: Hi Bill - I just stumbled across your thread - I had the same idea about a
: year ago. I've been mulling it since, and over the Christmas break I built
: a 1/4 scale model of a preliminary design for a catamaran kayak. The hulls
: are long and narrow, 16'4" by 6", max draft will be about
: 8-9", overall beam I'm trying to keep to 24". It's basically a
: skinny hull cut in half down the middle. Seating will be from a hung seat
: above the waterline, so I guess it will technically be a SOT.

: The boat is designed as a swimmer escort and rescue kayak - the major design
: goal is to be able to transport a patient on a hammock behind the paddler
: above the waterline to reduce hypothermia. The extra load will require a
: sliding seat for the paddler to trim the boat. It is also meant to act as
: a platform for long distance swimmers to eat, drink, rest, whatever.
: Ideally, it will be stable enough that the paddler can turn around and
: move around to aid the patient/swimmer. I think it will work well as a
: chase boat at paddle events as well. I'd also like it to be fast, able to
: function on the open ocean, etc. etc.

: A plastic wrap test on the model went pretty well (it appeared to have very
: low drag), and I am currently gearing up to make a prototype starting in
: the next week or two. It will be a big experiment, as the model didn't
: give a lot of info about paddling dynamics, and there's a lot to figure
: out. I've thought about doing some software modeling, but that won't help
: with the dynamics either, so I am going to just forge ahead and make a
: boat. I plan to do the first prototype as a Yost-style SOF. The hulls will
: be nearly flat on the inside as suggested by you and Mike - they're so
: narrow they actually look more like airplane wings on edge. But hey, my
: Dad was a wind-tunnel model-maker at Boeing and my brothers and I grew up
: making balsa airplanes, not boats, so I guess that has something to do
: with it. The biggest challenges I see at this point is hull torsional
: stiffness and weight.

: I have a detailed photo sequence of the model construction. I've been meaning
: to put it all together to share on this site - I'm glad you asked your
: question as it gave me the impetus to start. The link below has just a few
: so far.

: I wanted to call the boat the "Sea Sled" but the name was taken by
: a fast speedboat catamaran from the early 20th century (now defunct,
: though). I'm toying with the name "Cutter", which has a nice
: double meaning - USCG Cutters are used for rescue, of course, but
: "cutter" is also a term for a light, fast sleigh pulled by a
: single horse, which I think is appropriate.

: Well, I guess this is maybe more info than necessary, but I've been thinking
: about this for a long time. Let me know what you think - better photos
: later, Carl

Oh yeah, couple of construction things. If you use an epoxy filet at the intersection of the stringers and frames you can eliminate the diagonals, makes the hull extremely rigid and still very light. Did that one my single hull Yost kayak and it's as rigid (sans skin) as any glass boat.

I was going to make the insides of the hulls completely flat, the two hulls are so close together that you'll end up with standing waves that cause drag if there is much if any curve in that area of the individual hulls. I think you'll still have that problem at a certain speed, only time will tell how fast that speed is. If it's fast enough won't matter.

I was going to make the insides of the two hulls from a piece of think plywood, with no curve (or very little) in the hull the fabric cover won't have anything to be stretched over to keep it taunt. Still needs covered in fabric to keep everything watertight, but then it can be glued to that internal ply skin to keep it in place.

I was going to use only 3 fairly large cross members to hold the hulls together. With your sliding seat you'll need more, I was going to put them in front of the foot support, behind the seat and under the raised front of the seat. I've got some clear sitka spruce that's quite strong for it's weight that I'd use for that. Perhaps a light box beam would work there to save a little weight (aka airplane spars).

Bill H.