Propeller choice

[Crunluath]

We have really enjoyed our first season in our long keeled wooden boat (28ft 4.5 tons displ.), it sails like a dream. It motors ahead at up to 5 knots with ease... but going astern is a nightmare in windy conditions!
We have an old but reliable VP MD7a engine and a two bladed 14in prop, pitch not known.
Would a change of prop cut down the prop walk and give us any more grip, other than the white knuckle type on the tiller?

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[alan]

You should consider one of the feathering props, which give more or less equal performance in astern and ahead. Some makes are : Autoprop, Maxprop, J-Prop.
Autoprop is more expensive but is self setting for pitch according to revs/speed through water. I have one fitted to my light displacement fin keeled sloop and there is no appreciable prop-walk, and the performance in astern is as good as ahead.

Alan.
Nettuno, Italy.

<hr width=100% size=1>Alan Cloke

 

[Evadne]

Long-keel boats are notorious for being able to motor forwards or sideways but not backwards, as you have found out. It's possible to use reverse constructively, it just takes a bit more thought and practice (and a bit of luck) than with a fin & spade and rarely results in a straight course in the intended direction for more than a boat's length. I describe her as being predictable but intractable, i.e. if I try and steer her where she wants to go anyway, she will behave.
I have struggled with a 2-bladed prop. for years, but am told by fellow boat owners that a 3-bladed one would give us more power forwards and more bite in reverse. I suspect it will increase the paddlewheel effect as well. If, like me, your prop sits in a notch in the rudder then increasing the diameter is not really a sensible option. One day I'll get around to changing the prop., but I've got used to it now so it's less of a priority.
Meanwhile, just try and look on it as part of her character.

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[Paul_H]

Dont dismiss prop walk cos you can sometimes make use of it.

Suggest your difficulty is less to do with prop walk and more to do with vagaries of windage and the long keel configuration. Going astern is a bit like pushing a piece of string and presents new challenges at every attempt. A rudder on a long keel going astern offers very little turning moment compared to even a light breeze acting on the rig. Ill resist raising a previous thread about hanging sails up the backstay to counter act the wind - oh s**t I raised it.

After 20yrs with a CO26 I was just getting the hang of going astern and now after 12 mo with an HR35 I find Im having to learn all over again - especially the change from tiller to wheel.

Its the not knowing what's going to happen that causes those white knuckles. Get out and practice in a variety of conditions is my advice preferably away from where you can do damage if things go wrong (else youll have Robin shouting at you). Dont aimlessly reverse all over the place, rather set youself a target eg. relative to an empty mooring buoy (but not too close to foul your prop!!).

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[bedouin]

I was experiencing similar problems with my boat (which is fin and skeg with an offset propellor) and got great results by replacing the fixed 2 blade prop with the Gori 3 bladed folding prop. I imagine that any of the feathering props would do as well; as would a 3 blade fixed - but be careful about going for any other make of folding prop.

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[Evadne]

Re: reversing a long-keeler

I think that over the years both YM and PBO have done boat handling articles many times, and a scan through back issues might shed some light. At our owners association meeting last year we had an interesting talk and demo from Simon Jinks who proceeded to reverse his 30 (long fin & skeg) a hundred feet or so up the alley between the pontoons. He didn't offer to try it with a 29 (long keel) though.

The main trick is to remember that the prop always kicks the stern right (or left) and the wind always blows the bows downwind. If they balance you're in luck, if not then you've got problems. To reduce prop kick problems build up speed and then coast, with bursts of speed as necessary to maintain a weaving course.

This is all academic to me, I know my limitations. In marinas I always try and turn the boat to point the way Mr Holman intended her to, either with warps or using wind and/or prop kick, and accept that I occasionally get it wrong, with a 92-point turn or an unexpected return to a berth.


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[Crunluath]

Thanks to everyone for the useful replies.
I had rather accepted that going astern in a crowded marina was part of the character testing of long keel ownership.
I had thought we were getting better until our last return to berth or rather berths... we tried out several before we made it back to our own!

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[Crunluath]

Thanks to everyone for the useful replies.
I had rather accepted that going astern in a crowded marina was part of the character testing of long keel ownership.
I had thought we were getting better until our last return to berth or rather berths... we tried out several before we made it back to our own!
The problem is undoubtedly windage rather than prop walk, it is possible to use the prop walk to advantage on occasions, even if it means going astern in a complete circle before heading off out to sea!
I tried the rev up the engine in gear before letting go technique...very nearly catapulted my crew off the bow and terrified the guy on the berth behind us!
Back to practice I guess, thanks again.

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