feathering and folding propellors - opinions

[Skysail]

I too am very please with Gori - in addition to sailing speed, fuel economy has improved. Replaced small anode every 2 years so far.

I am inclined to agree the OPs problem is cavitation, based on a friend's experience.

 

[snooks]

Respectfully I might suggest that the vibration you're feeling when going into high rev reverse is cavitation. Prop killer.

It might well be cavitation, but the vibration was far worse with a 2 bladed props than the 3 bladed props we tested

 

[Bosun Higgs]

I am inclined to agree the OPs problem is cavitation, based on a friend's experience.

You may well be right - thats what the Brunton man thought. Either way, the boat has a grp stern tube of no great thickness so I have to do something about the vibes.

 

[snooks]

Just heard back from the writer, he only made notes of those which had noticeable vibration going forwards....Sorry

 

[Bosun Higgs]

Thanks anyway. From what you have already said it sounds as if a 3 blader would be better so I'll see what owners of the same boat use.

 

[richardbrennan]

I changed my two bladed fixed prop for a three bladed folding Volvo prop some years ago and have been very pleased with it. Performance in forwards and reverse is probably better than with the fixed two blade and although it is difficult to estimate acurately, I reckon I get at least an extra half knot when sailing in lighter airs. I looked at a wide variety before making up my mind, and if money were no object I would probably have gone for the Brunton as it has the "overdrive" feature when motorsailing. However, I do little of this and it was nearly twice the price of the Volvo.

 

[BelleSerene]

I replaced a fixed two blade prop with a 3 blade Kiwiprop and have used it for a season.

Results are: no rumbling noise as the shaft no longer rotates at 5kn+, Greater propwalk in both fwd and rev.

And I hope greater fuel efficiency under motor. And I hope less drag when sailing (although both these I've not been able to measure and prove)

I did this same over the winter. Delighted with the results. Do find greater propwalk (probably just because of greater power in reverse throwing the water up against the hull); but the greater traction in reverse (than a conventional propeller) means you get way on sooner so regain control. Result of this is (a) better stopping power and (b) more useful propwalk for turning on a sixpence.

Oh - and contrary to a couple of very informed warnings I received, she does great speed ahead under power, and of course better speed under sail. A very effective use of £845 + VAT.

 

[dt4134]

I've a feathering prop that came with my cruising boat. It reverses pitch so there are definitely cogs etc in there. You've to be even more gentle than normal going from ahead to astern as there's a big clunk whenever you engage gear as the blades reverse pitch.

Other than that no worries. There's some prop kick in astern but enough to be useful rather than excessive.

Not caught anything on it yet whilst sailing. It's no good for hanging your jacket on when out of the water so I hope it would shrug off debris just as effectively when in the water.

 

[sailorman]

Currently got a Radice folder which vibrates like a road drill if I put it into reverse when going forward. They all do that says the agent, and true there is nothing much apparently wrong with it. So maybe I need to replace with a better brand.

Would be interested in hearing about people's experiences of other makes, both folders and featherers, particularly if they have changed ove from ( say) a fixed prop and can give a comparison of performance.

Boat is used for both cruising and racing so a fixed prop is out of the question.

i have a 2 blade MaxProp prol 20 yrs old with some wear,but not excessive & when greased up it tightens up with no play at all. i would certainly have another one

 

[TradewindSailor]

I have two 3-bladed 15" Maxprops. These are excellent bits of kit. Mine are the standard model which requires the two half-shells to be removed in order to change the pitch. I've done this underwater in 40 minutes. No problem ...... but do arrange something to catch any dropped bits.

I can see one problem. If the body is not kept pressed full of grease, marine worms, etc can grow inside and create calcium deposits which could dramatically increase the internal wear when they become mixed with the grease. I did dive on a Maxprop that must have had very little grease left inside : the blades were very sloppy.

Of course you must keep the anodes in good order too.

 

[AntarcticPilot]

I've got a folding two blade prop on my Moody 31; don't know what kind, as I didn't fit it. The engine is a Volvo 2003, with standard reversing gearbox. I am thinking of changing it because although it normally works fine, on occasion it fails to open when put in reverse. Then the only solution is to put it in forward for a moment, then in reverse again - scary when manoeuvring! The mechanism is fine - the prop was only installed the year I bought her, in 2007 - and out of the water everything works very smoothly. It just seems that the combination of water forces and perhaps the lower revs of the reverse gear mean it doesn't always open properly. And yes, we have repeatedly checked for plastic bags round the prop and so on - it happens when everything is fine.

 

[Marsupial]

Its all about levers

I agree that a small folding or feathering prop COULD have difficulty deploying, its all about the blade length and leverage on the gears, the larger they get the more force they can exert. Cetainly have no probs with my 19inch but can see that 12inch or less COULD be an issue.

 

[AntarcticPilot]

I agree that a small folding or feathering prop COULD have difficulty deploying, its all about the blade length and leverage on the gears, the larger they get the more force they can exert. Cetainly have no probs with my 19inch but can see that 12inch or less COULD be an issue.

Yes, it is about 12". Never a problem in forward; it's just reverse.

 

[Tranona]

Yes, it is about 12". Never a problem in forward; it's just reverse.

I hope it is bigger than 12 inch. More likely to be 15 or 16.

What you describe is a common problem with some folders.

 

[AntarcticPilot]

I hope it is bigger than 12 inch. More likely to be 15 or 16.

What you describe is a common problem with some folders.

I'm only guessing from memory! It works fine in forward, and usually works fine in reverse, so however big it is, it's big enough I've no plans to go swimming just to measure it - there's snow forecast this weekend - just as I plan on going up for week aboard!

 

[gardenshed]

folding props: all need to be spun around to open them up, so if going forward, the flow of water is working against you and you often need a fair bust of power to open it up (usually accompanied with a fair old clunk) and then it will work. Benefit: cheaper to buy, simpler mechanism than a featherer marginally less drag
Feathering props: better inital bite in reverse, ability to adjust pitch to better match your engine/boat
I strip and re-grease my maxprop every year and am happy with the performance.
If it ever fails, I'll go for another 3-blade feathering prop but would speak to bruntons and darglow before a final decision as my 26 yo maxprop may have been overtaken by newer technologies.

 

[murraynorth]

Having recently read on the Catalac forum the data on tests of locking a propellor or letting it freewheel with amazing results in favour of drag reduction by freewheeling has made me wonder why nobody has thought to rig up a car alternator (or two on a catamaran) via properly ratio pulley v belt system wired in tandem to the engine alternator electrics.
OK, most solar and wind generators are great for trickle charging batteries, but the towing water type of generator are very expensive, but the need for decent amperage on ocean passages does require frequent engine use.
Working on the principle that we try all manner of expensive folding prop to reduce drag, whilst not thinking that a freewheeling prop as an efficient turbine which could be used to generate a lot of free electricity, certainly enough to power on board electronics/fridge and auto pilot?
Any thoughts on this OR has anyone actually tried to do this?

Just a note of caution on allowing props to freewheel, on my Volvo engine/gearbox combination, the gearbox oil is only pumped through the gearbox when the engine is running, so freewheeling the prop when sailing is definitely not a good idea!

 

[murraynorth]

Currently got a Radice folder which vibrates like a road drill if I put it into reverse when going forward. They all do that says the agent, and true there is nothing much apparently wrong with it. So maybe I need to replace with a better brand.

Would be interested in hearing about people's experiences of other makes, both folders and featherers, particularly if they have changed ove from ( say) a fixed prop and can give a comparison of performance.

Boat is used for both cruising and racing so a fixed prop is out of the question.

I use a maxprop on my Najad 440 - no propwalk in reverse and same thrust in reverse and ahead - brilliant. Only downsides are it is tricky to get it to stop freewheeling without recourse to reverse gear after stopping the engine and the prop anode is poorly designed - the screws are too close to the outer perimeter of the anode which leads to anode replacement at 75%. Agree with previous comments on necessity to keep grease topped up to reduce wear.

 

[snooks]

folding props: all need to be spun around to open them up, so if going forward, the flow of water is working against you and you often need a fair bust of power to open it up (usually accompanied with a fair old clunk) and then it will work.

That might have been the case many years ago, but all the pros we tested (may 09 issue of YM) would open in forwards and reverse in tick over..We know because we had a Scubar underwater video camera on loan for the test so we could see what was happening under the water

 

[BlueChip]

That might have been the case many years ago, but all the pros we tested (may 09 issue of YM) would open in forwards and reverse in tick over..We know because we had a Scubar underwater video camera on loan for the test so we could see what was happening under the water

I agree with that, my 40hp Yanmar and 3 bladed flexofold will drive our boat at a knot or so at tickover forward or reverse. Never had any clunks or vibrations either. When the blades get fouled at the end of the season performance falls off and there is a change in the noise - a bit like cavitation which I suppose it is.