backs like a pig
 

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?

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

backs like a pig
 

"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?

We have a Perkins 4-154 which had a fixed three blade prop. It also
backed poorly and had a prop walk. We replaced the prop with a Max
Prop (not because of that, but because the noise made by the shaft
spinning when we were under sail sounded like we were next to an
expressway). The Max Prop feathers (doesn't really fold), and the
blades are flat instead of cupped so that it will feather flat. This
meant that the boat backed better - the cupped blades only increase
the bite of the water when going forward. So

Not being an engineer or anything, and not even playing one on TV ...

My guess would be that yes the folding prop would help. Why is it
stored in a locker?



grandma Rosalie

S/V RosalieAnn, Leonardtown, MD
CSY 44 WO #156
http://home.mindspring.com/~gmbeasley/id1.html

backs like a pig
 

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.

Try pulsing the prop when in reverse.

Set engine speed relatively low, then shift into reverse for maybe
5-10 seconds, then back to neutral for maybe 30 seconds.

You will have to experiment with times.

Place rudder in desiored position.

Not perfect, but it will help.

Lew

backs like a pig
 

On Fri, 12 May 2006 10:30:00 -0700, in message

"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?

I swapped a large blade two-bladed fixed prop for a smaller blade Gori
folding prop of the same pitch and diameter. I didn't notice any
change in the walking behaviour. (But the boat sailed faster... )

Ryk


--
NewsGuy.Com 30Gb $9.95 Carry Forward and On Demand Bandwidth

backs like a pig
 

I was in Port Townsend, WA about 5 years ago. Talking to a guy who had
same problem so he called the designer of his production boat. Can not
remember the designer's name but he was someone legendary type.

The designer's response was, "I did not design my boats to sail
backwards."
Bob

backs like a pig
 

Prop walk is a function of 'tip clearance' to the hull and other hull
projections (aperture, etc.) , blade tip shape, , etc. etc. etc.

Just learn to 'back and fill' to steer going in reverse when there is
NO flow over the rudder ... and be prepared to use your rub-rails.
Especially if this is a full keeled boat with an aperture, you will
need LOTS of practice in 'backing and filling' to get it right; but,
once you 'learn', you will not want less prop-walk.

If you want to see exactly how to use prop-walk, go down to the
commercial docks and watch the prop-walk wizards / watermen fishermen
when they are about to land with a single screw boat -- always in a
hurry, LOTS of 'rpm burst', and precise maneuvering ... and all without
touching the wheel !!!!!.



In article , 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?

backs like a pig
 

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 caused by the design of the boat, mostly the downward angle
of the prop shaft. The more downward angle, the worse the walk will be.
Other factors contribute too, but that's the main one.

Changing the prop may cause a noticeable difference, but not enough to
matter.

Folding props reverse poorly, and won't help. Feathering props, such as
Max-prop's, actually reverse better than fixed props. This won't stop the
walk but it will give you more control.

On some boats I just put the wheel hard over and pulse the throttle, or
goose the tranny in and out of gear. The alternate turning forces cancel
each other, and with luck (and no wind) the boat goes straight back.

Practice!

Matt O.

backs like a pig
 

"Rosalie B." wrote in message
...
"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?

We have a Perkins 4-154 which had a fixed three blade prop. It also
backed poorly and had a prop walk. We replaced the prop with a Max
Prop (not because of that, but because the noise made by the shaft
spinning when we were under sail sounded like we were next to an
expressway). The Max Prop feathers (doesn't really fold), and the
blades are flat instead of cupped so that it will feather flat. This
meant that the boat backed better - the cupped blades only increase
the bite of the water when going forward. So

Not being an engineer or anything, and not even playing one on TV ...

My guess would be that yes the folding prop would help. Why is it
stored in a locker?



grandma Rosalie

S/V RosalieAnn, Leonardtown, MD
CSY 44 WO #156
http://home.mindspring.com/~gmbeasley/id1.html

I guess the owner felt that coming up the west coast he would have more
power with the fixed prop. That was the reason he gave, although I'm not
sure that makes sense.

Thanks for the thoughtful response. I appreciate it.

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

backs like a pig
 

"Lew Hodgett" wrote in message
nk.net...
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.

Try pulsing the prop when in reverse.

Set engine speed relatively low, then shift into reverse for maybe 5-10
seconds, then back to neutral for maybe 30 seconds.

You will have to experiment with times.

Place rudder in desiored position.

Not perfect, but it will help.

Lew

Lew, I'm familiar with this technique. My question was how to correct it
from a mechanical view, not how to correct it by technique. Thanks though.
It's nice to hear the technique mentioned.

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

backs like a pig
 

"Rich Hampel" wrote in message
...
Prop walk is a function of 'tip clearance' to the hull and other hull
projections (aperture, etc.) , blade tip shape, , etc. etc. etc.

Just learn to 'back and fill' to steer going in reverse when there is
NO flow over the rudder ... and be prepared to use your rub-rails.
Especially if this is a full keeled boat with an aperture, you will
need LOTS of practice in 'backing and filling' to get it right; but,
once you 'learn', you will not want less prop-walk.

If you want to see exactly how to use prop-walk, go down to the
commercial docks and watch the prop-walk wizards / watermen fishermen
when they are about to land with a single screw boat -- always in a
hurry, LOTS of 'rpm burst', and precise maneuvering ... and all without
touching the wheel !!!!!.



In article , 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?

Rich, as I mentionen in a previous response, I'm familiar with the
technique. I was looking for a mechanical solution. Thanks though.

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

backs like a pig
 

"Matt O'Toole" wrote in message
g...
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 caused by the design of the boat, mostly the downward angle
of the prop shaft. The more downward angle, the worse the walk will be.
Other factors contribute too, but that's the main one.

Changing the prop may cause a noticeable difference, but not enough to
matter.

Folding props reverse poorly, and won't help. Feathering props, such as
Max-prop's, actually reverse better than fixed props. This won't stop the
walk but it will give you more control.

On some boats I just put the wheel hard over and pulse the throttle, or
goose the tranny in and out of gear. The alternate turning forces cancel
each other, and with luck (and no wind) the boat goes straight back.

Practice!

Matt O.

Matt,

Thanks for the comments and comparisons between two type of prop. I'll take
it under advisement, and I don't actually know if what is in the locker is
folding or feathering.

Jonathan

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

backs like a pig
 

"Matt O'Toole" wrote in message
g...
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 caused by the design of the boat, mostly the downward angle
of the prop shaft. The more downward angle, the worse the walk will be.
Other factors contribute too, but that's the main one.

Changing the prop may cause a noticeable difference, but not enough to
matter.

Folding props reverse poorly, and won't help. Feathering props, such as
Max-prop's, actually reverse better than fixed props. This won't stop the
walk but it will give you more control.

On some boats I just put the wheel hard over and pulse the throttle, or
goose the tranny in and out of gear. The alternate turning forces cancel
each other, and with luck (and no wind) the boat goes straight back.

Practice!

Matt O.

FWIW, I have a Catalina 30 and have had both a fixed 2 blade and a fixed 3
blade prop on it. The prop walk is definitely and noticeably worse with the
3 blade. The diameter of both props is the same. Others on the Catalina 30
list claim that when they switched from the standard-issue 2 blade fixed
prop that usually comes from the factory to a Martec folder that the prop
walk goes down.

--Alan Gomes

backs like a pig
 

"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
 

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?

I think in the end that the best cure is technique. Once water starts
flowing along the keel and rudder, prop walk is minimized. Give the
boat a quick burst of power in reverse to get it moving a little and
then shift to neutral. Apply more reverse as needed in short bursts,
and use the rudder to compensate for additional prop walk.
Many people are reluctant to build too much boat speed in reverse but
it really does a lot to minimize control issues of al types.

backs like a pig
 

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?

The simple type of folding prop which opens by centrifugal force has about
as much stopping power when reverse is engaged as a car with silcone-coated
tyres on sheet ice. Folding props of this type have one purpose and one
purpose only, to minimise the prop-drag on a racing boat. If you minimise
the drag you also lower the forward thrust of the prop, hence the maximum
speed under engine at a given revs.

Efficient props have more prop-walk than inefficient props, so you have a
price to pay for maximum thrust. Most sailors get used to the prop-walk of
their particular boats and allow for it. In most cases they learn to make
good use of it, such as when backing into a marina berth, the angle of
approach being controlled intitially by the prop-walk factor. Once the boat
gathers way, the prop walk is minimised and the rudder takes over.

If you use the boat only once a week or less, you would take about 3 years
to learn the secret, so practice is essential, which is why professional
fishing-vessel skippers are so good at it.

It would be possible to design a prop which did not "walk". The same prop
would have little or no forward or reverse drive, and would therefore be
useless. The answer can be seen in new liners like the QM2, 4 independently
rotatable pods, each powered by it's own motor. Such technology is rather
expenssive for a small boat, but you can fit a bow thruster, which is a big
help.

backs like a pig
 

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
 

I agree. Having no ability to make the stern go sideways with minimal
forward or aft motion would complicate almost as many single screw
maneuvers as it simplified for the person who knows how to use the
prop force. It's almost like having a stern thruster.

It does mean though that the boat has a good side and a bad side in
many docking situation. I have a slip on the difficult side. 75% of
the time, the wind is quartering off the dock and half the time, the
current is as well so stopping the boat with three forces pulling the
stern away is an adventure. We've got it down pat though and I even
manage it single handed very often.

That said, the tiny propeller, large lateral plane, and high windage
of the typical sailboat make the propwalk force minimally useful
except in very calm conditions. When there is any wind, you can't
make our boat do the fancy things you see the lobster boats doing.

--

Roger Long



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
 

Generally, whenever this discussion arises we all tend to discuss or
think of our own boat and/or situation rather than talking about it in
a "generic" sense.
Forgetting wind and current for the moment. All propellor driven boats
will have prop walk to some degree, from hardly noticeable to "wowser"
and that difference will include two of the same type being totally
different due to how they are loaded with gear, fuel, people, etc..
If you have wind and current to consider, learn your boats "walking"
characteristics without wind and current first, then learn it with wind
and current, as sometimes one factor will totally negate the other.
Take, for instance, a single screw right hand prop docking stbd side
too (probably the toughest maneuver for this boat). No wind or
current.... use your prop walk to STOP your stern swinging into the
dock.
Now, same setup but port side too..... use your propwalk to START or
make your stern swing into the dock.
Since most boats will want to back into a wind or current you will have
to learn at what point of wind speed or current velocity and from what
directions will your boat be under the control of one factor (propwalk,
wind, current) or combination.
Obviously, no two conditions are the same and no one answer fits all.
I'd hate to tell you how many times I've started backing down expecting
my stern to go to port, only to find out that today it would rather go
to stbd.... and then after the fact, tried to figure out why.

Shen

backs like a pig
 

" wrote:

Generally, whenever this discussion arises we all tend to discuss or
think of our own boat and/or situation rather than talking about it in
a "generic" sense.
Forgetting wind and current for the moment. All propellor driven boats
will have prop walk to some degree, from hardly noticeable to "wowser"
and that difference will include two of the same type being totally
different due to how they are loaded with gear, fuel, people, etc..
If you have wind and current to consider, learn your boats "walking"
characteristics without wind and current first, then learn it with wind
and current, as sometimes one factor will totally negate the other.
Take, for instance, a single screw right hand prop docking stbd side
too (probably the toughest maneuver for this boat). No wind or
current.... use your prop walk to STOP your stern swinging into the
dock.
Now, same setup but port side too..... use your propwalk to START or
make your stern swing into the dock.
Since most boats will want to back into a wind or current you will have
to learn at what point of wind speed or current velocity and from what
directions will your boat be under the control of one factor (propwalk,
wind, current) or combination.
Obviously, no two conditions are the same and no one answer fits all.
I'd hate to tell you how many times I've started backing down expecting
my stern to go to port, only to find out that today it would rather go
to stbd.... and then after the fact, tried to figure out why.

The rule of thumb will be - if your boat usually backs to starboard,
and you want it to go to starboard, it will go to port.


There have been a couple of instances where we wanted to dock to port
(because that is the side the fuel fill is on), and just had to give
up on it and string the fuel hose all the way across the boat because
the engine could not overcome the wind and current (propwalk or no
propwalk).

In some cases the shore people were requiring a port docking, and we
could tell that it wasn't going to be possible. If they still
insisted, we would tell them that they would have to pull the boat in
to the dock by hand. Sometimes they could, and sometimes they could
not. It takes two of us to push the boat out from the dock against
any significant wind or current. (like in the Cooper River or in
Fernandina Beach). It is a heavy boat.

And sometimes they would tell us to do something - not being aware
that we have a modified full keel and not a fin keel - and without
telling us that there was a very swift current - this can result in
some scary situations when the current carries us sideways down the
fairway.

Bob will sometimes ask them to secure a bow line tight on something
and will run the boat forward into it - if there isn't too much wind
against us, that can get the boat swung around into the dock.

In two instances the shore person indicated a space on the face dock,
and Bob lined up the boat even with the space, and the boat was blown
sideways all the way across the channel and into the spot without us
using any engine at all.

grandma Rosalie

S/V RosalieAnn, Leonardtown, MD
CSY 44 WO #156
http://home.mindspring.com/~gmbeasley/id1.html

backs like a pig
 

yea, you just need to "get to know: the boat and how
she acts whilst backing down...all sailboats will want
to walk to one side at different rates...ist the "p factor"
we see in airplanes also...esp the single engine prop
planes...the torque from the spinning blade causes it...
just practice and get to know your vessel......

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

backs like a pig
 

"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

backs like a pig
 

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.

backs like a pig
 

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.

backs like a pig
 

On Sat, 13 May 2006 14:30:49 -0400, Wayne.B
wrote:


I think in the end that the best cure is technique. Once water starts
flowing along the keel and rudder, prop walk is minimized. Give the
boat a quick burst of power in reverse to get it moving a little and
then shift to neutral. Apply more reverse as needed in short bursts,
and use the rudder to compensate for additional prop walk.
Many people are reluctant to build too much boat speed in reverse but
it really does a lot to minimize control issues of al types.


I know the OP wanted physics and not art, but the prop walk of my old
fixed two-blade was so nasty (and contrary to my port side docking
situation) that I learned quite early to just walk the boat off the
dock in neutral and "coast" until I could put it in forward, and to
"dead stick" the boat back to dock by throwing it into neutral,
bleeding off speed in a sharp S turn and basically crabbing right into
my slip.

So even though I can back down straighter (after a slight pause as the
blades open), I still don't use a lot of reverse thrust. I fell out of
the habit.

R.

backs like a pig
 

"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

backs like a pig
 

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/

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

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