Folding Prop?

[DavidBolger]

I have been trying to race my Sadler 34 with limited success. My sails are the same age as the boat which is 1989, so I am taking the plunge and buying new sails. I asked my sailmaker to recommend which sails I should replace and in what priority. His number one recommendation is to change the prop from a two bladed fixed to a folding version. He does not sell props.

What do people think of this change? Will it make a significant difference to my speed? What details do I need to know before ordering a new prop? My engine is a Volvo 2003. Do I go 2 blade or 3? I don't understand what pitch means but what do I tell the supplier? How much do I pay and where do I go for one?

All help and comments much appreciated.

regards

David

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[snowleopard]

you could try CJR props of southampton who sell various folding/feathering props. they will advise on size/pitch. expect to pay nearer £1000 than £500. you will get maybe 1/2 knot extra under sail but that should be allowed for by the handicapping.

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[Brian_B]

We have a 2 blade folding prop on our Starlight 35. As with your boat it's connected to a Volvo 2003.
We find it works very well but had thought about changing to a 3 blade folding to improve marina handling. She can be a little unpredictable in reverse.
At the end of the day a 3 blade is twice the price but if I were fitting new, that's what I'd choose.
However, most racers couldn't care less about parking, it's the sailing performance they want and will get a 2 blader.
These sites may help:
http://www.autoprop.com/
http://www.gori-propeller.dk/

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[dralex]

We currently have a 2 blade folding prop and it definately makes about 0.5-0.75kn of difference. It is however a pain in the backside at times when it comes to trickier berthing manoevres involving cross winds as the initial thrust is not there. You can allow for it most of the time, but you sometimes get a surprise.

As Snowleopard says, folding props will be penalised in the handicap rating, so there may or may not be a payoff. As far as tru boat speed goes, it is definately an advantage.

I've heard lots of good things about feathering props, but have yet to convince myself the cost is worth it.

<hr width=100% size=1>Life's too short- do it now./forums/images/icons/wink.gif

 

[DavidBolger]

Thank you, Is there a difference between a feathering prop and a folding prop?

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[Brian_B]

Have a look at the Gori site.
Folding props fold flat then open when under power.
Feathering props swivel.

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[dralex]

I'm sure somebody out there can explain it better than me, but with a folding prop, the blades are geared together at the hub and fold 90 degrees- from being perpendicular with the shaft when open they fold to lie parallel to the shaft when closed. With a feathering prop, the blades stay perpendicular to the shaft, but feather to allow equal flow of water over both sides of each blade, therefore reducing resistance. I've heard that feathering props give better drive and also better performance in reverse.

<hr width=100% size=1>Life's too short- do it now./forums/images/icons/wink.gif

 

[BobE]

Yep there surely is David.
The blades on a feathering prop align themselves with the waterflow when the engine is stopped and the shaft/ prop is in gear and therefore stopped.
The folding props blades literally fold back when the prop stops again due to water flow..
Feathering works really well in reverse as well as forwards ..Folding works well in forwards but is sometimes debatable in astern due to the blades being " pulled" shut by the revese thrust.. But it's got less drag when under sail.
If racing without allowance for prop then go for Folding
If more concerned with maneovering then take the feathering option

I have a Darglow three blade feathering on my Sadler 32 and it's fine for what I do -- a little club racing and as much cruising as I'm allowed.

Have fun Cheers Bob E...

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[bedouin]

I recently converted from a 2 bladed fixed to a 3 bladed Gori folding. Firstly it made a huge improvement to handling under power, especially in reverse.

Under sail of course it depends on the wind - in light airs it can make a difference of about 0.5 kt, maybe a bit more. In heavier conditions of course it is not noticeable.

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[dralex]

Just out of interest, can you give us a ball park figure for the Gori prop.

Thanks

Alex

<hr width=100% size=1>Life's too short- do it now./forums/images/icons/wink.gif

 

[DavidBolger]

Thanks,

What kind of boat and engine do you have? Also why did you choose Gori over any other brand? I would also be interested in price if you don't mind.

Thanks for all the advice.

regards

David

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[bedouin]

Not cheap /forums/images/icons/frown.gif

The Gori three-bladed folding prop costs about the same as the feathering props of comparable diameter (but IMHO out-performs the feathering props).

I forget the exact price (well you have to if you run a boat) but it was about £1200 for a 15"

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[snowleopard]

a feathering prop is around twice the price of a 2-blade folder as are bruntons.

i was afraid i would get poor performance in reverse with a folder but feathering isn't an option for my boat. i was surprised to find that the folders could stop me from 10 knots in less than a boat length.

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[bedouin]

There are dozens of folding props on the market - I am explicitly referring to the 3 bladed version of the Gori prop, which is a folding prop like none other. Price wise it came out to be very close to the AutoProp, Maxprop and the like, and more than twice the price of a cheap 2 bladed folding prop.

In reverse the blades open the opposite way round (a feat that only the Autoprop can match IIRC) and so always presents a correctly profiled blade to the water - unlike a fixed prop or a conventional 2 bladed folder.

As a result it is more efficient in reverse than a 3 bladed fixed and a vast improvement over the 2 bladed fixed it replaced.

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[cliff]

Before you buy anything, talk with Mike Lucas of Mike Lucas Yachting.

The prop recomended for the Sadler 34 by Gori apparently is not correct. Mike has fited a number of replacement props to the 34s and can give you chapter and verse on which is which and best for the 34.



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[sailorman]

check-out "MaxProp" prices
there as good astern as forward & feather fore & aft givine no drag.
they can be adjusted for rotation/ direction + pitch.
it will be a similar price to the Gori but u will req another shaft ( i think)
i have one that was fitted by the previous owner it is now slightly worn on the piviots bur is the best thing since sliced wotsisname
good hunting
roger

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[kidnapped]

Tried them both, folding and feathering. Folder wouldn't fit, they fold out almost the lenghth of the diameter .... my half skeg was too close, bought a Maxi three blade job, very good. It seems to be quicker, slightly bigger than original three bladed fixed,and works well in reverse. When looking at these props, comment was made more than once, that yachties do not necessarily put the biggest/best suited fixed prop on .... due to drag ... but fix the one 'that will do' ie smaller. Anyone heard this??

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[BlueSkyNick]

I have not thought about this before, myself. Having read this thread and as a cruiser-only apart from the occasional race for fun, any folding or feathering prop is not only expensive for little benefit, but is also one more thing to go play up at just the wrong time.

All IMHO of course.

<hr width=100% size=1>There is no such thing as reality, only different people's perceptions of a situation.

 

[alahol2]

When I bought my boat it came with a BIG three bladed prop. For various reasons I decided to try a folding prop (the best reason was that it cost me £50). The new folding prop, 2 blade, was much smaller than the original but it added a half knot under power and at least a knot in light winds and half a knot in stronger sailing.
Even for a cruising boat that's worth having.
Unfortunately I'm now changing my engine and, you guessed, it turns in the opposite direction. So now I'm faced with a choice of £400-£800 for a folder or back to a 2 blade fixed. Life's not fair.

<hr width=100% size=1><A target="_blank" HREF=http://www.troppo.co.uk> Follow the Tightwad Sailor</A>

 

[brianhumber]

Re: Gori

Would also add that by going ahead from reverse without allowing the blades to fold again, you have a coarse pitch profile going ahead. This means less revs for more speed in anything up to moderate seas - ie less fuel and its quieter in my case becuase I am spot on the max effieciency curve for power/torque.
Best thing I have bought for the yacht in 8 years of ownership, also improved the handling 500% over the previous 2 blade folding prop.

This kind of quality is not cheap, mine was C£1,500 8 years ago.

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