How much fiberglass is enough

I have some spots on my body that I am currently dremeling out and filling with west system epoxy. I also wanted to lay some pieces of glass on the backside and was wondering how many sheets is enough on one spot. I have the 1.5 ounce fiberglass and know that when you lay it your supposed to overlay them with the one behind larger then the one before it. How many layers is good enough 2,3,4,5? I am going to paint this thing and want to make sure I do my best to avoid spider webs in the same spot.

Also if you guys know of any common spot that could use extra reinforcement while im at it that would be great.

Mat:

Where and why are you attempting to add thickness to your body?

Is it a CMC body or something else? I ask, because usually CMC's are thicker than they need to be (except for a few areas, like around the headlights on some bodies - not all!). Other body manufacturers might be different in thickness or weaker areas. the problem with CMC bodies is NOT the thickness of the body material, but with the lack of proper structural support for the body itself.

So what are you trying to modify, and where?

The number of layers of glass mat depends on where and how it's applied. If it's for lateral strength it is layed up differently than for torque strength. Usually, for lateral strength, you lay the mat at 22 or 45 degree angles to the last mat put down. If it's for torque strength then it's layed at 90 degrees only.

The number of layers depends also on the thickness of the mat material. Usually 2 layers gives you just less than 1/8" but if you use thick, industrial-strength cloth you might end up with 2 layers giving a thickness of 3/16" - pretty heavy stuff. Also.West Marine sells a bondo-like substance with chopped glass fibers imbedded in it that can be mixed and spread onto a roughed-up fiberglass surface to provide additional strength without doing the mat-and-resin dance.

Hope this begins to help.

gn

I am not trying to add fiberglass to the whole thing only behind the spots that are spider webbing the gel coat. I am using the west system with that sand additive to fill in the spider webs on the gel coat which is what I heard works good but I figured I should reinforce the back side too. The spots are right above both sides of the tail lights, above both of the front tires, also around the doors there is some, also a lot right in front of where the windshield mounts. Also a lot of cracks around 3 of the fenders. I am just worried that I am going to paint this car and then think crap I should have done more prep.

Mat -- don't forget: You can epoxy over polyester resin but you can't polyester resin over epoxy. Your fiberglass is no doubt polyester resin.
You are ok with what you are doing (West Systems products are outstanding for the purpose). Just don't come back over your epoxy repairs with polyester resin fiberglass or Bondo. Once you go epoxy, stay epoxy!

If you are only making repairs to the gel coat (spider webs) then you are not creating any "strength issues". The gel coat provides no strength (you could sand it all off, it wouldn't matter).

If you are repairing damaged fiberglass, then how to repair it involves a bunch of variables. There are a ton of videos on youtube to give you some step-by-step tips. For example: http://www.youtube.com/watch?v=6N7YMr6E564

Mat,
Are you going all the way through the body creating a hole in the
body? If so you will need to taper the opening. Go to Youtube
and search, there is a good short video by TAP Plastics on fiberglass
repair. Back in my old Corvette days when removing the spiders if I
didn't go all the way through the body I usually used 2 or 3 layers of mat on the back side depending on the size of the area being
worked. Have fun.
Bill

Thanks for the advice guys. I want to prime the car with the 2k primer stuff that I think is epoxy. Is that ok over the gelcoat I dont plan on ssanding all the gel coat off. I am dremeling out the cracks past the gel coat and into the fiber and will throw some layers on the backside. Thanks for all the info.

Id estamate the mid 60s and 70 vette bodys were between 1/4 and 5/16 thick 3 or 4 lays of cloth.

But I did go thicker on the D and On my elcamino ground effects but not over 3/8..

Yup, that sounds about right, although I bet on some of the CMC's that Jose, the chopper gun pilot (or was it Julio?), fell asleep from time to time and some areas of some cars (not consistent between cars by any means) can sometimes be WELL over 1/2" thick. That may account for the difference in weights between cars when we weighed them at Carlisle - identically equipped cars might be as much as 150 lbs. different in weight or more (and not from different levels of fuel in the tank, either).

After you finsh glassing the unerside . No sooner than month afterwards coat the bottom with a black urethane rubberized coating.
It will help prevent staring type chips in the fenders. and help seal up the body inside and out .

This one step done well will prevent paint bubbles and paint failure. Ever wonder why some kitcars go south real quick and by no fault of the owner.. Ding Ding Ding!! moisture gettin in under the paint.

Guys her wonder why I took so much time under my car 3 years prep thats why. it was bone dry the day it was shot and cleared.

Hey Matt....

Are you using fiberglass cloth...or mat? (no pun intended)

Mike

Its the 1.5 ounce stuff got it at a wholesale place.

...but is it cloth or mat? Post a pic.

You got resin and hardener.. Right But no cloth?? I like the woven cloth better.

Figure out your patch size. paint the area to patch with the hardener /rezin mix with a paint brush.

lay in the cloth patch and repaint it as quickly as you can. Shoot for less than 3 minutes .

Wash out the brush with Acetone. the sand area after it hardens.

Do at least 3 lays that way to get strength and a 1/4 inch thick patch .

I have covered the patch with suran wrap to allow hand mulipulation to adjust the lay

,And it does help it harden quicker

If you are just fixing spider cracks, dremel them out and if they don't go all the way through, fill them with "gorilla Hair". It is a resin with chopped fiberglass already mixed in. It comes in two versions, one finer and the other more coarse. If they do go all the through, two layers of 1.5 ounce should work or probably a single layer of light matt.

Or, just drop the car at Randy's shop in Chambersburgh, PA, pay your money and pick it up all painted nice! Excellent work for a decent price too!

In a spider crack i would grind futher beyond the area and do a 2 layer cloth overlay

A second option is Dyamax super strong epoxy resin and strainded cloth a inch over size the area. its the stuff they use to glue fibergass parts together on vettes and big rigg noses like a freightliner.

Its some tough stuff!! but expencive $$$$

The green stranded putty and jelly are not strong enough for a area like a lower front fender well that may vibrate. it will likely recrack.

I found something called Dymax but no real place to buy it from is that what you are talking about? Is that stuff that much better than something like west system?

How would you go about patching that chip in the hood in between those 2 blue pieces of tape?

Also I have two holes in the fiberglass where the windshield mounts and around that area there was some cracking that I am assuming was from the movement of the windshield whole driving or the pressure from the top when that was up. Do any of you guys put better reinforcement in that area like metal?

I would grind the top and bottom area past it by one inch. and use stranded cloth cut up with sissors and mix the regular resin and hardener into a peace of suran wrap and add the clippings . then pick it up by the suran wrap and hold and mold it into the wound untill it sets up some..

One more warning!! Always shake your resin can before you begin a mix the activater is bad to settle to the bottom of the can..

Its not rocket science and its not hard ,But have some acetone to clean your hands afterwards it is messy ,,you could were latex gloves but . I have a hands on aproch i like to feel what im doing and can tell when the resin starts to heat up as it hardens and i us my fingers . Via the suran wrap to move it where i want it.


The next day is when you start fileing it to shape and if you boo boo a little regular body filler is fine for miner stuff.

use a metal file to chrisp up the edge and rough block it with 40 grit and then jump to 80 grit to get it close. witha rubber block by hand.

Relax and take your time with it. and you will do fine

When I grind it down I take it I should grind down past the gel coat.

If you realy want to be fast with it do several places on the same day and just continue the next day to catch it up. Then repeat day by day untill it all looks perfect.

I let the car rest a week sometimes 2 weeks to give the stuff a chance to gass out and scrink on bad spots .

Then repeat again on the problem areas

It wont take you long and you'll be a pro at it. Just look and feel it.

This why ccorvette work is so slow and expencive it takes time to do it right

Yes rough it up a inch or so around it just enough to pull the jel coat and epose roughed up glass..

when you get nearly done blocking it back out you can put on some high fill primer just around the spot 3 or 4 inches out and then block it with 220 grit the next day by then you can just prime and block and prime on a step by day scheldule to remove any scratches and ripples. If your using epoxy primmer you can paint in a day or 2 but with the cheap laquar you miust wait a month for it to cure or the paint will spyder web terably.

then water sand with finner grits to the prep stage for the last stage sealer and paint. which is ussaly done the day of paint after a final sanding and tack ragging when you have tape up any place you don't want over spray.

What type of paint are you plainning to use