Thrust vectoring
 

schlackoff, you are beyond belief. A Nobel prize winner in physics is
discussing physics and YOU say you know better. hell, schlackoff, even jeffies
abandoned you to swing slowly in the wind days ago.

first you didn't understand, than when I explained it to you you did, then when
you forgot what I explained (and couldn't remember how to remember) you didn't
believe, and when a world famous physicist explained it to go (complete with
movie) you stated flatly that you know better.

you are beyond belief. go crash a boat.

Never hoid of this Feynman character ...

here you go. 467,000 hits for you read. next time you will know who this
famous man was.

http://www.google.com/search?hl=en&i...59-1&q=feynman

btw schlackoff, Feynman won his Nobel prize in physics long ago, which he
got
his before you'll get yours.

...but can you or this Feynman handle a boat? We know you can't, and if Mr
Feynman can't apply his scientific "stuff" to boat handling, what good is he,
his nobel prize, or all his scientific papers to this discussion?

Sorry Jax, I larn't my boat handling by doing, not reading books.
My offer will increase to $600/hr at the end of the day, simply because
you're
a useless aggravation and I know I'll need a new pair of steel toed shoes,
after the first hour, to get your attention.

Shen

Thrust vectoring
 

schlackoff, go sleep it off. you have been overserved.

I attribute it to the pitch of the blades pulling to a greater
degree on the "down stroke" side of the revolution, than the "upstroke
side"

This is only true -- for a fixed blade prop -- when the shaft is angled AND
the
boat is moving.

Wrong on every point. Spout all the scientific crap you want .... can be
fixed
or variable pitch, horizontal or angled, moving or at the initial start
before
moving. .... what's most important is what the boat handler can see or feel.

A variable pitch prop will generally cause walk even at so called zero
pitch(the degree may vary, but it will still be a factor you need to
address);
a boat with a horizontal shaft will have prop walk, just like one with an
angled shaft (the degree may vary, but it will still be a factor you have to
address); immediately upon turning the prop, before you get sternway, you
will
get "propwalk"(the degree may vary, but it will still be a factor you will
have
to address).
Fer cripes sake, Jax, take some courses, get some experience .....hell, I'll
give you a bargain basement rate .... $800/hr.

Shen

Thrust vectoring
 

Date: 03/28/2004 16:54 Pacific Standard Time
Message-id:

schlackoff, go sleep it off. you have been overserved.

Jaxoff, get readmitted .... you don't have a clue as to what I said ....
obviously.
No response, no clue, typical Jaxoff.
Hint, Jaxoff ... what I stated,k apples to a practical application ....
something you have no experience with.

Shen

Thrust vectoring
 

schlackoff, go sleep it off. you have been overserved.

Thrust vectoring
 

ubject: Thrust vectoring
From: (JAXAshby)


schlackoff, you are beyond belief.
G are you talking to Shelikoff or Shen, or are you still confused?

A Nobel prize winner in physics is
discussing physics and YOU say you know better.

Yup, when it come to boat handling, I'll bet I can beat any Nobel prize winner
in physics or any other area, hands down..... cause, I know how to handle
boats, pure and simple. (hell, I bet I could teach my daughter to beat you,
hands down, and she Hates boats).

hell, schlackoff, even
jeffies
abandoned you to swing slowly in the wind days ago.

Nah, otn told him not to waste his time with your useless butt .... I do
because I have a jaded sense of humor and enjoy watching you make an ass of
yourself, even if I have to join you in the process.

first you didn't understand, than when I explained it to you you did, then
when
you forgot what I explained (and couldn't remember how to remember) you
didn't
believe, and when a world famous physicist explained it to go (complete with
movie) you stated flatly that you know better.

you are beyond belief. go crash a boat.

ROFL The only one here who doesn't understand is your royal jaxass.
I believe the "flip flop" you refer to is the fact that I stated that when
initially kicking an engine astern, I have seen some rudders move because of
that kick.
On my 26' Contessa, kick the engine astern, and if the rudder was not centered,
it would get pulled further over, before the boat ever started moving.
Now, I realize your book readin and larnin never mentioned this possibility,
but, alas, physics aside, in reality, honest to goodness, really, no lie, gosh
darn, it would happen .....eg go figure.
Naturally, because you have no real experience, you could not understand this,
or anything else, I've said, for that matter, regarding backing and steering.
Simply stated, jaxass, get a job which involves boat handling, work at it year
round in all weather, and come back and see me in about 10 years .... I'll let
you know then, how many more years you'll have to do it, before I'll consider
what you say worth listening to or thinking about.

Shen

Thrust vectoring
 

Subject: Thrust vectoring
From: (JAXAshby)
Date: 03/28/2004 15:30 Pacific Standard Time
Message-id:

schlackoff, three day ago you said a prop in reverse would affect a rudder,
then you read my explanation of the phenomenon and flip-flopped. Now, you
have
forgotten what your read, or remember what you understood then, and have
flip-flopped back.

tell us again how you are going to win the Nobel prize in physics as you
prove
Feynman wrong.

Jaxoff, read what I said and try to get mr Feynman to explain it to you,
regarding props and rudders, in reverse.
Only a stupid person would think that because someone has umpteen degrees and a
nobel prize, they should be considered expert boathandlers .... you are a
STUPID PERSON (note the complete use of capital letters).

Shen

PS I know I said "see ya", but you are sooooo amusing, my funny bone just
cain't stop playin a tune on yer dumb responses.

Thrust vectoring
 

On 28 Mar 2004 19:11:58 GMT, (Shen44) wrote:


G Never hoid of this Feynman character, before this thread....
Shen

He won a Nobel prize.
He was an accomplished bongo player too, and had a taste for women.

But I think you can take it that his bongo-playing talent and Nobel
class research endeavours are pretty well independent from
boat-handling skills. No Nobellist has ever won a major boat race, as
far as I know.

He could make pretty elementary errors too.
Like calculating the work needed to raise a metric tonne 0.1 meters
with a screw jack for instance. He didn't understand that it takes at
least 2000 joules. But then, he wasn't an engineer! :-)

He thought that if you worked out the potential energy equation m.g.h
m= mass, g = 9.81 m/s^2, h = height in meters,
you found the work done on the screw jack, you see....

Brian W

Thrust vectoring
 

On 28 Mar 2004 15:14:03 GMT, (Gould 0738) wrote:
Putting the boat in reverse will (after a split second) result in sternway
unless the engine is not running
or the vessel is lashed to the dock. When the sternway becomes sufficient, the
rudder exerts greater influence on the direction of boat than the prop walk
does.

==========================

Absolutely right. One of my favorite strategies for dealing with a
sailboat that has a nasty prop walk in reverse, is to give it a burst
of power in reverse where there is still some maneuvering room, get it
moving sternward at a knot or two, put the engine in neutral to kill
the prop walk, and then let the boat coast backward on momentum while
maneuvering with the rudder. Once the boat is moving the keel and
rudder take over, forward or reverse.

Thrust vectoring
 

Shen44 wrote in message
...
OK, think I see what you're saying.
First off, I used to run a 65 foot boat with a similar
configuration and
remember a beautiful old 45' ketch with the same thing ... both
had large
degrees of "propwalk".

Interesting. Some of the older boats had engines added later, of
course, and sensibly had prop shafts installed with an offset so
you could remove the shaft without taking the rudder off. That
changed the prop wallk picture a bit!

Secondly, I think we may have different views of what is the
major cause of
prop walk (I attribute it to the pitch of the blades pulling to
a greater
degree on the "down stroke" side of the revolution, than the
"upstroke side").

OK. The only certainty about prop walk is that it must be caused
by the prop in reverse squirting more water to one side of the
boat than the other. We could discuss the mechanism for ages -
but there wouldn't be much practical use to that unless we were
designers!

BG Why would I want to design "propwalk" out? "Propwalk" is
my friend!

Especially pulling the stern in as you come alongside.... bit of
a sod when it's the wrong side though.

JimB

Thrust vectoring
 

brian? what type of engineering training does an MIT professor of Mech Eng
have?

G Never hoid of this Feynman character, before this thread....
Shen

He won a Nobel prize.
He was an accomplished bongo player too, and had a taste for women.

But I think you can take it that his bongo-playing talent and Nobel
class research endeavours are pretty well independent from
boat-handling skills. No Nobellist has ever won a major boat race, as
far as I know.

He could make pretty elementary errors too.
Like calculating the work needed to raise a metric tonne 0.1 meters
with a screw jack for instance. He didn't understand that it takes at
least 2000 joules. But then, he wasn't an engineer! :-)

He thought that if you worked out the potential energy equation m.g.h
m= mass, g = 9.81 m/s^2, h = height in meters,
you found the work done on the screw jack, you see....

Brian W

Thrust vectoring
 

wayne, please read what you wrote and you will find you are saying exactly what
I am saying that you are disagreeing with so strongly. the boat MUST be
**moving** for the rudder to have an effect in reverse.

please read what you wrote again.

When the sternway becomes sufficient, the
rudder exerts

Absolutely right.

give it a burst
of power in reverse ... get it
moving sternward at a knot or two,

let the boat coast backward on momentum while
maneuvering with the rudder.

Once the boat is moving the keel and
rudder take over

Thrust vectoring
 

Once the boat is moving the keel and
rudder take over, forward or reverse.

in forward, you can use the prop blast to move the rudder. in reverse, you
can't.

but, yes, once the boat is moving in reverse the rudder can be used to turn the
boat.

Thrust vectoring
 

Subject: Thrust vectoring
From: Brian Whatcott
Date: 03/28/2004 19:26 Pacific Standard Time
Message-id:

On 28 Mar 2004 19:11:58 GMT, (Shen44) wrote:


G Never hoid of this Feynman character, before this thread....
Shen

He won a Nobel prize.
He was an accomplished bongo player too, and had a taste for women.

But I think you can take it that his bongo-playing talent and Nobel
class research endeavours are pretty well independent from
boat-handling skills. No Nobellist has ever won a major boat race, as
far as I know.


G haven't heard of too many that are pilots, either.

Shen

Thrust vectoring
 

Subject: Thrust vectoring
From: "JimB" j
Shen44 wrote in message

OK, think I see what you're saying.
First off, I used to run a 65 foot boat with a similar
configuration and
remember a beautiful old 45' ketch with the same thing ... both
had large
degrees of "propwalk".

Interesting. Some of the older boats had engines added later, of
course, and sensibly had prop shafts installed with an offset so
you could remove the shaft without taking the rudder off. That
changed the prop wallk picture a bit!

True There are many varying degrees of propwalk, for varying reasons (offsets,
kort nozzles, rope guards, to name a few). I normally board a boat and find out
type and rotation of prop to determine expected direction of walk, then as soon
as possible, if it's new to me I'll try to create a situatuion to test it out.
I've learned to expect a certain direction and amount of walk for some boats,
but always keep in mind that sometimes, especially on some boats they may walk
opposite to the expected (normally this will be a wind, current, or existing
turn situation, but not always.). .... at any rate, expect it, test it, and
then be ready for the unexpected.


Secondly, I think we may have different views of what is the
major cause of
prop walk (I attribute it to the pitch of the blades pulling to
a greater
degree on the "down stroke" side of the revolution, than the
"upstroke side").

OK. The only certainty about prop walk is that it must be caused
by the prop in reverse squirting more water to one side of the
boat than the other. We could discuss the mechanism for ages -
but there wouldn't be much practical use to that unless we were
designers!

Again true, although there is still prop walk when going fwd, it's just not
normally as noticeable.

BG Why would I want to design "propwalk" out? "Propwalk" is
my friend!

Especially pulling the stern in as you come alongside.... bit of
a sod when it's the wrong side though.

G Can also be used when docking the other side too, to stop the stern coming
alongside as you stop.
There is no doubt, that at times, prop walk is a pita, because it is contrary
to what you want and need to do, but in a high percentage of cases, it can be
made to work for you.

Shen

Thrust vectoring
 

On 28 Mar 2004 17:29:30 GMT, (JAXAshby) wrote:

that's a hermaphordite that nobody on either side of the
bed wants to play with. a twig too small to be a stick, and too long to be a
clit.

Not another one of your "what I did on shore leave" Navy stories, JAX.
There are young people present.

R.

Thrust vectoring
 

In article ,
Wayne.B wrote:

On 28 Mar 2004 15:14:03 GMT, (Gould 0738) wrote:
Putting the boat in reverse will (after a split second) result in sternway
unless the engine is not running
or the vessel is lashed to the dock. When the sternway becomes sufficient,
the
rudder exerts greater influence on the direction of boat than the prop walk
does.

==========================

Absolutely right. One of my favorite strategies for dealing with a
sailboat that has a nasty prop walk in reverse, is to give it a burst
of power in reverse where there is still some maneuvering room, get it
moving sternward at a knot or two, put the engine in neutral to kill
the prop walk, and then let the boat coast backward on momentum while
maneuvering with the rudder. Once the boat is moving the keel and
rudder take over, forward or reverse.


With our boat, that's the only way to do it. Until we're doing a knot or
two, we can at best keep the boat from pulling to port while the engine
is in gear. (a 16" prop *may* be a bit excessive for a 28' boat.)

Something that I've noticed, though I'm not sure if it's universal or
even really true: When I punch it, the prop walk seems to be minor. When
I want maximum prop walk, idle speed is the way to go. It could be just
that the duration is so much shorter, or that the higher thrust
straightens things out.

--
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/

Thrust vectoring
 

Something that I've noticed, though I'm not sure if it's universal or
even really true: When I punch it, the prop walk seems to be minor. When
I want maximum prop walk, idle speed is the way to go. It could be just
that the duration is so much shorter, or that the higher thrust
straightens things out.

--
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/


Could it be due to a short duration of a "punch" in reverse, or due to the
factor that sternway (and therefore rudder effectiveness) increased enough at
the higher RPM ? :-)

Thrust vectoring
 

Subject: Thrust vectoring
From: Jere Lull


I don't doubt that this is true for your boat (since you've observed it) but,
I'd bet it's not universal and would depend on the boat, set-up, and
conditions.
Why it occurs, would take someone familiar with boat props, and I would wonder
if it had anything to do with the fact that the prop might be working more
efficiently when starting at slower RPM's than at higher, especially if the
boat is DIW.
Another observation along the same lines .... I'm more apt to see the effects
of prop walk when going ahead, if boat speed is low.

Shen

Something that I've noticed, though I'm not sure if it's universal or
even really true: When I punch it, the prop walk seems to be minor. When
I want maximum prop walk, idle speed is the way to go. It could be just
that the duration is so much shorter, or that the higher thrust
straightens things out.

Thrust vectoring
 

Not another one of your "what I did on shore leave" Navy stories, JAX.

can't be. I was never in the Navy.


R.

Thrust vectoring
 

In article ,
(Gould 0738) wrote:

Something that I've noticed, though I'm not sure if it's universal or
even really true: When I punch it, the prop walk seems to be minor. When
I want maximum prop walk, idle speed is the way to go. It could be just
that the duration is so much shorter, or that the higher thrust
straightens things out.

--
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/


Could it be due to a short duration of a "punch" in reverse, or due to the
factor that sternway (and therefore rudder effectiveness) increased enough at
the higher RPM ? :-)

I've been tending toward that explanation except that a few seconds of
near-idle reverse can slide the transom over a foot without moving very
far; punching it for a few seconds (2000 rpm out of 3600), we don't seem
to pivot at all. When I shift to neutral, we don't have authoritative
steerage way yet.

Our prop (16x10x3 AutoProp) is pretty close to the rudder... Could we be
getting enough flow across it to counteract the walk?

What got me thinking about it and taking closer notes was watching a new
36 or 38' Catalina on charter try to back into a slip at idle last
September. Actually rotated more than it backed. The rudder never got a
chance. I'd never seen a sailboat do that badly, though I've seen a few
powerboats humble some mighty fine helmsmen.

--
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/

Thrust vectoring
 

Jere Lull wrote:
In article ,
(Gould 0738) wrote:


Something that I've noticed, though I'm not sure if it's universal or
even really true: When I punch it, the prop walk seems to be minor. When
I want maximum prop walk, idle speed is the way to go. It could be just
that the duration is so much shorter, or that the higher thrust
straightens things out.

--
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/


Could it be due to a short duration of a "punch" in reverse, or due to the
factor that sternway (and therefore rudder effectiveness) increased enough at
the higher RPM ? :-)


I've been tending toward that explanation except that a few seconds of
near-idle reverse can slide the transom over a foot without moving very
far; punching it for a few seconds (2000 rpm out of 3600), we don't seem
to pivot at all. When I shift to neutral, we don't have authoritative
steerage way yet.

Our prop (16x10x3 AutoProp) is pretty close to the rudder... Could we be
getting enough flow across it to counteract the walk?

G Take your wife's mixer, turn it on full and plunge it in a bowl of
milk. Basically, all you're going to do is splash milk all over the
kitchen. After you clean up the mess, refill the bowl an put the mixer
in and start it slowly ... no splashing and the milk will start to flow
smoothly i.e. the mixer will be working more efficiently at it's
intended task.
Since i think propwalk is a function of the prop rotation and pitch,
start it slowly and let it work as it is intended and it will do it's
thing and you will get more prop walk right off the bat, unlike you
might when you "punch" it and basically sit there and throw water until
the boats movement catches up to the props speed.
G I know .... totally unscientific, but waddahey.....

otn