Towing Barge

A friend of mine kindly gave me a large cargo ship, which could be used to test the towing capabilities of the rescue boat. At over a 1m long and weighing 8Kg it provided the ideal test facility. Being another boat it could also be equip with the tow hitch facility to test various latching and towing ideas to see which one worked best.

 

 

 

The scale of the cargo ship was brought in-line with the rescue boat by adding a new cabin section and a couple of crates.

 

 

 

The Crane

Up until now, the crane on the rescue boat had not been operational. It was modified with some extra pulleys, a simple ratchet and a damper from a kitchen door into a working assembly.

The idea was that the boat would be dispatched with the crane leaning backwards, holding the hook/magnet at the correct height to match the boat being rescued. Once attached, the rescue boat would pull slowly forwards and initially all this would do is winch the crane forwards into the towing position and latch into place with the ratchet. The damper was found to be needed to stop the crane falling forwards releasing slack rope all over the place. This sequence is shown here :

Crane tilted backwards and hook set to correct height for latching.

Once latched, driving forwards started to winch crane in, through a system of pulleys.

Once crane was fully forwards the tow was started with a good length of line.

 

 

 

The tow line was equip with 2 attachments, a 3 pronged grappling hook and a rare earth magnet medallion. Either one could be screwed into the union on the end of the line. A float would also be added to the line in case the tow was lost. This would help stop the line getting caught in the propeller.

 

 

 

On the water; the barge, hook, crane and magnet were put to the test.

Several rescue scenarios were tested, to simulate different problems which could be encountered with the steam tug.

Standard tow recovery

Reverse Tow

Rescuing beached boat.

 

 

Rescue from weir grounding (against flow).

Rescue from reed bed

Open water manoeuvring and returning to port

 

Results

On the whole very successful, but a few things were learnt :

  • Trying to see what was going on at a long distance was the greatest difficulty in picking up the boat.
  • The wind was the next biggest obstacle in making a successful grab.
  • Reverse manoeuvrability was very poor.
  • The crane winch system worked fine.
  • It was easier to grab the back of the barge because the steel plate was larger. A larger plate at the front would help.
  • The grappling hook was too tricky to use but the magnet was good.
  • The absence of a float on the magnet was not a problem. In fact the weight of the magnet kept the rope taught and away from the propeller whereas a float would allow loops to form.
  • The magnet was strong enough for most scenarios.
  • Conclusion - The system should be good enough for the steam tug.

  

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