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Old 24-05-2011, 19:16   #1
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Folding Props

Hi guys,

Fitting folding props seems to be the most effective way to increase the speed of a cat.
Has anyone fitted folding props or has folding props on their Lavezzi?
What sort of speed gain do you get?
What size is best and where is the best place to buy them?
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Old 24-05-2011, 19:43   #2
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Re: Folding props

I am in no way qualified to answer your questions, but I noticed you have a Lavezzi.

We have been looking at a Lavezzi here on the Chesapeake Bay in MD.

Any suggestions on the Lavezzi? Things to look for when buying one?

Best Regards,
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Old 24-05-2011, 21:06   #3
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Re: Folding props

Hi DJ,

There is a loy of disscusion on the osmosis issues on these boats.
My boat had a full bottom peel and was relaminated with a two year factory warranty.
Having said that it appears that these boats get gelcoat blisters not full blown osmosis so it's just a cosmetic issue.
They are also supposed to have an issue with cracks on the botom of the mast, mine has been fitted with a sleeve to fix this.
There also seems to be an issue with rudder bearings on FPs, some sieze up one of mine is worn the other has been replaced.
All in all I think they are the best boat in their price range and the layout/accomadation is exactly what we want in a boat.
I'm sure you'll be happy if you buy one, everyone else who owns one seems to love them.
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Old 25-05-2011, 07:05   #4
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Re: Folding Props

Hi Dragon Lady,
After much research we have purchased two Flexofold 17" x 12" three blade props last Dec.( exchange was .75 to the Euro then thru OZ FOREX ) to fit to the Orana on her next haul out this June ( Woolwich Dock-- Noakes Yard ) will let you know how we go and what the performance difference is, one way or the other!!

Gordon.
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Old 25-05-2011, 07:42   #5
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Re: Folding Props

I can't tell you the difference in our speed, as we always had a folding prop, but I can highly recommend the "Flex O Fold". In test done by MIT, this prop was the slipperiest, and most efficient of ALL props tested, "in forward". It even beat the Max Prop, as well as the other folding AND fixed props! In reverse, the Max Prop was better...

On multihulls, anything can slow you down. A 1/16" thick layer of slime might be 1 to 1.5 knots lost! For this reason, if I haven't been moving in a couple of weeks, I always dive on the hulls, and wipe the bottoms down with a Kevlar gloved hand.

BTW... The advantage of a folding or feathering prop on monohulls is less pronounced, but it is WAY more than most monohull sailors realize! It might take $10,000 spent above the WL, to equal the daily average run advantage of switching to a low drag folding prop.
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Old 25-05-2011, 07:46   #6
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Re: Folding Props

Dragon Lady,

What engines and HP do you have.

On the Mahe 36 with Volvo Penta D1-30 we use a three blade 17 dia. X 12 pitch.

We have one owner trying 18 diameter x 13 pitch prop upgrade.
This bulletin may help you.

Sail Drives and Props

Mark
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Old 27-05-2011, 03:50   #7
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Re: Folding Props

Hello,

here is photo off our volvo folding prop on our Lipari. ( fitted with Volvo 30hp )
mounted by FP.

I had also a Flexofold on my previous boat ( Oceanis 393 and Yanmar 40hp) and I was really pleased about it even running backwards.
Only one inconvenient, need to be really clean to fold well, make some vibration if dirty and loss of power running backwards, all that under motor.
3 blades seems to be better than 2 blades under motor.
the 2 folding blades are called here in France: "duck nozzle" blades.
If this can help !
cheers from south France
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Old 28-05-2011, 02:18   #8
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Re: Folding Props

Hi Dragon Lady,

I installed 3 weeks ago a folding prop on my Orana and the difference is huge..

To be more precise, I wasn't even attemting to sail if the wind were at least 12-13 kts. Now, I can sail at 8-9 of wind kts and make 4 to 5 kts of speed..
I've also bought a new assymetrical and with this alone (no main sail) and folding props, we did 8-9 kts at 15-16 kts true from 160-170 degrees..

My folding props are Radice (two blades) and cost only around 600 €. This is the italian company who supply the original alu props for the entire FP range to the factory. If you consider the original alu props (non folding) are around 380 € each, I think it's a good deal..

Orana use 17X13 and Lipari 16X13. Most likely yours would be 16X13 which cost actually a bit less

Orana and Lipari are coming with the props aft the rudder. (not sure but I believe this not the case for Lavezzi) This creates another problem, almost every week they are coming back from charter with props fouled with fishing lines. With centrifugal forces, these lines are then forced through the shaft to the seailing of the sail drive. The end result, sea water in gear box every week..
I've noticed that since we installed these new props we never had this problem anymore.
Therefore, I've ordered the same props for the other Orana and Lipari as well.

Depending on the request of the owner, we installed other brands of folding or feathering props as well both on cats and monos. Never heard any complaints from anyone. They are quite expensive though and some are quite sophisticated, particularly the ones with 3 blades. For me , the simpliest, the better..

Cheers

Yeloya
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Old 30-05-2011, 18:28   #9
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Re: Folding props

Thanks DL-

So here is the boat we have been considering.

Any thoughts?

Yachtworld link to Lavezzi

Best Regards,
DJ
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Old 31-05-2011, 00:27   #10
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Re: Folding Props

Thanks Guys,

We have Yanmar 27 hp with I guess SD20 saildrives.
I like the idea of the simple 2 blade. I can see why the 3 blades are better but the complication of design could mean more problems and they are obviously more expensive.
It looks like Europe is the best place to buy them from.
Does anyone have any recommendations for where to buy them?
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Old 31-05-2011, 00:41   #11
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Re: Folding Props

Check out the SeaHawk/Slipstream range. Stainless steel and Aust made. No personal experience however have not found and negative commentary on them on the web.

Seahawk: Slipstream Folding Propellers for Sailing Yachts & Sailboats

When time comes for me will be looking critically at them.
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Old 31-05-2011, 01:37   #12
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Re: Folding Props

Had new seahawk fitted & they work ok. I do suffer from barnacles in the gears. Bronze maybe better. 3 bladed feathering would be smoother & may not have as much problems from barnacles.
Regards Bill
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Old 31-05-2011, 03:40   #13
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Re: Folding Props

Quote:
Originally Posted by Dragon Lady View Post
Thanks Guys,

We have Yanmar 27 hp with I guess SD20 saildrives.
I like the idea of the simple 2 blade. I can see why the 3 blades are better but the complication of design could mean more problems and they are obviously more expensive.
It looks like Europe is the best place to buy them from.
Does anyone have any recommendations for where to buy them?

For a 27 HP 3 blades will not be appropriate anyway. Usually, 3 blades are recommended after 40-45 HP. The reason (I believe) is that after this power range 2 blades needs to be just too big..

The folding Radice is made of bronze, but it's too early to say how it will hold up in the future. Meanwhile I forgot to mention in my earlier post; like with every folding prop, you are using a bit of performance when motoring. Hard to say exactly but with these props I would have guessed 5 to 10 % forward a bit more on reverse.

Cheers

Yeloya
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Old 31-05-2011, 04:56   #14
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Re: Folding Props

Quote:
Originally Posted by yeloya View Post
For a 27 HP 3 blades will not be appropriate anyway. Usually, 3 blades are recommended after 40-45 HP. The reason (I believe) is that after this power range 2 blades needs to be just too big..

The folding Radice is made of bronze, but it's too early to say how it will hold up in the future. Meanwhile I forgot to mention in my earlier post; like with every folding prop, you are using a bit of performance when motoring. Hard to say exactly but with these props I would have guessed 5 to 10 % forward a bit more on reverse.

Cheers

Yeloya
According to the extensive study and prop comparison done by MIT...

"More blades" makes a LESS powerful prop in theory, IF they have the same square inches of blade surface area. (Apples to Apples)

A three bladed prop of 12" might be equal in size to a two bladed prop of 16".

Thrust wise, the most efficient prop would be a ONE bladed prop, but it would not balance, and is utterly impractical. The best "practical" solution would be a two bladed. THEN a three. This is regarding "thrust efficiency" for a given cumulative amount of blade area.

As is well known, a large prop going slow has more grip than a small prop going fast, but it gets complicated...

The reason for going with more blades, and/or smaller, faster props, (in spite of their being less efficient), is that after a point it becomes impractical to have a prop beyond a certain size, due to the hull's design constraints. There is just so much space for an aperture in the skeg, and it needs to be well clear of the bottom as well as the hull. Multiple blades then become the logical compromise.

IF, however, you CAN fit an appropriate sized two bladed prop, it will be more efficient than the exact same blade area of a three bladed prop, because there is less propwash for the blades to contend with. The two bladed prop will possibly have a bit more vibration, but this need not be an issue.

In the MIT study: Comparing the two bladed FLEX O FOLD folding two bladed prop to numerous other props, including a "Michigan Wheel" fixed two, fixed three, other brands of folding or feathering props, AND the two and three bladed feathering Max props... The Flex O Fold was more efficient than ANY of them, in forward!

IF it is sized correctly, YOU WILL NOT LOOSE ANYTHING BY SWITCHING TO A FLEX O FOLD in forward, you will probably gain... but you do loose a bit of reverse thrust compared to a feathering Max Prop.

Other brands of folding props have different results, but they all will improve your sailing and make it less likely to snag a crab pot line as well.

It is the most bang for your sailing buck!

Mark
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Old 31-05-2011, 07:19   #15
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Re: Folding Props

I found 2 beautiful Boyen 3 blade folding props in the bilge. They were so heavy I thought they may make the 27hp Yanmars sluggish. Thanks yeloya, now I don't have to feel guilty not installing them.....i2f
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