Fiberglass, Ghetto Engineering, Excitement

Here are a bunch of pictures from my weekend fixing rust and exploring the virtues of fiberglass. I'm super excited about the glass, btw. The parts came out very well and weren't that hard to make. I'm going to start making molds for fenders, trunks and my custom hood. Thanks to this forum for all the help getting started. Y'all rock.

http://bengarrido.com/2013/10/30/the-art-of-ghetto-engineering/

Is there anything I should do special as far as fenders? I want to make the wheel opening larger and build a dam to divert air around the wheels, but otherwise I want to keep the stock shape. Will I need to impregnate the glass with iron to make it strong enough?

This weekend I'm going to start fiberglass round two. Any tips for making molds of the trunk and hood? I'm not going to bother with hinges, I'll just secure them both with four pins.

You will likely want to brace the mold with wood fiberglassed on.

This. Make some cardboard patterns that sit perpendicular to your mold surface. Cut those shapes out of 2x6s. Sand the 2x6s down to 80 grit and glass over them. Epoxy bonds with wood well, but polyester resin is okay as long as you surround the wood with fiber. If you drill some random holes in the wood with a spade bit (3/4" - 1.5") and lay the fiber through the holes, the fiber will have less of a chance of breaking free from the wood.

In reply to Warren v:

That sounds pretty easy. With this sort of a method, how many layers of matte/resin would you use.

I ask because the air extractors I made last time had three layers and those things are berkeleying stout.

For the molds, it really depends on the shape and how many you plan to produce. 1/2" thick is the general "safe" recommendation for fiberglass tooling, but you could go down to 3/8" without much deformation if you reinforce with wood. Your absolute minimum would be around 1/4". Your general chopped-strand fiberglass mat is 1.5oz/ft², which usually ends up being around 20 layers/inch. If you go heavier, buildup will be faster.

I would highly recommend your first tooling layer be woven cloth, something lightweight that won't print through to the gelcoat layer. Cloth is measured in oz/yd², don't ask my why. 4oz E-Glass works great for this, just cut it into pieces and don't be afraid to overlap, as it wets out easy. Good supplier: http://www.uscomposites.com/cloth.html

Oh, don't lay up more than 2 layers of 1.5oz mat at the beginning. Wait at least an hour for it to cool down, then sand it with 120 grit, clean it off, then lay up the rest of the mold 4 layers at a time. If you do too much and make it too thick, the exothermic reaction will make the mold cure completely at a higher than normal temperature. When it cools back down, it will shrink and deform a measurable amount.

This is a good guide: http://www.fibreglast.com/product/mold-construction

So it this (even more practical): http://www.sceadu.com/support_fiberglass.html

I discovered some things yesterday that changed my priorities vis a vis the Daewoo.

It turns out my stock fenders are really light once you pull out the factory rust promotion salt sponges and sound deadening. I've already made the air extractors for these fenders and, it seems, making glass replacements will be a waste of time.

This leaves me with a hood and trunk. If I were to make a copy directly off the metal (I was going to say stock, but neither the metal hood nor trunk is stock) and skip the mold step, would it cause the end of the world?

DaewooOfDeath wrote: This leaves me with a hood and trunk. If I were to make a copy directly off the metal (I was going to say stock, but neither the metal hood nor trunk is stock) and skip the mold step, would it cause the end of the world?

I've done this many times including the hood and trunk on the Wartburg. The biggest issue is you will need to do a lot of finishing to get a smooth surface.

You'll need to lay up at least 2 layers of 1.5 oz and let it cure completely. Any more than that layed out on top and your part gets thick enough to throw off final dimensions. Once its cured pop it off the original part carfully, brace it to shape before hand if you can then lay up another 2 - 4 layers with some reinforcement on the inside. You will sand off almost a full layer on the outside to get even close to smooth then need to skim coat it with filler to finish it off. It can be done and its still a faster/cheaper way to do one off parts but it can be a pain in the ass.

JThw8 wrote:

DaewooOfDeath wrote: This leaves me with a hood and trunk. If I were to make a copy directly off the metal (I was going to say stock, but neither the metal hood nor trunk is stock) and skip the mold step, would it cause the end of the world?

I've done this many times including the hood and trunk on the Wartburg. The biggest issue is you will need to do a lot of finishing to get a smooth surface. You'll need to lay up at least 2 layers of 1.5 oz and let it cure completely. Any more than that layed out on top and your part gets thick enough to throw off final dimensions. Once its cured pop it off the original part carfully, brace it to shape before hand if you can then lay up another 2 - 4 layers with some reinforcement on the inside. You will sand off almost a full layer on the outside to get even close to smooth then need to skim coat it with filler to finish it off. It can be done and its still a faster/cheaper way to do one off parts but it can be a pain in the ass.

I hate to be contrarian, but that is a very difficult way of doing things. It's much easier doing a female and then a male; much less finishing and overall work. You'll want to paint or spray gelcoat on your plug before laying fiberglass. That will transfer the smooth surface very well. Also, don't pull the mold off the original plug until you're done laying up fiberglass. It will warp like crazy otherwise.

Okay, thanks for the tips.

Warren v wrote:

JThw8 wrote:

DaewooOfDeath wrote: This leaves me with a hood and trunk. If I were to make a copy directly off the metal (I was going to say stock, but neither the metal hood nor trunk is stock) and skip the mold step, would it cause the end of the world?

I've done this many times including the hood and trunk on the Wartburg. The biggest issue is you will need to do a lot of finishing to get a smooth surface. You'll need to lay up at least 2 layers of 1.5 oz and let it cure completely. Any more than that layed out on top and your part gets thick enough to throw off final dimensions. Once its cured pop it off the original part carfully, brace it to shape before hand if you can then lay up another 2 - 4 layers with some reinforcement on the inside. You will sand off almost a full layer on the outside to get even close to smooth then need to skim coat it with filler to finish it off. It can be done and its still a faster/cheaper way to do one off parts but it can be a pain in the ass.

I hate to be contrarian, but that is a very difficult way of doing things. It's much easier doing a female and then a male; much less finishing and overall work. You'll want to paint or spray gelcoat on your plug before laying fiberglass. That will transfer the smooth surface very well. Also, don't pull the mold off the original plug until you're done laying up fiberglass. It will warp like crazy otherwise.

Not disagreeing at all with you. Note I said it was a pain in the ass :) But you can knock out a part faster and cheaper this way if you only need to do a one off and you don't mind sanding (a lot)

The problem with pulling a mold for a one off is now you've got a mold sitting around taking up space. So you either find a way to store it forever in case you need another one, or you trash it and waste a lot of product in the process.

But I absolutely agree you will get a much better finished product and a reproduceable one if you make a mold properly first.