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• View topic - Stranded narrowboat in Oxfordshire - River Thames

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PostPosted: Mon Feb 15, 2016 9:41 pm 
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We were called to work in conjunction with JT Mackley and to devise a plan to retrieve this stricken vessel. Apparently it broke loose from its mooring on Monday (01/02/16). Both it and another boat went uncontrolled down the river until they became stuck by the Osney bridge. The first boat was successfully rescued by the agencies. Unfortunately, when the fire brigade attempted to winch the second boat to safety it ended up across the river. We have had a lot of rain recently and the velocity of the water was too much for their methods. It broke loose and became jammed across the river. The massive weight/force of the river was bearing against the side of the hull and it listed badly before taking on water and sinking.

Various methods were attempted and failed. You can see from the photos that there was an attempt made to pump the boat out. They were going to float the vessel to safety but conditions etc. prevented this method from succeeding. A crane was suggested and it was calculated that a 500T lift would be required as there were problems with the bridge loadings etc. All attempts/approaches were not suitable for various reasons.

We attended on Thursday afternoon (04/02/16) to assess the situation. High rainfall was forecast for the weekend thus it was imperative that the obstruction was moved as soon as possible, otherwise flooding up river would become a distinct possibility.

The boat weighed approximately 26T and is 65ft long. It was full of water and the estimated weight of this was a further 18T. Boats rely on 'up-thrust' to stay afloat and this form of displacement creates lift on an object. In this case there was none. The boat was on the bed of the river in places. It would be very difficult to calculate the side thrust on the boat. One would have to be an expert in fluid dynamics and any research carried out to quantify the force was futile due to the many variables present. The width of the river, depth of the water, slope of the surrounding land, time of day and gaps beneath and in front of the boat etc. all influenced calculations. Of course, all of this would alter rapidly as soon as the boat began to move.

We were aware of the weight, although this would change dramatically as the weight was taken from the front of the boat as water would run to the rear. The vessel is flat bottomed and a plan was formed where we would use two rotators and a ramp constructed in front of the boat. The wall was reduced in height and a local survey carried out for services etc. The plan was to set up the 1075 in front of the boat, leaving enough room to use the elevated boom to provide an element of lift, a tractive force and a righting action. The two 60,000lb winches were used as two part lines via 12T snatch blocks. The blocks were attached to two deck drain holes via 16mm chains. The drag winch was also used as a two part line to provide tractive and directional effort. This was connected via two 8T slings which were arranged to form a 'bridle'. This was also attached to the hull via two 16mm chains. One of the auxiliary winches was arranged to run from the boom to the tailgate of the wrecker, and then to an 8T block which was anchored to a cluster of trees. The cable terminated on the starboard side of the boat. This gave directional control and also provided the opposing force we desperately needed to balance the force created by the river. We also had to monitor the legs on the 1075. When carrying out a heavy winching operation, the legs should be retracted, they are designed to support load and not be pulled. We did use the spades to help create an anchor, but we also had to have the legs extended as we were using the boom at a high elevation.

The second recovery vehicle (NRC) was set up in the gardens/allotment area at a 45°angle to the other vehicle. A special track had to be formed from timber mattings as the ground was so soft. Both winches were to be used to give stability to the rear of the boat. Again, the weight of water would try to force the boat down river as soon as it was freed. The cables were taken across the river in a small boat. Connecting to the rear of the boat was difficult as there were very few points which we felt were adequate for the loads that may be imposed. We were not allowed on the boat due to safety reasons and the current was so strong that the divers on scene would not enter the water.

You could witness massive changes in the water's behaviour as it was forced against the side of the boat. It created a large number of what look like whirlpools on the up-river side, and a massive torrent on the down-river side as the pressure was relieved. These were particularly dangerous conditions and extreme care had to be taken. The divers managed to pass slings through the rear deck drains, although they were much smaller than we would have liked. We settled for two 4T endless loops to attach each winch cable to the rear of the boat.

A large tree hampered this part of the process. It fell in line with the route the cables would take as the boat was recovered. We decided to pass cables either side of the tree, so as one ran out of its ability to stabilise, the other would take over. The divers had to study our method statement to ensure they understood how we required the rigging to be arranged. Virtually all the rigging arrangement was duplicated as any form of failure would be catastrophic; we just could not leave room for error.

We disconnected the pump which had been left there from previous rescue attempts and the recovery began. We took an element of weight on the rear cables. The 1075 then began by initially taking a light pull on the auxiliary winch whilst the O/S boom winch took some of the load. The drag winch was tightened and finally an amount of weight taken on the N/S boom winch. This process was repeated several times until the boat was close to the wall.

We had calculated the distances to allow the boat to have its front raised and then be winched forward approx 10ft before we had to reposition the 1075. The boat was secured to two trees via chains/tensioners whilst this was done. It was important that the distance was correct when setting up the booms/winches etc. It is always tempting to be 'too greedy' and stand too far away but this will result in operating the boom without sufficient angle, not providing enough lift and loading the equipment excessively. We had to constantly monitor the NRC's winches to ensure that they did not become a hindrance as the boat moved forwards.

Eventually the boat was totally out of the water. We had been assured that the boat was totally flat bottomed – it wasn't! There was a large support bracket and support welded to the underside at the rear of the boat which supported the rudder. Fortunately we had gas cutting equipment. Although it was awkward, the bracket had to be cut off just before it touched the wall. This allowed us to continue moving the boat until we finally got it to the desired point. It was placed on blocks ready for examination etc. after which it will be taken away.


This job received quite a lot of media attention, here's a couple of links to be BBC articles:

http://www.bbc.co.uk/news/uk-england-ox ... e-35472028

http://www.bbc.co.uk/news/uk-england-ox ... e-35506435



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