performance when towing

dnv · 17 June 2011, 18:22

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

marinesafety · 17 June 2011, 18:38

I've successfully towed a 9.5m with another 9m fitted with a 250hp outboard at planing speed.

willk · 17 June 2011, 18:58

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?

dnv · 17 June 2011, 19:18

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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willk · 17 June 2011, 20:32

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....

Nos4r2 · 17 June 2011, 22:10

Quote:

Originally Posted by willk

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.

dnv · 17 June 2011, 22:37

Quote:

Originally Posted by willk

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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willk · 17 June 2011, 22:45

Quote:

Originally Posted by Nos4r2

Are you sure?

I'm certainly not sure to be sure

Bigmuz7 · 17 June 2011, 22:49

Quote:

Originally Posted by Nos4r2

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

Nos4r2 · 17 June 2011, 22:54

Quote:

Originally Posted by bigmuz7

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

jyasaki · 22 June 2011, 16:24

Quote:

Originally Posted by dnv

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

Once towed a 25'-ish Boston Whaler with my 18' RIB (F115). Only about a mile and a half or so, but made about 6mph at a little over half throttle (though a long time firewalled to get it up to that speed.) Any faster and the Whaler started reacting more to swell and chop, jerking the stern of my boat too much to allow me any peace of mind. So, 6mph it was. I was actually surprised it towed as easily as it did. That Whaler looked pretty beefy.

jky

Andy Gee · 22 June 2011, 16:33

Seen a 11m Redbay (6.5t ish) pulling another at 20 odd Knots. We also pulled the 850 (yeah the one willk broke

) back to Ireland from Jura at around 18-20 knots in a force 6-7 on the nose.
Toms pulling a 750 with fuel problems (the bug) back to Ireland at the moment at 25.5 knots.
A big long rope makes it so much easier for open water towing.
Cheers
Andy

willk · 05 July 2011, 20:05

Quote:

Originally Posted by Andy Gee

Seen a 11m Redbay (6.5t ish) pulling another at 20 odd Knots. We also pulled the 850 (yeah the one willk broke

y

Oi! Missed this piece of slander. It wuz donegaldan wot broke that bote...
...and I'm not convinced that you revving the t1ts off her helped either ;-)