Bow high, stern squatting

Discussion in 'Stability' started by Jolly Mon, Oct 19, 2019.

  1. Jolly Mon
    Joined: Jun 2019
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    Location: East Coast, USA

    Jolly Mon Junior Member

    I have a 1971 Morgan OI sloop. The bow is riding high and the stern is squatting. This boat has been a huge project over the last 8 years, and I recall removing an old water tank from under the V-berth which I elected not to replace. Now I am left with 90 gallons in two tanks in the engine room plus a 20 gph watermaker so just don’t need additional tankage.

    I cruise and live aboard this boat, and travel the ICW mostly with occasional coastal runs or trips to the Bahamas.

    Other than the visual of the boat squatting, when sleeping in the V-berth you can feel your head below your feet so much that you end up turning to put your head towards to bow. This makes for very close quarters for a couple.

    I’m planning to replace this weight at least temporarily with 50 lb bags of sakrete from Lowe’s. I can put 400 lbs under the V-berth in 8 - 50 lb bags. Then add or remove bags as necessary to fine tune the requirement.

    Any thoughts are appreciated.
     
    Last edited: Oct 20, 2019
  2. BlueBell
    Joined: May 2017
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    Location: Victoria BC Canada

    BlueBell Ahhhhh...

    Sounds like you need to move some weight forward or add it forward.
    How's your ground tackle arrangement?
    Need some beefing up?
    More chain?
    What about a windless?
    Move a tank forward?

    PS Be careful with terminology. Squat often refers to dynamic stern dropping due to making-way.
     
    Last edited: Oct 20, 2019
  3. Jolly Mon
    Joined: Jun 2019
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    Location: East Coast, USA

    Jolly Mon Junior Member

    Hi BlueBell,

    I’ve got all the anchor and chain I want. Manson supreme with all 3/8” G-4 chain. Also have a Lofrans windlass.

    thank you for your thoughts
     
  4. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    What is the displacement of the boat ? There must be a reason it isn't sitting on a level
     
  5. Ike
    Joined: Apr 2006
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    Location: Washington

    Ike Senior Member

    The reason is simple. He removed weight from the bow and added weight farther aft. He needs to either redistribute weight or add weight in the bow to bring it down.
     
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  6. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    I must mention that if you moved or added some 800 pounds to the stern or even 400 pounds to the stern; in order to restore the trim of the vessel; you need to double the add back.

    And in so doing, you will be lowering the boats waterline and increasing drag.

    Something as dynamic as a tank change of 40 or 80 or 90 or 110 gallons from forward to aft is no small thing.

    The best and only solution for the boat is to restore forward tanks.

    You know this and wanted someone here to bless the bad idea.

    Adding weight forward misses the obvious need to reduce weight aft.

    You are being a little cryptic about the weight change. Let's assume you took 90 gallons from forward to aft and you added a 20 gallon watermaker. Let's assume the tanks and watermaker weigh 50 pounds. You are telling us you have 110 gallons of water aft or call it 900 pounds of water and 50 gallons of gear. This would be 950 pounds aft.

    In order to fix this; you'd need 1900 pounds forward or 38 fifty pound sacks of concrete. Adding that much weight might be unsafe; so don't.

    And this is why you and the wife at say 400 pounds do nothing to affect the trim of the vessel.

    The problem with your plan is you have not subtracted the weight aft. In order to do so; you need to move the tanks.
     
  7. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    It is also important to recognize levers in this discussion.

    If you placed the water tanks in the stern nearer or closer to the vessels centerline; that must also ne factored.

    My first reply is missing that bit.

    To do math correctly; one must treat the weights as levers and consider the distances to the boats center of mass. It is 2 am here and I am dozing off. Perhaps someone can explain it further if you need or want it.
     
  8. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    The engine room presumably isn't far from the centre of flotation, he has his water tanks in there, if so no great affect on trim, the vee berth tank would have been well forward, and I doubt of much capacity, or it would have had the ability to noticeably affect the trim when empty/full. But if the trim is still way out of whack with two people right forward, there is more going on with weight changes than water tanks.
     
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  9. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    Let's make some assumptions to point out the issues.

    Let's say the lever arm of the tanks on the bow is 12 feet to center.

    Let's be generous and say the tank move was to 6 feet from the center of mass.

    If the numbers he gave are correct and my 950 pound assumption valid; he would need to addback 50 percent of the weight or 950 pounds and not 1900.

    He would need 19 bags of concrete instead of 38.

    This is a simple lever problem and well explained with seesaws in grade school science classes.

    The trouble is the lever arms were balanced with the weight forward. When you take all the weight off the seesaw and move it to the other end; in order to get the seesaw back to level; it takes a lot of lever [effort].

    If my memory serves; it is simply the dot product of distance and weight.

    But the original lever cannot be forgotten in the calculations.
     
  10. bajansailor
    Joined: Oct 2007
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    Location: Barbados

    bajansailor Marine Surveyor

    Jolly Mon, could you perhaps post a photo of your fine vessel showing her side profile?
    Then we can see how much she is trimming by the stern.
    I would be inclined to taking the 'glass half full' (rather than half empty) approach, and count your blessings, rather than your apparent misfortunes.
    Some trim by the stern can only ever improve your directional stability when under way.
    Adding a lot of weight now in the bow will greatly increase your longitudinal inertia, which will mean that you will pitch / hobby horse more when sailing to windward in any kind of sea - the energy to do so has to come from somewhere, and it is at the expense of forward speed.
    If you ever do find that you need extra water capacity (a trans-Atlantic passage perhaps?) then it is good to know that you could re-install a tank under the vee berth without too much in the way of adverse effects (apart from the increased inertia mentioned above).
     
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  11. Jolly Mon
    Joined: Jun 2019
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    Location: East Coast, USA

    Jolly Mon Junior Member

    Hi All,

    In reading all the responses I realize I could have been more articulate from the beginning. I’ll try to clarify.
    The boat came originally with two, 45 gallon water tanks in the engine room plus a water tank under the v-berth. I don’t know the capacity of the tank I removed out of the V-berth. I’m guessing from memory 8 years ago maybe 40 or 50 gallons.

    The displacement of the vessel is 23,000 lbs.

    Thank you all for your responses
     
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  12. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    best of luck; things are not nearly as bad as I feared
     
  13. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    Might to time to get a spirit level out and measure the trim angle, hard to imagine how what you describe could have led to a pronounced change.
     
  14. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    There is an easy way to solve the problem. Rebuild the V berth to be level with the new trim of the boat.
     
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  15. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    or not even a full rebuild

    all he would need is two pieces of plywood and a frame for the angle

    great post
     
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