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Present Vessel Im on Installs Windmills. When we sail to site or port we have to Jack Down or Up on 4 Legs. As we lost all our electronic feedback last night Jacking Up in Port How Do we Find the Average Pressure without anykind of Instrumentation on the Legs.
 

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By jacking up do you mean taking the vessel from a position where you are totally suported by the legs to a position where you are afloat
 

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I suppose as far as mean pressure on the legs are concerned, when you are afloat it is zero and when the deck is jacked clear of the water it is 100% so as you jack up the deck goes down and buoyancy takes effect so the mean pressure on the legs can be calculated by the ratio between the mean draft of the body of the rig and the mean draft when fully afloat. If the pressure when fully afloat is calculated then the mean pressure at various times during the jack up should be known. Mmmmm, it makes sense to me anyway, why do I get the feeling you are going to say B*****ks gdynia.
 

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Jeff Vessel enters port as a conventional ship. We moor up then place all 4 legs on sea bed then Jack her up like a Rig, basically making her stable but hull still partially submerged. Your on the right lines but not there by a half distance.
 

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Yes I've been aboard one or two in the river while this has been done but could never remember which way was jack up and which was jack down. I think it must have something to do with displacement. We once had a jack up at the old Readheads yard and the rig was jacked clear of the water altogether I think for inspection purposes, am I correct in saying that the pressure on the legs would be 100% in that case, and that when fully afloat the pressure on the legs is zero?
 

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Jeff Egan said:
Yes I've been aboard one or two in the river while this has been done but could never remember which way was jack up and which was jack down. I think it must have something to do with displacement. We once had a jack up at the old Readheads yard and the rig was jacked clear of the water altogether I think for inspection purposes, am I correct in saying that the pressure on the legs would be 100% in that case, and that when fully afloat the pressure on the legs is zero?
Jeff
When the electronic sensors are working you can read the pressures on each leg individually.. Dont forget for different types of seabed the operator can set these figures by the force applied. It has to do with displacement but how?
Clue. More than one displacement is required.
 

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Well they only other displacement I can think of is the displacement of the sea bed by the leg I suppose different bottoms have different density's and would maybe have to be taken into account when calculating the mean pressure on the leg, I'm not really convinced of this (Night)
 

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Jeff
Clue - Its the same as a conventional ship in ballast/ full of cargo you get drafts before and after you are loaded or discharged.
 
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