Help requested... adding weight to keel

Discussion in 'Stability' started by New Penny, Jan 19, 2010.

  1. New Penny
    Joined: Jan 2010
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    New Penny New Member

    Dear Forum members.

    This is our story...

    My friend and I recently purchased a sailing yacht, her name is New Penny and here are her details:

    l.o.a - 25.262 feet.
    beam - 7.546 feet.
    draft - 3.937 feet
    one 8 kw disel engine.
    year of construction 1967
    material: fiberglass.

    before I start the story a "before" and "after" pics are attached:

    As you can see on of its previous owner has decided to elevate it by approximately 40-70 cm mayby even more in order to enlarge her inner space. adding all this weight(estimated as 200Kg has changed its center of mass and it's now hulling a bit too much under sails or if someone stands on the gunwale.

    Is there anyone of the distinguished forum members that can share some knowledge and\or experience about how to add weight to the keel in order to balance it and what is the best technic to do so, and is there any formulas or rule of thumb that could help us approch this project.

    Thanking you in advance.

    Mark&Elad.

    We would happly give more information if requested.
     

    Attached Files:

  2. souljour2000
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    souljour2000 Senior Member

    Not to be recalcitrant but honestly, have you given much thought to possibly doing a different major re-model?...such as returning the super-structure to it's original height and weight...and leave the keel alone...the boat would be more attractive and you've solved your keel problem.That's one man's opinion...good luck...
     
  3. PAR
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    PAR Yacht Designer/Builder

    Depending on how much weight you add to the keel, you may end up having to redo the whole rig, with increased righting arm leverage. In the industry, we call these "********" and they've earned their name over and over again.

    So, yes you can add weight, but as in all thing in yacht design, there's a cost to pay. What is her ballast/displacement ratio?
     
  4. gonzo
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    gonzo Senior Member

    The first question is : Why do you want to do that?
     
  5. TeddyDiver
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    TeddyDiver Gollywobbler

    If you bother to read the OP's first message where the why is stated "As you can see on of its previous owner has decided to elevate it by approximately 40-70 cm mayby even more in order to enlarge her inner space. adding all this weight(estimated as 200Kg has changed its center of mass and it's now hulling a bit too much under sails or if someone stands on the gunwale.

    Is there anyone of the distinguished forum members that can share some knowledge and\or experience about how to add weight to the keel in order to balance it"

    Second question please :D
     
  6. PAR
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    PAR Yacht Designer/Builder

    Teddy, had you bothered to read at least my post, you'd have found that at least some of us had read the original poster's question.

    If the CG is uncomfortably high (by new owner's standards) with just a raised deck, then ballast may not be the real issue here. This is one reason I asked for the ballast ratio. I guess you could call it "fishing".
     
  7. TeddyDiver
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    TeddyDiver Gollywobbler

    Sorry PAR, didn't mean you with my comment.. :) I agree totally with your answer to the OP..
     
  8. New Penny
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    New Penny New Member

    The displacement is not written in the certificate of registration, but I can get this info, how do I calculate the ballast\displacement ratio?
     
  9. TeddyDiver
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    TeddyDiver Gollywobbler

    weight of the keelballast/total displacement..
     
  10. PAR
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    PAR Yacht Designer/Builder

    Does the registration have a weight noted?
     
  11. alan white
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    alan white Senior Member

    I am a little confused but I think I read that the boat has already been modified, probably in an effort to stiffen up the hull. Now the current owner speaks of excessive heeling. My guess is she's overly slack-bilged, meaning lacking form stability, and the addition of add-on ballast in the past only effected final stability, but did nothing to improve initial stability.
    The boat was designed tippy, in other words, and nothing can be done to improve that aspect.
    Such boats can be seaworthy but they sail on their ear, and this can be a bit disconcerting to a neophyte sailor. Especially with additional ballast down low, she probably "stiffens up like a church" when the rail is almost under.
    I might have misread the original poster's comment, however.
     
  12. PAR
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    PAR Yacht Designer/Builder

    I was assuming the new owner's comfort level was what should be questioned here too Alan, though I've been beating around the bush. The pictures really don't show the hull well enough to see what she is, but she doesn't look very slack. I guess the better question would be what is the heel angle in 10 - 12 knots of wind on a close hauled course.
     
  13. alan white
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    alan white Senior Member

    Narrow hull doesn't help. I did misread it. The doghouse got added to the cabin top, and apparantly affected the stability somewhat. This boat was already narrow of overall beam.
    Inside ballast might be worthwhile to consider if it turns out that the additional top hamper has hurt an already marginal stability curve. The dog house doesn't look that high, actually. It may be an unfamiliarity with a traditional rounded and narrow hull shape that needs to be overcome.
    Regarding stepping on the rail which the owner says shows sensitivity to heeling------ that has more to do with hull shape than top hamper, so I'd guess the raised cabin isn't the main problem.
     
  14. PAR
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    PAR Yacht Designer/Builder

    The before and after pictures show the deck cap was raised, maybe a foot and the doghouse may have been altered as well. I don't think the beam is excessively narrow, particularly if there are any overhangs on her. A 25' boat sitting on a 20' LWL may be as much as a couple of tons, or as little as a ton, considering her general era. Stepping on the rail of a 2,000 pound boat will feel mushy if it's of a certain type.

    We'll just have to wait for a make, model or much better pictures of her general shape.
     

  15. tunnels

    tunnels Previous Member

    Simple buy another boat !! you could end up chassing your tail for ever and spending a load of money for very little if any gain !!sell it and get something closer to what you are looking for !!. If you want to go faster get a faster boat !!:p
     
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