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Forearm of Steel
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Discussion Starter · #1 ·
I've read through the threads here about making custom tails for our fighters, and I'm about ready to begin my journey - here's to my fiberglass cherry about to pop :beer:

This is the tail section in question:



I've got a few questions:

1. If I mask the subframe off, fill the parts with spray foam, shape it to how I like, then mask off the foam, am I ready to lay down fiberglass layers?

2. What's the best process to lay down fiberglass? I need a basic lesson in fiberglass I guess, as much info as you can type.

3. Are there any good online retailers? I've seen a few but I don't know if the prices are good since I'm just getting into this.

4. I know there are different weights of matts - Which is best to use where?

5. What materials would give me the best results? Resins, fillers, matts, etc.

If it helps, this will just be a tail section with no structural purpose - it will only be holding up a tail light, license plate, and covering up the subframe.

Thanks for the advice guys.
 

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You can lay up over spray foam with fiberglass directly. If you use something like floral foam you would need to cover it with tinfoil to keep the resin from eating away the foam. I like to use floral foam and glue the blocks together for shaping since it is alot easier to shape than spray foam, but it does damage easily if you bump it with something or sand too much off.

I don't know what to tell you about laying glass you just try to get the glass to soak up enough resin to become saturated, but you don't want pools of it either, it's kindof something you get an eye for after doing it a few times. For laying the glass i typically just use cheapy brushes to wet it out, and sometimes paint rollers(they would be kind of excessive for something this small though). Then go over it with a roller to help pack it down.http://www.expresscomposites.com/ROLLERS.html I like the plastic ones or metal ones, I don't really care for the bristle type. Then if you do have any pools of resin I would go over with a brush and try to soak it up so before the resin gels up and starts to harden.

http://www.expresscomposites.com/ this is a place somewhat local to me that I like to get my stuff from and from what they have told me they can work it out to ship pretty reasonably, like shipping multiple containers to get past some of the haz mat fees.

I typically use a 1.5 oz mat and just apply more layers if i need more thickness, also if you have a large flat area it may be a good idea to reinforce it with a core material to stiffen it up. I used to use coremat alot when I was building kayaks and canoes to add stiffness without all the extra weight and cost of using just mat or cloth.

For a tail section you should be fine using a polyester resin and chopped strand mat. Mat will be alot easier to work with since you have never worked with fiberglass before. Cloth can typically make the part stronger and lighter but for something like that I don't think it would be worth the extra effort.
 

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Forearm of Steel
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2,581 Posts
Discussion Starter · #3 ·
If I just wanted to be extra careful, I could get some release agent (carnauba wax?) and put it on top of a couple layers of masking tape, right?

So my list will be:

Masking tape
Carnauba Wax
Spray foam
1.5oz chopped mat (i'm guessing 3-4 yards is enough?)
1 gal polyester resin

To get the part from fiberglass cure to final paint I would use normal bondo, sand, then fine filler to fill in the remaining holes, acetone wash, primer coat, sand, color coat, sand, clear coat, wet sand... Is this correct? I'm assuming it might take several tries with bondo and sanding.

I found a local supplier for chopped mat and resin (http://www.associatedindustriesinc.com/)... I'm still not sure of the prices but I'm guessing buying locally I avoid shipping and hazmat fees, right?
 

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if you spay glue some tin foil onto it and roll it down flat, with the shiny side up you don't even need release. I've never used caranuba for release, I usually use pva, or part-al release. Sounds like you got the finish part down pretty much though, I usually try to get it sanded pretty well with like 150 - 220 grit before bondo. the better you can get it before filler the easier the bondo will be.
 

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I bang metal
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do not use carnuba wax or turtle wax, i forget what exact ingredient it has but it keeps the resin from hardening. Like bend mentioned, use pva
 

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I bang metal
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Forearm of Steel
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Discussion Starter · #7 ·
this is where i used to get my stuff.... im sure there is a better place

http://www.uscomposites.com/
Thanks for the link! I didn't know that only 5 gallon pails were subject to the hazmat fee. I ordered 4 yards of 1.5oz CSM, 1 gallon of resin, and a small bottle of surfacing wax for $60. I will post pictures of the tail section when it's been shaped (this weekend) and when I lay fiberglass down (next weekend, i think)
 

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Just Here For The Party
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Laying fiberglass, like everything else on this site, is easier the more prepared you are for it.

Take an old sheet or t shirt and cut a square out of it bigger than your piece in question.

Drape it over, and begin smoothing it and taping it down. Use a pair of scissors to cut out any bunches that can't be smoothed out. When you get everything "perfect" (I always liked "good enough for me!") Cut away all the left over bits of fabric. This is basically your cutting guide for your fiberglass.

This is really good for doing your piece in larger single sheets of woven mat.

If you're just using chopped mat, then just cut the fiberglass into a bunch of squares, rectangles and strips. Small manageable pieces are best.

Get all your pieces cut and ready BEFORE you mix any resin and hardener! Lay everything out in the order you're going to place it on your piece. Double check everything, and have some extra scraps of material laying around. For whatever reason, I've found that rough cut triangles always end up being useful. Are you embedding anything? Does the piece need reinforcement anywhere? Get all of that stuff ready to go now.

When everything is ready to go, mix your resin and hardener up, then grab a 2" chip brush and liberally coat the surface of your piece before you put any fiberglass down. Lay your first piece and smooth it on with your hands. The use the brush to dab the piece down into the resin. It will turn translucent when it's soaked through.

Do this for all your layers, using less resin with each successive layer, just keep pressing and smoothing and cursing it down. It's doubtful you'll get all the air bubbles out, just get them as small as you can. Don't let those little things keep you from getting down all your layers though.

Resin/Hardener is temperature and humidity sensitive. If it's a cooler day/moister day it will take longer to setup. I did a piece in February, that I'm 100% convinced is still not entirely set up yet. I say this because after you lay your piece up, walk away from it. For like 2-3 days; don't even look at it. Just let it harden up.
 

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I bang metal
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2,779 Posts
I used carnuba and the glass cured fine for me. I used a paste with zero problems

Sent from Motorcycle.com App
yeah, you are right. Carnuba wax is what you want if you use common wax. I forget what wax is bad, i just remember that it is styrene based and the resin will eat it.
 

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Forearm of Steel
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Discussion Starter · #11 ·
For like 2-3 days; don't even look at it. Just let it harden up.
Is it possible after 1 day that it is cured to the point where I can remove it and set it aside? It shouldn't be humid or cold, so I figure a 24 hour cure would be fine. I just need to get it off so I can begin other work on the bike.
 

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Just Here For The Party
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Is it possible after 1 day that it is cured to the point where I can remove it and set it aside? It shouldn't be humid or cold, so I figure a 24 hour cure would be fine. I just need to get it off so I can begin other work on the bike.
Yes, it's normally fine after 24 hours. I work a little humor into my explanations, should probably stop that.

Tap it, it should give a solid knock sound, like plastic. If it doesn't then it hasn't cured.

A little heat will help the process go faster. An even heat at not to high a temperature will help things go quickly.

Although hold off on painting it for a week, fiberglass off-gases for a little bit of time.
 

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Forearm of Steel
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Discussion Starter · #13 ·
Yes, it's normally fine after 24 hours. I work a little humor into my explanations, should probably stop that.

Tap it, it should give a solid knock sound, like plastic. If it doesn't then it hasn't cured.

A little heat will help the process go faster. An even heat at not to high a temperature will help things go quickly.

Although hold off on painting it for a week, fiberglass off-gases for a little bit of time.
gotcha. I've got a space heater I can set up for the first few hours after I lay down the glass.

The worst part about this is that my subframe sweeps out instead of towards a point, and that makes it difficult to get a good shape. I'm not completely sold on what I have right now, but I can always do another fiberglass tail or subframe/tail swap in the future.

I'm also planning on making the undertail section out of fiberglass. Any tips on what would help prevent damage or at least be the most durable? I thought about finding a piece of sheet steel, painting it, and riveting it to the fiberglass.

I also thought about looking for a mounting point and making a rear tire hugger at some point.
 

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Just Here For The Party
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gotcha. I've got a space heater I can set up for the first few hours after I lay down the glass.

The worst part about this is that my subframe sweeps out instead of towards a point, and that makes it difficult to get a good shape. I'm not completely sold on what I have right now, but I can always do another fiberglass tail or subframe/tail swap in the future.

I'm also planning on making the undertail section out of fiberglass. Any tips on what would help prevent damage or at least be the most durable? I thought about finding a piece of sheet steel, painting it, and riveting it to the fiberglass.

I also thought about looking for a mounting point and making a rear tire hugger at some point.

Fiberglass is pretty durable in its own right. Sheet steel is overkill in my opinion, but it's your bike.


Get a piece of foam insulation from Lowes or Home Depot (The blue kind is best), cut it into blocks and start shaping it on your subframe. You can make a shape that you like and then lay fiberglass over it kind of like what this guy did.
 

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Forearm of Steel
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2,581 Posts
Discussion Starter · #15 ·
Matt, thanks for all your help.

I already had the base laid (spray foam/bondo, never again) and I laid 5 layers of 1.5oz chopped strand mat. It cured in less than 6 hours - it was a warm day here today. I mixed the right proportions and found I had a pot life of about 20-25 minutes.

All in all, it turned out okay for my first try. This frame is really difficult to design and implement, but I'll post some pictures later (probably tomorrow evening after I trim and do a initial sanding and then after bondo/sanding.
 
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