Folding Props

Philip_Oceanis 361 · Dec 13, 2010

I have a Beneteau Oceanis 361 with a 2-blade fixed propeller. Despite the shaft been perfectly alligned and new engine mounts I still get some vibrations at high rpm. They are not annoying (well you get used to them) but whaever you do you will always have them because the engine is 3-cylinder, the propeller has only two blades and the Beneteau has that skeg behind the propeller (even some magazines such as the British "Yachting Monthly" mentioned about the vibrations caused by the skeg when they made a propeller comparison on a Beneteau 343; and to solve this their comment was to use a 3-blade propeller).
And to make it more interesting let me mention that I have been into another Beneteau Oceanis 361, same age, same engine but with a 3-blade fixed propeller. It feels so smooth!! It's amazing.
I was thinking replacing my propeller with a 3-blade Campell Sailer (cheaper that any folding/feathering) but haven't done in yet. If I was ever going to buy a folding one, since there's not much drag difference between 2 and 3 blades I would have paid the extra cost and get a 3-blader.

JohnShannon · Dec 13, 2010

Well I went from a fixed 2 blade to a feathering 3 blade (Kiwi prop) and it is much smoother and lower vibration. However the engine was more or less rebuilt as well so tough to draw conclusions. The first 375 doesn't have a skeg.

cymeyer · Dec 14, 2010

We have the same boat...

andale@1

We have the same boat, but 2000 model year. Had a 3 blade fixed prop. Smooth, but lots of drag. We bought a 3 blade MaxProp and have been very happy with it. Speed has been increased for sure. Costs more, but we are happy with it.

I need to find a place to sell our 3 blade fixed since it will just gather more dust...

Chris

Philip_Oceanis 361 · Dec 14, 2010

cymeyer said:
andale@1

Speed has been increased for sure.

I guess you mean speed under sailing. What about motoring? Have you noticed any difference? Do the two propellers have the same size (though besides size blade area is very important)?
Thanks

Ron20324 · Dec 14, 2010

sell your prop

cymeyer said:
I need to find a place to sell our 3 blade fixed since it will just gather more dust...

There's always the classified/gear ads on this forum.

Ron20324 · Dec 14, 2010

My B323 does not have that skeg, either. I bought a Gori 2-blade folder when they displayed at a Beneteau rendezvous. I liked the fatter part of the blade out near the ends instead of closer to the hub. At first I had a 16 x 13 thinking I had the 3YM30(29hp). I found I have the 3YM20(22 hp) and a heavier boat(13,000), so bought the 16 x 11, and that got me back to proper max RPM speed.

agaliha · Dec 15, 2010

Same engine with 3 blade Max prop

I have a 2002 B361 with a Yanmar 27 hp and a MaxProp. It is smooth and efficient. The prop has been flawless and has very low drag when sailing. It's expensive, but worth it!
Agaliha

James Simmonds · Dec 15, 2010

Does anyone have any experience with a Varifold prop from germany. The one I am looking at is a feathering version. Also expensive. I really want to reduce drag and stop the vibration while under sail.

gord331victoria · Dec 16, 2010

James, get yourself a Campbell Sailor. I mentioned I installed one last September and aside from sorting out the pitch (I am over pitcched and unable to reach 3500RPM) this is very smoothe, under power and sail. 90% drag reduction under sail, which increases top speed by at least half a knot. not bad for $700.00.

my plan to fix my pitch is haul out in January, send the prop to the Victoria Propellor to reduce pitch by 1.5 inches. West by North sold me a metric bore RH 15inch diameter by 9inch pitch, which I am only able to reach 3100RPMS. I'll let you know how this goes. When you are overpitched by this much, it's like driving your card in 4th gear everywhere, not enough power heading out, and missing reserve power when motoring into 30knots of wind.

Gord

Gunni · Dec 16, 2010

folding and pitching

Which Varifold prop "feathers"? A folder still drags a prop "bud" at a 10% (beneteau) angle through the water. Feathering is a better option. Get the pitch exactly right, filling your engine with carbon just to gain a slower cruise RPM is an expensive miscalculation.

JohnShannon · Dec 17, 2010

Feathering prop is supposed to give better reverse performance vs either fixed or folding.
This is cause the prop repitches to the new "forward" direction. I'm so bad at backing that I can't say there has been any improvement in my boat.

JohnShannon · Dec 17, 2010

This is off the Kiwiprop web site, a reprint from Practical Sailor. Shows drag forces for various props vs speed

http://www.kiwiprops.co.nz/drag.html

It is kind of hard to read the graph but looks like feathering or folding solutions are about the same in terms of drag.
Campbell prop is shown as best fixed prop in terms of drag.

JohnShannon · Dec 17, 2010

More stuff off the Kiwiprop web site.

This is tank testing for drag of various props incl a Kiwiprop.

http://www.kiwiprops.co.nz/documents/Drag-Thesis.pdf

What was learned
-locked shaft gives more drag than freewheeling shaft
-Kiwiprop feathering prop gives second lowest drag after two bladed folder

I didn't see any "figure of merit" in this thesis. It is all very well to find the lowest drag prop, but if you have settled on one without propulsive power what good is it?

I would like to see propulsive power/ drag (could be in reverse) in this case you get to compare what you want (propulsion) against what you don't want (drag)

Gunni · Dec 17, 2010

JohnShannon said:
...
It is kind of hard to read the graph but looks like feathering or folding solutions are about the same in terms of drag.
Campbell prop is shown as best fixed prop in terms of drag.

The test was conducted with "shaft parallel to streamlines". Unless you have a sail drive, your Beneteau shaft is at 10 degrees off parallel, which favors a feathering prop.

Ron20324 · Dec 17, 2010

Gunni said:
The test was conducted with "shaft parallel to streamlines". Unless you have a sail drive, your Beneteau shaft is at 10 degrees off parallel, which favors a feathering prop.

Unless you "park" the folding one in a vertical orientation, not horizontal.

JohnShannon · Dec 18, 2010

Well I have already bought a feathering prop so I guess I lucked out as I have a shaft. The test was done with a saildrive which would put the prop parallel to the streamlines.

cjgrabell · Mar 13, 2011

Ron20324 said:
My B323 does not have that skeg, either. I bought a Gori 2-blade folder when they displayed at a Beneteau rendezvous. I liked the fatter part of the blade out near the ends instead of closer to the hub. At first I had a 16 x 13 thinking I had the 3YM30(29hp). I found I have the 3YM20(22 hp) and a heavier boat(13,000), so bought the 16 x 11, and that got me back to proper max RPM speed.

have a Beneteau Moorings 38 1991 has a 2 blade prop wanted to look into a 3 blade. Shaft is 25mm current 2 blade 16 x 11 RH. The person who takes care of my boat said because the shaft has a taper/Beneteau would need to order the 3 blade from France???? Has a Yanmar 27 3 cylinder. Have to get up to high rpms to move the boat. Does this sound right

cymeyer · Mar 14, 2011

Which prop did you buy?

Which prop did you buy??
Happy wiith it?
CYM

andale@1 said:
I have just recently aquired a 1998 321 Oceanis with a 27 hp Yanmar and I would like to install a folding prop. I had looked at Two bladed Martec and purchased it. For the price seemed good however, the OEM Tech in SC said that the Two bladed caused vibration and noise due to the skeg shadowing the prop. Any findings from you owneres? Futhermore, the OEM said that they are only installing a 3 bladed as a option and that the three OEM's have been tested and are recommended and they are : Martec, Foldoprop and PYI. I am looking for some experience here so please help me.
Martec said that they have been providing these Two bladed props for this type of boat for years with no negative feedback and that I shoudl try it first. If I don't like it then Martec said that I coudl then go to their much more expensive Three bladed folding prop or their even more expensive feathering prop. What are your thoughts and what as users of this boat would you say is the best?
Thanks in advance for your inputs.
andale@1

Richard Atkinson · Jul 11, 2011

I have a Beneteau 323. It came stock with a 2 blade fixed prop. I have replaced it with a Varifold 15"X11" two blade. Less vibration with the new prop with no loss of speed under power. Sailing speed improved. I race in 20 mile races and had been 10 to 12 minutes behind another 323 that had a folding prop. After installing the new prop I beat the same boat by 3 ninutes in the last race! I am happy. Sorry I am late with Info.