own design or plans?

[tom28571]

I'll explain what I think is going on with the warped bottom. At low speed it adds more lift aft than the monohedron because the downward turn of the chine relative to the rest of the aft bottom shape is a bit like trim tabs and aids in quick planing. At high speed (all speed really) the warp causes a differential downward force on each side across the transom. No problem as long as the water is calm and nobody causes the boat to heel. But that is seldom the case and the boat encounters wave patterns that affect the bottom differently. So any differential in the down force of one side of the transom to the other becomes a steering force. Try heeling your boat from one side to the other to prove this to yourself. Thus the boat develops a yaw instability which shows up as an oscillation about a central vertical axis. I have seen that happen in one of my test models such that the model actually oscillated so badly it flipped around backwards and destroyed my test rig.

I think this happens to all boats to some degree but is much more pronounced on the aft warped bottom. All (most all?) boats get unstable at very high speed and it is a matter of degree. In my opinion, no high speed boat should have a warped aft bottom shape.

For my own interpretation of the forces of planing, see my website: http://bluejacketboats.com/planing_boat_theory1.htm

Edited to add: Here is an extreme example of the steering-yawing problem from meeting off angle waves at high speed. Notice what happens to the boat just before it becomes airborne. http://www.youtube.com/watch?v=K9ZC4...ature=youtu.be