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ireaney · 01-10-2007, 10:20

Has anyone had experience of either Feathering (Goris or Kiwis) or Folding Autoprops (Bruntons) on their catamarans, if so which types have you used and what was the difference in performance, before and after fitting and would you recommend them.
It would be very useful to get feedback from users of the different systems and more important if someone has experience of using both systems also any drawbacks.

Jeannius · 01-10-2007, 10:58

I just have fixed 3 blade things at the moment - thought it better while Jeannius is in charter - but I will definitely change to folding/feathering next year. Jeannius goes more than half a knot quicker when I allow the props to rotate while sailing but I then have the annoying whine when going quickly. It'll be worth paying the money for folding/feathering just to get rid of the noise!

ireaney · 01-10-2007, 11:06

Quote:

Originally Posted by Jeannius

I just have fixed 3 blade things at the moment - thought it better while Jeannius is in charter - but I will definitely change to folding/feathering next year. Jeannius goes more than half a knot quicker when I allow the props to rotate while sailing but I then have the annoying whine when going quickly. It'll be worth paying the money for folding/feathering just to get rid of the noise!

Hi, Jeannius, I can easily get rid of the whine for you (as the 435 is/would be my dream cat), just let me sail it back to my mooring on the Exe and give me title, and we could both be happy.

Seriously though, what extra speed would you hope to achieve?

SkiprJohn · 01-10-2007, 11:19

Feathering vs Folding. I chose folding so that I won't snag things on the prop. There is no deadwood ahead of it and the shaft is on a strut. Just thought it would be better in case a lobster pot decided to head my direction some day.
Kind Regards,
JohnL

Jeannius · 01-10-2007, 12:55

Quote:

Originally Posted by ireaney

Hi, Jeannius, I can easily get rid of the whine for you (as the 435 is/would be my dream cat), just let me sail it back to my mooring on the Exe and give me title, and we could both be happy.

Seriously though, what extra speed would you hope to achieve?

I doubt there is much increase in speed with /feathering/folding compared to a freely rotating fixed prop. It is very easy to turn the prop by hand when the box is in neutral.

My main reason for changing is simply to get rid of the whine. When crossing the Atlantic with big following seas and we were doing 10 knots and more it sounded like a 747 about to take off in the stern cabins. Certainly loud enough to wake up a nervous skipper (me). I'd go rushing up on deck ready to reduce sail only to discover that everything was completely under control and the crew and boat were loving it.

Sadly I can't take you up on your offer to take away my problem... I have to go and live on Jeannius in the Caribbean next year

ireaney · 02-10-2007, 08:45

Quote:

Originally Posted by SkiprJohn

Feathering vs Folding. I chose folding so that I won't snag things on the prop. There is no deadwood ahead of it and the shaft is on a strut. Just thought it would be better in case a lobster pot decided to head my direction some day.
Kind Regards,
JohnL

Hi John, Good thoughts, is your prop on a saildrive or shaft drive? as I can see the benefits would be more on a shaft drive than a saildrive as the latter has more chance of snagging lines etc.

SkiprJohn · 02-10-2007, 12:18

Aloha Ireaney,
My Gori folding is on a shaft behind a fin keel and ahead of my spade rudder. That's pretty standard for a fin keel monohull. I believe the folding prop will be less efficient when backing down. Since I don't intend to be backing down much, I'm not too concerned about it. I sailed quite a bit and always approached a dock or buoy slowly to avoid having to back down hard. Always worked well.
Good luck on your choice. I can't share performance with you as I've not put my boat in the water since prop installation.
Kind Regards,
JohnL

**Ex-Calif** · 02-10-2007, 17:44

Remember that with the folding prop your reverse performance will be affected. On a big cat in a small marina this may be a consideration.

Whn we went from folding to feathering it was like night and day...

ireaney · 03-10-2007, 01:43

Hi Ex-Calif, Did you notice any difference in performance when you switched and is your boat a cat or a mono.
Thanks
Ian

**Ex-Calif** · 03-10-2007, 16:56

Quote:

Originally Posted by ireaney

Hi Ex-Calif, Did you notice any difference in performance when you switched and is your boat a cat or a mono.
Thanks
Ian

We have a mono hull with 10hp Volvo, saildrive and original folding prop. We would get about 3.5 kts at 2500-2800 RPM. It was embarrasing - guys with 5hp transom mount outboards were motoring by us.

Reverse performance relies on centrifugal force to unfold the blades. Additionally forward pitch is compromised because too much forward pitch and the prop wouldn't reverse at all!

A friend gave us a MaxProp 2 blade internally adjustable feathering prop.

The difference is staggering. We now get about 5 kts at 2,000 rpm (quieter & faster) and about 5.8 kts at 2800 if we rally need to haul butt. I can't tell you what a difference this is to us.

Reverse performance is as good as a fixed prop. Make a mistake and coming to the dock a bit fast? It's like having disc brakes. Tricky tide to back out of a slip? It's like having 4 wheel drive.

Honestly I would never willingly go back to a folding prop. They are a bad idea who's time is past.

Moby Dick · 07-10-2007, 02:41

Quote:

Originally Posted by ireaney

Has anyone had experience of either Feathering (Goris or Kiwis) or Folding Autoprops (Bruntons) on their catamarans,.

No, I haven't, but am also considering swapping from 2 blade volvo fixed to feathering type. It is now between Brunton Auroprop (which is also a FEATHERING prop not folding) or KiwiProp. My engines are 30hp Volvos saildrives.

Theoretical dis/advantages of each type are:

Autoprop
Self pitching, so should adjust to best setting for all the variables on a cat - motor sailing, running just one engine, going into head sea, throttles not exactly balanced etc etc. Drawbacks: more drag when sailing, 2 blades (at least at the price I want) so slightly rougher and not so much thrust when needed?

KiwiProp
Three blades (smoother, more thrust when needed) less sailing drag, nearly inert materials. Drabacks: fouling problems? Pitch is a compromise under all sailing/motoring conditions. I dont think the fixed reverse pitch will be a problem.

Autoprop costs about 10% more. I know of at least two similar cats with 2 blade autoprop, and they are a knot or so faster sailing than mine, so they do work.

Anybody any other thoughts to aid descison?

Lucky · 07-10-2007, 02:41

I swapped from fixed to folding Volvo props on my previous Athena 38. It worked very fine and I didn't have any problems with manouverability in harbour and haven't experienced that the prop wouldn't engage when backing up.

The sailing speed gain varies and would not be an issue for anyone cruising, but the noise and damage to the gear is a differnt case all together! I've read somewhere that a Bahia 46 sailing down the east coats broke the saildrive clean off at high speed! With feathering or folding props that wouldn't have happened.

I always lock the props when under way, this actually gives more speed than free spinning! This sound very strange but do a simple test by pulling any type of toy with a propeller trough the water while free spinning and then do the same locked and you would feel the difference in pulling force is less at the latter.

With my current Belize 43 I cannot use any of the folding props on the market due to the short distance between the saioldrive and the rudderblade. I have looked at several different feathering props and after talking to several people with experience I belive the Kiwi prop from New Zealand would be a sencible choice. This still requires more space than available for me, but I like the simplicity of the prop and it is also very light compared to the competion. It is also as far as I've managed to find, one of the best priced 3 blade feathering props - if not the best priced.

Props are like food! You always find different people that hates and love the same thing!

Don't know what make and model you have, but a check with the manufacturer should provide usful information.

I have been advise Maxprop for my Belize, but I find the too expensive.

Happy lead free sailin!

ireaney · 07-10-2007, 09:15

Bruntons also make the Varifold which is different to the Autoprop and the Kiwi but I believe this is the cream but very expensive - any views on this or experience!!