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Thread: Question regarding CB & line drawings in manual

  1. #1
    Join Date
    Jul 2004
    Location
    Winyah Bay, SC
    Posts
    607

    Question regarding CB & line drawings in manual

    I was looking at the line drawings this past week (I got some stanchions! yippee! install next week...), and I took notice of 2 little details which need clarification, at least for me.

    Just where the keel flattens out on it's run aft, just below the forward edge of the aft-most salon window, the drawings indicate 2 points, one labeled "CLP", and the other labeled "CB". CB is forward of CLP by what appears to be approx. 6 inches.

    With what little NA knowledge I have (not much, I admit), I believe these abbreviations would be referring to "Center of Lateral Pressure", and "Center of Balance". Does anyone ***know*** if this is indeed correct?

    I have read somewhere (perhaps elsewhere in the manual, or on the Forum here) that the Ariels balance point was just aft of the main bulkhead, which would turn out to be about 24" in error forward of the true CB, if the CB is in reality as far aft as indicated in the drawings. Based on that erroneous information about the CB location, I'd been planning to install batteries up front, just forward of the main bulkhead. This new, TRUE knowledge changes that.

    Instead, I think I'll be putting my batteries under the settee bunks, which is just fine - less of a wire run from my solar panel that way, more room for the install, and easier to get to.

    Now, to figure out where to put some water tankage...

    Thankls for help in clearing this up!
    Last edited by CapnK; 08-11-2005 at 09:10 AM. Reason: Added to title for future searchers
    Kurt - Ariel #422 Katie Marie
    --------------------------------------------------
    sailFar.net
    Small boats, long distances...

  2. #2
    Join Date
    Sep 2001
    Location
    Asst. Vice Commodore, NorthEast Fleet, Commander Division (Ret.) Brightwaters, N.Y.
    Posts
    1,823
    Its in here somewhere.

    http://www.boatus.com/goodoldboat/brewerformulas.htm

    Can't you just move the crew-dogs around?

  3. #3
    Join Date
    Sep 2002
    Location
    Southern Maryland
    Posts
    262
    CLP does equal center of lateral pressure (important for designing the rig/sails)

    CB is the center of bouyancy, or the center of gravity of the water you displace.

    After you put the deck on the hull, outfit it, fill it with provisions, stick a rig on it, etc, you can calculate the CG, center of gravity.

    The vertical difference between the CG and CB is the righting moment. (also important for designing the rig/sails)

    If you don't know the CG of the finished boat, you can do the righting moment test, where you get your three heaviest friends, have them stand on the rail, measure the list angle, weigh them and do the math.
    (lbs total)*(distance from centerline to rail) / (degrees of list) = righting moment/degree

    (This is an approximation, because the actual righting moment/degree is not linear, but this is probably close enough.)

    There is more math to do.....but then you get into trig.....etc etc etc.
    -km
    aka, "sell out"
    S/V Beyond the Sea
    C&C 35 mkIII

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