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Thread: Technique to weigh small boats

  1. #36
    Join Date
    May 2012
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    Central Ohio
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    521

    Default Re: Technique to weigh small boats

    Quote Originally Posted by Damian James View Post
    Back when I weighed <90kg myself, I checked the bathroom scale was good for 200kg. I weighed myself first, then picked up the boat and stepped (okay, staggered) back on... That was for a very lightweight rowing dory though.
    Little boats will balance on their nose on a bathroom scale. Padding and weight distribution recommended, of course. But they'll stay up long enough to read the scale.

    Deer scales that hang from a tree will also work for 400 lbs. or so. For more than that, I use the proportional method with a bath or spring scale, or break out my trailer tongue (hydraulic) scale from Sherline and use a car jack on each end in sequence.

  2. #37
    Join Date
    Mar 2005
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    Default Re: Technique to weigh small boats

    My customer, Nick, @PhillySailor of the infamous thread Building the Calendar Islands Yawl, use the method in post #14 and came up with what seems to be reasonable results, I would say within +/- 10lbs
    Clinton B. Chase
    Portland, Maine

    http://tinyurl.com/myboats

  3. #38
    Join Date
    Jan 2002
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    victoria, australia. (1 address now)
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    Default Re: Technique to weigh small boats

    I have gone to the local dump, they have a drive-on scale. Weigh the trailer, then both. They do it free.

    But none of my boats are big enough to worry about.

  4. #39
    Join Date
    Mar 2018
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    Annapolis, MD, USA
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    17

    Default Re: Technique to weigh small boats

    Quote Originally Posted by Peter Gottlund View Post
    On the other hand if you have the boat in hand you might try using purchase power.
    Brilliant! Get out your credit card and have someone else weight it for you. :-)

  5. #40
    Join Date
    Jul 2018
    Location
    Portland, OR, USA
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    55

    Default Re: Technique to weigh small boats

    A couple of years ago I weighed my Thistle to see how close it was to minimum weight for the class. I happen to have 400# Parcel scale with a remote read out so that made it a little easier. I started with the boat on the trailer and put the scale under each pneumatic wheel and the tongue wheel in sequence. When doing this it is important to keep the 3 trailer wheels at the same elevation so I put a block the same height as the scale under any two wheels when I weighed the other wheel. The weight of the boat and trailer is the sum of the three weights. Then launched the boat, and repeated the same thing with the empty trailer after letting the water drain off of it. Subtract the weight of the trailer from the first you have the boat weight.

    I'm sure it is not as good as a single weight using a crane scale but I expect I was within +_ 10 lbs on a 515# boat.

  6. #41
    Join Date
    Nov 2001
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    Seattle
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    Default Re: Technique to weigh small boats

    Quote Originally Posted by Canoeyawl View Post
    They use this in the Snipe class, with a sling in which they carefully balance the boats. Minimum class weight is 381 lb., if memory serves, so it's right in the ballpark for the weight you're tying to measure.

  7. #42
    Join Date
    Mar 2001
    Location
    FL
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    224

    Default Re: Technique to weigh small boats

    We have a certified scale weighing station locally to do legal weights. For smaller backyard stuff I use bathroom scales. Most Experimental Aircraft Association (EAA) chapters have scales too...those scales are on wheels and portable.

  8. #43
    Join Date
    Jul 2013
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    Aquitaine
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    859

    Default Re: Technique to weigh small boats

    I used the bathroom scales (checked against my medic's ones...) to do the wheels and hitch method. Then checked the trailer with the boat off. Both of them weigh close to 70kg. Good enough.

  9. #44
    Join Date
    Jan 2005
    Location
    Deepest Darkest Wales
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    19,836

    Default Re: Technique to weigh small boats

    Some people get incredibly fussy about weights in small boats..

    Google Lamboley Pendulum - hours of fun
    Creationists aren't mad - they're possessed of demons.

  10. #45
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    Default Re: Technique to weigh small boats

    The method in #14 seems to be doing well
    Clinton B. Chase
    Portland, Maine

    http://tinyurl.com/myboats

  11. #46
    Join Date
    Dec 1999
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    Oriental, NC USA
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    4,708

    Default Re: Technique to weigh small boats

    Quote Originally Posted by Clinton B Chase View Post
    The method in #14 seems to be doing well
    I cannot take credit for originating this method Clinton. I had heard of it previously but could not find the source when I needed to take some successive weights during a building process in order to predict the final weight of a new boat design. Probably most builders have run into the sometimes large difference between calculated and actual weight of their boat or project. I just made some calculations based on seldom used college statics to regenerate the formula. I have found it both very useful and accurate with the added benefit of being applicable in the home shop without need of any special equipment or outside help.
    Tom L

  12. #47
    Join Date
    Sep 2007
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    Benfleet Essex UK
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    386

    Default Re: Technique to weigh small boats

    The method on the windmill site works, http://windmillclass.com/static/weigh.html, I have used it several times on boats from 175lds to 700 lds in weight. It is quick & easy.

  13. #48
    Join Date
    May 2005
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    Bradford, VT
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    6,399

    Default Re: Technique to weigh small boats

    This reminds me of the story about the student given the exam question challenging him to use a barometer to find the height of a building

  14. #49
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    Seattle
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    Default Re: Technique to weigh small boats

    Quote Originally Posted by David W Pratt View Post
    This reminds me of the story about the student given the exam question challenging him to use a barometer to find the height of a building
    Dropped it and timed the fall?

  15. #50
    Join Date
    Mar 2015
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    Victoria BC Canada
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    263

    Default Re: Technique to weigh small boats

    I suspect it involved carrying the barometer to the top of the building, quickly.

  16. #51
    Join Date
    Mar 2017
    Location
    Waterbury Center, Vermont
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    73

    Default Re: Technique to weigh small boats

    With an accurate waterline marked on the hull and some forgotten calculus, I’m sure I could have figured it pretty closely.

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