Flexofold

[puffcard]

My theory is when they recommend a prop, it for a light boat (no cruising gear or full tanks) and a clean bottom. They seem to over pitch a little to me. If you are running loaded up or have bottoms not racer clean you might. I've have the 2 blade FOF and the size was spot on when we were racing, picked up 3/4kt at the same RPMs. Motoring while cruising, I think I would prefer a little less pitch. I think I'm starting to develop some vibration and plan to get the 3-blade FOF at this year's boat show and to install next fall. The two blade is not very unresponsive in reverse, scarry the first time I tried to stop. Has a fair amount of prop walk, more than my past folding props. Hoping the three bland well help with both of these attributes.

[robert sailor]

Originally Posted by puffcard

My theory is when they recommend a prop, it for a light boat (no cruising gear or full tanks) and a clean bottom. They seem to over pitch a little to me. If you are running loaded up or have bottoms not racer clean you might. I've have the 2 blade FOF and the size was spot on when we were racing, picked up 3/4kt at the same RPMs. Motoring while cruising, I think I would prefer a little less pitch. I think I'm starting to develop some vibration and plan to get the 3-blade FOF at this year's boat show and to install next fall. The two blade is not very unresponsive in reverse, scarry the first time I tried to stop. Has a fair amount of prop walk, more than my past folding props. Hoping the three bland well help with both of these attributes.

Was my experience as well, the prop suggested was over pitched (by 500rpm) and I ended up having to reorder new blades at my expense, they did give me some money back when I shipped the old blades back. Was not happy with that experience but I do like the prop.

[malbert73]

My FF was also over pitched but I asked for that. I wanted to optimize motoring for calm wind motoring to get hull speed at 2100-2200. My boat sails really well upwind so less priority for me to have full HP for upwind bash. Where I sail light/no wind is more common so I wanted quieter, more fuel efficient faster motoring for calms.
Now max rpm 3000 instead of 3600 so new 90% is 2700 which is plenty of power.
I think too much is made of achieving full rpms - I recognize that it is more idiot proof and you can get full HP but in calms it's like driving an old 3 speed car on a flat highway- engine revs too fast for actual need.


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[ausnp84]

Not sure I agree with the over-pitch comments - our boat was in full cruising trim (inc. a year's worth of food and circumnavigation spares) and the props were spot on.

n

[robert sailor]

Originally Posted by malbert73

My FF was also over pitched but I asked for that. I wanted to optimize motoring for calm wind motoring to get hull speed at 2100-2200. My boat sails really well upwind so less priority for me to have full HP for upwind bash. Where I sail light/no wind is more common so I wanted quieter, more fuel efficient faster motoring for calms.
Now max rpm 3000 instead of 3600 so new 90% is 2700 which is plenty of power.
I think too much is made of achieving full rpms - I recognize that it is more idiot proof and you can get full HP but in calms it's like driving an old 3 speed car on a flat highway- engine revs too fast for actual need.


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Its all good until your engine decides that it's over propped which is not good for your engine and if you have lost 600 rpm its my guess that you are over propped.

[Sonosailor]

I bought two Flex-o-fold systems for Cat Tales, for Yanmar SD-20 saildrives on 2GM20 engines: 16x12, with the SD-2 hubs, in 2004. The FoF company convinced me that they had worked with Yanmar to make the assembly. Pricey, in my opinion, but I have used them for 12 hard years. I go faster while sailing, faster motoring forward, faster motoring backward, and no longer miss the money. Btw, I take them off each haulout and hide them on board - so I guess that says how much I value them. I have had some minor trouble with stripped threads on some screws, and got great service ordering new and spare screws from FoF

[malbert73]

Originally Posted by robert sailor

Its all good until your engine decides that it's over propped which is not good for your engine and if you have lost 600 rpm its my guess that you are over propped.

Correct on being overpropped. But overpropped doesn't mean overloaded engine unless you run it too hard (i.e. at too high an rpm for match- i.e. Into strong chop, with loaded boat, or dirty bottom), much like driving a car uphill in too low a gear. But the dogma of running your engine at 75-80% of max is to load it up because it's underpropped at lower speeds and hence under loaded. Overpropping a little lets you load your engine properly at lower Rpms. Nigel Calder has explained and advocated for this approach if done right. I had a really enlightening conversation about this with him at the boat show a couple of years ago.


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[svrevelations]

We had 2 Gori props, excellent forward and reverse thrust - until 1 prop fell off for now apparent reason. After endless denials from non helpful Gori, we bought 2 Flexofold propellers. Very happy - although the reverse thrust is somewhat lacking.

[robert sailor]

Originally Posted by malbert73

Correct on being overpropped. But overpropped doesn't mean overloaded engine unless you run it too hard (i.e. at too high an rpm for match- i.e. Into strong chop, with loaded boat, or dirty bottom), much like driving a car uphill in too low a gear. But the dogma of running your engine at 75-80% of max is to load it up because it's underpropped at lower speeds and hence under loaded. Overpropping a little lets you load your engine properly at lower Rpms. Nigel Calder has explained and advocated for this approach if done right. I had a really enlightening conversation about this with him at the boat show a couple of years ago.


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I am also in agreement of being a bit over propped, right now we are about 300 rpm below normal top end rpm at full power and still get excellent fuel savings and decent speeds at lower rpm but 600 rpm is where I used to be myself and at higher power settings which I needed from time to time but well below 75% power I was getting some black stains on the transom and the Beta dealer suggested it was not good for the engine.

[puffcard]

Originally Posted by Revelations

We had 2 Gori props, excellent forward and reverse thrust - until 1 prop fell off for now apparent reason. After endless denials from non helpful Gori, we bought 2 Flexofold propellers. Very happy - although the reverse thrust is somewhat lacking.

Yea we had a Gori before the Flexofold and the backing was better with the Gori.

Question for the crowd. Does anyone else think they have more vibration with the 2-blade Flexofold? I seem to have a few sweet spots and run it there. I think my shaft system is ok and alignment seems ok. Thinking of going to the 3-blade next year, hear they run smoother.

[malbert73]

You have a T37 so I believe prop isn't in an aperture. Sometimes 2 blades vibrate more because both blades pass through dead water behind keel at same time. But this was described more in full keels or aperture I think and may not apply to yours. We have a 3 blade and it's super smooth.


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[vicbies]

Hi guys. I Just bought a 40 foot Apollo 12 plus Dromor build sail Boat. It has a 4 cylinder 4.14 mitsubishi 33 ho diesel engine. Thé prop is a 3 blade flexo fold. At 2200 rpm i get 6 knots. Above that I get vibration and prop cavitation. I use boat for commercial charter mostly using engine... If i changé to a fixed prop how much top speed can I expect to achieve with engine.. As i suspect prop is small... I charter most of the time with engine and would do anything to active at least 8-9 knots...

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