On Tue, 23 Nov 2004 22:01:12 -0500, Wayne.B
wrote:

On Wed, 24 Nov 2004 00:00:19 GMT, Short Wave Sportfishing
wrote:

AH HA!!!

See - "gliding"....

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

Yes, that light feeling of skipping across the wave tops. I know it
well, and like it as much as anyone else, BUT many heavy boats are
truly "on plane" well before that point is reached. And many heavy
boats never reach that point even though they start planing somewhere
between 13 and 20 knots.

Which brings us back to the original question in a circular sort of
way: When is a boat "on plane" ? I'd be inclined to vote for 2.5X
the theoretical hull speed. Easy enough to calculate, and sort of
intuitive. It may not be dead right for every boat but it should be
in the ball park.

I'll vote for gliding. :)

Seriously, sounds good to me.

Later,

Tom

On Tue, 23 Nov 2004 22:01:12 -0500, Wayne.B
wrote:

On Wed, 24 Nov 2004 00:00:19 GMT, Short Wave Sportfishing
wrote:

AH HA!!!

See - "gliding"....

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

Yes, that light feeling of skipping across the wave tops. I know it
well, and like it as much as anyone else, BUT many heavy boats are
truly "on plane" well before that point is reached. And many heavy
boats never reach that point even though they start planing somewhere
between 13 and 20 knots.

Which brings us back to the original question in a circular sort of
way: When is a boat "on plane" ? I'd be inclined to vote for 2.5X
the theoretical hull speed. Easy enough to calculate, and sort of
intuitive. It may not be dead right for every boat but it should be
in the ball park.

I just thought of something - would this be true of displacement
hulls?

Later,

Tom

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

On Wed, 24 Nov 2004 11:26:29 GMT, Short Wave Sportfishing
wrote:

Which brings us back to the original question in a circular sort of
way: When is a boat "on plane" ? I'd be inclined to vote for 2.5X
the theoretical hull speed. Easy enough to calculate, and sort of
intuitive. It may not be dead right for every boat but it should be
in the ball park.

I just thought of something - would this be true of displacement
hulls?
==========================================

A lot of so called displacement hulls could probably plane to some
extent if you could get enough power to the water. There are many
heavy sailboats that will briefly plane if you can get them surfing
down a wave with a lot of wind in the spinnaker. I suspect there are
some hulls, tugboats come to mind, that would be hard pressed to plane
regardless of power. The hull shapes just don't have enough flatness
to them. Lack of planar areas? It's difficult to skip a round rock.

On Wed, 24 Nov 2004 11:29:02 GMT, Short Wave Sportfishing
wrote:
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.

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

I think it's all in the hull shape.

On Wed, 24 Nov 2004 10:01:32 -0500, Wayne.B
wrote:

On Wed, 24 Nov 2004 11:29:02 GMT, Short Wave Sportfishing
wrote:
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.

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

I think it's all in the hull shape.

This hull is based and identical to the 620 series Ranger bass boats.
Those have considerable bow lift. :)

Live long and prosper,

Tom