backs like a pig
 

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

backs like a pig
 

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

backs like a pig
 

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

backs like a pig
 

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.

backs like a pig
 

-
"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

backs like a pig
 

"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

backs like a pig
 

"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

backs like a pig
 

wrote:

Back to more questions somewhat related to the Perkins 4-108. This
sailboat
is a pig to back up. It really wants to prop walk to starboard.
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?

First off, put me in the camp that recommends technique as a means for
neutralizing prop walk. You seriously do not want to eliminate prop walk
as it is the only thing that will turn the stern of your boat predictably
and reliably. People's biggest beef is that it will turn the stern in only
one direction and I can see that if you're viewing boats as watery
versions of cars, then this would be a little upsetting. If you want to
see what prop walk can do, check out the Dashew video "Dashew Offshore".
They are able to spin their vessel 360 degress with ZERO headway. All
technique.

That said, I can understand where some people may not be in the right
frame of mind to learn technique (think reluctant sailing wife being given
"verbal hints" when backing down an anchor). You also mentioned that the
vessel was being sailed in SF bay. You may want to know that there is a
prop shop called Bay Propeller (510-337-9122) that has a technique for
modifying fixed props. They tap the blade tips over to create little
tiplets. They claim it eliminates prop walk AND increases thrust. I have
no personal experience with their results, but it would be worth a try.

David

backs like a pig
 

"dbraun" wrote

You may want to know that there is a
prop shop called Bay Propeller (510-337-9122) that has a technique
for
modifying fixed props. They tap the blade tips over to create little
tiplets. They claim it eliminates prop walk AND increases thrust. I
have
no personal experience with their results, but it would be worth a
try.

This is a very cool idea and there are some sound physics behind it.
I doubt that it completely eliminates prop walk but it might will
reduce it to the point that it isn't noticable. Prop walk has a lot
to do with the vortexes thrown off the tip if any airfile and tiplets
reduce them. That's why you see them cropping up on the wings of most
new aircraft.

I'm not endorsing or claiming that this does work, just that the
rational is solid enough that I wouldn't reject it out of hand.

--

Roger Long

backs like a pig
 

"dbraun" wrote in message
lkaboutboats.com...
wrote:

Back to more questions somewhat related to the Perkins 4-108. This
sailboat
is a pig to back up. It really wants to prop walk to starboard.
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?

First off, put me in the camp that recommends technique as a means for
neutralizing prop walk. You seriously do not want to eliminate prop walk
as it is the only thing that will turn the stern of your boat predictably
and reliably. People's biggest beef is that it will turn the stern in only
one direction and I can see that if you're viewing boats as watery
versions of cars, then this would be a little upsetting. If you want to
see what prop walk can do, check out the Dashew video "Dashew Offshore".
They are able to spin their vessel 360 degress with ZERO headway. All
technique.

That said, I can understand where some people may not be in the right
frame of mind to learn technique (think reluctant sailing wife being given
"verbal hints" when backing down an anchor). You also mentioned that the
vessel was being sailed in SF bay. You may want to know that there is a
prop shop called Bay Propeller (510-337-9122) that has a technique for
modifying fixed props. They tap the blade tips over to create little
tiplets. They claim it eliminates prop walk AND increases thrust. I have
no personal experience with their results, but it would be worth a try.

David

David, please show me where I said I wanted to eliminate prop walk? It's
excessive in my experience, and I'm looking for a non-technique solution.

I've never know anyone who was seriously into sailing who does not
eventually get in the "right" frame of mind to learn technique.

In any case, thanks for the number!

I or the owner will give them a call.

Jonathan

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