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   Hello all, I'm about ready to do the gluing bridge, intonation thing on my first. Here's my question. I've used a wider saddle (a la Somogyi/Doolin). Because of this, I was wondering exactly how I should position the bridge. In the Cumpiano/Nathelson book, they mention mesuring 25.55 inched to the middle of the saddle slot, but, I'm thinking that if my saddle is 7/32 wide (as opposed to 3/32), this measurement won't apply. Seems to me I would have to add 1/16 (if I want to keep the original 6/64 between mid-saddle and soundhole) since the saddle is wider (by 2/32 each side). Does this make sense?
   I was reading up on it late last night and it seems to me there's not a whole of information as far as intonation goes. All they seem to mention is that the 1/8 slope on the lenght 'will yield excellent pitch intonation for all the strings at normal action height setting'. However, it seems to me that every guitar I see has more correction at the B string than any other. Am I missing something here, or am I just being paranoid?
   Does anyone have the exact distances for all strings (on a 25.4 scale)?   I would greatly appreciate your help on this one. Regards,

Alain Desforges

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I'd like to be able to prove, just for once, that money wouldn't make me happy...

Centerline of the saddle at center line is centerline of the saddle! The measurement did not change, just the amount of adjustment you have on each side of the centerline of the saddle for intonation adjustments. Your overall compensation is still the same. All you are really doing is giving yourself more leaway on each side of the saddle.

Scale lenght issue is subjest to the scale lenght use to calulate the fret positions. Martin 25.4 scale is 25.34 scale length plus .06 compensation I have seen some 25.4 that are 25.44 scale lenght plus .06 comp.. So to answer this you really have to know the scale lenght used to locate the slots.

Sorry I keep thinkg of things thatneed to be said here.


If you built you fretboard then you know the scale that it was layed-out to. If you bought a pre-fab fretboard and don't you can accuratly meassure the didtance from the nut edge to the 12th fret and run the calculations in T&T and reverse engineer the fretboard to find the design scale. but you need to know for sure to prperly set the bridge position.MichaelP38785.487974537

I have the fretcomp program from the MIMF - for a 25.4 scale using 12-52 gauge, the comp is given as follows:

e - 0
b - +.086 inches
G - -.009
D - +.026
A - +.086
E - +.186

I find it hard to believe that the G should be less than the true scale length, I cant say I have had this happen in practice, But I have used this program to give me bridge locations for multiscale guitars, and it definitely leaves enough room to move around an 1/8 inch wide saddle to get the intonation corrected. I position the saddle slot at the middle for the low E,and closer to the front for the high E ( again not believing that the string should be shorter than the scale length actual).

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Tony Karol
www.karol-guitars.com
"let my passion .. fulfill yours"

So this is for actual 25.400" scale length?

Yes ..

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Tony Karol
www.karol-guitars.com
"let my passion .. fulfill yours"

Yes it is a 25.4 scale length, as per instructed in the Cumpiano/Nathelson book. I built it from scratch myself and I followed the measurements given.

Michael, I understand the exact centre idea, but I thought the idea of the wider saddle was to allow a larger area of coupling (after the string break) over the saddle. I see now that if I were to move the bridge slightly back, it would give me the same amount of give towards the front (soundhole) but allow me a greater area of coupling and of adjustement toward the endpin... I'm not quite sure what I'll do. I like the idea of having more leeway on both sides, but, I also would like ot have more coupling. Decision, decisions...

   Hesh, thanks for the great info. I will try the method you described.

   Tony, thanks as well for the compensation measurements. Cheers.
   

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I'd like to be able to prove, just for once, that money wouldn't make me happy...

What Tony said about the "G" string is common place. I often find the "G" playng too flat and needing to be moved toward the nut. That's realy what you want to keep in mind when considering where to slot for your saddle - how much travel room do I need, and in what direction(s). I use Stewmac's intonation saddle jig to mark off approximate location of the saddle and then give myself room to tweak it sharp or flat as needed. Remember too, if you need to, you can always add a "shelf" on to the saddle for any one string to get the intonation right-on.





Dave-SKG38785.5945601852

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Dave Bland

remember...

"If it doesn't play in tune...it's just pretty wood"

you can also build a ghost saddle, which sits on top of your bridge until you rout the slot, just move it around until everything is a little sharp when the string breaks off the front edge, use a piece of paper to check the string is breaking off the front edge,

the other way i do it is with allen keys, then you have all the sizes you need, just move them round til you are happy and mark the slot then rout

Larger area of coupling (scratching my head)...Hummm meaning a bigger radius at the brake point. I am not sure what you gain. I have always assumed the tangent point of the intersection of the string and the saddle is a single point on that arc (theoretical tangent i.e. the upper quad. of the arc shaped into the saddle.) The only difference I see is how sharply the arc fall away from the string. None the less the only bearing point is the tangent point unless the string sets on a flat and that is no good.

If you mean the load bearing surface area of the saddle in the bridge there is a gain in load capacity there, and I think maybe you do mean this. Then that I follow you on this, but having more of this area of the saddle shifted forward of the sting contact point does not gains you much as far as eliminating possible future saddle tilt or bridge saddle channel crack protection, because the load on the bearing wall of the bridge did not change. Nor did the area of reinforcement. (thickness of the bearing wall) just the distance from the moment of action to the inner edge of the bearing wall. Depth of channel and thickness of bearing wall will add more strength, not a wider saddle.

Example lets say shallowest point of the bearing wall is 3/16” from edge of saddle to outer edge of bridge. The saddle is 7/32” or 1/8” wide either one. The forward tilting force on the bearing surface of the bridge is no different, and the weakest point is still the 3/16” from saddle to outer edge of bridge.

Now you have spread the vertical load over a larger footprint, but the percentage load that is along the plane of the strings (forward pull) has not changed and this load is what causes bridges to tilt forward.


MichaelP38785.6329861111

   Michael, I see your point about the single break point. Maybe I was explaining myself incorrectly. I decided ot use the larger saddle because of an excellent article I had read on Ervin Somogyi's web site... Here's the diagram that explains...



As he goes on to say, he doesn't have definitive scientific explanations/proofs why the wider saddle works better but he finds that in his experience, it just does.

From that diagram, I figured the string break happens nearer the nut than, say, mid-saddle. So that's why I asked my original question of moving the bridge (i.e. the saddle) a touch back to have the break point nearer the soundhole.

   My bearing wall is rather thick and the depth of the channel seems good. I forget the exact measurements at the moment, it's been a while since I've excavated the slot, but I was right on spec. with the book. The saddle should be of perfect height and not try to pitch forward too much (I'll still cross my fingers)

   Thanks for your help.

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I'd like to be able to prove, just for once, that money wouldn't make me happy...

DaveSKG

From your photo of the Stew-Mac intonation tool, that the final optimum positioning of the saddle looks like a split saddle configuration. From the e to the g as one run, whick will get the G closer and then the second set at a slighter angle to the E. Is this a way to address this? What or how do you guys feel about this approach?

I am ordering one of those tommorrow

Thanks

Mike
White Oak, Texas

OK. Now a question. Do you really have the point that the string leaves the saddle shear as in your sketch? If so are you relying solely on the saddle angle to compensate for intonation? Please don't take this as a wise crack but this looks more like a nut configuration than a saddle. I guess because I intonate each string I can’t see how I would ever end up with a shear face at the contact point.

I agree having more string in contact with the saddle on the pin side would put more energy into the bridge therefore the Bridge plate and top. I just have doubt that with out intonating the nut you can get the intonation at the saddle in a single plane. Tony’s calc show it is not a straight line from E-e. not disputing, just thinking out loud.

[QUOTE=MSpencer] DaveSKG

From your photo of the Stew-Mac intonation tool, that the final optimum positioning of the saddle looks like a split saddle configuration. From the e to the g as one run, whick will get the G closer and then the second set at a slighter angle to the E. Is this a way to address this? What or how do you guys feel about this approach?

I am ordering one of those tommorrow

Thanks

Mike
White Oak, Texas[/QUOTE]

Mike,
Split saddle is one way. I usually use a wider/thicker saddle and cut each of my points into it. Then I don't have to build any "Shelves" onto it.For instance, in the pic above( not the finished one...the one with the jig ) I used a .175" saddle (thinned some) and it hit all the points I needed. Same reason Doolin and Somogyi uses wider saddles ( although I believe Ervin likes the sound better).Dave-SKG38786.3954976852

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Dave Bland

remember...

"If it doesn't play in tune...it's just pretty wood"

   Michael, a light just went on in my head. You are most definitely right. The intonation is not a straight line... That's why I didn't like the explenation given in the Cumpiano/Nathelson book. The way they say it, you just need the 1/8 pitch and you're golden...

   I took that little sketch from Mr. Somogyi's site. I'm sure it's exagerated because such a sharp break point would certainly break strings...

   I just want to be able to use the wider area of string contact while maintaining enough space to be able to intonate correctly. I'm feeling more confident now since the saddle I'll be using is very wide. I hope to be able to accomplish both. Thanks for your help and wish me luck!

Alain

_________________
I'd like to be able to prove, just for once, that money wouldn't make me happy...