PabloPicasso
Well-Known Member
what is the difference between a feathering and folding prop? and please don't say one feathers and the other folds...
feather or fold
- Thread starter PabloPicasso
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jimi
Well-Known Member
one feathers and the other folds...
DaveS
Well-Known Member
jimi
Well-Known Member
Feather aligns blade with water flow reducing drag, folding collapses thus reducing drag
PabloPicasso
Well-Known Member
well done you smart donkeys and thanks for the real answer 
webcraft
Well-Known Member
.
Folding is cheaper and probably less likely to go wrong, but is not quite as good astern in most cases.
- W
Folding is cheaper and probably less likely to go wrong, but is not quite as good astern in most cases.
- W
wiggy
Well-Known Member
Folding is generally mechanically simpler and requires less maintenance/less likely to go wrong
Tranona
Well-Known Member
Serious answer. Up til about 10 years ago the distinction (functionally) was much more clear. Folders were relatively simple 2 bladed affairs most commonly used on smaller sailing/racing boats where low drag was important and performance under power less important. Feathering props are more sophisticated and allowed 3 or even 4 blades. More appropriate for larger cruising boats where performance under power was important but lower drag when sailing was a bonus. Think 40' bluewater cruisers - and boats where the cost becomes small in relation to overall costs.
Over the last 10 years or so there have been many developments. 3 and even 4 bladed folding props are available, even in large sizes, so some boats that previously had feathering props now have folders. Equally low(er) cost alternative featherers such as the Kiwi and Featherstream have come along which are more suitable for smaller boats. overall motoring performance has also improved with new blade designs and some designs have variable pitch.
The upshot is that the choice has become greater, differences in performance have blurred, but there is still enough to suugest a careful evaluation of the pros and cons of each design is necessary.
Over the last 10 years or so there have been many developments. 3 and even 4 bladed folding props are available, even in large sizes, so some boats that previously had feathering props now have folders. Equally low(er) cost alternative featherers such as the Kiwi and Featherstream have come along which are more suitable for smaller boats. overall motoring performance has also improved with new blade designs and some designs have variable pitch.
The upshot is that the choice has become greater, differences in performance have blurred, but there is still enough to suugest a careful evaluation of the pros and cons of each design is necessary.
Sans Bateau
Well-Known Member
For sailing get a folder, if you do a lot of reversing it has to be a Kiwi.
ianj99
Well-Known Member
For sailing get a folder, if you do a lot of reversing it has to be a Kiwi.
+1
forelle541
Well-Known Member
I have just fitted a Flexofold 2 blade to my boat and the difference is astounding compared to the fixed three blade that it replaced. Loads more grip on the water forward and astern.
andygc
Well-Known Member
It depends on the boat and the water. My long-keeler has a hole for the prop between keel and rudder which happily take a Darglow Featherstream, but could never take a folding prop. I though of a Kiwi for all the good reasons - cost, easy blade replacement - but my trusted local marine engineer advised very firmly against it because his experience was that the Kiwi did not cope with the silt in the Exe. As for going astern - a long-keeler is awkward enough going backwards without the handicap of a prop that is designed only to work properly going ahead.
forelle541
Well-Known Member
Yes it was the silt on the Deben that prompted me against a Kiwi prop, and the discounts offered by Flexofold but it is good.
Ridax
Well-Known Member
Also note that the Kiwi prop blade profiles are swept a lot backwards when feathered so they take much more space than the Darglow Featherstream. I also have a long keeler and the Kiwi of proper size wouldn't fit while the Featherstream fit perfectly.
DaveS
Well-Known Member
I can understand your point about silt, but the above bit is just wrong. As a number of others have pointed out, the Kiwi's performance in reverse is excellent. A statement like yours was made in the YM propeller test article, but the writer had failed to understand how the Kiwi works. In fact the blades swing round so that the same leading edge is used both in ahead and astern.
Sailfree
Well-Known Member
Fom a previous post :-
1. Folding - least sailing resistance of all
-poor power astern
- on most boats worth an extra 1/2 to 3/4 knot when sailing
2. Feathering- slightly more resistance than folding.
- more power astern than even a fixed prop (blades reverse direction for max efficiency). For most boats/engines will stop a boat in astern in its own boat length from 6kts.
- again worth an extra 1/2 to 3/4 kts when sailing
3. Bruntons Autoprop initially need more wellie to get power astern. I was also not keen on the amount of bearings exposed to salt water/marine growth. This prop has considerable advantages if considering doing a lot of motorsailing.
4. Fixed - has shaped blades for maximum forward power
- has less power astern as "shape" is inefficient in reverse direction and hence can be good for creating prop walk astern!
- has maximum drag and rope catching ability
- on a number of modern gearboxes locking prop in astern (for minimal drag when sailing) stresses gearboxs and locks it in astern - need to start engine in astern - not possible on USA spec boats - starter only works in Neutral!
I prefer a feathering prop. Of these
a) Kiwi prop looked good reasonable price and would be of interest except maximum power handling ability. Plastic blades hence cheapness but for small boats I would have seriously considered them. Can adjust forwards pitch from outside but not astern pitch which is fixed at very coarse which for some people/boats can be a problem.
b) Aquastream interesting as in stainless steel and warranteed for 5 yrs but one of dearest. Can adjust pitch from outside both forwards and astern.
c) Maxiprop- good but cannot adjust pitch from outside and needs to be assembled and pitch adjusted when installed - quite dear and for heavy use needs an even dearer larger hub option.
d) Variprop - Can adjust pitch from outside, already assembled slides straight on, has a 2,3 or 4 blade option for larger engines. has an internal cushion effect for when going forwards to astern and vice versa. cheaper than the maxiprop & Aquastream
My decision - having checked the market I decided the variprop was technically superior although was tempted with the SS aquaprop meaning no dissimilar metals on shaft. I had bought a Variprop before on my previous boat and was happy with it. "
I have a 75hp engine and used the Jeanneau standard 3 bladed fixed prop for 1 yr and have now used a 4 bladed variprop feathering prop for 6 yrs I would buy the same one again with all its advantages - especially the max power going astern (on the putty or berthing too fast!) and the only one disadvantage that forward top speed is very slightly down over the shaped bladed fixed prop.
I still have a hardly used feathering Variprop suitable for a 40HP saildrive 38' yacht if anyone is interested -wrongly returned (and checked/polished) by manufacturer when Volvo initially refused to accept that it was their gearbox that was faulty!! One replacement prop later - new Volvo gearbox!!
1. Folding - least sailing resistance of all
-poor power astern
- on most boats worth an extra 1/2 to 3/4 knot when sailing
2. Feathering- slightly more resistance than folding.
- more power astern than even a fixed prop (blades reverse direction for max efficiency). For most boats/engines will stop a boat in astern in its own boat length from 6kts.
- again worth an extra 1/2 to 3/4 kts when sailing
3. Bruntons Autoprop initially need more wellie to get power astern. I was also not keen on the amount of bearings exposed to salt water/marine growth. This prop has considerable advantages if considering doing a lot of motorsailing.
4. Fixed - has shaped blades for maximum forward power
- has less power astern as "shape" is inefficient in reverse direction and hence can be good for creating prop walk astern!
- has maximum drag and rope catching ability
- on a number of modern gearboxes locking prop in astern (for minimal drag when sailing) stresses gearboxs and locks it in astern - need to start engine in astern - not possible on USA spec boats - starter only works in Neutral!
I prefer a feathering prop. Of these
a) Kiwi prop looked good reasonable price and would be of interest except maximum power handling ability. Plastic blades hence cheapness but for small boats I would have seriously considered them. Can adjust forwards pitch from outside but not astern pitch which is fixed at very coarse which for some people/boats can be a problem.
b) Aquastream interesting as in stainless steel and warranteed for 5 yrs but one of dearest. Can adjust pitch from outside both forwards and astern.
c) Maxiprop- good but cannot adjust pitch from outside and needs to be assembled and pitch adjusted when installed - quite dear and for heavy use needs an even dearer larger hub option.
d) Variprop - Can adjust pitch from outside, already assembled slides straight on, has a 2,3 or 4 blade option for larger engines. has an internal cushion effect for when going forwards to astern and vice versa. cheaper than the maxiprop & Aquastream
My decision - having checked the market I decided the variprop was technically superior although was tempted with the SS aquaprop meaning no dissimilar metals on shaft. I had bought a Variprop before on my previous boat and was happy with it. "
I have a 75hp engine and used the Jeanneau standard 3 bladed fixed prop for 1 yr and have now used a 4 bladed variprop feathering prop for 6 yrs I would buy the same one again with all its advantages - especially the max power going astern (on the putty or berthing too fast!) and the only one disadvantage that forward top speed is very slightly down over the shaped bladed fixed prop.
I still have a hardly used feathering Variprop suitable for a 40HP saildrive 38' yacht if anyone is interested -wrongly returned (and checked/polished) by manufacturer when Volvo initially refused to accept that it was their gearbox that was faulty!! One replacement prop later - new Volvo gearbox!!
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andygc
Well-Known Member
Sorry, a misunderstanding - my point about reversing followed from Galadriel's post #9 - I don't do a lot of reversing, but when I do I want it to work - so a folder would not be much use to me. The Featherstream also uses the same leading edge both ways.
Sans Bateau
Well-Known Member
It does make me chuckle a bit when people talk about how great a Kiwi is at reversing. My main concerns when buying a prop, are 1. How does it cope in reducing friction when sailing (it is a sailing boat after all) folder: 10/10 . 2. does it do a good job in driving the boat forward. (Flexofold) sometimes I need to motor and when I do It want to be able to motor at the highest speed with the lowest revs. Folder: 10/10. 3. Every now and again, (2% of boat use?) I need to reverse, does my prop go in reverse? Yes 10/10 (A folder is not the best in the world, but you'll get used to it)
So if you are using your boat for sailing with some motor sailing, you want good value, you dont want complicated mechanics, get a folder! If however, you do a lot of going backwards a Kiwi may just be the answer.
So if you are using your boat for sailing with some motor sailing, you want good value, you dont want complicated mechanics, get a folder! If however, you do a lot of going backwards a Kiwi may just be the answer.
Ridax
Well-Known Member
I just don't see what your 10/10 means. Do you mean the folder scores 10 points out of 10 at doing reverse? The folder is neither a tenner at doing forwards nor backwards. You seem to give it 10/10 just on the pure fact that it is is able to do reverse at all. With the same logic you can give any feathering propeller the same scores. Reducing drag 10/10, forward 10/10 and backward 10/10.
Sans Bateau
Well-Known Member
You got it. You cannot reduce the drag by any more so 10 out 0f 10. A good modern folder will propel the boat at hull speed, so again 10 out of 10. I never go far in reverse, into or out of a berth perhaps? How far do you want to go in reverse? A folder does the job, it works, why give it anything less than 10 out of 10? It does the job.