All the older Martin fingerboards are done this way, not just the Hawaiians. The frets past the 12th are set a little closer to the bridge. I don't know the reasoning, other than to compensate for the ear's tendency to hear flat in the upper frequencies. Pianos are tuned to allow for this.

A number of different scale are often called 24.75. 24.625 is usually just rounded up and called 24.75 for instance...

A number of different scale are often called 24.75. 24.625 is usually just rounded up and called 24.75 for instance...

24-5/8" to 24-3/4" (an increase of 1/8") man, that's some mighty powerful "rounding-up". i know it's done, but it's also "advertising based" bs math.

What about when the factory does it? Martin currently lists the scale length of a new OM-42 as 25.4. Has anyone played a Martin from the 1970's - was the saddle where you would put it? And of course Gibson is notorious (from LMII)

Notes on Gibson Scale Lengths
The 24.75" scale length is commonly understood as a Gibson scale length. Gibson still advertises this scale length but it is an "abbreviation" of sorts. If you are working on an existing Gibson instrument the actual scale on the instrument may differ due to compensation and/or changes in their product line and production equipment over time. For example, we see instruments made in the early 50's cut to a 24.75" scale, in 1959 and after we find a 24 9/16", in 1969 it was 24 5/8" and after 1992 it was 24 9/16"! LMI offers a 24.75" (24 3/4") scale the 24.625" (24 5/8") scale and the 24.562" (24 9/16") scale.

What about when the factory does it? Martin currently lists the scale length of a new OM-42 as 25.4. Has anyone played a Martin from the 1970's - was the saddle where you would put it? And of course Gibson is notorious (from LMII)

Notes on Gibson Scale Lengths
The 24.75" scale length is commonly understood as a Gibson scale length. Gibson still advertises this scale length but it is an "abbreviation" of sorts. If you are working on an existing Gibson instrument the actual scale on the instrument may differ due to compensation and/or changes in their product line and production equipment over time. For example, we see instruments made in the early 50's cut to a 24.75" scale, in 1959 and after we find a 24 9/16", in 1969 it was 24 5/8" and after 1992 it was 24 9/16"! LMI offers a 24.75" (24 3/4") scale the 24.625" (24 5/8") scale and the 24.562" (24 9/16") scale.

There are two possibilities here. First, as MF suggest, there could be very slight differences in the actual scale. Gibson was notorious for changing their "24.75" scale, here is a little blurb from the StewMac website

The Gibson 24-3/4" scale is also very common, but it is also the most confusing of all scale lengths—this is because it rarely ever measures out to be 24-3/4 inches! This scale has gradually changed over the past fifty or so years due to changes in production equipment.

http://www.stewmac.com/images/fretcalc/ ... meline.gif

The other possibility is as you suggest, Martin might have "un compensated" the scale knowing that the instrument would not be fretted. I kind of doubt that because it is so subtle and most lap slide players only use the frets as indicators, you do the actual intoning with that little steel bar.

I've built a couple of Weissenborn style guitars and in that case just used standard fret locations but the saddle is not angled and there is no compensation in its location - it is exactly at the scale length. Many resonators are built the same way which is why the tend to play very sharp when fretted.

Would love to see pictures of your guitar as you build it.

Really interesting. I happen to have a 1972 D-18 I bought new. After I read your post I took it out and using my saddlematic, the saddle is a good 1/16 to 3/32" farther than what the saddlematic indicated. The middle of the saddle scale length is 25 3/8".

Maybe that's why they ended up where they are now.

Julie, Clay and Damon, here is a very well done explanation of how we got to where we are today. Julie, also note the little section near the end where David talks about the guitar that was built with a fretboard from one source and layout from another - kind of similar to your OM situation

Julie, Clay and Damon, here is a very well done explanation of how we got to where we are today. Julie, also note the little section near the end where David talks about the guitar that was built with a fretboard from one source and layout from another - kind of similar to your OM situation

https://youtu.be/0yCLckbp8ps