Towing Dinghies ...... Some Lessons

[TradewindSailor]

A trawler had been towing the 12 foot RIB behind the boat in reported 20 foot seas (probably 15 foot, but steep and cresting). The dinghy was being towed on a 40 foot length of Dyneema® SK-75 with negligible stretch. The snatching loads bent the combined fairlead - cleat that was set in the bulwark, and finally pulled the U-bolt clean out of the bows of the dinghy.

The trawler then made an attempt at recovering the dinghy, not at all easy in these conditions. Finally they grabbed it with a spare dinghy anchor ..... that hooked onto the throttle control on the centre console. The captain jumped into the dinghy to secure a line. But the dinghy broke loose again. The throttle control was broken now too.

With difficulty he got the RIB under way to try and keep up with the trawler, and to try a recovery. The visibility from the bridge to aft was bad, so his wife had difficulty keeping him in view. She had to go below for a short time. When she came up again he was no where to be seen.

An extensive search was instigated, including the Mexican Navy, and several cruisers. The trawler returned to port, captainless, in a thorough mess, and with a distraught crew.

About 3 hours later the Captain was discovered by the Mexican Navy lying on the bottom of his up-turned RIB. Luckily the water was warm and the sun not too hot. They recovered him, but failed to recover the RIB even after several attempts. He was declared fit and well and returned to his trawler later that evening.

Some lessons:
The loads on a towed dinghy can be huge.
The snatch loads are even higher ..... so if you do have to tow a dinghy use a long length of oversized poly-prop which not only floats, but has enough stretch to reduce the snatch loads.
If you loose the dinghy in heavy weather ...... don't risk your life to recover it.
If the bow eye has pulled out, there may not be another secure place to attach a line.
Have two independent tow lines, including the attachment point on the dinghy.

Anyone think of any other lessons?

 

[NormanS]

Yes, if at all possible, don't tow the dinghy, bring it aboard.
I don't know what size of "trawler" we're talking about of course.

 

[Stemar]

Others may disagree, but I think I'd rather use nylon than polyprop - It's good and elastic, but more UV resistant.

It seems that there are two ways to tow a tender, either a very long tow line that will absorb snatch or a very short bridle that stays taut. For my flubber, I favour the very short one, but am currently planning on towing a Mirror behind me at times this season, so am considering my strategy - it won't bounce off the transom like the flubber , so a fender on the Mirror's forward transom sounds like useful insurance.

As an aside, I've towed my flubber in up F7 and never had it try to take off, perhaps because of the short bridle. While I have found myself looking up at it from the cockpit at times, that's always been because I've also been looking up at the crest of the wave behind me!

 

[MonniotC]

flying flubber kites.

As an aside, I've towed my flubber in up F7 and never had it try to take off, perhaps because of the short bridle. While I have found myself looking up at it from the cockpit at times, that's always been because I've also been looking up at the crest of the wave behind me!

I've had mine take off several times on the same day. Shortish bridle. 2.4 metre Bombard AX2 with a Suzuki 2.2 outboard on it at the time. On each occasion it took off like a toy kite, turned on its back and came down again, immersing the motorhead. I don't have an anenometer, but I reckon it was approx F8.

 

[Ubergeekian]

With difficulty he got the RIB under way to try and keep up with the trawler, and to try a recovery. The visibility from the bridge to aft was bad, so his wife had difficulty keeping him in view. She had to go below for a short time. When she came up again he was no where to be seen.

One wonders what was more important than her husband's safety at this point.

 

[Twister_Ken]

The story does sound as if it should be recounted by Gerard Hoffnung.

 

[markdj]

Definitely use nylon and even some octoplait as it has loads of stretch. Polyprop should be resigned to the dustbin - useless on any boat I think.

 

[Salty John]

Just to keep things in perspective, the OP's report is of a 12ft, centre console RIB being towed behind a trawler yacht. You might be talking of a total weight of 300kg. A moderately sized tender with small outboard as towed behind your average AWB will be 35kg.
A towing bridle to spread the load over two towing points on the dinghy and a three-strand nylon bridle from there to the towing vessels quarters gives a very stable towing arrangement.
But, towing a dinghy in rough conditions is always going to be less than ideal so davits, or chocks on the foredeck, or deflate and stow are better options.

 

[TradewindSailor]

Thanks for the responses to date.

Firstly this was a 46 foot trawler. It had no davits astern. To raise the dinghy to 01 deck they would have used a mini crane.

My choice of poly-prop is for the floating qualities. Obviously this could be taken care of by floats on the nylon line. If the poly-prop is oversized and re-newed each year it shouldn't be a problem.

Unless the nylon line is floated there is a good chance that that it could get tangled in the rudder/s or propeller/s. The dinghy only has to surf down a wave and the line will get slack, or indeed if the trawler has to slow down or manoeuvre. Of course the ideal is to adjust the line so that the dinghy is always climbing the stern wave ...... but with such large stern seas it would not have kept taught all the time.

 

[TradewindSailor]

One wonders what was more important than her husband's safety at this point.

Yes .... fair comment. She went below to find warm/waterproof clothing for her hubby. She had realised that there was little chance of getting the boat back on board ..... and that he was determined to ride it home.

Another point: The visibility aft on this boat, or indeed down the sides, is particularly poor from the bridge. The view aft is provided by a camera set on the mast ..... when it is working. It doesn't take much to loose sight of a object the size of a 12' RIB in these seas ...... a person in the water would be virtually impossible to keep in sight for the duration of the recovery. With no other terms of reference other than the angle of the seas, it is very easy to become disorientated.

 

[mandlmaunder]

Thanks for the responses to date.

Firstly this was a 46 foot trawler. It had no davits astern. To raise the dinghy to 01 deck they would have used a mini crane

Having spent a lot of time around live aboard trawlers of the American preference, the larger(over 30ft) all have a crane to lift the RIB.

If you are going to tow a dinghy of any size then two points of attachment are better than 1, and the twin bridle is the safest option, especially if you have two separate lines coming back to two strong cleats.
The lines either have to be short enough to keep the RIB on the same wave as the main boat or long enough to have at least two waves between the RIB and the main boat to minimize the chances of being 'over taken' by your own dink.

If you ever see a Super yacht towing a 25ft 500hp macho tender(or what ever is the preferred toy of choice), the tender is usually 200/300ft behind the big boat.

 

[lw395]

....... You might be talking of a total weight of 300kg. A moderately sized tender with small outboard as towed behind your average AWB will be 35kg.
......

Until you fill the tender with a wave, when its mass will increase to......?
I reckon my AX3 will hold several hundred kg of water.
Another good point in favour of towing with the bow lifted on a short line perhaps. The AX3 has extra towing eyes under the front of each side tube, so you can easily keep it square on the transom. However, I would always put it on the foredeck out of preference, and definitely take the motor off unless only moving with harbour. But then my Yamaha 2HP is very light to remove.

 

[NPMR]

We have towed both a wooden rowing boat and a Laser Bug at different times.

As soon as the wind pipes up, the only way to deal with it is with a long line. A short line allows the dinghy to follow closely to the mother-ship but as it picks up speed surfing down waves it can (and does!) collide with the transom, knocking lumps off given enough momentum!

The long line overcomes this and if it weighs enough, takes a lot of the 'snatch' out of the process as it switches between surfing and being towed.

We did the 'bug' from Newton Ferrers (R.Yealm) to Falmouth in a 6-7 last year (with the wind behind us and diminishing) and had no problems at all once we'd lengthened the string enough! Could have been 40 feet or so away!

On other occasions we've had a towed inflatable go upside down numerous times - mostly without the outboard on it - that was just the once!

 

[Ubergeekian]

We have towed both a wooden rowing boat and a Laser Bug at different times.

As soon as the wind pipes up, the only way to deal with it is with a long line.

In bad conditions I have towed my 7'6" GRP tender by lashing it alongside. Works fine, but transferring it whilst tacking, particularly singlehanded, needs a little care.

 

[PetiteFleur]

Definitely use nylon and even some octoplait as it has loads of stretch. Polyprop should be resigned to the dustbin - useless on any boat I think.

I disagree - Polypropylene does suffer from UV degradation but the ability to float can outweigh this. I use ½" Diameter Marlow 'Nelson' hairy polyropylene for my grp dinghy as it floats and cannot get around your prop, particularly if you have it on a longish line. This size is more than strong enough for towing a dinghy. It's regularly checked and this year I shortened it by about a metre and respliced an eye onto the stem eye. I agree the very cheap blue split film polypropylene is rubbish and deteriorates very quickly. I also keep a 30m length of 1" dia. Nelson on the boat in a locker for towing - only used once in 10 years and still as good as new.

 

[alan_d]

I disagree - Polypropylene does suffer from UV degradation but the ability to float can outweigh this. I use ½" Diameter Marlow 'Nelson' hairy polyropylene for my grp dinghy as it floats and cannot get around your prop, particularly if you have it on a longish line.

I would suggest "... is less likely to get round your prop".

I managed to foul the prop of a chartered yacht in Grand Case Bay, St. Martin. The tender was a small rib which was provided with two long yellow polypropylene painters, one to each stern cleat. I was not too worried about shortening up when manoeuvring because I knew the painters would float, but a short burst of astern power was enough to get one round the prop.

 

[AndieMac]

IMO if you intend to do serious offshore (proper) dinghy towing, the rope length needs to be 200' and attached/bridled on the dink just above the waterline, on both sides, where the topsides turn in towards the bow. Attachment to the mother-ship is also a bridled arrangement to the stern cleats.

 

[whipper_snapper]

Some lessons:

Anyone think of any other lessons?

There is only one lesson from this IMO - DON"T TOW A DINGHY!!


Except for very short hops in totally sheltered water, towing a dinghy is a horrible thing to do. It WILL eventually end in tears!

 

[fergie_mac66]

short rope

I occasionally tow the dingy but I always use a very short rope tripled,so short that I lift the bows out of the water No snatch loads. The attachment on the dingy is by 3 car seat belts led tightly to the dingy transom from a loop around the (around 20 inch dia) around the bow . 2 belts go down the sides,hooked round the thole pins, and one goes along the inflated keel.

 

[Tidewaiter2]

One wonders what was more important than her husband's safety at this point.

Checking the insurance policies on him?