More properly called a "surface piercing prop". Common in the racing world.
Does allow the boat to go faster. Seems like that would improve "mileage"
as well but don't know.

"Richard Casady" wrote in message
...
On Wed, 20 Aug 2008 02:15:03 GMT, Short Wave Sportfishing
wrote:

It's an interesting design, but I'm confused about the tunnel system.
Looking at the drawing, it would appear that the prop sits half way
out of the water.

Than can't be very efficient.

Of course it can. Ever hear of an Arneson Drive. Only half the seven
blade prop is in the water. No drag from shaft, strut, prop hub.

Casady

On Wed, 20 Aug 2008 10:52:37 -0400, "jamesgangnc"
wrote:

More properly called a "surface piercing prop". Common in the racing world.
Does allow the boat to go faster. Seems like that would improve "mileage"
as well but don't know.

"Richard Casady" wrote in message
.. .
On Wed, 20 Aug 2008 02:15:03 GMT, Short Wave Sportfishing
wrote:

It's an interesting design, but I'm confused about the tunnel system.
Looking at the drawing, it would appear that the prop sits half way
out of the water.

Than can't be very efficient.

Of course it can. Ever hear of an Arneson Drive. Only half the seven
blade prop is in the water. No drag from shaft, strut, prop hub.

Casady


Must be some kind of tradeoff to correct the directional draw of the
prop, no?

On Wed, 20 Aug 2008 12:54:01 GMT, (Richard
Casady) wrote:

On Wed, 20 Aug 2008 02:15:03 GMT, Short Wave Sportfishing
wrote:

It's an interesting design, but I'm confused about the tunnel system.
Looking at the drawing, it would appear that the prop sits half way
out of the water.

Than can't be very efficient.

Of course it can. Ever hear of an Arneson Drive. Only half the seven
blade prop is in the water. No drag from shaft, strut, prop hub.

I am aware of them, but I've never seen one on a small boat - say
under 24 feet. I know they claim to be 25% more efficient than other
drive systems - I couldn't say. I've never seen an Arneson Drive
system on any boat smaller than 40 foot.

It's a different technology anyway - their props are designed to match
a specific drive system while most props are designed for a different
application. As in you probably couldn't use a Arneson prop on a
standard outboard, but I could, if necessary, use a Merc prop on my
Evinrude.

My original point was that a standard prop operating half in half out
of the water would be a very inefficient use and application of power.

Specialized props and drives are a different animal.

On Wed, 20 Aug 2008 03:24:49 -0400, "Eisboch"
wrote:


"Short Wave Sportfishing" wrote in message
.. .

On Tue, 19 Aug 2008 20:11:58 -0500, Vic Smith
wrote:


This "tunnel boat" is real interesting

Penn Yann had a very similar design only with a rounded chine rather
than a square chine. They worked well enough I guess, but it never
really caught on.

It's an interesting design, but I'm confused about the tunnel system.
Looking at the drawing, it would appear that the prop sits half way
out of the water.

Than can't be very efficient.

Have you ever tried close quarter maneuvering in a single screw, tunnel
drive Penn Yann?

It's no wonder it never caught on.

Never did that, but my brother and I were looking at a tunnel drive
Penn Yann a few years ago as a joint venture - we had this strange
idea to use it as an all-purpose crab/lobster boat. The owner let us
take it out for a ride and I will say it was a different animal under
power.

Not something I was used to I'll say that.