bridge placement

[Ron Daves]

I need to understand where to place the bridge on the Tenor Uke I am finishing. On past builds, I just located the bridge by making a pattern on the plans out of tracing paper and using that to determine where the bridge goes.

I think I understand that, for starters, the saddle has to be 2 X the distance from the nut to the 12th fret. then there needs to be adjustments for correct intonation. I have read that the saddle on the base side has to be compensated about 1/8”.

Is there some kind of jig I can build? Or is there some way to get the compensation right in real time on the uke before gluing bridge down?

I am using D’Addario Nyltech strings

THANKS!

[Bryan Bear]

I'm not an uke guy so my reply may not totally apply but should get you thinking. The location of the bridge is 2xs the distance from the nut to the 12th fret plus whatever compensation you intend to add. That compensation will depend on the instrument, scale length and type of strings. Steele string guitars have angled saddles to better approximate the different compensation needs for the thick wound strings and the unwound strings. I don't believe nylon string instruments typically need slanted saddles but verify that for yourself.

Stew Mac has a fret position calculator that allows you to enter the scale length and type of instrument you are making. Along with the fret measurements, it will provide ballpark figures for the amount of compensation to add. I'm not sure if it does ukes or not but I think it does. Once you know the amount of distance you want to add to the scale length, measure from the leading edge (where the strings will exit) of the nut to the center of the crown of the 12th fret. Then add the compensation to that number. measure out from the crown of the 12th fret and locate the saddle at this new measurement. You don't want to measure from the plan and place the bridge. Measuring from the nut and 12th fret will eliminate any small variances in the location of the body and neck joint.

You can go to stew mac and look at their saddlematic. This is kind of an adjustable story stick that can be set by the nut face and fret crown then turned around to help locate the saddle from the 12th fret. You can build something workable that adds your compensation in.

[Marshall Dixon]

Is there some kind of jig I can build? Or is there some way to get the compensation right in real time on the uke before gluing bridge down?

I am using D’Addario Nyltech strings

THANKS!

I radius the back of my guitars and carefully clamp the finished guitar onto the radiused form on either side on the linings where they meet the neck. At the tail end of the form I put a screw to hold a makeshift tailpiece with the desired string spread and attach it with an old g string. Protect the linings with a piece of leather where the contact point is for the tailpiece. And of course protect the top of the instrument too, as the tailpiece will sit close to or touch the top.

I string up with an old set of similar strings with the bridge movable and find the point where the open string and the fretted octave are good. I tune to the flat side because I figure the string tension will negate that in the first few days of use. You will need to consider the amount of additional saddle compensation (to the flat side) for the several strings that will need it.
I can expect an additional 3 cents of compensation from a 3/16" thick saddle with the medium tension nylon strings I use and a 650 mm scale.

This gives the saddle position without the pull of the strings involved. To figure that I measured another guitar (of similar design) with strings under tension and with strings relaxed then factor that in.

So I bring the guitar up to pitch.
Set the bridge for good intonation and measure to the front saddle edge of the outer strings.
Relax the tension and measure again. To this measurement I add an additional 1/32" as this is the amount the bridge gets pulled forward on my guitars.

[Ron Daves]

Is there some kind of jig I can build? Or is there some way to get the compensation right in real time on the uke before gluing bridge down?

I am using D’Addario Nyltech strings

THANKS!

I radius the back of my guitars and carefully clamp the finished guitar onto the radiused form on either side on the linings where they meet the neck. At the tail end of the form I put a screw to hold a makeshift tailpiece with the desired string spread and attach it with an old g string. Protect the linings with a piece of leather where the contact point is for the tailpiece. And of course protect the top of the instrument too, as the tailpiece will sit close to or touch the top.

Could you send a picture?

[Marshall Dixon]

Could you send a picture?

Here are pictures of the one I most recently threw together for a 7 stringer I'm working on. I mocked it up on a 6 string in the finishing process and didn't put the tuners in or the nut in place. And the strings need to be long enough to make this work.

Anyway, this will give you the idea.

[Marshall Dixon]

I said in my original post that I placed the bridge on the finished guitar, but have been gluing the bridge on in the white.

[Chris Reed]

All the ukes I've made need some compensation on all strings. For a tenor, I'd estimate 1mm or a fraction more for the high A, probably 2mm for the low C. If you plan a low G, then maybe 2.5mm for that. But those last two numbers might be 1.5 and 2mm.

I don't try to get the compensation exact in advance. I position the saddle just in advance of where I estimate the high strings need to be, so on a tenor I'd place it at scale length + 1 mm. Then I string up and compensate each string individually by filing back the saddle peak. A 2mm saddle is just wide enough, a 3mm saddle gives plenty of scope. This is the only way I know to get the intonation as spot on as is possible. And if you're using re-entrant tuning, you have to do it this way, otherwise either the low C of the high G will be substantially out.

For linear tuning (low G) a slanted saddle will get you close, but not exact. I'd position it 1mm back on the treble side, 2mm back on the bass side, and then be prepared to file back the saddle peak at an angle.

Bear in mind that whatever compensation you decide on will only work for that particular set of strings. So if you compensate for Aquila Nylguts, you'll be out for Fluorocarbons, and vice versa! Similarly, compensation changes if you raise or lower the action.

All of which is why I build the thing, set the 12th fret action where I want it to be, and then do the compensation afterwards.

[Alain Lambert]

If not too late, her is how I do it.
I glue my bridge after finishing.
My tenor has a scale length of 17 inches which is 431.8 mm
I get correct intonnation by placing the saddle CENTER at 434.5 mm form the nut edge, which is 2.7 mm of compensation.
I use a 1/8 ( 3mm) saddle so this give me +- 1.5 mm of adjustment for fine tuning.
I put masking tape where the bridge should go. Then carefully place the bridge so the saddle center is at 434.5 mm and the bridge is square to the center line.
Then I check the left-right alignment by placing a ruler on each side of the fretboard and making sure the bridge (bridge holes) is equally spaced on both side.
Once I am satisfied, I tape the bridge to the top so it does not move. I then trace the outside with a pencil. I also drill 2 very small holes in the saddle slot though the top and place 2 small finishing nails as positionners.
I can now remove the bridge and cut the tape 1-2 mm inside the pencil line and remove the tape under the bridge position.
The finish under the bridge position is scraped, I use hide glue, so I preheat the bridge put glue under it place it back using the 2 positionning nails and clamp it.
Once dry, I string the uke and use APTuner to check intonnation of each string filing the saddle top forward or backbard as needed.
This work for me!

[Ron Daves]

I built a jig for placing the bridge. I got it set up with a preliminary compensation, clamped everything down and strung up the number one and four strings and this setup tuned correctly when plucked open and harmonic. The action on this set up is a bit high and I’m hoping that doesn’t affect how it tunes
I am hoping I’m not missing something.