View Poll Results: Have you used a Mechanical Planimeter For Boat Design

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  • A what?

    5 18.52%
  • Heard of them - never seen one

    4 14.81%
  • Seen one - long ago

    5 18.52%
  • Used one long ago - was there something about Simpson's rule?

    3 11.11%
  • Used one but nothing to do with boats

    4 14.81%
  • Used one regularly before we switched to Computerised Draughting

    2 7.41%
  • Still use one occasionally

    4 14.81%
  • Could not manage without it

    0 0%
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Thread: Mechanical Planimeters - Care and feeding thereof.

  1. #1
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    Default Mechanical Planimeters - Care and feeding thereof.

    I have never owned or used a planimeter - 'cos I'm a dedicated cheapskate and even back when drawings were done on paper (or film) there were (still are) cheap and effective alternatives.

    However as an interesting piece of tech history and quondam magnificent piece of mechanical engineering - I admire them - much as I admire mechanical calculators and spiral slide rules.

    But there must be naval architects - professionals and amateurs who have used them for real commercial work - and there may be some who still do.

    Lets have a poll.

    Feel free to comment, recount amusing anecdotes etc....
    Someday, I'm going to settle down and be a grumpy old man.

  2. #2
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    Default Re: Mechanical Planimeters - Care and feeding thereof.

    I have also used one of these in anger.


    and seen one of these in use.
    It really is quite difficult to build an ugly wooden boat.

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  3. #3
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    Default Re: Mechanical Planimeters - Care and feeding thereof.

    Quote Originally Posted by P.I. Stazzer-Newt View Post
    spiral slide rules.

    ..
    I'm a huge fan of tools, devices, gadgets, jigs, fixtures etc, anything that simplifies a task.
    I've seen slide rules, never understood them, but "spiral slide rule" ?!! you got me there. I may have to Google it.
    The Planimeter looks awfully complex and expensive, so I'll have to live without one.

    Thanks for bringing it up

    Cheers
    Norm
    Do sceptics ever get sceptical about their own scepticism?

  4. #4
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    Default Re: Mechanical Planimeters - Care and feeding thereof.

    Unless you are a professional, in which case you'll probably be using CAD anyway, you'll only find occasional use for them. Still and all, they are fascinating instruments. Do you absolutely need one? Of course not, but then, who needs a wooden boat either? However, once in a while, every so often, it's nice to have an instrument that will give you the surface area of an irregular plane surface. So, if you think you might need to do that, and you don't want to spend thousands of dollars for quality CAD programing and construct the shape digitally before you can measure it, a good planimeter is what you need.

    They can be found fairly regularly on eBay for less than $100. Read Keuffel and Esser's Compensating Polar Planimeter Manual to understand the features of the various models. http://www.mccoys-kecatalogs.com/KEM...Polar_1963.htm Given the relatively low cost, there's no reason not to buy the "super deluxe" Paragon model, which was K&E's top of the line. This is the Paragon model number 620015. There's one listed right now for $79.00 that looks to be in decent shape. (Most are, as they were bought by professionals and cared for appropriately.) See: (http://www.ebay.com/itm/Keuffel-Esse...53.m1438.l2649) There are other makes, many quite old. Leave those for the collectors. The K&E 620015 was "state of the art" for mechanical planimiters through the 1970's or so. There were some electronic models made that had digital readouts, but I wouldn't trust spending money on one of those. Precision mechanical scientific instruments are made to last forever. Nothing electronic lasts forever, or even for long. A nice clean 620015 is an heirloom.

    So why the 620015 Paragon model? First, while other makes are available, the K&E manual is readily available and with the antique odd-ball makes, while attractive to instrument collectors, it's hard to know what you are getting and good luck finding an instruction manual listing the required settings. Equally well-made K&E planimeters are available on eBay for as little as $15.00, but they lack the features of the 620015. The 620015 model can be set to just about any scale one could imagine, and reads out in both English and metric measurements. The less fancy models have fixed settings as to English or metric and less range in terms of scale settings. A limited planimeter that is made for cartographic work may only read in acres, which isn't going to be useful for naval engineering. A K&E 62015 will yield readings suitable for everything you might ever want to measure.



    Each 620015 was individually calibrated at the factory and comes with tools to confirm it's continued accuracy in both metric and English measurement units. The manual, which is available on line (URL above) gives all the settings to yield various units of measurement.

    Definitely a fun toy and conversation piece. There's not a lot of folks out there who've seen one.

    See previous forum discussion at: http://forum.woodenboat.com/showthre...nimeter-Anyone
    Last edited by Bob Cleek; 10-17-2017 at 04:39 PM.

  5. #5
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    Default Re: Mechanical Planimeters - Care and feeding thereof.

    Quote Originally Posted by normil View Post
    I'm a huge fan of tools, devices, gadgets, jigs, fixtures etc, anything that simplifies a task.
    I've seen slide rules, never understood them, but "spiral slide rule" ?!! you got me there. I may have to Google it.
    The Planimeter looks awfully complex and expensive, so I'll have to live without one.

    Thanks for bringing it up

    Cheers
    Norm
    Look for a Fullers cylindrical slide rule. Complicated to use but ten times as accurate.
    It really is quite difficult to build an ugly wooden boat.

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  6. #6
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    Default Re: Mechanical Planimeters - Care and feeding thereof.

    Quote Originally Posted by normil View Post
    I'm a huge fan of tools, devices, gadgets, jigs, fixtures etc, anything that simplifies a task.
    I've seen slide rules, never understood them, but "spiral slide rule" ?!! you got me there. I may have to Google it.
    The Planimeter looks awfully complex and expensive, so I'll have to live without one.

    Thanks for bringing it up

    Cheers
    Norm
    Fairly easily found - but sometimes pricey
    http://www.ebay.co.uk/itm/VINTAGE-CA...sAAOSwAr9ZibhG
    Someday, I'm going to settle down and be a grumpy old man.

  7. #7
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    Default Re: Mechanical Planimeters - Care and feeding thereof.

    I have one and use it now and then.
    They're on Ebay for not much and don't take much room.
    If you want to do anything with hydrostatics of a boat that's just on paper, there's no alternative.

  8. #8
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    Default Re: Mechanical Planimeters - Care and feeding thereof.

    I lusted after one for a long time.Then one turned up on ebay at a very reasonable price and I bought it.Turns out I don't actually need it very much as other than trying it out on a scanned and enlarged set of hull lines,I haven't used it.Free CAD software seems to be more accurate and more versatile.

  9. #9
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    Default Re: Mechanical Planimeters - Care and feeding thereof.

    In the early seventies I used a planimeter similar to Bob Cleek's in post 4 to find areas of roads, footpaths and plots of land etc.
    It fascinated me how a polished wheel turning and sliding over the plan could come up with an accurate figure. With no internet then I could not find an explanation.
    So I checked now for how it works and found this site. http://www.math.harvard.edu/~knill/t...ter/index.html
    The first paragraph is
    "The polar planimeter is a mechanical device for measuring areas of regions in the plane which are bounded by smooth boundaries. The measurement is based directly on Green's theorem in multi-variable calculus: the planimeter integrates a line integral of a vector field which has constant curl". He lost me at multi-variable calculus.

    I liked using slide rules, at least I could understand how it worked having done logarithms.
    One of the senior engineers had a cylindrical slide rule.
    It was a great day when we got our first electronic calculator.

  10. #10
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    Default Re: Mechanical Planimeters - Care and feeding thereof.

    One of my boating friends is an old school naval architect/surveyor and he offered to run the hydrostatics on a Gartside design that I am modifying. I got to see him use the planimeter and of course Gartside's numbers were pretty much right on.
    Steve B
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    "If a man must be obsessed by something, I suppose a boat is as good as anything, perhaps a bit better than most." E. B. White

  11. #11
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    Default Re: Mechanical Planimeters - Care and feeding thereof.

    There needs to be a poll response that says: “bought one on eBay that was advertised as ‘complete’, was missing important parts and so was non-operable and I’m still looking for one where I can trust the seller”.
    Heute ist so ein schöne Tag...

  12. #12
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    Default Re: Mechanical Planimeters - Care and feeding thereof.

    Quote Originally Posted by Peerie Maa View Post
    I have also used one of these in anger.

    Showed the thread to SWMBO - Who said "I've used one of those for field areas from maps.
    Someday, I'm going to settle down and be a grumpy old man.

  13. #13
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    Default Re: Mechanical Planimeters - Care and feeding thereof.

    I used to use one long ago to measure the areas of indicator diagrams taken from marine diesel engines.
    https://en.wikipedia.org/wiki/Pressure_volume_diagram
    https://dieselship.com/marine-techni...ator-diagrams/
    Nick

  14. #14
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    Default Re: Mechanical Planimeters - Care and feeding thereof.

    Quote Originally Posted by P.I. Stazzer-Newt View Post
    Showed the thread to SWMBO - Who said "I've used one of those for field areas from maps.
    It will do areas, as does a planimiter. Its main purpose is first and second moment of area, used in stability calculations and longitudinal strength of a hull.
    It really is quite difficult to build an ugly wooden boat.

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    Default Re: Mechanical Planimeters - Care and feeding thereof.

    Quote Originally Posted by Peerie Maa View Post
    Look for a Fullers cylindrical slide rule. Complicated to use but ten times as accurate.
    How did you measure that accuracy?
    There is nothing quite as permanent as a good temporary repair.

  16. #16
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    Default Re: Mechanical Planimeters - Care and feeding thereof.

    Quote Originally Posted by Peerie Maa View Post
    Look for a Fullers cylindrical slide rule. Complicated to use but ten times as accurate.
    Then there's Thacher's Calculating Instrument, which goes for anywhere between $750 and $1,000 on fleaBay these days!


  17. #17
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    Default Re: Mechanical Planimeters - Care and feeding thereof.

    Quote Originally Posted by Don Z. View Post
    There needs to be a poll response that says: “bought one on eBay that was advertised as ‘complete’, was missing important parts and so was non-operable and I’m still looking for one where I can trust the seller”.
    Bummer! Damn antique dealers list stuff and don't know what it is. As they say, "The pictures are part of the description." The trick is to go to the on-line catalogs of the manufacturers and then study the pictures closely to make sure everything's all there. I've seen a lot of those "complete" listings with stuff missing. The drafting instrument sets are the worst. Sellers will substitute the weirdest stuff in the French-fitted instrument cases to make the set look like there aren't any pieces missing. Damn rip-off artists.

  18. #18
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    Default Re: Mechanical Planimeters - Care and feeding thereof.

    Just in case anybody's interested in a good planimiter:

    Super deal on a Keuffel and Esser #620015 Paragon planimeter newly posted on eBay. (Usual disclaimers apply.) This one looks complete with velvet lined case, adjusting templates, and manual and in very good condition with bidding starting at only $19.00. They usually go for between $75 and $100 in this condition.

    https://www.ebay.com/itm/K-E-Compens...EAAOSwOA1Z8Pa2


  19. #19
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    Default Re: Mechanical Planimeters - Care and feeding thereof.

    Quote Originally Posted by Stiletto View Post
    How did you measure that accuracy?
    Have you ever used a slide rule?
    It really is quite difficult to build an ugly wooden boat.

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  20. #20
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    Default Re: Mechanical Planimeters - Care and feeding thereof.

    Quote Originally Posted by Peerie Maa View Post
    Have you ever used a slide rule?
    Of course! But not for a long while. There's more computing power at my fingertips on my iPhone than in a gazillion slide rules. Who would have thought it would come to this back when we were in high school?

  21. #21
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    Default Re: Mechanical Planimeters - Care and feeding thereof.

    So does anybody remember these? They were the cat's meow for a brief moment in time... until the hand-held electronic calculators came along.



    They are still bringing $1,500 to $3,000 on eBay.

  22. #22
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    Default Re: Mechanical Planimeters - Care and feeding thereof.

    Quote Originally Posted by Bob Cleek View Post
    Of course! But not for a long while. There's more computing power at my fingertips on my iPhone than in a gazillion slide rules. Who would have thought it would come to this back when we were in high school?
    I was asking Stiletto. His question was a tad off the wall so I was wondering.
    You are right about the speed of obsolescence though. Moore's Law now applies bigtime.
    It really is quite difficult to build an ugly wooden boat.

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  23. #23
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    Default Re: Mechanical Planimeters - Care and feeding thereof.

    I was given a planimeter years ago by my father in law, i used it ocasionally but since i got Delftship i havent used it! As for slide rules I found a nice cased one at a boot fair for the princely sum of 50 pence. I gave it to my son Nick who at the time was aged 15, Father in law showed him how to use it & being good at maths he took it to school. He was using it in a maths class & the teacher was fascinated, He had never seen one used! And so Nick ended up showing the teacher how to use a slide rule.

  24. #24
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    Default Re: Mechanical Planimeters - Care and feeding thereof.

    Quote Originally Posted by Bob Cleek View Post
    So does anybody remember these? They were the cat's meow for a brief moment in time... until the hand-held electronic calculators came along.



    They are still bringing $1,500 to $3,000 on eBay.
    Yes I have used one. Beautifully made and satisfying to use at a time when the alternative was the size of a typewriter.

    I googled images for 'mechanical calculator', it brought up a range of different gadgets.

    I just caught the end of mechanical calculators as electronics took over.

    Punch card operated programmable computers were also coming in.

  25. #25
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    Default Re: Mechanical Planimeters - Care and feeding thereof.

    Quote Originally Posted by oldcodger View Post

    I just caught the end of mechanical calculators as electronics took over.

    Punch card operated programmable computers were also coming in.
    You and me both. Our office still had 3 or 4 mechanical calculators gathering gust whilst hydrostatics were run on the mainframe from punched tape. I still lave spools of the tape for tick strips when lofting by hand.
    Our first PC lived in a room of it's own, and was so lacking in power that there was no room for code to terminate the hydrostatics and stability programmes. One had to use the un-interuputable override switch in the wall.
    It really is quite difficult to build an ugly wooden boat.

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  26. #26
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    Default Re: Mechanical Planimeters - Care and feeding thereof.

    Before planimeters - back in the 16 or 1700's, I think - some guy measured the areas of all the counties of England by cutting up a map and weighing the counties. Also cut out a square of known area based on the map legend, as a standard.

    Sort of like the old way of finding center-of-lateral-plane by cutting out a drawing of the sub-waterline hull and balancing it on a straightedge.
    I will beg you for advice, your reply will be concise, and I will listen very nicely and then go out and do exactly what I want! (Apologies to Lerner and Lowe.)

  27. #27
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    Default Re: Mechanical Planimeters - Care and feeding thereof.

    Care and feeding of a mechanical planimeter? I would prefer to polish it, put it in a glass case on the wall and carry on with my electronic Placom KP-90 digital planimeter. I get the figures straight off the readout at whatever scale I want, it will if I ask it average five passes to get better accuracy from my wobbly tracking, and is most undemanding in maintenance needing new batteries about every two or three years.

    John Welsford
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  28. #28
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    Default Re: Mechanical Planimeters - Care and feeding thereof.

    Quote Originally Posted by Peerie Maa View Post
    I was asking Stiletto. His question was a tad off the wall so I was wondering.
    I had used one only briefly when introduced to them as a kid, so effectively no. I was wondering how something becomes ten times more accurate than a conventional slide rule.
    Ten times more divisions on it?
    Sorry, if it seems a rude question. On things I dont know about I like to ask questions. Please forgive my ignorance.
    There is nothing quite as permanent as a good temporary repair.

  29. #29
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    Default Re: Mechanical Planimeters - Care and feeding thereof.

    The Spiral/Cylindrical rules are approximately ten times as long as the conventional straight rules - and can thus be read to much better accuracy.
    Someday, I'm going to settle down and be a grumpy old man.

  30. #30
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    Default Re: Mechanical Planimeters - Care and feeding thereof.

    Quote Originally Posted by Stiletto View Post
    I had used one only briefly when introduced to them as a kid, so effectively no. I was wondering how something becomes ten times more accurate than a conventional slide rule.
    Ten times more divisions on it?
    Sorry, if it seems a rude question. On things I dont know about I like to ask questions. Please forgive my ignorance.
    Not a dumb question if you are unfamiliar with how a Fullers cylindrical slide rule works.
    A conventional slide rule has log scales about a foot long, and can normally only be read to 3 significant figures.
    The log scales on a Fullers spiral round the cylinder allowing them to be much longer than on a conventional slide rule (500 inches), so can achieve 4 significant figures.
    It really is quite difficult to build an ugly wooden boat.

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  31. #31
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    Default Re: Mechanical Planimeters - Care and feeding thereof.

    Quote Originally Posted by P.I. Stazzer-Newt View Post
    Showed the thread to SWMBO - Who said "I've used one of those for field areas from maps.
    I covet an integrating planimeter for the sheer awesomeness of an ingenious gadget. Meanwhile my CAD package cranks out the center of a 2D area faster than I can look up from the keyboard.

    Ken

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