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130 Hatteras Donna Marie?

Discussion in 'Hatteras Yacht' started by Marmot, Nov 25, 2013.

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  1. Yachtjocky

    Yachtjocky Senior Member

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    Tonnage

    Displacement can be tonnage or pounds however measured tonnage is what is being repeatedly talked about on here. Never heard of measured pounds in registration so maybe a point to ponder.

    Often wonder about tonnage of air conditioning but then again I wonder about computer "engineers" as well. :cool:
  2. sunchaserv

    sunchaserv Member

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    I note the weight of a 100' Hatteras recently tested in PMY was reported at "displacement weight" of 270,000 pounds. I would not raise this very nice vessel in a 150 ton (300,000 pounds) sling travel-lift without confirming weight from builder and sling test and rating data from lifting yard.

    Most importantly though, I would not allow this vessel, if it were mine, to be lifted without the yard managers (guys like Marmot) providing proof of coverage, experience and capability.
  3. Capt J

    Capt J Senior Member

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    I am actually. Anyways, let me put this into really easy terms for everyone. The total weight of the boat (however you want to measure it), weighed a lot more than the lift was capable of handling and it broke the lift and then the broken lift broke the boat.

    I know a well respected surveyor who surveyed her (Sacajawea) after she was fixed and claimed that she had a LOT of issues.
  4. K1W1

    K1W1 Senior Member

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    Hi,

    Would you care to identify that well respected surveyor?
  5. Yachtjocky

    Yachtjocky Senior Member

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    Lift

    That lift apparently was capable of lifting it out but not capable of "lifting" it back into the water.

    The concrete below the winch collapsed so I suppose overall it was not capable but the winches, wires and cradle were.
  6. Capt J

    Capt J Senior Member

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    See, you've got it all wrong. It does not lift it back into the water, it lowers it back into the water.

    Well, you see, what really happened is: The mate topped off the freshwater tank after it was on land. The air in the water tank was displaced with fresh water, that ended up being 8lbs per US. gallon over what the air in the tank was. If they added the same number of total gallons in Imperial gallons, instead of US gallons, it would have weighed less and may not have caused the lift to break. That caused the weight in both actual tons, and kilograms, and pounds, as well as British pounds, to increase, and therefore the lift broke until the yacht displaced enough water to actually float because it is more bouyant then the amount that it weighs and displaced the water in the marina. ;)
  7. K1W1

    K1W1 Senior Member

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    Hi,

    I think a little conversion factor 101 is needed here Capt J.

    For the purposes of this a figure of 1 is used to represent the Specific Gravity of Fresh Water - Dock water in So Fl might vary a bit but not enough to affect the following by a significant factor.

    1 US Gal is equivalent to 3.78541 Litres ( a litre is 1000 millilitres and is the same volume in all countries).

    This gives the mass of 1 US Gallon as 3.785 Kg.

    1 UK or Imperial Gallon is equivalent to 4.545963 Litres.

    This gives the mass of 1 UK Gallon as 4.545963 Kg

    Multiply each by the conversion factor of 2.20462 ( the number of lbs in a kg) and the following will be derived.

    1 US Gal is 3.785 Kg x 2.20462 = 8.344lbs

    1 UK Gal is 4.545963 Kg x 2.20462 = 10.022 lbs

    100 US Gals would be 834 lbs

    100 UK Gals would be 1002 lbs

    A 168lb per 100 Gal difference.

    I hope you can see the pattern developing here?

    Therefore, given the foregoing the following statement is misleading to many.

  8. Capt J

    Capt J Senior Member

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    Actually you're right, I got my conversions backwards between the Imperial gallon and the US gallon.

    But, I did not even mention the specific gravity of the water in the marina yet. Since the Greek yard is fairly far up the New River, it is not true salt and leans more towards freshwater which is less bouyant. It would also depend on whether the tide was at low tide or high tide. Since at high tide, the salt content of the water in the Greek yard would've been higher and more bouyant. If it was low tide, the specific gravity of the water at the marina would lean more toward true fresh instead of true salt water, creating less bouyancy and this would also effect the 130' Hatteras as it was lowered into the water with the lift. If the water was more towards true fresh, it would cause the Hatteras to displace more water as it was launched, creating more stress on the lift. The water temperature could also effect the strength of the concrete at the time of launching as well possibly causing it to crack.

    But the story did pretty much close the thread for 12 hours until you came along......LOLOLOLOLOL
  9. K1W1

    K1W1 Senior Member

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    The Hatteras will still displace an equivalent weight in water to it's physical weight regardless of what it floats in, if it weight 300,000lbs when hanging it will displace 300,000lbs of water.

    If the water is fresh (S.G.1) it will displace approx 35,953 US Gal

    If the water is salt (S.G. 1.025)it will displace approx 35,169 US Gal


    The only way the stress would be increased on the lift would be if the weight in lbs of the vessel hanging in the slings increased.

    As it is being launched the load comes off the lifting gear.

    The SG of the marina water has no effect on the overall weight of the vessel, the winch cables might have to be let out a bit more to allow for a few extra inches of submersion of the hull.

    I had a busy morning and didn't have time to have a look at YF sooner and I took my time to craft an answer that would not be seen as inflammatory or offensive by some folks here whose skin and wet toilet paper seem to have a lot in common.
  10. Opcn

    Opcn Senior Member

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    If the water has a lower SG then a yacht that is submerged by a given number of inches or feet into it will displace the same volume of water, but that volume will generate less buoyant force. So, if the tide goes out and the SG falls a yacht will exert significantly more force on a point on the ramp further from the shore. Because the ramp is an incline plane the load will have to be positioned further out it to get further down and shift from the straps to the water.
  11. K1W1

    K1W1 Senior Member

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    Hi,

    Who has mentioned anywhere the boat being discussed was being launched down a ramp?

    As has been suggested to you before before posting you could do well to actually have some understanding of the subject you are posting about.

    Misleading posts lower the quality of the forum.
  12. Opcn

    Opcn Senior Member

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    And nastiness really improves it...
  13. K1W1

    K1W1 Senior Member

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    Hi,

    I hope you are not trying to suggest my previous post you quoted partly was nasty in a effort to deflect attention from the overall meaning of that post.
  14. Opcn

    Opcn Senior Member

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    Nope, I was wrong about how a syncrolift works. I've only seen one from a distance, since there is only one in my state and it is in facility that I've never worked in. I once had the old system there described to me, and misunderstood it to be the current system.

    On specific gravity. Even a syncrolift (I looked it up this time, don't worry, talking about the real thing now) is affected by buoyant forces. It is misleading to suggest that the only factor is the weight of the ship. All that concrete and steel displaces water. As the water gets deeper and more saline the buoyant forces on the concrete and steel parts of the lift are increased, offsetting a fraction of the weight of the installation.

    It may just be a several hundred or a few thousand pounds worth of salt and water that is displaced, but as you approach an ultimate destructive failure point that matters.
  15. K1W1

    K1W1 Senior Member

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    Hi,

    As the concrete doesn't move as a part of normal operations on any synchrolift I have seen I don't see how its water displacement has influence on the total lift capacity unless the actual foundation for the winch packs are designed/built undersized.

    When a synchrolift has a rated lifting capacity this figure should also allow for whatever is being lifted as a part of the lifting apparatus itself in addition to the weight of what is being lifted.

    The difference in density upon immersion on a yacht syncrolift will be negligible as the immersion will not be much more than 5 m in 99% of cases.

    The overall condition and upkeep of the shipyard facilities and equipment can have as much or more influence on the success or failure of a maintenance period as any other single factor save the Owner going broke.

    One thing that needs to be considered is - Had the lift involved in this thread had any damage prior to this collapse, a line left on it when a boat pulls away, a collision with a boat, prop wash eroding the river bottom around the piling, overloading etc?
  16. Opcn

    Opcn Senior Member

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    An object or structure does not have to move to experience buoyant forces. The concrete is in static equilibrium, until the balance of forces overcomes its integrity and it breaks into dynamic equilibrium. Buoyant force is one of the forces that, in this case, is working against that transition.

    Damage, deterioration, or defect is no doubt the ultimate cause. Additional weight aboard the ship (below rated lift capacity) or buoyant forces can only be a proximate cause of the collapse.
  17. K1W1

    K1W1 Senior Member

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    Hi,

    While trying to use all the terms you have picked up at school please tell me how the concrete underneath the synchrolift winch pack has any influence on what the lift can lift if the aforementioned concrete is designed/specified and built to with stand the compressive forces calculated to be exerted during the normal operation of the lift with an appropriate safety margin included.
  18. Capt Bill11

    Capt Bill11 Senior Member

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    Just for those who may be following this discussion and may need some clarification on the different "weights" being discussed in this thread:

    "Gross Tonnage - is the internal volume in cubic feet of the vessel
    minus certain spaces above the main or "tonnage" deck, like stacks and
    ventilators, which are called "exemptions" .

    Net Registered Tonnage - is obtained by deducting from the gross tonnage
    the volume of space that can't be used for paying cargo or passengers,
    that is to say the space occupied by the engines, the crew's quarter,
    the stores, etc.

    Displacement Tonnage - is the actual weight of the water "displaced" by
    the ship and is usually quoted in long tons of 2240 lbs.

    Light Displacement Tonnage - is the weight with nothing in it.

    Loaded Displacement Tonnage - is the fully loaded weight to the maximum
    and is on her summer draft in salt water.

    Deadweight Tonnage - is the difference between Light and Loaded
    Displacement Tonnage....the actual carrying capacity of the vessel.

    Panama & Suez Canal Tonnages - these are different from the internationally
    accepted definitions. There used to be a lot of variations between
    countries and the
    canal owners thought they were being conned, so they came up with their
    own definitions.

    Simplified Measurement System - The USCG decided that all this was way too
    much for bureaucrats to deal with for yachts so they came up with
    their own formula:

    Take the horizontal distance between the outboard ends of the boat not
    including rudders and bow sprits. Multiply that by the maximum beam
    outside to outside.
    Multiply that by the distance from the sheer line not including bulwarks
    or cap rails to the outside bottom of the hull not including the keel.
    Add the volume of the deck house/cabin top. Multiply by .5 for sailboats
    and .67 for power boats.
    Divide by 100.

    This will give you the "Gross Tonnage". Net tonnage is 90% of gross for
    sailboats and 80% for power boats."
  19. K1W1

    K1W1 Senior Member

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    Hi,

    Does what is posted above apply in the US?

    The rest of the world uses something slightly different.

    Tonnage measurements are now governed by an IMO Convention (International Convention on Tonnage Measurement of Ships, 1969 (London-Rules)), which applies to all ships built after July 1982. In accordance with the Convention, the correct term to use now is GT, which is a function of the moulded volume of all enclosed spaces of the ship.

    Exemptions are a thing of the past I am told, it is now done purely by calculation which it why the GT of vessels that were originally measured under the 1969 rules have a big increase when re measured under the current rules.
  20. Opcn

    Opcn Senior Member

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    I don't think I learned any of those terms in school, my degrees are in biology and chemistry. My father built homes and boats, and wrote books on the subjects, I think I learned most of it from working on homes and boats with him.

    The compression forces that you are talking about are downward forces from weight. Not just the weight of the boat, but the weight of the machinery and the weight of the concrete. If you are just designing these things in CAD it is perhaps easy to forget that they have mass and that the weight effects the stresses that lead to failures.

    The buoyant force is a countervailing force, that works against the force of the weight. If you swapped the water for mercury the concrete embedded in the earth below would be holding down the heavy steel screws instead of holding them up.

    This force is small enough that it certainly should have been within the safety margins. Just like an extra coat of paint and full tanks on the boat should have been within the safety margins. However, due to damage, deterioration, or decay the actual physical characteristics of the lift can diverge from the design characteristics.

    So, on a well built lift that has been maintained and not damaged the difference from a full tank of water or from the tide being in or out would be inside of the design safety margin. On a lift effected by damage, deterioration, or defect the difference caused by small factors can allow the lift to successfully raise a ship, but not successfully lower a ship under conditions that apply a relatively minor increase in weight. Again, it's a difference between proximate and ultimate causes.