How to Seal a Folding Kayak's Deck Seam

We were one of the earliest customers to buy a Cooper from Folbot, the Carolina based manufacturer of durable folding kayaks, and a wonderful boat it's turned out to be: sleek, quick and easy to assemble.
Labour intensive jobs drive costs upwards so Folbot has a philosophy to keep the cost of the kayaks low by not doing those tasks that the consumer can easily do at home. Some don't like this view and want to buy a completed boat, but being a budget-minded, DIY-sort-of-guy I like the idea.
Folding kayaks, being skin-on-frame boats, have a tough hypalon hull stitched to a water-proof canvas deck and it's this seam, running the length of the boat on both sides, that can allow ingress of water unless sealed. The sealing is not a difficult task, just time consuming, so Folbot doesn't do it in-factory but ships some seam sealer with the boat.

So how do you go about sealing your nice new Cooper without covering yourself, the kayak, the kids and the neighbour's dog in gooey sealant? It's quite easy, all you need is the seam-sealer, some masking tape, patience and a six-pack of your favourite malt and barley (optional to some but not to me.)

1. Firstly, assemble the Cooper and inflate the sponsons tightly. The seam runs along the sponsons and inflating them keeps the seam open as well as giving you a taught surface to work on. Open seams also allow better penetration of the sealant into the seam gap.

2. Place the kayak at a comfortable working height, I put mine on some cheapo Ikea saw-horses. Having it on the floor is not the end-of-the-world but stooping makes the work harder.

3. Now you're free to open the first victim in the six-pack, but take it easy as you need a steady hand for the next few tasks. I recommend intermittent sips, rather than a good chug, as the way to go.


4. Before applying the tape you need to clean the seam area properly to remove any grease, salt, moisture and so on. My solvent of choice is usually acetone, but to be honest I can't quite remember what I used for this job, most probably white spirits from my local hardware store. I leave the choice up to you, but be careful and first test whatever solvent you use on a small, out-of-the-way patch of BOTH the deck and the hull. Acetone is great but can dissolve things, I'll tell you about the underwater camera housing some other time, so white spirits is probably safer. After testing, and assuming no gaping holes have been eaten through the fabric, have another sip to steady the nerves then clean all along the seam as shown in the picture above, concentrating on the hull.

5. While waiting for the cleaning solvent to evaporate and dry completely I recommend taking a few sips. No, not the solvent ... from whichever victim you're on by now. But remember, the next step needs the really steady hand, so take it easy.

6. Now, lay two layers of masking tape on either side of the seam from stem to stern. As you can see in the picture below, I've laid the hull-side tape quite close to the seam, there's just a narrow black band showing, while the deck-side tape is just off the stitching. Keeping the hull gap to a minimum makes the sealing job less noticeable when you remove the tape. Keeping the two lengths of tape as parallel as possible, take some time to firmly press the tape down, I run a thumb nail along the edges, otherwise the sealant can creep in under the tape leaving an unsightly ragged edge rather than a clean line. You're almost there, so have a few well deserved slugs, mmmh!


7. Now comes the trickiest part: applying the sealant. The trick in applying the sealant is to keep an even thickness all the way, the best way of doing this is to point the tube in the direction of travel, not away. So, start at one end, stern or bow it's up to you, point the mouth of the tube at the other end and gently squeeze the end of the tube until some sealant comes out, now keep pushing the tube as steadily as possible along the seam while squeezing lightly all the time. The bottom lip of the tube should help spread the goo evenly without breaking it up into gobs, which happens when you pull the tube. Make sure the sealant squishes into the gap of the seam but don't make the layer too thick, it only needs to seal the gap and the stitching, not add structural stability! If you get it all perfectly even, please let me know how you did it ... even with the best will in the world I still had to smooth things over with a wet-finger. I also ran a bead of sealant around the deck-ring fastenings, just in case.

8. Don't wait too long to remove the tape, you want it set but not cured. Depending on your malt/barley consumption rate I'd say give it a two-victim break and then remove the tape. There is also a trick to removing the tape to ensure that you don't lift the sealant edge with it. Lift the end of the tape just enough to get a good grip, then pull the tape back along itself, not upwards, the section being pulled loose should be virtually folded over. Doing this steadily, without yanking it, should leave a clean edge. If you're brainier than I am you may think of leaving a bit of an overlap at the end to make lifting the tape easier.

And your done! And not a moment too soon seeing as the six-pack has only one left. Leave the Cooper as it is to allow the sealant to cure, overnight should be fine, but seeing as our kayak was destined for use in the ocean I left mine for 24 hours. This was probably overkill but we've had no leaks after 4 years.

And now you can let your lovely wife paddle her own kayak out to the Dhows.

Update (19-Jan-2010): I received a email from Dave AvRutick, Folbot head-honcho, in which he clarified Folbot's position on in-factory seam sealing of the Cooper "we do not apply the seam sealer as we do not think it is necessary for 'average' use -- not as a cost saving measure. Depending on the customer's paddling, it may be something they choose to do -- it is nothing that is mandatory."
Sounds fair enough to me. Thanks for the input, Dave.


Craig
sunburnt ... and in need of a shave