Repair of a 1931 Martin OM-45 - Page 2

murrmac123 · #16 07-28-2016, 05:25 AM

An elegant solution, Paul.

The straight endgrain joints on the plug caused me a bit of a "hmmm" moment, but thinking about it further it becomes apparent that the spruce patch takes care of that ... the conformation of the end grain plug joint becomes totally irrelevant. Congrats on staying within the footprint, and maintaining the value of a valuable vintage instrument.

Obviously, as you have noted yourself, the critical factor now is to ensure that the bridge never ever lifts again. There is plenty enough of the original footprint for the belly of the bridge to glue onto that this should be no problem.

Looking forward to hearing the results demonstrated in due course.

redir · #17 07-28-2016, 06:25 AM

Clever idea with the three part folding patch to fit through the sound hole. I think she'll be good to go.

I must go on record to say I disagree with the Titebond VS Hide glue though... Just had to say it

Of course being a vintage instrument hide is the traditional correct choice but fish glue would have made it a heck of a lot easier

D. Churchland · #18 07-28-2016, 06:31 PM

Question...

In doing the new patch with the top, didn't you just repeat the exact same thing that the previous guy did, albeit just with a smaller bridge plate?

John Arnold · #19 07-29-2016, 08:09 AM

No.
In the previous repair, spruce was only used in the rectangular hole. The large bridgeplate was used to reinforce the plugged hole. However, this adds unnecessary weight and restricts top vibration. And if the grain is oriented normally (perpendicular to the strings), even a very stiff hardwood bridgeplate will not provide adequate reinforcement. The bridgeplate tends to curl across the grain when subjected to string tension.
Spruce is ideal for the repair because it is lightweight, and very stiff along the grain to resist bellying. But spruce is relatively flexible across the grain, allowing vibration. This mimics the original structure of the guitar.
I repaired my 1930 OM-28 by a similar method in 1994. The one main difference was the size of the existing hole in the top, which was exactly the same size as the pyramid bridge (1" X 6"). As a result, I also installed spruce patches outside the X-braces.

Recent photo:

The discoloration around the bridge is from the oversize pyramid bridge that was previously installed. If the guitar was better cosmetic condition, I probably would have made more effort to remove the discoloration.

No one who has played that guitar has detected any problem with the sound. Notables include Tony Rice, Robert Bowlin and Larry Wexer. That is in stark contrast to guitars with oversize bridges and/or bridgeplates, which almost always take a back seat in regards to sound or resale value.
This is the repair method I prefer because it preserves the sound and structure of the guitar, using the original size bridge and bridgeplate. Since that repair (and a similar repair of my 1927 000-18), I have repeated it many, many times on customer guitars with unqualified success.

clinchriver · #20 07-29-2016, 09:30 AM

Quote:

Originally Posted by John Arnold

No.

No one who has played that guitar has detected any problem with the sound. Notables include Tony Rice, Robert Bowlin and Larry Wexer. That is in stark contrast to guitars with oversize bridges and/or bridgeplates, which almost always take a back seat in regards to sound or resale value.
This is the repair method I prefer because it preserves the sound and structure of the guitar, using the original size bridge and bridgeplate. Since that repair (and a similar repair of my 1927 000-18), I have repeated it many, many times on customer guitars with unqualified success.

I can vouch for that. Robert Bowlin was amazed as I recall. It might be the best sounding guitar I've ever played.

D. Churchland · #21 08-04-2016, 05:52 PM

John, thats an interesting method. However I don't see how having the filler piece inlaid as end gran to end grain will work. End grain does not glue well (if at all) and I'm thinking a scarf joint would be more stable since it would allow for more long grain to be available for the gluing.

mirwa · #22 08-04-2016, 06:29 PM

Quote:

Originally Posted by John Arnold

I repaired my 1930 OM-28 by a similar method in 1994. The one main difference was the size of the existing hole in the top, which was exactly the same size as the pyramid bridge (1" X 6"). As a result, I also installed spruce patches outside the X-braces.

Unusual repair.

Steve

redir · #23 08-04-2016, 06:42 PM

I've done it this way a couple times myself though after looking at this one and John's repair I like the way they did a few things differently. Anyway the end grain on end grain is moot. It does indeed not have any structural integrity but what you are doing is essentially building a 'clamp' of sorts. The inlayed patch is just there to level the surface for the bridge foot print but it's really held in there by the underlying spruce patch, bridge plate and the bridge itself.

If I understand John's repair correctly by the image it looks like the spruce patch is actually one entire unit? So that you took a larger piece of spruce and routed it down to fit the hole? That seems like the best of both worlds but either way will work. I have yet to see the ones I did years agho like that come back anyway.

Sperry · #24 08-04-2016, 07:39 PM

What a beautiful project. Thanks for all the images and descriptions!

John Arnold · #25 08-05-2016, 12:48 AM

Quote:

However I don't see how having the filler piece inlaid as end gran to end grain will work.

Redir has it right. The large area of the patch has plenty of gluing surface along the grain. The end grain parts of the joint are not important because the large patch installed under the top provides the necessary strength.

Quote:

If I understand John's repair correctly by the image it looks like the spruce patch is actually one entire unit?

Yes, one unit, which is the same as the OP guitar. I have also done them in separate pieces....one to fill the hole flush, and the larger one underneath. Both methods function the same, but the one-piece has the advantage of one less glue joint.

Quote:

So that you took a larger piece of spruce and routed it down to fit the hole?

Essentially true, but instead of routing I just carve it out with a dovetail saw, a chisel and a rabbet plane. Spruce is easy to carve by hand.

murrmac123 · #26 08-05-2016, 05:52 AM

I would love to see, from the people blithely advocating a scarf joint on this repair, a step by step, blow by blow account of exactly how they would have gone about it.

And a diagram as well.

Howard Klepper · #27 08-05-2016, 10:52 AM

Quote:

Originally Posted by murrmac123

I would love to see, from the people blithely advocating a scarf joint on this repair, a step by step, blow by blow account of exactly how they would have gone about it.

And a diagram as well.

This should clarify it for you, Murray.

BTW, you don't actually attract answers by insulting the people from whom you are asking for them. Scarfers like to think they are more intrepid than blithe. {;->

http://frets.com/FretsPages/Luthier/...restore01.html

murrmac123 · #28 08-05-2016, 02:09 PM

I think we can forego the pistols at dawn, Howard ...

... it is surely possible to be simultaneously blithe and intrepid.

I had thought of adding "without massive invasive surgery" after the first sentence of my post above.

I honestly cannot conceive of any owner, presented with the two options, acquiescing to the process to which you link, compared to the process which was actually carried out on this OM, especially in view of the testimony of the highly respected guitar players mentioned above that they could not detect any diminution in sound in an instrument with a similar repair.

Howard Klepper · #29 08-05-2016, 02:51 PM

Having the back off facilitates the repair, but it can be done through the soundhole. And the patch can be made trapezoidal so it fits within the braces if the bridge is further forward (or the braces R&R'd, which is a bunch more work).

When multiple methods can produce satisfactory results, which is often the case with guitar repair, people may differ in their judgment about whether it is worth doing extra work to create greater structural integrity.

Bruce Sexauer · #30 08-06-2016, 02:20 PM

Just in case you're feeling lonely, Howard, or possibly missed my early post in this thread, I am firmly in your camp . . . so far. I am not surprised tha the band-aid repair can work well enough that the guitar remains viable, or even superior to most, but I have to doubt that added mass does not alter it from the original result. And since I consider weight to be burden, particularly in such a case as this, I come down in favor of the less complex and and probably no more technically challenging scarf solution.

Observation: The router/jig as well as abrasives have become much more prevalent in today's version of lutherie than the truly sharp chisel and the steel cabinet scraper, which truth (IMO) seems to be at play here.