PDA

View Full Version : Offset Rudder



Phoenix
11-05-2003, 02:32 AM
HI Guys,
I am replacing the Cav plate on my 17’ Simpkin Clinker Mid-mount Inboard Ski Boat and after reading about offset rudders I need to know the best place for my rudder? :confused:
Should I offset it to one side if so which side and how far? :(

Aramas
11-05-2003, 02:47 AM
Perhaps I'm a bit slow here, but I thought that offset rudders were only used in twin screw installations, unless you include twin rudders for single screws.

What's the point of offsetting a single rudder with a single screw? If it's out of the prop wash it will have to be bigger, and it would make the boat handle differently turning one way than the other.

Any more details?

Phoenix
11-05-2003, 03:30 AM
Hi Aramas,
The info I have read is to offset the rudder in relation to the prop shaft?

“all things being equal having the rudder dead central but in practice for outboard mounted rudders it is far better to have it offset Further to that we found in racing situations an offset rudder made for far superior turning if biased to one side. Most boats used on rivers for example would make the majority of their turns to the left so the rudder would be biased towards the starboard side of the boat.”

Also it allows the prop shaft to be removed without removing the rudder? :confused:

nedL
11-05-2003, 06:49 AM
Phoenix, I believe you are correct about offsetting the rudder if you are planning on racing her competatively. As a true race boat you are always going in a counter clockwise circle, you want to be able to turn left really well & don't care much about the ability to turn right. Offsetting the rudder a bit sometimes helps the left turning. If you are going to be using her as a 'river boat' (for pleasure use) then left & right turning will both be important & I don't think you'd want to offset the rudder. (Does this make any sense?)

Phoenix
11-05-2003, 06:57 AM
Hi Ned,
Yes it does make sense I will mount it centrally thank you for your help smile.gif

nedL
11-05-2003, 07:30 AM
:D

http://www.speedskiffs.com/rucki_js6_flying.jpg

Aramas
11-05-2003, 08:52 AM
lol - I didn't think of racers always going in circles in the same direction - but then I'm like that :D Not a sporting bone in my body.

I can see how it would work well for only turning one way. If the rudder was out of the prop wash but adjacent to it, turning it into the stream would work like a kort nozzle, deflecting the accelerated water. Meanwhile when it was not being used there would be less drag, and of course more speed.

It kind of reminds me of a proa that held the world speed record for a while - it only sailed on one tack :cool:

[ 11-05-2003, 09:57 AM: Message edited by: Aramas ]

Mike Field
11-05-2003, 08:08 PM
.
Except as for the racing requirement, I think I'd be offsetting the rudder to counteract rather than reinforce any prop-walk tendency.
.