Flexofold 2 or 3 blade folding on oversized 50hp FP Lavezzi

[CaptainRivet]

Hi all,

I am about to replace the fixed props on my FP Lavezzi cat.

Will go for flexofold
- reputation and trouble free
- can be serviced underwater (have coppercoat and saildrive oil-change from on top), no yearly haul out needed
- Price: 2 Blade 19x14 2500 , 3 blade 18x13 3500euro

I am only changing to folding because I have oversized 50hp engines and the corresponding 17x15 fixed 3 blade props (instead 13x11) cost me minimum 2 kn when sailing due to huge drag. I wanna optimize sailing, former owner motoring

Due to price plus replacement parts eg if loosing/damaging a blade and budget I would choose the 2 blade but don‘t know if I regret not to choose the 3-blade and spend 1200Euros more. I am on budget ( have around 10 other things with 1000-2000 more or not so the small stuff counts to 20k additional or not) but will have 1200 more when it’s a big difference.
Flexofold says and recommends the 3 blade as it has more bite and power but I already have more then enough power, so loosing a bit I don‘t care at all.

Is gearing correct: I have now 17x15 3 blade fixed which fits well and flexofold suggest only a 13 pitch in 18x13

Background
I have overpowered new 2x D2-50 in my FP Lavezzi (normally 2x20, upgraded 2x30) and have fixed 3 blade 17x15 propellers. Done by former owners who were motor boaters whose focus was motoring and having some sails when perfect condition for sailing…well I am the opposite…Gearing fits well and I do 13kn with both engines going 2800rpm. But tick tick with 800 is 3-4kn so maneuvering in tight spots is tricky.

But the 17x15 fixed costs me min. 2kn so I wanna change to folding or feathering…
Feathering would be actually the better option due to variable pitch I was told to get most out of the engine plus less drag but I cannot find reliable feathering for a price below 5000Euro for 2 props plus yearly service and that’s not worth it for me.

[fstbttms]

Originally Posted by CaptainRivet

...can be serviced underwater...

FYI- ANY prop (be it fixed, feathering or folding) can be serviced underwater. This attribute is not particular to Flex-O-Fold props.

[CaptainRivet]

Originally Posted by fstbttms

FYI- ANY prop (be it fixed, feathering or folding) can be serviced underwater. This attribute is not particular to Flex-O-Fold props.

Eg Volvo folding cannot be serviced under water.
Flexofold just the anode need to be changed, no greasing etc. like others.

[fstbttms]

Originally Posted by CaptainRivet

Eg Volvo folding cannot be serviced under water.

Give an example of service that cannot be performed to a Volvo folder underwater.

[SV-Viento]

I’m guessing you have seen the article in Yachting Monthly with the full article PDF found here https://flexofold.com/test-results

Had this same question and asked the flexofold rep at a boat show prior to COVID and he said the biggest difference would be noticed motoring into head winds and lumpy seas and said the 3 blade would do this better. The review indicates a pull value in forward slightly more for the 3 blade.

You have identified the crux for you which I see as additional cost for slightly better forward motoring performance. Have owed the 2 blade and ordered the 3 for our next boat. You’ll be happy regardless.

[Paradox111]

On my 31' mono (16hp), in 25kn of wind and chop on Biscayne bay, Florida,
I was doing 3kt with my 2 blade prop, and 5kt with my 3 blade prop.
On flat water no wind, about the same speed.

[CaptainRivet]

Originally Posted by SV-Viento

I’m guessing you have seen the article in Yachting Monthly with the full article PDF found here https://flexofold.com/test-results

Had this same question and asked the flexofold rep at a boat show prior to COVID and he said the biggest difference would be noticed motoring into head winds and lumpy seas and said the 3 blade would do this better. The review indicates a pull value in forward slightly more for the 3 blade.

You have identified the crux for you which I see as additional cost for slightly better forward motoring performance. Have owed the 2 blade and ordered the 3 for our next boat. You’ll be happy regardless.

Why do you take the 3 blade instead of 2 and spend the extra money?

Thanks. Yes I knew the tests.
Well if its only slightly better forward motoring i happily take the 2 blade, have plenty, actually too much of hp. Thats what i can read from the test also. I can't find any major differences then a bit more vibrations on higher rpms which a hardly use being overpowered.
I am just afraid i am biting myself in the ass later not spending the 1200 extra for the 3 blade because i missed an important fact. FFOF and Groever who calculated and manufactured my 3 blade fixed recommend to take the 3 blade folding.

What i heard from a gearbox remanufacturing company that the 2 blade folding stressing out the saildrive bearings and wearing them out faster then 3 blade. But I can't find it in any tests or threads about folding props. If thats true i am spending the extra 1200 without thinking twice.

[CaptainRivet]

Originally Posted by fstbttms

Give an example of service that cannot be performed to a Volvo folder underwater.

Greasing it... May work but a hassle I don't have with FFOF.

[fstbttms]

Originally Posted by CaptainRivet

Greasing it... May work but a hassle I don't have with FFOF.

Why would you lubricate a Volvo prop but not the Flex-O-Fold? Not that anyone ever does either.

[CaptainRivet]

Originally Posted by fstbttms

Why would you lubricate a Volvo prop but not the Flex-O-Fold? Not that anyone ever does either.

Look at the manual of the volvo plus Groever prop specalist that would deliver them told me to do so yearly require greasing while FOFF is just replacing anodes

[sailingchiro]

I have 2 qty. 3 blade 17" Max-props Classics if interested.

[Squanderbucks]

The choice between 2 and 3 blade props has to do with the weight of the boat and the performance data of the engines. Typically lighter faster boats use the 2 blade props while heavier boats benefit form the additional surface area of the three blades.
If you are trying to get your best performance sailing and don't care about motoring performance get whichever. But do you want to trade poor sailing performance for poor powered performance.
Getting the blades number, diameter and pitch are all important. Either use an online prop calculator or have a prop shop do the calculations for you.
You want the maximum pitch and diameter that lets your engines rev up to about 100-150 Above the stated max RPM Fully loaded. You do not want as many people suggest putting too much pitch on it to make the max RPS lower than the specs for top rpm. This will lead to engine lugging and shorter engine life as well as poorer fuel mileage. Even though you will likely not be running the engines at full throttle very often.

[CaptainRivet]

Thanks squanderbucks. Cat is light for a 40ft, My cat is fully load with all gear and tanks full 8-8.5t, overpowered 50hp engine where FOFF suggested a 19x14 2 blade and an 18x13 3-blade folding...original with 20hp is a 2blade fixed 13x11...
From all that a 2 blade seems sufficient.
now a 17x15 3 blade fixed is fitted which full thottle revs 2800 from 3000 max. delivers 13kn...have both power and sail catamaran...wanna optimize sailing but not screwing up motoring but ok with sacrificing a bit.
No glue about prop calculation.
Looking at test i only see i slight difference in performance not worth the extra 1200Euro especially because I have a bit to much. But a prop specalist and FFOF suggesting the 3 blade...

[fstbttms]

Originally Posted by CaptainRivet

Look at the manual of the volvo plus Groever prop specalist that would deliver them told me to do so yearly require greasing while FOFF is just replacing anodes

I have installed dozens of Volvo props (all of them underwater) and am quite familiar with the installation instructions. There is no mention of annual lubrication anywhere in them. Even if one were inclined to do so, a diver can easily take apart the blade assembly, lubricate the parts on the dock and then reassemble them. No need for a haulout for this.

[CaptainRivet]

Originally Posted by fstbttms

I have installed dozens of Volvo props (all of them underwater) and am quite familiar with the installation instructions. There is no mention of annual lubrication anywhere in them. Even if one were inclined to do so, a diver can easily take apart the blade assembly, lubricate the parts on the dock and then reassemble them. No need for a haulout for this.

Diver would be myself... Besides maintenance i know several boats with problems with the folding volvos from eating anods like crazy till problems with the tooth of folding mechanism while FFOF nothing besides some lost blades which 99% was a install failure.