Folding Propeller that folds in reverse

[Docaroo]

Hi gang.
Just cleaned up 2x folding propellers and coated with propspeed.
Back in the water and now OK in forward but initially open in reverse then fold as revs increase. SD20 saildrive with dog clutch that is engaging.
?? why previously working propeller now not working.
Could we have lightened the blades in our cleanup ??

More to the point how do we fix the problem
Docaroo; current sanity rating withheld

[JPA Cate]

Hi, Docaroo,

Welcome aboard CF. We have one only (monohull) Flex-O-Fold 3 blade prop, and it only closes when the water pressure doesn't hold it open. Maybe what happened with yours is that you went slow enough in reverse that the water pressure from the boat's movement astern caused them to close? This may be crazy as anything, just a thought.

Ann

[Dsanduril]

Just a shot in the dark, do the engines (propellers) rotate the same direction? I think with a saildrive it is pretty rare to get a counter-rotating twin, but... Any chance you swapped the props?

[rom]

Originally Posted by Dsanduril

Just a shot in the dark, do the engines (propellers) rotate the same direction? I think with a saildrive it is pretty rare to get a counter-rotating twin, but... Any chance you swapped the props?

Wouldn't that just perfectly invert forward & reverse gears ? Docaroo says the boat is still fine forward. It is the centrifugal force that keeps the blades open in reverse. I also have two of those nice 3 blades FoF, woring perfectly forward & reverse.

[Docaroo]

Thanks gang
Thanks for your thoughts
We are currently in a marina berth and a little reticent to leave it !!
So the props are closing themselves even when we are stationary.
ie tied up and trying reverse (as well as when mobile; docking was a little entertaining as we discovered the problem).
The props both rotate the same way.
FOF 2 blade props really only mount one way so stuffing that up shouldn'd be the problem (although not discounting it)
So still trying to work out possible causes prior to hauling our little beastie out and fixing it.
All ideas welcome !!
Regards

[Pete7]

Have you seen this:

https://www.youtube.com/watch?v=3_adsflxy8g

[SV Bacchus]

I have MaxProps so I have no experience with the folding props. So many on this thread swear by the FlexFolds that I can't help but think it has to be some type of installation error.

If the prop was disassembled to paint, could it have been reassembled wrong? In other words, assembly is wrong but actual mounting on the boat is correct leading to the confusion as to why it doesn't engage?

[Chuck Hawley]

Sorry that I can't be more helpful in diagnosing this, but I do have to compliment you on your videography. Many diagnostic videos make things more confusing rather than less, and your video is really clear.

Second, can you take any solace in the fact that at least your propeller has low drag when operating in reverse? Perhaps not...

Chuck

[Pete7]

Chuck, sadly not my video, wish it was. I found it a while back whilst thinking about a FOF prop, project now on hold for while.

Pete

[tpkas]

When the prop spins in reverse it generates a force that not only gives power to reverse the boat but will also close the blades. This blade closure is counteracted by the centrifugal force wanting the blades to open. My understanding is that as a result of the balancing of these forces all folding props will fold to some extent when in reverse and why the power available in reverse is not as great as that when the blades are fully open in forward gear. By cleaning the props you may have increased the efficiency of the blade which, when in reverse, will increase its propensity to close. I have just fitted folding props to our boat and there is a reduction in available reverse power which you have to get used to.

[senormechanico]

Apply more power in reverse.

[Jim Cate]

Originally Posted by senormechanico

Apply more power in reverse.

This ^^^^^.

The higher the revs, the more centrifugal force opening the blades. Our FOF three blade does pretty well in reverse, better than other folders we've had, but still not like a good feathering prop. Some tests have shown better bollard pull in R than a standard fixed prop.

Jim

[EWOL Props]

Folding props have this issue in reverse, they push water forward, so as a reaction the blades tend to close, that is why boats with folding props are more difficult in reverse maneuverability
Now why this was not happening before cleaning them ? I am scratching my head on this...
I believe that probably before cleaning the blades were a bit more stiff than now due to fouling or incrustations, now that they are cleaned and have less friction on movements, hence water pressure now wins against friction of blades pushing them to close.

[rom]

Originally Posted by senormechanico

Apply more power in reverse.

Hopefully there is something wrong elsewhere because I would be very unhappy if that is the normal behaviour of 2 blades FoF. My 3 blades FoF pull me real good in reverse at idle, 800 RPM Yanmar 4JH4.


I have no idea why it used to work and does not work anymore. Docaroo, did you try to contact FoF directly ?

[Docaroo]

Right-t-ho me hearties
A solid days work and I have the problem worked out
The prop blades have been on a diet;
Prob spinning in sand and mud has knocked some weight off.
As they stay open by centripetal force that loss of weight
was enough to lose the effect.

Took blades off; added 60gm of weight (the stick on stuff used by tyre places when balancing wheel rims)
Bingo the props stay open in reverse

So new prop blades is the answer !!!
Regards Docaroo