Cracked seam - repair suggestions?

Now that I had a chance to more carefully examine the “new” kayak I have, I found I’ll need to fix an area of about 15" where the seam b/w the fiberglass deck and the carbon/kevlar hull seems to be broken. The inside still has the kevlar tape intact so they are not separated but the deck area flexes relative to the hull there so the epoxy on the seam seems to be broken.

Also, the outside strip that covers the seam is separated in that same area.

So there are 2 things I would like to hear advice about.

(1) The best way to fix the broken seam from the inside?

(2) The best way to re-glue the outside seam cover?

For (1) is it better to wet and apply some fiberglas or do I need to remove the old kevlar seam tape first? What cloth should I use? 9 oz seam tape or 4-6 oz cloth patch? I already removed the epoxy from the seam on the inside getting it down to the kevlar tape, which as I said seems to be intact.

For (2) I am just thinking of somehow (with a siringge and knife perhaps) suffing the small gap with epoxy and pressing it in so that it cures in a snug position. The gap is narrow enough to only allow to slide a knife thru the gap. Or do I need to remove the outside strip and fix the seam from the outside then live with an ugly repair patch on the outside (I would not have the patience to cosmetically re-create the seam strip and paint/match the gelcoat)?

Do I do (1) and then (2) after (1) has cured or do I do them at the same time or in reverse order?

I will also be applying a reinforcing cloth on the inside of the hull on another crack that seems to have been fixed from the outside but is visible on the inside and I want it covered. Probably light cloth would work there.

Lastly, what epoxy and materials would you suggest? I think I will only need a small amount…


If you have or can get a dental syringe
with a curved poly nozzle, you may be able to force a thin epoxy like West under that outside seam cover. What is that made of? Some sort of fabric in it? I used to work in a lab that had plenty of “real” syringes as surplus stock. However, the smaller the needle, the harder it is to force even a thin epoxy into a thin crack. Sometimes I have drilled a small hole over the loose over-covering (#2 in this case), and have pushed the tip of the dental syringe hard against the little hole so as to force epoxy in where it might not have gone otherwise.

As for that inside Kevlar seam failure, I guess you could try to force epoxy underneath, but then after it hardens, you should sand the top before applying glass reinforcement. I prefer to wet out the glass in place. You may have to find a way to lean the boat on its side so the epoxy does not run away from the repair. Don’t over-wet the glass. You should still be able to see the weave after it is wet out clear.

The epoxy question… You can get a West epoxy repair kit in little bladders, but I have not used one and do not know the mixing ratio. If it is the same 5:1 as West’s 105/205, that’s hard to judge or measure without a scale. Obviously mixing the entire pouches isn’t going to work. And the repair pouches are really not a good buy, money wise, as 105/205 in the smallest available cans, with the metering pumps.

Don’t consider West’s new G-flex epoxy. I’m using it now, but it’s too thick to get in where you need it to go. Convenient 1:1 mix, though.

I’ll probably go for a layer of carbon on the inside and squeze some epoxy on the outside of the seam then secure it back against the deck till it cures.

Would you suggest doing the inside and the outside at the same time or one or the other first?

I have the boat hanging from the ceiling at eye level so I can position it anyway I want along its long axis to have the epoxy pour in the right direction. Hope to not glue my hair or beard to the cockpit in the process like Patrick “entraped” himself :wink:

wall paper paste syringe
Those of us not in the medical community have an easy option for getting metal tipped syringes.

I found that some paint stores sell a large metal tipped syringe (wall paper paste syringe) to inject paste into bubbles in wall paper. They work much better than the plastic tipped syringes when injecting epoxy into closed spaces like a bubble under fiberglass. You will have to call a number of stores to find the one that stocks them in your area.


Thanks too
I have several syringes at home from our cat’s medications and what not. Hopefully one of them would work with or without a needle. If not, the wallpaper one sounds like a good idea.

My thinking is that if the mix is runny enough to be squirted out with a syringe, then I think it will just flow where needed in the seam area when I warm-up the area with a hair drier as Eric suggested and perhaps I can spread it around with a thin knife or better yet, probably with a very thin metal thickness gauge I have from the days I used to adjust spark plug gaps on my older car - these metal plates are really thin and flexy so they should go in the seam area where a knife would be too thick and rigid to go.

About to do the repair, a few questions

– Last Updated: Apr-12-09 10:21 PM EST –

Would you advise to cover the repair while it cures with plastic? And may be add a loosely filled bag of water on top of it to compress it? Would cling-wrap work for this or do I need something thicker, like a drop cloth from the paint department or a thick garbage bag?

2-nd question is on the material The advice I'm getting on fiberglass vs. carbon for this repair is evenly split b/w the "supporters" of each of the two materials. I got both so I can use either, just want to use the "better" material for the job. The area to be repaired is on the front'side of the cockpit at the seam b/w deck and hull, so this area should not normally see hard blows from rocks or beaches or anything else that would threaten structural damage. It is in one piece already, just softened.

So, besides cost, given what I want to fix, why would I *not* use a layer or two of carbon there instead of what I suppose would need to be 3-4 layers of fiberglass to get similar stiffness?. I'm not that concerned about weight [saving] since the area is small...

Last one - can/should I use acetone to clean the area before applying epoxy? Got a can sitting in the basement from some other project ...


You can “bag” the repair with cling
wrap for the outside repair. I would not bother bagging for the inside repair.

When I use food wrap to bag an exterior patch, I draw the food wrap tight with pieces of tape applied to the margins. You might see some air rise out of the wet patch and collect under the food wrap. This can be gently moved to the margins of the patch, along with some excess resin.

You’re going to be using maybe 2 to 3 layers of cloth inside. I would use 6 oz glass because it’s easier to see that the layers are wet out properly. Using carbon will not contribute much additional stiffness, but it will weigh a teensy bit less. It may be harder to see the wetting out process. Personally, I would be using Kevlar inside, but it’s hard to see Kevlar wetting out.

Acetone is OK but remember, it’s flammable. And as a general rule, never sop acetone on a plastic. Moisten a cloth and wipe.

No outside repairs needed
Thanks for the thoughts. I will only be patching from the inside. All that’s needed from the outside is to re-glue the seam back to the deck and optional gel coat repair of the spider cracks.

Someone suggested 3M 5200 instead of epoxy for the seam and someone else - epoxy. Any thoughts on why one or the other?

I would use epoxy, because it is
thinner, more penetrating. Also has at least as good adhering quality as 3M. And if cloth is involved, with epoxy you can see what you’re doing. Is that possible with the 3M?

West epoxy 105/205 is one of the most versatile materials available for boat repair. Keeps a long time, penetrates cloths well, adheres to most surfaces well.