Shen, it's not really helpful to tell me stuff I already know. Anyone who's
been around boats for any length of time knows that prop walk can be used to
advantage. That has nothing to do with my question.

--
"j" ganz @@
www.sailnow.com

wrote in message
oups.com...
As long as you treat "propwalk" as the enemy, you will continue to have
problems with it and never learn to handle your boat well.
Learn to use it, treat it as your friend, compensate for it, and you'll
soon be wondering what all the fuss is about.
Accept it..... single screw or twin screw..... prop walk is an
important consideration to your boat's handling.

Shen

Roger Long wrote:
"Capt. JG" wrote

My question was how to correct it from a mechanical view, not how to
correct it by technique.

It's very difficult to correct mechanically. Physics are against you.
Open wheels are always going to walk. Variations in size and number
of blades with change the degree but the psychological effect of
spending a grand or more to reduce the problem will often be greater
than the actual change in forces.

The difference in water density with depth makes the wheel act like a
paddle wheel (grossly oversimplified explanation warning).

Three things you can do:

Put the prop in a nozzle. You really won't be happy with the drag
under sail of this arrangment!

Twin props. Not much better from the drag standpoint.

Angle the shaft to counteract the effect and normal backing speed.
Going forward faster and with more rudder authority, the off center
thrust will not be as noticeable.

Neither of these are practical as a retrofit.

--

Roger Long

Then I may be reading more or less into your question than I thought.
I don't believe anyone could give you a definitive answer as to whether
a particular prop would reduce prop-walk on your particular boat
without you actually trying it out, and that can get expensive,
especially if you don't like the results in other areas of performance.
If you are generally happy with the overall performance of your prop
then I would look first to the "operator" to solve your possible
problem.
Nine times out of ten, this is where the real problem lies......
course, I couldn't say if this was true in your case unless I road with
you and watched and then I could easily end up agreeing with you......
or not.

Shen

wrote in message
ups.com...
Then I may be reading more or less into your question than I thought.
I don't believe anyone could give you a definitive answer as to whether
a particular prop would reduce prop-walk on your particular boat
without you actually trying it out, and that can get expensive,
especially if you don't like the results in other areas of performance.
If you are generally happy with the overall performance of your prop
then I would look first to the "operator" to solve your possible
problem.
Nine times out of ten, this is where the real problem lies......
course, I couldn't say if this was true in your case unless I road with
you and watched and then I could easily end up agreeing with you......
or not.

Shen


I thought my question was pretty specific:

According to the owner, it's got a fixed, 3-blade prop. I believe the boat
also has a folding prop aboard in a locker. Would that help? Would
tuning help?

Perhaps you should re-read the question.

--
"j" ganz @@
www.sailnow.com

On Mon, 15 May 2006 10:09:35 -0700, "Capt. JG"
wrote:

According to the owner, it's got a fixed, 3-blade prop. I believe the boat
also has a folding prop aboard in a locker. Would that help? Would
tuning help?

It's probably safe to say that the 2 bladed folding prop will have
less "walk" than a fixed 3 bladed. That is not necessarily the best
solution however, depending on how the boat is used. For a heavily
loaded cruising boat that spends a lot of time under power or motor
sailing, a 3 bladed prop can be a nice thing to have because it will
generate more thrust, with less slip, both forward and reverse, than a
2 bladed folder. On the other hand if the owner is also concerned
with light air sailing performance, and is willing to take the
necessary steps to ensure that the prop folds properly, then that is
the way to go. I would not go to a folding prop just to minimize prop
walk. My personal choice for a cruising boat would be a 3 bladed
feathering prop.

"Wayne.B" wrote in message
...
On Mon, 15 May 2006 10:09:35 -0700, "Capt. JG"
wrote:

According to the owner, it's got a fixed, 3-blade prop. I believe the boat
also has a folding prop aboard in a locker. Would that help? Would
tuning help?

It's probably safe to say that the 2 bladed folding prop will have
less "walk" than a fixed 3 bladed. That is not necessarily the best
solution however, depending on how the boat is used. For a heavily
loaded cruising boat that spends a lot of time under power or motor
sailing, a 3 bladed prop can be a nice thing to have because it will
generate more thrust, with less slip, both forward and reverse, than a
2 bladed folder. On the other hand if the owner is also concerned
with light air sailing performance, and is willing to take the
necessary steps to ensure that the prop folds properly, then that is
the way to go. I would not go to a folding prop just to minimize prop
walk. My personal choice for a cruising boat would be a 3 bladed
feathering prop.

Wayne,

Do you think there would be a significant difference between a 3-blade
feathering prop and a 2-blade folding prop? I guess my question is why would
you prefer that prop?

FYI, most of the sailing is on the SF bay, so lots of wind, strong currents,
etc.

--
"j" ganz @@
www.sailnow.com

On Mon, 15 May 2006 14:43:40 -0700, "Capt. JG"
wrote:

Do you think there would be a significant difference between a 3-blade
feathering prop and a 2-blade folding prop? I guess my question is why would
you prefer that prop?

FYI, most of the sailing is on the SF bay, so lots of wind, strong currents,
etc.

It's hard to say without actually trying the swap. You might be able
to find a diver who can swap the props underwater at a reasonable
price.

Is there racing involved? If yes, I would choose the folding prop
regardless. In order to get the prop to fold reliably it is necessary
to mark the shaft when the hinge pin is vertical, and manually align
the shaft to that point every time you shut down the engine before
racing. Otherwise the lower blade will flop downward and defeat the
purpose of drag reduction.

"Wayne.B" wrote in message
...
On Mon, 15 May 2006 14:43:40 -0700, "Capt. JG"
wrote:

Do you think there would be a significant difference between a 3-blade
feathering prop and a 2-blade folding prop? I guess my question is why
would
you prefer that prop?

FYI, most of the sailing is on the SF bay, so lots of wind, strong
currents,
etc.

It's hard to say without actually trying the swap. You might be able
to find a diver who can swap the props underwater at a reasonable
price.

Is there racing involved? If yes, I would choose the folding prop
regardless. In order to get the prop to fold reliably it is necessary
to mark the shaft when the hinge pin is vertical, and manually align
the shaft to that point every time you shut down the engine before
racing. Otherwise the lower blade will flop downward and defeat the
purpose of drag reduction.

No racing involved unless the other boat is unawares. :-) There are plenty
of divers around, but I suppose it would be just as easy to swap them during
the next haul, which is coming up in June.

--
"j" ganz @@
www.sailnow.com

In article ,
"Capt. JG" wrote:

Do you think there would be a significant difference between a 3-blade
feathering prop and a 2-blade folding prop? I guess my question is why would
you prefer that prop?

We need three blades to combat a vibration. The feathering prop (two or
three blade) will back more reliably. You have to be more deliberate
when backing a feathering prop. Going forward, the difference in drag
won't be noticeable.

--
Jere Lull
Xan-a-Deux ('73 Tanzer 28 #4 out of Tolchester, MD)
Xan's Pages: http://members.dca.net/jerelull/X-Main.html
Our BVI FAQs (290+ pics) http://homepage.mac.com/jerelull/BVI/

-
"Capt. JG" wrote in message ...
wrote in message ups.com...
Then I may be reading more or less into your question than I thought.
I don't believe anyone could give you a definitive answer as to whether
a particular prop would reduce prop-walk on your particular boat
without you actually trying it out, and that can get expensive,
especially if you don't like the results in other areas of performance.
If you are generally happy with the overall performance of your prop
then I would look first to the "operator" to solve your possible
problem.
Nine times out of ten, this is where the real problem lies......
course, I couldn't say if this was true in your case unless I road with
you and watched and then I could easily end up agreeing with you......
or not.

Shen


I thought my question was pretty specific:

According to the owner, it's got a fixed, 3-blade prop. I believe the boat
also has a folding prop aboard in a locker. Would that help? Would
tuning help?

A new attitude?


Perhaps you should re-read the question.

--
"j" ganz @@
www.sailnow.com

"Harbin" wrote in message
...
-
"Capt. JG" wrote in message
...
wrote in message
ups.com...
Then I may be reading more or less into your question than I thought.
I don't believe anyone could give you a definitive answer as to whether
a particular prop would reduce prop-walk on your particular boat
without you actually trying it out, and that can get expensive,
especially if you don't like the results in other areas of performance.
If you are generally happy with the overall performance of your prop
then I would look first to the "operator" to solve your possible
problem.
Nine times out of ten, this is where the real problem lies......
course, I couldn't say if this was true in your case unless I road with
you and watched and then I could easily end up agreeing with you......
or not.

Shen


I thought my question was pretty specific:

According to the owner, it's got a fixed, 3-blade prop. I believe the
boat
also has a folding prop aboard in a locker. Would that help? Would
tuning help?

A new attitude?


Perhaps you should re-read the question.

--
"j" ganz @@
www.sailnow.com

So, what you're saying is that you don't understand the questions. Got it.

--
"j" ganz @@
www.sailnow.com