Folding Propeller Problems - SailNet Community

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  #1  
Old 05-21-2008
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Folding Propeller Problems

I'm having intermittent problems with my 2-blade folding propeller. Details below. Please let me know if you have any thoughts or have experienced anything similar.

Summary of Propeller Issue
-----------------------------
Problem: The 2-blade folding propeller works sometimes, but intermittently dies out - either failing completely or giving very little thrust (like 0.5 knot) even with high RPM.

Current status: My yard has examined the boat. They believe that a small, foreign, object has been catching in the gearing and preventing the prop from opening. They are disassembling, cleaning, and reasssembling the prop.

The yard believes that the prop has been getting stuck after opening about 1/4 inch. They think it is an intermittent problem because the "sticking" has been caused by a small object (like a metal shaving or fragment) getting caught in the gearing. Since the object moves around, it doesn't always cause the sticking. That is the theory that best seems to explain the observed behavior.

Some of the other possible causes that the yard considered were:
- Transmission slippage
- The prop closes too tightly and doesn't easily open again.
- A hub problem.
- A keyway problem
- Saildrive cone clutch problem.

These causes seem unlikely to the yard because when they hauled the boat, they were able to grab the prop by hand and turn the engine over. All linkages seemed to be tight.

Some Concerns: I'd like to believe that the "cleaning" will solve the problem. However, I am a bit uncomfortable because the "small foreign object theory" doesn't account for two observations:
(1) The prop has failed a few times when shifting from forward to reverse. Also, I don't think it explains how the prop was working as we headed out to the start or a race recently, but stopped working about 10 minutes before the start. I suppose that it is possible that in these situations, I have temporarily put the transmission in neutral (while raising sails), which caused the prop rotation to stop. If the prop then closed up, due to the motion of the boat, when I shifted out of neutral, the "foreign object" may have lodged in the gearing and prevented the prop from opening. But could the prop actually close during the process of shifting from forward to reverse - when the time spent in neutral may have been at most a second or two?
(2) The prop seems to always work when the engine is first started at the mooring or dock. Why doesn't the "foreign object" ever cause problems at these times?

Chronology of Prop Problems
-------------------------------
1) My yard installed a Flex-O-Fold 2-blade folding racing prop this winter.
2) The prop seemed to work OK during the delivery from the yard to my yacht club on April 12th.
3) In late April, started to notice that, at certain times, we seemed to lose power, even though the engine was running at high RPM. This problem was more pronounced in reverse. Power always came right back, so didn't pay much attention. Figured that we were just getting used to the new racing propeller.
4) In early May, almost crashed into the yacht club work dock because didn't get any reverse "bite". Started to get concerned, but figured that I just needed to learn some tricks for getting the propeller from forward to reverse.
5) A mechanic checked propeller and engine on the mooring. Everything seems fine - noted a powerful prop wash was being generated. Transmission seemed fine.
6) First race of the season - going out to start, propulsion starts to fail. We had very little power on the starting line. After the race, we barely had enough power to get back to mooring.
7) A diver checks out the propeller underwater and says that everything looks fine, but had some comments about a "catch" point, where slight resistance to opening was encountered, when prop was 1/4 inch open. His opinion was, however, that the centrifugal force on the blades, when prop was put in gear, would easily overcome that "catch".
8) While testing storm sails this past weekend with crew, the propulsion completely died on the way back to mooring. We had to sail into the mooring.
9) Today, some crew attempted to delivery the boat from its mooring to the yard. Although the propeller initially had "bite", as soon as they got off the mooring, it failed and they barely got back on to the mooring.
10) Boat is now at the yard. Prop works fine during tests at the dock (of course!). When hauled out, they notice the "catch" at 1/4/ inch.
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Old 05-21-2008
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Are you giving it full throttle then settling back? It takes quite a bit of grab from the prop to unfeather...

So in other words you have to give high burst to open - then low throttle and gradually increase to engage it...

And are you properly feathering it according the manufacturer. ON mine the max prop I have to pull it into reverse - some are forward..

It may be more operator related as it gets all confusing as all get out as it is a behavior totally different from a fixed prop...
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Yes - I have tried giving it full throttle to open it up. Sometimes, nothing works. Also, other drivers - one who is a professional sailor - has experienced the same difficulties.

Oh, and it is a folding prop - not feathering. A flex-o-fold 2 blade racing prop.
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Check the entire prop mechanism against play. Some play should be normal and easily handled by a perfect teeth shape. But if mechanism was hit by debris modifying the sensible teeth surface or natural ware overtime, even a minimal play on the axis would make that catch harder in certain positions. I see little chance to fix it. Replace your prop,
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Old 05-21-2008
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I have a Martec folder. The two blades are not geared together like some others (not sure about the Flex-O-Fold). Sometimes one blade will open but the other won't. A quick shift into reverse then into forward (at low RPMs of course) will open both blades.
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