Fiberglass question

I know the car audio guys use fleece and t shirt material on their cusom bixes. It stretches and conforms nicely. Its a bitch to get a nice finish on though, at least in my one experience with it.

As i beed to make bolt on overfenders for the challenge car, and a body for my cyclecart, im going to be doing a lot of glasswork in the coming weeks.

I want to make life easier. These dont have to be structurally rigid forms, but do need to be somewhat durable.

Im thinking t shirt material stretched to shape, and soaked in resin.

What stretchy material should i be looking for instead? Im sure plenty of guys here have done similar things.

Depending on how complex your shape is, 4 to 6 oz glass cloth will move a surprising amount.

Actually incredibly complex. Easiest way to make it is going to be wax the fender liberally, cover with blue painters tape. Spray super 77 on the tape, stretch material over tbe wheel arch and attach to desired places with the glue. Resin the piss outta it, and trim off excess. Pop from the fender, add some matting to the backside for strength.

At least this is how it works in my head.

What about expanding foam and trashbags? Carve your own shapes?

With something stretchy you still need to stretch it over something else.

The strength of fiberglass is in the glass cloth or mat. The resin has no strength, relatively. So you are looking for the strength of a T-shirt? Why not use proper cloth and mat?

just remember, 'glass does not like to make right angles. You can make it stick into a right angle corner, but making it bend around a right angle will be difficult. Best to round off the edge of the corner first.

'Glass is also fairly rigid and brittle. Have you thought about epoxy like I use on my boats? It has a longer cure time, smells a LOT less, and is easier to mix and use.

It is hyperallergenic though, so keep your skin covered and try not to breathe the fumes too much if you decide to make a living using it

Ok, so does a mat product stretch? Part of the way i am thinking about this is as almost a vacuum formed piece. Lots of curves, but no real sharp angles. Just smooth radius. Im attaching the wheel lip at desired location, and then working matrial back to the flat surface of the fender for a bolt on flange.

Did that make any sense?

you NEED to make overfenders for gary?......is that the little guy on your left shoulder talking to you......with the horns

So, is your problem that you want to fiberglass air? Is that where this silly T-shirt idea is coming from? Put whatever you want that will support a layer of cloth (paper, cardboard, whatever,) put some wax paper over that and the cloth down on top of that, wet it out, let it dry, add more cloth and mat until it's strong enough.

Having been doing some fiberglassing over the last couple days myself, I recommend cloth over mat. The mat seems to come apart if you try to work the resin in via a brush, or even with a roller.

I've done light fiberglass work in the past to repair the glass on my race bike. Nothing like that what I am attempting to do currently.

I'm currently building an enclosure to go between the engine and the trunk of my kit car that had to be cut out for the new engine to fit. Having watched many YouTube videos and a visited the advanced composite Community College school near my house I decided to try some high-tech Manufacturing in my garage.

I made a mold laid down some epoxy for a gel coat. Then put a couple layers of glass and resin rolled it up in some plastic and threw it in a huge Ziploc vacuum bag for storing clothes and vacuumed it down. All went fairly well. It needed some more glass so I gave it a coat of resin put the glass some more resin Karma threw it in the bag and vacuumed it down. It did not go so well with the second coat of glass as I forgot to wrap it in plastic before throwing it in the bag. The corners dug into the vacuum bag and tour the bag. Hit would not hold a vacuum even after the tears were taped up. I'm going to need to do some additional work.

If I ever decide to redo this piece, I think I will build a vacuum forming table to pull the plastic tight around the peice instead of using the vacuum bag.

I used what I had for glass both Matt and cloth, the mat came apart on the brush and roller, but the cloth stayed together due to its woven nature instead of random strand nature. I think the cloth also was easier to form them around the curves.

This might help.

https://www.youtube.com/embed/mB4NXA_vNWs

When I was in the car stereo game the idea with the t-shirt or fleece was to get a hard shape that you could then build on. For most projects the finished side would get the bondo with fiberglass fibers in it first and then the smooth over that. The back side was generally layers of mat, cloth, and/or chopped fibers soaked in resin.

And that all is stretched over an armature with an mdf ring for the speaker to screw into. And it's all designed to be heavy, so it doesn't vibrate.

For fenders, you want a thin strand or lightweight fiberglass cloth that will stretch, and multiple layers.

In reply to oldopelguy:

Pretty much hit it. Im thinking of the genders luke building the top of a sub box. Can you give me a link to the stretchy fiberglass cloth you are talking about?

I don't have a link. Kinda by definition fiberglass fibers can't actually stretch, so you want to look for a loose weave with thin strands so you can slide and move the fabric around. Generally you look for the lightest weight fabric you can get.

Aircraft Spruce sells 1.8 oz/yard "#120" Kevlar woven cloth. It's 0.0035" thick. That's what to use here - strong, abrasion resistant, very drapeable.

Fiberglass (fire proof) curtains might work for you. Really stretchy and super cheep. These would be hung in motels, RVs and campers. Easy to find, pretty much like fiberglass mat or cloth, but a looser weave so that they stretch a whole lot like t-shirt material does.

If you DO use t-shirt material, find one made of polyester fiber rather than all cotton or polyester-cotton blend. Cheap stretch pants and the like (found in thrift stores/Wallmarts/etc.) are usually all polyester and would work well for what you're planning.

i concur with using a stretchy material to build the initial shape, just rigid enough to add stronger material (like glass) on top of, if you were stretching it over something like a wire-frame.

If you use a non stretchy material, you may end up having horizontal-ish surfaces sag while it's curing, once it wets-out and starts to get a little heavy.
the stretchy material should fight that tendency a bit, and hold the initial shape better till it's cured, and then you can proceed to go over it (reinforce) with something stronger like woven glass, or whatever.

Two_Tools_In_a_Tent wrote: Fiberglass (fire proof) curtains might work for you. Really stretchy and super cheep. These would be hung in motels, RVs and campers. Easy to find, pretty much like fiberglass mat or cloth, but a looser weave so that they stretch a whole lot like t-shirt material does. If you DO use t-shirt material, find one made of polyester fiber rather than all cotton or polyester-cotton blend. Cheap stretch pants and the like (found in thrift stores/Wallmarts/etc.) are usually all polyester and would work well for what you're planning.

Do you have a link? Sounds perfect.

lastsnare wrote: i concur with using a stretchy material to build the initial shape, just rigid enough to add stronger material (like glass) on top of, if you were stretching it over something like a wire-frame. If you use a non stretchy material, you may end up having horizontal-ish surfaces sag while it's curing, once it wets-out and starts to get a little heavy. the stretchy material should fight that tendency a bit, and hold the initial shape better till it's cured, and then you can proceed to go over it (reinforce) with something stronger like woven glass, or whatever.

Thats the initial plan. And build up SMOOTH layers for less bodywork. Granted it is a challenge car...

How about carbon fiber? This is the dash in my race car(excuse the dust). It's 1/4" dia steel frame with carbon fiber over Coremat

I'm totally confused at what you're trying to do...this is for front and rear flares, right? Are they going to cover entire circumference of your fender opening?

It is essentially going to be a bolt on wide body Fender Flare. It'll cover the entirety of the rainiest wheel well and come out to the outside edge of those gigantic Circle Track slicks creating a nice large flare. Then cold imsa race car.

After accomplishing them please post a step by step DIY and cost. I may need to do something like this in the future.

Chadeux wrote:

Very similar to this.

I liked the cheap white styrofoam from the insulation department at the hardware store. Glue the sheets together cut with a bread knife, spray foam weird shapes, glue and tape as needed. This gets you a basic large form. You can Bondo on top of the foam and sand as needed too.

But make sure to coat the foam with the product of your choice before applying resin. The resin will dissolve the foam. This can be paint to tinfoil.

Then wax or oil the surface and lay the mat. The foam can be sacrificed once the work is all set up.