Gibson Army Navy Reconstruction

[Tukanu]

I had so much fun restoring an Alrite, so I went out and bought a A/N that needed a lot of work.

The head, neck and fretboard are in great condition, although it will need new frets. The body, on the other hand, has exploded. Besides splitting, the back is heavily warped. The braces have all come loose...no surprise there. The radius of the braces is 8' to 10'. This was a surprise to see that much curvature. The treble side of the top came off after splitting, but the base side is mostly secure.

The top and back have shrunk, so the plan is to loosen the treble side from the tail block and remove about a 1/4 inch, reducing the diameter of the body so that the top and back will fit.

[Tukanu]

I wetted the pieces of the back and clamped them between two flat boards to try to get them to lay flat. The warping remained after removing them from the clamps. I decided to go ahead and glue up the three pieces of the back, and try to flatten out the warping later.

The fingerboard was the next project. The first few frets were badly worn, and the end frets had rusted. I removed all the frets and got some pretty bad chips. I was able to sand them out by rubbing the fingerboard on a strip of 80grit sandpaper attached to my bench top. I had to sand thru the pearl dots in the process. There is no problem replacing them with 1/4" dots. I will also have to re-cut the fret slots for the new frets. With most of the top and back removed, it will be easier to re-fret the fingerboard without worrying about damaging the top or back.


You can see in the photo that the top has shrunk and won't fit on the sides without modifying the sides a bit.


I'm waiting on some parts from StewMac. I ordered their tobacco spray lacquer stain hoping that it will match the neck color. I really don't want to touch the neck finish since it is original and in great condition.

[Tukanu]

I made a cut for removing a 1/4" from the treble side before freeing the side from the tail block. Using a hot artist's pallet knife, the side popped loose (photo #1). I re-attached the shortened side without a problem (photo #2). The top and back now have a little bit of overhang to work with due to the reduced diameter of the sides. Removing the 1/4" resulted in about a 1/16" overhang on both sides of the top and back.

Next step was to re-cut the fret slots. #2 and #3 were off by 1 mm, so I filled them with epoxy and made new slots. The new 1/4" pearl dots fit right in. I filled a couple of deep chips with super glue and ebony dust. I have happy to find out that the fret board is ebony, and not some dyed lesser wood (photo #3). In re-fretting, a couple new chips formed. They will be easily filled with ebony dust.

I will be working on re-building the top today.

[Russ Donahue]

Looking forward to seeing pictures of the next steps and your completed work!

[MikeEdgerton]

I'm impressed that you found two basket cases to buy

Nice work.

[Tukanu]

The first pic shows the gap that remains after positioning the pieces of the top. It is a wedge shaped gap open to the sound hole.


The next picture shows how much of the top has to be removed to close the gap.


The 3rd pic shows the top being carefully sanded to get the two pieces of the top to come together and close the gap.


The 4th pic shows the two pieces of the top being glued and pressed together. At this point the top is mostly detached from the sides which allows the top to be pressed.


This final pic shows the top being glued to the sides and also shows the patches for the repaired top.


The next project is to add the new braces to the top.

[Br1ck]

Following this with great interest.

[Tukanu]

All the top braces are in. I used the bracing pattern from Crystal Forest which seems to be a pretty reliable way to handle the structural issues of a flat top. I set the radius at 15' which is enough to give the top some arch without too much stress. Note the brackets running up the side that will prevent the braces from popping loose in the future.

I'm working on the back, and have managed to flatten out some of the nasty warping that has set in and caused the back to come loose from the body.

The bracing is not as massive as it looks in the photo. The main lateral brace is 5/16 X 5/8:

[peter.coombe]

Looks good. I also used those extra braces each side of the soundhole and a 15in arch on the Army Navy copy I made. Makes a lot of sense.

[Tukanu]

I have tried X bracing on a couple of flat top mandolins, but saw some slight defection under the bridge. So, I have been using this pattern ever since. I like the idea of support under the full width for the bridge. I use a 96" radius on the A/N Flat tops that I am currently making.

[peter.coombe]

I have been using X bracing on my other flat top mandolins, but they have carbon fibre reinforcement which I think is necessary with X bracing. So far have had no problems. These little Army Navy type mandolins can sound quite nice if you get them right, and the soundbox is so easy and quick to make. I am very impressed with the one I made and will be making more like it.

Here it is

[Tukanu]

Very good looking mandolin. You don't feel the sound hole needs any reinforcement? What do you think of the Brekke bridge? I have one but haven't tried it on a flat-top yet. I bought it for the Alrite that I restored, but I couldn't get it high enough.

[peter.coombe]

I like the Brekke, it is full contact so that spreads the load on the top. You are right in that the Brekke is a bit too short for restorations, although Vern should be able to make one that is higher. The Army Navy I had has a bridge height of 17mm which is too high for the Brekke. My mandolin has a 15mm bridge height which is near the top of the adjustment range of the Brekke. I am going to make a saddle 1mm higher with my saddle modification and see how that goes. I am also going to play around with different strings. Light strings only.

The sound hole is lined with a strip of Maple so I don't think it needs reinforcement. Next one won't be lined and I will see how it goes, but I don't think it is really necessary.

[pelone]

Question to the OP and Peter-----are you positioning the transverse brace directly under the bridge? Is this the common placement in
all Gibson mandos?

[Tukanu]

The two Gibsons I have worked on have the bridge directly over the brace. However the Alrite that I work on used lengthwise tone bars that completely failed. I have built 4 flat tops with the brace under the bridge. It seem contrary to the way a guitar is braced, where there is no heavy structure directly under the bridge. However, the tone and volume are good, and this seems to be the way a flat top responds the best. The plans that Crystal Forest sells show the bridge directly over the brace, and the Crystal Forest mandolins are very popular.

[peter.coombe]

Yep, directly under the bridge. The Army Navy I had was like that.

[Tukanu]

A side note about the Brekke Bridge. This is one of the most innovative products to hit the mandolin world in some time. What attracted me to this bridge is the style and cleverly hidden height adjustment.

Flat-tops just seem to look better with fixed bridges. The old Gibsons, Martins and Flatirons, and the modern Big Muddys and Red Valleys have a certain look and feel with the fixed bridge.

The Brekke Bridge has that same style, but offers adjustment by way of hidden set screws that raise and lower the saddle.

[Tukanu]

The back is complete and braced using the original lateral braces from the top and back. The braces have an original arch with a 10' radius. In trial fitting the back to the sides, I come up about an 1/8" short in the width. All that shrinkage thru the years and re-fitting the pieces back together have taken a toll. I will have to install edge binding to make up for the reduced size of the back. It will be invisible under the colored lacquer, and the back will be all the stronger for it.

[fatt-dad]

fun project! I've been curious about the Brekke - not that I have a current need. Thanks for posting!

f-d

[Tukanu]

The first pic shows the back glued in place and the 1/8" shortage in width.


The second pic shows the ledge for the edge binding with the opposite already glued in.

[peter.coombe]

So what wood is the back?

[Tukanu]

I have been trying to figure that out. It is very light colored and has a slightly open grain. If I had to guess, I would say a light colored cherry...but I really don't know.

[Tukanu]

Although it does look lite it in the photo, the tobacco brown from StewMac matched the original dark brown finish pretty well. It only took three light coats to get a nice dark even color to the body. Ready for about 10 light coats of satin lacquer.

[Tukanu]

So what wood is the back?

Peter Coombe - mandolins, mandolas and guitars
http://www.petercoombe.com

Update: Peter asked what wood was the back built with. I was at my local "Woodcraft" store and saw a piece of Birch that had a similar grain pattern to the back of this A/N. I was not familiar with birch, but I am sure the wood is the same as this A/N. Also, I was looking over the finish that I have been applying to the mandolin and notice the stain looks a little reddish. So I applied two more light coats of tobacco brown to darken the finish a bit. It seems to match better with this darker application.

[Tom Haywood]

My understanding is they were made of birch. But I haven't seen one up close.