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

"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

"Roger Long" wrote in message
...
"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

It sounds interesting, that's for sure.

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

"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

"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

As a follow up to this, I gave them a call. Unfortunately, they no longer
can do this work (it's not very expensive, about $160 for a 3-blade prop).
There is a patent issue. The guy I spoke with said he would be happy to
refer me to the patent holder (a former employee), but that it might be a
couple of months before he's going to be able to accept clients (the patent
holder that is).

They said that they had excellent results from the work, but of course this
is all heresay at this point.

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

On Fri, 12 May 2006 10:30:00 -0700, "Capt. JG"
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? Would tuning help? What do
you think?

Prop walk is a function of hull geometry, aperature size, prop pitch,
etc. One boater's solution may not solve yours.

However: I run a direct drive Atomic 4 on a '70s light cruiser-racer
with a fin keel and a spade rudder on a tiller. I used to have severe
prop walk with the stock Michigan Wheel 12 x 6 R.H. fixed two blader.
Just prior to launch I installed a Gori folding prop of 11.5 x 8
dimensions. It has made a significant difference in my handling under
power for the better, given me a good 1/2 knot increase in speed under
all conditions, better control and "bite" under low speeds, and best
of all, GREATLY reduced prop walk.

A friend of my with a very heavy steel 40' ketch with a full keel,
cutaway forefoot (36,000 lbs. in the slings) claims that cutting a
slightly larger aperature in his rudder allowed him to swing an
AutoProp custom cast for his boat. His frankly underpowered vessel (35
HP Volvo) can now dock like a minivan and makes 8.2 knots, a full knot
better. The thing sails better as well.

Call me a convert.

R.