Folding propellor for SD20 saildrive ?

[wizard]

I have a Yanmar 2GM20 with SD20 saildrive and wish to fit a folding prop to reduce drag when sailing. Modern yacht, fin keeled, LWL 8.07m , beam 3.2m, displacement 4090kg.
Have done quite a bit of research, lots of types (and prices !!!) to choose from, so now I am really confused.
Does anyone have any advice/ recommendations on the various makes, or even better, a before and after scenario having changed from fixed to folding and what worked for them.
Many thanks in advance

 

[Trajan]

We have the same setup, on a slightly bigger yacht, we changed a 16x11 fixed to a 15x11 folder, the motoring was better and the sailing performance much better, ie at least 0.5 of a knot increase! and much less turbulance on the helm...
However...
Do Not get a Gori!
The blades and hub are insulated (most SD props are) from the Alloy SD20 leg but they have no anodes and as such any unprotected alloy of metal will dissolve away underwater without sacrificial protection...

However Sillette Sonic (UK) dealers will still sell you not one but two even tho they know they dissolve away (after a few seasons) then scream your out of time when you try and goto court. Just look around the forums and there's plenty of examples of bad life and support - However watch out, there are posts telling us all how great the props are and they last years - these we believe were posted by the UK agent, we tackled them on this in one of many pre-court letters and they ingored it, so we aussme its true. - There line is "the props will exist in a natural salt water enviroment" which a marina is not as you may imagine so they dissolve away!

Source one with anodes, The composite Kiwi prop is supposed to be good - Just ensure that the prop is protected with andoes and it should be ok...

 

[wizard]

So, which one did you actually buy in the end ?

 

[Trajan]

Hi, Again,
I am actually after our bad do with gori currently running tests at my university labs to find out the best prop for Sail Drives, each and everyone has their problems - I have recently come across a composite propeller, called a Kiwi Prob, which looks as if it may be a solution to many of the problems which plague sail drive folding/feathering props - The company are providing one for the tests (both lab tank's and *field* based tests) - In theory the prop looks very good indeed from corrosion (It is not insulated from the leg, it doesn't have to be because there is not a large surface area of metal, as such the stainless metal there is would be protected from the leg anode + it's mass is a lot less that the heavy Nickle Alloy Bronze Gori etc) and all testimonials about its actual performance and already published data read well. The best part of it, its very competitively priced compared with other makes, its 3 blade and the people running the show seem friendly, helpful and extremely knowledgeable....

take a look at their site, http://www.kiwiprops.co.nz/ there are uk agents now, just contact them for more information


Hope that helps,

Greg...

 

[arvin555]

Trajan,

I am currently replacing my bukh 10hp to a yanmar 3YM20 and SD20 saildrive. I am surprised at what you said because when I ordered a folding propeller from the same yanmar dealer, they gave me a Gori!

This makes me nervous now! I am stuck with my Gori propeller and will probably go ahead installing it, but will already start looking for possible alternatives. unfortunately you mentioned that most folding props are insulated so there really is not much to choose from other than the Kiwi props! /forums/images/graemlins/frown.gif ?

Wizard, going with a folding propeller will surely help you with speed in sailing. The disadvantage with folding props though is you will have to clean it regularly, once I couldn't get out of the marina because the props couldn't unfold because of too much fouling.

TTFN
Arvin

 

[snowleopard]

i have a pair of 3gm30s with sd20 legs and flex-o-fold 2-blade props from cjr. results are excellent.

it is essential to us a rubber-bushed prop if you have a folder, otherwise the gearbox warranty is void.

i think you will need 15x12 props but cjr will advise if you choose them.

p.s. even when we had an inch of fouling all over the hulls in the caribbean the props got only a few small barnacles and worked fine.

 

[Cantata]

In my experience you need to go up at least one inch in either pitch or diameter to make up for the loss of efficiency. But I've not used one of the really expensive jobbies like a Brunton.

 

[snowleopard]

the early folders were little more than flat plates of metal. the current ones have wide and thick foil-section blades that work every bit as well as fixed equivalents. in fact a 2-blade folder will be a lot more efficient than a fixed prop with narrow blades designed to reduce sailing resistance.

 

[quaelgeist2]

I have changed from an aluminium three blade fixed to a 2 blade folder.
It is a Radice (formerly standard supplier for Volvo) - very similar to Gori.
Boat: 31ft, 4.6t, MD2020, SD

Performance under sail: Big improvement.
Between 0.5 and 1kn - depends on wind/course/waves etc.
so I took average cruise times of regularly sailed trips. Reaching hull speed frequently, even with moederate winds.

Performance under engine: Little change
Less prop walk, which I regret since it helped in tight marinas, canals.
Slight delay when giving short thrusts as the prop has to unfold.
Had to change from 15*9 (volvo/moody recommendation) to 15*11, though.
(for that reason I could offer you a one season-used re-polished LH 15*9...)

I could not notice any corrosion on body or blades - I dont think my prop is isolated from the leg either.

 

[wizard]

Hi Snow Leopard

Just wondered if you have any form of rope stripper with these props ?

 

[snowleopard]

We don't have a rope cutter and, touch wood, have never needed one. we've probably been lucky but some people say they're not needed with folders (i don't believe that). it is possible to fit a Stripper in place of the ring anode on the hub.

 

[wizard]

Thanks for all the help.
Now have information on the Kiwi and the flex-o-fold- more homework!!!!!
Arrrrgh!!!

 

[arvin555]

10 years update!
This thread is quite old, and I recently visited it checking about other folding propellers for my friend, and was surprised that I posted here 2005 when I was doing an engine change. I'd like to update this thread as follows:

1. Turns out the Gori propellers are great. I have a folding type one that needs an anode for itself. The Prop has a rubber hub that insulates it from the SD20 saildrive

2. The Gori anodes are quite expensive, but they do the work, and after 10 years, I can say that the prop is still looking nice, aside from some scratches, etc. and of course the fouling, which I cleaned off.

3. The SD20 yanmar saildrive has it's own anodes and the Gori prop also has it's own anode and together I think they protect the whole system really well, I'd say mine lasts around 2 years, but I don't recommend going that long to check.

4. I just cleaned the Gori Prop from a lot of fouling, and I learned that using Muriatic acid (HCL) that is around 20% solution works nicely, it make the hard to take off fouling bubble. Diluting the Acid with water and dipping the prop will also make the prop shine nicely, this is how I "etched" the prop and applied laminating epoxy on it, as an experiment, we'll see how it fairs as a "primer" for antifouling paint.

5. I would like to suggest/remind members, to please use some kind of "Loctite" on bolts and screws and nuts on propellers. This way when you take them off (for when you want to clean them) the threads are still clean and smooth. Fouling got into the grooves of my set screws which made it hard to take off the set screws, putting loctite would have prevented fouling from entering, I think.

TTFN
Arvin