Bertram 20 remod question???

Discussion in 'Boat Design' started by Outcast, Apr 22, 2007.

  1. Outcast
    Joined: Apr 2007
    Posts: 1
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    Location: Palm City, Fl.

    Outcast New Member

    I am looking for some info from someone that has some qualified answers to my weight distribution questions for a redo on a 20 Bertram:

    Here is what I have done

    Removed V-8 and outdrive approx 840lbs

    Adding bracket and 225 4 stroke approx 520lbs motor and 185lbs bracket (keep in mid that the bracket is a positive flotation bracket that allows 250 lbs flotation)

    Moved batteries to front (100lbs)

    enlarged fuel tank from 50 to 85 gal and moved 2 feet forward

    added 12 gal fresh water tank forward of fuel tank

    ANy ideas or thoughts will help

  2. jsh
    Joined: Sep 2003
    Posts: 25
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    Location: vancouver

    jsh Junior Member


    The weight distribution is managed with the weight estimate, measured in ft-lbs,based on a common origin. When you know the position of the center of gravity for and aft (LCG) you can compare it to the center of buoyancy and get a feel for your static trim.

    Determining the center of buoyancy requires the designers knowledge or you must measure the hull and do some calculations. There is a method described in Dave Gerrs Propeller Handbook.

    Once displacement , center of buoyancy, and longitudinal center of gravity are known then you can quantify your changes.

    I am working on an inboard conversion to a stretched version of the bertram 20.They were built on license here in the 70's someone splashed the original and stretched the 20 to 22 and the 25 to 28.
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