50hp 40hp sailboat folding/feathering prop wanted

Hello.

I am looking at a cost effective option to replace my damaged fixed 2 blade. One blade spontaneously broke off my prop the other day! What could have caused this!

What props would you recommend for my boat and what would be the prices + What info do you need to spec the correct prop? Would I need to haul and measure? I know the shaft is 1" but that's about it.

Boat is 1992/93 Hunter Legend 40.5 Yanmar 50hp. 4JH2E_YANMAR Gearbox: 5864_APMD
KM4A_KANZAKI Trying to find ratio.



Dennis.

 

IF you do not actively race in a very very competitive racing circle , another folding 2 blade will be just the thing.

IF you are a cruiser a 2 blade sailing prop ( thin blades) will give better engine performance and more reliable reverse than the folding style.

$300 vs $2500, sorta depends on how much a second per mile is worth to you.

The place to start is READING the old prop it will have diameter and pitch stamped on.

And reading the plate on the tranny to find the reduction ratio.

If they still exist , perhaps a call to the boat assembler would get all the answers you want.

 

Fast Fred.

Fitting a folding prop is widely recognized as the most effective mod you can do to increase sailing performance bar none. Speed increases under sail are usually about a knot from what I have read. A 3 blade fixed prop can account for over 30% of the total hydrodynamic resistance of the boat at hull speed and over 50% at low speeds!

Tests have shown modern folding props to be as good sometimes better than fixed props in forward. I can live with worse performance in reverse as long as I can still get into my slip. I prefer to think of my boat as a sailing boat than a motorsailer.

See test here http://www.flexofold.com/upload_dir/docs/Test_YachtingMonthly_low.pdf

Stock prop is:

Fixed blade 2 blade 18x15 RH
2.63 ratio
Shaft 1.25"

 

Radice/Allpa is probably the cheapest folding propeller and it is perfectly OK, if correct size is used. It used to be sold as Volvo Penta as well before Volvo Penta changed to the current curved blade design also for two-blade folding propellers.

Changing from 18" two-blade fixed propeller to a folding one on a rather heavy 40' cruiser will not increase sailing speed by a knot. In some extreme conditions it may, but typical less than you are able to notice unless you are racing against a similar boat.

But on the other hand Radice/Allpa is quite cheap and it will not spoil your engine performance. Probably on forward it will be as good as or even better than the old propeller, but on reverse you will likely need more rpm and have a smaller maximum bollard pull. But you have a big engine, thus that shouldn't be a problem.

Here is another test for you: http://www.klapschroef.nl/foto/14.pdf

I have no idea where to buy them around Brisbane, but you can find many sellers from the web.

Another cheap option would be Varifold, which was in the test you already found. Flexofold is better (better bollard pull and less prop walk on reverse), but more expensive as well.

 

Folding..duck bill...props are for race boats. Cruisers use feathering props like the MAX.

Ive only used MAX, so cant comment on the other feathering props. To change pitch on a MAX you must haul out the boat and disassemble the prop. Additionally MAX props must be packed with grease a few times per year. The grease tends to blow out. Any feathering prop that has better grease seals and can be pitch adjusted in the water would be worth considering/

Three blade feathering props last longer and are smoother to operate than two blades.

Both Feathering and folding props suffer vibration when motorsailing

 

Why? Folding propellers are more efficient on forward and they are much cheaper. Feathering propellers are usually better on reverse although with more propeller walk. But modern folding propellers are certainly good enough on reverse for most people.

 

Duck bills have no stopping power in reverse. Hard to Maneuver. Max props give good reverse thrust .

Perhaps there is a Modern Duck Bill. I dont know

I delivered a boat fit with an AutoProp folding prop. It was a dog to maneuver.

 

"Fitting a folding prop is widely recognized as the most effective mod you can do to increase sailing performance bar none". Speed increases under sail are usually about a knot from what I have read. A 3 blade fixed prop can account for over 30% of the total hydrodynamic resistance of the boat at hull speed and over 50% at low speeds!"


EVERY test by a mfg always shows remarkable improvements over the competition gas , oil goop, roller furling , folding prop or windsheild wiper blades.

"A 3 blade fixed prop can account for over 30% of the total"

Perhaps but that was NOT the recommendation a more efficient (under both power and sail) 2 narrow blade sail prop was the suggestion.

"Tests have shown modern folding props to be as good sometimes better than fixed props in forward. "

Whose tests? some prop seller? Good luck, watch the many videos showing this anchor superior to that anchor , on line.

I have a great deal on a bridge in Brooklyn for ya!

 

I agree tests should be taken with a grain of salt. But the tests I actually linked to had some decent results and it seems were done fairly.

Well clearly if a fixed 3 blade is bad, then the fixed 2 blade will be approx 2/3 as bad it terms of drag. A folding prop does not have to have "thin blades" which means it could be better in forward by design. The test I linked shows that this is in fact true with many folding/feathering props beating a fixed 3 blade in top speed and several being close enough to equal in forward bollard pull you would not be able to tell the difference in the real world. In fact a 2 blade folder beat the fixed 3 blade in top speed and pretty much equaled it in forward bollard pull. How would this go against your suggested thin bladed 2 blade? (which is currently what I have)

Maybe you need to check this thread again as there are 2 prop tests in here already. Or are you saying these tests which are pretty easy to do fairly have been blatantly rigged and the props with the best scores are just the ones whos company's bribed the testers the most?

Yeah. I must be pretty gullible to believe various test results from multiple sources and mulitple first hand stories from friends over someone who argues their points simply by suggesting people who don't take their advice are stupid.

 

Max props and other feathers always seem to be behind the folders and fixed blades in forward speed and pull tests due to the lack of curvature in the blades. However the reversing is the best of all props.

As you say the folders are not as good in reverse. This is something I can live with as long as its adequate. From my research people not used to them tend to report badly as they need much more RPM to work backwards. Seems to me once you are used to adding way more RPM than you are used to they can be OK in reverse.. However at max revs they can be up to 70-90% as good as a fixed blade, which to me sounds fine. The stock 3 blade in the test I linked took 9.3 seconds to pull the boat up from 6K the worst folding prop took 11.3 seconds. Not the end of the world.

 

Autoprop is not a folding prop: http://www.autoprop.com/

 

Thanks for that. I cant read the test but I think I can make sense of the results which show pretty much what all tests do (all faked results eh Fred? )

I will look into the radice and varifold.

The cheapest is still the martec non geared. I have not seen these in a test. I assume forward would be as good as other 2 blade folders but I am not sure how much difference the gears really make in reverse.

Edit, my boat weighs 20,000lbs which is pretty light for a 40 foot cruising boat. So I think even if I dont get 1K the gains will be still be decent.

 

Well...you can term it whatever you like...its still a dog.

 

In the prop test the autoprop got 43miles from 10L of fuel which was by far the best prop tested. The worst by far was the max prop which got 27miles from 10L. HUGE difference! Plus the autoprop was faster in forward.

For cruising I will take the better forward speed, power and great economy of the autoprop over the max props poor economy and reduced speed for the sake of great reverse. That's what I want. Others might like the reverse power and be happy with lack of speed and crap economy. As long as I can get in my slip with the reverse I will be happy. Eventually I wont be going near slips anyway.

 

The gears assure that each blade has the same diameter and that in light winds both blades fold. With a non geared you typically dive over and rubber band it closed.

Ive sailed many many miles with the old style Martec. They work, but again...reverse thrust is an issue.

Since Martec has been around for a while you can find them used.

The typical scenario has a boat shift from martec to max...prices should be good.