Quote Originally Posted by gn7 View Post
Its more like the prop is too close to the surface. It moves the water (creating the rooster tail) as opposed to moving the prop thru the water that happens on the down side. To get anything approaching equal force off the prop would require something like this. Not unlike a Jet Ski prop or fan shroud on a car engine.

Take a prop on a 8* angle on 4 ft of water, and spin it 10,000 RPM and tell me how much water flies in the air. That water creates some but its countered by the ear trying to drive itself to the bottom of the lake. That force on the strut is countered by the upward force of the opposite side to a much greater degree.
The water thrown on the bottom of the boat does jack shit to propel the boat. It just destroys blast and cav plates.
OK, but lets picture this, same example you used, 8 deg shaft angle to the boats motion. Now lets use a prop that has an 8 deg angle on the blades. The downward moving blade will be creating no forward motion, just lift like a paddle wheel. But the upward moving blade would have a 16 deg angle and create forward motion as well as some downward thrust. Less downward thrust than the upward thrust of the paddle wheel on the downward motion side, Right ? We would end up with lots of lift and a little forward motion, Right ? So now we put the shaft at a 4 deg angle, same 8 deg blade angle, the downward moving blade will be at a 4 deg angle creating less lift but more forward motion, Right ? And the upward moving blade will be at 12 deg angle creating less forward motion than the downward moving blade that's at a 4 deg angle, Right ? The downward blade creates less lift, and the upward blade creates more downward trust, Right ? The down ward moving blade will have a much higher inch of movement per rotation (higher true pitch) than the upward moving blade. So we end up with less lift and more forward motion, Right ? Now put the shaft at 0 deg. Now both sides are creating the same forces. Same 8 deg blade angle, so same true pitch, same forward thrust, and equal up/down force. No lift, just forward motion, as long as the prop is fully submerged. So shaft angle as well as blade angle, compared to true forward motion angle will have a HUGE effect on lift, Right ? Not just how much water the prop throws in the air.

And I still think the shaft angle basically causing the upper blade to be raked back more than the lower blade (compared to true forward motion) has something to do with the "paddlewheel" effect (pushing the back of the boat one way or the other). I just cant figure it out in my head.