Click for Mag Bay Click for Burger Click for Westport Click for Ocean Alexander Click for JetForums

lasico planimeter

Discussion in 'Technical Discussion' started by coastalrb, Jan 16, 2013.

You need to be registered and signed in to view this content.
  1. coastalrb, Jan 16, 2013
    #1
    coastalrb

    coastalrb New Member

    Joined:
    Aug 2, 2011
    Messages:
    4
    Location:
    in Westbrook ct had to sail back up the channel.
    not able to calculate ft2 with a lasico model 20 A
    tryed to follow the instructions but no luck
    CA = unit
    1 to 1 ratio
    1" to 1'
    unit = .02 x N = square ? What unit, feet, inches don't know
    Robert
  2. K1W1, Jan 16, 2013
    #2
    K1W1

    K1W1 Senior Member

    Joined:
    Sep 30, 2005
    Messages:
    7,392
    Location:
    My Office
    Hi,

    Measure a room in your house/office you know the dimensions of. Work out what unit the answer is in based on the answer you already know.

    I have not dealt with Ft and Ins for many years, I seem to recall that there would be 144 sq ins in a foot so an area 5 ft X 2 ft would be 10 sq ft, or 1440 sq ins. The same as if you had used inches all the way and multiplied 60 X 24.
  3. Garry Hartshorn, Jan 21, 2013
    #3
    Garry Hartshorn

    Garry Hartshorn Senior Member

    Joined:
    Jun 14, 2005
    Messages:
    504
    Location:
    Directly above the center of the earth
    My planimeter has not been out of it's box in many years however try the following

    Draw a series of squares of know sizes and begin with the planimeter measuring them, you will undoubtedly notice that there will be variations in your readings. This is normal and with a little practice you will get better.

    I expect you have an imperial planimeter so when you measure 1 sq inch your reading should be 1.00 this is factor N, when measuring on a drawing this is to scale and it is no longer 1 square inch.

    If your drawing is 3/4" = 1' the N factor of 1.00 is now 256 sq inches or 1.778 sq ft

    Hope this helps

    G
  4. Ward, Jan 21, 2013
    #4
    Ward

    Ward Senior Member

    Joined:
    Jan 18, 2010
    Messages:
    266
    Location:
    Vancouver BC
    A tip I remember from Kinney's book on yacht design: trace around the shape you're measuring in both directions and average the readings.
  5. Garry Hartshorn, Jan 21, 2013
    #5
    Garry Hartshorn

    Garry Hartshorn Senior Member

    Joined:
    Jun 14, 2005
    Messages:
    504
    Location:
    Directly above the center of the earth
    Francis Kinney recommends averaging several readings but I do not believe that he measures in both directions. Most plain meters only work clockwise
  6. Ward, Jan 21, 2013
    #6
    Ward

    Ward Senior Member

    Joined:
    Jan 18, 2010
    Messages:
    266
    Location:
    Vancouver BC
    It has been a long time since I read my Kinney book, so it's possible I've got it wrong. It stuck in my mind because I first read (but didn't understand a lot of) the book when I was a kid and it wasn't until much later that I had a chance to try a planimeter and I dug out the book and that's what I think it said, but at this point it's a memory of a memory, so it could be wrong.