Does anyone out there have any experience with controllable pitch propellers? I believe that Hundsted is the leading brand with Sabb a close second. Can anyone comment on real world efficiency differences between CPPs and fixed pitch propellers? Also, what about reliability, resistance to damage, maintenance and repair-ability? I have some experience with variable pitch aircraft propellers but have never operated a powerboat equipped with CPP. On the passagemaker we're designing now we are considering a coaxial arrangement with two engines driving a single shaft. This is not so much for the sake of mechanical redundancy as it is for engine output efficiency. I would like to have 240 plus HP for when conditions are bad but normally we'll require less than 50 HP to run at a V/L of 1.0 at 9 knots and 3 nmpg. Running a 240 HP engine at 20% of output is not a good thing and its better to switch between the two 120 HP engines and put both on-line when needed. With this range of operating speed/output difference a CPP would seem to make sense. On our current boat we always carry a spare shaft and prop. Carrting a spare CPP is likely to be a major expense. Thoughts? Bruce -- ======================================================================= L. Bruce Jones U.S. SUBMARINES, INC. President POSEIDON UNDERSEA RESORTS LLC Tel: 208/687-9057 Fax: 208/441-7478 E-mail: bruce@ussubmarines.com http://ussubs.com http://poseidonresorts.com "Design, engineering and construction of submarines and submersibles" "Submarine related consulting, sales and operations." =======================================================================

At 04:55 PM 1/14/05 -0800, you wrote: >Does anyone out there have any experience with controllable pitch >propellers? I believe that Hundsted is the leading brand with Sabb a close >second. >On the passagemaker we're designing now we are considering a coaxial >arrangement with two engines driving a single shaft. Bruce, I am not aware of ANY twin to single shaft system, anywhere in the world. I checked this out about 3 months ago and came up dry. Anything that might be available is totally obsolete. Ocean Quest in San Diego has such a system, but that boat is a 40? year old Romsdal/Malahide? and the system is no longer available. If you come up with something, I think you will get a LOT of attention. If for no better reason than to lock you up somewhere where you can't do any harm. Frankly, I think it is a pretty good idea. One engine to drive the boat, the other as backup and to provide extra power if needed. Now, if there were only something off the shelf! Mike Capt. Mike Maurice Tualatin(Portland), Oregon