Cockpits on low volume kayaks
Tuesday, November 15, 2011, 15 comments
The discussion on Tahe Greenland and its cockpit leaves a few questions. Here are a couple of thoughts (that perhaps also triggers an interesting discussion). The basis is my experience from Black pearl and may answer quite a lot of questions from builders on seating position and cockpit configuration.
I like small cockpit openings (ocean cockpits) and the reasons are discussed elsewhere, so over to the potential problems. Many of those trying the Tahe Greenland (first series) asked for a larger cockpit hole to make it easier to slide in and out of the kayak and to improve the comfort.
Hole size
In the picture below I want to show that it is not the size that determines the ease of access in a low volume kayak.
Since the foredeck normally slopes down forward, a larger hole means a lower front edge, and thus no immediate advantages – unless the hole is so large that you sit on the seat before your kneecaps reach the rim: but then it is not a small cockpit anymore and most of the benefits are gone.
Simply enlarging to make it easier to slide in will probably be a disappointment!
The important thing is the difference in height between fore and aft deck. Too tight? Raise the fore deck or lower the aft deck. (This is perhaps the time to admit that when building my BP, I made a cockpit dummy to try out the exact configuration. Superb in theory but for some reason that I still do not understand bad in execution – my knee caps did not get past the rim in the finished kayak! So I had to make two cuts through the rim and into the fore deck, some 50 cm long, and glue strip wedges into those to raise the fore deck approx 15 mm. A lot of irritation, some extra work, but it turned out very nicely).
This is what it looks like when sitting in the Pearl – a relaxed and comfortable position, with perfect kayak control.
Some builders want to recess the rim. I advice against that, since it will be very tight over the knees and the thighs.
Recessed rim
(Translation of captions: "Recessed rim means that the aft edge is below the sheer", "min height to get into the kayak" and "...means that the deck first must be raised")
I claimed in the Tahe post that recessing the rim on low volume kayaks is a mistake, and got some well-motivated objections in the comments. These were my arguments:
- The low deck on the Pearl is designed with the minimum height to get into the cockpit, with very little margin. That means that the deck first must be raised to provde room for the recess, and then the advantage of recessing is gone. On a higher deck (fx on Njord) the recess may create a comfortable angle for the thigh support though.
- A recessed rim on a flat aft deck creates a gutter, where water pools and might get into the cockpit when the tuiliq or spraydeck is removed (if you don’t tilt the kayak first, use a sponge or build some kind of drain). The problem can be solved in a number of ways: create an s-shaped rim (side view) so that the aft part is almost horizontal – but that makes it harder to attach the tuiliq hem and may compromise the seal. Or you can straighten out the aft part of the rim – but then the tuiliq or spraydeck will be leaking there, and back-leaning will be uncomfortable. (Tahe is, for Greenland, using both methods)
A common reason to recess is to make it easier and more comfortable to lean back. But as shown in the picture moving the seat 2 cm forward can do that. It produces exactly the same effect as lowering the rim by the same measurement – but is much simpler.
The rim profile
In another post I have suggested straighten out the rim profile (side view). A fairly straight profile seals better and makes it easier to attach the spraydeck. I simple way to achieve this is to attach a dummy-rim (a piece of particle board or plywood) on the molds before stripping the deck. The dummy will guide the strips when stapling.
The seat
Black Pearl is designed for a very low seat – lowest points just a couple of millimeters above the bottom. One way to achieve this is to start with 10 mm a foam sheet, the underside shaped to fit the bottom profile of the hull, and tho top dished out to fit the butt. For comfort and look, glue a piece of sleeping pad on top. A higher seat compromises the initial stability and may unnecessarily make the cockpit too tight (my problems with the first series Tahe Greenland turned out to be a mistake at the factory: using a too high seat).
