Folding Prop, Sunfast 37

[richy]

Any recommendations for a folding prop for my Sunfast 37? The engine is a Yanmar 3GM30 and presently has a two bladed fixed propeller. I've had some suggestions of variable pitch options which are probably unnecessarily complex and expensive for my needs. What size prop would suit, and any other hints? 

[ianpowolny]

We bought a feathering prop from Darglow for next season. They have a number of different prop designs. Speak to Rosie she seems to know a lot about props even if you don't buy one from Darglow. Our price was very competitive for our 45DS. You get a good discount before the New Year if they're open.

[On y va]

I agree with Ian. Darglow is a good company to talk to.

For you the main question will be folding or feathering. If you do regatta's regularly, I would go for folding. If you are a cruiser, go fro feathering. As you have a Yanmar, with a Yanmar (or Kanzaki) gearbox, I would go for a Maxpop Easy, 3 bladed prop.

[hoppy]

Dec 27, 2014 7:49:18 GMT On y va said:

I agree with Ian. Darglow is a good company to talk to.

For you the main question will be folding or feathering. If you do regatta's regularly, I would go for folding. If you are a cruiser, go fro feathering. As you have a Yanmar, with a Yanmar (or Kanzaki) gearbox, I would go for a Maxpop Easy, 3 bladed prop.

I got to ask why on the feathering for cruising?

My 3 blade flexofold is maintenance free, performs well forward and has great stopping power. If you get the one designed for your boat/motor/gearbox then I don't see any reason why you would want to change the pitch.

[richy]

In answer to the feathering vs folding q'n, while I've never used a feathering prop, on a boat at least, I'm guessing it's quite a bit more complexity and expense. And even feathered, more drag, relative to a folding prop?

[ianpowolny]

Speak to Rosie.

[On y va]

Hmmm, the "If you get the one designed for your boat/motor/gearbox then I don't see any reason why you would want to change the pitch.
" It´s again relative.

I have had the pitch changed on two yachts (with feathering props) this year, as according to calculations/manufacturers advice, they had the perfect prop for boat/engine/gearbox. However, with some growth on the prop, the engine could not get to it´s rev, fuel consumption went up and the exhaust started smoking somewhat. People in general, really underestimate the effects of fauled props. I see it time and time again.
So, we changed the pitch one mark on both these props and end of problem. Top speed with a clean prop is down 0.3 of a knot. For the rest you do not notice the changed pitch.

As to why I have preference to feathering for cruising.....Because they always work (well, I speak of Maxprops here). I have had folding props not opening properly due to crustations growing into the teeth, giving terrible vibrations.
Don´t get me wrong, I have nothing against folding props at all. They are cheaper, less complicated and cause virtually no drag. A feathering prop has about 5% (Maxprop) drag of what a fixed prop has on drag. But as an all rounder, I just think Feathering props are more all round than folding props. And as a cruiser, you want a prop that works good in fwd, stopping and reverse.

But, if I wouldn´t have a Maxprop, my next choice would be a Flexofold 3 bladed folding prop. But, again, mostly based on professional experience. Not because of some test in a magazine. I am just a great fan of Maxprops, because I know they work.

[ianpowolny]

This is great conversation and always goes around the same circle. It all comes down to personal preference.

We went for the FeatherStream over the Max-Prop for three reasons:
the Featherstream is cheaper than Max-Prop;
it has a thinner cross-sectional area as the blades are made from stainless steel
its designed and made in the UK and I wanted to support UK business.

...and there are nice pubs and people in Wareham.

We also went for the feathering prop over the folding because we bought Rosie's argument about cruising verses racing and stopping a large boat in a tight marina. Suckers maybe and time will tell. Ask me at the end of the 2015 season.

[jdl01]

Our 379 is driven by the yanmar 30 hp standard engine. I have run it over time with both the 16" 3 blade flexifold and a 3 blade 16" variprofile feathering prop. The feathering prop is better in reverse and stopping power - hence mooring advantages - but does not have as much pulling power as the folding prop when it comes to towing a dinghy and hence a lower towing speed. As I drag my dinghy around a fair amount I am sacrificing the in close handling for better cruising speed under power by reverting to the flexifold prop.

[hoppy]

Dec 27, 2014 19:11:01 GMT jdl01 said:

Our 379 is driven by the yanmar 30 hp standard engine. I have run it over time with both the 16" 3 blade flexifold and a 3 blade 16" variprofile feathering prop. The feathering prop is better in reverse and stopping power - hence mooring advantages - but does not have as much pulling power as the folding prop when it comes to towing a dinghy and hence a lower towing speed. As I drag my dinghy around a fair amount I am sacrificing the in close handling for better cruising speed under power by reverting to the flexifold prop.

I was about to say I'm surprised about your issue with the flexofold... but then it occurred to me that I really don't know what mine is like when throwing it into reverse to stop. I always med moor so for me stopping is throwing into forward gear.

[Don Reaves]

I have a 3GM30 in my SO35. For the past six years or so, I've use a 3-blade Kiwi Feathering Prop, which works very well. It's much simpler than most other feathering props, without gears and such. As a result, it costs about half as much.

Stopping and backing are much better than with the original 2-blade prop, and prop walk is much less. Drag is lower than with other feathering props because the blades align with water flow rather than the shaft, which usually has a downward angle. (The exception being sail drives.) However, the blades, which are made of a composite material, are rather thick, and I'm sure this increases drag somewhat.

if you decide on a feathering prop, it would make sense to investigate different makes and pick the one that seems best for you.

Don

[dublin]

I have previously commented on using s kiwi on a 39ds. I used a kiwi for 4 seasons. Significant loss in both cruising speed and max speed under engine with .5 to .75kt increase in speed under sail. Maximum speed was down to 6.5kts.
I believe the kiwi is not suitable for a boat with a waterline length of more than the SO35.
The prop really does depend on your type of sailing, fixed, folding or feathering. A friend who only does long passages including a number of Atlantic crossings and a circumnavigation takes the view that the loss in sailing speed with a fixed blade prop is not material with winds over 15kts and a loss of .5 it on a long passage I.e. Over 1000 miles, is not material as there are too many other factors that effect passage time.
In my own case I did not find a material difference in speed under sail when the winds gots to 15plus.

Last season I reverted to the fixed and made some of the faster passage times under sail I have even made in my current boat. Also it is one less thing to go wrong. Many years go on a friends boat weI had a small piece of line around a folding prop when the wind died off Finistere. Drifting on the tide and a long Atlantic swell toward "the coast of death" was not pleasant. The amount of lne was very little but was enough to prevent the prop from opening. Such a small amount would have no effect on a fixed prop.

.

[On y va]

Dec 27, 2014 20:48:42 GMT dublin said:

I have previously commented on using s kiwi on a 39ds. I used a kiwi for 4 seasons. Significant loss in both cruising speed and max speed under engine with .5 to .75kt increase in speed under sail. Maximum speed was down to 6.5kts.
I believe the kiwi is not suitable for a boat with a waterline length of more than the SO35.
The prop really does depend on your type of sailing, fixed, folding or feathering. A friend who only does long passages including a number of Atlantic crossings and a circumnavigation takes the view that the loss in sailing speed with a fixed blade prop is not material with winds over 15kts and a loss of .5 it on a long passage I.e. Over 1000 miles, is not material as there are too many other factors that effect passage time.
In my own case I did not find a material difference in speed under sail when the winds gots to 15plus.

Last season I reverted to the fixed and made some of the faster passage times under sail I have even made in my current boat. Also it is one less thing to go wrong. Many years go on a friends boat weI had a small piece of line around a folding prop when the wind died off Finistere. Drifting on the tide and a long Atlantic swell toward "the coast of death" was not pleasant. The amount of lne was very little but was enough to prevent the prop from opening. Such a small amount would have no effect on a fixed prop.

---------------------

This is true. Over 15 knots, the difference gets less and less. However the wear and tear on your gearbox with a constantly turning prop gets exponentially higher above 15 knots.
It is also true that fixed props give the highest reliability for long distance cruisers. Hence a lot of cruisers do opt for fixed props. But, the fact that the prop is constantly turning and whining and wearing my gearbox out is for me a consideration to have a feathering prop (but I do have my original fixed prop and prop nut on board, just in case).

[dublin]

The owners mahal recommends putting in reverse when sailing. Stops the noise and wear but as ported on other threads is awkward as must sort engine before it. Can be returned to brutal unless you let the boat stop first.

[electricmonk]

I v e had all three types over the years, fixed, feathering and folding, I would go with the folding type, far simpler than the feathering and easier to manage, no anode or greasing needs. Mine gets cleaned once or twice a year with a scraper whilst afloat and has always worked forward and astern.

[abgreenbank]

I have a flexfold prop as recommended and fitted by jeanneau, was half the price direct from flexfold in Denmark than jeanneau plus I have the original 3 blade fixed prop. Has a zinc but difficult to have a rope cutter on a saildrive, works great, very little prop walk but needs a fair bit of rpm to change speed from fwd to reverse. If you don't put it in reverse for a second after stopping the engine it's pretty obvious as there is lots of noise from the gearbox, but all it needs is 1 second in reverse and then neutral after the engine has stopped and it's folded and quiet.


rgrds
ab

[Deleted]

We have the SO37 which has the same hull as the SF37. After lots of studying I decided to go for the 3 blad Kiwi prop. I will install it in March so for the moment I have no data on performance. The current configuration is an MD2030 with a 2 blad fixed prop. I will most certainly like the disappearance of the fibrations of the existing prop.

Furthermore I decided for the Kiwi prop due to less complexity and the gear wear which will occur anyhow on a folding prop.

[dublin]

The simplicity of the design and mechanism is one of the plus factors of the kiwi

When using the kiwi there are some things you need to be aware if

Unless you stop the boat before sailing the kiwi will not feather and will auto rotate. This is something of a pain if like me, as I expect most people you house the sails when motoring out of the marina and then turn off the engine when safe to do so. Ha one to stop the boat in the water at that stage is to put it mildly inconvenient.

At speeds in excess of about 6kts the kiwi will start to autorotate and the only way to prevent this appears to be to put the gearbox in reverse. Otherwise you will have the same noise etc as from the fixed.

There is an article on this on the kiwi website

I think the kiwi will be ok on the SO 35 waterline length but I will not be fitting it on the 39DS.

I will be putting it for sail shortly

[J349er]

Dubin, when going from motor to sail and instead of stopping the boat, why don't you just put the gear briefly in reverse to force the prop to fold as you do when reaching over 6kt? Got the same "issue" with the folding prop installed at the factory on my 349.

[dbostrom]

Generally speaking it's a shame antifouling for props is so difficult. 

Practical Sailor (I swear I'm not affiliated!) has a fairly dismal recent update:

www.practical-sailor.com/issues/37_46/features/Prop-Paints-Show-Familiar-Signs-of-Failure_11525-1.html

More background here:

www.practical-sailor.com/issues/36_7/features/Antifouling-for-Props_5942-1.html

[jdl01]

Hello Hoppy,
It's all about small marginal improvements. Had I not had two props at hand to play with, I probably would be unaware of the relative advantage. I'm not dissing the variprop, It has served me well on 2 boats.
Jim

[dublin]

J349r
The gearbox on the 39ds does not allow the leaver move from reverse to neutral unless the engine is running

[touchngo]

We have a Kiwi Prop on our SO40, but our experience has been that boat speed has improved, and we certainly haven't experienced the issues that Dublin reports. Could be something to do with different hulls, engine sizes, etc...

We also managed to get a line around us and have a simple cutter fitted to the shaft just ahead of the boss, which dealt with it. Had no problems engaging reverse.

I'm quite happy with it but understand that it really is a matter of choice.

We have the fixed blade on board just in case it is needed too.

Cheers, PT

[richy]

Evidently I've ambled into what sounds like a long-running folding/feathering debate. As I said in my opening post, and with due regard for all the factions, a folding one is likely to be most suitable for my needs. I've been recommended a 16" two bladed prop and been quoted £682 plus VAT. Does this sound like the right size, and is it a reasonable price?

[electricmonk]

Jan 1, 2015 13:24:30 GMT richy said:

Evidently I've ambled into what sounds like a long-running folding/feathering debate. As I said in my opening post, and with due regard for all the factions, a folding one is likely to be most suitable for my needs. I've been recommended a 16" two bladed prop and been quoted £682 plus VAT. Does this sound like the right size, and is it a reasonable price?

Richy, whatever you choose, folding or feathering fit a three blade, I promise you wont regret it.