Shen,

You're way off about two bladed and folding. I have a single prop mono
hull and I use both a fixed Martec and at times a Martec Folding, Both
13x13. They both walk. The Folding much worst than the fixed, due the
the need of higher RPM's initially to open the blades

Jeff I don't have the answer of why you don't walk but I would suspect
it has to do with the Saildrives. Walking occurs on bare props. The
Saildrives have cavition plate and shaped housing forward and shedges
below which control the water flow to aid forward and stern direction

You, my friend, are BLESSED with a vessel that goes forward and back in
a straight line. Give thanks!!

"I'LL DRINK TO THAT!"

Ole Thom

ubject: Inherently beautiful.
From: (Thom Stewart)
Date: 10/23/2003 14:25 Pacific Standard Time
Message-id:

Shen,

You're way off about two bladed and folding. I have a single prop mono
hull and I use both a fixed Martec and at times a Martec Folding, Both
13x13. They both walk. The Folding much worst than the fixed, due the
the need of higher RPM's initially to open the blades.

You may very well be right, but for your application, not his, or possibly,
also his.
BG I have no experience in that area (folding props) and have said so, but
there are other points he has brought up, that make me think "prop walk", in
his case, is not a serious maneuvering factor ( don't know why, but think the
folding prop/pitch/efficiency may be inclusive as a factor).
If nothing else, I'm getting the sense that we need to throw out preconcieved
notions of twin screw boat handling, when discussing "cats" in general and
Jeff's in particular.

Jeff I don't have the answer of why you don't walk but I would suspect
it has to do with the Saildrives. Walking occurs on bare props. The
Saildrives have cavition plate and shaped housing forward and shedges
below which control the water flow to aid forward and stern direction

Can't agree with this, since I feel "propwalk" happens AT the prop and is not
related to G appertenances surrounding it (though they might have a very
slight effect on end results)

You, my friend, are BLESSED with a vessel that goes forward and back in
a straight line. Give thanks!!

"I'LL DRINK TO THAT!"

Ole Thom

As an addendum to your other post to Mooron (I believe) in the twin screw
world, there are three setups:
twin screw both same rotation - to be avoided at all cost (Jeff's exception
noted and reason for many of my questions).
Twin screw, inboard turning - a favorite of many "Supplyboats" and the Navy -
has it's advantages, but not my overall favorite.
Twin screw, outboard turning - what you'll find on the majority of twin screw
boats and my overall favorite.

Shen

Subject: Inherently beautiful.
From: "The Captains Nemesis
Date: 10/23/2003 13:45 Pacific Standard Time
Message-id:

On Thu, 23 Oct 2003 18:11:19 GMT, otnmbrd
wrote:

G Also interspersed

Jeff Morris wrote:

A simple test, would be both engines astern, equally. Since they are
both "left hand", your boat should immediately start backing to stbd.
How quickly and at what "turn rate", would indicate the degree of prop
walk.
I'm guessing here, but I'm betting you can steer your boat astern by
just increasing/decreasing throttle on one or the other of the engines?



I don't recall the boat ever doing anything other then going straight back
as it first
started up.

Interesting, G another test for next year?

Cats don't prop walk to the same extent as monos.
Probably the same reason they don't tack as easily.

I wonder how much of this is attributed to hull spacing and length.


Shen