Hi F1M..........knowing little about these fast machines........ but do I see......
1. the propeller is anti clockwise rotation
2. the blade rudder is to the right hand side of the axis of the propeller
Thinking about this....the pressure on each of the three propeller blades is on the leading edge, the lower pressure is then also on the trailing edge of each blade
From this ......should the vessel not have the tendency to turn to Port or the left?......... ....Derek
Hi Derek, the anti-clockwise rotation of the prop (as viewed from the rear), means that the torque transmitted up the shaft to the engine, tries to rotate the boat clockwise (again, as viewed from the rear), causing it to tend to list right, and veer right. Additionally, the paddle wheel effect of the prop in the water, will tend to try and pull the rear end of the boat leftwards - again, causing a tendency to veer right.
Our main friend here is the rudder. The main reason that a right side rudder offset is conventionally used, is because the lift from the rudder helps to lift the right side of the boat, and counteract the natural tendency to list and veer right. Having the trailing edge of the prop roughly level (equidistant respective to the transom), as the leading edge of the rudder, is said to help. I suspect that shortening the transom to prop distance should also help (prop has less leverage on the boat). Having the rudder equidistant, I believe, is meant to help in the sense of the rudder kind of catching the wash thrown off the prop, and re-directing it straight back.
Hi Daz,
Some other things of note (you probably know most of this already, delete as appropriate):
1) Different props react differently. Generally, bigger props, and especially more pitch, cause more problems, but other prop characteristics also have a bearing. Might be worth trying two blade instead of three.
2) Prop again, the sharper the prop, the less likely to give issues.
3) Strut / stinger offset towards the right (a few mm), tends to help (because the strut or stinger also creates lift), but generally not too quick or easy to implement if not already built in. Strut / stinger depth and angle (respective to keel line), can also have a bearing.
4) More rudder blade in the water means more lift on the right of the boat. If you can get the rudder a bit deeper, it should help. More offset too, but the greater the offset, the more it affects left turns, and the longer the rudder needs to be to get the same rudder depth. Can't really see how far your rudder is offset at the moment. General consensus normally suggests an offset in the region of 60ish - 70ish mm.
5) Check carefully for any play or flex in the rudder linkage. A deep vee won't naturally go straight. The rudder is constantly holding it.
6) Similar to above, rudder servo power needs to be adequate; both to hold the boat in a straight line, and pull it back after a right hand turn.
7) I'm still - to some extent, battling this with my C Class, but getting there. My AA boat started to do the same after I raised the rudder to install bigger trim tabs. I fixed it by taking means to get the rudder depth back, and now tends to slightly lean left at speed (due to the rudder lift), but doesn't seem to steer left, presumably because the other factors are counteracting.
Good Luck. Keep us posted.
Ian