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Locating the Bridge (Read 2376 times)
killin5
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Locating the Bridge
Jan 20th, 2005 at 11:11am
 
I am just about to glue the bridge to the top of my 17 scale tenor uke.

I am curious about locating the bridge accurately. I have an 1/8 inch groove cut in th bridge to hold the saddle. When I am measuring for the placement of thhe bridge, should it be 17 inches from the nut to the front of my saddle groove or to the middle fo the groove?

I have not planned for any type of compensation on this one. I am hoping to be able to make minor adjustments by filing the corian saddle.

Any tips on this crucial step would be appreciated.

Thanks,

John
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Road_Toad
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Kalyfoonya
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Re: Locating the Bridge
Reply #1 - Jan 20th, 2005 at 7:13pm
 
If you're doing the compensation, I think there should be compensation to all strings so I would place the the front of the saddle a little farther back than the 17 1/4" length of your scale. How much?... that's hard to say. If the action is high, more compensation is needed. I'm guessing with your scale length, maybe 1 mm longer for the 'A' and make the adjustments to the saddle from there. That's about what I did on my last tenor and the intonation came out right. Hopefully others will chime in on this that have a little more experience.

Owen
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msrvfx
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Re: Locating the Bridge & Saddle Adjustment
Reply #2 - Jan 21st, 2005 at 2:57pm
 
Hi Owen & All -

I am working up a new bridge, and have been reading on several forums lately about intonation issues. It appears to be different from sopranos to concerts to tenors to baritones.
I hear sopranos seem to have the biggest problems.
It also seems to boil down to needing to adjust the location of a string, several strings, or all the strings depending on the model.
this also makes the assumption that we are just talking about GCEA tuning.
I notice on my Tacoma Cheif guitar that every string location is adjusted on it. Under an ideal situation should every string location over the saddle be different if we are talking about just tenors, or just the "C"?

I would appreciate any measurement information for saddle adjustment, or distance from the nut for each string, related to tenors.

thanks to all.

Mark in Portland ???
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Ukeman
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Re: Locating the Bridge
Reply #3 - Feb 4th, 2005 at 2:12pm
 
aloha all...

Here's my take on intoation and compensation:

First decide on a tuning and appropriate string set.

Example Tenor scale...around 17 inches...Aquilla high G setup

In this set-up the high G and the bottom A string will be your smallest diameters. The middle C and the E string will be a tad thicker.Normally the thicker strings will stretch a bit more than the thinner strings so in this case the saddle slot on this puppy should be kinda akin to the Mona Lisa smile..not the happy face kind. Most bnuilders however simply route a straight channel and move the saddle location a tad rearward when mounting the bridge to the uke! The amount "a tad "rearward is the compensation of that set of  strings. How do we get this compensated amount correct?

Heres acouple of ways:

Make a work board out of scrap one by 4 x 24..you an stiffen the piece from the underside with another scrap 1 x 2 so that the show surface is absolutely flat and true. At one end of the piece drill in a 1/16" hole in your piece to allow a string to pass through and be knotted on the under surface so it is held secure....a bit in front of this hole and inch or two make one nut slot across your work piece about 1/4" deep....make a nut about 1/2" high so it will seat in your slot and remain 1/4" or so over the work surface.

From the front edge of your new nut...yes bevel it (the nut) like you would for real rearward, measure down all the scales you like test...ie: 13 and 5/8ths, 14 and 7/8ths, 17 and 20 and 1/8th inch  soprano, concert, tenor and baritone and mark these scale lengths will a square. 

Now make a testing saddle using a piece of aluminum L metal you can buy from the hardware store. Make the designated saddle edge of your L aluminum about 3/8" high and yes with a slight bevel front to back so the foward end is your lead end.

At the end of your work piece mount a gotoh machined mini tuner dead center of the 1 x 4 at about 23 and 1/4 inch center.

Now you can go nuts and test each given string to any scale and just clamp your moveable saddle to the location of the desired string lenght via the marks you drew. Tune the string to pitch with a chromatic tuner..yes the string to pitch is loud enough for the chromatic to pick up ...now depress the string on the halfway point of your scale and listen to the chromatic...if its sharp...move your portable saddle a bit rearward..reclamp ..press your twelf fret area on the string and see what happens..you can compensate each string to the correct intonation., measure the distance to the front of the saddle and you have accurate intonation values...if you like you can double stick tape a fret board to the workboard and tune and adjust each string on an actual fretboard.

Yes, everytime you change string brands, thus changing string tension..the compensation values move...but now you got the tester and all is cool!

Low G guys slant the saddle slot a bit lower on the Low G since the strings go from fat to thin sequentially ..so the saddle slot is slanted..see acoustical guitar saddle set-ups! .......I worked out a proto universal saddle at the last exhibition...whenever I learn to transfer pictures will post...laters  ukeman
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StringDoc
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Colorado Springs
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Re: Locating the Bridge
Reply #4 - Feb 5th, 2005 at 4:40am
 
David Hurd has his own version of an intonation jig.
Go to ukuleles.com....look at the site map, scroll down to Kawika's shop tips, look for "positioning the bridge for gluing".   

I made an intonation jig for my 17in scale tenor before gluing. I measured it last night to see how far I moved the bridge back. Barely a 32nd! My slot is straight but I still intonated it for a low G. Low G is on the back edge, high A is on the front, draw a line inbetween the two and you will have it pretty close.

Nate

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Ukeman
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Re: Locating the Bridge
Reply #5 - Feb 7th, 2005 at 3:04pm
 
Aloha All!

Duly remembered that Frank Ford of Frets.Com had an article on compensation and in this he gave an actual formula for those of left brain orientation!

Use the chromatic tuner to find out how sharp you are and convert the amount of cents into a percentage. Example  you are 12 cents sharp..this now becomes 12 percent.

Now divide your scale length by the constant 17.817 and then multiply your result by the above 12 percent...this will give you the amount of compensation required for that particular string!

Pretty cool   laters  ukeman
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