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VIDEO - Sunk Bertram Discussion

Discussion in 'Bertram Yacht' started by YachtForums, Jan 15, 2010.

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  1. Henning

    Henning Senior Member

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    You bet, for first the week or two after it sank, it was probably barely on the bottom. A significant storm moved through the area after the sinking. As you are probably aware, the currents in that area can be strong without any exceptional conditions. Run a storm through and that sucker just bounced along the bottom. The current position is a mile and a half from the reported point of loss. Bouncing along the bottom in a storm causes awful amounts of damage. All the damage outside of the initial bow collapse is easily explained by this factor. When it sank, the fuel tanks (and water and and sewage) all in front of the engines and running gear (the only bits of the whole boat that have serious negative bouyancy), so every time a surge picks her up and moves her 8", she comes down on the back corner of the boat, thunk, that's also what broke the rudders out. The transom broke away right at the stress load corner lines. Nothing surprising.

    Sea water is figured at 64lbs/cuft. 500lb lift bag is about the size of half a twin mattress. There is no change to ultimate bouyancy with depth, however, if you are lifting something with less than a full bag, you will have to release the expanding volume of gas on your way up, or it will accelerate out of control as the volume of the air expands with the reduction in environmental pressure. If you fill the bag to overflowing at 3000', it will have the exact same bouyancy at 3'.
  2. tommymonza

    tommymonza Guest

    Did you look at the video again where i mentioned about 10 seconds in to the footage of the transom there is the hole where the stern cleat was.Explain that .

    Also what power did this boat have and what is the weight of the engines and gears.

    I can except the weight of the fiberglass being offset by the foam core that remains but there is tons of dead weight in machinery there to be moved also.

    The water tank if empty is providing a lot of bouyancy and also the holding tank but at what stage was the fuel tank emptied ? Immediatly after the sinking and than i would assume the fuel in it became displaced by sea water ?

    So If you had to dead lift it off the bottom with a crane what would your scale say for weight ?
  3. Henning

    Henning Senior Member

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    Remember, a full fuel tank will provide bouyancy at over a pound per gallon... a full fresh water tank at nearly half a pound.

    My bet is that the scales on it supported in the water column is now around 3500lbs. The fuel wasn't removed, to the best I can put together, until the same trip where the divers took the video and anchored the boat because it was still moving.....

    I'm not sure which engines it has, but I remember them videoing the datatags.
  4. tommymonza

    tommymonza Guest

    From the spec sheet i am getting the mtu 1825 12v series 2000.

    I have yet to find a weight on the engines anywhere, top secret i guess.

    Water is 350 gallons and lets say it was half empty so 175x64=11200lbs of bouyancy .

    I don't have the figures for the holding tank but lets call it a 100 gallons and it was empty.

    100x64=6400lbs of bouyancy so so far we are at 17.600lbs of bouyancy with out figuring are fuel tanks out yet.

    How many hours were they into the trip that morning ? And what is the max fuel burn?
  5. Marmot

    Marmot Senior Member

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    I thnk you need to revisit the density difference between fresh and salt water.
  6. tommymonza

    tommymonza Guest

    Hi Marmot

    Can you work these bouyancy figures for me please.

    1850 gallon fuel tank half full=

    350 gallon water tank half full=

    100 gallon waste tank empty=

    Thanks Tommymonza
  7. Marmot

    Marmot Senior Member

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    What kind of tree are you barking up and what are you barking at ...

    (For the benefit of our international readers, that is from an old rural American saying "You are barking up the wrong tree." which means the hunting dog thinks it has something of value trapped in a tree and is making a lot of noise telling the hunter that it has found the prey.)
  8. Marmot

    Marmot Senior Member

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    I can but I won't because you won't learn anything by me giving you the answers.

    You could have done it yourself in about the same time it took to ask someone else to do it for you.

    And not least, you are asking for buoyancy figures, does this mean you believe the tanks are partially filled while submerged?
  9. tommymonza

    tommymonza Guest

    Not barking up any tree just trying to get a grasp on whether the boat was almost at nuetral bouyancy on the bottom.

    Just got the weight figures on the engines at 7200 each with the gears

    So 7200x2=14400 plus lets throw in another 15,000 for generators ,batteries, a/c , reefers. shafts ,wiring .and and other non bouyant hardware.

    Leaves us with almost 30,000 pounds dead weight on the bottom if you take the hull out of the equation,but lets be realistic and put 10,000 back in for the hull from the chine area down.

    So we are at a 40,000 pound total.

    To be realistic i don't see how that boat weighs 90.000 pounds, The bottom must be 6 inches thick.
  10. tommymonza

    tommymonza Guest

    Come on Narmot. I know you are thinking the same thing I am thinking..
  11. BUIZILLA

    BUIZILLA New Member

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    I know of a salvor that did exactly that on a boat that burned and sank off Key Largo, so he could get first shot at the pickings.... not uncommon...
  12. BUIZILLA

    BUIZILLA New Member

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    also, wasn't it reported that the vessel was found approx. 1 1/2 miles SOUTH of the sinking position?

    now, with a northbound current velocity Gulfstream push, and prevailing winds to support that... how exactly could that happen? :rolleyes:

    ahhhhhhh, equator gravity...
  13. NYCAP123

    NYCAP123 Senior Member

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    Actually, although I don't have the information in front of me, I believe the prevailing current in that area is southerly. Certainly the surface winds and currents were southerly as they were southbound with a following sea.
  14. Marmot

    Marmot Senior Member

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    Sorry, but "I haff no idea vatt you are sinking about." But, if your questions are any hint then, no, we are not thinking the same thing at all.
  15. BUIZILLA

    BUIZILLA New Member

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    studying the video...

    does anybody have any idea of the length/mass of the torn away square area of that foredeck?? 25'x?? maybe more...

    that's a HUGE piece that was possibly folded back, and up against the bridge forefront, before it broke off, certainly as high as the tower, and above the hardtop height... that's just a HUGE and heavy piece..

    and nobody saw that happen and/or where it went?
  16. alacrity

    alacrity New Member

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    could it be that the manufacturer did not want pics of a boat at the bottom of the ocean with its name on it? how terrible would that look?
  17. geriksen

    geriksen Senior Member

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    I was thinking the same thing...
    to move it somewhere only u can find it later, or to just make it disappear completely.
    We had a sailboat go down here and when they went to get it just a day or two later the entire rig was missing. There was another one that was a powerboat that went down on the edge of a deep drop off. (many suspected insurance fraud), it was located quickly but when they went back to raise it, it was gone.
    The divers think it got drug over the edge of the cliff it was on.

    If it went with the current, it may be that is all that happened. Partial buoyancy allowed it to move with the current...

    But then there is the transom...
  18. NYCAP123

    NYCAP123 Senior Member

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    Real-time wave & current information in the nearshore at

    Springmaid Pier, SC

    Bin Number Height above seabed (meters) Current Speed (meters/second) (knots) Current Direction (degrees)

    1 1.55 0.067 (0.130) 215
    2 2.05 0.076 (0.148) 206
    3 2.55 0.083 (0.161) 219
    4 3.05 0.103 (0.200) 218

    Bin average 0.082 meters/second (0.160 knots) toward SW (214 degrees)
  19. capitano_65

    capitano_65 Member

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    Maybe an uninsured owner did not want the boat found? Who knows....