Flexofold prop FELL OFF!!

[ErikLP]

Sounds like bad luck. Good that you could make it to a safe mooring. I have had the same 3 bladed Flexofold propeller on a sail drive for 10 years and sailed many nautical miles without any issues. If mounted properly it works like a dream.

[Icarus]

Originally Posted by Lifeonalean

Well I was motoring slowly out of the harbor when all of a sudden I had no propulsion. Was lucky enough to coast to an anchorage and drop anchor. Dove the boat and found the shaft to be completely bare! My issue is, I really liked the flexofold and now I wonder is there a design flaw? Bad installation? Attempted theft maybe? I feel like the installation must have been done right because we just sailed from Seattle to Newport Beach California right after install and motored probably half the way. I would think this would’ve happened sooner? Has anyone ever heard of this with a flexofold? Doesn’t seem possible to lose all of it at once considering how it is put together. Opinions? Advise?

Looks like bad installation, props generally dont come lose unless the nut hasn't been locked and secured properly.
Unless you check the installation your self you would not know if the installation has been done correct.
If the key doesn't fit tight it works the holding nut loose and if the nut hasn't been pinned it eventually comes off and the prop flyes off.
Sorry for your loss.

[tartan4100]

No one has mentioned this yet so....


I've used Flexofold for 20+ years, albeit on a saildrive. One day about 8 years ago, the prop fell off while day sailing. Motor out, sail for several hours, try to motor in. Found prop totally gone. Called TowBoat US. It was about 3 months after a bottom job in which the prop was removed and cleaned, etc BY ME. When I got the new Flexofold, I found they had added a new washer with instructions to tighten the center mounting nut and then bend an edge of the washer up against one of the 6 sides of the big nut as a safety. The washer has a tab or something to keep it from turning. Flexofold must have had issues and created a fix. I was please to know it must have happened before me. So with grease and water crud, Locktite might not be enough. And if I didn't read the instructions to see what the new washer was for, I might have put it in place, but not bent it up against the nut. I ordered a couple of spare washers in case, even though I reused the washer at my next haulout. And for saying this, my prop will fall off again tomorrow.

[barboak]

Why would one want to install an expensive piece of gear like a flex o fold prop underwater if you have any other option! I’d save the diving for an emergency or a zinc change

[fstbttms]

Originally Posted by barboak

Why would one want to install an expensive piece of gear like a flex o fold prop underwater if you have any other option!

Cost and convenience for starters.

[sdj]

Sounds like the loctite set-up real quick and made the nut look "tightened". Gotta watch that.

[GrowleyMonster]

Originally Posted by fstbttms

Did I say it's preferable to install underwater? No, I did not. But there is also no compelling reason to haul a boat to remove or install a prop. Especially when the work is done by an experienced professional. Any inference that an in-water installation is inherently inferior to an installation done on the hard is an inference made in ignorance.

But hey, it's your dime.

I have never hauled one of my boats to change a prop. I even changed a shaft in the water once. And I am not even a professional diver. Usually I have a spare, though, because I did break a blade off, once. (log? sunken bouy? It was pretty dark and I didn't see anything, just felt bumpity thump and then the vibration of a very sick propellor) I would certainly install or replace a prop in the water again, to get home, rather than being the latest Sea Tow poster child.



That said, it would be stupid to not check your prop and shaft and strut and all that stuff, and fix proactively, when hauled out for other reasons.


TBH I never messed with a folding prop in the water. Removed one on the hard once, and had it took me over two hours to get it off. I can't imagine losing it by accident. Seemed to me that the nut was captive to the threaded end while the blades were still attached, and the shaft key prevented the entire prop assembly backing off.


I would make sure that the shaft key is of sufficient dimensions to fill the keyway, though. Too small a shaft key could permit the prop to unscrew itself over time, with vibration and enough astern operation.

[FlyingScot]

I recently installed two composite FoFs on Yanmar saildrives. I ordered extra parts just in case something went wrong or for the next time I have to pull them. I strongly recommend others do the same. One was “tilbehørspose” ‘ accessory bag’. The other was shaft nut with tab washer.
Plus extra anodes.

The composites were difficult to get to full torque on the nut due to flex while using a blade and wood to stop the rotation.

[fstbttms]

Originally Posted by FlyingScot

The composites were difficult to get to full torque on the nut due to flex while using a blade and wood to stop the rotation.

Pro tip- Use a length of rod rigging (or similar) run though the blade pivot holes to immobilize the prop while torquing the nut.

[Old fella]

Originally Posted by fstbttms

Here's the bottom line, as I see it:

There are many, many hundreds of thousands (if not millions) of pleasure craft around the world that have shaft-mounted propellers. Very few (I would venture to guess much less than 1%) have ever had those props lapped. Whether or not this is a best practice, the number of props that are lost in total is very small and the number of those props that are lost due an improper fit on the taper has got to be infinitesimal. A number so small that statistically speaking, lapping is waste of time and effort.

You are dead right mate, lapping in props, I've never heard so much cr@p, I suppose years ago some drongo came up with this brain fart and there is always going to the mugs who believe it.

[Per Weiskvist]

Hello in this forum

One of our clients, emailed us about this thread, so I think it will be good if I place a comment and a few advices, to this issue.

A Flexofold propeller normally dont just fall off. But there are a few things you need to be very aware of :

First of all, if you suddenly feel vibration from the shaft/saildrive, that was not there before, stop immediately and get a propeller check....

To prevent this :

1. The hub taper must fit perfectly, so please make sure to order the right standard taper.
2. The hub is not allowed to ride the key when mounted (you might feel this by some vibrations from the propeller/shaft).
3. By shaft installation, it is VERY important to remember, to fit the little locking screw on the side of the hub, and make sure it locks the nut on one of the flat sides of the socket.
4. By Saildrive installation, it is VERY important, that you fit the locking screw and the tab washer on the nut. and it is VERY important to make sure the tab washer is locking both backwards the locking screw, and forwards the nut, so needs to be bended both ways.

I hope this prevents any other member of this forum, to unfortunately loose a Flexofold performance propeller.

Per Weiskvist
Flexofold Aps
Denmark

[Wotname]

Originally Posted by Per Weiskvist

Hello in this forum

One of our clients, emailed us about this thread, so I think it will be good if I place a comment and a few advices, to this issue.

A Flexofold propeller normally dont just fall off. But there are a few things you need to be very aware of :

First of all, if you suddenly feel vibration from the shaft/saildrive, that was not there before, stop immediately and get a propeller check....

To prevent this :

1. The hub taper must fit perfectly, so please make sure to order the right standard taper.
2. The hub is not allowed to ride the key when mounted (you might feel this by some vibrations from the propeller/shaft).
3. By shaft installation, it is VERY important to remember, to fit the little locking screw on the side of the hub, and make sure it locks the nut on one of the flat sides of the socket.
4. By Saildrive installation, it is VERY important, that you fit the locking screw and the tab washer on the nut. and it is VERY important to make sure the tab washer is locking both backwards the locking screw, and forwards the nut, so needs to be bended both ways.

I hope this prevents any other member of this forum, to unfortunately loose a Flexofold performance propeller.

Per Weiskvist
Flexofold Aps
Denmark

Thanks Per, very helpful.

One question if I may, is there any thread locking fluid needed in step 3?
If so, can this applied underwater?

[Per Weiskvist]

Dear Wotname

The screw used in step 3 is self locking, so it needs no thread locking fluid...

[flyingnut40]

I skipped the last hundred posts TTTR.....
but my take on the thread is this.
Morse tapers are machined to an industry standard and IF the prop is new and IF the shaft is new and properly made the two parts WILL mate with 80 -90% contact and the nut will seat the tapers together with enough contact area that the nut "could" be removed with no consequence.... but you wouldn't. Locktite or set screws are EXTRA insurance that like any bandaid won't work forever. If the prop/ shaft has ANY DEFECT it WILL affect the mating performance of these two parts and machining or lapping or both will be required to get that 80-90% contact. When I am faced with this challenge you can bet that I will be getting some bluing agent or in a pinch a light spray of paint (something!!) And cheching the mating of these surfaces! Lapping is great insurance. Lots of parts are held by Morse Tapers...... like flywheels etc. and virtually Always require a puller to get them to release the "lock" that a proper taper gives.
If there is even the slightest score on either surface then the working of the parts will flatten the defect and you have loose parts. Now you are at the mercy of the bandaid!
Keyways are to locate part orientation and earlier posts are valid. Ket needs to fit tight in shaft and have enough clearance to not impede the 80-90% contact area of the taper. The keyway might drive a go kart axle for a while..... it WILL NOT drive your boat!
Good luck with this! The engineering is sound!
Dennis

[Wotname]

Originally Posted by Old fella

You are dead right mate, lapping in props, I've never heard so much cr@p, I suppose years ago some drongo came up with this brain fart and there is always going to the mugs who believe it.

Hard to know if you are serious or if you are taking the mickey - I understand you are a Kiwi so you are probably taking the mickey.

For anyone who doesn't want to take my unfounded word about the inherent advantages of lapping prop when first fitting to an unknown shaft, work you way though these links from a variety of professionals.

Propeller Fitting Instructions
Lapping Propellers to Shaft | High Seas Yacht Service
https://stevedmarineconsulting.com/p...-installation/
https://www.havelockslipway.co.nz/services/props-shaft
https://www.ashleyriverboatworks.com...-to-the-shaft/
https://www.pressreader.com/usa/soun...81934542718996
https://www.passagemaker.com/technic...pellers-part-2
Marine propeller installation - boat prop instalation
https://henleyspropellers.com/products/shafts/
Keep your prop on - Ocean Navigator - January/February 2003