Here's my Jocassee with its factory sprayskirt. Looks like a kayak, doesn't it? Except that even after several home-brewed improvements, the skirt leaked, was hard to fit into place even on shore, and might have drowned me if I had ever had to make a wet exit at sea. $150 down the tube!
I pondered and schemed and brainstormed for several months, trying to decide how to make a deck for my kayak. Fiberglass is one approach, but I had no experience with it. Aluminum seemed like a good idea, but I didn't have access to a big sheet of aluminum to experiment with. Plywood has the advantages of being readily available, inexpensive and easy to work with, so I settled on 1/8" plywood. I spent considerable time thinking about how to make a deck that would preserve the option of switching between single-paddler and two-paddler configurations. It soon became clear that two complete decks would be required. The decks would have to be attached to the kayak by screws through the deck into nuts bonded to the underside of the lip of the cockpit rim.
The plywood was trimmed to the outline of the cockpit area. This isn't as easy as it sounds -- unbraced polyethelene is flexible. The kayak's shape varies depending upon how it is supported and what its temperature is. It would probably be best to match the deck to the kayak while the kayak is floating in water, but that presented practical problems (bathtub too small). I made a posterboard template of the cockpit area shortly after bringing the kayak back from paddling it, and trimmed and retrimmed it several times until I was confident it matched satisfactorily. Then I used it to cut out a deck from a sheet of polystyrene foam insulation for final matching and fitting. I used the polystyrene deck to cut out the plywood deck, and then fitted and trimmed some more. The cockpit openings were positioned by careful, repeated measurements from the seat positions in the kayak and the openings in the fabric sprayskirt. Extra care and double-checking are called for, since you can't un-cut an opening once it has been cut out. On the singles deck, fore and aft openings are also needed for access to the flotation bags, storage space, and foot peg adjustments, so I made holes for hatches -- a large one aft (to double for carrying a small child or dog) and a smaller one for'rd mainly for access.
After cutting and trimming the plywood to shape, and cutting out the cockpit and hatch openings, I clamped it onto the kayak and drilled 26 matching holes through the deck and the cockpit lip. It was difficult to find anything that would bond a nut to polyethelene. After some experimentation, I found that "J&B Qwik Weld" could be molded into a block holding a T-nut against the underside of the lip. If the polyethelene is roughed up, the Qwik Weld bonds pretty reliably. It only has to hold the nut in place when the deck is unattached, since the screw holds everything tightly together when the deck is installed.
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Clean the surface of the plastic thoroughly, and rough it up to give the adhesive something to hold onto. I sanded it and then scored it in a cross-hatched pattern with a sharp knife. With the the deck screwed down, work up a solid blob/block of the Qwik Weld around, behind, and under the T-nut. The stuff hardens quickly, so you can only do one at a time. Let it cure a day or so. The only way it can come out is when the deck is not installed. If that happens (only one of mine has ever come loose) the whole block can be glued back into place with Hydrogrip. I used 10x32 screws and nuts. If I were to do it again, I would use 10x24 instead because the finer threads are a nuisance to use in the field. |
Above, the Jocassee in drydock, with the singles deck fitted into place. The cockpit coaming is lying upside down on the steps, awaiting installation.
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My cockpits and cockpit coamings were modeled on the cockpit of my old Prijon T-Canyon since I find that a comfortable size and it allows me to use the same spray skirts on both kayaks. I suppose if you elected to make smaller, more round cockpits, you might be able to put three cockpit openings in one deck. I chose to have roomier, more comfortable cockpits instead. Coamings were made from stacked pieces of plywood, glued together and trimmed, rasped, and sanded smooth. I used three to four pieces of plywood, depending upon the thickness of the available pieces. The quality of the plywood is more important than how many pieces it takes, since wherever I used rough plywood I wound up spending lots of time filling and smoothing voids and gaps. I used a waterproof wood glue to glue the first coamings together and to the deck. I was rewarded by having the coaming start to come loose from the deck several days later. Subsequently, I switched to using "Liquid Nails for Heavy Duty Construction", and haven't had anything come loose since. Glue your coaming pieces together and to the deck with the deck fully screwed down on the kayak, so as to match the curvatures the deck assumes when it's in place. |
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The singles deck with the cockpit coaming clamped in place, drying. Be sure you have LOTS of clamps.
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Below is a photo of the doubles deck (which I actually made first). It's obvious why two decks are required if you're going to have decent-sized cockpits. Notice in the background how the standard seatbacks stick up and back, robbing you of a lot of useful room in the cockpit opening. I have since removed the plastic seatbacks and replaced them with padded backbands, making it possible to sit three or four inches farther back in the cockpit. This allows more room to move or to position the seat.
The undersides of both decks are reinforced: the singles deck has an extra layer of plywood epoxied to the underside from the rear portion of the cockpit back to the end. The doubles deck has lateral and transverse 1" braces running from the fore part of the after cockpit up to the rear of the for'rd cockpit, to reduce flexing. Additionally, the rearmost edge of each cockpit coaming is support by a vertical pillar of 2.25" (58 mm) diameter PVC tubing so as to support a paddler's weight when entering and leaving. On the singles deck, the drink holder of the unused rear seat forms a perfect socket for the PVC pillar. For the doubles deck, the bottoms of the pillars are cut to fit over the longitudinal tubular brace that runs the length of the cockpit.
I "painted" the decks with two coats of Bondo Marine Epoxy (simply because that was the only brand locally available), with the intention of adding a top coat of paint or varnish for appearance and UV protection. Bondo Marine Expoxy is thick, rather like molasses, and doesn't take well to thinners. It also retains a certain degree of flexibility/softness. As I learned from a factory rep, it was designed mostly for use as an adhesive and a protective coating, so it isn't intended to be thinned and they don't recommend it. I had trouble finding a spray coating that offered UV protection (when you call the manufacturers, they won't say their paints stop UV), so after a year neither deck has been painted and they still look fine in just the double coat of epoxy.
So here's the Jocassee after refit:
The improvised hatches work well, although they make the kayak look a little bit like a battlecruiser awaiting its turrets and superstructure. It did not prove necessary to use a gasket or caulking under the deck. The black moulding that covers the edge of the cockpit opening seals nicely when the deck is firmly screwed down on it. Even when the kayak is heeled over with the edge of the deck submerged, no water comes in.
