This is great information!tippie53 wrote: ↑Mon Mar 22, 2021 5:05 pm the facts
this had nothing to do with the string gauge.
The neck block changed in 1939 the original neck block was 1 9/16 thick this was changed to 1 3/8 in 1939.
they also changed the transverse brace from 5/16 and 3/4 hi to 1/2 wide 5/8 high
then the fretboard was also changed from 1 3/4 2 1/4 to 1 11/16 and 2 1/8
the warranty work went through the roof . There was a false assumption that the string tension was causing this failure and tops were cracking along the fretboard . What was happening with the thinner neck block the extension was cracking the top because of the expansion differential of the spruce and the ebony.
The solution was to place the Popsicle brace as they had in the 12 frets. This helped and thus the POPSICLE was introduced into 14 fret models in 1939
so if your neck block is under 1 9/16 use the Popsicle but you only need about 4 inches of this. Use enough to support the fretboard extension with about 1 inch per side.
Some quick measurements says the neck block StewMac sent me in the kit is 1 3/8" and the front brace is 1/2" wide by 5/8" high. So pretty well bang-on for the 1939+ specs just quoted. So it will get a popsicle brace, despite that being left off the plans.
All of the OM kits that StewMac sells are advertised as being 'authentic' copies of the 1933 OM. And (while I have no complaints about the kit) it becomes pretty obvious once you dig in that a lot of the parts are just adapted from their dreadnought model. The neck itself looks identical, but the neck block isn't - the dread neck block had a gentle radius towards the front of the body, the one supplied for the OM is perfectly flat. And it didn't match the width of the OM sides all that well as received. Even stranger, I got an e-mail from StewMac after receiving the kit telling me to check for mis-drilled holes in the neck block (it's a bolt on neck). Mine was OK on that front, but I think they may be having some QC problems with this part.
Anyway, thank you so much for the info regarding the popsicle brace. I'll feel better with it in there!
Andrew