Martin Uke Repair: Depressed Fracture

[George Roberts]

I bought this uke years ago for $10 to 15 because of the extensive damage.  It has been in line, patiently awaiting repair.  The side cracks are both lengthy, but line up very well.  Hopefully they won't be too hard. 

The part that has made me shy away from this project is the "penetrating wound" with  a "depressed fracture" on the back.  Left to my own devices, I would secure a hard flat surface over the outside of the back, and then use a long burnisher on the inside, going with the grain and working from the ends toward the middle.

I would sure appreciate some help from others more experienced than I am.  I did look at Frank's repair of a uke with a similar crunch on the front, but I'm not sure how I could get a caul on either side of the back and get adequate pressure.

Thanks, George

[George Roberts]

Here's the bad part.

[Ned Knepp]

That's going to be a great uke, George. 

 It seems like I always say this but I would remove the back to make both repairs. There's just not that much room to work in aside of a ukulele. 

[George Roberts]

Thanks Ned.  It always seems more difficult to me to get the back off, and even worse, get it back on, than to find some alternate way to do the repair.  I may have to bite the bullet with this one, though.

George

[Paul Breen]

Pulling the back is an option if you can't get things pulled back where you want them. However, the side that's split in the image looks to be pretty well lined up already and should not be too difficult a glue up with hot hide glue. It could be clamped with no more than just masking tape. The back damage could possibly be clamped flat with magnets. I use 1" X 1/8" Neodymium magnets for clamping hard to reach spots like the squish in the back of your uke. Stacking the magnets increases clamping force. You could use 3 or 4 magnets, stacked both outside and in and likely flatten things out without pulling the back. Use hot hide glue for all repairs to this instrument.

[George Roberts]

Hey Paul,  I like the idea of the magnets, especially stacking them.  I have some that are hard to manage, but without any bracing in that area of the back, it is certainly worth trying.

Thanks, George

[Paul Breen]

Hi George,

Magnets have bailed me out of pulling a back more than once but you need to be very careful when using them. Clear the deck of anything that the magnets can attract. I use magic marker and put a plus or minus symbol on the magnets so there is no confusion if it will attract or repel. Lay them out away from one another but ready to go. I would use a palette knife or bit of steel rod as a means to first position the interior magnet through the sound hole where you want it. Then, with a firm grip, place the outside magnet. It's best to have the instrument clamped or held tight in a holding fixture while doing this!

[George Roberts]

Hi Paul, 

Thanks for the great tips.  I especially like the palette knife for placing the first magnet.  I have some small square magnets that I believe were rated at 18 lb attraction.  I'm not sure whether that means 18 lbs attraction to a piece of steel, or to another one of the magnets.  Hopefully it will be enough to flatten the dent.

[Paul Breen]

George,

If the little square magnets you mention don't cover side to side across the squish, you may want to get some with a bigger footprint. A 1" diameter is the smallest that I use and look about right, judging form your picture, for your project. I suppose it could be possible to double stick tape a gang of them onto a thin piece of plexiglass, you would need to experiment with that though.

[George Roberts]

Paul,

They are 1 inch square and about 3/16" thick.  I have to use a wooden wedge to get them apart.

[George Roberts]

Well, the agate burnisher didn't work.  Couldn't bring enough pressure to bear.  The magnets were very scary, but did work to flatten the depressed spot.  The splinters are not entirely back in their original location, but not bad.

I didn't think that I would have enough time to use the hot hide glue during the flattening process, so there isn't any glue in there at all.  My question is what should I do now?  Could I squeegee some hh glue in with my finger?  CA would probably wick into  all the little cracks.

I'm also assuming that this is a lacquer finish, and I have zero experience with lacquer.  Which glue would be most compatible with lacquer?

Again, many thanks for all the help, George

[George Roberts]

One more view

[Mark Pollock]

You could do the violin maker trick of using a suction cup to push the glue in to the cracks. I use an old Nerf dart.