Picture of Simple methods for molding fiberglass and carbon fiber
Here'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 parts that 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 have an extremely high finish leveI, I have molded everything from simple car parts to subwoofer enclosures to costuming/theatrical props using these methods.

Step 1: Materials

Clear packing tape
Blue foam insulation- available at many home improvement stores
Laminating resin- polyester resin and epoxy resin ( I use Bondo polyester resin for fiberglass and West Systems epoxy resin for carbon)
Paint brushes- I use a short bristled brush, sometimes I just cut the bristles down to anywhere between 1/2' to 1" llength
Mold release paste wax-available from Aircraft Spruce- http://www.aircraftspruce.com
Woven fiberglass cloth and/or chopped strand mat- often called CSM
Woven carbon fiber cloth- available from Aircraft Spruce- http://www.aircraftspruce.com
3M Super 77 spray glue (optional)
Rubber gloves
Filtering 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 can produce nasty vapors.
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manuel.roales5 months ago

thanks sir for being being generous in sharing your knowledge. such a big help to someone starting a project. THANKS again sir!

brubble5 months ago
I'm thinking about building an inner fairing for my Harley that will house a small stereo, amp and some speakers. Do you think that would be too much weight for either of these methods, or can you suggest another method that will work?
Honus (author)  brubble5 months ago

There's absolutely no reason why it wouldn't work for that.

supinder9 months ago
Do you add the resin to over the fiber glass?
Honus (author)  supinder9 months ago
Yep- you brush it on using a stippling motion in order to make sure the resin has fully impregnated the fiberglass cloth.

This has been quite helpful.

I recently bought an older 4x4 to play with and the wings are prone to rust. Although mine are in reasonable condition they could be better. I was thinking of using the existing wings to create a mold. then use the mold to make some rust free wings for myself and a few friends on the Nissan Terrano forums.

This is really a good tutorial. I was unknown about all these facts. Thanks for sharing the info about fibreglass moulding.
GraphixS62 years ago
This is a great method. However, You're using a lot of fiberglass, about twice as much which I imagine could get pretty expensive quickly (resin).
I like this tutorial, but I have a few questions. Do the edges of the packing tape leave impressions in the fiberglass (like if they are overlapped)? And will the foam hold up to vacuum bagging?
Honus (author)  taylorknight62 years ago
The edges of the packing tape will leave an impression in the mold- any surface imperfection on your pattern will be reproduced in the mold. The foam I used will hold up to vacuum bagging.
Do you answer your private messages and not mind helping people who are just getting started with this?
Honus (author)  USFRobotDesignerME2 years ago
I'm happy to help- just ask! :)
Edgar3 years ago
You gotta love an Instructable that even goes as far as the Author drawing Instructions, to make sure people understand it!
Nice! :D
Honus (author)  Edgar3 years ago
Edgar Honus3 years ago
Edgar3 years ago
Since people keep asking me questions about carbon Fiber, on my Portuguese DIY Blog, I've made a Post, pointing to this Instructable:

ydeardorff3 years ago
Any instructable about how to make reversed identical body parts like fenders etc?

That would help me immensely. i have half a car done, and need to replicate the work on the other side.
Honus (author)  ydeardorff3 years ago
The best way to do that would be to design your body parts using a computer and then create templates to make your molds.
The parts are already made on one side. So my only option i guess would be building a home made 3D laser scanner, and then make a 3 axis CNC big enough to carve the parts in layered format.
Again, very expensive, and time consuming. i was hoping for a more ghetto, but works idea.

808Dave3 years ago
Honus - still checking in after all these years?

Re: lost foam method:

A year or so ago, I suspected this might be a great method to make an irregularly-shaped diesel tank to add to my truck's crowded underbed spaces, so I poked around on the web for info to confirm that the sludge/goo that would result from melting the styrofoam with acetone wouldn't be a problem (thinking it would stick to insides of tank, leave a residue, etc.) I didn't stumble across your instructable then - but a major web-retailer of resin/materials said it /would/ be a problem, and advised me not to do it. Your experience makes me think that might have been bad advice.

Would you say I should plan to do hand-cleaning of the interior surfaces after the initial melting - so I'd need to have good access to all interior spaces in the tank for this? If there's residue, does it seem like it's going to be forever sticky (and maybe get mixed into fuel or cause other problems), or is this a non-issue?

Also - you mentioned something about epoxy/CSM turning into a big mess? My occasional experience with almost nothing but epoxy resin in the last ten or so years is that there isn't really a problem wetting out CSM fibers, and I'd definitely prefer to work with CSM in a project like this tank, since it conforms better to irregular surfaces. Maybe this has changed since you wrote this a few years back - styrenes in polyester resin being recognized as rather nasty toxins, etc. and I hear all but replaced with epoxy in many industrial applications. I do recall how magically the fibers used to melt invisibly into the polyester resin when I used it before (doesn't do quite that with epoxy) but I've not observed any alarming lack of strength in my dabblings. Do you still avoid epoxy/CSM combination?
Honus (author)  808Dave3 years ago
I wouldn't use a fiberglass container as a fuel tank. Any type of fuel will act as a solvent so that would be bad. Commercial composite fuel cells have an internal bladder.You would be better off creating a steel or aluminum tank.

I still avoid using epoxy with CSM since the CSM uses styrene as a binder and epoxy resin will not dissolve the binder. The only time I really use CSM these days is for making some molds using polyester resin, and even then not that often. I much prefer using epoxy resin.
808Dave Honus3 years ago
I might not use epoxy for a more volatile fuel, but with diesel, I have no qualms. Also, I plan to slosh the finished tank with a sealer, so it's not a problem, really.

Anyway, repeating my question about the 'lost styrofoam' process: Would you say I should plan to do hand-cleaning of the interior surfaces after the initial melting - so I'd need to have good access to all interior spaces in the tank for this? If there's residue, does it seem like it's going to be forever sticky (and maybe get mixed into fuel or cause other problems), or is this a non-issue?
as someone who has melted styrofoam before as long as you melt and clear within the same day it won't be a problem.
day 1- slippery goo similar do a runny egg(pulverize styrofoam for best results)
day 2- still slippery has a bit more body
day 3- starting to harden but still shapeable
day 4- becomes even more hard but small holes are a problem
day 5- if you get rid of the smell of gas from styrofoam makes a interesting ball once formed
Honus (author)  808Dave3 years ago
Boy, I don't know. A lot of it is going to depend on how well you tape the foam pattern. If you do a good job taping it and then waxing you shouldn't have much clean up. I'd say you would definitely want to have really good access to get rid of any residue.

Have you run a test do determine the impact resistance of the fiberglass tank relative to a steel or aluminum tank?
crowd94 years ago
I imagine the final product has to resist compression/suction from air forces, and not vibrate/flap during a race. How many layers of CF did you use for the parts on this project to ensure strength?
Honus (author)  crowd94 years ago
It was so many years ago I honestly don't remember but it was several layers.
nixnope4 years ago
Nice info! Will need to try this!
ferrous5 years ago
ahahahah! brilliant!
Woow! Nice idea, Boss...
I like the subwoofer idea! Will try to build one for my car too...
stevo675 years ago
Honus you are a huge inspiration, I love those sketches, and thank you for your most helpful and detailed instructional. I am going to hook in and make my own panels for my circuit car. Cheers from Down Under.
Honus (author)  stevo675 years ago
Thanks! Make sure to post pics when you're done!
Bergzee245 years ago
You mention using clear packing tape to seal. Is there a reason why you use clear over the brown packing tape?
Honus (author)  Bergzee245 years ago
I use clear because it's non absorbent. Brown packing tape would soak up resin and it's also not as flexible.
mrlunna135 years ago
YOU ARE A TRUE MASTER CRAFTSMAN!! Wow it is the best and most descriptive instructable. I was just going through the "fiberglass" ibles, and saw yours. Couldn't stop reading, I now have to wait till tomorrow to start my cowl induction hood on my truck and center console. 
Thank you so very much!!
Mr. Lunna Xiii

Honus (author)  mrlunna135 years ago
Wow- thanks! If you have any questions during your build just let me know and I'll help out as best as I can.
dk-info5 years ago
 Just came across this instructable, looks great, I am trying it this weekend. What did you do with the Acetone/foam sludge? Soap and water cleanup?.

amcayanan5 years ago

ferrous5 years ago
I was taught to coat the foam with thinned down white-glue as a sealant, then heat-wax as a mold release... do you think the packing tape method is superior? if so, why?
Honus (author)  ferrous5 years ago
It doesn't really matter as long as it's sealed.
ferrous5 years ago
Thanks for the tutorial! Its nice to finally see this job laid out so logically and nicely.
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