Large fiberglass molds

There was an article about a purpose built race car using a Honda Z600 based body. The final body was made out of carbon fiber. Does anyone have any pictures or links that would show the structure of a mold that large and shape? There were concave sections that must have required removable sections. How it that done while still leaving a smooth line?
I made a fiberglass seat to fit me exactly back when I raced dirt oval karts. Now that I have given that up, I want to build a chassis car with a particular body. No one makes what I want so hopefully someone here will have some info. Thanks, Mike Grady

I would recommend two sides, a roof, hood and trunk then saaemble the parts.

I have seen a very neat carbon fiber project with alloy bolt rails on each joint gap and fender welt padding the joint everything bolted together very well and the structure was quite stiff.

Mold seams are typically sealed with a wax or other specialized putty to prevent a large line in the finished part.

Winston wrote: Mold seams are typically sealed with a wax or other specialized putty to prevent a large line in the finished part.

Even so there is usually a line left in the glass which has to be sanded down. That Z600 looked very smooth in the pics. I don't believe the raw carbon fiber look would let you sand a line down smooth unless you are going to paint it afterwards which that fellow didn't.

I wonder how he did it

This is a good book: http://www.amazon.com/Competition-Car-Composites-Practical-Haynes/dp/1859606245/ref=pd_bbs_3?ie=UTF8&s=books&qid=1219243029&sr=8-3

and will answer all your questions. I'm about to dig it out and read it again as I get ready to make clamshells and rear fenders for the Locost.

There are other pictures of that car out on the net. Closeup pic of Honda roof If you look closely you will see that some parts of the body are painted black. I would guess they did that to hide the body work required to cover any flaws in the layup.

If you are going to clear coat the carbon fiber you can sand out some flaws. In a way it's like wood, you can hit the carbon when you sand it, and the clear will make it shiny again. If you do a multi piece mold right the parting lines will be very small. The roof for my car, in the picture below, was a five piece mold. The parting lines are in the area where the drip rail would normally be, they are hardly noticeable right out of the mold, and will be invisible after I sand them down,

More pictures of my project here

youngfg, Did you do all the work? Was everything vac bagged?
Thanks, Mike Grady

Yep, I did all the work. All of the CF is vacuum bagged.

Looks nice. What do you use for a mould release agent? What kind of oven are you using? Vacuum pump?

(I'd really like to hear: Wax. Home built from junk yard parts. Busted refridgerator, this being GRM and all, but I'm wishin'.)

I use wax and PVA when I am making a fiberglass mold off a part. Polyester resin makes a good paint remover, that's why I use PVA with polyester resin. I use a teflon release agent when I make CF parts, it's cheaper and easier than wax, and is good up to 450 F. Wax is OK on CF but you have to keep the temperature down. You can't use wax outside in the sun with CF, the black gets too hot. On a summer day the CF out in the sun will get up to 140 F., wax is only good up to around 120F. I glued a part to a multi piece roof mold that way, wasted a months worth of work. No oven is required, I use wet layup. My vacuum pump is a old compressor out of a water fountain.

Link to PTFE Liquid Release. Mold release I have been using the same quart of mold release for several years.

Thanks. Just out of curiosity, how much did the carbon fiber cost for that roof? Did you have an additional layer of glass under it or is it all CF? Would you recommend the polyester resin or epoxy for things like fenders for a newbie composit maker?

I'm considering using some Kevlar cloth for my fenders. They will be painted. I have a set of genuine Lotus 7 Series 2 clamshells (front fenders) that need to be cleaned up. I'm going to use them for my first buck, then cut up what comes out of that for the second buck and make my clamshells from that.

The CF 5.7 oz, 50" wide and is about $32.00 a yard. The roof used about five yards, and half a 4'X8' sheet of honeycomb. A sheet of honeycomb is about $120.00

I make molds out of polyester resin and chopped strand mat. I put down two layers of gel coat, then at least three layers of chopped strand mat.

As for parts it depends on what it is. A hood would be one layer of CF, then the core, and another layer of CF. Around the edges where there isn't any core I usually build them up with three extra layers for a total of five.

For something like Lotus fenders they are too curved for core materials, so you would have around three layers for the main part and more around the edges and where you would mount them.

I only use epoxy for the CF parts. Supposedly polyester resin doesn't like to be vacuum bagged.

Kevlar is a pain to cut. You will have to get special scissors to cut it, and then it's still hard to cut. The Kevlar Scissors you by at composite shops are around $100.00, but I took some Kevlar to Home depot and tried all the shears until I found a set that would cut it. The ones I found cost $12.00, and they work better than the special Kevlar shears I have. Also don't use your Kevlar shears for anything but Kevlar, unless you want to ruin them for Kevlar.

Where can you get the CF?

Thanks,

John

Thanks again. I gotta get back to work on the Locost. I've been working on my bike, spending some quality time with her, plus all the other routine tasks of fleet and home ownership and haven't had time. As soon as I get somewhere near caught up, I'll start putting the Locost together, then when it's sitting on it's own wheels (again, but this time with the body on), I'll start on the fenders. I have a steel trailer fender to use as a buck for the rear. That should be a fairly easy GFRP starter project.

avtcomposites.com US composites

What honeycomb do you use in certain areas and do you ever use foam for a core? Thanks, Mike Grady

Is there anywhere you can go to a basics class.........something hands-on? Thanks, Mike Grady

I use 1/8" thick nomex honeycomb when I can. I have used foam core, 1/8" and 1/2" the foam is cheaper, and you can shape it to fit more complex curves, but it's not as strong.

If you can come to Kentucky I can show you how to do all of the composite stuff. If you read through this thread about my friend Paul's car. He wrote up the process it starts on page six of the above thread. We have come up with some improvements since that was written up in 2005, but it's close enough to get you started.

Wow!

I'm very impressed. I've never been brave enough to try to make fiberglass parts. I've thought about it and read up on it, but never got brave enough to try. Carbon fiber is like a whole level above that.

Oh, you made the wrong suggestion.........where in KY and when?
Thanks, Mike Grady

I'm up for a trip also

I am in Owensboro, we should be able to work something out.

YFG, you should offer that "class" to one of the staff writers and maybe they could do a write up on the XRAwesome

I'd speculate that there was no mold, at least not in the sense most people mean mold. Quite likely a buck with a single layer of fabric draped over it, a drizzle of resin tightly squeegee'd.

Strong it wouldn't be, but it would be light.

Heck, with a single layer of cloth the buck could have been a Honda 600. You lay saran wrap over the car, and then drape the cloth over that. You could vacuum bag it in the end to pull it tight onto the car. Then just flex it to pop it up off the car.

The more I think about it, the more I'm inclined to suspect that's exactly what he did.

EAA offers a composite class. i took it years ago and it was pretty good, but sorta geared toward wing and spar construction.

http://www.sportair.com/workshops/Composite%20Construction.html#TopOfPage