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Hi I have a couple of plans for a 14 fret OM. I want to build a 12 fret OM sized guitar and understand that the bridge plate and bridge will have to move further down the lower bout but does the X brace move down as well? Does the soundhole stay in the same position as for the 14 fret model. This assumes I will be using the same scale length as for the 14 fret plan which is what I want to do.

Cheers, Bob

You might want to take a look at the StewMac 000 plans.

http://www.stewmac.com/How-To/Blueprint ... _Plan.html

The term "OM" implies 14 frets.

http://vintagemartin.com/om.html

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It's not what you don't know that hurts you, it's what you do know that's wrong.

If you build the 14 fret body with a 12 fret neck the bridge moves down and the X will open, a 12 fret OM is quite different from a 14 fret.

are you doing this on a 14 fret body or 12 fret ? Remember the bracing also goes with it. if your doing it like a Norm blake. You don't have to shift it all the way I shift it so the braces are on the front of the bridge corners.
I also us 18 frets this sets the hole closer to the original position.

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Semantics: It's not an OM unless it has 14 frets by definition. It may be OM shaped, OOO sized or you could call it an OMLO (OM like Object.... ).

As mentioned "000" 14th fret is the style/shape/size --- OM Orchestra Model technically is in reference to the scale length (long scale 25.34") ---more string tension = more volume --- there was a period where Martin offered OM versions in most body sizes and shapes. In today's vernacular its seems the "000" 14th long scale is referred to as the OM.

Regarding the OP, we (KMG) offer a stencil/template with our interpretation of the "000" 14th body shape that is modified to accept the 12th fret neck the bracing is such that the bridge wings rest on the "X" lower bout legs and the intersection is in a desirable location.

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Ken Cierp

http://www.kennethmichaelguitars.com/

Interestingly I was in the National Musical Instrument Museum at the University Of South Dakota recently (an amazing place) and they had a mid 20's Martin 000 12F and mentioned that it had a 25.4 scale length.

I had built a couple from the StewMac plans a while back that were great guitars and was starting another that was on my bench in MN when I visited the museum. Somehow I thought it was 24.9 and made the fretboard and neck for it already. I didn't bother to go back and look at the plans.

When I saw the one in the museum I thought whoops did I screw up. Sure enough when I got home I got the plans out and it was 25.4. Had to make a new neck and fretboard but I can use the other on one of my size 2's

As it turned out my bracing and bridge plate were OK as the locations I marked on my template were for the correct scale although there is not much difference.

_________________
It's not what you don't know that hurts you, it's what you do know that's wrong.

Per the Martin History book
the first OM and to this day it is still called the OM was made in 1929. This was also the birth of the 14 fret body for martin,
Copied from the Martin History Book 1st edition pg 51

The 14 fret neck came into the picture in 1929. It came in response to a request of one of the periods most respected professional banjoists , Mr Perry Bechtel of Atlanta Georgia . Perry visited the Martin factory about the matter in October , 1929. He and many others who had been banjoists were looking for a way to change to the guitar. The banjo had fades along with the saxophone at the end of the decade if the 1920s.
Mr Bechtel made his suggestion of a fourteen fret neck and it appealed to Martin. At once the worked up a sample guitar in style 28 , and Mr. Bechtel like it very well. Martin made a few more like it and within 6months the had offered to the trade the new style OM-28 ( Orchestra Model , Meaning fourteen frets to the neck). Essentially these guitars were martins 000 size redesigned for the longer neck. This may have been the first regular flat top to appear regularly with the longer neck.
The fourteen fret neck was so well received that Martin extended the feature to other models in their line. In short order itbecame the standard design for most models , and for the American guitar industry. The fourteen fret neck had been previously used for the arch top guitars.
The OM was discontinued as a prefix after 1933 , when Martin went back to the000 designation for the 14 fret models of that size. The only real difference between the the OM series and succeeding 14 fret 000 guitars was scale length. The OM had a 25.4 scale ( measured from nut to saddle ) , whereas the 000 following it had a 24.9 scale as did the 0 and 00 sizes. We might mention that we have seen 000 models from about 1934 which had the long scale but with the 000 stamped designation, so there was at least for a short term overlap. More information on the OM series is included in the OM guitar styles section ( referring to the book ). The OM appeared again in 1977 when interest was revived among ragtime and other finger picking styles.

So in a nut shell the original term OM wasn't about the scale length per se but in reference to the new 14 fret neck used on flat top guitars.
NOTE OM section of the book
The OM section of the book does state that the big difference of the OM compared to the 000 was scale length.

_________________
John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Since a standard definition for an OM has become more muddled and really has never been clarified I see even Martin has taken scale length off their general spec sheet and also now group OM and "000" in the same section

https://www.martinguitar.com/featuresma ... etype.html

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Ken Cierp

http://www.kennethmichaelguitars.com/

seems a bit of semantic fussing here. When i convert 14 to 13 to 12 fret for L-00's i just shift the whole bracing pattern and soundhole down by the correct distance. I do use two shoulder braces for 12 fret joint. pretty sure that'll work fine.

I didn't intend to stir a pot but to add to the history based on the Martin side of the story. Ken Ceip is right as far as the scale length today though that is more of what it became that what it started as. 14 fret necks are now the norm but in the early days for martin they were rare. Today the OM is always long scale . Also with the bolt on neck there were few short scale necks with this feature , a few mostly on customs.

Martin did things differently than did Gibson. Gibson didn't change the body as Martin did. What is interesting is there is only 1 known martin 13 fret , an arch top and it is in the museum.
As stated braces are placed based on scale length so if you know where the nut is , you will know where the saddle goes so you can plot the bracing from that point.

_________________
John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Thank you everyone for all your input. I now have a much better idea of what to do.
Cheers, Bob

Here's a list that DannyV posted a while back when there was a similar discussion.


Alex

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