Prop Walk - Manoeuvering under Power

[Vega1447]

Hi.
I have the original "Combi" transmission system so prop shaft always has
same direction of rotation when engine is turning over.

Am I correct in thinking that there is nonetheless a "prop walk"
(paddlewheel) effect in reverse - though in opposite direction to that
expected as prop direction of rotation is not changed when reversing?

Or is this wishful thinking?

I still find that reversing out of a narrow gap (head to wind usually)
between a finger to port & a wide motor boat to starboard - and with a
rocky breakwater 3 or 4 boat lengths astern - I'm not always certain
which way she will turn.

It seems that the wind on the bow usually pushes bow downwind in
reverse.

I've learned to let the boat go the way she wants. Then do a three-point
turn with plenty of power in forward does the trick.

Any comments from experienced Vega drivers?

All the best,

John
--
John A. Kinsella Ph: +353-61-202148 (Direct)
+353-61-333644 x 2148 (Switch)
Mathematics Dept. e-mail: John.Kinsella@...
University of Limerick FAX: +353-61-334927
IRELAND Web: John Kinsella's Website

 

[stevebirch2002]

Hi John

Join the group. With the combi I dont know anyone that really knows what way
she will turn in astern unless she weathercocks into the wind. Changing to a
conventional prop for better, but not perfect, control...... I have seen
exact control in Holland as many Vegas have the "Help-Rudder" added. This is
a semi-balanced spade rudder added aft of teh prop and used in tandem with
teh main rudder by use of two quadrants and associated fittings.

Cheers

Steve B

 

[Vega1447]

Hi Steve & all.

Yes but..

My main question is whether I am imagining the prop walk effect?

Second question; I expect the help-rudder would have a much greater
effect on steerage in reverse than changing to conventional
transmission?

Third - is there a "kit" for the help-rudder; don't think I saw it on
the VAGB site?

All the best,

John

 

[jvancraaikamp]

Hi guys,

With the combisystem paddlewheel effect is in the same direction in
forward and reverse.
Normally a RH prop will push your stern in forward position to
starboard. In reverse it will push your stern to portside.
A LH prop does the same thing in the opposite way so in forward it
will push your stern to portside.
Since you change with the combi from a LH to RH prop the paddle wheel
effect is in the same direction.
The big advantage of an extra rudder behind your prop is that the
boat starts turning when you thrust water against the rudder with
your prop.Even when the boat has no speed at all.
Now (with teh standard rudder) you need some speed before your rudder
does have any effect. In reverse direction it does not have a better
effect than the standard, but you can stop your boat in reverse and
than correct it when you push it forward since it immediatly responds
to the rudder.
I think that Steve has some connections in Holland where he can order
a set for the helprudder.

Kind regards, Jan van Craaikamp V973

 

[emmajen5]

There is a file devoted to the extra rudder kit with photos, etc. on our Yahoo home page in the files section.

Just as an aside, (although I'm sure some concider this idea heresy) a small bracket mounted auxillary outboard with a tller handle does wonders in manoeuvering the Vega in close quarters. Plus, it's easier and cheaper to install than any extra rudder with the added bonus of providing emergency back up power.

Garry
v. 2427
manoeuvring