max prop vs autoprop (long)
Let me try....max props use a fairly flat blade (s) mounted in a geared hub.when in forward, they work much like a fixed prop but with less efficiency because the flat blades are not as efficient as the typical curved blades. the curved blades on a fixed prop maintain even water speed over the blades-the tips move faster thru the water so they need less pitch than the inner part of the blade-when you put the prop in reverse the hub rotates the blades so they work more efficiently in reverse than a std prop.when placed in reverse and shut down, the blades feather. good point-the gearing forces the blades into position, where a folding prop a blade can stick. bad part, the prop's leading edge becomes the trailing edge in reverse, not optimal. the geared hub needs to be lubed periodically, and comes in two versions-the cheaper one needs to be disassembled to adjust the pitch of the prop, the more expensive version can be adjusted in the water.well proven and reliable.the autoprop is a british design, also well proven and reliable, used on many large ships it uses a solid hub with large ball bearing races holding L shaped blades that swivel freely. the blades are curved (pitch varies along the blade)so it is very efficient. in forward, the blades swivel to get the best pitch forward for whatever you're doing (more in a moment). When you go into reverse, the blades flip around to give the best pitch in reverse-and the leading edge is still leading so the prop is very efficient in reverse, too! with the engine stopped under sail, the water flowing by the blades holds them feathered for low drag. The net effect is very high efficiency in forward and reverse, very low drag under sail, and very good acceleration. the pitch of the prop is determined by the relationship of engine rpms to water speed past the prop, so pitch increases at low boat speeds for better acceleration, then decreases as you get up to speed. While I haven't done 0-6 times, the acceleration is substantially better than my old 3 blade fixed. this is a great feature fighting into a headwind or sea, or if you are towing. Also, it enhances maneuvering and backing. Hard numbers: under sail, gained 3/4-1kt from the prop change. Under power, used to reach 7kts at 3400rpm, now at 2700 rpm. Only maintenance is annual greasing of the bearings thru grease fittings-can even be done under water.go to their website (autoprop.com) and watch the video of the prop in action-my words don't do it justice