has anyone changed from fixed to folding prop with good results?

[SAWDOC]

Hi folks

I have a 3 blade fixed prop on my sail drive. I know the theory that I could gain "up to 1/2 knot" if I changed to folding prop. Has anyone succeeded in gaining this considerable increase in speed and if so could they give details of what they went for?

I would also be interested to hear if anyone found that this type of conversion resulted in any unexpected lack of power issues.

Thanks

 

[Norman_E]

Not really the same because I have shaft drive and changed from a fixed three blade to a feathering Maxprop. It certainly has improved speed in light winds, though I cannot put an accurate figure on it. I do now manage to sail in light winds where I would previously have motored. The change has actually improved motoring because the old prop was undersized. I gained an inch on diameter and about the same on pitch, and motor about half a knot faster at the same engine revs, but the biggest improvement is better thrust astern with less prop walk.

 

[Laurie]

A friend of mine has swapped a fixed 3 blader for a gorgeous Brunton Autoprop. It certainly sails well, but it also made a phenomenal difference when motoring as the blades are constantly self adjusting for optimum pitch as the revs vary. Very impressive.

 

[Dipper]

I changed my fixed two blade Volvo propeller on my 120S saildrive for a Radice two bladed folding propeller. It was probably the best investment I made although the Gori is a better propeller. I used to race and it put me to the front of the fleet. My boat just sails so much better with the folding prop.

Under power there does seem to be a loss of 'bite' especially in lumpy seas but if the seas are lumpy, then the wind is usually blowing so I can sail.

Reverse isn't a problem. On flat water I can go from 4 knots forward speed (in neutral) to a full stop in my boat length (26') although not much happens in the first 10 - 15 feet. I don't understand the argument that reversing is difficult because if you are actually going backwards, the water pressure forces the blades OPEN. It's just the initial delay in flinging the blades open when you are still going forwards that may catch you out. The Radice blades are bronze and very heavy which must help them to fling open.

 

[savageseadog]

Less turbulence on the helm which gives better feel and less prone to broaching too

 

[nimbusgb]

3 bladed fixed bronze prop to a 3 bladed feathering kiwi prop. The difference accelerating out of a tack is very noticeable, we seem to get to hull speed fairly easily too.

Happy with the power, 2000 rpm in flat water gives 6.5 knots with a bit of oomph left for pushing in to any weather.

 

[uxb]

Another happy Kiwi prop owner here.

Can't quantify the increase in performance as I re engined at the same time but definitely a lot more oomph in astern.
The boat also sails a LOT better, but that will mostly be down to th new sails...

 

[reeac]

Not really the same because I have shaft drive and changed from a fixed three blade to a feathering Maxprop. It certainly has improved speed in light winds, though I cannot put an accurate figure on it. I do now manage to sail in light winds where I would previously have motored. The change has actually improved motoring because the old prop was undersized. I gained an inch on diameter and about the same on pitch, and motor about half a knot faster at the same engine revs, but the biggest improvement is better thrust astern with less prop walk.

Presumably astern performance in of some importance only in marinas. I tend to view propwalk as something of an asset - like a stern thruster.

 

[Tranona]

Flexofold 2 blade on a saildrive. Motoring performance same as fixed. Sailing noticeably better, particularly in light airs. Good Value. Speak to Darglow Engineering who are distributors.

 

[Marsupial]

changed a fixed 3 blade to a volvo folding 3 blade - on a shaft. very satisfied with it.

noticeable increase in sailing performance in light airs. hull speed is easier to achieve at all points of sail.

no noticeable problems going astern, or stopping the boat, still has prop walk but this can be a good thing . . . can be a pain in the . . . . .

prop does spin when the engine in switched off sailing, engage a gear and it folds instantly and stops spinning. Gearbox can then be taken out of gear with no load on the selector mechanism, previously with a fixed prop in gear and sailing the lever was very stiff, needed to start the engine in gear to select neutral.

on a previous boat I had a max prop - was not impressed. yes it had amazing astern performance but I was never sure it had feathered - when sailing the prop kept spinning . . . . . the gear lever was always loaded if I engaged a gear to stop it from spinning so I concluded that it did n't feather. took it off sent it back and replaced it with a fixed prop, put up with the drag, sold the boat (prop was not the reason for selling it).

 

[dovekie]

38 ft old AWB. Changed from a fixed 3 blade to a Bruntons Autoprop - self-pitching, more expensive than the folders as you've probably seen.

Good things
Quicker in light winds, at least half a knot - perhaps more in very light winds.
Good motor sailing. No need to rev fast to get the prop to add some propulsion.

No change on our boat in astern performance or prop walk. Still need to engage gear to prevent prop turning when sailing. No change in fuel consumption that we've noticed.

Bad things.
Initial cost. And it eats anodes, which are £20 a go, one very six months. So we need to lift or dry out to change the anodes (at which time we grease the bearings too).

 

[pmyatt]

A friend of mine has swapped a fixed 3 blader for a gorgeous Brunton Autoprop. It certainly sails well, but it also made a phenomenal difference when motoring as the blades are constantly self adjusting for optimum pitch as the revs vary. Very impressive.

Brunton Autoprop without a shadow of doubt.

 

[blackbeard]

Changed from a fixed Radice to a Bruntons Varifold, both 2 blade. Boat is a British Hunter 245 (25', bilge keels), engine a Yanmar 1GM.
Hard to be certain (as I don't race) but the general impression is that the boat sails substantially better with the folding prop. When motoring, not much difference although I think the Radice was a tad faster.
There was a minor problem due to Bruntons assuming that the shaft taper would be the same as on a previous Hunter 245 which they had supplied a prop for - it wasn't!, and they didn't check the taper on the old prop which I had sent to them. Bruntons sent a new hub in the post to solve this.

Some minor points:
No problem in reverse provided you remember to give a little burst of power after changing into reverse gear.
Blades are heavier than with fixed prop so it's probably a good idea to be extra sure to let engine slow down to idle before engaging gear.
Pitch and diameter of folding prop were less than for fixed, as blades are wider and thicker and are "aerodynamically" shaped.
On putting gearbox into neutral and stopping engine when going from engine to sail power; blades may continue to spin, centrifugal force (I assume) can keep them open. Putting gearbox into reverse stops the spinning and blades then fold.
I would recommend the fitting of a folding prop on a small yacht with an inboard engine.

 

[alant]

I changed my fixed two blade Volvo propeller on my 120S saildrive for a Radice two bladed folding propeller. It was probably the best investment I made although the Gori is a better propeller. I used to race and it put me to the front of the fleet. My boat just sails so much better with the folding prop.

Under power there does seem to be a loss of 'bite' especially in lumpy seas but if the seas are lumpy, then the wind is usually blowing so I can sail.

Reverse isn't a problem. On flat water I can go from 4 knots forward speed (in neutral) to a full stop in my boat length (26') although not much happens in the first 10 - 15 feet. I don't understand the argument that reversing is difficult because if you are actually going backwards, the water pressure forces the blades OPEN. It's just the initial delay in flinging the blades open when you are still going forwards that may catch you out. The Radice blades are bronze and very heavy which must help them to fling open.

You can say that again.

When Sea Venture bought a fleet of Jen32's some years ago, many skippers were embarrased when their usual regime of a 'quick' 3 point turn/reverse into a slot, resulted in pranged pontoons/associated boats.

 

[john_morris_uk]

Like others who have posted, we changed from a fixed three bladed prop to a feathering Max prop. Ours does feather (I know because I have dived under the boat when we have sailed into an anchorage and looked) and the shaft no longer free wheels when we are sailing. The biggest difference we have seen is in light airs sailing. I think it made more than 1/2 knot difference and we regularly sail now where a dying breeze would have had us turning on the engine when we had the fixed three blader.

It was expensive, but we have no regrets with the purchase.

 

[Norman_E]

Presumably astern performance in of some importance only in marinas. I tend to view propwalk as something of an asset - like a stern thruster.

In Turkey you go astern onto most jetties and pontoons, not just in marinas, so astern performance is important. Propwalk can be a help or hindrance, and there is still a little with the Maxprop, but not the big movement of the stern to port that always happened with the fixed three blade prop. The difference is that the fixed prop was designed for forward thrust, and astern it took time to get a grip, and whilst it did so the paddlewheel effect took over.

 

[duncan99210]

Yet another fan of the Brunton Autoprop. I reckon it gives up to half a knot in light winds but really scores when motorsailing as it is very easy to match rpm to required speed. Also enable me to run the engine at 1800 rpm for 5.5 knots as opposed to 2400 rpm on the original Volvo prop. I doubt I would have bought one myself but I'm very glad the previous owner had taken the plunge.

 

[Arcady]

We changed the fixed 3 blade prop on our 40' motor sailer for a Brunton Autoprop. It turned out not to be a good match. Lots of vibration which wore the cutless bearing out in just one season and occasional some very nasty near-stalls when the blades got out of balance (usually air under the hull, sometimes eddy vortices in strong currents).

We subsequently changed it for a 4 blade feathering prop which has been a great success. We get as much as a knot improvement in light airs. The prop will initially spin, but putting the gearbox in reverse feathers the blades. Cruising rpm is actually slightly more efficient than the fixed prop (as it's slightly coarser) but ultimately there's a trade off at max power: flat blades are simply not as efficient as a helical screw.

On balance we are thoroughly pleased with the benefits of a feathering prop.

 

[Halo]

I changed from fixed 3 blader to Flexofold 3 blader. Best thing I have done since first investing in my first Decca Navigator. I went for Flexofold over because Brunton Autoprop because latter is incompatible with sail drive. Sailing perfromance is much better and motoring/ mooring at least as good as before with very little prop walk and easy breaking
I keep a running total of distance and time and can confirm that last year I averaged over 0.6 kn faster (0ver about 1200 miles from memory) than the yeart before I fitted it.
Would definately fit a Flexofold 3 blader next time because it is best for mooring IMHO and that is the bit that stresses SWMBO out
cheers
M

 

[flaming]

A few years back I did a lot of skippering for Sunsail. One corporate regatta in light winds, one of the boats was simply untouchable. They were so, so much faster than everyone else. This came as a surprise to most of the skippers there, as the skipper in question was not exactly one of the hot shots... Then after crossing the finish line of the final race they fired up the engine to motor back to Port Solent.

Yep, you've guessed it, the prop had fallen off.

Best illustration I've ever seen of the drag that a fixed prop causes.