interspersed ...

"otnmbrd" wrote in message
ink.net...

....


A simple test, would be both engines astern, equally. Since they are
both "left hand", your boat should immediately start backing to stbd.
How quickly and at what "turn rate", would indicate the degree of prop walk.
I'm guessing here, but I'm betting you can steer your boat astern by
just increasing/decreasing throttle on one or the other of the engines?


I don't recall the boat ever doing anything other then going straight back as it first
started up.

Yes, I back down a long narrow fairway with throttle alone, rudders centered.




Thus, the net affect is zero propwalk, but I have no way to determine whether the
individual engines are generating propwalk.

Another way would be back on port engine and get a sense of "turn rate",
then back on stbd and compare (backing on stbd, could/should produce a
slower turn rate)

Yes, I should try that, if only to get an answer to this question.




BTW, the builder claimed this was a non-issue, but when they started building larger
sailing cats, and the powercat, they used counter-rotating props, because it was an
option
with the larger transmissions.

Your transmission/reverse gear is only built to turn in one direction?
Can't be built to turn opposite?

No, obviously there is a reverse, but many transmissions favor one direction amd the
other is only for intermittant use. There are differences in the gearing and the
lubrication. Other transmissions can be set up either way. I don't know what the issue
is with the small Volvo and Yanmar saildrives but the only props they (Volvo) make for
them are LH - I take that as a sign.

There is an often talked about case of a trawler that was setup counter rotating by
running one tranny in reverse. It took them a while to figure out why that transmission
always cooked in a few hundred hours.




Overall, I'm guessing that the spacing of your props, andG as mooron
says, the fact you have folding props of relatively little "bollard
pull" means that for most maneuvers you do, prop walk will be there, but
not of enough significance, when compared to the reaction of your boat
to the spacing and thrust of your props, so, as the builders claim, it
will generally be a non issue.


maybe so, maybe so.

otn

I had a situation with a Seawind 1000 that in some ways contradicts
the statement of being crippled in reverse with only one engine.

I was in a rather narrow channel and was waiting to dock. The
best was to do it in this situation was to back to the dock square
on the stern of the boat, step off and tie off the starboard side, then
use the port engine forward to bring the boat around for a side tie
on the starboard side (wind, current, tight quarters were the issues
involved).

During the wait for the other, larger mono to get the f*ck out of
the way, the starboard engine died and wouldn't restart (can't recall
what the problem was right now). I still managed to do the same
maneuver but it took longer and I had to jockey back and forth
a couple of times. Perhaps it's just a matter of taking it easy with
not too much engine.

Of course, forward has never been a problem on several large
cats. In Belize, the port engine was sounding funny one day
when we were in "get there" mode. I just turned it off and raised it
while we kept going.

Jonathan

"Jeff Morris" jeffmo@NoSpam-sv-lokiDOTcom wrote in message
...
After starting this little brouhaha I think I might have to modify my
claim that my cat
has no prop walk.

Since the props are widely spaced (15 feet with an 18 foot beam) if I ever
tried to back
on one engine the boat would "spin out" immediately. Although the boat is
functional with
one engine in forward, it is rather crippled for maneuvers in reverse.

Therefore, anytime I would be running one engine in close quarters, I
would be also be
running the other, and likely balancing so that it would back true, or
adjusting to turn
as desired. The only way I could tell that I had no prop walk would be to
carefully
measure the RPMs, and this is beyond my instrumentation.

Thus, the net affect is zero propwalk, but I have no way to determine
whether the
individual engines are generating propwalk.

BTW, the builder claimed this was a non-issue, but when they started
building larger
sailing cats, and the powercat, they used counter-rotating props, because
it was an option
with the larger transmissions.


"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

G Also interspersed

Jeff Morris wrote:

A simple test, would be both engines astern, equally. Since they are
both "left hand", your boat should immediately start backing to stbd.
How quickly and at what "turn rate", would indicate the degree of prop walk.
I'm guessing here, but I'm betting you can steer your boat astern by
just increasing/decreasing throttle on one or the other of the engines?



I don't recall the boat ever doing anything other then going straight back as it first
started up.

Interesting, G another test for next year?

Yes, I back down a long narrow fairway with throttle alone, rudders centered.

Sounds like a twin screw with outboard turning props, although we know
this isn't the case.
Think we're learning some things about "cats" here ... have a feeling
it's mainly due to spacing/hull length.




Thus, the net affect is zero propwalk, but I have no way to determine whether the
individual engines are generating propwalk.

Another way would be back on port engine and get a sense of "turn rate",
then back on stbd and compare (backing on stbd, could/should produce a
slower turn rate)


Yes, I should try that, if only to get an answer to this question.




BTW, the builder claimed this was a non-issue, but when they started building larger
sailing cats, and the powercat, they used counter-rotating props, because it was an

option

with the larger transmissions.

Your transmission/reverse gear is only built to turn in one direction?
Can't be built to turn opposite?


No, obviously there is a reverse, but many transmissions favor one direction amd the
other is only for intermittant use. There are differences in the gearing and the
lubrication. Other transmissions can be set up either way. I don't know what the issue
is with the small Volvo and Yanmar saildrives but the only props they (Volvo) make for
them are LH - I take that as a sign.

I say transmission/reverse gear, purely to note different terms for the
same thing.
It's interesting to note they only make the "gear" for left hand
.....wonder why....

There is an often talked about case of a trawler that was setup counter rotating by
running one tranny in reverse. It took them a while to figure out why that transmission
always cooked in a few hundred hours.

Have run across this situation in the past. It's not normally a quick
presto - chango. Sometimes engines were and possibly still are, built to
run opposite, and I remember one Boston ferry, was built with engines
gears set up for inboard turning props ( shocked the hell out of the
operator, first time he maneuvered it, since it didn't react at all like
what he was used to or expecting). It was, I believe, done
inadvertently, and they ended up switching gears and props to outboard
turning.

otn




Overall, I'm guessing that the spacing of your props, andG as mooron
says, the fact you have folding props of relatively little "bollard
pull" means that for most maneuvers you do, prop walk will be there, but
not of enough significance, when compared to the reaction of your boat
to the spacing and thrust of your props, so, as the builders claim, it
will generally be a non issue.



maybe so, maybe so.


otn

Yes there's always a way to get things done. I usually want to dock by pushing against a
spring, but the person on the dock inevitably runs the line forward instead of aft, so I
have to pull on it. I've given up planning too much, because the plans always seem to get
foiled at the last second. Fortunately, with the twins there are a lot of options.

I remember once talking to folks in a Manta 42 - they had just got a tow in from an
anchorage about 10 miles up the ICW. They had lost a prop and were afraid to bring the
boat in with one engine. I was surprised, but I understand - especially if they had
"unlimited" tow insurance.


"Jonathan Ganz" wrote in message
...
I had a situation with a Seawind 1000 that in some ways contradicts
the statement of being crippled in reverse with only one engine.

I was in a rather narrow channel and was waiting to dock. The
best was to do it in this situation was to back to the dock square
on the stern of the boat, step off and tie off the starboard side, then
use the port engine forward to bring the boat around for a side tie
on the starboard side (wind, current, tight quarters were the issues
involved).

During the wait for the other, larger mono to get the f*ck out of
the way, the starboard engine died and wouldn't restart (can't recall
what the problem was right now). I still managed to do the same
maneuver but it took longer and I had to jockey back and forth
a couple of times. Perhaps it's just a matter of taking it easy with
not too much engine.

Of course, forward has never been a problem on several large
cats. In Belize, the port engine was sounding funny one day
when we were in "get there" mode. I just turned it off and raised it
while we kept going.

Jonathan

"Jeff Morris" jeffmo@NoSpam-sv-lokiDOTcom wrote in message
...
After starting this little brouhaha I think I might have to modify my
claim that my cat
has no prop walk.

Since the props are widely spaced (15 feet with an 18 foot beam) if I ever
tried to back
on one engine the boat would "spin out" immediately. Although the boat is
functional with
one engine in forward, it is rather crippled for maneuvers in reverse.

Therefore, anytime I would be running one engine in close quarters, I
would be also be
running the other, and likely balancing so that it would back true, or
adjusting to turn
as desired. The only way I could tell that I had no prop walk would be to
carefully
measure the RPMs, and this is beyond my instrumentation.

Thus, the net affect is zero propwalk, but I have no way to determine
whether the
individual engines are generating propwalk.

BTW, the builder claimed this was a non-issue, but when they started
building larger
sailing cats, and the powercat, they used counter-rotating props, because
it was an option
with the larger transmissions.


"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

The biggest factor is the interaction of the prop with the hull.

Cheers MC

Jeff Morris wrote:

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

No, Bob, its not your fathers Oldsmobile, Ricardo Montleban (sp),
Chrysler, " fine, corinthian leathooooooor. Remember ?

On 22 Oct 2003 21:50:48 GMT, (Bobsprit) wrote:

Have you ever heard of a Corithian?

Yes...rich and soft, found in my dad's old Oldsmobile!

RB

Shen,

You're way off about two bladed and folding. I have a single prop mono
hull and I use both a fixed Martec and at times a Martec Folding, Both
13x13. They both walk. The Folding much worst than the fixed, due the
the need of higher RPM's initially to open the blades

Jeff I don't have the answer of why you don't walk but I would suspect
it has to do with the Saildrives. Walking occurs on bare props. The
Saildrives have cavition plate and shaped housing forward and shedges
below which control the water flow to aid forward and stern direction

You, my friend, are BLESSED with a vessel that goes forward and back in
a straight line. Give thanks!!

"I'LL DRINK TO THAT!"

Ole Thom

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

"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

No, Bob, its not your fathers Oldsmobile, Ricardo Montleban (sp),
Chrysler, " fine, corinthian leathooooooor. Remember ?

I do indeed. Sad to see him in a wheelchair these days. His knee problems
plagued him all his life, even when he was a champion swimmer.
Khan!!!!!

RB