Small Boat Design

Discussions around designing small boats including kayaks and canoes.

Re: Initial Stability
In Response To: Initial Stability ()

Hello Dave,

Okay, I thought you were designing a kayak, but yes, if it's a paddleboard then the pivot point of the paddle is higher and therefore has more heeling moment... or effect on the heeling moment... I believe that's the right way to say it. You get my drift. Anyway, it's also harder to add flare to a SUP simply due to the height of the sides (rails) being so low. Sounds like you're on the right track.

Also going back to your original question, you asked about the vee having effect on the stability. One thing to consider is the deeper the vee, the more volume you are putting lower below the waterline, as you mentined in your follow-up post. For a SUP what I did was to do a very shallow vee so that it rests level, but it still has a gradual stability curve. If you take the example of a Baidarka- often a Baidarka will float heeled over until you get in and add ballast (your own weight). The vee hull has more buoyancy low than it has resistance so the keel wants to float up. Once you get weight in it there's enough to keep the keel down. With a SUP this becomes a difficult situation when you try to get back on the board in open water. It is one of the concerns about my design. I built some test models that did really well so I don't think it's going to float too heeled but we will see once it's finished. Actually it just needs to be sanded, final coat, and the deck pad put on.

I think we are kind of doing the same thing here- trying to design a SUP more around the kayak hull shape, but keep the stability needed for standing on top of it while still having a clean entry and exit. Each of those factors are enemies of the other! :-)