Extreme towing

[BobPrell]

A number of comments were made on the Hot Liquid thread that the yacht's bow cleat should have been more strongly mounted. It broke away when the yacht was being towed. I wonder if this is completely reasonable, the loads applied are potentially huge when both vessels are bouncing around in waves.

This being the "practical" forum I would like to offer this suggestion.

A long time ago, there was an account published in one of our sponsoring magazines about a yacht being towed into port in very heavy weather. The owner had recently installed a VHF radio which was just the latest thing way back then. It was somewhere in the English Channel, and a french warship responded. A matelot came aboard and to the owner's surprise, he did not use the bow cleat. He rigged a loop of very heavy line around the whole hull of the yacht, supported at the right height by short strops. The tow line was secured to the loop at the bow and towing proceeded without incident.

The loop transmits the towing force to the whole hull of the boat rather than via the bow cleat. The tension in the loop tends to squeeze the boat together rather than tear it apart.

I have used this technique myself a few times, mostly when hauling boats over the ground or off the ground onto trailers. I remember seeing video of Sir RKJ and crew hauling a replica viking longship overland. The ring in the bow threatened to break the bow off the ship.

 

[Billjratt]

I wanted to post similar in the original threads but they had gone loopy by the time I got there!
My RYA man taught me to involve lashings to the mast and all available cleats when towing.
I'm not surprised the damage occured in the highlighted incident, as we don't seem to do samson posts anymore, and the wee cleat is probably classed as an anchoring facility rather than a towing facility in the small print.

 

[Twister_Ken]

I wanted to post similar in the original threads but they had gone loopy by the time I got there!
My RYA man taught me to involve lashings to the mast and all available cleats when towing.
I'm not surprised the damage occured in the highlighted incident, as we don't seem to do samson posts anymore, and the wee cleat is probably classed as an anchoring facility rather than a towing facility in the small print.

Or take a bridle forward from the sheet winches and make the towline off onto that? Strikes me that sheet winches are about the most securely mounted items aboard when it comes to resisting a horizontal force.

 

[fireball]

You're talking about using compression force - as far as I can tell - from your description it doesn't put the load over the whole hull, it puts it at the transom - on the joint between the side and the stern. It probably works better for vessels without a square transom.

My hull isn't beefed up in these locations and whilst I don't expect it to break - it doesn't appear to be designed to have a line passed around the stern for towing. If utilising that method for a substantial tow then I'd expect a bit of compression damage at the joint.

I wouldn't use the front cleats as the only point for towing either - although a Bav44 I towed did exactly that - but then with a smaller Bav as a tow boat I wasn't exactly applying the horses - that and it was flat water.

I think the issue of towing has been covered in one of the pulled threads - I was going to ask about the sensibilities of putting a line around a desk-stepped mast though - it's something that atm I wouldn't do - but only because I'm not certain as to the strength of the mast step.

 

[pvb]

I think the issue of towing has been covered in one of the pulled threads - I was going to ask about the sensibilities of putting a line around a desk-stepped mast though - it's something that atm I wouldn't do - but only because I'm not certain as to the strength of the mast step.

I'm fairly certain it isn't strong enough! The mast step is only designed for vertical force, and typically just has a few bolts screwed into the fibreglass deck to keep it in position.

 

[Talbot]

If you are installing strong points for a parachute anchor, then recomendations for the strength of this make the average cleat or winch backing look puny (at least 18" of steel strapping either side, throughbolted, with the fibreglass having been built up to spread the load to the surrounding structure).

I would suggest that towing by a powerful vessel is at least as stressful on the structure as a parachute anchor. So unless you have the parachute anchor strongpoints, any tow will need to have the towing hawser made fast around the boat structure.

 

[Hardley]

That was the method I was taught and used many times in the RN.

 

[BobPrell]

You're talking about using compression force - as far as I can tell - from your description it doesn't put the load over the whole hull, it puts it at the transom - on the joint between the side and the stern. It probably works better for vessels without a square transom.

My hull isn't beefed up in these locations and whilst I don't expect it to break - it doesn't appear to be designed to have a line passed around the stern for towing.

A good point. Some boats have transoms that might make this method impracticable.

The sailor is going to have to assess their own situation. I feel the major advantage, as stated, is that the forces tend to hold the boat together rather than pull it apart.

 

[wooslehunter]

Anyone setting up a tow needs to do it recognising the design of the casualty vessel, the sea state & the distance involved to name a few of the factors.

Many AWBs these days don't have a strong enough bow cleat for towing in heavy weather. In fact many lack any reasonable strong points foreward. Setting up a bridle is not as easy as it seems. On an AWB, some of the best points are the primary winches. But, extreme care must be taken to ensure the boat cannot sheer off to the side. A bridle attached behind the center of lateral resistance can potentially cause this. So, a line from the bow cleat to the bridle will stop it. Also, many AWBs have deck stepped masts which shouldn't be used for towing.

Basically, think about the forces of the tow lines. They have to be attached to points designed for high lateral loads. Chain plates are designed for vertical loads & can easily bend or beak under lateral loads causing the rig to drop. Same applies to deck stepped masts. Also, think of how the boat will respond when pulled from the tow point. In front of the centre of lateral resistance & the bow will come first dragging the boat behind it. Behind it & you have a potential for real trouble.

Beware too of chafing the tow line. A boat with anice strong bow cleat is great but the line needs to be fed foreward generally over the bow roller. The roller side plates can chafe through a tow line in seconds. That's why lines designed for towing have a nice heavy plastic shield around the line that can be positioned over the bow roller.

Towed boats can also veer all over the place unless they are steered at the tug. If there's any damage to the steering gear a drogue needs to be used. An alternative is to tie up alongside, but that's horrible if there's any waves or a long way to go.

It isn't as simple as it may seem.

 

[BobPrell]

That was the method I was taught and used many times in the RN.

Thanks for that. If the RN taught and used it, I am even more confident the method is sound.

 

[trapezeartist]

Someone suggested putting the bridle on the bow cleats but then running lines back from the cleats to the primary winches and winching them up drum tight. That seemed quite a good idea to me. Otherwise I would have gone for a single turn around the bow cleats, single turn around the midships cleats and finish off on the primary winches. The friction of a single turn will feed some of the load into the cleat and then pass the rest further down the line.

 

[William_H]

Towing

I like the last idea. Certainly forces in towing can be horrible. Even a small towing boat has inertia far more than horsepower. So if the line goes slack the towing boat speeds up while the towed boat slows down the shock load can be huge when it takes up.
I was once towed by a 18ft power boat. It was at night with no wind or waves. Unfortunately I was in turn towing another 2 boats in tandem from my stern cleat. Fortunately no failure but I felt quite sure the cleats would fail through the jerking motion. You needs lots of springy tow rope and good attachment.
I think most boats however would cope with rope around the hull or just around the keel. But do ensure that bow has some pull to keep it going straight. olewill

 

[euroe]

and don't forget to introduce the old tyre half way along the tow rope ( with a generous bight between the securing hitches across the diameter of the tyre) which will absorb tons of shock and save ripped up decks and cleats.

 

[LadyInBed]

Someone suggested putting the bridle on the bow cleats but then running lines back from the cleats to the primary winches and winching them up drum tight. That seemed quite a good idea to me.

+1
That's the way I would do it.

 

[nimbusgb]

and don't forget to introduce the old tyre half way along the tow rope ( with a generous bight between the securing hitches across the diameter of the tyre) which will absorb tons of shock and save ripped up decks and cleats.

Sure, I keep a spare 255*40*16 here in the lazarette

 

[savageseadog]

Someone suggested putting the bridle on the bow cleats but then running lines back from the cleats to the primary winches and winching them up drum tight. That seemed quite a good idea to me. Otherwise I would have gone for a single turn around the bow cleats, single turn around the midships cleats and finish off on the primary winches. The friction of a single turn will feed some of the load into the cleat and then pass the rest further down the line.

That's the way we moor our 38 footer, being a modern racer we don't even have cleats!

 

[Twister_Ken]

That's the way we moor our 38 footer, being a modern racer we don't even have cleats!

God, I hate having to raft up on burgers like you!

 

[Deleted member 36384]

..... rigged a loop of very heavy line around the whole hull of the yacht, supported at the right height by short strops. The tow line was secured to the loop at the bow and towing proceeded without incident.

The loop transmits the towing force to the whole hull of the boat rather than via the bow cleat. The tension in the loop tends to squeeze the boat together rather than tear it apart.

I have used this technique myself a few times, mostly when hauling boats over the ground or off the ground onto trailers. ...

There are hitches and slips used to lift tubular equipment that only rely on compression to maintain sufficient friction to keep the hitch / slip in place. Pipes used in oil wells and hoisted from horizontal to vertical with manila rope relied on the tension in the rope to keep a slip type wrap on an 8 ton pipe in place. That was old school and we now use specialist lifting devices, never the less the principle is the same.

A warp wrapped around a yacht hull produces quite a lot of surface area in contact with the hull which is also being forced into the hull, as you say, due to the compression from the tow. This compression contributes to the friction that resists the bridle being pulled along the hull. Therefore some of the towing load must be distributed throughout the hull instead of all of it being transferred across the stern.

Hull shape and surface finish (relatively rough wood versus polished gel coat) will determine the effectiveness of this. This old school method is worthy of consideration. A dedicated towing strap (similar to cargo strap material or travel hoist slings) sized for a particular circumference, wrapped around a hull may provide an excellent device (and superior to rope) for both offering and receiving tows.

 

[savageseadog]

What about a rope round the keel?

 

[pvb]

Sure, I keep a spare 255*40*16 here in the lazarette

Oh, I don't think low profile tyres are suitable!