kayak hull deck seam tape

-- Last Updated: Jan-30-10 12:55 AM EST --

The subject of this post contains search terms I was trying. Seems like this has to have come up here before, but darn if I can find it.

The Kanoe Latvija (kayak) leaks at the seam between the rear deck and the hull. The seam is covered with that black tape, which I think is fiberglass. The tape seems to have split right at the joint.

If you have seen this kind of repair discussed before on this forum please give me some hints as to how to search for it.

If not, or if you just want to provide advice, please share ideas on an effective strategy for repair.

I'm starting to think the boat should go to the dump. But I kind of like it.

This is a 16' fiberglass kayak. It will be difficult to get at the inside of the joint because of the bulkheads and the lack of a hatch on the rear deck.


You could
install a deck plate so you can get to the inside.


link to tapes


fix from the outside
This happened to me a while back. I could barely reach the inside seam, but did manage to get some cloth and resin to the inside area (fortunately not visible). You’ll need to sand/drill around the length of the split (which for me was much longer than I first thought), then do a good job on the outside seam and your hatch will stay dry.


Not advice, since I am no expert
But a thought:

Why not sand the tape, (if that is what it is) off and just fix the crack/leak with epoxy. If it is wide, use a strip of glass.

Then use black gelcoat to match the rest of the strip.

On a QCC the strip that covers the seam where the hull meets the upper deck is gel coat. I originally thought it was some sort of tape too.

In my experience with cracks, holes, and leaks on both composite canoes and kayaks, epoxy has always worked

Good luck,


Don’t be scared…

– Last Updated: Jan-30-10 7:32 AM EST –

and don't be afraid to identify any weakened seam joint that may still be there but not visible. If the deck to hull joint was weakened to the point of a visible separation, chances are the areas nearby are seriously compromised. Before you add any material, make sure you are satisfied that you have removed anything that looks schetchy. All of it.
I don't mess around too much when making repairs. Wearing a dust mask, I break out the 4 in grinder with a thin fiberglass cutting wheel(made of fiberglass) to cut away damaged material. Then I remove gel coat by using the grinder like a orbital sander, being as gentle as I can to remove only the gel coat. I have tried sanding out the gel coat but that takes more time and patience and I can remove the gel coat much faster with a cutting wheel placed at a shallow angle and making long continuous sweeps. It would be super easy to make a giant gash with the grinder if it gets away from you so I cant recommended doing it this way but what is important is a good clean bond however you can. I was not really sure if the glass would bond to the gel coat well so I have been removing the gel coat anyways. Maybe I don't really have too? Seemed like a good idea especially at a joint like the seam at the deck/hull.

What I have done in the past is repair that joint from the outside. I have removed the gel coat from the fiberglass about 3/4 an inch on both of the joining surfaces exposing the fiberglass. I cleaned the joint with acetone. Not sure if that is the greatest thing to use but that is what I had in the shed. I then cut some strips of 12 oz cloth. Again it was what I had in the shed. I cut two strips. One was about an inch and a half wide. the second about an inch wide. Before I glass a joint it may be important to use something to manipulate the joint somehow to make sure the joint is in the position you want it to be in. I mean it be be foolish to try to place wet glass on a joint that isn't pretty close to it's original position. You may have to stitch the joint together before glassing if it is a huge repair. I did a complete hull to deck repair with the boat in two pieces. I screwed small pieces of wood along the joint as needed. They obviously remained inside the boat when I was done. I just made sure the screw heads were sunk enough to cover them seamlessly with the repair glassing. It was a lot easier than I thought it would be.

I used some west systems 205/105 epoxy and soaked the glass and boat well and placed the wide strip first followed by the thin one on top center on the joint. Covered with wax paper making sure to remove any bubbles of air by working them out by hand. Next day I sanded any lame looking rough areas and painted the joint and while it is definitely not a professional repair, the boat is water tight and makes me smile. I believe the repair I did is stronger than the original and probably heavier than it needs to be but it works.

I don't have much experience repairing fiberglass to a like new appearance but I have lots of experience doing repairs that keep my boats floating. Not sure if I am much help but that is what I would do if it were my boat on the brink of being discarded otherwise.

If you are anal about your boat's appearance repairs take longer and cost a bit more. For me it is good enough if the repair is reasonably functional. I don't even try matching gel coat.

Was the damage caused by the boat being compressed from the top or the sides? Don't be afraid to add some material at other locations that may be ready to fail. Push on the boat with your hands applying weight and try flexing the joints. You may be able to locate future problems ahead of time. Better to get em now.

I’m refinishing
and learning along the way. A quality 120 grit sand paper cuts through gel coat quicker than 60, 80, 100, or 150. Don’t know why.

Does anyone know if the black line on an NDK is just gel coat or tape? Looks like gel coat.

Scottb’s advice about cleaning up the
outide is good. For small area removal, I have been able to remove the seam with a rasp.

It is highly likely that the boat was seamed with FG tape and resin, not just decorative seam tape. But often boats were seam taped inside and then only decorative tape was applied outside, instead of FG tape and resin. In either case, it probably is not worth doing anything to the inside. An effective, if unattractive, repair can be done outside.

Seam tape can be gotten from johnrsweet.com as well as from RAKA, etc.

Because I keep Kevlar around, I would be tempted to do a two layer seam patch using bias cut Kevlar for the first layer, and glass for the second. You don’t need tape except for the convenience of doing a long length of seam repair. Kevlar and glass can be cut “on the bias” so that fibers run at 45 degrees to the seam. This doubles the number of fibers that have to break if the repair is stressed. And Kevlar is unlikely to break. Rather than doing concentric cloth layers, just offset the second on top of the first. The outer glass layer will wet out easily, mostly just absorbing resin from the inner Kevlar layer.

I have done inside repairs, and it is possible to tap a nail into the end of a stick so that a piece of tape or cloth already saturated with resin can be dropped on the break. But it is hard to properly sand and prepare the surface, and it’s just an awful lot of bother when an adequate repair can be done outside.

I can’t say whether an epoxy-only repair would work. Maybe if done with West’s new G-flex epoxy, it might last relatively well. But a cloth and epoxy repair is always a better bet.

Sounds emminently doable
I’m with you, Scottb, on the appearance vs. function.

I don’t really know when or where the damage occurred. According to a local guy that should know (Brad, at Starrk Moon Kayaks) the guys who built these boats were not known for quality. Before I added the bulkheads, I would not have known if I was taking water through the seams. Could be a longstanding problem, or could be that the two guys that were trying to lift this boat over a sea wall when it was full of water put some stress on the boat. Maybe a little of both.

I think I will roughly follow your procedure. As other posters suggest, epoxy and glass on the outside ought to hold. I’d like to get some FG tape, though, because it is a PIA trying to lay up thin strips of cloth. Seems like the cloth starts fraying as soon as a scissors hits it. I’ll check the link provided by another poster and see what they offer in the way of FG tape.

Thanks, all for info.



Tape & gelcoat
The seam on the NDK (and most all composite boats) consists of tape & gelcoat. Some manufacturers (i.e. CD) however, use an “H” channel between deck & hull, which can make locating the source of a leak difficult but it is a strong joint.

toss the scissors and pick up a
rotary cutter. The less you have to touch the glass the better. Cut it and wet it on the same board picking it up once to apply. It will still fray easily but not like when you handle the glass and scissors together. Terribly frustrating.

Note the change in email address for
Sweet Composites.


This link will bring up their page on seam tapes. They have glass, Kevlar, bias cut.

Strange, I’m a big, clumsy person
but I don’t find cutting glass or Kevlar cloth that frustrating. Might be because I usually cut on the bias. Cutting parallel to the fibers will have them jumping out !