Basic Question

[Jerryc41]

Based on your suggestions, here's what I plan to do.

1. Draw lines down from each side of the fretboard onto the top of the uke.
2. Draw a line down the center of the fretboard onto top
3. Measure proper distance from nut and add maybe 1/8". Mark top.
4. Draw horizontal line at that point, making it at right angles to center line.
5. The horizontal and vertical lines should meet at the center of the top. That is where the midpoint of the bridge will go.
6. Position bridge so the center of the saddle in on the horizontal line.

 

[sequoia]

Has anyone figure out the minimum and maximum compensation distances on a ukulele or are we all guessing?
Does someone have a better compensation figure for the front face of the nut slot than my 1/16" guess?

The problem with coming up with an exact number is that it is a moving target depending on the diameter of the strings and their height (action) over the fretboard. With my action set-up and string set I get "Pretty Good Intonation" (PGI) with 3/32 inch compensation on a 17 inch scale to the middle of the saddle.

 

[Timbuck]

There is a string compensation calculator for fretted instruments .. UU will not allow me to download the full link but you can get it here cut and paste.... liutaiomottola.com

 

[sequoia]

There is a string compensation calculator for fretted instruments .. UU will not allow me to download the full link but you can get it here cut and paste.... liutaiomottola.com

I love this site. It is a treasure trove of lutherie information. Thanks Liutaio Mottola! Here is the place on the website for doing the calculations (at bottom of page). It asks for pretty detailed data parameters but is useful.

https://www.liutaiomottola.com/formulae/compensation.htm

 

[anthonyg]

The problem with coming up with an exact number is that it is a moving target depending on the diameter of the strings and their height (action) over the fretboard. With my action set-up and string set I get "Pretty Good Intonation" (PGI) with 3/32 inch compensation on a 17 inch scale to the middle of the saddle.

I don't want to doubt that what you do works however here is a quick question. How thick is the saddle that your using?

Sure there is plenty of variation however there must be some limits that we can define which is the approach I am trying to take.

First up. There is no case ever where the actual scale needs to be SHORTER than the theoretical scale. NEVER, so this is an absolute hard point. The front face of the saddle NEVER needs to be shorter than the nominal scale length of the instrument.
As I wrote previously, if the saddle material was thick enough you could simply place the leading face of the saddle exactly at the nominal scale length of the instrument and all would be good.
However I think we can do better.
Has anyone measured the absolute least saddle compensation that they ever needed with a high A string?
Can we define the smallest amount of string compensation that will be needed?

Working out the most compensation needed is the next step but lets take one at a time.

 

[sequoia]

How thick is the saddle that your using?

To me, the thickness of the saddle does not matter that much. I file the saddle so that it has a peak for a break point and I measure from there. The peak can be set back a little for the thicker stings and forward for the thinner strings to aid in compensation. Thus a thicker saddle would be better. I use a 1/8 inch saddle which doesn't give that much wiggle room to compensate. Thus the whole saddle needs to be set back.

But really, with a reelntrant tuning system like on an ukulele, if you set the saddle parallel to the nut your ability to get perfect intonation is limited. You can get close sure, but hey, it is an ukulele and a little funk is all part of the sound. A LOT of funk is maybe not so good. It is an approximation. If I'm within a cent I call it good to go.

 

[anthonyg]

To me, the thickness of the saddle does not matter that much. I file the saddle so that it has a peak for a break point and I measure from there. The peak can be set back a little for the thicker stings and forward for the thinner strings to aid in compensation. Thus a thicker saddle would be better. I use a 1/8 inch saddle which doesn't give that much wiggle room to compensate. Thus the whole saddle needs to be set back.

But really, with a reelntrant tuning system like on an ukulele, if you set the saddle parallel to the nut your ability to get perfect intonation is limited. You can get close sure, but hey, it is an ukulele and a little funk is all part of the sound. A LOT of funk is maybe not so good. It is an approximation. If I'm within a cent I call it good to go.

OK, thanks for the information. A 1/8" saddle (4/32" or 3.2mm) is actually a reasonable size. Believe it or not many ukulele saddles are thinner. A whole bunch of my ukuleles have 2.5mm thick saddles making it 0.7mm harder to get things right.

So some maths. You offset a 4/32" saddle, 3/32" to the centreline (2/32 each side), giving you an intonation adjustment range from 1/32" to 5/32". Seems good and I'm not claiming that its wrong.
The guess I made earlier was to have an adjustment range from 2/32" to 6/32" with the same saddle but I could well be wrong.

I'm just seeing if we can collectively build up some data.

 

[Jerryc41]

I placed the bridge last night and taped over the area where it will be. I hope to apply some stain today.