Towing - stupid question

Steve_B · 23 July 2011, 21:45

Whilst refuelling today, we came across a family on a 6m Zodiac that had broken down. They needed to get back to the slipway at Swanage for their car and trailer. They offered an acceptable fee and we agreed to tow them round.

We put the family aboard the Parker, with the owner/skipper on the Zodiac and made up a bridle for the tow. In the harbour we had to stick to the 10kts limit and to be honest, it was hard to tell we were towing another RIB at all. Once clear of the speed limit, I pushed on to 14kts, the Parker still not planning and the Zodiac nice and stable in our wake (but did look like it was planning).

So whilst we didn't, it would have been so easy to have raised the speed a little more and had both boats planning at about 16-18kts. The sea state was smooth/slight. Has anybody towed at planning speeds, is it sensible/safe??

I dont expect to do this again, but it just set the mind off wondering about the subject. We had a huge surplus of power and the other boat looked very stable.

Steve

Neil Harvey · 23 July 2011, 21:57

Steve,

Ask Trevor g for his BIBOA tow experiences, he's witnessed scorpions towing other boats at about 25 knots; I would have thought puts a lot of strain on the tow line and fittings, but maybe better on plane than at displacement; I also worry about snatching at speed in slightly rougher copnditions, but would also be interested in others opinions

All I really know is my fuel consumption goes through roof towing at dispacement speeds, how did you find that?

Neil

Crusher · 23 July 2011, 22:15

Hi,
I have towed a 7.8 Rib, with a 7.8 Rib, Both at planning speeds (18-20knts), both rock steady. Boat being towed with engine tilted right up (I have heard others try and keep them down a little to keep everyhing straight, but this just seems dopey amounts of drag to me)
Was absolutely no issue, and towed for about 5 or so miles.

I now wait for all the comments telling me how stupid this was......

willk · 23 July 2011, 22:58

The secret is a VERY long tow rope and balls of steel...

Linky

I've been towed (onboard a 6.5m RIB) at over 25kts - it's OK, you need to have your comms worked out though

Anchorhandler · 23 July 2011, 23:27

Quote:

I now wait for all the comments telling me how stupid this was.....

No not stupid....its all about risk assesment...i wouldnt recomend towing another vessel at those speeds in somewhere busy like the solent as waves and wash from passing commercial traffic will put a much increased strain on the bow eye of the vessel being towed. (especially if it snatches) If the towing vessel should need to make an emergency maneuver to avoid something then again, problems could arise for the vessel behind. As Willk says, a long tow rope is the key...especially the faster you go as the catenary (the fact that the tow rope will sag in the middle) of the tow rope will act as a shock absorber taking out a great deal of the shock loading. The rope will actually stretch also giving a slight spring effect which also helps.
In my line of work we tow much larger objects (oil rigs etc..) but the basic principles remain the same There are times when some of our vessels have stretched the tow out to 1200-1300 meters depending on the weather conditions and the object being towed.

A rib towing something relatively heavy will handle differently also (especially turning) so i suppose some care should be taken when first setting out.

AS for leaving the outboatd in the down position....well i dont think i would as the thrust on the propellor will be reversed ie; instead of the prop pushing against the leg it will be pulled away from it causing a reversal of thrust on the bearings inside. It would be a bit like running astern for extended periods of time at 25kts...not really what the outboard was designed for.

Simon

Starovich · 24 July 2011, 17:20

I've towed a 6.5+ dive rib with divers on board at planing speeds from a 5.5 Humber across from West angle to Dale (Milford haven Mouth) after they flattened their batteries leaving all the gear on for a whole day.

Long slow acceleration , long tow line, was no problem.

I carry Jump leads now, much easier.

longjohn · 25 July 2011, 11:41

Quote:

Originally Posted by 250kts

Whilst refuelling today, we came across a family on a 6m Zodiac that had broken down. They needed to get back to the slipway at Swanage for their car and trailer. They offered an acceptable fee and we agreed to tow them round.

We put the family aboard the Parker, with the owner/skipper on the Zodiac and made up a bridle for the tow. In the harbour we had to stick to the 10kts limit and to be honest, it was hard to tell we were towing another RIB at all. Once clear of the speed limit, I pushed on to 14kts, the Parker still not planning and the Zodiac nice and stable in our wake (but did look like it was planning).

So whilst we didn't, it would have been so easy to have raised the speed a little more and had both boats planning at about 16-18kts. The sea state was smooth/slight. Has anybody towed at planning speeds, is it sensible/safe??

I dont expect to do this again, but it just set the mind off wondering about the subject. We had a huge surplus of power and the other boat looked very stable.

Steve

Hi Steve
I saw you towing on the way out of Poole past the training bank - I turned round to get a better look. Was impressed - the Zody certainly looked like it was planning as did the Parker really.
Cool
John

Steve_B · 25 July 2011, 13:31

Thanks for the comments and link.

As it was not another boat we owned or even a friends boat, I exercised caution and got the job done without incident.

The advice given is helpful and if such an unfortunate incident occurs in the future, would do the same, but if its Pete's or David's boat, might be tempted to push on ....

PeterM · 25 July 2011, 19:49

Quote:

Originally Posted by 250kts

Thanks for the comments and link.

As it was not another boat we owned or even a friends boat, I exercised caution and got the job done without incident.

The advice given is helpful and if such an unfortunate incident occurs in the future, would do the same, but if its Pete's or David's boat, might be tempted to push on ....

Best not mention David & towing.....more than enough of that I feel...