Weight of Lead Keel for 50 X 8 racing sailboat

Discussion in 'Boat Design' started by cklfmba, Jun 23, 2012.

  1. cklfmba
    Joined: Jun 2012
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    cklfmba New Member

    What is the approximate range in pounds that a keel should weigh to support a 50 X 8 mahogany racing sailboat, while offering as little esistance as possible during racing?

    I have a German made sailboat built in 1914. The keel is made of lead. It is hard to measure the width which is bulbous and curvy, however the keel is 15' along the boat's hull and its depth (from hull to floor of keel) is 22" tapering to 6".

    All thoughts are greatly appreciated. I only need a general range so I can calculate needs for having the boat moved for restoration.

    Thanks so much!!!
     
  2. Stumble
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    Stumble Senior Member

    Clk,

    Measure the volume of the keel, then aproxamate it as a rectangle, or ellipse depending on which it more closely resembles. There is just too much variation in keel shape to even begin to guess at this type of thing.

    Alternatively if you know the model of the boat the numbers are probably easily accessible.
     
  3. cklfmba
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    cklfmba New Member

    Thank you very much. I've followed your advise and came up with approximately 12.5 cubic feet. Multiplied by 700 lbs per cubic foot, I get 8,750 lbs. Do you think 4 tons sounds reasonable?
     
  4. Stumble
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    Stumble Senior Member

    It sounds light for a 50' but possible.

    A Columbia 50 which was an old racer is 14,000lbs or so. But your boat is much narrower.
     
  5. PAR
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    PAR Yacht Designer/Builder

    Often you can get closer to the volume by multiplying by a qualifier, say somewhere between .7 and .8. This will account for the tapers at each end and some of the roundness. What are the physical dimensions of the keel (can you post some photos)? I think your 8,750 might be pretty close, considering you beam. What is the reason you want the ballast weight?
     

  6. HakimKlunker
    Joined: Aug 2009
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    HakimKlunker Andreas der Juengere

    You may find information here:
    There is a book: "Bootsbau-Praktischer Schiffsbau" written by A.Brix
    It is a reprint of the 1929 edition with lots of drawings of boats and yachts then made in Germany.
    I am not sure if it is available in English though.

    A practical approach from Archimedes: Build a rectangular tank around the keel and fill it with water.
    Take the weight (or volume) of the water and the difference to the full cube will reveal the exact volume of the keel.
     
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