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Progressive Vee hull


By petehdgs - Posted on 23 June 2012

I had a discussion recently with Coot enthusiast about hull bottom design for the Coot Amphibian. I had suggested going to a progressive V hull like we talked about and using strakes to increase the lift. He warned be to be careful with strakes because they can be dangerous when landing in a crosswind. If the airplane is moving sideways when it touches the water, the outside edges of the strakes can dig in causing the airplane to yaw and roll violently perhaps resulting in an accident. He offered specific examples of this and suggested that I reconsider.

So I spent some time drawing bottom profiles at the step and hit on the idea of one-sided strakes. I have later come to realize that the progression of the hull would form a type of nested V design that could allow the aircraft to slide sideways somewhat during a crosswind landing before settling out and tracking straight. There is a sketch of this idea attached to this email.

Do you think the general idea is sound and that my proportions are about correct?
The upper drawing shows the inside intersection at 8" left and 8" right and the outer intersection at 9" left and 9" right.
The lower drawing shows the inside intersection at 9" left and 9" right and the outer intersection at 10" left and 10" right.

If you look at the sketch you'll notice the intersection of the nested V will have increased stress due to the nature of turning the water 25 degrees to a discharge angle of 12.5 degrees down. How should I go about re-inforcing this area to to ensure long life of the hull? I want the hull to be as light as possible, but I'd hate for it to start cracking there because I didn't build it strong enough in the first place.
I intend to build a clay model of this idea to extend the lines in 3D from the step transom to the bow. I might make two and send you one of them to look at.

Thanks for your counsel

This sounds interesting but we need to see the diagram. See the tutorial on adding photos if you need help.

 

;-) Paul

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