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Simple methods for molding fiberglass and carbon fiberby Honus on June 3, 2007

Table of Contents

intro:   Simple methods for molding fiberglass and carbon fiber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

step 1:   Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

step 2:   Method #1- creating a mold and pulling a positve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

step 3:   Method#2- lost foam molding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

step 4:   Method#3- using an existing item for a mold . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

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http://www.instructables.com/id/Simple-methods-for-molding-fiberglass-and-carbon-f/

intro:  Simple methods for molding fiberglass and carbon fiberHere's a couple of low cost and quick procedures I use to manufacture simple parts using fiberglass and carbon fiber. While it's not the best method for producing partsthat see structural loads (some form of consolidation like vacuum bagging/pressure molding to reduce internal voids should be used for that) or parts that need to havean extremely high finish leveI, I have molded everything from simple car parts to subwoofer enclosures to costuming/theatrical props using these methods.

step 1: MaterialsClear packing tapeBlue foam insulation- available at many home improvement storesLaminating resin- polyester resin and epoxy resin ( I use Bondo polyester resin for fiberglass and West Systems epoxy resin for carbon)AcetonePaint brushes- I use a short bristled brush, sometimes I just cut the bristles down to anywhere between 1/2' to 1" llengthMold release paste wax-available from Aircraft Spruce- http://www.aircraftspruce.comWoven fiberglass cloth and/or chopped strand mat- often called CSMWoven carbon fiber cloth- available from Aircraft Spruce- http://www.aircraftspruce.com3M Super 77 spray glue (optional)Rubber glovesFiltering mask

Please use proper safety equipment when working with resins and fibers. Carbon fibers are extremely sharp when cut and the use of resins and melting of foam canproduce nasty vapors.

http://www.instructables.com/id/Simple-methods-for-molding-fiberglass-and-carbon-f/

step 2: Method #1- creating a mold and pulling a positveI used this method to modify existing bodywork on a friend's Ralt R5 CSR Mazda race car. His new tire/wheel set up was causing the front tires to hit the existingbodywork so he modified it by cutting holes in the fenders and then bolting on some plates with spacers so the front tires would clear when the suspension was fullycompressed. The modifications were pretty ugly and un aerodynamic (not to mention the tires would still rub on occasion) so he asked me to make new fender parts thatcould be grafted onto the existing bodywork so he wouldn't have to buy all new bodywork for the front of his racecar. I made these modifications several years ago so Idon't have photos of the entire sequence so I did drawings to fill in the gaps.

The first thing I did was to figure out how much I wanted to raise the fender line and then cut a template to be used to cut the blue foam. The blue foam is then cut using ahot wire cutter and is placed on top of the existing fender to check the fit.

Next the foam is taped down to the fender using clear packing tape- the tape prevents the polyester resin from melting the foam when applying the fiberglass. I thenmade some vents for the new fender using some wood molding- this is hot glued in place on the taped foam.

The taped foam then gets a coating of mold release wax.

Now the fiberglass cloth is wetted with polyester resin and is applied over the foam. You can use woven fiberglass cloth or chopped strand mat for this. If you use CSMyou have to use polyester resin- the polyester resin melts the styrene binder in the CSM. All epoxy resin will do is make a huge mess.

One trick I do when using woven cloth is I pre cut my cloth and stick it down on my pattern with some 3M Super77 spray cement and then wet the woven cloth out withresin using a short bristled paintbrush. If the cloth (or CSM) has to be applied in sections make sure the sections overlap by at least one inch.

Once the resin has cured you can pull the fiberglass mold from the foam pattern.

To mold a carbon fiber positive from the fiberglass mold you first apply a mold release wax to the fiberglass mold.

Then start wetting out the carbon cloth with resin and laying it inside the fiberglass mold. When wetting out the resin use a short bristled paintbrush and a "stippling"action to make sure the resin has fully penetrated the carbon cloth as is placed in the mold. I tend to use epoxy resin when laminating carbon cloth as it produces a muchstiffer final product.

I usually apply layers of carbon cloth at alternating 45/90 degree positioning. This is because the woven carbon cloth only has stiffness in the direction of its fiberorientation.

Before the resin has fully cured you can trim the excess material around the edges of the mold with scissors- this is much harder to do later.

Once the resin has fully cured the part can be removed from the mold.

After the molding process was finished all I had to do was bond the new carbon sections onto the existing bodywork and blend it in with some filler.

http://www.instructables.com/id/Simple-methods-for-molding-fiberglass-and-carbon-f/

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http://www.instructables.com/id/Simple-methods-for-molding-fiberglass-and-carbon-f/

step 3: Method#2- lost foam moldingI used this method to create an air duct for the oil cooler on a friend's Porsche GT5R racecar. This is a very quick and easy way to mold a hollow component or a part thathas severe undercuts that would not alllow it to be molded in a single piece female mold.

The first step is to cut a pattern from blue insulation foam and wrap it with clear packing tape.

Next, cover the taped pattern with a mold release wax.

Now cover the pattern with woven fiberglass cloth and wet out the resin. Make sure to leave a section uncovered- this is where the foam will be melted.

After the resin has cured, melt out the foam by pouring acetone on the uncovered section (note that in drawing #4 it says kerosene- this is incorrect). Make sure you havea decent sized tray or bucket under your part- this will get messy! As the foam melts you can reach into your hollow part and pull out the packing tape and you are leftwith a hollow molding.

http://www.instructables.com/id/Simple-methods-for-molding-fiberglass-and-carbon-f/

step 4: Method#3- using an existing item for a moldIn this case I wanted to make a hidden subwoofer enclosure for my car by molding a fiberglass tub that sat inside the spare tire so I wouldn't lose any trunk space.

I first started by covering the inside of the spare tire wheel with clear packing tape and giving it a good coat of mold release wax.

Next I cut a large ring from MDF and placed it on top of the spare tire.

Then I started laying up my fiberglass ( I used CSM for this) into the taped spare tire. The fiberglass was applied so that it overlapped the upper surface of the MDF ring.This made the finished molded tub much stronger and made it much easier to remove from the spare tire after molding.

After the resin cured I cut another MDF ring to mount my subwoofer into and joined it to the MDF ring that was molded into the fiberglass tub. I used some sealantbetween the two rings and also screwed them together.

Then I drilled a hole in the hole in the MDF for my subwoofer wiring and applied sealant to it after I ran my wiring to the woofer. The last step was to bolt the subwooferinto place.

The volume of the molded tub turned out to be perfect for a 10" subwoofer and it sounds great without taking up additional trunk space- and I get to keep my spare tire!

http://www.instructables.com/id/Simple-methods-for-molding-fiberglass-and-carbon-f/

http://www.instructables.com/id/Simple-methods-for-molding-fiberglass-and-carbon-f/

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Comments19 comments Add Comment

 skaldedgrifon says:  Aug 17, 2008. 12:33 PM  REPLYThanks for this tutorial. It really helped clarify the process. Great diagrams and support text. I like the real-world examples and the open ended feel where italmost says 'now go build what you have always wanted to with this new knowledge'..... Good stuff.

 Honus says:  Aug 17, 2008. 1:34 PM  REPLYThanks- glad you like it!

 Scurge says:  May 29, 2008. 10:26 PM  REPLYTip from experience:Vacuum bag your carbon fiber (you can do it with fiberglass as well)! it makes it more lightweight by removing excess resin, and it is stronger in the endbecause you get all the air bubbles out. It also looks better in the end and has a smoother finish.The technique is described fully here: http://www.info-central.org/construction_vacuumbagging.shtmlIt makes a big difference in tensile strength, more than I thought till I tried it.all i used for the vacuum bag was one of those space saver closet bags and a shop-vac.

 Honus says:  May 30, 2008. 6:15 AM  REPLYI'm familiar with vacuum bagging- I've had a bagging setup since the early 90's and I used to make a rear wing for a race car. It's great for parts that seelarger structural loads, especially where epoxy resin is used.

 jkinrade says:  Mar 30, 2008. 1:35 PM  REPLYHere's something I've been trying to figure out for a while: When you're making fenders, is there a way to produce a 'mirror' foam mold for the other side, oris it just a matter of eye-balling it? My project bimmer race car needs some bigger wheels.Thanks.

 Honus says:  Mar 30, 2008. 4:07 PM  REPLYHmmm... I don't know. If you had a CNC foam cutter you could probably do it.Check out: http://gm.cnc.free.fr/en/index.html

 shortshift says:  Sep 24, 2007. 2:07 PM  REPLYHey, cool that you posted this up, I like your illustrative sketches a lot, they're clear and simple to understand.

I would encourage you to break these techniques into separate instructable sections just to make them more readily searchable. While they're all relatedthey're also quite useful in and of them selves.

Anyway, I was going to make a lost foam page for a motorcycle tank, but you beat me to it :)

http://www.instructables.com/id/Simple-methods-for-molding-fiberglass-and-carbon-f/

One challenge I've had is coming up with the correct patterns for cutting up glass when laying up around complex shapes. That air duct for instance; whatwere the glass shapes that you chose for the "crotch" section where it bifurcates into two? Seems like this could be a new instructable topic altogether...

Thanks for posting.

 Honus says:  Sep 24, 2007. 6:22 PM  REPLYThanks for the comments! As for figuring out how to cut cloth for complex shapes you can first cover the area with masking tape and then cut that intosections and peel it off your pattern. Then flatten it out to give you some patterns to cut cloth from. It's not perfect but it works reasonably well.

 DanDaDad says:  Aug 31, 2007. 1:18 AM  REPLYGreat stuff!!! You can also get supplies from Wicks aircraft supply in Highland Illinois, about 35 minutes east of St. Louis Missery. Or just order online.http://www.wicksaircraft.com/

 freewheeler says:  Jun 9, 2007. 9:32 AM  REPLYu ar brilliant.keep it up,as i wanna build a carbon MTB and i need all the tips and instructables i can get.

 Honus says:  Jun 9, 2007. 2:43 PM  REPLYThere's more info and pics here:

http://www.sheldonbrown.com/rinard/howibuil.htm

http://www.sheldonbrown.com/rinard/

Hope this helps!

 freewheeler says:  Jun 10, 2007. 1:43 AM  REPLYthanx vry much

 freewheeler says:  Jun 9, 2007. 9:34 AM  REPLYalthough what i really need is a frame jig and where i can get epoxy.and carbon sheets.

 Honus says:  Jun 9, 2007. 2:36 PM  REPLYYou can buy all the materials you need from Aircraft Spruce:http://www.aircraftspruce.com

The jig you'll need to construct yourself to suit your particular frame design.You might want to check this out for a home made carbon frame:http://www.sheldonbrown.com/rinard/carbon_fiber.htm

 mf70 says:  Jun 7, 2007. 9:01 AM  REPLYThis is a wonderful idea, but... KEROSENE? I've never seen any foam product that would dissolve in kerosene.

Mind you, I HAVE melted foam with solvents by accident. The solvents have generally been really "hot" paint additives.

Mark

 Honus says:  Jun 7, 2007. 9:07 PM  REPLYYou're right- I forgot I used acetone when I did this. Don't know what I was thinking.... I'll change it- Thanks!

 trebuchet03 says:  Jun 3, 2007. 11:21 PM  REPLYproducing parts that see structural loads (some form of consolidation like vacuum bagging/pressure molding to reduce internal voids should be used for that)

Vacuum bagging is used when you want to remove lots of resin and reduce weight....

If you want structural members, you'll want to use an autoclave -- a chamber that applies heat and pressure ;)

But that's not to say you can't do both vacuum bagging and curing in an autoclave. You can wet your cloth -- bag it to remove excess. Lay it up -- then curein an autoclave. I've never done it, but a friend explained the entire process -- it's rather intensive :p Works especially well when you use cloth bulkers :)

Also, for the mask... Anything but a organic filter will not protect you. That is, regular dust "comfort masks" won't cut it ;) You'll know quickly as styrene actsfasts and makes fairly stupid for awhile.

If you can get it (a big if), biaxial woven carbon is strong in two axial directions -- rather than one. You can also lay up a layer of Kevlar to give it a springycharacteristic (that is, if it's thin -- you can dent the fairing -- then pop it back out ):)

http://www.instructables.com/id/Simple-methods-for-molding-fiberglass-and-carbon-f/

To be thorough... I did a series on making an HPV fairing -- making a negative tool and such (I actually need to write one more instructable to finish up theseries :p). While the overall process is not as simple as what you've outlined here (we made a tool) -- it's just another way to get a product :)

 trebuchet03 says:  Jun 3, 2007. 11:24 PM  REPLYDamn, forgot the link

Videos for Making a Fairing

And I forgot to mention -- nice car :D

 Honus says:  Jun 3, 2007. 11:58 PM  REPLYThanks! I guess I should have clarified that point as I have done a fair amount of vacuum bagging in the past. My point was that unless you dosomething to consolidate your wet layup you can have internal voids which can lead to structural failure. Vacuum bagging also improves the wettingout of the fibers.

A great many carbon composite structures have been built without the use of an autoclave (autoclaves are primarily used when using prepregmaterials- I'm not too familiar with people using one for wet lay up) and while they may have been less than structurally "optimal" from an engineeringpoint of view they certainly do exist. Many carbon bicycle frames have been built this way, some using bladder molded lugs bonded to filamentwound tubes. Some have also used resin transfer molding (RTM). For optimal tubular structures filament winding is really the way to go on acost/performance basis- you can get very precise fiber orientation and resin volume.

When I worked in the bicycle industry I remember talking to a couple of engineers from Lockheed and the guys at Spyrotech in the early 90's aboutproducing a filament wound composite crankset..... now carbon cranks are pretty commonplace. All the latest pro roadie carbon frames are amazingin their strength/stiffness to weight ratios......

The biggest thing when designing carbon composite structures is to remember that carbon is anisotropic- it's greatest strength is along the directionof fiber orientation.

Vacuum consolidation while using an autoclave is very common in the racecar and aerospace industries but most of those guys are using very highmodulous prepreg material. I think my wife might give me trouble if I tried storing some prepreg in our freezer! I've still got a big roll of Kevlar out inthe garage..... :P

I'll have to check out all the HPV stuff- I've always been really intrigued by them- plus I like going fast! The Ralt belongs to my dentist- it's powered bya Mazda rotary- about 200hp and 1300lbs. The Porsche is a 914/6 that belongs to a longtime friend of mine from the bike business- it's a 2.2 liter-about 230hp and 1700lbs.