320 - New folding propeller and gear reduction ratio

New folding propeller and gear reduction ratio

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Forum Name: 320
Forum Description: 320 Hints and Tips
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Topic: New folding propeller and gear reduction ratio

Posted By: aquilo
Subject: New folding propeller and gear reduction ratio
Date Posted: 06 March 2017 at 09:29

Hi

During winter we finally replaced the original jib with a better quality one (+positive leech) and we also want to replace the fixed propeller with a flexofold 2 blade (classic or composite).

Our boat is a 2010 build ("Smartline") with standard motor 3YM20 and saildrive from Yanmar.

I cannot find any labels on the saildrive. Anyone knows the gear reduction ratio (and possible other data) needed to choose the right size/type propeller?

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Hanse 320
Norway

Replies:

Posted By: Frederick
Date Posted: 06 March 2017 at 10:40

Most probably you will have the SD20 from Yanmar. The technical data you can find https://j109.org/docs/yanmar_sd20_saildrive_operations.pdf" rel="nofollow - here .

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Hanse 342#464 Frederick

Posted By: aquilo
Date Posted: 06 March 2017 at 11:33

You're right, it's a SD20 and the reduction ratio seems to be 1:2.64 according to the document.

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Hanse 320
Norway

Posted By: Andre
Date Posted: 26 March 2017 at 22:20

I have recently installed a new Flexofold 16 x 12 LA 2 blade folding prop. on our 320 as replacement for the standard fixed one, so the new design with large hub and protected gears with large anode.

Dimensions were advised by Flexofold.

Boat is still ashore, so no results yet.

Posted By: Janni
Date Posted: 03 April 2017 at 06:14

We have installed a 3 Blade Flexofold on our Smartline. We are very happy with it.

Dimensions were defined by Flexofold. There is only one little issue - we have YM30 instead of the YM20 - which we did not know before buying the prop. Now the engine revolutions are a bit on the high side.

Jan

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Hanse 320 #548 "SCHNEGGE"

Posted By: Andre
Date Posted: 06 June 2017 at 20:03

Some feedback from my experiences with the Flexofold 16 x 12 LA 2 blade.

On motor: a bit less thrust ahead and max. motor speed going up to 3700 rpm which is actually 100 rpm more than the engine should run at full speed. Also at 2800 rpm (which used to be my favourite engine speed) a bit less boat speed of 6.2 knots where the fixed one provided about 6.5 knots. Clearly less thrust in astearn, something to get used to, but certainly sufficient. The prop is opening/closing very smooth (you don't hear it, wouldn't know it is a folding one if I wouldn't have seen it myself prior launnching the boat), no noise at all and is also when running very silent. More silent than the old fixed one and finally no annoying "prop singing" anymore. Compared to the fixed prop in general I have the impression the folding one could have been slightly bigger in diameter and/or pitch (because at full throttle engine seems slightly overreving and a bit less speed at 2800 rpm), but it is also possible the fixed one in fact was slightly too heavy as engine tended to smoke a bit at full throttle. Max. boatspeed at full throttle is 7.2 knots in good weather, not bad at all.

Sailing, for which it was in fact bought: Upwind the boat speed increased with at least 0.3 - 0.4 knots, which I am very pleased with, I now am convinced about the folding prop advantages, always believed this was commercially exagerated. Also no annoying vibrations anymore (I always blocked the fixed prop from running when sailing) on the rudder and in the boat, just silent sailing.

So based on my first experiences and observations: very pleased.