Rudders and centerboard while motoring

[TimKat]

Hello all you happy Mac owners:I am a beginner boat owner and sailor, but getting better as the summer wears on. I have found it hard to keep the boat on course on Lake Erie, where it can sometimes feel like we're in a big bath tub with all the wakes coming at us and choppy seas. I have motored with the rudders down and the centerboard in about 18" and it seems to help quite a bit, but I am worried that I might be hurting the boat. My US Sailing instructor thought that the stress the centerboard undergoes while under sail is pretty intense, so he didn't see where it would hurt it while motoring. The rudders are another story. Those have to be tied off, locked in the down position and I'm afraid that might be too much stress on the mounts. Any opinions? Forgive me for my ignorance, but my experience reading these tells me Mac owners are a special, forgiving and helpful bunch! Thanks in advance.

 

[Ray18680]

Motoring

I have a 05 26M and the owners manual says that you should not have the daggerboard down at a speed above 6mph. I have found that at speeds lower than that I need to lower the daggerboard about a foot and lower at leat one rudder in order to have reasonable control.

 

[JonBill]

Roll Right Over

The main problem with motoring while the dagger board is down on a 26M or X is that the dagger board operated in this condition acts like a wing on a plane. It creates lift. If it's down more than a couple of feet and you hit the throttle full open, the boat will roll right over. The reason for this is the dagger board is trying to climb right out of the water due to the lift and because its attached to the keel it simply rolls the boat over. Slow speeds and/or a few inches of dagger board down and the affect is not that great so it doesn't matter that much. But the faster you go and the lower the dagger board the greater the roll affect.If you don't believe this will happen (that the boat will roll over) then experiment with it a little and you'll prove it the hard way. If you do plan to experiment then leave the kids and wife at the dock and keep your hand on the throttle so you can back off the throttle before you roll over.Hopefully if you don't create too much momentum you'll recover as your speed decreases and the boat will right itself hopefully before you roll over.As far as having the rudders down while motoring the problem here is that it creates too much force on the steering mechanism and will stip them out or break the cord. The wheel works on the principle of leverage created by a large wheel (the wheel you turn in the cockpit) being moved a further distance to pull a smaller wheel inside a shorter distance or radius but with a multiple of the force. The problem is that the force placed on the rudders with the boat going at higher motor speeds while you turn the wheel exceeds the capacity the system is designed for. Read any sailing magazine and every few issues someone will write a story about rudder failure. The reason is the high leverage ratio which can be as high as 80:1 ratio in some wheel steering with a multiplying affect from wheel to gears to rudder. In this scenario the force of 1 pound on the outside of the wheel to make it turn creats 80 pounds of force that is transfered to the rudder to move it through whatever its resisting it (usually water at slow speeds). I don't know specifically the ratio of the steering mechanism on the M or X but its got to be at least 30 or 40:1. The problem is the force on the rudder caused by the water squares as a function of speed. So the faster you go and try to turn the rudder the much greater the force on the steering mechanism. At some point something breaks and you have rudder or a steering mechanism failure. The rudders and steering mechanism are designed for the forces associated with sailing speeds not motoring speeds.Kind Regards,JonBill