Hi,

I am leaning towards fiberglass deck lids for a project I am working on.
I was going to go with aluminum, but the cost of getting them made (I dont do english wheel stuff so I would sub out the skins) is pretty high.

So, I am thinking of making a buck that is the shape I want.
Not going to make a mold/plug. Just make a single piece.
Fill in between all the ribbing of the buck with green foam and sand/carve it to shape.
The wrap the whole deal in saranwrap and lay fiberglass right on top.
Use fiberglass matt with a layer or two of woven cloth.
Then, once I have the final shape and desired thickness here is my question.

I would like to lay carbon fiber, exposed over the top.
I would assume that the first step would be to sand and make perfect the fiberglass lid so its absolutely smooth, no bondo, just resin and glasswork..

Can I just lay carbon fiber over a fiberglass piece?
Do I need to start with a certain type of resin for the fiberglass and then build up with that type of resin?

I would like an exposed carbon fiber piece at the end of the day.

Rich

You're kinda doing it backwards but I guess it would work. Problem would be building up the resin enough on the top of the CF to be able to sand it back down smooth. If the risen is too thin you're going to expose the CF and screw up the look of the mat.

You would do MUCH better talking a stock lid and pulling a mold from it. Than make you final lid from the mold.

That's how I'd do it.

I'd have to agree with Paul. You're doing it backwards that way.

IIRC this site (http://www.fiberlay.com) has a lot of useful info for mold making and glassing.

Edit:

more specifically: http://www.fiberlay.com/howto/silicone.pdf

This pdf is instructions on how to make an open faced RTV silicone mold.

Well, the lids I am doing are not stock shaped...

So, you think I should make molds first?
The other thought I had was to make perfect Fiberglass pieces as I described earlier and then bring them to my sign guy and have him wrap them in vinyl/carbonfiber look stuff....its hard to tell the difference when he does it.
Rich

Add fiberglass, foam, tape, paper, whatever to the stock lids to make it look like what you want. Pull a mold, then lay up your real pieces. You're going to make a mold regardless of what you do. It only depends if it's a positive mold or a negative mold.

If you are going to glass over foam, you must use epoxy resin. Polyester will dissolve the foam.

why not use all carbon fiber

Make your panel from foam as you plan. Make in perfect. Pull a splash mold from your shape. Fix and perfections in the splash mold. good coat of resin in slpash mold before setting in the carbon.

Oh and add lots of itching.

$$$

I'd recommend that you go by Barnes and Noble and get a copy of "Fiberglass & composite materials" by Forbes Aird.

It's a very good read.

Wes

http://www.fiberglasssupply.com/Product_Ca.../pour_foam.html

If you're going to use foam use polyurethane. DO NOT USE insulation foam or anything like it because it will melt under most chemicals, even bondo. If you have a part to pull a mold from just make the part the shape you want and pull the mold from it.

Making a female mold initially will be a pain and your product probably won't turn out the way you would like it to. I would make a male part whenever possible and then make a fiberglass female mold most of the time. Do more research first and do some practice runs on smaller parts.

How about this idea: Buy a decent pair of FG lids and modify them to your liking.

If you would price the current cost of carbon fiber, fiberglass cloth, and resin, you might want to reconsider and simply modify someone's readymade glass lid.

These things have gone up absurdly in the last few months. Even though the price of a barrel of oil has come down significantly, it hasn't shown in the fiberglass industry.

Polyester resin melts styrofoam or any styrene based foam but epoxy resin doesn't. Epoxy resin melts urethane foam. Polyester resin won't melt urethane foam. Aircraft spruce has blocks and sheets of both.
Urethane foam sands nicely, styrofoam doesn't, you must cut it with a hot knife. Aircraft spruce sells hotknife kits, too. You can technically use either resin with any type of cloth, personally I prefer epoxy but it has it's problems too, like the part where it doesn't work with the foam that's easy to shape and if you don't mix it perfectly or if the temperature decreases it won't ever get hard.

Oh yeah, PIZZA tonight, Rich!
Not that Costco industrial stuff either. This was a custom made job.

The only time I have ever touched polyurethane foam directly on epoxy resin was to use the foam as core. Typically if you're making a mold you will want to make it smooth before you put glass/carbon on it. I use bondo and then primer to finish it off. Then I wax it up and lay up on top of it. I haven't ever had any problems with polyurethane foam, but I have melted lots and lots of styrofoam (all on one project I couldn't turn around on). Also if you're not at the very least vacuum bagging the material your parts will be heavier than they need to be and they will not be as strong. If you're trying to get a nice surface finish the vacuum bagging will pull the material down tight into the mold giving a better finish.

http://sae.wsu.edu/media/0708car/body/
A company water jetted this foam out for us without letting us know what they were using beforehand. The foam melted all over. We tried using plaster of paris on it and then used bondo on top of it, but it all came out and it was really crappy. The picture at the bottom is how this thing was after lots and lots of chipping the crap off from the mold. I wish I would have had more time to work on it before we painted it, but it still turned out good enough for a race car.

http://sae.wsu.edu/media/0708car/bbq/
This is of a seat we layed up on the pour foam I talked about above. You have to go through a few pics to find the ones I'm talking about. We shaped it to fit me since I was the biggest person that would be sitting in it. We didn't have time to pull a female mold so the top ended up rougher than I would have liked, but it still worked really well. The top half of the seat didn't pull a vacuum, so it ended up heavier, but still turned out alright.

http://sae.wsu.edu/media/0708car/08-03-10/
Here are some pics of the initial seat mold and a carbon restrictor I made.