Carbon Fiber/Fiberglass

[Occasionally6]

Originally Posted by redpoint5

I'm pretty good with my hands, but my first attempt with fiberglass was a disaster. I spent about $150 in materials to make a mold of a kitchen sink, and had nothing but problems. Problems with bubbles, problems with getting the glass to conform to the contour of the sink, problems with the epoxy setting up too quickly, problems with the glass wanting to stick to my hands more than the sink, problems getting the PVA to coat uniformly, etc..

With chopped strand mat? Fibreglass cloth is much easier to drape over complex surfaces. Two layers offset at 45 degrees are necessary if you want ~anisotropic properties.

Perhaps it's worth some indication of how much weight is in doors to be saved. On a 1400kg 4-door car I have weighed the empty door shells: 20kg front; 18kg rear.

In terms of safety, a foam filled, double skinned door in composite could be pretty good I think. I'm undecided about the value of a - triangular - tube frame inside the door linking the hinges and door latch.

This is my favourite How To series on making composite panels using a steel panel as the pattern:

http://www.youtube.com/watch?v=UgKvDw1E60E

[serialk11r]

Originally Posted by Occasionally6

Perhaps it's worth some indication of how much weight is in doors to be saved. On a 1400kg 4-door car I have weighed the empty door shells: 20kg front; 18kg rear.

In terms of safety, a foam filled, double skinned door in composite could be pretty good I think. I'm undecided about the value of a - triangular - tube frame inside the door linking the hinges and door latch.

Again though, there are so many other panels on the car that are WAY cheaper and easier than the doors. Once you do the battery, wheels, roof, quarter panels, hood, and trunk in CF, and then racing seats (still better bang for the buck than CF doors, especially if you're going to add foam or other reinforcement), then maybe you can look at the doors.

The carbon doors I've seen are something like 2k each, never seen one under 1k. Let's say you can do all 4 doors for 6k, and somehow your windows and whatever still fit. Now you need to make some custom crash bars most likely, plus maybe some foam so fragments of composite don't stab you if you get hit from the side. You said your doors were 38kg total, so let's say you can drop 25kg from that. That's about 200 dollars per pound.

For 200 dollars per pound savings, there are more things than what I listed above that would be easier to install than a CF door. For example, aluminum brake calipers or aluminum hat rotors. Aluminum suspension arms. Lightly used secondhand coilovers. Titanium exhaust parts (you can drop about 1 pound for 100 dollars from aluminized steel parts).

Don't get me wrong, doors are a really big place to save on, but it's only for the really serious dieter. If you can make your own door for a reasonable cost and amount of time, then sure but I would guess not many people are capable of that.

[Occasionally6]

My reason for quoting the door weights was to point out that there's not huge scope for weight loss in duplicating them in composite. I make no judgement with respect to the value of doing so.

The foam would be the crushable structure. There are foams available for the purpose, with defined crush rate vs pressure and minimal &/or slow rates of spring back.

On race cars the foams are used inside composite boxes attached to a roll cage and in the head supports around open wheeler cockpits.

I think in some cases which foam is used is determined by the ambient temperature on the day, as the temperature affects the foam properties. (Multiple head supports are made and selected from.)

[BobS]

I keep having this question bugging me and maybe you guys can answer it for me. When the carbon fiber matrix breaks down, will we all be breathing in super small stiff needles?

[kafer65]

I got to examine a TDI jetta cup car at VW show that looked just like my '06 at the time. Driver says yeah hop in and take a look around. I grab the door handle and thought I'd yanked the door off its hinge! It was carbon fiber painted red and even had the chrome trim identical to my door. I was totally astonished at how light it felt.

[TexasCotton]

Does anyone have first hand experience with purchasing fiberglass supplys online etc. whats site what you get. I am looking for both cloth,expoxy, roller etc

[NeilBlanchard]

I have been quite happy with US Composites, in Florida.

http://www.uscomposites.com/products.html
Fiberglass Cloth

[turbothrush]

X2 for U.S Composites. Good prices , well packaged , fast ship

[oil pan 4]

I usually buy mine from ebay.

[stiletto2]

I get my epoxy stuff from polymerproducts on ebay... OK so far. I've got a streamliner scooter project I've started (not worked on it a while though) and have done simple flats and curves with CF fabric I got a while back; also bargain priced.... some damaged fabric is why I got it for cheap. Pretty easy to work with actually. No more difficult than FG. Got my manual epoxy pump from:
Michael Engineering & Rook Metering
The pump ratio is adjustable, but I had them set it at 2:1 by volume (2 parts resin - 1 part hardener) as recommended by the epoxy maker. Non waxed paper cups, slim popsicle sticks for stirring and LOTS of disposable nitrile, vinyl or latex gloves are supplies that one will go through most along with newspaper or cardboard to catch drips. Acetone for cleaning tools and drips.

For a half cone section on the top rear of the tail fairing, I made a curved mold using HDPE sheet plastic. Worked great because the epoxy will not stick to it. So no messy release agent was needed except that I polished the mold with PLEXUS plastic spray polish. Flat sections were done on an old glass storm door. Very clean and polished with the PLEXUS polish spray. They came off mirror smooth; they even picked up the tiny etched lettering and logo of the glass manufacturer. Still, when it comes to any painting, the mirror smooth surfaces will need to be deglossed with very fine sand paper so that paint will have something to grip to.

The one thing about using the HDPE was that temperature stability was very important during cure. I once moved the form out into the sunlight to try to help the cure along, and the sunlight heated CF transferred heat to the HDPE which expands faster than the CF when quickly heated. It started pulling itself away from the CF and caused dents and waviness. Whatever temperature it is when the layup is done, the temperature of the mold and layup need to stay there until it sets at least 24 hours. Think I'm going to build an insulated box with a thermostat, small fan and a hair blowdrier as the heat source for stable temperature controlled environment for the cure process.

There are different patterns of fabric weave that will allow the fabric to lay better for some uses. A satin weave will allow some shifting of fibers in the weave and so will conform much better to compound curves than a plain weave would. Search the web for info on using composites. Lots of stuff on youtube that can help.