Not easy to figure out.
Hello Bruce,Vibration is not an easy thing to pin point in any situation. We often find that one thing compounds many other problems. So removing or eliminating one area may not seem to be helping. I would like to make a statement that all in all folders work to there potential and that in no way am I slamming Matec or Flexofold. Regardless of which kind of folding propeller you have, the system is working on centrifugal force to open and hold the blades into an open position. When you add angle to the propeller shaft the loading of the blades becomes different between the two. If you imagine a clock face, as the 12:00 blade is advancing downward it is increasing in load because it is being presented to the flow of the water being presented to it by the movement of the boat. Just the opposite is taking place with the 6:00 blade, as it raises its loosing or reducing in load. Add this to blades that move independent of each other and one further increases the discrepancy between the blade loadings. The greater the angle the greater the load discrepancies can be. Switch back to a fixed blade and the loads are starting to balance out again. If we add a third blade we then begin to transfer or distribute the difference in loading over greater surface areas, thus helping to reduce the whipping in the shaft. Keep in mind that the new fixed is not any anyway perfect, its just that the supporting items like engine mounts, shaft diameter and cutlass bearing are know able to support the rotating propeller. Perfect world for most sailboats would be to have a parallel running shaft to the water line. In your case you may find that the shaft angle may be 8-10 degrees. Some of the older race boats had 15-18 degrees of angle, this created huge noise problems in the boat. To fix the noise you may have to increase support to the running gear. Worst case you may need to consider a fixed blade style propeller. Hope this helps. Kevin