Repairing leaking bulkheads

October 3, 2006

This is a collection of research on leaking bulkheads which i will update until the job is done!

This question and advice was posted here (a forum in the US).

Question : Can someone guide me to instructions for repairing a leaky bulkhead in my fiberglass/kevlar kayak? A little water gets into the dayhatch (not through the cover, but through the bulkhead behind the seat). What’s the best stuff to buy at the marine store to reseal it? Thanks!

Suggestion 1: I’d suggest first contacting the manufacture to see what they recommend. Failing that I think I’d try to patch it with epoxy if it is a small gap, or epoxy and fiberglass tape if the seam is starting to give way… Woody

Suggestion 2: Go down to your local automotive supply store and buy a small, self applicating tube of two component urethane seam sealer. Clean the area, scuff sand the fiberglass with 100 grit paper and apply a bead of sealer. I recommend a urethane because it is easy to use, cures quickly (about 20 minutes) and is also a structural adhesive and will not come off. Ian

This was for a fibreglass boat, mine is plastic. This was posted here at Eddyline Kayaks about maintenance and repair of leaks:

Remember, the bulkheads are vented with a tiny hole in the center. [Didn’t know this].

Since a leak rarely means a structural problem, simple sealants like clear silicone are quite adequate for stopping them. Once you have identified a leak, press a very small amount of sealant into the area with a finger or rag. Be sure to wipe off the excess, you just want to seal the pore that is allowing water to pass.

Recommended sealants: 3M 5200 Fast Cure or any other marine grade polyurethane sealant. Silicone may be used, however, once you use silicone in an area, nothing else will stick to it in the future. This may cause problems if you need to do further repairs.

And for here this gem (actually about sealing hatches but hey):

Glass fibrer resin will NOT adhere long-term to plastic where there is any flexing… If resin/glass is your only sealant, your hatches will eventually leak. This also applies to Q cells which is a glass fibre filler and various commercially made bonding agents which set HARD when cured. A flexible sealant is needed in CONJUNCTION with glass fibre and resin.

The very best sealant I have seen is Sikaflex. Nothing else even comes close. This sealant is a purpose designed marine sealant/adhesive for below-the-waterline use. You can get it in black or white, tube or cartridge. It can be a bit messy to use, clean up with turps, metho or acetone and store opened cartridge in the fridge. You can get it at Ships Chandlers and marine dealers. Resins will stick to it unlike silicone sealants. It is the best. Again,…it is the best. Do NOT use silicone sealants.

And about foam bulkheads (like mine)

…foam bulkheads often begin leaking within a few years. This is due to the fact that the foam shrinks with age and pulls away from the adhesive used to seal the edges. These leaks are annoyingly persistent even after re-caulking…

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One Response to “Repairing leaking bulkheads”

  1. Adam Bolonsky Says:

    Hi Kayak Japan:

    I’ve got a six-part series on my blog about how to repair fiberglass boats. One of the key reasons to learn how is to be able to not only repair leaky bulkheads but to move them to increase cargo volume and reduce cockit volume.

    Here’s my blog’s address:
    paddlingtravelers.blogspot.com


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