On Mon, Jun 2, 2008 at 7:09 PM, Callum M0MCX <[EMAIL PROTECTED]> wrote: > New boat, new prop with slight-to-moderate rudder judder from tick-over > upwards. > > How can I cure this? Ask builder to change prop?
Could be anything, but there is a small chance that the prop is just to close to the rudder. Cheers, Mike I agree with Mike's other suggestions but there is also the possibility that the prop is too close to the sternpost, especially if the swim does not come to a sharp point. Check photos of the prop area taken during building - on seagoing vessels there are good clearances between prop and both hull surfaces and rudder to prevent interference, but the restricted space on nbs sometimes means clearances are less than they should be. You can get a feel for how the rudder is balanced by comparing steering effort at different speeds. I have a completely unbalanced rudder which requires fingertip effort at minimum tickover and full strength at full speed. If the effort is light and similar over the speed range, the judder might be due to excess balance area, which might also have made prop and rudder too close together. In reality the forces on the rudder are very considerable at speed, and a balance hides this. Sean
