catamaran kayak

I am thinking of designing and building a catamaran style Kayak.
I will be using it for fishing, so the two features I am looking for are stability, and ease of paddling.

The current fishing based (rotomoulded plastic) Kayaks are either stable, and a pig to paddle or, unstable and easier to paddle.

I am looking at 4.25m length, beam .7m, and displacement of 120kg (me plus 40kg payload)
I am hoping the cat style will give me 2 narrow hulls which will be easy to paddle, and stable when fighting the big fish.

Would love to get any feedback, suggestions or comments on this idea
Thansk

 

OK, So, right off the bat you're going to achieve the huge improvement in stability by going to the twin kayak cat form, no matter what kind of kayak hulls you wind-up with, so let's put that away for now.

Ease of paddling for a boat of this type will come from having the skinniest hulls possible for the desired displacement that are shaped for best performance at human powered paddling speeds. If you have any future desire to see this boat with a sail rig, then I suggest that the hulls be shaped differently than they would for a pure paddled design.

Likewise, if you have any future desire to use one of the kayaks for a solo boat, this will also require a rethink of best hullform, but for different reasons.

Sitting in the hulls for paddling (using a single blade canoe paddle) with a fairly simple, slatted bridgedeck surface for fishing will give you a light boat that can be pretty easily driven. This boat will have the stability to allow you stand on the slatted deck to fish in style and will easily drain away and wave action.

Yeah, that's how it goes in the boat design world. There is a way, however, to get that cool paddling efficiency going and also get a nicely enhanced sense of stability once you get to the fishing grounds.

A decently slender kayak hull could be equipped with a folding set of amas mounted aft of the cockpit. When you paddle they are retracted up and away from the water, and when you want to sit stable and fish, down they fold to give you a nice wide base for stability. This type of design solution lets you live a bit in both worlds without the added wetted surface of a second hull that is in the water all the time.

If your plans are to have a second person along for the fishing trip, then the cat makes sense, as does a double kayak with the folding ama setup.

If there's no need to pull one of the kayaks out of the cat form to paddle solo, then you don't really need to have anything like a typical kayak hull. You could go with a design that optimizes the potential of the human paddler with an emphasis on minimum wetted surface aimed at the load-carrying target. You'll leave out the solo hull stability function and split the displacement needs between the two hulls.

Just for fun, I did a couple of boats awhile ago that are something along the lines being tossed around here. One of them is very specifically designed to be a fishing machine with some cool features. Tap this link and see if there's anything in this approach that generates some thought for you.

http://www.lunadadesign.com/nagare-21-dual-mirage-drive.html

Both of these boats can be equipped with folding amas, as mentioned above, though the drag the amas may create is minimal, even if left in the down position.

 

design ideas

I was thinking of having two hulls each with a beam of approx 150mm, and sitting on a lightweight platform between the hulls.
The current rotomoulded kayaks are 4m long and upto 750mm wide. This creates a lot of surface area drag.
While the cat would have greater drag than a racing kayak, it should have significantly less than the current fishing kayaks.

Other options would a a trimaran/stablised mono, or an outrigger canoe.

I want sonethingthat is simple and lightweight.