reproducing hull to deck seam line

-- Last Updated: May-14-11 7:02 PM EST --

I'm wondering what methods are used to lay up the heavy gel-coat seam line of a British style sea kayak?

The thickness is much greater than can be produced with several layers of masking tape while the edges appear to taper as to not protrude greatly from the hull and deck.

I'm doing some repairs and seam line is next. Thanks!

Glass tape
I found that heavy fiberglass tape either in layers, or doubled over if it’s twice as wide as you need makes a pretty convincing repair once you gelcoat it and blend it in with sanding.

Try it on a piece of wood first, and see if it is the right thickness. If it is, do it on the boat.

Does your kayak have a true outside
seam, one made of glass or poly tape and resin?

If you were to replace a part of a seam with glass tape, epoxy resin would be the practical choice. But then you have to take that into account when you choose a gelcoat. Some gelcoats may not adhere well to an epoxy surface. Otherwise you’d have to get vinylester resin and catalyst. Vinylester’s strong and easy to work with, but much may go to waste because it will slowly harden in the container.

Are you clear on the need for a structural repair to the outside seam, or does the seam already seem normally rigid and strong, so that you just want a cosmetic match?

the glass repairs are already done with vinylester.

I am just looking for an easier way to build up the seam line and make it look right. I was thinking of thickening the gel with microballons, but I don’t know if that is the right approach.

Melt your brain
Clear gelcoat, waxed styrene, microbaloons, and lots of tint.

Always start with clear gelcoat. I can’t believe how many times I’ve heard people complain that they can’t make black gel coat by adding black tint to white gelcoat. Even adding microballons to black gel coat will result in a grey, it’s much easier to work with clear gelcoat.

You can make your own waxed gelcoat by shaving wax into styrene then mixing it in with the gelcoat. Styrene is awful stuff to work with so prepare to forget your name for a while.

The pretty seam lines are done during cure. Apply the waxed-gel seam line and wait for it to become less runny. Peel the tape back across the new seam, this rolls the gelcoat back onto the seam. There is a fine point in time where you can do this, to early or to late in the cure and it’s a mess.

If you had graphite powder, which
West sells, you could get a quasi black result. Sanding the graphited resin will make it look grey, but then if you apply some varnish, it will probably look black again.

Worked great
The great thing about a forum is that one can read everyone’s comments and pick out the bits and pieces they are looking for.

I have no trouble making black gel using neutral gel and adding black pigment. I always use waxed styrene with gel, as I find it makes it easier to sand and see what I am doing while sanding. When I do white, I buy finish gel so I don’t have to mess with the wax.

I ended up using nothing to thicken it. I secured the boat up on it’s side so I could apply it without it running. I used 4 layers of masking tape on each side as a dam and wet the area with a thin layer first before blotting a bit heavier with an acid brush. I pulled the tape just as it started to kick off. The seam looks almost perfect, just not quite as smooth at the tape line as Valley did it. I think if i’d have pulled the tape a minute earlier, it would have been perfect, but I doubt anyone but me will ever notice.

Thank you all for your input. In the end it turned out even better than I thought it would.