Cutting fiberglass?

[Wade Lippman]

I did something really stupid with my fiberglass kayak and have a bit of repair to do.

I want to tape the parts together with duct tape to get them in the right place, and put new fiberglass/epoxy over it all. As long as the tape adheres, it should be just as good as going directly to the kayak; maybe better.
My neighbor is a professional and says the epoxy will soak through the duct tape and make the whole thing a big mess. The tape is waterproof, but he says it is not resin proof.

I cut some fiberboard in half and taped them together with duct tape. I then put a couple layers of fg on top. It looks pretty good, but I want to cut it up to see how stuff is adhering.
I have a choice of a carbide TS, a carbide BS, a jig saw, and a carbide circular saw.
I am thinking the jig saw so if it ruins a blade it is just a few dollars instead of a hundred.

Any advice here?

[Walter Plummer]

Any of them will cut it but go with the jig saw. The glass should be ground back and the repair done in layers each a little larger than the last until the thickness is right. If you know it was built with polyester you can use polyester to repair it. If you don't know or think it is epoxy then use epoxy to repair it. Epoxy does not work well with chopped mat so use cloth to make the repair. I have done some composite work but by no stretch an expert. I'm sure you can find tutorials and videos.

[Martin Wasner]

Cut it with an abrasive wheel in angle grinder.

Anything with a tooth will pull and rip.

How big of a hole? Sometimes a dremel works well on little stuff. I've used hotel key cards to act as a backer when making small repairs to the trailing edge of dagger boards and rudders numerous times on sailboats. The cards pop right off, and if clamped well there's minimal fairing afterwards

[Wade Lippman]

The top and bottom have pulled apart. I want to use the duct tape to hold them in place, as the fg won't do that. No real way to clamp them.
I have epoxy and and cloth from previous repairs to two sailboats, a rowing shell, and a fiberglass shower. Just never had to pull ends together first.

While looking for a metal blade for my jigsaw I decided to try my scroll saw. Went through like butter.
The resin did not hurt the duct tape, but it didn't adhere to it very well either. I have to either find better tape or use it very sparingly.

[Peter Christensen]

Tape it together on the outside and then apply some resin and a strip of glass cloth to the inside corner. When that sets remove the tape and glass and resin the outside.

[Wade Lippman]

Tape it together on the outside and then apply some resin and a strip of glass cloth to the inside corner. When that sets remove the tape and glass and resin the outside.
That might work; thanks.

[Doug Garson]

Look up stitch and glue kayak building, you would basically drill a series of small holes near the edge of each half, use wire to pull the two haves tight, glue the two have together with thickened epoxy, remove the wires and then reinforce the seam with glass and epoxy. Works when building wooden (plywood) and glass kayaks, can't see why it wouldn't work to repair an all fibreglass kayak. Can you post some pictures of what you are up against?