: Below is a picture of Sea Sled 1, my skin-on-frame catamaran kayak prototype.
: I tested it on Wednesday at the Maritime College waterfront which is on
: the East River in the Bronx. That's our cadet training ship in the
: background.

: The boat is designed as a swimmer escort and rescue boat. The idea is that a
: swimmer or rescuee can rest between the hulls in the stern with their arms
: over the aft decks. For the rescue capability I will be adding a hammock
: of some sort between the hulls to allow getting a person up out of the
: water to slow hypothermia, if necessary. To allow for the extra weight of
: a passenger, the seat-footboard assembly will slide to allow for
: re-trimming the boat on the water.

: Boat specs: hulls 16'6" long, max beam ~6", max depth ~15",
: hull spacing 16", max overall beam about 28", max beam at
: paddling location ~25". Weight about 50 pounds (estimated). Initial
: design was done with Kayak Foundry - thanks to Ross for the package.

: The design is partly an engineering exercise, and I hope to get some of my
: students to work on improving the design and coming up with further
: adaptations. I'm not sure that there's actually a market for a rescue
: boat, but I think it will be a good perimeter safety boat for beaches and
: long distance swims. Due to its stability it would make an excellent
: fishing or diving platform. I'm hoping to exploit the extreme narrowness
: of the hulls so it will be fast - I could see it as a fun open-water
: racing boat if the drag can be lowered enough.

: The plastic wrap kept water out for an hour or so, and gave me (in the hat)
: and a student a chance to run it around our enclosed harbor quite a bit.
: Here's the major results: 1. It is ridiculously stable - I could stand up
: in the seat without trouble. If you sit side saddle and hang your legs
: over the outside, it lists about 20 degrees and stops. It took a major
: effort to capsize - righting it was difficult as well, but doable by one
: person. Leaning the boat is none too easy.

: 2. It does not like to change direction at all, but once it gets going the
: glide is quite significant. It was physically difficult to turn, which
: makes sense given the hull geometry. I could close my eyes and paddle
: hard, open my eyes and still be pointing at the same target. I am
: designing a rudder now. A couple of people have suggested a rudder in the
: bow to keep the aft rescue space clear, which sounds worth considering.

: 3. Although the boat twists a little around the crossbraces when being
: handled out of the water, in the water I didn't notice any relative motion
: between the hulls, which I find surprising, although conditions were
: benign. I could save some weight by downsizing the crossbraces and
: connecting hardware.

: 4. Drag was high, although the major portion appears to have been caused by
: major wrinkling of the plastic all over the hulls. It's true that skin
: friction will be high because of the extra wetted surface on the insides
: of the hulls. The test was promising enough to go ahead and put on a
: nylon/goop skin to see how much drag is eliminated. Skinning will have to
: wait for the rudder design.

: 5. Hull wake interactions become noticeable at about 4 knots - the surface of
: the water between the hulls developed a standing wave pattern. I need a
: waterproof camera to get some views of this once the new skin is on.

: 6. Although the seat felt high, it was not as high as the SOT that we used as
: a chase boat. The cat hulls did not interfere with the paddle stroke,
: which I was worried about. A high paddling angle was doable. Best results
: were had with a 230cm Euro paddle with a big blade area; my GP felt pretty
: useless, and my Exception AT with a smallish blade felt underpowered. That
: may be because of the high drag, the new skin will tell. It should like a
: wing paddle - I have one, but am not adept yet, so that will have to wait.
: The seating was very comfortable and I will go ahead with a sliding
: version with a fiberglass seat and footboard with a gas pedal rudder
: control system.

: OK, I wrote too much - I'm pretty excited that it worked at all. I don't know
: that this is really a kayak - if nothing else, it is technically a sit on
: top. I'm calling it the Sea Sled, which is maybe a good term for this type
: of paddleable catamaran in general. Anyway, any comments or bright ideas
: are welcome. Cheers, Carl.

Hi Carl,

Congrats

The standing wave pattern between the hulls might be partially because of the skin's relative roughness, but I suspected that would happen. Yes, very high wetted surface compared to a conventional kayak, of course larger cats also suffer from this and are quite a bit faster than monohulls.

I'm kinda surprised, I would have thought from the pictures that your boat was much wider, only 6" wider than mine, almost entirely in the hull spacing.

Sounds like mine may actually float afterall . We'll see in the spring.

Bill H.