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Old 17 June 2011, 13:22   #1
dnv
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performance when towing

Recently, on my Parker 630 with its 120hp oilburner and a mirage plus prop, I towed a Diva Royal 700. I was using a bridle, and the water was dead calm. The length of the towing rope was about 4 boatlenghts.

I was surprised to be able of making 7kn through the water only, with the engine revving at 3,100revs (max rated for 4,200-ish). Higher revs immediately caused the temperature to rise.
My key learning was that in serious conditions it may be difficult to tow, at least this kinda objects. It might only be possible to assist in stationkeeping.

what is your experience on perfomance when towing - what is possible and what not?

regards
Jan
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Old 17 June 2011, 13:38   #2
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I've successfully towed a 9.5m with another 9m fitted with a 250hp outboard at planing speed.
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Old 17 June 2011, 13:58   #3
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Was the casualty craft in Neutral gear? If in gear then more resistance...

It seems very slow though. Were you tied to his bow eye/painter or higher up on the craft?
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Old 17 June 2011, 14:18   #4
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Quote:
Originally Posted by willk
Was the casualty craft in Neutral gear? If in gear then more resistance...

It seems very slow though. Were you tied to his bow eye/painter or higher up on the craft?
Was tied high up to a clamp on the f'cstle. Don't know if in neutral.
When seeing the temperature rising while at abt 3,500 revs, I took back to 3,100. So I donno the speed at higher revs...

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Old 17 June 2011, 15:32   #5
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I don't know if it would make much difference, but the tow line may have been holding the bow of the casualty down in the water. Having thought some more - I bet that other vessel is very heavy too....
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Old 17 June 2011, 17:10   #6
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Was the casualty craft in Neutral gear? If in gear then more resistance...
Are you sure? In my yotting days, we had a 3 blade fixed prop and it sailed better in gear than in neutral. Think of a freespinning helicopter VS one that's rotors aren't turning.
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Old 17 June 2011, 17:37   #7
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Quote:
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I don't know if it would make much difference, but the tow line may have been holding the bow of the casualty down in the water. Having thought some more - I bet that other vessel is very heavy too....
Well, a Diva Royal displaces more than 2.5t.
With the bridle pretty high up and such a long rope, you ain't pull down too much.
My bet is, that the kind of hulls of the Diva have high a resistance at sub-planing speed. This combined with the displacement makes them a tough tow.

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Old 17 June 2011, 17:45   #8
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Are you sure?
I'm certainly not sure to be sure
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Old 17 June 2011, 17:49   #9
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In my yotting days,
LORDY well... I knew there was something .. if you want to say it three times to help the process of eviction just say..... 'three failed wheel bearings '.. SEVERAL TIMES after a goodly number of pints of course ,.. and all will be well
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Old 17 June 2011, 17:54   #10
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lordy well... I knew there was something .. If you want to say it three times to help the process of eviction just say..... 'three failed wheel bearings '.. Several times after a goodly number of pints of course ,.. And all will be well
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