the wick becomes a central cone, and this will also greatly reduce the chance for sea water to splash out and contaminate the condensate, but this also limits the area of wick presented to the sun, and compromises the steep angle of the condensate collection skirt. there is noting wrong with such a design, but slashing can be reduces with sponges, and thereby allow the wick to catch the maximum amount of the suns rays. Both designs have their pros and cons, so it is up to the builder to adapt and craft their design to best advantage.



The lower, keel section is a problem due to stability as such a lightweight design tends to sit lightly on the sea, and thus will always be prone to bobbing around. Therefore the keel needs to be well designed to prevent being dragged by currents and still allow it to lie upright with minimal bobbing. The keel mass wilt therefore be decided after testing, then a suitable mass added to the base, while still being convenient to pack. Therefore the underwater section should be either a curved base which floats over the water, but keeps mainly upright, like a kiddies inflatable plastic wobbly snowman, or a thinly vertically aligned so it stays upright as much as possible even in poor sea states, similar to a fishing float. If a wide, curved base is used, then three cords supporting a lower weight may be used to improve vertical alignment. Any separate keel section must not displace much water, otherwise it may cause excess bobbing. An extra piece of lead can help, but must be carefully restrained to prevent the metal from damaging the rest of the delicate design while packed away for many years. If an open design of sea water keel contains plenty of sea water, perhaps using a separate lower water filled keel chamber using a sea filled sponge, it can act like a sea anchor and keel. I prefer to mount any lead in a little foam. Some bobbing is NOT a problem as this will encourage condensate to move and encourage the wicking action of the salt water section of the cloth. The problem of floating with good upright alignment is easily accomplished by the use of a tether which , when blown downwind, will cause the still to remain upright. on a beach ball design, this can be a mid point tether, and in a tall design, then a Y tether holding top and bottom. The harder it blows, the more upright it will try to remain. And when no wind blows, then there may well be fewer waves to worry about. From the above can be seen a general trend for two types of solar still. The simple spherical beach ball design. this will tend to roll, so the wick and skirt must be designed appropriately. A simple plastic balloon is possible and makes a lightweight and easily packed item. The vertically symmetrical shape in circular platform, offers a large greenhouse and condensation area, but a small buoyancy area to support the upper in a vertical manner. Types of supported designs. The central pole with a mid point ring. There is also the two arched springy bar design. These could be made from bamboo or piano wire, as it is light and fairly resilient. They also allow the central wick to be easily and more widely supported. These will not be easy to assemble and loosing any component in the sea is disastrous. Therefore any such designs must have constrained components. Welding plastic. The most common design will be an inflatable solar still and will often need welding. It is possible to glue plastic but polythene is a very poor choice, as the resultant glue is not going tohttp://www.btinternet.com/~jhpart/bksolar1.htm (10 of 29) [2008-03-25 22:34:32]


survive bending and folding, nor the pressure of all but the lightest of inflation pressures. Learning to weld polythene is highly recommended. To learn how to weld plastic, practice by placing two edges on top of one another, on a piece of wood which will not soak away the heat, then applying a hot, wide, smoothly rounded metal bar, moving it across the plastic gently enough to melt them together, - but not slow enough to cause the plastic to loose its thickness. A large, smooth curve will be less prone to causing a narrow or thin weld. Ideally, the weld should be almost the same thickness as the original plastic, and have a wide molten welded zone with no ragged edges. If no other tools in a survival situation, then a cigarette lighter with small flame is also possible. When many decent welds are made, it is vitally important to test by pulling them apart to see just how strong they really are. Always make many test pieces to get the hot steel to the perfect temperature. Welding takes time and plenty of practice and a few tricks. To make neat lines, use a wooden guide. Where complex curves are used then careful freehand skills will be needed. Another way to melt plastic is to place the two edges together with the free edges both facing upwards, then using a cigarette lighter or small flame or candle to melt them together into a thicker bead as they melt. I prefer to clamp the intended join between two pieces of wood to ensure a neat and strong bead of weld. This latter form is stronger because it has a straight line with no weak bumps, but the resultant open 'ridge' join will have the plastic sheets at a poor angle where they join. This weld is easier in a survival situation where you have scavenged lots of pieces of plastic sheet. When stranded on land, never use any cigarette lighter to weld plastic, but use it to make a fire, so your cigarette lighter remains ready for further survival use. You can then heat a stone held in cloth or a charred piece of wood to melt the plastic. Once a plastic tube can be made by good welding, it must be modified. This may often require spot welds to attach the wick support and therefore the spot welds will become a weak point. A spot weld should therefore be strengthened with an intermediate piece of plastic to give some extra strength. In high stress areas, it may be preferable to fit strengthening sheets either side of the main sheet. If making a flat, circular solar still from a tall, tapered, clear upper section and a flat, darker lower section, then it is possible to make a neat main outer weld by clamping the halves together between two old steel car or the larger bike wheel rims, or any metal disc, then trimming the plastic to be 1/4 to 3/8 the of an inch proud, then melting them together with a soft flame for a very neat join. The advantage is that the steel is cold and therefore, - somewhere between the overly hot flame and the cold rim - will be the perfect heat zone for the perfect welded seam. This will also result in a neat and smooth curve which has no high stress points. Clamping two or three sheets together between two old car rims and using a soldering iron or hot bar is very simple technology. If deciding to make ten welded solar stills for pennies, then a pair of old car rims from a dump, the edges smoothed and polished, will make manufacturing so much easier. A solar still will also need two pipes to be fitted, one to insert and remove salt water, the another to inflate the still and to drain the fresh condensate. Welding a plastic pipe through a plastic sheet is not at all easy and it also becomes a high stress point. In some designs as mentioned later, this will be avoidedhttp://www.btinternet.com/~jhpart/bksolar1.htm (11 of 29) [2008-03-25 22:34:32]


wherever possible, but if you are getting rather good at plastic welding, then a much neater still design is possible. Finally a strong tethering point will also be needed so the still does not float away. Spot welding. Moulding the details into the plastic before final assembly, will need spot welding and are, not surprisingly, simple small spots of weld. This is done using a smooth rounded heated metal item such that the weld melts at the centre, making the join, but smooth out towards the edge to give a low stress join. For example, to attach a tether, the string will need a loop to attach to, so the spot weld can be done with a strong piece of similar plastic, attached to the strongest point in the design with, perhaps four spot welds. Spot welds can easily pull out of any plastic because it is a single point of stress, so they are usually done as sets of welds, such as four or more so that the stress is greatly reduced and therefore more reliable. At high stress points, it may be prudent to fit a strengthening sheet either side of the main sheet. Making a basic inflatable solar still. Not everyone likes welding plastic, so here is the most basic design I can come up with, other than the pop bottles mentioned later. Because this is a simple design, anyone can make it with little hassle, if they can find suitable industrial plastic tubing. The size does not matter too much. Too small and it can act as a test item. Too big, no one really cares as long as it works. Should only cost pennies to make, or for free. The process is to learn how solar stills work, so you carry the subsequent knowledge in your head, and this is the priceless part. Where most people can afford to carry just one commercial solar still, this design allows many to be carried for little effort or cost or as a roll of clear plastic tubing, ready for a waterproof sleeping bag, or water carrier, or a solar still, dependant upon how your survival situation pans out. The picture opposite shows the most basic design. It requires no welding if you can find suitable clear tubing. Otherwise just a simple seam weld for make tubing from sheet is needed. It needs a long tube, or two similar diameter tubes. This design ( No. JPs4e) is crafted to be very simple to make, robust in use and sit very well in the sea. It is surprisingly effective for little effort and minimal cost. This design is based on an eight foot long clear plastic tube, which can be used as a survival sleeping bag in cold or wet areas, as the kit may be needed in any or allhttp://www.btinternet.com/~jhpart/bksolar1.htm (12 of 29) [2008-03-25 22:34:32]


possible survival situations. Where you need a solar still, you probably don't need a plastic sleeping tube and vice versa. Therefore carrying the tube, pipe, string, wick and the concept and skills in your mind, then the survival kit is more likely to be of greater use. By using a long, folded plastic bag, such a finished design can also be deconstructed to give a large polythene bag for containing pieces of iceberg if you are stuck in northern latitudes, or give some fishing line and a small piece of wicking cloth for drying out the base of a life raft and a sheet to catch rain water or act as a shelter. Be prepared. Do not worry too much about getting the ideal sizes at this stage, as even a small or poorly made solar still can be used to assess its abilities. As skills get better, then your own Mark II will soon appear, as they cost pennies to make. Eventually you could make solar stills as good as the very best. Take a large clear plastic tube (perhaps 6 ft long and 3 ft diameter) and taper one end by careful folding, do the same at the other end and blow inside like a balloon to inflate to get a general idea of the overall working size. If no large clear tubing is available, then make a long tube by welding a joining seam. The plastic covering of a new bed, or such like from DIY stores is ideal. Leave some overlap rather than a neat join, as this also gives some possible attachment points. See welding. Make sure all weld lines are smooth so there are no tight spots which can cause high stress points. At the apex, add ten lengths of thin cord, such as sewing thread, which will dangle down the inside of the greenhouse section, then gather and tie the apex with string to make a temporary seal. At this stage, just leave the top with plenty of extra tubing and cords, so the final design can later be adjusted to perfection at this upper seal. Four cords to hold the skirt, and four cords to hold the splayed wick, plus to threads will run centrally, which can be used to pull the top and bottom together to make a squatter, more spherical design if so desired after final adjustment. Gather the base of the tube, test by inflating by mouth, then fold and tie off the other end and leave to check if it deflates over a few hours to check if your gathering and tying is moderately air tight. It does not have to hold a high pressure, but be able to hold its own shape and its weight in the sea, so a couple of large socks will be enough for applying a lightweight load on the inflated section.



Now assess the height of the design. Too tall, it will be blown sideways by wind, and too small will not make a decent green house effect. A spherical or slightly tall aspect ratio above the sea level is often best. The upper clear area where the water vapour will condense against the cooler surface should ideally be more vertical, so the water will naturally trickle down the inside surface for collection. The resultant design will probably be less than perfect, either be a thin design or a wide and squat design, dependant upon what tubing is available or personal preference, as there is no truly perfect design, but think about what is happening and make it happen to the best of the materials ability. While un-inflated, the assembly can be done on a table to get the basic layout. But the base is occasionally gathered with a pipe, then inflated to check the relative sizes, shapes and positions of the internal structure. Internal Skirt. The upper greenhouse section must now be given an internal skirt to collect the condensate. This will need some safe collection point, especially in rough seas, so that the fresh drinking water won't spill. Therefore the internal skirt should have a natural drain zone all around the base, to act as a condensate collection zone. This is where the fresh water suction tube will be placed. As the condensate collects, the solar still should later be weighted slightly towards the pipe to further encourage drainage into this area. Welding such a skirt is common on commercial designs, but I cannot recommend this in a basic design as it becomes a weak point in any survival strategy. There are alternatives to welding the skirt, such as folding the base of a long tube back inside the design, or using a second tube inside the main tube, then tying them near the base to make a good seal. See sketch. for this example, I'm folding the bottom of the tube back into the main section of the tube to make the skirt. this has to advantages, one, it improves air tightness and secondly, the bag can be dissembled and uses as an emergency sleeping bag or rain catcher or storage tube if not needed as a solar still. The skirt is held inside using the four cords from the top. the skirt can be gathered at four nodes and secured by the cords, then pulled further up the solar still, during later adjustments, once inflated. Wick. The wick is made from a few layers of fine black cotton cloth or other excellent wicking material. Black absorbs the heat of the sun, so a pale colour is not recommended. To support this wick from four of the cords, the top of the wick needs a spreader to maximise the surface area. To encourage the cloth to open to a wide surface, the wick spreader can be made to suspend from a circular ring, or X piece of thick, soft plastic, so that when inflated, the wick cloth will have maximum area and absorb the rays of the sun to maximum effect. The ring or X piece can be made from a tall piece of plastic such that when it is in the inflated still, it has good structural strength, but when deflated, will lie flat and fold easily. The X will have thicker central section to encourage more capillary action, but is likely to puncture due to the X shape with four points. But a tube will enable a very dense water vapour area inside the tube. So a ring is the natural choice, simply because it has no pointy bits to puncture the still when it's packed away. The wick can be pulled into the tube about two thirds or more into the green house section to catch the sun's rays. If a small still, then the wicking action can be further and the wick can reach the top if required after testing the various wicking materials.http://www.btinternet.com/~jhpart/bksolar1.htm (14 of 29) [2008-03-25 22:34:32]


The loose centre of the inner skirt can now be gathered to a circle about half the diameter of the still, and held upwards, the central cords adjusted to hold the skirt angled upwards to encourage safe condensate drainage. Some extra cord between skirt and wick can be used to keep the wick centrally spaced relative to the skirt to minimise contamination and abrasion if this becomes a problem. The bottom of the wick can be loosely gathered to sit in the sea water reservoir. To prevent sloshing of the sea water reservoir, it is recommended to shape an old synthetic bath sponge or some absorbent towelling to make a splash - free sea water reservoir, as this will reduce internal contamination from splashing should you wish to add plenty of internal sea water for better ocean stability. Do not make the base of the wick with too much cloth, or sponge, as the sea water must be able to be replaced easily. For a slightly more sophisticated base, then a small, rigid plastic medicine bottle tuned upside down and be used as the sea water reservoir. The screw cap at the base can be used to replace the sea water by sinking the inflated still into the sea, then opening the cap, swilling about, then sealing after the sea water has changed, without loosing any internal air pressure in the solar still. Again, add some sponge around the top of the sea water level to reduce spillage. An alternative solution is to fit a secondary pipe to orally suck out the old sea water and squirt fresh sea water into the still. Base. The base of the solar still will have certain problems, mainly due to creating stability in the sea. There are two main forms of base. Either the base is fairly flat, so the base floats upright on the sea, with the base of the wick gathered to be a heavy pool in the centre. Or a long, thin tapered design with a small heavy keel weight to allow it to remain upright. To maximise stability, any keel must displace minimal volume, so it sits fairly low and thus stable. The rolling action of a spherical design, or the vertical bobbing action of a taller design, encourages the condensate to move down into the collection area. This section describes the tall, tied base, which has many advantages and enables a much easier to make and more reliable solar still. The tapered base of a commercial design could be made from welding a suitably shaped plastic tube, or with thin plastic tubing then perhaps dual thickness, and welding this to the upper glass house section. This needs a full, strong weld which is airtight but is not recommended nor necessary. For this design, simply gather the plastic together neatly to reduce chances of air escape. Before doing anything else, gather the free end and inflate by mouth, fold and tie, to see where the air leaks are and how the wick and skirt position themselves. It may also be noticed, that as this part is under the water, air is marginally less likely to escape, but it still remain under pressure to inflate the green house section, so all care must be taken to minimise air loss. One or two pipes will also need to be inserted here. Pipes and tether. The pipes are vinyl and available in many small diameters from pet tropical fish shops, brewer shops, and model shops who use them for fuel lines). Do not use soft, or thin walled tubes which can be constricted easily. The smallest brewers tubing allows vacuum and pressure with thicker wall thickness and is the type recommended.http://www.btinternet.com/~jhpart/bksolar1.htm (15 of 29) [2008-03-25 22:34:32]


The pipes and the tether are the last items added before sealing the base of the still. Two pipes may be used, one to insert and replace sea water to the central reservoir. The other pipe to inflate and drain off the fresh water. If using a small bottle at the base, then only one pipe is needed. But having two pipes will allow the sea water reservoir to be sucked out and replaced without deflating the cell. As the sea water evaporates, it will become increasingly salty, so regular replacing will be needed. The long length of fresh water pipe is simply draped loosely in the base of the condensate pocket, tied loosely to the central cords of the skirt to hold it in position, then down to exit around the central base seal. This route down through the base is done simply to reduce the problems of making safe seals through the thin sidewalls of the design. As the base is to be a 'stuffed' seal, then this condensate pipe could be inserted between the outer and the skirt folds, to make a shorter and neater condensate pipe run, but only if the bottom seal is perfect. Likewise, the sea water pipe is fitted to simply allow sea water to be inserted by mouth and when it gets too salty, can occasionally be drained to allow new, lower salt content sea water to be replaced around the base of the wick. The pipes are either part of the tether, or if wanting to save weight and space, they are short lengths of plastic pipe with bungs. The sea water replacement pipe is a simple, short distance into the base of the cell, or perhaps a screw cap plastic bottle. It is likely that the condensate will be sucked out far more regularly then the salt water replacement. Therefore the condensate pipe can be much longer, to allow the still to remain alongside as all precious water is sucked out, then the still inflated from the long condensate pipe. The internal ends of the pipes inside the still must be rounded, with no sharp edges, as this can otherwise abrade and eventually damage the plastic still, especially after many weeks on the high seas. Fitting the internal end of the fresh water pipe in a little foam has many advantages. By fitting the pipes through the gathered base, and a gathered and tied top, the survivor has a good chance to repair a solar still while on the high seas. Being able to untie the base and open up the still for repair, such as patch a hole or cut, makes a much more robust design. It is more reliable to repair a puncture from the inside, so the patch is constantly pushed against the hole, rather than constantly pushing against and lifting any external patch. By having most of the potential air leaks below the sea level, will also ensure the air tends to remain inside, and thus stay afloat, even with a reduced inflation air pressure. (This is called developing a 'robust design' - a design which has far more chance of survival and repair after damage.) The pipes will then run outside from the base and if you wish, up to above sea level. For a more compact package, the solar still can have short pipes, where the user simply lifts the very lightweight still out of the sea, clamp the condensate pipe between the fingers, remove the bung then discharge the fresh water directly into the mouth or into storage bag. The pipes can be plugged with simple tapered plastic bungs to seal the air inside and to allow inflation and for condensate removal. Clamps tent to leak and damage the tubes, and folding the pipes over, then clamping simply runs a good pipe. Far better to use simple tapered bungs. By leaving plenty of length, the pipes can be bent over and lashed to keep the air inside, especially if thehttp://www.btinternet.com/~jhpart/bksolar1.htm (16 of 29) [2008-03-25 22:34:32]


builder has forgotten to tie these important bungs to the pipe with a safety cord. Plenty of extra pipe does no harm, especially if clamping off and slowly damaging the end of the pipes. always include two spare bungs, tied to the pipes. To make a bung, use an old piece of toothbrush, secure in t he jaws of an eclectic drill and then file the spinning plastic into a tapered bung, then smooth with fine abrasive cloth such as a scouring pad. Remove, shape and drill a tether hole. Where the solar still floats high in the water, then the condensate pipe can drain from the pocket directly into a small external collection pouch floating outside the still. But this will need careful welding, and is not always a good idea, even though some commercial designs use an external bag. The only time an external collection bag is useful is when the solar still is left alone for many days, perhaps on a desolate island and hung from a tree. But as drinking water is a daily need, then perhaps an external storage bag attached to the solar still is not such a great idea, especially if it can be damaged by flotsam jetsam or creatures. It is always best to regularly harvest and protect all precious water. I consider it far safer to drain off drinking water little and often, so little is wasted. Any excess drinking water should be placed in many separate storage bags, safely in the raft, or no raft, carefully stored inside any clothing. See storage bags, later. If the base of the still is a tied design, then the base will be very neatly gathered and packed with filler such as tacky office putty, lightly filled or 'stuffed' with bathroom sealant or thick grease or lard or whatever is to hand, in the areas where the string is to gather the base and the pipes together. This can also hold the backup tether. The still is now adjusted at the top so it inflates neatly for testing, and the cords gently pulled to make a neat internal design. When all the internals are about right, the wick can be nicely positioned to catch the sun, the base of the wick sits perfectly in the reservoir area, and the skirt is nicely adjusted to allow the wick maximum sunshine while also ensuring the condensate is safely gathered. The top can now be firmly tied to be airtight. If leakage appears here, then by using nylon cords, the plastic and nylon can be lightly melted into a single button seal, using a hot piece of metal. The still is now prepared with salty water and floated in a sink or a pool, and weights added to the base to adjust buoyancy and stability. Waves are introduced to check the stability. Pieces of lead or car wheel balance weights may be taped to the base to give the still a good chance of surviving upright, ready to work. Any weights must be protected so they do not abrade the delicate plastic either in storage or use. Sitting the weight in some foam will add some extra stabilising mass when sea water enters the foam. This can simply be some lightweight foam sponge in a plastic outer cover (with many very small holes to prevent sea creatures from taking up home after many weeks in the sea). A good weight would be a little piece of lead sheet left over from house roofing, protected in thick plastic, wrapped around the base, then tied securely. Lead can be melted and easily poured into flat sheet in a cheap stainless steel cooking plate. Do not be tempted to add a central cord with a polished weight to act as a fishing lure. any fishing must be done separately to protect the still form damage.http://www.btinternet.com/~jhpart/bksolar1.htm (17 of 29) [2008-03-25 22:34:32]


The still is now left out in the sunshine, either in a pool, or simply on the porch, so it can be tested in sunlight. Measure the quantity of fresh water collected in one day in average conditions you expect to be sailing in. Now calculate the number of stills needed to give safe daily water needs, plus 50 percent more, as unseen problems occur and rough seas can spoil the plot. The other stills can be made 'dry', and not tested, but left ready for neat folding and packaging in the grab bag, or liferaft survival kit, along with the other kit including water storage bags. The first solar still is 'wet' and therefore likely to suffer contamination and cause illness from leaving contaminated water in the still for many years in a liferaft support package, so any 'wet' still should only be used for development purposes. Once the design is deemed suitable, it can then be copied as many times as needed. See also, packaging. The tether must be strong. This is best made by making a strong nylon or (floating orange polypropylene) cord around the strongest part of the still. The tether must ensure the still remains upright, and as such, I prefer a dual top and bottom Y line tether to ensure the still remains upright, even if very windy. Attaching a waist line with pliable but strong gaffer tape can help protect any delicate base to top areas from external damage and can be done at the waterline to reduce damage from floating objects. Part of the tether will need an emergency sea anchor (like a parachute) so that it can be caught before floating away too far. Flat Base solar still designs. If the solar still is essentially a large inflated welded plastic balloon then the construction is different. This may well use the two car wheel rims as the basis of the design. The base sheet can be tougher materials, such as old plastic bivouac bags, with the upper glass house area made from less strong, clear plastic sheet. It is obvious that because the middle is being welded, then this opportunity is ideal for inserting a third, intermediate layer to act as the internal skirt to collect the fresh water condensate. Unfortunately, this skirt will need to be lifted up to retain the condensate, and as such, will need internal tethers. So the internal structure of the design will have to be built carefully before final welding of the circumferential seam. It will also be noted that using a flat dons sheet for the glasshouse will not give much of a glass hose, so this should ideally be made from a tubular or as a conical plastic sheet, made prior to assembly to give a much taller greenhouse area. The skirt can be cut with a star like central opening, with the fingers of the star spot welded or tied to the upper section. Inside the base will also need to be a storage section for the sea water reservoir, which can be a pre made plastic cup, with a foam sponge to maintain its shape. The wick will also need to be supported internally, perhaps using a large, shaped sponge (although they are not always guaranteed to retain to their shape after five years in storage. Therefore the wick will need to be supported to the top. As can be seen, the top can be just as easily made using a tubular section, and tied to hold the sting forhttp://www.btinternet.com/~jhpart/bksolar1.htm (18 of 29) [2008-03-25 22:34:32]


the wick and skirt as in the design described earlier. The base will also need the pipes to enter to drain the liquids which will need a strong welded secondary patch for the pipes to pass through then glued using silicone sealant or vinyl weld glue. Below the rounded base of the inflated ball will need to be external keel consisting of a spot welded lower section containing a sponge and weights. The sponge will absorb sea water mass and help damp the rocking, while the lead will help hold the still upright. The flat base if done well, is a good design, especially if the thicker base remains fairly flat, and the clear area is much larger in surface area. But careful design is needed and there are many weak spots to the design and it cannot be easily repaired. If used, then it can also be less stable in the sea, but is the most common type used commercially today, possibly due to mass production requirements. Testing. Inflate the solar still and sit it in a bucket or bowl of water if you don't have a pool. Squirt salt water into the wick area. Check how well the design sits in the water and encourage some waves. Decide how you can modify the design so it can float better. Note how well the salt water wicks into the upper wick area. Allow time for the still to work. Note the ways that any waves help or dissuade the condensate to run down the plastic into the collection area. Measure the amount of distillate per hour. Change the salt water a few times each day. Play around with different volumes of salt water for stability. See how the tether cord can be used to maintain an upright position, by gently pushing against the area of maximum air pressure, which will be about the lower mid point of the greenhouse area. Perhaps the main tether can be around the base, with a soft, lightweight stabilising tether up to the top to keep it upright when floating downwind of the liferaft. If the central salt water reservoir tends to slop about, then rebuild with a secure a piece of sponge or towelling around the base of the wick to prevent spillage in rough seas. If the condensate slops about, then add some sponge or towelling or polypropylene string as needed to prevent sloshing. If the top of the wick does not get wet, then consider experimenting with better wicking materials, or thread some capillary tubing into the fabric of the wick. Capillary tubing is possible by removing some of the copper cores of fine electrical wiring, but check the capillary tubing can transport the salt water high enough to be of use before inserting. You may now appreciate the advantage of simply tying the base and top to make a simple seal, as it allows constant modification until the design works as best as is possible. I rebuilt my internals three times before I was happy, and the top opening worked rather well prior to reaching the final design. I even put a spike into the still to see how easy it was to repair. I used gaffer tape on the outside, but his gradually peeled off, so was inserted on the inside, which worked much better. For the first few attempts it is highly recommended to fully test the design to destruction by inflating



until the still splits or otherwise breaks, to see where the weak areas are in the welding, materials, design or manufacture. Packaging. If the solar still works reasonably well, the subsequent 'dry' items must then be packed with great care. The art of packaging must be self protecting, or have a protection cover. Fold the still such that the inflatable components will never become damaged nor have any stress placed on the welded joins. The central wick spreader should be carefully positioned to prevent abrasion. Check any folds around welded areas, so the welded seams are not sharply folded to ensure gentle folds which are less prone to damage. The pipes can be folded around the outer part of the main folded package, as these are less easily damaged. Make sure it can be easily inflated and put into use. Put a bright yellow label 'blow here' on the condensate bung and 'insert salt water' on the other tube, Then cover it with a protective layer such as cardboard. The still is now placed in a strong plastic bag, along with many sealable plastic water storage bags, as commonly used for sandwiches. These between the still and cardboard will also help protect the still. A laminated instruction sheet can also be added to protect the still. Date the outside of the packaging with the contents and date of manufacture. as they are easy to make, then replace them every five years and mark a replace by date. Bright orange survival bags make thick, easily welded packaging, marked with a black permanent felt tip marker. Include waterproof instructions, or they can be printed out and covered in food cling film then tied to the tether. If you have a laminator then this is particularly effective. It is common to glue the laminated instruction on the outside of the package, so the owner can read and understand before needing the still. You may wish to weld the seam of the main cover to make it sea proof. Place the individually packaged stills in with the life raft or other safety equipment as required, to make enough drinking water for each person. The packed stills must be secured to the liferaft with a tether or packed in a secure pocket or a tethered survival container. By placing the stills in three different places, should the life raft kit be smashed, this is likely to only damage one third of the solar stills. Water storage. When a solar still is needed, all water must be carefully stored for the drier days, as solar stills do not give great outputs of water. There may be days of bad weather and other days with rain, so all forms of water must be conserved as part of the overall survival strategy including rescue, fishing, physical and mental health. Rain must be gathered, often during bad weather when a solar still must be carefully retained in some form of protective container from the ravages of a storm. A large sheet of plastic can also be used as an upside down umbrella to catch as much rain as is possible and store it all. In really wet weather, the solar still should always be used to catch and store any excess fresh water. Rinse out the salt water and fill it with rain. Adding three dozen plastic ordinary storage bags, the sort for sandwiches using zip style seals, can store the fresh water. If you can collect other sealable plastic drink bags, then these should be rinsed withhttp://www.btinternet.com/~jhpart/bksolar1.htm (20 of 29) [2008-03-25 22:34:32]


distilled water, dried, and added to the survival kit. If they cannot be fully dried, then they can be rinsed with water to which a water purifying tablet has been added, so the insides will be safe for many years. As fresh water floats, add a trailing tether of orange polypropylene cord to the stronger bags so they can be more easily rescued if lost during a capsize or if using only a lifejacket. Without water, you may last four days. With water, up to two weeks. With food and water - indefinitely. So make sure you include the other stuff - fishing hooks etc. See survival kits monograph. There are a few ways to improve a solar still. The central wick should absorb as much solar radiation as possible so splay it out to grab as much sun as possible and to offer maximum evaporation area. The condensate collecting on the wall should be removed as soon as possible, so bobbing around in the sea, or hanging from a tree in the breeze, or tapping with a stick in still desert air or on a mill pond, all helps keep the suns rays reaching the wick and also maximises the coolness of the condensing surface. The main problem area is the central sea water reservoir and keeping all the wick wet. As the height is a problem for wicking then a short still will be more efficient per unit size. Making the central wicking zone and reservoir may be an area of concern. For maximum size from a small package, a long, circular still, with a long, flat central wick, the whole still floating like a sausage can be better if it can be constantly oriented towards the sun. Non - inflated solar stills may take up more room when packed, but they can survive more damage and often allow an upper reservoir for constant wetting of the wick with easier filling with salt water. Whatever you decide to create, always try to maximise the potential of your solar still, by thinking carefully before building. An extra hour of thought in a survival situation will often pay off with greater drinking water generation. Because solar stills produce only small amounts of drinking water, then you must think on an industrial scale, and also look to all other options for drinking water.

Variations on the theme.A strong variation may be to find a suitable large inflatable beach ball made of clear plastic, with good manufacture and shape. Unfortunately, like a ship in a bottle, all the other bits will require some minimalist opening at one small area, and this is the weak point in an otherwise perfect plot. If they are cheap, then three can be used to make two good ones, by cutting a small flap and using an internal patch of plastic from the spare ball and using Vinyl glue to make the repair and modifications after the internals and pipes have been added. There is probably no limit to how large a solar still can be, but putting all your eggs in one basket ishttp://www.btinternet.com/~jhpart/bksolar1.htm (21 of 29) [2008-03-25 22:34:32]


dangerous. Nevertheless, if having a long plastic tube, some string, a length of pipe or a straw and a black sock as the starting point of a survival kit, then a solar still is always possible. If making stills for multi person life raft, or for use on land, then larger stills may be included as part of the wider safety measures for larger numbers of survivors. If calm, sunny day, then a very large polythene tube with a keel, and a large central wick sheet may be able to supply enough water for the worse days too. Something along the size of a 'poly tunnel', found growing tomatoes in a vegetable garden will not take up much room for its ability, but will always be prone to just one puncture. A larger still should consider more closely how it works and probably become more efficient. The sun in most ocean climes is high above the horizon at midday, and so the solar rays will be at maximum power. If the solar still can absorb them in both vertical and especially horizontally, especially at midday, when maximum evaporation power is available. The cooler condensation areas should ideally be vertical to reduce the amount of radiation falling upon them so they stay relatively cool. Because a still is light weight, then there is no reason why it cannot be perched on the roof of a liferaft, or on a floating door, especially if there is a lot of sharp debris floating nearby. Ideally in equatorial climes, a long, fat rounded still with a horizontal wick is useful. Whereas in other climes and during the morning and evening, a general purpose still may be better. Therefore any equatorial use solar still can be a sausage design, with a large dark wick at the base to catch maximum overhead radiation, and turned to face the sun before dawn and dusk. (If travelling nearer the poles, hope for a nice blue iceberg which you can float nearby inside a large bin bag, and use a sponge or a pipe to suck out the fresh water contents as it melts into the solar still to act as a water container.) To make an equatorial solar still which could be shaped as a large and short oblate spheroid, then the central cords from the top and bottom joins, as described earlier, will need to be stronger to pull the shape flatter. The wick will also be shaped differently, more of a mushroom design laid out below a narrower distillate catchment skirt and encouraged to roll to cause the condensate to flow efficiently, rather than bob vertically. The flat base of the large inflatable design may have a large thick base sheet, welded or sewn to a clear upper section tube, and therefore assembled from the bottom up. The pipes can be passed through the circuferential side seam if the seam is not fully 360 degree welded, but have two extending tongues which allow the pipes to enter and then tied to seal them along the tongues. The two pipes could also become the tether. Because of the size, perhaps about three feet in diameter or more, strong polythene is needed, although there are stronger plastics, but they are not easily available, so keep your eyes open. It may be convenient to have a compact design at home, but in a survival situation, a bigger solar still is to be cherished. The base of a flat design can be from rubberised fabric, to survive the sea better and offer a stabilising



weight. Gluing a central pool for the salt water for the base of the wick will also be much easier to make and glue in position if using rubberised fabric, which can be glued and sewn for an airtight seal. the upper plastic will have to be seamed, glued and sewn in place. The top of any large diameter design will need fairly vertical walls, so the top of the clear upper section should be gathered to make a suitably pointed apex to encourage good condensate flow down the inside of the walls. This gathered apex could also make the access area for repair. As making a stronger design is considered, then welding will not be not so easy and sewing with a rubber glue interface as air sealant can be considered. The upper plastic will need to have a multiple layer seam to prevent ripping and careful sewing tension is also needed. Welding is possible, but this will have to use a strong plastic as the base, such as used for lining river beds or ornamental garden ponds and available from most gardening shops. Very thick plastic sheet can be locally heated and pulled into a tapered extrusion to allow the pipes to enter and secured by tying around the locally deformed area of plastic. Non inflatable stills. A thin piano wire solar still. If you look in some cheap shops, you will find a clothes basket which consists of fine wire loops and fine netting which folds into a compact, flat circular package. This immediately removes the many and worrying restrictions of an inflatable design. The rectangular cross section allows it to float using a natural keel section or barge base. An outer shell of plastic and the netting becomes the fresh water collection area, while a separate, suspended salt water tray and vertically hung wick cloth can supply a very large moisture delivery system, especially if you can add a nice big, sun catching wick with an upper sea water hole to constantly wet the top of a large central wick using a damp sea water zone in the top where sea water is poured to drain into the wick. there is no problem with inflation, so a gentle leak of se water in the top to the wick, is simple technology. The whole base can be a condensate collection area if the wick is carefully designed. A survival Land still: If using on land, then you can maximise the whole bag as a long still, and use or make a simple saucer or pan or turtle or sea shell of salt water in the base, with a frame to splay the wick, then simply inflate and tie to seal. Later, simply open and drain off the condensate that pools around the lowest part of the base near the tied opening, made by scooping a lower pool area in the ground and placing a stone to catch the condensate. If it does not inflate too well, then simply make up a light bamboo internal frame or place a bush or lightweight branches inside to expand the volume. The internal volume need not be spherical, but a tall flat area facing the sun at midday, with the rear facing a cool breeze to maximise condensate production. Ideally, a clear plastic bag for a solar still is preferred, but it you have nothing else, then a black or other plastic bin bag will suffice, but the heat to the wick will be less and evaporation will be slower, As the black plastic bag absorbs the suns rays rather than wick, then condensation will also be slower. If you need water and there is no other option, then always make the best of a poor selection of materials.



A (fun) beach solar still. (No. JPs4g) Items needed: A large and a small pop bottle, cloth, strands of cloth. If you are a mariner with sea faring kids, bored on the seaside with your bucket and spade, (or a technology teacher looking for a short filler project on water and recycling), then this can be built with minimal tools other than a pocket knife, some cloth and two pop bottles. The basic design is just a standard large clear soda pop bottle with a smaller pop bottle inside to make the distillate skirt, holding a sea water soaked rag wick in the middle. Find a large soda pop bottle then cut it around a full diameter, near the base, so the removed piece can be pushed back in to seal the base. Turn the main bottle upside down so the threaded cap becomes the base. Slit and splay the bottom of a smaller soda pop bottle to make six or eight fingers, turn it upside down so it becomes the salt water reservoir. Sit this in the base of the large bottle. Because the smaller bottle does not sit easily, the slits in the base of the small bottle are split vertically and these are bent back to become support fingers to keep the smaller bottle centrally supported in the larger bottle. Make sure these fingers are pointing downwards, so the condensed water does not run into the salt water reservoir. If you have chewing gum, then this can help keep the base of the smaller bottle from moving about too much. The still is closed by simply dangling the wick into the central bottle and inserting the base of the large bottle (now the top) into the main bottle so it fits snugly, to make a neatly sealed chamber. Thread a loop of cord, stripped from the cloth, through the removed top (was the base) of the upturned bottle and suspend a piece of dark cotton cloth from the cord. This loop of cord also becomes a convenient handle to later pull the cap into position. The cord holding the wick can also pass through the upper sides of the cap and main bottle, so it remains in place, and can also be made into a loop which will allow the whole solar still to be suspended from a tree or side of a raft. If the curved base of the larger bottle, which is to be the sealing cap, is inserted upside down, then this can become a small sea water reservoir, which will allow salt water to trickle down the holes for the cord, to keep the sea water mainly on the wick, and down into the central bottle reservoir, without contaminating the fresh water condensate. This makes refreshing the system much easier. You do not need to fit pipes from drinking straws for filling the central salt water reservoir nor one tohttp://www.btinternet.com/~jhpart/bksolar1.htm (24 of 29) [2008-03-25 22:34:32]


drain off the condensate around the base of the large bottle. - The condensate removal can be done by simply unscrewing the base cap over your mouth. Drip some salt water into the central reservoir, so the wick gets wet and the reservoir partially fills enough to keep the wick wet. Make sure the still sits in the sun, preferably in a mildly cool breeze to help condensation. Place the still on a branch, or in the sand in a safe, upright position and allow the sun to work. Because the base is sealed, then this upturned bottle will float in a moderately stable manner in the open sea if weighted with a rock secured by cord. The small pop bottle I used had a 'pull nipple' cap design with the same thread as the larger bottle. Therefore these were swapped, so the salt water reservoir had a basic cap, while the condensate in the larger chamber could be easily removed by lifting the bottle vertically and placing the pull cap in the mouth for direct drinking. It took twenty minutes to make the first one and ten minutes for subsequent stills, using a Swiss army knife, two bottles and a piece of cloth. Not a great deal of condensate, but better than nothing. I recently hung this still off a back yard wall in the British summer, using a red wick, but only got about an egg cup full per day. With a cooler breeze and a darker wick, plus some hanging in the breeze or bobbing around to encourage the distillate to run down the sides faster, it could probably manage about two egg cups in best possible conditions. This means that a dozen or more will be needed for minimal survival. This is why specially made solar stills are needed to be well designed to maximise the output from any small, emergency still. Solar stills never make a lot of drinking water, but it's better than nothing. If in a desperate survival situation, always make as many solar stills as possible, but also be prepared to use the still to store any rain water which can be captured using a prepared collection array of palm leaves, plastic sheets or whatever is to hand when water laden skies approach. I have refined this extremely simple soda pop bottle design further. A black cotton sock as a wick, with the open end of the sock jammed into the circumference of the lid, the base of the sock knotted to sit in the reservoir, to give a large conical solar area. There is also the advantage that the salt water can be poured in at the top, and because of the inverse conical sock design, the salt water can only filter down to the reservoir. The conical wick design also helps reduce sideways movement on the reservoir for what I consider a nicely conceived and implemented design. At present under test, awaiting some extended sunshine. A solar still for the side of a life raft. Stand alone solar stills at the standard design. Nevertheless, the side of a liferaft often has a large flat surface, one of which could be angled towards the sun and used to generate condensate. The flat design can also be used onshore, but will need to be rotated unless pointing due south in the northern hemisphere, or vice versa, and if near the equator, then switched direction either side of local noon. If on a life raft, where many people will need water, then a large still will be needed. A solar still can be mounted along the sunward side of a rubber raft or even a driftwood raft to give both shade from the sun and to make a solar still. The solar still can be a simple large vertical form, using flat sheets wrappedhttp://www.btinternet.com/~jhpart/bksolar1.htm (25 of 29) [2008-03-25 22:34:32]


over an upper and lower bar, with the large flat sides vertically down to a catchment area. As only one side is presented to the sun, then the rear of the still can be made from white or reflective plastic to further raise the internal temperature by reflection, yet still remain cool enough to condense the water vapour. This will also make maximum use of a limited sheet of clear plastic. The central wick can be a simple flat sheet of cloth, suspended from the top and onto this a small pipe or extra cloth to keep it wetted with sea water. If this drip feed is less than the condensate removal, then there will be no need for any sea water contaminating the lower condensate collection area. If you cannot regulate the cloth, then the base of the cloth can be fixed to a sloping bar which will drain the sea water away from the condensate collection at the base. The basic rectangular frame can be made to match the plastic sheets, with a wide base to keep the wick away from the condensate collection areas. Four strips of wood and some string for the frame, a dark cloth such as a short or lower trousers for the wick, and two sheets of polythene wrapped over the frame. It is perfectly possible to make the upper side panels of an inflatable liferaft to act as a solar still, using a drip feed upper sea water reservoir, and thus maximise the survival potential of these large commercial life rafts. An integrated version may be added to my DIY liferaft designs. See lifejackets monograph. Desert still. For desert use, there must be a source of water, perhaps just damp earth, and if it's not possible to dig down to water. The simplest is a large clear plastic sheet over the damp area, with a cup below the centre, and a stone on the plastic to make the sheet slope down over the cup. A solar still frame can be made from a large clear sheet into a transportable design, so it will work all day as you walk or rest in its shade. (The Romans used to make ice in the desert by leaving open cups of water to the cold sky at night, and covering with insulating straw during the day.) Do not be tempted to recycle your perspiration by wrapping yourself up to your neck in a plastic bag while sleeping during the day to capture your moisture as this can lead to heat build up and death. It may be done at night, as perspiration still continues during the night, but as this is the time for hot land travel then this is most unlikely unless you are injured and cannot travel far. Always keep a close attention to your body heat and allow your body to breathe normally every few hours. You should now be able to make your own solar stills from bits and pieces lying around, to test your skills, and perhaps one day, in an emergency and if desperate, to help save your life. Hope this has been useful. Email [email protected] John Partridge. B.Ed. B.Sc. Unemployed. Gizzajob.



___________________________________________ Make a better world. If we all blindly follow those who think they know better, then, heaven forbid, we may even end up in a world where all cars begin to look alike, and the only options will be the exciting variations of cup holders or other such facile crap. If (when) this happens we will know we are dumbed down ready to become consumer sheep, fit only to graze in malls. Please help make a far better and nicer Britain than the one Thatcher, Blair and Blunkett have forced on us. We can do so much better, we deserve so much better. Always use your vote to prevent big businesses and fat-cat lawyers from screwing with politics to the detriment of our civil liberties and freedoms. Say no to Labour, Blair, illegal wars and ID cards. Say yes to Democracy, Magna Carta and Freedom. This and the other monographs with the fewest replies get dumped to make way for others. So if you liked this monograph, email and offer any advice or things you would like added, so that I can make it more useful to all. Since this was first posted, it has had no relies so will be dumped in 2008. I am also finishing off a monograph on marine engineering including hull design, electrical, propulsion, steering and motor installation, maintenance and repair, plus some radical racing yacht designs and general boatie stuff such as how to repair, balance and pitch your propeller. Now available. Some other companion monographs by the author. A Builders Guide To Survival Knife Design. A Builders Guide To Survival Kit Design. Learn to swim and survival swimming. A Builders Guide to Steam Engines. A Builders Guide to Computer case design and building. A Builders Guide to Computer water-cooling. A tourist guide to Plymouth, Barbican and Hoe. Domestic repair and maintenance. A Builders Guide to Motorcycle Design. A Builders Guide to Composite HPV Cycle Design. Dumped. A Builders Guide to Composite Motorcycle Design. Dumped. A Builders Guide to Trike Design. A Builders Guide To Camper Van Design. Dumped. A Builders Guide To Basic Wind tunnel Design. A Beginners Guide to Motorcycle and Trike Wiring.



A Beginners Guide to Motorcycle Mechanics Basics. Dumped. A Beginners Guide to Motorcycle Mechanics Intermediate. Dumped. A Beginners Guide to Motorcycle Mechanics Advanced. Dumped. Steam engines, learn to swim, and lots of other stuff. Via my website at www.btinternet.com/~jhpart/index.htm Other monographs which could be published include: A lateral look at innovation. From Polynesian monkey traps to BV141. An approach to preventing design stagnation in small businesses. Building the Future: Development possibilities for single track vehicles. Compilation including examples of seven radical machines built and tested on the road. Motorcycle design, its roots and future. A draft thesis of 200,000 words. I'm looking for any university with the relevant qualifications. Ergonomics and control possibilities for single track vehicles. Fundamental corporate design stagnation, and the rise of the car cup holder. Social hurdles leading to the failure to find qualified staff, even though they exist and seek work. A few case histories. Derrified: Hospital deaths by mismanagement including case examples of friends and relatives. Also : How to prepare yourself for your time in hospital. Begging. Begging is the bottom line of this work. Being just one of the many long term unemployed English science graduates with a strong engineering background in nuclear, marine and other spheres, the author would like a job or help funding some of the projects. Most of the vast numbers of 'begging bowl innovators' have ideas, so please help. British venture capital is an oxymoron, a joke comparable with our police and education system. Being British, begging is the bottom line of this work. As just one of the thousands of long term unemployed British science graduates with a strong engineering background being wasted in Britain, the author would like a job. Please consider this monograph a slightly blatant C.V. Thanks, John. Partridge. B.Ed. B.Sc. etc. Unemployed. Gizzajob. _______________________________

Britain for the British. Now and For Ever.Email [email protected]



Website www.btinternet.com/~jhpart/index.htm

Always try to improve society rather than just take from it. Until then, lawyer stuff. Copying, duplication or transmission of this material whole or in part is not permitted without the written permission of the author. The contents of this text are for illustrative purposes only. Do not act on this information. Errors and omissions excepted. Contents subject to change without notice. All material herein is subject to copyright, patent and other intellectual property rights. All rights reserved. All trademarks and suchlike acknowledged. Copyright (C) J.Partridge. 2005.


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