Fiberglass 101 - Tutorial

[Carbon Fibre]

I am a fellow "fiberglass technician". Any questions I will attempt to answer. Be specific!

[the russian]

Originally Posted by Carbon Fibre

I am a fellow "fiberglass technician". Any questions I will attempt to answer. Be specific!

I got a question for you. I'm new to this whole fiberglass thing so please be patient with me... anyway i'm currently trying to make a custom light housing and face for some BMW euro-projection headlights. now my question is when i make the mold for the housing do i have to concider how thick the fiberglass is going to be? thanks.

[mike@af]

Originally Posted by the russian

I got a question for you. I'm new to this whole fiberglass thing so please be patient with me... anyway i'm currently trying to make a custom light housing and face for some BMW euro-projection headlights. now my question is when i make the mold for the housing do i have to concider how thick the fiberglass is going to be? thanks.

Wow, that is a good question. TSC? CF? You guys have this one.

[TheSilentChamber]

Originally Posted by the russian

I got a question for you. I'm new to this whole fiberglass thing so please be patient with me... anyway i'm currently trying to make a custom light housing and face for some BMW euro-projection headlights. now my question is when i make the mold for the housing do i have to concider how thick the fiberglass is going to be? thanks.

You allways have to take into consideration the thickness of any materials you work with. When you refer to mold, what exactly do you mean? Mold is a common term that alot of people use in referencing composites, but its rarely used in the right way.

[the russian]

what i mean is the foam mock up of the housing, i'm going to use the covers that cover openings to access the bulbs from the original BMW headlights, so i need to make the mock up have basically the samething incorerated in it. I just need to know if i have to make the mock up just a little smaller than the finial product, or if i make it the real size will it work anyway...
I know.... a bit of a stupid question, but like i said i'm new to this whole fiberglass thing....

[TheSilentChamber]

In general if your using foam as a base you will want to make it smaller than the final product.

[the russian]

sweet... thanks for the info. one last thing what is the average thickness of fiberglass. i know it depends on the amount of layers used, i was thinking 12oz layered twice, does that sound right for a light housing?? do i need more or a different weight of cloth??

[TheSilentChamber]

Thats not going to be strong enough for anything more than pure cosmetic piece. I'm still not real sure on exactly what your trying to make here, so its hard to say how strong it needs to be.

[Carbon Fibre]

REPLY

Someone asked me about fabrication of a headlight bucket? I can't find your post, but i'll try to help. I made one to replace a crappy rectangle headlight on a Tomos scooter once, and here's how.
I wanted a round one, so I actually used a ballon for the shape. Since the polyester resin would eat through the ballon and pop it before the gelcoat hardened, I spraved PVA (Poly Vynl Acetate) on the ballon as a relese agent. This worked better than wax because it assured me a good thick coat and was quick. I then applied my gelcoat and a layer of fiberglass mat. after lightly scuffing up the glass, I then built it up with heavier glass. If u don't do this u will get print-through of the pattern of the glass due to heat from the curing process.
I deflated the ballon and took it out, and cut the mold down it,s center. Keep in mind the front of the bucket was unnecessary, so i didn't make an entire sphere. O.K., I cut it so I could remove the part from inside of it w/out damaging it later. Be carefull cutting to not chip off gelcoat from it's edge.
The 2 halves i placed on a waxed peice of plate glass, and laid down gelcoat and sucessive layers of glass to form a lip that would mate to the other side. Pull both pieces off the table and put yhen together lip-to-lip and align them. clamp the flanges together when they're flush inside, and drill some holes through the flanges to put bolts through. with bolts in place and both halves waxed, here's your mold
To mahe headlight mounts, make them in the finished part as tabs glassed in from the inside. a nice peice of shiny cardboard waxed up cut into a ring for acess put against the lamp opening will work great. Hot glue will temporarily keep ot there for you and peel off of your gel w/out damagong it.

[TheSilentChamber]

To claim your a "fiberglass technician" your a fucking dumbass. You dont use gelcoat to lay your glass in, "print though" as you call it, is not caused by heat, and the last part about shiny cardboard I'm not even going to coment about.

[Carbon Fibre]

really? What do you use, Dupont basecoat-clearcoat? you are the fucking moron

[Carbon Fibre]

Gelcoat cures anerobically. I'm sure you dom't know what that means, so I'll explain. When you put gelcoat in a mold to make a part, it never fully cures untill you lay up your fiberglass on top of it. The gelcoat hardens when it is no longer exposed to air. THAT IS WHY YOU BED FIBERGLASS IN IT. IT IS CHEMICALLY DESIGNED FOR THIS PURPOSE.

[Carbon Fibre]

Gelcoat cures anerobically. I'm sure you dom't know what that means, so I'll explain. When you put gelcoat in a mold to make a part, it never fully cures untill you lay up your fiberglass on top of it. The gelcoat hardens when it is no longer exposed to air. THAT IS WHY YOU BED FIBERGLASS IN IT. IT IS CHEMICALLY DESIGNED FOR THIS PURPOSE. And if you have ever tried to pit fiberglass in a mold w/out gelcoat, you will realise it is very difficult to remove all the air from your laminate schedule.

[Carbon Fibre]

Print-through is caused by building up too much material derectly on your gelcoat. The reason is that fiberglass produces heat when it cures, and that heat causes the gelcoat to shrink-i.e. print through. And as a moldmaker and custom fabricator, you use anything you can that suits the purpose. and in the case of the "shiny cardboard", anything more would be unnecessary. This thread is for people that wish to gain knowledge, so please know what the hell you are talking about before you try to discredit my help. If you attempt a battle of wits or knowledge with me you WILL lose.
thank you

[Carbon Fibre]

REPLY THE RUSSIAN

I found your original question. If you are going to make a production mold, it should be strong. you will want to use tooling gelcoat (it is harder than regular, and comes in black or oarnge). But first you need to make the shape that you want your part to be, and use this to create a mold from. This is called a plug. Styrene foam is good to use, because it's cheap and easily sanded or cut. Use this to approximate the desired shape, keeping in mind that you need to build it up with something to make the finished surface smooth and non pourus. Bondo works great for this (cheap and easy to work with. some epoxy fillers work better (they're less pourus) but requre specific mix ratios, are harder to sand, and are bad to get the dust on your skin or in your lungs. Bondo works good, you just need to wax it really well before you make your mold from it. Finish the bondo with about 220 grit, and apply a few coats of wax. I like using Johnson's paste wax on bondo because it fills in the pores. Apply it, then buff it off using a clean soft rag. I would do 4 coats. PVA works great, too. This plug should exactly resemle the desired shape of the part.
You need to build up the thickness of your mold, so after you have applied a good thik layer of tooling gel to the waxed plug, and the gelcoat has cured, put 1 or 2 layers of light mat on it. Use enough resin to leave the surface smooth enough to lay up your next layer. If it looks like the silent chamber's picture, you have used way too much resin, and didn't get the glass to lay down well enough (lol). After the layer of glass is cured, scuff it up a little with 80 grit to allow the next layer a mechanical bond.
Woven roving is usually the best to go with on sucessive layers, cause it forms well and it's cheap. you don't want to use it on production parts, though: it ends up being heavy and brittle. Use a bi-directional cloth.
repeat the scuffing and laying of roving untill you get a good thickness (usually 3/8" for a good mold of this type). There you have your mold.
Flanges made in the mold to create a multi- piece mold (to be able to remove the part) are usually put in when fabricating the mold.The heavy type of craft paper that has a shiny surface works good, because it is easy to cut, and can be curved slightly to make the mold pieces fit together more accurately. Position it so that the seam created will allow the part to be pulled out of the mold. Cut it so that it's edge is flush with the plug's surface, and"spot- weld" it in place with hot glue on one side only(the side opposite if the first half you make). Wax the crap out of it, and lay up one half of your mold. Remove the divider, wax the flange of the existing mold half (and the plug again, you've probably wiped some wax off in the process), and build the other mold half, using the existing flange to make the other half. Keep in mind that you need to use putty when laying up fiberglass in a hard corner, or it will create voids. The best way is to make a pie bag that you put catalised putty in, squirt it into the radiuses, and laminate on top of it before it cures, trying not to force the putty out of the corner.
Oh and one last thing. Keep in mind that your mold must have a draft angle to allow the part to come out.
This type of mold should work very well for you, and the opening for the headlamp should allow you acess to make the part inside of it.
You should make your part with 1 layer gelcoat, 1 layer fiberglass mat, and probably 2 layers of an 8-10 oz. cloth. you will be able to tell once you make a part how stiff it should be. You can also reinforce stress or mounting locations with more material in these locations. Have fun and good luck.