FOLDING PROP - worthwhile for a heavy displacement long keeler?

Scotty_Tradewind

Scotty_Tradewind

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As many will know the trade-off for superb seagoing and comfort in a boat like a Tradewind is reduced speed through the water.

I have a rudder which encloses the prop. Does anyone reckon I would gain any appreciable worthwhile boat speed by fitting the only type, a

KIWI type, folding prop on instead of my fixed blade prop? Other folding types would not work in the space available

I'm thinking of any trip over 6-8 hours, but especially over a day or two.

S.
 
Yes. Try sailing along and towing a bucket. Then bring the bucket in and see how much faster you go. It'll be a similar difference.

As far as heavy and long keels go my boat is hard to beat but I reckon the feathering prop gives me at least an extra half knot if not more. You'll notice it more in light airs.
 
Hi Scotty, why not an SPW Varifold prop? 3 feathering blades, fits nicely in the aperture on Pleiades, even gives room for a disc line cutter.
Robin
Pleiades of Birdham
MXWQ5
 
I had a Rustler 36, similar keel prop config. We swapped from a three bladed fixed to a three bladed feathering prop. We did a lot of flat water testing and concluded the average speed increase was half a knot in our cruising range of around 5 knots when motoring, and the increase when sailing in the four to five knot range was just under half a knot.
 
Scotty, I don't disagree in principle with what others have said but there is a law of deminishing return. I have sailed everything from a Plymouth Oyster Boat (old gaffer to you) to a light catamaran. Fitting a folder to the 12 tonne gaffer to try and get better sailing performance in local gaffer races did nothing but reduce perormance under power. On the cat however it made a tremendous difference. You have a skeg hung rudder on a fairly heavy long keeler in a rudder cavity. In this case you might possibly get a marginal improvement, you might not, but you also might find your slow speed manouvering in confined spaces, especially in reverse, is even worse than it probably is already. Proceed with caution!
 
Definitely worth it, particularly for longer passages under sail. As already suggested typically.5 knot in the 5-6 knots range. Motoring performance probably a bit better. Suggest you look at the Darglow Featherstream. Shorter than most so fits in easily into your aperture. Adjustable pitch in both forward and reverse to fine tune for your needs. Competitively priced.
 
Tranona said:
Definitely worth it, particularly for longer passages under sail. As already suggested typically.5 knot in the 5-6 knots range. Motoring performance probably a bit better. Suggest you look at the Darglow Featherstream. Shorter than most so fits in easily into your aperture. Adjustable pitch in both forward and reverse to fine tune for your needs. Competitively priced.
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Spoke to the Featherstream guys at SIBS for exactly the same reason the OP has suggested and by coincidence for a Tradewind 35. They said the best solution from their range would be the 4 bladed Featherstream for this application. For longer passages, I think you would see a big difference. Our Tradewind throws a huuuuuuuge three bladed fixed prop which provides plenty of bite at low revs but I assume is knocking a fair bit off the top sailing speed. It would be interesting to see any anecdotal evidence from Tradewind applications.
 
Scotty_Tradewind said:
As many will know the trade-off for superb seagoing and comfort in a boat like a Tradewind is reduced speed through the water.

I have a rudder which encloses the prop. Does anyone reckon I would gain any appreciable worthwhile boat speed by fitting the only type, a

KIWI type, folding prop on instead of my fixed blade prop? Other folding types would not work in the space available

I'm thinking of any trip over 6-8 hours, but especially over a day or two.

S.
Click to expand...

Whilst you'll certainly have less drag, it's unlikely on a long-keeler with an attached rudder, you'll have the space in which the blades can fold behind the prop-boss.
For this reason you'd be more likely to be able to fit a feathering prop (which the Kiwi is).
I note that your description has led others to answer your misleading question.

Whilst great in theory it's a matter of careful measurement to see if there is sufficient room and clearance to fit anything but a fixed propellor.
 
I have a Kiwi prop and although I cannot comment on how it will benefit your boat, one thing you will experience is the Kiwi gives much more thrust in reverse than a traditional prop due to the configuration of the blades.
 
savageseadog said:
The boat will actually sail better too, due to the reduced turbulence over the rudder.
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Interesting, I have noticed we suffer some turbulence over the rudder that you can feel through the steering when motoring. I suspected that it was related to the big 3 blader we have (incidentally, a much bigger prop than any other similar sized boats in the yard).
 
We sail a heavy long keeler. Big prop, the boat was previously used as a shrimp trawler.
After sailing on some modern yachts and cats I wanted to do something about the light air performance of our old boat.
Testing with a precision towing log showed a ½ kn increase in sailing speed with the prop stopped in the right position. This position was found by braking the coupling and marking the position on witch the prop gave the least torque. Dozens of tests gave the exact position. At longer sailing passages the prop shaft is now fixed in that position. Better for the hydraulic gearbox anyway.
Taking our rigid dingy on deck ads an other ½ knot.
Good clean hull made a difference as well ( Coppercoat )
From 10 knots of wind the boat sails its hull speed, then we can tow lots of dingy´s.
A feathering prop, sure it will help, to expensive for us.
 
Thats the whole point of having a 2 blade fixed prop innit? Stop it in the vertical position and it is effectively out of the stream. Don't see how a feathering or folding prop gives you half a knot better in that case, but I recognise that several on here think it does. Now that OP has said he has a 3 blader I can see how that would be different though. Most heavy displacement boats I have owned with long keels (that's 4 actually) have had 2 bladers. Not as efficient I grant you but stopping in the vertical position and setting the shaft brake is probably as good as a folder I would have thought and they don't require any maintenance other than cleaning now and then...
 
Tranona said:
Definitely worth it, particularly for longer passages under sail. As already suggested typically.5 knot in the 5-6 knots range. Motoring performance probably a bit better. Suggest you look at the Darglow Featherstream. Shorter than most so fits in easily into your aperture. Adjustable pitch in both forward and reverse to fine tune for your needs. Competitively priced.
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Would agree but I use a 3bladed Kiwi 17" on my 10t long keel steel ketch. .5kt faster cruising at the same 2000rpm compared to the fixed blade 17" prop, and the Kiwis larger astern pitch is better for slowing down. (prop walk is a bit worse going astern as a result)
Go for it.
 
The Contessa 32 class tend to fit the Darglow because of the limited room available, might be worth looking at. Probably expensive.

I have seen a number of close quarter clumps blamed on tricky props failing to open. So, for that reason, I will not be investing.
 
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boatmike said:
Thats the whole point of having a 2 blade fixed prop innit? Stop it in the vertical position and it is effectively out of the stream. Don't see how a feathering or folding prop gives you half a knot better in that case, but I recognise that several on here think it does. Now that OP has said he has a 3 blader I can see how that would be different though. Most heavy displacement boats I have owned with long keels (that's 4 actually) have had 2 bladers. Not as efficient I grant you but stopping in the vertical position and setting the shaft brake is probably as good as a folder I would have thought and they don't require any maintenance other than cleaning now and then...
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Perhaps depends on the chord of the prop blades and the shape of the keel?
If the prop is in some sort of vortex anyway, it might do less harm than behind a nicely faired keel.

Under most racing handicap systems, you can get a significant allowance for having a fixed prop, but everybody still seems to go for folding or feathering.
Even a quarter of a knot is a lot if you are cruising in company, let alone racing.
 
lw395 said:
Even a quarter of a knot is a lot if you are cruising in company, let alone racing.
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yes we've noticed how true that is.... our friends should not be as quick as us by a long way in their LM30.... After going down to St Malo alongside them this last summer I wondered why we couldn't shake them off our stern..... discovered they always motor sail!!

Dreadful habit!!

S.
 
Tranona said:
Definitely worth it, particularly for longer passages under sail. As already suggested typically.5 knot in the 5-6 knots range. Motoring performance probably a bit better. Suggest you look at the Darglow Featherstream. Shorter than most so fits in easily into your aperture. Adjustable pitch in both forward and reverse to fine tune for your needs. Competitively priced.
Click to expand...

That's the only one which will fit the aperture on my boat. One day I'll have the money ...
 
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