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
|
|

Inherently beautiful.
From: "Capt. Mooron"


All very interesting ... I may not totally agree with your conclusions, but
there is some well thought out reasoning behind them.

Shen

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

"Shen44" wrote in message
...
| Inherently beautiful.
| From: "Capt. Mooron"
|
|
| All very interesting ... I may not totally agree with your conclusions,
but
| there is some well thought out reasoning behind them.

Well Shen... elaborate.... where do you think my theory is wrong?

CM

Subject: Inherently beautiful.
From: "Capt. Mooron"
Date: 10/22/2003 18:32 Pacific Standard Time
Message-id:


"Shen44" wrote in message
...
| Inherently beautiful.
| From: "Capt. Mooron"
|
|
| All very interesting ... I may not totally agree with your conclusions,
but
| there is some well thought out reasoning behind them.

Well Shen... elaborate.... where do you think my theory is wrong?

CM


I, Like otn, do not agree with the angled shaft creating all that noticeable a
difference in "prop walk".
Although I may agree that a prop tunnel, may act similiar to a Kort nozzle, for
an open prop, I don't think the prop wash behind a wide keel, when going astern
will have a noticeable affect on prop walk.
However, if nothing else, I've learned that no matter how much some might try
to say that the handling of a particular boat with a particular set up, can be
described by science, this is just not so ....each boat must be figured out,
and this applies to boats of the same class.
One thing I would say is that I'm inclined to agree with the notion that a
folding prop may have less walk/bite, but I'm not sure that has everything to
do with the fact that it's folding or more to do with it's pitch .... I don't
have enough experience and knowledge of them to say.

Shen

Shen

"Shen44" wrote in message
| I, Like otn, do not agree with the angled shaft creating all that
noticeable a
| difference in "prop walk".

I wonder if "sucking" wash at an angle may reduce the effect of the rudder.
I don't believe the angle affects the walk by itself.... only influences the
wash over the rudder.

| Although I may agree that a prop tunnel, may act similiar to a Kort
nozzle, for
| an open prop, I don't think the prop wash behind a wide keel, when going
astern
| will have a noticeable affect on prop walk.

Don't the newer cruise ships now use pod screws for better control and
performance? That would be like a prop in reverse ... sort of.

| However, if nothing else, I've learned that no matter how much some might
try
| to say that the handling of a particular boat with a particular set up,
can be
| described by science, this is just not so ....each boat must be figured
out,
| and this applies to boats of the same class.

I concur.

| One thing I would say is that I'm inclined to agree with the notion that a
| folding prop may have less walk/bite, but I'm not sure that has everything
to
| do with the fact that it's folding or more to do with it's pitch .... I
don't
| have enough experience and knowledge of them to say.

Well since none of us are experts in the field it only makes for a venue to
compare alternate viewpoints. It's of interest only to those of us who
consider the problem and wish to explore the situation.

CM

Subject: Inherently beautiful.
From: "Capt. Mooron"


"Shen44" wrote in message
| I, Like otn, do not agree with the angled shaft creating all that
noticeable a
| difference in "prop walk".

I wonder if "sucking" wash at an angle may reduce the effect of the rudder.
I don't believe the angle affects the walk by itself.... only influences the
wash over the rudder.

BG This may be part of the problem you are having with otn's comments.
Generally, when we discuss prop walk, we relate it to backing, not ahead
motions of the prop. Prop walk, when going ahead, is there and useful or
harmful, depending, but not as noticeable or well used as when going
astern.(which also means we may be trying to make totally different points)
I'm not sure what you mean by "sucking wash" regarding the effects of and on
the rudder?
The angle of the shaft, may well affect the wash across the rudder and how it
responds, but I would assume (right or wrong) that that may be accounted for by
some of the "tear drop" shapes you see in some rudders....only a guess.

| Although I may agree that a prop tunnel, may act similiar to a Kort
nozzle, for
| an open prop, I don't think the prop wash behind a wide keel, when going
astern
| will have a noticeable affect on prop walk.

Don't the newer cruise ships now use pod screws for better control and
performance? That would be like a prop in reverse ... sort of.

Azipods (was on one last weekend) They are more like a outboard drive that can
turn 360 deg (electric motor in the pod) independantly of each other .... kind
of like Z-drives on a tug. Yes, make for a highly maneuverable ship.


Shen

CM,

You must be over doing it on the "Overproof!" Jeff has "Zero" prop
walking.
Why in the world does he need a counter rotating engine?

OT

Don't know exactly Thom... but I believe it has something to do with wakes,
cut of the blade and Hydrodynamic stuff that is supposed to deliver better
power to twin outboards. Maybe some of the engineers here can enlighten us.
I know the boat I drove with the counter-rotating props was a dream to
maneuver.

CM

"Thom Stewart" wrote in message
...
| CM,
|
| You must be over doing it on the "Overproof!" Jeff has "Zero" prop
| walking.
| Why in the world does he need a counter rotating engine?
|
| OT
|

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