Folders, featherers and fixed

[[3889]]

This is my take on the above prop options:

Folders: Low drag, poor drive, cost less than feathering

Featherers: Lowish drag, good drive, delay in engagement, expensive

Fixed: Good drive, high drag, cheaper

Is any of the above wrong or lacking?

 

[Bobc]

No, other than higher maintenance of folding, and even higher maintenance on feathering.

 

[Leighb]

We have a Featherstream and I would disagree with you "delay in engagement" comment. There has never been any perceptible delay going into gear or from ahead to astern etc. An additional comment is that astern performance is significantly better than the fixed 3 blade that it replaced. Only so far as stopping power is concerned though, there is no change in the unpredictability in direction with a long keeled yacht.

 

[Leighb]

No, other than higher maintenance of folding, and even higher maintenance on feathering.

Agree there is some maintenance. It consists of applying a grease gun annually and replacing the prop anode - admittedly a modest annual extra cost.

 

[Tranona]

No. Folders do not necessarily have to have poor drive. My 2 blade Flex o fold gives virtually identical performance (objectively tested) as the fixed. Latest 3 blade are equally as good as fixed 3 blade. Featherers such as the Featherstream have the advantage that they can be used on boats where a folder is impossible because of lack of clearance. No delay in featherers in my experience, small delay in reverse with a folder.

 

[geem]

Have a Brunton three blade folder. Can't say I have noticed any loss of power. Had to change plastic thrust pads this winter as they were worn flat. Cost about £30. Not sure when I will have to do again. Can't see any other maintenance issues.
Sailing performance is excellent.

 

[flaming]

If cruising a 3 blade folder is a very good bet. Much better drive than a 2 blade fixed, with barely any more drag than a 2 blade folder.

Cost is the only downside.

 

[Neil_Y]

Yep that 's about right...but

I wouldn't say high drag for fixed, some drag and more than a folder/featherer, but in practice the extra drag added to the boat from a fixed prop must be quite small, and when sailing I never noticed any difference. I sailed with a sail drive two bladed fixed and the Volvo folding many miles. I also towed a towed generator and never noticed that slowing us either, the over all drag of the hull/keel must be so much more (maybe I'll get one of the naval architect students who worked for us to work it out)

 

[Georgio]

We have a Featherstream and I would disagree with you "delay in engagement" comment. There has never been any perceptible delay going into gear or from ahead to astern etc. An additional comment is that astern performance is significantly better than the fixed 3 blade that it replaced. Only so far as stopping power is concerned though, there is no change in the unpredictability in direction with a long keeled yacht.

+ 1 I have the same prop and agree entirely.

The only downside over a fixed prop (apart from cost) is that it requires a small amount of maintainence, but 10 mins a year to pump full of grease is not a problem.

 

[dunedin]

Kind of depends on the boat and the usage, as ever.

But on a modern fast/ish boat a fixed prop would be an instant replacement project for me. Out two bladed folder seems fine, and only gets annual polish and anode change. But we never motor sail

 

[lw395]

You could put it that folding props tend to wear out, rather than require maintenance.
A boat designed with a two blade folder in mind will probably not benefit ever so much from a 3 blade.
But if there is not space for a big enough 2 blade, a 3 blade will be superior.
A prop of the right size and pitch is probably more important than type, once the motor is in use.

 

[knuterikt]

This is my take on the above prop options:

Folders: Low drag, poor drive, cost less than feathering

Featherers: Lowish drag, good drive, delay in engagement, expensive

Fixed: Good drive, high drag, cheaper

Is any of the above wrong or lacking?

You can't make such a broad categorization.
Not all folding props are created equal.
- Number of blades makes a difference for performance

It is unfair to compare the performance of a two blade folding to a three blade feathering.

There are different feathering designs
- Some is less expensive that folding props
- Some is slow in engaging when going from forward to astern, but it's not all designs that "flip" the blade when changing direction.

 

[30boat]

My folding Radice two blader is crp in ahead but surprisingly good(for a folder) in reverse.As was said these props wear .There's no maintenance possible on mine other than a bit of grease,that soon washes off.I don't think that my standard fixed two blader will exert so much drag that I would notice.Ok maybe in very light airs but in normal conditions the diference may not be that much.I may fit the fixed prop next year because it really improves motoring performance.

 

[Woodlouse]

Yep that 's about right...but

I wouldn't say high drag for fixed, some drag and more than a folder/featherer, but in practice the extra drag added to the boat from a fixed prop must be quite small, and when sailing I never noticed any difference. I sailed with a sail drive two bladed fixed and the Volvo folding many miles. I also towed a towed generator and never noticed that slowing us either, the over all drag of the hull/keel must be so much more (maybe I'll get one of the naval architect students who worked for us to work it out)

I reckon that the difference made by having a fixed prop is about the same as towing a dinghy. It's light airs performance that the difference makes its self more apparent.

 

[flaming]

Yep that 's about right...but

I wouldn't say high drag for fixed, some drag and more than a folder/featherer, but in practice the extra drag added to the boat from a fixed prop must be quite small, and when sailing I never noticed any difference. I sailed with a sail drive two bladed fixed and the Volvo folding many miles. I also towed a towed generator and never noticed that slowing us either, the over all drag of the hull/keel must be so much more (maybe I'll get one of the naval architect students who worked for us to work it out)

I've told the story before of doing a corporate regatta with Sunsail in light winds, and one boat being completely untouchable - only to discover that their (fixed) prop had fallen off when they fired up the engine to go home. It does make a huge difference, especially in light winds. Plus in heavy wind surfing conditions a fixed prop can cause fairly serious disturbance in front of the rudder, which makes broaching more likely.

 

[rob2]

Wow, now the discussion broadens into the amount of drag from different types and designs of dinghies! ;-)

I had a Darglow folding prop when I bought Mojo and it performed quite well, but needed a good few revs to open in reverse, then throttle back to suit. I changed it for a modern equivalent which doesn't need so much force to open, but otherwise performs about the same. Folders do generally respond faster if you give a burst of power to get them going though and they definitely offer least drag when sailing.

On a previous boat we had a two bladed "sailing" prop originally which performs under power much the same as a folder (narrow blades) but you could feel the difference when you aligned the blades vertically, in line with the keel, to reduce drag under sail - not easy as you have to have one person with their head in the engine box to see the alignment whilst the helm pops her in and out of gear to stop the shaft! When we changed the engine the budget ran out and as the new gearbox reversed the rotation we fitted a three blade fixed with wider blades - someone had it as an ornament on the mantelpiece. Embarassingly good performance under power, cruise speed with the throttle cracked open a touch, but it was like sailing with a sea anchor.

Rob.

 

[[3889]]

OK, thanks, some things to think about. I ask because I have a feathering prop on a recently purchased boat and I find it a lot harder to manoeuvre onto a berth than my last, admittedly 10% smaller, boat with a 2 blade folder. There seems to be a worrying delay between reverse revs going on and way coming off. There also seems a lot more prop-walk. How much is due to different hull configurations and how much down to the prop I can't say. I'd never considered a feathering prop before and wonder if it's worth changing.

 

[Tranona]

Depending on what prop it is you might be able to reset the pitch separately in reverse. If the revs are rising fast but nothing happening it could be too fine pitch. Usually feathering props perform equally well in reverse because the blade shape is the same as in forward.

 

[knuterikt]

OK, thanks, some things to think about. I ask because I have a feathering prop on a recently purchased boat and I find it a lot harder to manoeuvre onto a berth than my last, admittedly 10% smaller, boat with a 2 blade folder. There seems to be a worrying delay between reverse revs going on and way coming off. There also seems a lot more prop-walk. How much is due to different hull configurations and how much down to the prop I can't say. I'd never considered a feathering prop before and wonder if it's worth changing.

It would help if we knew what boat and type of feathering prop you have.

I changed from a two bladed folding prop to a three bladed feathering prop (kiwiprop) on my Beneteau First 38 and would never change back..
I'm still having propwalk but since I get the boat moving aft faster it's less of a problem now.

All single screw boats have propwalk - but the degree is different depending on the hull shape / propeller placement (more so than the propeller design)

Learn to use the propwalk to your advantage, and plan maneuvers so you can live with it.

My boat will move the stern to port when I engage reverse - as a consequence I can do starboard turn sharper than a port turn (by engaging revers for a short while).
So if I need to do a 180° in confined quarters I will always try do a
When going astern I turn to port before engaging reverse so when the rudder get a grip I'm back on the desired "track"

Have found that when I have got the boat to move astern I can put the engine in neutral and just let the rudder steer the boat.
Since there are no prop wash over the rudder when going astern you must get the boat moving before the rudder give you control.
When the boat is moving astern setting the engine i neutral will let the rudder work without interference from the propeller

 

[Woodlouse]

Being a heavy long keeler propwalk is a vital asset to parking and manuvering in tight spaces. Because, as said a feathering prop works as efficiantly in astern the propwalk is reduced. To tackle this I ordered mine so that the pitch in astern is coarser and so less efficient which has kept the propwalk how I like it. The prop is a featherstream and they were more than happy to customise it like that.