I can't agree here, although I've also heard this and there may be some
validity to it. However, most ships I've been on, have very little angle
on their shafts ..... they torque to port like an SOB, more so with
engine speed than not.
There are many reasons/factors which will affect "prop walk", and some
boats will ignore it, if the wind/current is strong enough, but I'm also
inclined to think "pitch" is the major factor, and Jeff's two bladed
props may not have or need much for his application.

BTW Boobsprit, we will occasionally get into a ****ing match with Neal,
since on rare instances he show's some trolling intelligence .... you
are, on the other hand, a total waste of effort, not worth more than one
or two responses on extremely rare occasions, purely to note your idiocy.

otn

Capt. Mooron wrote:
I believe Shen is wrong here Jeff and you are right. The angle of the shaft
would definitely affect propwalk. It's not the only factor but it will
contribute. I think the biggest villain is pitch and rudder placement as
well as flow and entry/exit of the prop wash.

I think there is less propwalk on folding/ feathering props. I carry a
13"x19# LH 3 bladed prop with a stern hung tiller that is the size of a
small barn door. The prop well unfortunately is small and my upper clearance
is only 4". The keel is 5" thick at the shaft and this affects the flow to
the prop and correspondingly to the rudder in reverse.

Wouldn't it be wise in a twin screw configuration to have counter-rotating
props? This would eliminate propwalk altogether. I was coxswain on a Aux CCG
with a pair of matched outboards and counter-rotating props.... I could
station keep that bugger in the worst conditions with no problems.

CM


"Jeff Morris" jeffmo@NoSpam-sv-lokiDOTcom wrote in message
...
| My props are Left-Hand, two blade folding. There is virtually no
propwalk. I'm quite
| familiar with the phenomenon because my old Nonsuch would walk hard to
port, as would all
| the single screw boats I've driven.
|
| I was under the impression that a major contributor to prop walk was the
angle of the
| shaft; thus, if its horizontal, the affect is greatly reduced. If this
isn't the case,
| what does cause it?
|
| -jeff
|
|
|
| "Shen44" wrote in message
| ...
| Subject: Inherently beautiful.
| From: "Jeff Morris" jeffmo@NoSpam-sv-lokiDOTcom
| Date: 10/22/2003 13:00 Pacific Standard Time
| Message-id:
|
| Neal really doesn't understand, even though I explained it fully.
He'll
| figure it out and
| come up with a creative way to cover his ignorance!
|
| BTW, I get virtually no prop walk - is that because the shaft is
horizontal,
| the blades
| are flat, the keel is long, or a combination of all three?
|
|
| None of the three SHOULD eliminate "prop walk", singly or in combination
....
| G you don't have Kort nozzles, do you?
| To be sure I'm thinking correctly, both your props are right hand,
folding? (I
| have no experience with folding, so I don't know if this may be a
factor).
|
| When backing, your boat, should want to back to port, as Neal said, once
you
| lose steerageway .... does it? (assuming two right hand props ... I
can't
| remember if you said right or left).
|
| Shen
|
|

"otnmbrd" wrote in message
nk.net...
| I can't agree here, although I've also heard this and there may be some
| validity to it. However, most ships I've been on, have very little angle
| on their shafts ..... they torque to port like an SOB, more so with
| engine speed than not.

Well I would expect that angle of the shaft affects direction of the prop
wash against the rudder... that would be plain common sense. I distinctltly
stated that I couldn't state one single overwhelming factor for propwash
from my experiences. I never claimed your theory to be false only that I
didn't completely agree with the premise.


| There are many reasons/factors which will affect "prop walk", and some
| boats will ignore it, if the wind/current is strong enough, but I'm also
| inclined to think "pitch" is the major factor, and Jeff's two bladed
| props may not have or need much for his application.

May I suggest reading for content rather than confrontation.... I wrote as
plain as day "I think the biggest villain is pitch and rudder placement as
well as flow and entry/exit of the prop wash."

| BTW Boobsprit, we will occasionally get into a ****ing match with Neal,
| since on rare instances he show's some trolling intelligence .... you
| are, on the other hand, a total waste of effort, not worth more than one
| or two responses on extremely rare occasions, purely to note your idiocy.

Now this petty, delusional, uncalled for, idiotic, uninspired statement just
blows your entire argument and casts doubt on the validity of your
intentions. If it's confrontation you want .... clarify that and I'll
accommodate you. It's not like you have the aptitude to contest me on either
a verbal or physical arena. You want to troll ... keep it on rec boats where
you have a chance of success. Around here you have little credibility and
absolutely no influence.

CM

ROFL, Cool your jets, Mooron ... I'm not confronting you, I'm talking to
you .....comments interspersed:

Capt. Mooron wrote:
"otnmbrd" wrote in message
nk.net...
| I can't agree here, although I've also heard this and there may be some
| validity to it. However, most ships I've been on, have very little angle
| on their shafts ..... they torque to port like an SOB, more so with
| engine speed than not.

Well I would expect that angle of the shaft affects direction of the prop
wash against the rudder... that would be plain common sense. I distinctltly
stated that I couldn't state one single overwhelming factor for propwash
from my experiences. I never claimed your theory to be false only that I
didn't completely agree with the premise.

Quite possibly correct, but when going astern, there would be no prop
wash past the rudder and I would say most would see the affects of
propwalk to a greater degree when backing. G You don't have to
completely agree with me any more than I do with you. We're talking the
possibilities, here.


| There are many reasons/factors which will affect "prop walk", and some
| boats will ignore it, if the wind/current is strong enough, but I'm also
| inclined to think "pitch" is the major factor, and Jeff's two bladed
| props may not have or need much for his application.

May I suggest reading for content rather than confrontation.... I wrote as
plain as day "I think the biggest villain is pitch and rudder placement as
well as flow and entry/exit of the prop wash."

G The only confrontation, was in your own reading of the content. My
statement was that I felt it was mainly pitch (shoulda, coulda said
also). I don't think it has as much to do with rudder placement although
flow and entry/exit of the wash from the prop probably does count.

| BTW Boobsprit, we will occasionally get into a ****ing match with Neal,
| since on rare instances he show's some trolling intelligence .... you
| are, on the other hand, a total waste of effort, not worth more than one
| or two responses on extremely rare occasions, purely to note your idiocy.

Now this petty, delusional, uncalled for, idiotic, uninspired statement just
blows your entire argument and casts doubt on the validity of your
intentions. If it's confrontation you want .... clarify that and I'll
accommodate you. It's not like you have the aptitude to contest me on either
a verbal or physical arena. You want to troll ... keep it on rec boats where
you have a chance of success. Around here you have little credibility and
absolutely no influence.

CM

ROFL the last paragraph was dedicated to Boobsprit, as an afterthought
(figure he reads them all) and had nothing to do with you (read for
content). Seems to me, the only one here looking for confrontation, is
you, I was having a discussion .....

otn

"otnmbrd" wrote in message
nk.net...
| ROFL, Cool your jets, Mooron ... I'm not confronting you, I'm talking to
| you .....comments interspersed:

Warp engines offline, standing down, docking thrusters activated. :-)

Amazing what a "we" before the will can cause when it's not picked up in the
initial read through!
I'd kick myself but I'm having too much fun laughing at my own expense!


| Quite possibly correct, but when going astern, there would be no prop
| wash past the rudder and I would say most would see the affects of
| propwalk to a greater degree when backing. G You don't have to
| completely agree with me any more than I do with you. We're talking the
| possibilities, here.

Gothcha... I'm just not correctly differentiating between flow and wash on
the prop in my original reply. My prop actually becomes narrower further
down. The prop is angled so that the flow would be strongest at the point
where it begins to narrow the most. I believe that's the reason I have such
a bitch of a time with propwalk to starboard in reverse.

CM

Capt. Mooron wrote:



| Quite possibly correct, but when going astern, there would be no prop
| wash past the rudder and I would say most would see the affects of
| propwalk to a greater degree when backing. G You don't have to
| completely agree with me any more than I do with you. We're talking the
| possibilities, here.

Gothcha... I'm just not correctly differentiating between flow and wash on
the prop in my original reply. My prop actually becomes narrower further
down. The prop is angled so that the flow would be strongest at the point
where it begins to narrow the most. I believe that's the reason I have such
a bitch of a time with propwalk to starboard in reverse.

CM

So, you've also got a lefthand prop (There are more of them out there
than people realize).
I really can't say, whether the above is the reason, or not. In "most"
cases, single screw, no matter what the hull design (inboard, fixed
pitch prop, right or left) when backing down, you are going to get a
serious condition of prop walk, which can be a pain and a boon to boat
handling (exceptions noted). However, there are many boats/ships out
there, that 8 out of ten times will torque as expected .... the next two
times they'll go in the opposite direction, for no reason, or at least
none that you can figure out at the time.

otn

"otnmbrd" wrote in message
| So, you've also got a lefthand prop (There are more of them out there
| than people realize).

Yup...

| I really can't say, whether the above is the reason, or not. In "most"
| cases, single screw, no matter what the hull design (inboard, fixed
| pitch prop, right or left) when backing down, you are going to get a
| serious condition of prop walk, which can be a pain and a boon to boat
| handling (exceptions noted). However, there are many boats/ships out
| there, that 8 out of ten times will torque as expected .... the next two
| times they'll go in the opposite direction, for no reason, or at least
| none that you can figure out at the time.

I try and use it to my advantage whenever possible. I have found that with
short bursts of high RPM I can compensate for most of the walk... some of
the time. For a full keeler I can spin it on a dime in quite water by short
bursts of forward and reverse.

CM

Every boat, operator, and set of conditions differ. I try never to use
any more power than is necessary, but, what works for me, may not work
for the next guy. A nice full keel sailboat, is one of the best learning
experiences for single screw powerboating, as they tend to be very
predictable, and relatively responsive to gentle prods.


otn

Capt. Mooron wrote:
"otnmbrd" wrote in message
| So, you've also got a lefthand prop (There are more of them out there
| than people realize).

Yup...

| I really can't say, whether the above is the reason, or not. In "most"
| cases, single screw, no matter what the hull design (inboard, fixed
| pitch prop, right or left) when backing down, you are going to get a
| serious condition of prop walk, which can be a pain and a boon to boat
| handling (exceptions noted). However, there are many boats/ships out
| there, that 8 out of ten times will torque as expected .... the next two
| times they'll go in the opposite direction, for no reason, or at least
| none that you can figure out at the time.

I try and use it to my advantage whenever possible. I have found that with
short bursts of high RPM I can compensate for most of the walk... some of
the time. For a full keeler I can spin it on a dime in quite water by short
bursts of forward and reverse.

CM