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Over Plating


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On 03/03/2022 at 10:44, john.k said:

A large size crisp packet and tube of the sticky stuff would have saved the day........three people increase displacement how much??.....was it a weight watchers  outing?

Three people of the stern deck and the draft increases by 115mm?  Far from usual, I think 

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49 minutes ago, Tacet said:

Three people of the stern deck and the draft increases by 115mm?  Far from usual, I think 

 

I thought that too. Doesn't stand up to analysis at all I don't think.

 

Also, the lines drawn on the photo show the waterline way higher than would be normal. Generally the uxter plate sits on the waterline. On the photo, the waterline is drawn about 6" higher than the uxter plate. This does not make sense. 

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On 03/03/2022 at 09:15, MtB said:

 

 

Point of Order...

 

I can't see any mention in the report of it being a Springer in particular. Also, the photo in the report of the counter shows a conventional swim and uxter plate, rather than the "V" shaped base plate and weird counter design that most (if not all) Springers have.

 

971020646_Screenshot2022-03-03at09_09_06.png.3e0f7bcb380256e1a586b71b2bc6fac1.png

 

Also, looking at the photo, it appears the air intake freeboard WAS considered by the over-platers who appear to have raised it by the width of the rubbing band and inserted a blanking plate. The whole idea of cutting holes through the hull for air cooling strikes me as stupid though, as the result is highly predictable.

 

 

 

Here's a picture I took of the boat in Greenland Dock after the sinking.  It shows the extent of the overplating.

IMG_20120830_143850.jpg.d82213fd6c71e26172c952d68ca59930.jpg

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41 minutes ago, koukouvagia said:

Here's a picture I took of the boat in Greenland Dock after the sinking.  It shows the extent of the overplating.

 

Any idea what that huge steel 'slide' and framework is that is welded on the stern ?

 

It looks like a sort of hybrid hull . short V-sides and flat base plate.

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1 hour ago, Alan de Enfield said:

 

Any idea what that huge steel 'slide' and framework is that is welded on the stern ?

 

It looks like a sort of hybrid hull . short V-sides and flat base plate.

Could it be a collapsible frame for a pram cover?

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7 hours ago, Tacet said:

Three people of the stern deck and the draft increases by 115mm?  Far from usual, I think 

The report doesn't say that. It says after recovery it was determined that the bottom of the vent opening was 65mm above the water line. The accident happened not on a flat canal but on the Thames where even in calm weather the waves may be a few inches high. So as soon as the boat departed South Dock Marina it would have been taking in a little water from each wave crest. This would have weighed the back end of the boat down, meaning more water would be taken in from each wave crest. This must have continued for some time until the crew noticed the engine note change. By this time the engine was "half submerged", so there must have been a substantial quantity of water in the engine bay, and the back end of the boat would be a lot lower than when they set out- quite possibly already by more than the 65mm original freeboard. I can easily believe that in this situation people moving to the back of the boat could push the back end down by another 50mm, especially if they were predominantly on the same side of the boat as the vent. 

In any event it doesn't really matter whether the total drop of the back end was 115mm or not. The end result was more or less inevitable with that little freeboard in the presence of waves.

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7 hours ago, MtB said:

Also, the lines drawn on the photo show the waterline way higher than would be normal. Generally the uxter plate sits on the waterline. On the photo, the waterline is drawn about 6" higher than the uxter plate. This does not make sense. 

Well the report notes that the boat was much deeper in the water than originally designed, due to the weight of the overplating (and presumably with no corresponding reduction in the amount of ballast carried).

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4 hours ago, Mad Harold said:

Could it be a collapsible frame for a pram cover?

It is a frame that held a generator.  I took this not very clear picture shortly after the boat sank.  It had been beached just outside the entrance to Greenland Dock.

 

 

sunk boat.jpg

  • Greenie 1
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14 hours ago, David Mack said:

The report doesn't say that. It says after recovery it was determined that the bottom of the vent opening was 65mm above the water line. 

 

It also implies that the bottom of the vent was 50mm below the waterline when the three persons were on the stern deck.  It increased rather as the boat sank, of course.

 

The diagram shows the 65mm as being the distance between the uxter plate and the bottom of the vent - but that distance is, from the photos, much more.  So I can't have much confidence in the details of the report.

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18 minutes ago, Tacet said:

 

The diagram shows the 65mm as being the distance between the uxter plate and the bottom of the vent - but that distance is, from the photos, much more.  So I can't have much confidence in the details of the report.

The diagram in the PLA Safety Bulletin doesn't show any dimensions, although the text of that report stares that the bottom of the opening is approximately 65mm above the water line. The diagram in the other document posted (source unknown) clearly shows the 65mm as the distance between the "waterline in still water" and the top of the "blanking plate" i.e. the bottom of the vent opening.

21 minutes ago, Tacet said:

It also implies that the bottom of the vent was 50mm below the waterline when the three persons were on the stern deck.  It increased rather as the boat sank, of course.

The boat was already sinking before the crew realised there was a problem and congregated on the back deck.

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