Outdrive steering at slow speed.

[johnhill]

I've a 640 with outdrive used mainly on the Trent and connected rivers.

Has anyone with a similar installation fitted an auxiliary rudder extension, as seen frequently on outboard motors? /forums/images/graemlins/cool.gif

 

[bdsweeting]

One tip I was given for slow speed handling was to lower the trim tabs, if you have them - of course, the extra drag help to stop the boat wandering so much.

 

[bruce]

wandering is normal on a single outdrive boat, can be corrected by installing a propguard that incases the prop and directs energy only forward or reverse

 

[duncan]

If you get back to basics you will find that there is basicaly only one solution..........
the 'wandering' is primarily caused by the relationship between the hull and thrust - basically on an OB and OD boat and a planning hull this is that the thrust is from behind the hull and the hull doesn't have any lateral grip on the water (at slow displacement speed) so turning the wheel redirects the thrust and simple tries to make the whole thing slew........
(here we see why putting tabs full down will work to a degree as they will create a couple of points around which the thrust force can act - but they are on the trailing edge of the hull just in front of the drive so very inefficient.)
It follows that the ideal solution would be a small keel as close to the bow as possible, even a small skeg will do a great job; you will see these on ski boats often in conjunction with a shaft and rudder and these things track as if on rails!
In practice though the real answer is to minimise your use of of the wheel because of where the force is acting. Adding a rudder to the skeg of the drive, or anything else there is not going to make any difference - your thrust is already vectored but it's moving the stern not the bow.
Practice hard and always use a rear wheel steer trolley in the DIY store as it's got the same problems............ /forums/images/graemlins/laugh.gif