Read and Researched. Looking for some help on my project.

General Composites Discussions Composites Talk
#1

I have been reading on this forum and another and also seeing the tutorials and want to see if I understand it all correctly to do my project. I used t0 work for a body shop doing mild body work so im familiar with bondo, fiberglassing, painting, except I have never done anything custom before, but Im all about learning new things to further my hoobie of modifying cars.

I want to make this CSL lip (see pic 1,2) out of fiberglass and have a part of it CF (see pic 2,3) which then I want to mold it into the trunk. This is what Im planning on doing, correct me if im wrong.

I am only going to be making one of these pieces so I will not be needing a mold. My plan is to use polyurethane foam that comes in blocks and shape it then overlay fiberglass on it and then CF.

Im not sure if I should use 2 resin types or one since I could use polyester resin for the fiberglass since its cheaper and then use the Surfboard Resin (not sure what it is exactly) because its clear for the CF or could I just use the polyester for all of it. I want the CF to show up very clear. Please advise here.

Heres the step by step. Feel free to critque or give suggestions.

  1. apply blue tape on the trunk so I wont ruin the paint while shaping the foam incase I mess up.

  2. apply some kind of adhesive to hold the foam blocks down to to trunk. (not sure which kind, ANY SUGGESTIONS?)

  3. apply polyurethane expandable foam in the cracks of the blocks.

  4. shape the foam to spec but just slightly smaller than the original part because 1 layer of fiber glass will be layed on top of it.

  5. THis step im not sure which way to go (SOME HELP HERE). Once the lip is formed, is there supposed to be a filler or primer that is supposed to go on the foam prior laying the 1st layer of fiberglass down or could I just lay the fiberglass directly on the foam with resin. Wouldnt the resin go into or melt the foam if I dont fill or primer the foam. Please advise. (Also consider my next step)

  6. Ok so after the first layer of fiberglass is put on, I was planning to put 2 more layers but on the inside of the 1st layer, meaning that I would have to rip out all of the foam somehow and smoothing out the inside and then applying the next 2 layers. Is this a good way to go about it or should I just continue adding the 2 layers on top of the first. Although this way I am scared that the shape will not be exact…

  7. Trim fiberglass just like in pic 1.

  8. Now is when I plan to make the “MILK SHAKE”, part bondo, part resin and resin hardner, to smooth out the fiberglass. Or is there a better way to smooth out the top layer of fiberglass.

  9. After I smooth out the fiberglass, I will then cut a piece of CF and wrap the lip in CF going through the CF routine. Put resin down, wait till tacky, then lay the CF. Then 2 layers of resin and sand with 380 wet then as many more layers of resin as needed and sand, wet sand going finer to finer 2000 grit, and buff to a shinny glass like finish. Although im afraid this might cause air bubbles.

  10. Now if everything turned out ok and is smooth, I plan on taking off the tape and adhering the lip to the trunk and molding it in.

  11. Taping off the CF that I want showing, then painting the thing and clear coating it.

I look forward to everyones help. Thanks.



#2

anybody around?

#3

In my opinion, it would be far, far more simple to make a mold of the part, make a fiberglass copy from the mold, glue it to the trunklid, and then just overlay the whole trunk and lip.

This way you can use standard, proven fabrication techniques and materials, which will be much more straightforward.

#4

I was away for 3x days and I’m back…less money in the pocket as we went to Laughlin!

If you already have a FG rear spoiler, just use that and what Captian Bondo stated, bond it to the deck lid and CF cover it all.

#5

Sorry if you guys misunderstood, but I dont have the fiberglass spoiler. That is just a picture of the fiberglass spoiler that I want to make. If I had had one, I would have made a mold of it and things would have been alot easier but since I dont, I need to shape it out of foam. Hope that clarifies things.

#6

Is there an already a FG one for your car available? Or one that is close to fitting with little modifiying?

If you are planning to use Polyester resin, then get PUR foam as PS foam will melt away with PER.

Surfboard resin is PER that is clear, thinned and has liquid wax in it so you can sand (also called sanding resin) it after drying. The wax seals off the air for the resin to get a full cure. Lamination resin stays a little sticky so you can add more layers of reinforcements and they stay in place so you can wet it out…

#7

yes there is one available but its like $500 and i dont feel that a little fiberglass piece should cost that much, plus I want to try my hand at shaping foam. This would give me a good understanding of my future projects which will be custom as well. Also I will only need one, I have no desire in duplicating it, therefore I dont want to do a mold which could add to the expense.

Yea I understand now that pe will melt the ps foam (blue or pink insulation), but now my question is where can I get the PUR foam in blocks. I know the blue and pink foam is sold at home depot.

Also could this work- If I end up using the pe foam, shape it, and then if I could cover it with latex paint like a barier between the foam and resin. Or could I just put like 3 spray layers of the latex and then put polyester filler on top and smooth down and then only put the one layer of CF down. This way, I would not need to lay fiberglass, although Im not sure if this way will work.

#8

Oh wow… ok… so you want to basically just use the picture of the spoiler as a guideline for making one in “real life”?
Well, the foam isn’t too expensive to you could certainly try it…

Wether or not the project is worthwhile for you will basically depend on what your time is worth to you I guess.

I doubt latex paint is a worthy substrate for an automotive overlay…
that’s something you might use on a plug, but not for something mounted to your car full-time.

I really think if it were me, and buying the spoiler just wasn’t an option, I’d make a plug and mold still.
Using a bunch of layers of different materials as a core and then overlaying it just isn’t going to be dimensionally stable in the long run.

#9

No, I have a friend who has a complete trunk with that lip already molded on. I will take measurements from that. I would be kinda crazy just lookin at pics and trying to make it.

ok I think I found all the answers that I am looking for so far. All thats left is to do it. Thanks for everyones in put. if I get stuck Ill know where to go.

#10

you can buy urethane foam at a home center, It is usually covered in foil and about 5-10X the price of the blue stuff. one trade name is cellotex. it is a urethane foam with fiberglass reinforcement. most composite houses also sell foam sheets and blocks. I would suggest you carve and make the piece using PER and chopped mat. once you have it shaped perfect and bonded on overlay the part you want in CF. cover well beyond what you want to show. once cured go back and feather the edges down, mask, prime, sand and paint, peel the mask and clear the entire lid.

#11

I cant use per foam cause will be using polyester resin which will melt the oer foam unless the method I sugested above with the latex is feasable.

#12

It is PS Polystyrene foam that melts with PER, the PUR (Polyurethane) will not and he is correct, you can get it at like Home Depot. It is the more expensive one with alum foil on it.

You might to also check with www.precisionboard.com to see if they have a dealer near you as they manufacture PUR foam.

You might also check out some local sign shops too…

#13

thanks, sorry i got a little confused with the abreviations. i thought he ment PER as in polystrene foam. PER is the resin. All is well.