Zainab About Rocket

8/8/2019 Zainab About Rocket

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Rocket H2O -Tips For Students In Science Rocket Challenge // Tipberkaitan roket H20

1. Stiff fins are the best fins. Flexibility decreases the effectiveness of a fin.

2. To trace the bottle's shape on the fin material, place the bottle directly under a

light source.

3. Place the grain of the fin perpendicular to the bottle. This will make the finstiffer and stronger.

4. Do not sand the bottle prior to gluing. It will get you disqualified and is notnecessary.

5. Best glues for fins: PL Premium - available at Home Depot or Lowes, Goop -available at most hardware stores, Shoe Gu - available at shoe stores andsporting good stores, 100% GE Silicone Glue - available everywhere. All holdwell, PL Premium is the stiffest, probably the most toxic, Shoe Gu and Goop are

both fairly stiff, GE Silicone is less toxic, but more flexible. Contact Cement orRubber Cement can be used to glue on paper fins. You should be in a well-

ventilated area and wear latex gloves when using PL Premium, Shoe Gu, andGoop. It will usually take fins about 2 hours to cure enough to put on

another fin and about 2 days before launching.

6. "Swing Testing" is a quick way to determine if a rocket has reasonablestability. This test is done by tying a string around the rocket at its CG andswinging the rocket around.

7. Fins cause very little drag and do not weigh very much. A non-stable rocketthat is flying sideways is creating a lot of drag. Non stable rockets have a lot of

problems with pre-deployment of their parachute.

8. The cost of non-vertical flight is tremendous. A flight that is 5 degrees off vertical can loose 10% of its potential altitude.

9. Parachutes are more efficient with more shroud lines. Shroud lines hold theshape of the parachute and keep air from burping from the chute.

10. Parachutes should be as large as possible while still meeting overall lengthrequirements and efficiency standards.

11. Parachute efficiency is improved by using the correct shroud length. Shroud

lengths should be between 1.2 to 1.5 times the parachute diameter.

12. The best parachute material that I have found is dry cleaner bags. If yourequest the bags used by commercial cleaner for drapes or wedding dresses youmay find one large enough for your parachute.

13. The best material for shroud line is nylon upholstery thread.

14. How much water? 1/3 of the capacity of the bottle will get you close. Usesimulator listed on page 4.

15. When humidity is low and there is no chance of rain, you can use talc to keep

the chute from having static cling.

16. The best folding technique for passive deployment is to zig zag fold the cute,

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starting from the top to bottom. When you fold the chute to the shroud lines,gently make a couple of wraps with the lines. You want to use as few wraps aspossible so that the chute will deploy quickly.

17. The parachute should be attached securely to the rocket. It can be glue ortied. If glued, you should reinforce the bond with fiberglass reinforced packing

tape. This also applies to the cord that attaches the cone to the bottle.

18. Deployment at apogee and a quick opening parachute are essential toincreasing hang time.

19. If the rocket arches through apogee and does not slow down, wind drag willnot allow the cone and body to separate even with active deployment.

20. Make sure that your cone sits securely on the rocket. I have seen numerousrockets disqualified due to cones shifting during pressurization or by being blownoff by the wind.

21. The rules no longer allow for a wind block to be used by a competitor toshield the rocket from wind gusts during launch.

22. Beware, bottles expand under pressure. The expansion can upset a cone if

the rocket is not designed to deal with this problem.

23. You can design a cone that fits loosely on the bottle. It will need to besupported by a ring or pegs. Both pegs and rings (butter tub seal) can be gluedto the rocket with PL Premium.

24. Many competitors use poster board paper or banner paper to make theircone.

25. If you use pegs to sit the cone on, make sure to use Bass Wood (not balsa)

and turn the grain so that the G-forces of take off will not cause the cone to cutthrough the peg.

26. Another simple method of controlling expansion and creating a ledge for thecone to sit on is to wrap fiberglass reinforced packing tape around the top of thebottle until it has created a ledge.

27. Practice many times in all conditions including rain.

28. Have a written procedure and follow it every time. The teams I coach follow

step by step through their checklist everytime even though they know it by heart.Airline pilots and surgeons both use checklists, shouldn't you? Laminate yourchecklist!

29. How heavy should my rocket be? That is a good question. The weight thatwould give the rocket the best loft may not allow it to reach the highest altitude.Go for stability first, loft second, altitude third. Try to reach a good compromise.

30. How much air pressure do I use? Easy question, all that is allowed. The morestored energy, the higher you go.

31. Use this flight simulator to determine the best amount of water.

32. Check the opening of your bottle, a standard piece of 1/2 inch, Schedule 40PVC pipe through the nozzle of your rocket. If it will pass through the opening, it

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will launch from any standard launcher.

33. With rocket designs where a tall cone sits loosely on the bottle, the conemass can do little to correct an initial flight stability issue. Why? Because whenthe fins attempt to correct the instability, the rocket can bend in the middlewhere the cone sits on the bottle. If you notice that you are getting a lot of pre-

deployments, you may attempt to move some of your cone mass toward the baseof the cone or you may choose to shorten your cone.

34. Make sure that you have a waterproof box to store your rocket and supplies.

Also make sure you have an umbrella to cover the rocket while staging andbefore launch. Bring rain gear for yourself. The last 2 years at nationals we havehad intense rain and many rockets were damaged.

35. Try not to use paper, cardboard or wood components in the rocket. If you do,attempt to waterproof them.

36. Bring too much clothing. You don’t have to wear it, may want to. When cold

or wet it is hard to concentrate.

37. Know the launcher that will be used at the event you are going to attend. Thisis a particular concern for rockets that have fins that are swept below the flange

on the bottleneck. Many launchers including the typical "Bent Fork Launchers"and the NERDS launcher will not launch rockets with swept fins. If you plan to usea swept fin rocket, I recommend that youcontact the event supervisor or event director to determine what type of launcherwill be used. In the past at nationals a launcher that is capable of launching alltypical rocket fin configurations has been used, but it still doesn’t hurt to check.

38. I recommend a fin jig be used for installing fins with precision. A fin jig is a

necessity when using slow set glues

39. To measure your water, build you own custom measuring device from a 1Liter Bottle. Mark it for just the right amount of water for your rocket. This willhelp eliminate measuring mistakes.

40. Mark your rocket with the correct water level as a double check. If you aregoing to be launching off a launcher where you will have to tip your rocket, ratherthan the launcher tip ping for loading, always put in a little too much water. Asyou tip your rocket you will always lose a little water.

You can lift up on your rocket gently to let out a little water while on the pad.(Don't get too bent out of shape if you don't have exactly the correct amount of

water, a few ml of water will not make that much difference)

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Problem

Create one bottle rocket that will fly straight and remain aloft for a maximumamount of time.

Materials

Two 2-liter bottlesOne small plastic cone (athletic)Duct TapeScissorsStringManila Folder Large Plastic Trash BagMasking Tape or Avery Paper reinforcement labels (you'll need 32/chute.)Hole punch

Procedure

Cut the top and the bottom off of one bottle, so that the center portion or acylinder remains.

Tape the cylinder to another bottle to create a fuselage (a place to store theparachute).

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Get the manila folder; fins will be made from it. Cut three shapes out of thefolded bottom in the shape that the diagram shows. Your fins will betriangular.

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The next drawing indicates how the fin should look once folded.

Mark straight lines on the bottle by putting the bottle in the door frame or aright angle and trace a line on the bottle with a marker. Use these lines asguides to place the fins on the bottles.

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Make three fins and tape them on the rocket. Be sure that the fins are spacedequally around the rocket body. This can be achieved by using a piece of string and wrapping it around the bottle and marking the string where it meetsthe end. Mark the string and lay it flat on a meter-stick or ruler. Find thecircumference of the bottle by measuring the length of the string to the mark.

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Once you know the circumference, then you can divide it by three to find thedistances the fins should be separated.

Use the athletic cone to make your nose cone. Use fairly rigid scissors andcut the bottom square off of the cone. Depending upon your project's masslimitations, place a golf ball sized piece of clay in the tip of the cone. This will

add mass to the cone and give the rocket/cone more inertia. Then, usingscissors, trim the cone to make it symmetrical. (Hint: the diameter of thebottom of the cone should be a little wider than the diameter of a 2-liter bottle.

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Attach the cone with string to the top of the other two-liter bottles so that itlooks like the diagram. Tie a knot in the end of each piece of string to give itmore friction and tape it using a piece of duct tape to the inside of the coneand to the inside of the rocket body.

Many students have trouble with their nosecone getting stuck on the top of therocket and not coming off. This can be prevented by making a pedestal for thecone to sit on. It should be high enough up so that there is space between thecone and the top of the parachute compartment. You can make a pedestal out

of the same material you will make the fins, the manila folder. Make threemini-fins, invert them and tape them on the rocket where the cone should sit.

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Making the Parachute

Don't forget a good parachute has shroud lines that are at least as long as thediameter of the canopy.

Lay your garbage bag out flat. Cut off the closed end. It should look like alarge rectangle and be open at both ends. Lay down the bag on a flat surfaceand smooth it out.

The bag has a long side and a short side and is open at both ends. Fold it intwo so that the short side is half as long as it was originally.

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Make sure the edges are perfectly lined up during each fold. Now fold it in half along the long axis.

Make a triangle with the base of the triangle being the closed end of theprevious fold.

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Now fold it again. Fold the hypotenuse so that it lines up with the right side of the triangle in the above drawing.

Examine the base of the triangle and find the shortest length from the tip tothe base. This is the limiting factor for chute size. The most pointed end willend up being the middle of the canopy.

For an example; if you want the diameter of the chute to be 34 inches then

measure 17 inches from the center of the canopy (the most pointed side of the parachute) along each side, mark it and then cut it.

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Fold the canopy in half, then into quarters, then into eighths. Carefully creasethe folds each time. Crease it well and fold it again. Now the canopy is dividedinto 16ths. Unfold the parachute. Notice the crease marks. Get masking tape

and put a piece around the edge at each fold mark. You may also use Averyreinforcement tabs. Place one on both the inside and outside of every crease,making sure that they are overlaid on top of each other.

Punch holes through every piece of masking tape or Avery tab pairs and usethese to attach the kite-string shroud lines.

As mentioned earlier the minimum length of the shroud line should be thesame length as the diameter of the canopy.

After punching the holes fold the canopy in half. Pick four holes and tie theshroud lines to the holes. After doing this tie the four lines together at the endmost distant from the canopy.

Repeat this four times until the chute is completed.

Once you have it complete attach it inside the fuselage. Generally a couple of

pieces of duct tape will hold the parachute to the rocket. Pack the parachuteloosely and put the nosecone on the rocket.

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You are now ready to launch your rocket.

Carefully read the safety instructions. Fill the rocket half full of water, place onthe launch pad, pressurize, and launch.

Be safe, and have fun!

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Zainab About Rocket

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