I thought Frank's article on the repair of the top sink on a Gibson K-2 mandocello was certainly up there with his usual level of excellence in wizardry. Of course it would be fun reading for most folks (I posit) but for myself, the owner of a 1936 K-1 with the same problem, it was a really interesting piece.
My K-1 is not as serious as the one in the repair article.
On my K-1 when I remove the tension of the D'Addario J78's the top returns to its normal convex contour viewed from the outside. In fact, if I tighten the strings just enough to secure the bridge in place in looks perfect (pic attached).
So, I thinking. I should be able "just" to remove the back plate (like Frank did) and then shore up the top with a new transverse brace under the bridge like he did? There a no end block or neck block issues with mine and I would not have to to the plaster of Paris mold and reshaping the top. So a much smaller scale project I think.
But. And here is my REAL question. By putting a new brace under the bridge, Frank altered the original Gibson design -- of course he HAD to as the original design had proven inadequate.
But if you are going to change it anyway what do folks on this forum think about just X-bracing the top? Maybe even adding X-braces and taking out the original transverse brace? Thoughts pros or con?
I am thinking the X-bracing might make less change to the tone/volume of the mandocello then the extra transverse brace under the bridge. Just a "gut" feeling....1936 Gibson K-1
Thanks for all the comments. I am primarily interested in preserving the tonal character of the instrument -- I'm not really too concerned about the "collector value' of it.
Thus, I am focused on what kind of bracing will both 1) prevent the top sag and 2) still retain the maximum tone and projection of the instrument. My only interest in X-bracing would be if it served to be the best way to maximize those two criteria.
Of course it is kind of impossible to get an answer to this question a priori. I have not yet made contact with the owner of the K-2 that Frank Ford fixed -- but I did send him a PM from the Mandolin Cafe. He posted a video of playing Bach on the instrument on YouTube -- I commented on the video and in his answer he suggested that the extra transverse brace might have reduced the volume of the instrument a little but he was not certain of that.
So my question would be would you actually end up with a better sounding mandocello by removing the existing transverse brace and installing X-braces. That is, would X-bracing really be better than the situation with two transverse braces?
However, as noted above probably no one is going to know the answer to that in advance -- unless someone has already tried it! (<:
I certainly appreciate the comments - - every bit of information helps!
I've X-braced several teens and 20's mandolins with sunken tops. So far, it has greatly benefitted both the tone, and the value of the instruments. A mandolin with a collapsing top has little collectible, or utilitarian value, so a well executed repair is your best hope. I'd want to see just how far it's sagging though, before I would recommend this. A lot of these do deflect a fair amount and can function fine this way for many years. What it does to the sound depends a lot on the size, placement, and angle of the X, as well as the original thickness of the top.
Thanks for the comment. I thought I had replied some time ago but maybe it did not upload.
Anyway, the sag on this mandocello is significant in that after several days at pitch it is more or less "flat" across the top like a dinner plate. But as noted if I release the tension it rebounds to essentially a smooth proper contoured top board in a day or two. It still sounds decent -- even as sagged as it is -- but I cannot hardly look at the sunken top without cringing.
One thing I had thought about trying before doing anything with the top was to convert the base of the bridge from a two point contact one to a full contact one by filling in the space with an ebony insert and then refitting the bridge to top. The original bridge on this mandocello is like an F-5 adjustable bridge -- only about double size. But this might help distribute the weight more evenly? Alternatively I could make a one-piece full contact bridge so as not to mess up the original one.
If I did take the back off -- a sobering thought -- I would have lots of options I suppose. For example I could put another transverse brace directly under the bridge? Or Frank Ford fixed a sagging Gibson mandolin by actually adding some additional thin plys of spruce to thicken the top. Or I could devise a set of X-braces.
Bernie, I can't see how changing the bridge will change a single thing in the sag department, but you probably already figured that out.
It seems to me that the only solution is to redo some bracing inside, and that will involve the back coming off. There are several folks here that will be able to knowledgeably talk you through this if you have not done it before. If it is your 1st time, I would suggest sending it to s real Luthier as there is virtually no chance of doing it so it will not show. My first one wasn't so much of a mess, but the missing lacquer from were I had to free the binding bothered me till the guitar was sold years later. After the back is off, you can make some decisions, as opposed to figuring that aspect out now. Getting the back off is the important thing.
I tend to think you are right about that. OTOH the there would be a larger surface for the bridge to contact the top and it seems intuitively that it might distribute the tension -- but then the total string tension will not change so yes I agree -- unlikely to help.
Also I think I have the same concerns about making a "mess" if I try to pull the back myself. I'd have no one but myself to blame....
I either have to fix this thing or sell it -- I can't stand seeing that top like that so it is just laying there with no strings. Right now all I have in the totally original instrument and its original red-line HSC is the $275 that I invested as a graduate student in 1973! (<:
Flat on top is not too unusual for a K1. As long as you have a good bridge and string height, I'd leave it alone. Once the bridge is all the way up and the strings are too low, then its time for surgery.
Thanks much for the perspective on this matter. I need to ponder it. Just for information, where in the USA is your shop and do you work on items shipped to you?
I am actually in Northern BC if you were talking to me. Bernie, I sent a friend request to you on here and a PM...