GREAT Article on Kayak Design

Came across this while fooling around on the internet. Covers length, wetted surface, beam, "wet kayak", rocker, etc.


http://www.ftlauderdaleyakfishingclub.org/yakdesign101.html

That is very old. 10-13 years my guess. But has some useful info.

I enjoyed the article.  The seat height got me thinking about the new AI versus the old AI.  Is that new Hobie seat, when lowered all the way, going to put my butt at the same distance from the water line as the old AI?  If not, I might just want to snap up a retired AI.

I enjoyed the article.  The seat height got me thinking about the new AI versus the old AI.  Is that new Hobie seat, when lowered all the way, going to put my butt at the same distance from the water line as the old AI?  If not, I might just want to snap up a retired AI.

My understanding is that they made the seat base lower in order to compensate for the increased seat height. So it's at the same height. Don't quote me on that though!

Now that I think about it a little more...why worry?  Those Amas will make up for any loss in stability seat height might bring?

It states the assumption that a boat with a longer waterline will always be faster and this is not true as it ignores the shape of the hull and the amount of wetted surface and other factors. There is the old calculation that the maximum speed for a boat that has a displacement hull is 1.34 time the square root of the length of the waterline.

But this only works for two boats with identical hulls and in terms of the maximum speed when there is no limit on the power applied to moving the boat using sails or a motor driving a propeller. That is not the same as the amount of power provide by a person with a paddle or a pedal drive where the power output is limited.

Anyone who thinks a 12'1" long Hobie Outback or a 13'4" Malibu Two XL at is going to be faster than a 11'6" Hobie Revo 11 is going to disappointed in actual use of the longer and supposedly therefore faster boats.

Other factors that are ignore in the longer is better is the added windage on the bow of the boat that needs to be countered when there is a strong cross wind, and the degree to which a boat with a given load sinks down into the water. The latter is why catamarans with a light load are generally faster than a mono hull but where this ceases to be true with a heavy load where the twin hulls are much deeper in the water. The same applies to putting a 200 lb. person into a kayak where the amount of reserve buoyancy affects the wetted surface and drag from the water.