Poor Mans Rigging Strain Gage

Discussion in 'Boat Design' started by viking north, Jul 18, 2012.

  1. viking north
    Joined: Dec 2010
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    viking north VINLAND

    I did a forum search on this but no bananas. Is there a reasonably priced one on the market or has anyone come up with a unique home built device to accomplish this ? I've checked the local yacht shops but again come up with zilch. I would like to improve upon my present technique :). In the final stages of tuning the mast i have played around with --"Guesstimate" tightening; until the standing rigging was what i thought was tight enough and not overly so by the pain threshold generated in my pinky finger attaining 1/2 deflection of the stay wire. :D In this modern age of computerized electronics I would think there should be a quazi accurate backyard unit on the market. Maybe I'm not looking in the proper yellow pages ----Tnx.Geo.
     
  2. PAR
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    PAR Yacht Designer/Builder

    A good scale is your ear. Pluck each and match sounds with it's opposite. A fish scale used at the same point on respective shrouds and stays will offer an indication of balance and tightness.
     
  3. bntii
    Joined: Jun 2006
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    bntii Senior Member

    This:

    [​IMG]


    I just give the 'good enough for government work' pull then go sailing.
    Leeward shrouds will let you know if the rig needs a bit more tension..
     
  4. Frosty

    Frosty Previous Member

    A scale for this is not available probably because Its not that important to need such specific measuring equipment.

    Wood boats slack, fibre boats tighter, steel boats as tight as you want.

    (I have a feeling I have just opened a jar of worms)
     
  5. viking north
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    viking north VINLAND

    MMMmm--- seems to me the caution on rigging was overtightening. Ok I says to myself in Newfinese ,--myself I say, what is tight ? You know "BY' just tighten it up till it feels right. Christ say's I again to myself, how the hell do I know what feels right and if I don't know dat, how am I to know what overtight is. Well "BY" there must be a chart somewhere. You know dat tells ya fer a certain size wire ya should tune it to "E" above middle "C. Calling all riggers-- Calling all riggers-- come on now "BYs" post us a chart. Now 'BYs" once we gets dat chart and a few pieces of commonly used riggin wire, you know of the different sizes. Here's what we can do. We can rent a strain gage --stretch the be Jasus out of each piece until it reaches the specs on the riggers chart, hit it with one of those doctors rubber reflex hammers and see what note shows up on our guitar's electronic tuner. So PAR ya weren't so far off afterall, cuse ya gave me this :idea, :p . Now my "Son" you're some smart. What'ya think have we invented a poor mans back yard tuner ???? :D

    P.S. And i'm not on anything stronger than tea.
     
  6. philSweet
    Joined: May 2008
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    philSweet Senior Member

    Ok Viking, you know there are real gages out there that tell you in pounds what the tension is.

    First question- Do you know what you want each wire to be in pounds- based on RM30 or some such?

    Or, are you trying to proportion uppers and lowers according to some schedule?

    Or, are you trying to establish a preload based on the wire size and have designed everything else around that.

    It's hard to give you an answer without knowing the sort of accuracy and range you need. A full on rigging gage is not that much money. It is difficult to cobble one together because it has to be calibrated for every different size and construction and material. Either that or it has to be really big and awkward.

    http://www.radialengine.com/flywire/flywire2.htm
     
  7. hoytedow
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    hoytedow Wood Butcher

  8. Frosty

    Frosty Previous Member

    It should go plop on a wood boat and twang on a steel boat. It should not blow in the wind yet not distort the chain plates and pull them through the deck.

    If you stand with feet each side of the chain plate of a shroud and lean back on it, it should give --say--oh--errrrmmm about 2 inches here or there approximately--ish.

    Maybe that might be a tad on the tight side.
     
  9. Silver Raven
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    Silver Raven Senior Member

    Gooday "Dame"-Frosty(ish). Let us see if we got what you said -rrect ???

    I would have thought that if I'd - leaned back - full out - - & pulled like all heck - on it - & I got say 2" - - ******** - - I'd be pretty damn proud of myself - - - I'll go & see - what de-flection - I can get up-to & get back to you all when I've finally got a solution. Gawd knows when that'll be - - ??? But I'll keep - tightening - until I get some results. Thanks for your illumination - mate. Ciao, james - - [I'm off - to put-it - - tighter - YES]
     
  10. viking north
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    viking north VINLAND

    Phil -- just beating the bushes to draw out some of the methods the guys use. I have actually seen the riggers use the professional gages setting up the rigging on the big yachts. When I was at the yearly CoCoa Beach marine flee market in March a guy had used one for sale. I seem to recall price was $500 firm. It would have been a great opportunity for me to purchase it and start a little mobile buisness visiting the local yacht clubs. However my buisness days are winding down -- don't want no more stinkin work :). My interest in this is strickly research as I have seen more than a few boats damaged as a result of their owners overtightening the rigging on their deck or cabin stepped mast. I realize I am covering a wide range of vessels and rigging here but thought there might be some sort of factory or engineering guidelines. Also the possibility of a unique backyard technique or actual hombuilt measuring device. Maybe this has been covered before on the forum but i haven't detected it in my forum searches --so lets see what pops up-- if nothing else how not to damage that craft using a deck/cabin stepped mast.

    P.S. While my last post was somewhat tongue in cheek -- PAR did switch a light bulb on and I'm gonna play around with the idea.
     
  11. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    This question is a bit like asking how hard to make love to a woman. In reality it depends on several factors in both cases. On the rig of a cruiser, you'll be looking to have everything in column, with opposite wires ringing similarly in an ideal world, without any slack on various points of sail. It's not a matter of how tight, so much as tight enough (much like the love making thing again). You only need bar taunt standing rigging on highly tuned rigs (racers), which typically have reinforcements able to tolerate this level of abuse. A good ear and common sense is all you need. Fine tuning the rig any further on a cruiser, is meaningless and possably over stressing the rig.
     
  12. powerabout
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    powerabout Senior Member

  13. philSweet
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    philSweet Senior Member

    I went looking for that but couldn't find it. Used wrong keywords I guess.
     
  14. rwatson
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    rwatson Senior Member

    I like the previous system with a calibrated torque wrench
    http://www.radialengine.com/flywire/flywire2.htm

    rather than loosnaples, as it sounds a bit too "poor mans" for me - in the instructions it says

    " A word of caution, however: excessive pull on the lanyard, which pulls the pointer beyond the calibration mark, may permanently bend the spring and damage the gauge"
     

  15. messabout
    Joined: Jan 2006
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    messabout Senior Member

    VN there are gauges to do what you want to do. They need not be expensive either. Matter of fact I have built several tens of thousand devices that measure the tension in a membrane or screen. That was the main product of my small manufacturing firm. My instruments did not measure shroud tension but with a little modification they could have done so with great precision. Alas, my tension gauges were a bit complex and moderately pricey. Alas number two..... I sold my business last November and no longer manufacture that item.

    Here is a little research project for you. There is a popular RC model sailing boat called EC12. It is populated in great measure by techno freaks. Somewhere in their enormous information exchange are the plans for a rigging strain gauge that you can make for yourself. Start by dialing up American model yacht association. There are quite a few classes but the EC12 is what you want. The class secretary is Rick West. If you really want to do this, I'll bet that Rick will help.

    Having the distinct impresion that you, VN, are a clever old dude,
    as well as a more than competant sailor I will regale you with the following....really tight shrouds place a proportionately big column load on the mast. Seems to me that minimum practical tension is desirable unless you have some kind of rinky dink mast with a lot of wire and diamonds and such, like a Star.

    Go sailing. The lee shroud will be under less tension than the weather shroud. Measure that one like this......Make a mark on the port and stb shroud about six feet up from the chain plates. Make a mark on the mast at about the same height. Use a screen door spring to pull the lee shroud inward toward the mast. One end of the spring attached to the wire, one end attached to a marked point on the mast. (make up a C shaped piece of plywood for the mast to spring attachment and a simple hook for the shroud end of the spring. You can easily measure the spring induced deflection (sag) of the lee shroud. Tack onto an opposite course and do the same on the new lee shroud. A bit of fiddling and you can get a symetrical set of shroud tensions with this three dollar gimmick,
     
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