'69 Martin D-35 reset question

[Chris Scott]

Note - edited for clarity - please re-read if you've already seen this

 

Hey folks, first post here, and glad to find a place to ask stuff a bit more "advanced"...

 

...my question involves a reset on a D-35. No major out-of-the-ordinary going on here - bridge was shaved to approx. 1/4", and even with this having been done, the action  is uncomfortably high, so after a new bridge installed we're talking a fair bit of material to come off the heel.

 

Here's where I'm at; With the new bridge (which is a Stew-Mac replacement with 1/16" bigger footprint already) I've got 3/16" from the leading edge of the saddle slot on the etreble end to the corresponding edge of the bridge, which imo is right on the edge of acceptability - the higher the reveal of the saddle, the more force pushing forward, which will increase the chances of a split. Fwiw, I've already fudged the bridge forward as much as I can without revealing any of the old glue line.

But that's not what got me concerned. I'm actually worried about is this; as I mentioned before, this one's already pretty darned under-set, and by the time it's reset properly, the (as a reference point) 12th fret is going to be a bit farther away from the saddle, as I'm "rotating" the neck AWAY  from the body in the reset process, which will obviously require moving the saddle slot even further forward, burning up more of my already small amount of material seperating the saddle from the leading edge of the bridge - am I making sense here? 

I'm wondering if anyone here has any figures that might show me just how much further away the 12th fret (again, just a reference point on the f-board) will be from the body after the reset procedure, as I'm thinking if it's more than say a 3/2nd, I might have to fabricate a new bridge with more material on the neck-side to compensate, simply to avoid the possibility of a bridge split-out somewhere down the road.

 

Thanks in advance! 

[Jeff Highland]

Works out to about 0..004"  moving the14th fret away from the  body joint due to rotation and another 0.002 from raising the string height to 1/2" from 3/8" (thereby increasing the fretted string length from 14th fret to top of saddle)

So total of 0.006 ,about the thickness of a sheet of paper

[Chris Scott]

Oh jeez, that means I'm gonna have to put a nashville tunamatic on the sucker...(:<>)

 

Hey thanks Jeff for all your time - gentleman and a scholar, you be...

 

Chris

[Greg Mirken]

I think you all are missing an important consideration that renders this discussion interesting but pointless. It is almost certain that the body distortion that has resulted in high action on a 44 year old guitar has also resulted in a decrease in the distance from the nut to the saddle. After all, that's what the string tension is trying to do; squish the guitar lengthwise. The miniscule theoretical lengthening of that distance as a result of a reset won't even return the scale length to the original value used to compute the fret locations.

In short, the saddle will not need to be moved toward the 12th fret.

[Mark Pollock]

Wait a minute - let me start a spreadsheet...  :)

Yes, and really, is there that much point to splitting hairs to this fine a degree? When there are far greater problems with guitars, such as bizarre saddle and bridge placement, three-year-old strings that are impossible to play with good intonation, etc.?

Well, no, but this was a really good thought exercise for me. Thinking about how the different elements of geometry of an instrument work together, and thinking about things in a vertical dimension that I haven't really paid attention to before was an educational experience. Also, finding out just how wrong my initial series of assumptions were (I hate to admit this, but for about a half-hour there, I was CONVINCED that the lower neck angle meant that the space between the nut and saddle got shorter.) helps me approach problems with a simpler approach.

[Chris Scott]

Thanks for chiming in Greg. I mos def get where you are coming from, and I like to think of myself as one who at least tries to keep the big picture close at hand, while simultaneously considering the details. Funny thing is, though this particular instrument came to me in barely playable condition, my saddlematic thingy registered the saddle bang - on where it should be, (the saddle slot had clearly been re-located at one time)  which only reinforced the client's comment that "...it still plays in tune", so I simply didn't want to be appreciably off the mark, so to speak.

 

We'll see how things progress.

 

 

 

[LARRY KLOSE]

Re computing the change in length of the triangle and the difficulty thereof, there's a bunch of calculators on the web that do the trigonometry for you.  For example:

http://www.csgnetwork.com/righttricalc.html

Trig was always my difficult math subject.  

Precision of the measurements will perhaps be the biggest challenge.

Larry

[Chris Scott]

Thanks for that Larry - I'll check it out!

Chris