On Tue, 23 Nov 2004 22:10:12 -0500, Wayne.B
wrote:

On 23 Nov 2004 15:31:50 -0800, (Big Daddy) wrote:
Hey, one more quick one. Has anyone else noticed in some of the
magazine boat reviews where they show the rpm, boat angle, and mpg
that in some tests, the best mpg that they measure is when the boat
angle is at it's steepest, like 5 degrees? That seems odd to me.
That, I would think is the very worst angle for good gas mileage and
yet they show it as the best.

============================

Depends on the boat and how it is loaded. 5 degrees is not all that
much but it is probably enough to get the forward third of the boat
out of the water and thus reducing hull friction. If you increase the
angle too much the stern squats and digs in, creating a different kind
of drag.

I would also expect that a certain amount of bow rise helps the boat
climb onto the surface of the water just as a small angle of attack
helps an airplane climb through the air. In each case the downward
flow deflection creates an upward lifting force.

My Ranger has zero bow lift. There is a slight tilt when power is
applied, but for the bow to actually "lift" is damn near impossible -
I know, I've tried raising and lowering the motor, different tilt
angles. As power is applied, the boat just lifts itself out of the
water sans bow lift.

I've never been able to figure that out. Most bay boats in my
experience have similar bow lift to bass boats - this one doesn't.

Later,

Tom