Can someone give me Fiberglass 101?

I got some body rust that needs to be filled. Local tech suggested "kitty hair." I don't know anything about fiberglass, can someone give me Fiberglass 101?

Kitty hair is just fiberglass reinforced bondo. Not good for filling a gap.

I'll dispense with the obvious, welding in new metal is the only correct repair.

Ok, that's out of the way. Grind, cut, clean the area well, get rid of as much rust as you can. Hit it with a good primer and paint and let it cure, might as well protect what you have left, any rust that forms between the fiberglass and the metal will just cause the patch to fail faster.

Get some fiberglass and some resin, your average auto parts store kit will do fine for this purpose.

Cut a section of the fiberglass cloth so that it overlaps the rusted area on to the good metal by at least an inch on each side, 2 is better.

Wear rubber gloves, resin does not come off the hands easy. Mix up the resin according to the directions. The auto store stuff is a heat cure so if its cold, a little more hardener, if its warm a little less. You have maybe 5-10 minutes of working time so have everything laid out and your cloth cut in advance.

Now using a disposable paint brush put a little resin on the metal around the patch area, then brush your cut cloth patch so its saturated, you dont want it dripping, just soaked through. Apply it over the hole and try to smooth it out as best you can. If its too wet it will try to sink into the hole or slide down the body depending on the orientation of your piece so dont overdo it. Let it cure, you can toss a heat lamp or other heat source at it if you didnt mix it up right and its not curing. Repeat with a 2nd layer for strength. Sand, fill, etc to your preference.

"Cat hair" is like bondo, only instead of clay (bondo), there's short cut up fiberglass strands. It dries harder than bondo and is, at best, a half-assed rust repair, but better than straight bondo.

Link to a fiberglass tutorial I did. Not about body repair but some of the info may be relavant.

http://misfittoysracing.com/Yugo/flaretutorial/index.htm

Thanks guys.

Yes, this will be a temporary fix. Inspection time next year I plan on having the tools and skills to do a complete rust repair, but on the limited time I have, fiberglass is going to be the solution. It's getting cold and my inspection sticker is expired, and I'm getting to the point where I need to think about switching from the motorcycle to the car.

Do I need to be concerned about breathing the resin fumes?

JThw8 wrote: Link to a fiberglass tutorial I did. Not about body repair but some of the info may be relavant. http://misfittoysracing.com/Yugo/flaretutorial/index.htm

those flares are totally badass!!

Taiden wrote:

JThw8 wrote: Link to a fiberglass tutorial I did. Not about body repair but some of the info may be relavant. http://misfittoysracing.com/Yugo/flaretutorial/index.htm

those flares are totally badass!!

Thanks :)

About the fumes, um, I dont wear a respirator but it's probably not a bad idea. At least work in a well ventilated area.

Taiden wrote: Do I need to be concerned about breathing the resin fumes?

Only if you'll be driving or going on a job interview!

Be concerned when you start to grind the excess. Real good idea to at least have a paper mask. The hardener for fiberglass resin is MEK, a really nasty carcinogen. Best to keep it out of your system. Glass itself is also not a good thing inside. Proceed with caution. Also, that acetone you used to clean up with? Dangerous in many ways, including explosive. I made many fiberglass bodies back in the day. Can be scary stuff.

Dr. Hess wrote: "Cat hair" is like bondo, only instead of clay (bondo), there's short cut up fiberglass strands. It dries harder than bondo and is, at best, a half-assed rust repair, but better than straight bondo.

So, does thad make straight bondo three-eighths-assed? I think that's about right, if not quarter-assed.

Clem

I think quarter-assed or less. Actually, I think straight bondo over rust holes is "not repaired at all."

Unless you back it with duct tape first.

hahaha. This aint a rust repair as much as a, "get me a damn sticker so I can get to class in the winter" repair.

EastCoastMojo wrote: Unless you back it with duct tape first.

You can add an eighth-ass or so if you fill the hole with spray foam, let it set up, trim the excess, THEN put the bondo on it.

16vCorey wrote:

EastCoastMojo wrote: Unless you back it with duct tape first.

You can add an eighth-ass or so if you fill the hole with spray foam, let it set up, trim the excess, THEN put the bondo on it.

So THATS what I keep finding under quarter panels in early 90s japmobiles in Maine...

Jim, that tutorial was excellent and the timing couldn't have been better!

Thanks!

Marty! wrote: Jim, that tutorial was excellent and the timing couldn't have been better! Thanks!

I've had it out there for years, it comes to the surface around here every once in awhile. Glad it can be of some assistance to folks. I was pleased to meet the Condor folks at GRM and find out that the 1st version of their car used fiberglass flares based on that tutorial. The new version uses steel but its still nice to know it helped.

Fiberglass isnt that hard to work with once you get a feel for it. Go forth and make some things and you'll learn to like it.

Question: Is the rough mat better to use than the woven cloth? On one of the "Hot Rod TV" type shows they used cloth on a large mold.

mapper wrote: Question: Is the rough mat better to use than the woven cloth? On one of the "Hot Rod TV" type shows they used cloth on a large mold.

Depends on what you are making. The rough mat allows you to make structure with less layers but it is rougher and requires more finishing.

The woven cloth can actually be stronger in multiple layers and provides a smoother product, but in single layers its fairly flexible whereas the rough mat will have less flex and more substance.

For real strength you can use the 2 together.

Im sure there are much better technical explinations and specific scenarios for when each should be used, these are just my personal opinions from working with it.

how come no one posed the obvious answer to his needs. ..... just cover the hole with a grm sticker!

itsarebuild wrote: how come no one posed the obvious answer to his needs. ..... just cover the hole with a grm sticker!

This!

Actually on our first BABE rally vehicle, a big Chevy van which was rusted out all along the bottom I just stuck big sheets of adhesive vinyl over the entire bottom of the van to cover the holes. The guys at the inspection station were so appauled with the rest of the van they didnt even notice. It came off before we made Staten Island for the start...but it held long enough.