Panel Construction Advice - Experts needed

General Composites Discussions Composites Talk
#1

Hello All,

I’ve got a bit of a project on my hands. It’s going to take a while to get to the parts that I want to make for my car and I’m in the accumulation of knowledge phase and hope to pull parts from molds sometime this summer. What I need is some advice on material for building fenders, grill aperture, hood and trunk lid for my 1966 Volvo 122S.

Here’s the car

The grill aperture is a separate part that is multiple pieces of sheet metal.

The hood is very simple with a perimeter frame (probably keeping that) and a Volvo thick steel skin.

The trunk is the same as the hood.

Then here are the fenders.

I have a basic idea of how these parts will layup but what I really want to know is with all the variety of carbon fiber, what should I use? I’ve got a vac pump but have never done any infusion before. I’d like to build strong parts that will last.

I’m appealing to the experience of the forum to provide some advice on the weights and weaves that you’d suggest. All parts will be painted - I’m not doing this for the look of the parts.

Craig

#2

Video’s on this site here for building a carbon hood - http://www.easycomposites.co.uk/Learning.aspx

Some other video’s in this lot that may be of some use to you - http://www.youtube.com/user/WJP004/videos

#3

You could use a thin layer of glass fabric, and behind that a certain number of multiaxial carbon fabrics. These are cheaper than woven 5.7oz, so more bang for the buck.

Also, for car parts, make sure you use a high Tg resin, and postcure before you add paint.

Why do you want composite parts? Weight? Availability?

#4

So you’re suggesting a surface layer of CSM, then carbon fibre after that? Can you point me to a website for the multiaxial fabric? I’m reading several composite books trying to get up to speeed. I’ve got some 280 g straight weave and 2 X 2 twill and a gallon of epoxy (all from aircraft spruce - the epoxy is called “poly epoxy” - found here http://www.aircraftspruce.com/pages/cm/resin/polyepoxy.php)

I bought it as it is supposed to work well for vacuum bagging and appeared to say the right things about structural properties.

Reasons for wanting parts are mostly for design reasons (I need to add subtle fender flairs) rust resistance and some weight savings. This isn’t a race car (though I do track it) - I just don’t like bondo and welding up a lot of seams is an invitation to do all the work again when moisture gets in. To me, these are valid reasons to look at composites. Others would have me beating sheet metal and slatering on the bondo. I also like to push my personal skill set and find a certain degree of pleasure in the obvious masochism of what I’m doing.

#5

Now I understand. Old cars indeed are a strange sort of masochism.

Why not strip the car, have it blasted, then weld all the seams which now are spot welded, and apply a body coat?

Anyhow, not a CSM but a lightweight woven cloth. CSM is not really compatible with epoxy.
Unfortunately I cannot direct you to a supplier, I have no idea who are active in your area.

#6

Even a screen shot would help - so just a straight weave fibreglass first, then the carbon? I can get FG cloth easily enough. What are the advantages to doing this? I was going to import some of the epoxy compatible gel coat from Easy Composites in the UK - so that the surface can be simply wet sanded, primed and painted.

My main concern is that the hood has NO backing structure at all. Just a perimeter frame - so the panel has to hold it’s shape all on it’s own so it needs to be stronger than a single layer of CF.

#7

Plain weave or twill. Twill is easier for the shape you are making. Something lightweight. Just as a sanding layer.

I would not even bother with an epoxy compatible polyester gelcoat, if you are painting anyhow. Waste of money, time and weight. If you like to use something, use a true epoxy gelcoat, which can be applied very thin, gives the part a base colour, and is easy to work with.

Or just blast a sanding primer over the bare part.