MIMF

Any takers?
This mandolin is owned by me. As far as I can tell it was built in 1923 and is an A-Jr. It is playable. I did a not so successful top crack repair about six years ago and put a LOT of lacquer on it to hide the repair. The top has cracked again in another place. I'm not proud of what I did but the instrument still has potential. The tone bars have both given way and there is now a significant bent depression under the bridge which is not likely to be able to be repaired and this is probably what caused the initial crack and the one that I have now. I want to replace the entire top. The job of carving a new top will be done by me but I want to have some sort of oversight in disassembling the instrument and want the original top off to study it before I carve the new one. I haven't found anything in the archive. I think that I'm up to the task and I want to avoid as many of those things that you only learn by making mistakes and just doing unnecessary stupid things. I'm not finding much technical info on these instruments. I'll post a picture tomorrow.

That's fixable! If you want to carve then make a new mandolin!

Mark W, It's hard to tell without pictures but it sounds like your Mando has this problem: http://www.frets.com/FretsPages/Blogs/K ... lapse.html. Rather than replacing the top (why does "it seemed like a good idea at the time" come to mind), perhaps Frank Ford's approach would be better.

Joshua

Mark, I anticipated your reaction and I may take your advice in full. Joshua, ABSOLUTELY! The photo essay illustrates exactly what needs to be done however the existing top has much more of a severe depression caused by the downward presure of the bridge and is on both sides. If you took Mr Ford's mandolin and put it in the back window of an old sedan and left it sitting there tuned up to pitch for a couple summers in Mississippi, you'd have my mandolin. With the back off of the instrument, there may be a slight chance for recovery using the illustrated photo essay aproach and I will give it a go. For this instrument, I have nothing but time on my hands. I'll repost again when I have the back off of the instrument. The back has a good fit and has not shrunk like others that I have seen. I'll do a few tiny alignment holes around the perimeter and pull the back off this week. The last time I worked this instrument there was a comment made that these tops are very thin. I may need suggestions for alternative bracing methods but we'll discuss that when I get there.

Thank you both,
Mark W... aka wrnchbndr

I've repaired some pretty warped soundboards with the replacement of bracing. Take the old braces off, then use heat, moisture and clamping pressure to slowly coax the plate back where it should be. Let dry, then add new braces. Its worth a try.

I've reshaped several old Gibson mandolin tops, some removed from the instrument and "sandbagged" in a plaster form, the most recent one reshaped still on the rim using a Watlow heater and "ingenuity". I've added splines and various braces and reinforcements to maintain the shape (hopefully).
Adding an X-brace is a good way to maintain the shape of the top, but only if it is removed from the rim. Adding an extra transverse brace is effective and can be done working through the sound hole.
There are some Gibson tops that are so thin they are hard to salvage, but they are usually much earlier than the 20s. "Snake head" mandolins are in demand these days, and that indicates that saving the top is probably a better way to preserve value even if a re-top would lead to a more sound instrument.