Rig tuning

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ehh
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Rig tuning

Post by ehh »

Has any one ever tried tuning a rig by measuring the frequency of the of the tone made when the rigging is plucked?

Here is the math explained...

http://www.school-for-champions.com/sci ... uation.htm

a guitar tuner would measure the frequency, (I think).
Bikermouse
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Re: Rig tuning

Post by Bikermouse »

A standard guitar tuner will only tell you 5 notes: A, B, D, E, and G. A more expensive Chromatic tuner will show you any notes, including half-steps, but I know from experience that most have trouble with lower notes. My Boss Chromatic tuner (that cost around $80 or $90) reads the lower strings on my bass spottily at best. To use it, I usually tune the G string electronically, and then tune the other strings relative to that one.

The G is the smallest string on the bass, with relatively high tension to achieve a higher note than the others. I haven't done the math, so I may be wrong, but it seems to me that by the time you tension a shroud or stay that's thicker than the lowest bass string (even on a small boat) and much, much longer (lowering the note further) to a tension that will produce a note readable by a chromatic tuner, you'll need enough tension to either break the rigging or send the mast through the bottom.

I may be well wrong, though, once the numbers are run.
ehh
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Re: Rig tuning

Post by ehh »

I hadn't thought about it, but of course there are computer programs which analyze sound frequency. Here is a free one...

http://www.relisoft.com/freeware/freq.html

Assuming that it works all you would need is the length of your shroud and the weight per meter.

Somebody coud make a neat iPad app that would do the whole thing for you.
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Re: Rig tuning

Post by Duncan »

ehh wrote:Has any one ever tried tuning a rig by measuring the frequency of the of the tone made when the rigging is plucked?.
Is this so that you could accompany yourself, while delivering a rousing version of Frigging in the Rigging?

Could you change keys by using a backstay tensioner?

Would using Spectra be like playing classical guitar?

ok, I gotta stop... ;)
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Hirilondë
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Re: Rig tuning

Post by Hirilondë »

Even if you could identify the note a shroud plays what does it tell you? And is this information helpful?
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ehh
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Re: Rig tuning

Post by ehh »

You can calculate the tension from the frequency with the formula below


The equation for the fundamental frequency of an ideal taut string is:

f = (1/2L)√(T/μ)

where

f is the frequency in hertz (Hz) or cycles per second
T is the string tension in gm-cm/s²
L is the length of the string in centimeters (cm)
μ is the linear density or mass per unit length of the string in gm/cm
√(T/μ) is the square root of T divided by μ in seconds

By that (I think)

T= ((2f/L) sqrd) * u


BTW I see that one of those 100 dollar tuners claims accuracy to within 5%. That's not hard to beat.
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earlylight
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Re: Rig tuning

Post by earlylight »

Am I missing something here? I tune my rig by sighting up the mast to make sure the stick is in column in a static state at the dock and then I go out for a sail and do final adjusting by sighting up the stick under the dynamic load of the sails. Are you doing this as an academic exercise?
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Re: Rig tuning

Post by Hirilondë »

So you identify the sound, plug everything in to the formula and you know the tension. It tells you nothing useful regarding sail shape, center of effort, balance of the helm. You could evenly tension your mast with it leaning 10º to port and so much weather helm you can't keep from rounding up. What does this do for you? I think I will continue to tune in a manner similar to earlylight.
Dave Finnegan
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Gresham’s Law of information: Bad information drives out good. No matter how long ago a correction for a particular error may have appeared in print or online, it never seems to catch up with the ever-widening distribution of the error.
ehh
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Re: Rig tuning

Post by ehh »

Knowing the tension doesn't do anything for you unless you know what the tension ought to be. Knowing what it ought to be is another matter.
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earlylight
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Re: Rig tuning

Post by earlylight »

So you identify the sound, plug everything in to the formula and you know the tension. It tells you nothing useful regarding sail shape, center of effort, balance of the helm. You could evenly tension your mast with it leaning 10º to port and so much weather helm you can't keep from rounding up.
Rig tension is only a small part of the overall process of tuning the rig. Here is a link to an article on basic rig tuning by a sailmaker.
http://www.fxsails.com/article_rigtune.php
Hope this helps
Dick Coerse
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Re: Rig tuning

Post by jollyboat »

Thank you EarlyLight for making the correct comments.
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Drew
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Re: Rig tuning

Post by Drew »

The "rigging" on guyed communication towers is tuned using the relationship for frequency and tension. The towers are hundreds of feet tall. To adjust the guys the wires are "plucked" and the time required for the pulse to travel to the tower and back to the anchor is measured with a stopwatch. The times on each wire and transit measurements of the tower are input into software that determines the adjustment required to adjust he tower.

drew
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