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compensated saddle (Read 4123 times)
drfrancov
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compensated saddle
Feb 24th, 2009 at 6:21am
 
I recently changed strings on one of my ukuleles. I was using re-entrant tuning and the intonation was perfect. I am using low G tuning now and I have developed intonation problems. I realize that I need to compensate the saddle...But how do I do that?...Does anyone have measurements I can use?...Can it be done just modifying the saddle height? (like a guitar) or do I need to rebuild the bridge at an angle?...Any help is appreciated...BTW, what shaped should the saddle have?...Does it have to be inverted V shaped or round?

Thanks guys
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jack
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Re: compensated saddle
Reply #1 - Feb 25th, 2009 at 4:10am
 
Ideally your saddle should start as a gentle curve on top.  It it is still fairly flat, string it up to tune. Play the harmonic at the 12th fret, then play the note at the 12th. If the note is sharp of the harmonic, the string needs to be compensated towards the back of the saddle, if it is flat you need to shape the top of the saddle so that the bearing point of the string is moved towards the neck.
One way to get an idea of how much to compensate, is to place a small piece of a string, pependicular to each string on top of the saddle.  You then do the harmonic/note test, then move the small piece of string to change the contact area on the bridge until the harmonic and note at the 12th are the same.  You can then mark the top of the saddle on each side of small string, and shape the saddle so that the area between the marks is where the string contacts the saddle.  I hope that this is understandable, hard to describe but easy to demonstrate.
Jack
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drfrancov
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Re: compensated saddle
Reply #2 - Feb 25th, 2009 at 5:15am
 
Jack,

Thanks for the explanation. I will try that over the weekend!
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drfrancov
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Re: compensated saddle
Reply #3 - Feb 28th, 2009 at 6:06pm
 
So here is the question guys: I now understand why and how to compensate a saddle to obtain good intonation, but what can I do with a ukulele that has a saddle positioned for high G tuning when I change strings to low G tuning?....On the Hana Lima tenor plans, the bridge slot is different for high and low G to allow for compensation (saddle straight vs at an angle)...Can I achieve a similar result by shaping the saddle in a similar way: instead of a flat saddle, can shape it at an angle higher at the low end (low G) and lower at the high end (A)?...If so, how do I do it?...Where can I get reference or some numbers to use?...BTW, I am using Worth crystal clear low G strings....Thanks!
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Wood_Butcher
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Re: compensated saddle
Reply #4 - Feb 28th, 2009 at 7:35pm
 
I have seen some people post that they no longer cut the angled saddle slots when they are using the low G.  I'm not sure if that is a great idea but if it works, well what the hey.  Actually I have a Mele tenor that is low G that is built with a straight slot.  Intonation on it seems to be pretty close

You might try cutting a new saddle and experiment with crowning the top of it so that the high point is near the nut edge of the saddle at the A string and then crosses diagonally along the length of the saddle so that the high point ends up near the tail edge of the saddle at the low G string.  This would give you as much of the comensation of an angle slotted bridge as you can get without replacing your existing bridge.

Mark
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jack
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Re: compensated saddle
Reply #5 - Mar 1st, 2009 at 1:02am
 
The pupose of an angled slot is to compensate for the increased diameter of larger/stronger strings, like on a steel string guitar. It is a function of how much a string has to stretch to fret a note.  You will notice that most classical (nylon strings) have a saddle that is usually straight.  I think that you should be able to compensate the contact point on the saddle enough to change your tuning.  If you have the tools, you can cut a wider slot and use a wider (1/8") saddle which will give you more area to use in compensating.
Jack
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Don_Orgeman
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Re: compensated saddle
Reply #6 - Mar 1st, 2009 at 3:33pm
 
Jack & Mark:

When I was building my tenor uke I built a compensation testing jig using my tuners, my fingerboard with frets installed, and a 4 piece movable saddle.  I used Aquila low G strings and found that the amount of compensation needed was well within the normal saddle thickness, and that a slanted saddle was not needed.  My tenor uke bore that out.  I do not believe that using a slanted saddle for low G tuning is a good idea, unless you plan on using steel strings for a loud concert instrument.  I own about every book written on classical guitar construction and I have never seen a builder recommend a slanted saddle on a classical guitar.

Don
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Wood_Butcher
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Re: compensated saddle
Reply #7 - Mar 5th, 2009 at 3:55am
 
Don & Jack,

I agree with you idea that an angled saddle is not required for compensation.  Don, do you agree that the straight saddle should be 1/8" wide or have you gotten away with less?  I am getting ready to machine bridges for these three tenors and am looking for input before I decide what to do.

Thanks,

Mark

...
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Thanks, Mike and Asa!
 
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jack
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Re: compensated saddle
Reply #8 - Mar 5th, 2009 at 5:10am
 
Mark,
I have built 4 tenors, and because of the GCEA strings I found a 3/32 saddle was plenty thick and very little compensation was needed.
Jack
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Wood_Butcher
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Re: compensated saddle
Reply #9 - Mar 8th, 2009 at 4:04am
 
Hi Jack,

Thanks for the feed back.  Just so I am keeping this straight, you are referring to a low G tuning, correct?

Mark
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Thanks, Mike and Asa!
 
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