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Author Topic: Prop rotation  (Read 2344 times)

volusia

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Prop rotation
« on: February 14, 2015, 07:22:59 AM »

This is my very first post, so I hope that I get it right.
I am about to start building a 1:24 scale model of a Macduff 27m workboat, (very similar to a Damen Shoalbuster).
The vessel in question runs three props in fixed nozzles, my question:-
Which direction should the centre prop rotate? both the other two run in opposite directions.
I am not new to building model boats, but have never done a three prop vessel before.
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Brian60

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Re: Prop rotation
« Reply #1 on: February 14, 2015, 08:36:06 AM »

Try this link and see if it helps......

http://www.propellerhub.com/rotation.html

Also use the forum search, this was discussed here a month or two ago.

radiojoe

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Re: Prop rotation
« Reply #2 on: February 14, 2015, 11:22:12 AM »

The prop setups I've seen in my years of working in the boat building industry, have been  for twin props/ stbrd clockwise, port counter clockwise,   for triple props /   stbrd clockwise,  port counter clockwise, centre clockwise,   for four props / stbrd pair clockwise,  port pair counter clockwise, all as viewed from the rear of the vessel.



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volusia

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Re: Prop rotation
« Reply #3 on: February 15, 2015, 06:22:59 AM »

Thanks for the replies guys.
Everything I've seen points to the centre prop running clockwise.
This will be the way I will go when I get to that point.
Cheers.
Steve.
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CapnTroy

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Re: Prop rotation
« Reply #4 on: February 17, 2015, 09:44:19 AM »

And you might give a thought to having your port & starboard props turn inboard...this will aid immensely when attempting "flanking" or "walking" maneuvers...
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Brian60

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Re: Prop rotation
« Reply #5 on: February 17, 2015, 07:21:42 PM »

And you might give a thought to having your port & starboard props turn inboard...this will aid immensely when attempting "flanking" or "walking" maneuvers...

Oddly enough this is how I have built my tugs in the past. However if you are building one of the newer style anchor handlers I have read it is best to have them 'turn outward' The thought here being that inward turning will create suction under the hull and pull down the stern which is already very low freeboard. Turning outwards will push water upward making the hull more boyant.

Then again if you have Kort nozzles this could all go down the pan anyway! :embarrassed:

volusia

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Re: Prop rotation
« Reply #6 on: February 18, 2015, 05:27:47 AM »

I would like to thank everyone for their suggestions, but I now have the answer. Yesterday evening I received an email from the marine architect at the shipyard where the vessel in question was built, and also the gentleman who actually prepared my drawings for me. Looking forward from the stern the port prop turns anticlockwise, the starboard prop turns clockwise, and the centre prop also turns clockwise.
I don't have an explanation as to why, but I am going to ask him the question.
As soon as I have the answer I will let you  all know.
Thanks again for all your advice.

Steve
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andywright

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Re: Prop rotation
« Reply #7 on: February 24, 2015, 08:20:36 PM »

It is "normal", for a prop to turn right handed unless specifically asked for, that is clockwise. However in the case of a twin screw vessel, the props turn opposite ways, to cancel out the 'walking' effect of the props, especially going astern, but also noticeable ahead. I have never skippered a triple screw vessel, so cannot say through experience, but would assume the centre prop would be right handed on a triple screw vessel. On Damen multicast with triple screw, I think all three engines would be run when the towing power is required, having three engines would not make an appreciable difference to speed when running at designed speed. Three engines would give the owner/ skipper more versatility when steaming from one job to another, if the vessel was not in a rush just the centre engine could be run, if normal steaming speed was required then the two outside engines would be utilised, and if power was required three engines would be run.
I won't go into fast vessels, as this is a tugs thread.
Hope this helps.
Cheers
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