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2 blade folding prop, which one?


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4 hours ago, Wright Way said:

Bought 2 flexofold 2 bladers now for two different yachts, shaft and saildrive. Would buy another without hesitation, probably wouldn't consider anything else.

Price, performance, service could not be faulted.

Seems like “flip a coin” then…

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7 hours ago, Raz'r said:

Seems like “flip a coin” then…

Had Flex-o-fold on previous boat, Gori on the one prior to that.  As long as they're appropriate size/pitch for the engine, I'd agree it's "flip a coin".

New boat has a J-Prop feathering three blade, now that's a different kettle of fish...

Cheers!

 

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flexofold hands down. I've got two, they have low drag and excellent motoring performance. Also, price is pretty decent.

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I had a saildrive Gori fall apart in Samoa -- the prop apparently had things to do in the abyss but left the hub behind. It took Gori weeks to get back to my email and their answer was "we've been on vacation and here's our price list". I'd already contacted FF and organized new props at that point. I found performance indistinguishable. I think the design and machining is a little nicer on the FFs. The service was better. N=1. YMMV.

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I was at the same decision point about 6 years ago. Wanted to change from an undersized Martec to a newer style geared folder. Was leaning towards Flex-O-Fold but went to the Annapolis boat show and talked to Martec, Flex-O-Fold, and Gori.

Martec guys were great and answered all my questions. Guy from AB Marine who is the US rep for Gori was great and took a lot of time explaining the prop and even compared it to their other offerings while his booth was really busy. Flex-O-Fold guy could be barely bothered to talk to me even with an empty booth. His pitch was, Flex-O-Fold is the best, and I should buy it. 

I bought the Gori and I've been very happy with it. It was a big improvement over the undersized Martec. A properly sized Martec would probably have been a big improvement too. I'm sure I would have been happy with the Flex-O-Fold as well, I just couldn't bring myself to give that guy any business. 

One of the benefits for the Gori (that I didn't need to take advantage of) is if your recommended tip clearance is close to a standard size but not quite there, they can machine the blade down a bit to get optimum clearance instead of just going down to the next standard size. Something to do with the blade design allows for this. 

A downside to the geared folder that I've found is if there is if you get any hard growth in the gears it will open, but it might not fold back under sail. A quick dive to cycle the blades back and forth will clear it, but it's something to think about. 

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I looked at the FOF in the above link and note two things: one, the shaft nut assembly is covered which would preclude the fouling issues I experience; and two, FOF have a bushing which cushions the prop as it slams open. Those are IMO nice touches.

As for fouling in the gear meshing assembly, that is somewhat mitigated by assuring the props are closed when not in use. In fact the closed position seems to help with the blade fouling as well.

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4 hours ago, Max Rockatansky said:

As for fouling in the gear meshing assembly, that is somewhat mitigated by assuring the props are closed when not in use. In fact the closed position seems to help with the blade fouling as well.

Sure, but how do you do that? Dive on the boat after each sail to manually close the prop? Unfortunately that just isn't practical for most users. If your marina even allows you to dive on your boat in the slip, which many don't. 

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4 hours ago, Slick470 said:

Sure, but how do you do that? Dive on the boat after each sail to manually close the prop? Unfortunately that just isn't practical for most users. If your marina even allows you to dive on your boat in the slip, which many don't. 

I just reach mine with the boathook, but i'm damned if i'd be in a marina that wouldnt allow me to dive my own boat. I've never heard of such a thing

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14 minutes ago, Max Rockatansky said:

I just reach mine with the boathook, but i'm damned if i'd be in a marina that wouldnt allow me to dive my own boat. I've never heard of such a thing

I'm pretty sure that it's common around here. Ours allows it, but the larger marinas next door do not, supposedly due to liability concerns. Our water is so murky that you can't see much in the slip and have a little better chance of seeing what you are doing at anchor.

Not sure if I could tell if I succeeded in folding the prop with a boat hook. I'd be just kind of stabbing around by feel. 

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On 11/15/2021 at 10:13 AM, Slick470 said:

Sure, but how do you do that? Dive on the boat after each sail to manually close the prop? Unfortunately that just isn't practical for most users. If your marina even allows you to dive on your boat in the slip, which many don't. 

honestly I've never had a problem with fouling keeping the blades from functioning properly. One of my props this year was propspeed and the other was interlux spray-on antifoul. the funny thing on the interlux boat was that the engine was out of the boat for about 2 months and we sailed the boat anyway, but in 5 years with the FoF I've never had a fouling issue.

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10 hours ago, ryley said:

honestly I've never had a problem with fouling keeping the blades from functioning properly. One of my props this year was propspeed and the other was interlux spray-on antifoul. the funny thing on the interlux boat was that the engine was out of the boat for about 2 months and we sailed the boat anyway, but in 5 years with the FoF I've never had a fouling issue.

We've had some bad seasons with hard growth here on the Chesapeake. I also probably don't always use my boat enough. Those two things combined and I've had the occasional issue and figured it would be worth mentioning. Still way better than needing to set the prop on the Martec or having one blade not come out. 

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We bought a FoF 2-blade for our 36' cruiser.  They sent the wrong pitch and we had to send it back (factory took responsibility and were very good about it), but in any case it created a lot of vibration compared to the fixed two-blade it replaced.  We decided to upgrade to the 3-blade FoF to fix the vibration and that solved it - though it was an expensive upgrade.  Later I found an article that explained why two blade props often vibrate in the turbulence created by the keel.  It doesn't happen with every boat.

Both were/are works of art.  We didn't want to put the boat in the water, we wanted to just leave it on the hard so we could admire the prop.  

If you get the two-blade and are unlucky like us and it vibrates, consider upgrading to the three-blade.

One FoF advantage: they are very popular making it easy to find replacement zincs.  When I went to the marine store to get one this fall they had a dozen in stock.

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On 11/21/2021 at 4:22 AM, inneedofadvice said:

Better? Cheaper? What made you choose it?

J35 and Martec have a long history together. So I contacted Gary and he told me SeaHawk does their manufacturing of new props.  So I ordered. 

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On 11/23/2021 at 3:44 PM, gkny said:

Is there anyone who refurbishes the FlexoFold props? 

what kind of refurbishing? you can get spare parts easily and they come apart with minimal tools. Any company that polishes props should be able to work on the blades. If you are worried about refurbishing these like you would a max prop, you'll be pleasantly surprised that they are far less complex.

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  • 3 weeks later...

I am also looking at a folding prop this winter and would like to replace my 2 blade fixed with a 2 blade Flex-O-Fold.

Any thoughts on vibriation or any other concerns? Owning a fixed 2 blade, I understand there will probably be some vibration. There appears to be some good reviews on this thread for FOF.

Thanks

Patrick

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Tim who owns Prime Time, the Olson 40, swears by Brunton Autoprop. He powered 8+ knots while I went 6.3 with my old elliptical Martec. Same Yanmar engines. Remarkable performance under power.

I am getting one soon. Step by step improving my drive line so I can hopefully measure effects of each change. I can’t use a folding prop and regenerate electricity.

Aqua drive first, as switch from packing gland to dripless shaft seal led to shaft instability.

Once shaft works properly and hopefully reduces friction and noise, I’ll switch props.

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23 hours ago, pcoe said:

I am also looking at a folding prop this winter and would like to replace my 2 blade fixed with a 2 blade Flex-O-Fold.

Any thoughts on vibriation or any other concerns? Owning a fixed 2 blade, I understand there will probably be some vibration. There appears to be some good reviews on this thread for FOF.

Thanks

Patrick

no vibrations from the prop, with the caveat that on my 3 blade that's how I know it's not fully open is that it vibrates a little bit. a little burst of power and it's fully open. I don't expect you'll notice any vibration at all.

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2 hours ago, carcrash said:

I can’t use a folding prop and regenerate electricity.

can you explain how an auto feathering prop would allow you to regenerate electricity?

It seems like you'd need something like the Mastervolt servoprop which can be controlled via software to put the prop at the appropriate pitch to generate power (as opposed to being fully feathered for efficient sailing). 

Or you could add a dedicated hydrogenerator, which to me seems like the best way to make sure your prop is the most efficient for sailing and motoring, and your regeneration is as efficient as it can be to generate power. In fact you could be generating power while you're motoring.

I'm just curious, crash - you seem to have a pretty good handle on your projects, and I'm only asking out of curiosity. 

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I borrowed a friends spare AutoProp and fitted to just one shaft of a 50' catamaran that had Electric Wheel motors running off battery back and single diesel generator. The original props were Michigan standard square 16" three blade props. The AutoProp was perfect on that boat and I begged the owner to buy a pair so I could return the loaner. I could center the steering and then advance the throttles on each engine until the boat was tracking straight and then compare the amp draw on each motor. The standard three blade used about 30% more current to keep up with the AutoProp. Doing the same in reverse and the AutoProp was even way more effective since it wasn't working with the cupped blade backward. The biggest surprise was that the AutoProp had no problem regenerating even though it is still a mystery to me what kept the blades open while being dragged forward through the water. Biggest problem was that it regenerated so much current it was easy to overcharge the battery bank! You could stop that by careful adjustment using the little joystick throttle to control the field current and slow the prop rotation down. Something that you couldn't do with the fixed prop! The drag on the AutoProp at really slow sailing speed when there wasn't enough flow past the blades to fold it up was really the only negative thing about the AutoProp but was still less that the fixed 3 blade.

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Rasp that's really interesting about the regeneration on an autoprop. So it sounds like a decent solution for an electric system. However, it also points to why a folding prop is better for pure performance, if the feathering prop still has enough drag to be able to overcharge a battery bank! Still, that kind of regen keeps systems simpler, not having to to add a separate hydro leg. thanks for the info.

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An 'Autoprop' never fully feathers/folds. The pivot is well off the blade, so there is always an attack angle on the blades. To align the blade to water flow you would have to rotate the blade INTO the water flow

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Longy, the blade will find the least angle of attack. essentially neutral if you have the means to lock the shaft. So that would be equivalent to feathered. No way that configuration could be called folded though. What is interesting is to get into the water with a mask on and have someone shift from fwd to reverse and watch the blades do their rotation thing! The blades have always looked like a seagull with a broken wing to me though...

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Exactly what I was talking about. The guy narrating the video is a genius. He has worked for Bruton forever as a propellor engineer and is now the marketing guy in N. America. He knows exactly what he is talking about when it comes to props but now he has to try and represent as many of his manufacturers as possible and doesn't really go out on a limb on what to recommend but I think if you really pinned him down he would tell you the AutoProp is really the sweet point.

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It is the offset of the pivot point from the center of pressure of the blade that makes the Autoprop work. It will adopt an angle of attack relative the the local flow at the pivot axis. Local flow at the pivot axis is nearly circular around the hub (and nearly 90 deg to the shaft) when it is spinning, and nearly parallel to the shaft when still. It has to be looked at from the blade's reference frame.

So it does feather when the shaft is locked, but not to zero angle of attack and will cause some drag due to that - in excess of a truly feathering prop - but far less than a fixed one. 

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On 12/12/2021 at 12:58 PM, ryley said:

can you explain how an auto feathering prop would allow you to regenerate electricity?

It seems like you'd need something like the Mastervolt servoprop which can be controlled via software to put the prop at the appropriate pitch to generate power (as opposed to being fully feathered for efficient sailing). 

Or you could add a dedicated hydrogenerator, which to me seems like the best way to make sure your prop is the most efficient for sailing and motoring, and your regeneration is as efficient as it can be to generate power. In fact you could be generating power while you're motoring.

I'm just curious, crash - you seem to have a pretty good handle on your projects, and I'm only asking out of curiosity. 

Fixed, feathering, folding, auto prop. 4 different types.

MaxProp is a feathering prop. When the shaft is not moving, the blades all become parallel with the shaft. If the shaft is at an angle, as is typical, then the blades are not really minimum drag. On race boats, one uses a two blade and you must ensure the blades are vertical to achieve minimum drag.

With a feathering prop connected to an electric motor, you put the motor in reverse, and the blades will stay in that orientation as the electric motor is put into regeneration mode, and the prop will spin quite well. All feathering props are less than optimal when spinning of course, as they all lack any twist. But they do work well to regenerate (force the motor to turn).

With an autoprop, Ras22 has explained it very well.

An autoprop is more drag when not in use than a folding or feathering, due to two things. The hub is much larger, and, as mentioned, the blades do maintain a bit of angle of attack. 3 and 4 (and hypothetically 5) blade auto props may be less drag than folding and feathering. The feathering prop drag might be more because the non-vertical blades will have some angle of attack unless there is zero shaft angle to flow, which never happens.

But the autoprop is still pretty darn low drag. I would never use one on a GP race boat. But people have found them to work very well on slow speed powerboats, where the automatic optimization of pitch is a big advantage.

I am hoping to see the same results as Ras22 did with the electric wheel catamaran. Randy told me about those experiments at the time, so I have been intrigued for quite some time.

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2 hours ago, carcrash said:

Fixed, feathering, folding, auto prop. 4 different types.

MaxProp is a feathering prop. When the shaft is not moving, the blades all become parallel with the shaft. If the shaft is at an angle, as is typical, then the blades are not really minimum drag. On race boats, one uses a two blade and you must ensure the blades are vertical to achieve minimum drag.

With a feathering prop connected to an electric motor, you put the motor in reverse, and the blades will stay in that orientation as the electric motor is put into regeneration mode, and the prop will spin quite well. All feathering props are less than optimal when spinning of course, as they all lack any twist. But they do work well to regenerate (force the motor to turn).

With an autoprop, Ras22 has explained it very well.

An autoprop is more drag when not in use than a folding or feathering, due to two things. The hub is much larger, and, as mentioned, the blades do maintain a bit of angle of attack. 3 and 4 (and hypothetically 5) blade auto props may be less drag than folding and feathering. The feathering prop drag might be more because the non-vertical blades will have some angle of attack unless there is zero shaft angle to flow, which never happens.

But the autoprop is still pretty darn low drag. I would never use one on a GP race boat. But people have found them to work very well on slow speed powerboats, where the automatic optimization of pitch is a big advantage.

I am hoping to see the same results as Ras22 did with the electric wheel catamaran. Randy told me about those experiments at the time, so I have been intrigued for quite some time.

Wait until you hear the rest of the story crash!!!

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3 hours ago, carcrash said:

The feathering prop drag might be more because the non-vertical blades will have some angle of attack unless there is zero shaft angle to flow, which never happens.

It pretty much does happen, on a saildrive. 

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  • 3 weeks later...

well my new to me Cal 40 from 1966 has always had a Martec folder from the dealer. I am 3hrd owner and thought well crap. I  was impressed how well it pushed the boat , even has more reverse than expected with the Grey Marine 4 112 gas engine. Think I will keep both and the pressurized alcohol Shipmate oven

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On 1/1/2022 at 11:15 PM, Oh Sheet said:

and the pressurized alcohol Shipmate oven

OMG DOOM AND UNMITIGATED FAILURE

 

(next you'll tell us you have an offset companionway!)

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