Prop Shaft

[gn7]

I've always had a hard time understanding why this is true. I know its true, but I just cant wrap my head around why its true when a prop is fully submerged.

I think my little brain came up with a theory. Lets see if I'm on the right track here. It has to do with the props angle (shaft angle), right ? Sense the prop is angled under the hull, lets say 8 deg. And the hull is angled bow up slightly, lets say a few deg. The prop is running through the water at maybe 10 deg. Now think of the angle of the props ears (pitch) compared to its true direction of travel through the water, when both ears are straight out to the sides. The ear that's on the downward travel would have a more aggressive (higher pitch) compared to its true direction of travel through the water, creating lift, right ?

Now as far as the paddle wheel effect, ears having more bite when there down compared to up (fully submerged). They should have the same angle/pitch to direction of travel at that point. So could it be a rake issue ? The upper ear would be raked back more than the lower ear at that point (again compared to true direction of travel). Or is it just disruption of water to the upper ear by the hardware ? Maybe a combination of both ?

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, with the top ear 1" below the surface, and spin it 10,000 RPM and tell me how much water flies in the air. That water creates some lift, 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.