Jere Lull wrote in message
...
In article
.net,
otnmbrd wrote:

I don't think you're simply talking about the wash over the
rudder. That
is clearly thrust vectoring, but should be easy enough to
explain as
"kicking the ass over".

I like Jere's approach. It correctly describes both phenomena you
get using rudder with power; first, a rotation, secondly, a
lateral movement.

When teaching, I've found it useful to separate the two
phenomena.

First, how to point the boat. If you're static, that's using one
engine ahead and one astern to swivel around a point with rudder
neutral. If you're moving forward significantly (or aft) that's
using rudder or differential engine to steer.

Second, how to shift the boat (or part of it) bodily sideways.
That's using wind, and/or prop walk, and/or power with rudder
(the other engine being used to control the degree of fore/aft
movement), and/or bow thruster. The last three I certainly
understand as 'thrust vectoring' (I'm familiar with the term as
an ex VTOL pilot, and most numerate people would be OK with
'vectoring').

When teaching, though, I'd test my pupil's understanding of the
phrase before using it. After all, the student may be numerate -
as an accountant - rather than a physics major. And 'kicking ass'
does have a nice ring to it . . .

JimB, Yacht Rapaz, sadly, for sale to buy that nice new Greek
house:
http://www.homepage.ntlworld.com/jim...cification.htm

Thanks. One of the things I tend to talk about is the potential
advantage of using rudders when twisting (swivel) as it tends to help
when you work into how you need to set your rudders to "walk".

otn

JimB wrote:

I like Jere's approach. It correctly describes both phenomena you
get using rudder with power; first, a rotation, secondly, a
lateral movement.

When teaching, I've found it useful to separate the two
phenomena.

First, how to point the boat. If you're static, that's using one
engine ahead and one astern to swivel around a point with rudder
neutral. If you're moving forward significantly (or aft) that's
using rudder or differential engine to steer.

Second, how to shift the boat (or part of it) bodily sideways.
That's using wind, and/or prop walk, and/or power with rudder
(the other engine being used to control the degree of fore/aft
movement), and/or bow thruster. The last three I certainly
understand as 'thrust vectoring' (I'm familiar with the term as
an ex VTOL pilot, and most numerate people would be OK with
'vectoring').

When teaching, though, I'd test my pupil's understanding of the
phrase before using it. After all, the student may be numerate -
as an accountant - rather than a physics major. And 'kicking ass'
does have a nice ring to it . . .

JimB, Yacht Rapaz, sadly, for sale to buy that nice new Greek
house:
http://www.homepage.ntlworld.com/jim...cification.htm

careful. you *must* be moving through the water for a rudder to be effective
when trying to back up.

Thanks. One of the things I tend to talk about is the potential
advantage of using rudders when twisting (swivel) as it tends to help
when you work into how you need to set your rudders to "walk".

otn

Subject: Thrust vectoring
From: (JAXAshby)

Huh? What does that have to do with what he is saying .... "back up" is not
being discussed.

Shen


careful. you *must* be moving through the water for a rudder to be effective
when trying to back up.

Thanks. One of the things I tend to talk about is the potential
advantage of using rudders when twisting (swivel) as it tends to help
when you work into how you need to set your rudders to "walk".

otn

schlackoff, you were told to never post in English. Adults are posting and
they use big words like "docking" and such.

Huh? What does that have to do with what he is saying .... "back up" is not
being discussed.

Shen


careful. you *must* be moving through the water for a rudder to be
effective
when trying to back up.

Thanks. One of the things I tend to talk about is the potential
advantage of using rudders when twisting (swivel) as it tends to help
when you work into how you need to set your rudders to "walk".

otn

Subject: Thrust vectoring
From: (JAXAshby)

Jaxass, your comment has nothing to do with what he's been discussing.
It is, however, very basic knowledge, which I'm surprised you know...... it can
also be applied to moving ahead, but that's probably too much "input" for you
for one day.

Shen

schlackoff, you were told to never post in English. Adults are posting and
they use big words like "docking" and such.

Huh? What does that have to do with what he is saying .... "back up" is not
being discussed.

Shen


careful. you *must* be moving through the water for a rudder to be
effective
when trying to back up.

Thanks. One of the things I tend to talk about is the potential
advantage of using rudders when twisting (swivel) as it tends to help
when you work into how you need to set your rudders to "walk".

o

t can
also be applied to moving ahead,

no, it can not. water *pushed* over a rudder can cause a rudder to turn a
boat, while water "pulled" over a rudder can not.

JAXAshby wrote in message
...
careful. you *must* be moving through the water for a
rudder to be effective
when trying to back up.

Not quite true. When 'trying to back up' (attempting
rearward motion) you will often use bursts of ahead over the
rudder to alter the pointing of a boat, whether you're
static or actually moving astern.

Very large diameter props, well sheltered from prop walk,
with a large rudder close to the prop (as on single prop
tugs and some fishing vessels), will, in astern, cause
rudder to alter the direction from which water is ingested
into
the prop. If the water is ingested from one direction,
and exits in another, that deflection causes a change in
lateral momentum - creating a force which in turn causes a
yaw. Of course, single screw tugs are not so common now, and
this thread was about twin screw vessels. But this used to
be a useful manoeuvring trick.

Note that the effect is in the same direction as the burst
of ahead; ie, full left rudder yaws the vessel to the left
in either fwd or reverse (no 'suction' effect). And note
that I was talking about props sheltered from prop walk -
either through their depth, the use of shields or a lateral
offset.

JimB

Single screw .... With full left rudder, kick ahead, bow will swing to
port .... due mainly to rudder and some prop walk (right hand prop).
With rudder hard left, kick astern, stern will swing to port .... all
prop walk, has nothing to due with rudder placement(rudder could be hard
left or hard right, initial affect will be the same).
The only way to shield a prop from prop walk, that I know of is a Kort
Nozzle or similar shield.

otn

JimB wrote:


Note that the effect is in the same direction as the burst
of ahead; ie, full left rudder yaws the vessel to the left
in either fwd or reverse (no 'suction' effect). And note
that I was talking about props sheltered from prop walk -
either through their depth, the use of shields or a lateral
offset.

JimB

Single screw .... With full left rudder, kick ahead, bow will swing to
port .... due mainly to rudder and some prop walk (right hand prop).
With rudder hard left, kick astern, stern will swing to port .... all
prop walk, has nothing to due with rudder placement(rudder could be hard
left or hard right, initial affect will be the same).

true.


otn

JimB wrote:


Note that the effect is in the same direction as the burst
of ahead; ie, full left rudder yaws the vessel to the left
in either fwd or reverse (no 'suction' effect). And note
that I was talking about props sheltered from prop walk -
either through their depth, the use of shields or a lateral
offset.

JimB