Flexofold vibration

[keeljoy]

I replaced by fixed three blade propeller with the flex-i-fold 2 blade folding with a 10 degree pitch. The thrust is fine, not a lot of loss of speed, but tremndous vibration? Its a concern

[colemj]

We are casually looking at new folding props and I was doing some research on FOF. It seems like there are a lot of complaints about vibration with the 2-blade versions. The 3-blade doesn't seem to have the same complaints. If this is very new, I would get FOF involved and not settle for anything less than no vibration at all.

Mark

[JPA Cate]

Have a look at the engine mounts, the shaft alignment, play in cutlass bearing. Our 3 blade FOF has never had a vibration problem. The suggestion above, to involve them, is a good one, we found them easy to work with.

Ann

[Jim Cate]

How much tip clearance between prop blade and the hull? If inadequate, this can lead to severe vibration, and perhaps you went up in diameter to compensate for only having two blades.

Jim

[keeljoy]

It's the same clearance as the fixed three blade...

[keeljoy]

OK..so I went to Flexofold. We had quite a discussion They said they had never had a vibration problem in this kind of mount. I shared the pictures with them We talked about whether the key was set properly. I called my divers. They not only assured me that the key was in properly, but that its had been one of the better installations they had had in some time. So in the conversation, we discussed the fact that the flexofold has considerably more noticeable thrust than the three blade it replaced. The thought is now that engine alignment, mounts and shelf alignment may be the culprit, with the increased thrust forcing the engine to torque more.

.

[colemj]

All of that could be true, but if you search the web you will find several examples of people with the FOF 2-blade complaining about vibration.

Mark

[sailorboy1]

does it vibrate all the time at steady load, or maintaining when increasing the rpms?

[keeljoy]

All the time under steady load

[svHyLyte]

Originally Posted by keeljoy

All the time under steady load

There are set-screws in the hub that are intended to lock the shafts of the pins about which the blades rotate in place. If the set screws have loosened, the pins rotate with the blades, which should not happen. If so, however, the prop will vibrate like crazy, which, of course, will wear our your prop, and cutlass bearing very quickly and may damage your shaft log. We dealt with this problem for awhile but to put it to rest, we finally had the set screw holes bored out one size and used the larger screws with Lock-Tite and the issue was resolved.

FWIW...

[keeljoy]

We just installed it on Thursday...this was the first time out so it would be weird to lose the set screws...especially when the divers were so complementary of the fit.

[svHyLyte]

Originally Posted by keeljoy

We just installed it on Thursday...this was the first time out so it would be weird to lose the set screws...especially when the divers were so complementary of the fit.

It would not be weird for the set screws to loosen with an underwater install. Nor would it be weird for the pins to not have been positioned properly so that the "dimples" the conical shaped ends of the set screws are supposed engage were/are, in fact, properly and fully engaged. Working under water can be very problematic and is not wise where a certain degree of precision is required. N'any case, we have offered you information based upon our own and other yachts experience. Whether you chose to use it or not.....

[keeljoy]

I appreciate the contribution :-) And it helps me do due diligence
. Thanks for your thoughts.

[fstbttms]

Originally Posted by svHyLyte

There are set-screws in the hub that are intended to lock the shafts of the pins about which the blades rotate in place. If the set screws have loosened, the pins rotate with the blades, which should not happen. If so, however, the prop will vibrate like crazy, which, of course, will wear our your prop, and cutlass bearing very quickly and may damage your shaft log.

Pivot pin rotation is not possible in current Flex-O-Fold props. The pivot pins are notched to accept the locking screw and barring the loss of the screw, will not move.

Originally Posted by svHyLyte

Working under water can be very problematic and is not wise where a certain degree of precision is required.

Said the guy who has never done it before...

https://www.youtube.com/watch?v=2q3ntQF_Csk

https://www.youtube.com/watch?v=y3WaOWestWQ

[Weyalan]

We installed a Flexofold 3-blade folding prop. Never had any vibration issues. In fact significantly less vibration than our old Autostream 2-blade feathering prop