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Quick Question About DIY Fiberglass Fenders


Guest iskone

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Guest iskone

I'm gonna call u.s. composites and get there recomendations about the sort of mold release I should use on the painted hood of my 71'. The hood's paint is not in good shape but the hood is ok.

 

Isk

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Guest iskone

Ok, the guy at us composites told me to use 4 coats of partall then spray on a coat of PVA and use the 700 vinyl ester resin. He alos said I could use 2 layers of tape then wax.

 

I think I'll go with the tape/wax route because I would need a spray gun for the PVA. I think I read somewhere that masking tape will melt with the resin, true? Even with a few layers of wax?

 

Also for the hood I said it would take 4 yards of cloth for both the 4oz and the 7.5oz I belive he said 1 gallon would be enough.

 

Isk

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Guest iskone

I should mention how I came up with that figure for the hood. I measured 62x44(2) which is actually more like 3.5yds and rounded up to 4. That is for the 4oz and 7.5oz

 

 

Isk

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Also, don't be stingy with the hardener. I learned that lesson the hard way, or not so hard way as it took DAYS for some areas to dry completely. And I do plan to stick to the cheap bondo products. My stuborness I guess.

 

If you use enough hardner like instruction said, it will be fine. Extra hardener will actually slow down the curing. If some area takes a long time to cure, that means the epoxy wasn't mixed into even consistency.

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Guest iskone

Change of plans. I get my car back today!!!! So barring any problems I'm focusing on the fuel system and buying new rubber. Which will efectivly tap me out for a while.

 

I'll keep you guys updated as I plan to go through with this project within the month.

 

Isk

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After using a technique like this for my dash, I have the following recomendations:

 

1: Use the duct tape, use the duct tape, use the duct tape. If you apply it evenly, it wont have much if any effect on the outer surface. If you are going to use carbon fiber for the part, then you'll have to use epoxy resin. Epoxy by its nature sticks to almost everything. I used a ton of mold release on my dash after applying several layers of wax as well, and still ended up clawing the foam mold out of it in chunks because it stuck in multiple places. In fact, it stuck just about everywhere except for a small hole in the mold that I covered with duct tape....

 

2: As a general rule of thumb, a layer of carbon is about equal to two layers of glass cloth of the same weight as far as strenght and rigidity is concerned. This only applies if the correct amount of resin is used though, as I found out on my dash. Too much resin will make the part really gummy and flexible. Bad. Also, mixing epoxy resin is kind of a pain, it is very picky about proper ratio and mixing. I'd suggest mixing the two parts in one container, then pouring into another clean container and mixing again before applying it. Having a partially cured part baking in the hot sun in the back of your jeep cherokee for several weeks really sucks, and tends to make said jeep smell like a chemical factory....

 

3: I think someone mentioned this earlier, but it would probably be a good idea to use some duct tape as a mold release agent..... :)

 

Good luck man!

 

Mike

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Guest iskone

Thanks. I'll use duct tape then. I think I'll be outta funds for a while with all that is going on so I won't get to this right away. I plan to use FG and vinyl ester resin.

 

Isk

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Guest JAMIE T

Epoxies are better than poly resins. I use West Systems exclusively. They come in the correct size cans and you buy the "Mini" pumps that fit into each can specifically and each pump meters the precise amount of each component. I buy it from Marine supply places and use it on just about everything. I also use the "aluminum foil" method for lay-ups when using FG. I got the idea from the car audio community for building speaker enclosures that precisely fit the contour of anarea inside the vehicle. It should easily work good for the fenders and hood. You COULD lay-up many layers on your parts and back them up and make a negative mold so you could get good fitting parts over and over again.

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Guest iskone

The guys at US Composites told me to use Poly over Epoxy.

Foil sounds like it may work pretty well. I may try that too.

 

Isk

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  • 2 weeks later...
The guys at US Composites told me to use Poly over Epoxy.

Foil sounds like it may work pretty well. I may try that too.

 

Isk

Probably because Poly tends to flex more before it starts to crack. I'm guessing using less hardener with epoxy will let it be a little more flexable but getting the proper minimum amount of hardener is going to be tricky, would be spending more than a few days to wait for it to cure and probably still be tacky, if not enough.
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You COULD lay-up many layers on your parts and back them up and make a negative mold so you could get good fitting parts over and over again.

I agree with Jamie. If you are going to go through all the trouble, why not make a mold, it's not that hard.

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Guest iskone

I was thinking about that but I just don't know how much time I'll have for the car. I'll be going through the rest of my remodel (put on hold for a while after my arm was snap in peices) taking up ALL of my time. At the moment I'm in a bit of a rush to wrap up the car.

 

Isk

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