Fiberglass question

Are there various different thickness of fiberglass cloth, where the individual threads would be closer together than others, and if yes, what would be the one with the tightest weave or the best for small patches?

It seems that every time I go to wet out a small patch, (say a inch wide by a few inches long), I have to fight the threads along the sides from coming apart.

thanks in advance,


Fiberglass is made in a huge variety of thickness and weaves. Usually you have to order what you might want because boating stores usually just carry the most common middle weight weave as you know. Go to a marina where they do fiberglass repair and maybe they will give you a scrap of what you need.

different weights. Last used 4 oz on a paddle blade. Threads smaller and tighter than 8 oz stuff I previously used, but the edges always come apart to some extent.

Try using a bigger patch, only wet the area your smaller patch would have covered, then let it set up. After it dries, use a sharp-edged putty knife to cut the threads of the excess cloth at the point where the dried resin ends. Finish it off by sanding. This doesn’t solve the unraveling threads issue, but avoids it.


FG Tape
You can get it in different widths and weights, 1.5 or 2" is common. One edge is closed and the other is sewn so the only unraveling is where you cut it to length.

No way around the fraying
so cut the patch big and pull some of the threads out of the weave before you start in order to keep that junky mess that results from loose threads in the epoxy.

Bias cut patches will fray less during
layup. The strands that fray will be shorter. Bias cut patches conform to compound/ complex curves better, and when patching a crack, a bias cut patch puts twice as many strands over the break as a patch cut parallel to the fibers.

You can get the tape at OR
I have a bunch of it.

Fiberglass cloth
Use “Super Glue” to wet out the line where you intent to cut. Once it sets up, cut with scissors along the hardend line. This eliminates the frayed edge.

Or, buy the figerglass tape. It won’t ravel.

Jack, I have some glass that you can
barely blow through, let alone wet out … but it all still leaves an ‘edge’ … Best bet is to use some wrinkle free 4 mil plastic or peel ply ( that stuff I sent over ) to smooth the edges down. If you don’t have this put your last patch on dry and gently ‘tamp’ it to wet out with resin already there from below … Or do this with a piece of 4 ounce or less over the repair … Tamp only, no ‘brush’ with bush. Go right out to edge and stop. You can also get a lighter weight cloth such as Hexcel 1080 from modeling stores. Sanding if any is a quick shot with 120 and that would be it. The fiberglass tapes sewn edge really does not lay down any better than cut patches, in fact it often rolls up and is worse. No need for this unless you are doing a long, skinny run such as a seam.

You can trim the edge with a held @ super low angle utility blade too when the resin is still green.

Call me if you want.

Yes, but they still fray

– Last Updated: Oct-13-09 4:10 PM EST –

I found that it was easier to work with the more closely-woven 4 oz. glass than 6 oz. glass. But it still unravels; they probably all do. Even glass tape doesn't really solve the problem, because you still have to cut it across where it will fray, plus the sewn edges tend to curl up and cure as hard ridges. Of course, you can later sand those curls a bit and then brush epoxy over them to seal again.

The 4 oz. glass is easier to fill to a nice surface, too.

Reduce the amount of fraying by not applying too much force when applying the epoxy. Don't push hard because that causes the weave to open up and come apart. (Been there, done that.) So go easy when squeegeeing excess epoxy out.

Many thanks for all the advice
and offers, here as well as private e-mails.

We have the most wonderful club in the world here on P-net.

My patch was done yesterday, and I’ll finish it off tomorrow, but I was trying to plan ahead for the next time, and I got some good all around advice as well.

Regards, and thanks again,