Feathering vs Folding Prop

[reed1v]

Practical Sailor had several research articles on this issue.

[Cheechako]

Originally Posted by hoppy

I don't understand the big deal about reverse

If you have a prop that means stopping distance is longer, learn your boat and understand when you need to start reversing or perhaps give it more revs.

I think it's better to get a prop that allows you to travel forward faster or the same speed with less revs and accelerates better so that when you are motoring into some chop you lose less speed. After all most of us probably motor forward 99.9% of the time and reverse the other 0.01%

I'm happy with my Flexofold 3B as it does all of that.

If you don't understand it, Not sure I can help you much. Try steering and stopping (if you can steer!) into a dock with 5 knots current going with you into the slip. Report back.

[CarlF]

Never had a problem with my 3 blade Flexofold giving me immediate and powerful reverse. Not once.

I think most problems come from the wrong size or pitch prop. Don't under-prop or over-prop. Ask the prop manufacturer to try and find you a reference from the same type boat with the same engine/transmission. If they are happy, copy them.

[malbert73]

Had a 4 blade variprop on my old boat. Great in reverse, instant thrust in FWD, nice to be able to adjust pitch. On current boat, went with 3 blade flexofold which to me was no brainer as I felt the loss of top end FWD efficiency at cruising speed with feathering. And the thing is bulletproof- no grease, etc. and much better when sailing around pots, kelp, etc as all that slides off.

Basically, you can have low price, FWD efficiency, reverse efficiency, low drag. Cannot have all 4 IMO.
So flexofold maximizes all but reverse which is merely adequate. Counter with higher revs. Good every once in a while to clean out cylinders 😀
If you live somewhere where you must dock in 5 knots of current as someone said above, move or get a mooring. I really don't know any sailboat that could actually do that realistically so I assume hyperbole?

But if reverse is highly important go feathering- then you will give up some FWD efficiency due to flat blades of feathering prop.


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[01kiwijohn]

My boat is a fin keel, spade rudder, as is yours. I too like to sail most of the time. I added a 3 blade, feathering,Kiwiprop about 5 years ago and cruise about 5 months per year. It has plastic blades, which will break off if you snag something really hard (as I did) and avoid other drive train damage, fewer moving parts, mechanical part are stainless and it is easy to fine tune the pitch in the water. Goes into max pitch astern, but you'll get used to that after a while. Servicing is easier than most others. I'd highly recommend it.

[hoppy]

Originally Posted by Cheechako

If you don't understand it, Not sure I can help you much. Try steering and stopping (if you can steer!) into a dock with 5 knots current going with you into the slip. Report back.

Why post up a seriously stupid example???

So you will charge into the dock at 6 or 7 knots to maintain steerage? And slam it in reverse and hope? I wouldn't be wanting to do that with a prop designed to work best in reverse.

I'd just reverse into the slip, motoring forward through the water at 4 knots so that I'm going 1 knot backwards.

Again, given that none of the modern props in that test barni linked to are bad in reverse, I don't see the point of worrying about reverse and think it's better to chose your prop based on forward speed and price.

A few times I've had to med moor into a town quay with a 20 knot cross breeze. To be able to keep the boat reasonably straight and aim so a gap between two yachts, I have to keep a reasonable speed in reverse. It's only bravery, not prop performance of my low ranking in reverse that has limited my reverse speed causing me to abort.




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[hoppy]

Originally Posted by hoppy

Again, given that none of the modern props in that test barni linked to are bad in reverse, I don't see the point of worrying about reverse and think it's better to chose your prop based on forward speed and price.

From the article

"On the other hand, with astern performance, in general it was the feathering props that came out best, with better bollard pull than the standard, and better stopping times, and the Autostream coming out top. The folding props were generally not as good as the standard, though in the main only by no more than 10%.
"

[reed1v]

If you must drive in reverse, get a three blade prop. That will limit you to a feathering prop.

[fstbttms]

Originally Posted by reed1v

If you must drive in reverse, get a three blade prop. That will limit you to a feathering prop.

Umm... no it won't.

Gori



Flex-O-Fold



Slipstream



etc., etc.

[hoppy]

Originally Posted by reed1v

If you must drive in reverse, get a three blade prop. That will limit you to a feathering prop.

I have 3 blades that fold, not limited to feathering

[roberthowell]

check out kiwi props not savvy enough to to embed the link they are feathering 3 bladed ( composite blades ) 1/2 the price of all others and spare blades are only 100 dollars so must more thrust in both directions that my 2 bladed folding

[hoppy]

Originally Posted by roberthowell

check out kiwi props not savvy enough to to embed the link they are feathering 3 bladed ( composite blades ) 1/2 the price of all others and spare blades are only 100 dollars so must more thrust in both directions that my 2 bladed folding

I considered Kiwi when I changed my prop but the performance seems to be pretty poor in the YM test. I kind of think that if you are cruising which can mean extended motoring, it's better to wait until you can afford a better prop. Kiwi props seem to me to be better suited to day sailing locally where you mostly just motor to get in and out of your marina.


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[01kiwijohn]

I am not aware of any tests that show a drastically inferior performance for the Kiwiprop. They do have some horsepower limitations, on their web site, so you may need to consider that. There are also some hull shapes that seem to inhibit performance too.
My experience has been very satisfactory and it pushes along at hull speed without duress.

[hoppy]

Originally Posted by 01kiwijohn

I am not aware of any tests that show a drastically inferior performance for the Kiwiprop. They do have some horsepower limitations, on their web site, so you may need to consider that. There are also some hull shapes that seem to inhibit performance too.

My experience has been very satisfactory and it pushes along at hull speed without duress.

See the YM test linked to by Barnicle. The Kiwi prop has a top speed that is around half a knot slower than the fixed prop and 0.65 less than the best in the test. Whilst you don't race around at top speed, it does mean that it will be less economical to achieve the same speeds because you need higher revs and this translates to a shorter range.


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[01kiwijohn]

Actually, not necessarily. The load on the engine, not the rpm, will have more of an effect on the fuel consumption. Thus the need to adjust the pitch to attain 95% (approx) of max idle rpm at full speed underway. More than that = lost potential, less than = too much continuous load.