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Restoration of a write-off archtop

If you have a string instrument of any kind that needs fixing, a mistake you made in building a new instrument that you need to "disappear," or a question about the ethics of altering an older instrument, ask here. Please note that it will be much easier for us to help you decide on the best repair method if you post some pictures of the problem.

Restoration of a write-off archtop

Postby Nathan Dodd » Wed Jul 26, 2017 9:19 pm

I've been looking around the site for some time and used to be a much more active member. Life and funds have always made my building experience a slow one.

While on holiday last week I decided to invest in a 'project' guitar. I found a 1961 Hofner Congress in very bad shape. I paid a little more than I wanted to for it and had expectations that many things would require repair and renewal on the guitar. It had a broken neck at the heel. Someone had added a Japanese pickup in the late 60s early 70s and the whole thing was held together by sheer willpower. Perfect - it provides an opportunity to cut my teeth on a lot of repair jobs I have always wanted to become accustomed to.

For those who may not know, the congress is an all laminate, bottom of the range fully acoustic archtop affair in its original form. I suspected that it would be parallel braced and i was correct. When the pickup was installed they cut through the top and straight through both braces!

I have already stripped the guitar and removed the top. I added a maple filler piece to the pickup aperture and replaced the braces. It was at the point of sanding the maple filler piece that I realised that I had made a rookie mistake - I hadn't thought to run a straight edge up the length of the top. Upon sanding I became aware that the pressure of the strings over the last 40 odd years and the compromised integrity had caused the arch to collapse below the pickup hole and the top described a double arch with a dip at the waste some 2.5mm at its deepest.

The intention was always to refinish the guitar as a 'black top' to hide many other minor scars to the top.

What would you do at this point? Would you backtrack, remove the new braces and patch and make an effort to reintroduce the original arch by creating stressed glue joints and new braces that compensate? Would you continue with the top in its existing shape? Could you think of an alternative? I would imagine that adding material (even spruce) as a splice over the area and sanding the original curve back into it would dampen the responsivness of the top and as such would be a no-go.

As it stands, patch in place and braces shaped with the indentation present the top is actually very responsive for a piece of laminate and taps a nice clear and loud tone.

For further interest the guitar will be receiving new binding front and back and to the neck (currently no binding on the back and neck), corrected back bow to neck, repair of broken heel, from 10 to a 12 inch radius on the fret board, full refret, new hardware throughout, full refinish along with the repair of all indentations, small cracks and various holes and gouges that have been drilled and cut into it over the years. It really was a shambles! Down the line it may also receive a floating pickup off the fingerboard (which also has to be replaced)
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Re: Restoration of a write-off archtop

Postby Beate Ritzert » Thu Jul 27, 2017 5:01 am

Nathan Dodd wrote:The intention was always to refinish the guitar as a 'black top' to hide many other minor scars to the top.

In a similar case i decided to make a filler in the shape of a "pseudo pickup" and leave the original color intact.

See this thread as an inspiration: viewtopic.php?f=8&t=1652#p15182

It actually covers the restauration of two guitars (Isanas). In the 2nd case i tried to push a sunken top out by heat and tension. But You really have to shape the wood. Just forcing it into shape by bars might lead to failure in the long run.

What would you do at this point? Would you backtrack, remove the new braces and patch and make an effort to reintroduce the original arch by creating stressed glue joints and new braces that compensate? Would you continue with the top in its existing shape?


As i do not have a picture of the top my answer can only be "probably".

Something else: the pickup hole will always be a weak point in the top, especially if it is close to the neck where the direction of the arc changes in a complicate manner so that the filling s not able to carry the forces.

So the braces need to be strong (=high, 3-4 cm) in this area in order to be able to carry the load all by themselves. This immediately will lead You to scallopped braces which are high only where they statically need to be and low everywhere else.

I should note that the 1st of the two guitars is still a bit weak; it looks as if i'll need to reinforce it a bit more.

Please let me also notice that the responsiveness of both guitars improved drastically after the repairs.

For further interest the guitar will be receiving new binding front and back and to the neck (currently no binding on the back and neck), corrected back bow to neck, repair of broken heel, from 10 to a 12 inch radius on the fret board, full refret, new hardware throughout, full refinish along with the repair of all indentations, small cracks and various holes and gouges that have been drilled and cut into it over the years. It really was a shambles! Down the line it may also receive a floating pickup off the fingerboard (which also has to be replaced)

My idea of doing such stuff is quite different: leave as much as possible of the old structure and look intact. The fingerboard can usually be used after refretting, and the finish will look a lot better after merely polishing it up with micro mesh (well, on the 1st Isana i filled some of the holes, tried to match the color with stain and covered this with NC lacquer).

Every old instrument has its history. And these marks display that and contribute to its character. So why hide them?
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Re: Restoration of a write-off archtop

Postby Nathan Dodd » Thu Jul 27, 2017 7:21 am

Hi Beate,

Thank you for the reply and the link; it appears that we have had a similar idea and similar experiences.

The previous work carried out to my Congress was very poorly executed and unfortunately the aperture for the pickup is quite unsightly and there is also scoring around the bridge area that appears to have been done with a stanley knife. the finish to the guitar is also severely crackled and chips off easily. as such I believe the best cosmetic option to be to finish in a block colour. luckily i happen to really like the look of black face archtops.

I have installed braces in line with the dimensions mentioned in the Benedetto book and left them fat and rounded. I am hoping that they will provide enough stiffness. they are very stiff to thumb pressure.

This was the state of the original top:
P7221973.jpg

P7221976.jpg


Now with patch and replacement braces shaped and in place (Please forgive the scorching from the previous brace removal process :? ):
IMG-20170726-WA0003.jpg


And this is re resulting curvature of the top:
20170727_114439.jpg


in a way, as the dip is inline with the waste of the arch top, it doesn't look entirely out of place if not somewhat unusual. i would imagine that filling this section and reshaping it would dampen the responsiveness. possibly leaving it like this would be the best option for the responsiveness of the top but i'm not sure. i'm sort of considering it but am afraid to adversely effect the volume and tone producing quality of the soundboard.
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Re: Restoration of a write-off archtop

Postby Brian Evans » Thu Jul 27, 2017 7:43 am

If you've stabilized the top with the new braces, I would leave it as is. I have a similar Hofner Senator, they are actually pretty good guitars, loud and brash. Watch for the neck mortise, it is a plain mortise, not dovetailed, and is prone to slipping and needing a reset. Mine was done 25 years ago is and is still in great shape. I put a Johnny Smith pickup on mine for a while, and it was an astoundingly good sounding electric jazz guitar.
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Re: Restoration of a write-off archtop

Postby Nathan Dodd » Thu Jul 27, 2017 7:56 am

Thanks Brian,

Your reponse gives me confidence. i fell in love with a friend's Congress many years ago and have always wanted one. i know what you mean about loud and brash. i may add a floating pickup to this guitar in the future if i like the way it turns out maybe a Benedetto S-6 or something. I envy you for your Senior :)

Yes the heel has indeed slipped on this guitar as well as a clean break in the heel about 1.5-2cm down from the base of the fingerboard. when i got the guitar home the neck popped right off but the remainder of the heel remains in it's shifted position:

P7221941.jpg


P7221963.jpg


P7221965.jpg


I intend on injection steaming the remaining part of the heel out to rebuild the neck and reset the joint. fortuitously, due to the break and as it is below the line of the top, i envisage that this process is going to be easier and less invasive. did you steam yours out? is there an alternative method?
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Re: Restoration of a write-off archtop

Postby Barry Daniels » Thu Jul 27, 2017 11:27 am

I am a contrarian. Planing off braces and replacing them is really quite quick and easy. Leaving a dip in the top like that will throw a lot of things off. Repair it now while the top is off. You will be glad that you did in the long run. One of the first things to learn in guitar making is to not be afraid to re-do things if they don't work the first time. That is the best way to learn.
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Re: Restoration of a write-off archtop

Postby Bill Raymond » Thu Jul 27, 2017 12:02 pm

I agree with Barry. You will probably be happier in the long run if you get this as right as you can from the very start.
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Re: Restoration of a write-off archtop

Postby Nathan Dodd » Thu Jul 27, 2017 12:36 pm

Thanks for the input guys, I must admit it has been bothering me that this dip is presentbajd I'm worried that it will be incredibly evident when I apply the finish.

If I did take it apart and redo the top my idea presently is to make a tall filler block in spruce this time then make a form for either side of that block describing the correct arch. I would then weigh down the sides of the top to allow the effected area to take shape over the form and glue it to the filler piece to keep it in place. I would then re-brace to add strength to the new shape. Any stresses should even out in time. Would you agree with this action?
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Re: Restoration of a write-off archtop

Postby Brian Evans » Thu Jul 27, 2017 1:15 pm

What is a good strategy for the repair? The top is 4 ply (three thick layers and a thin maple face layer). I am uneasy about using heat or moisture to slip the glue in the layers so the plywood can change shape, and plywood that thick (mine is .143" thick) is hella stiff. If it was solid wood, I would heat it, move it and re-brace it (Frank Ford has a description) but plywood I would be afraid of permanently de-laminating it. I don't think I would permanently glue a block inside, but using a caul and clamp may well persuade the dip out. If you do remove your new braces, just plane them off, don't use heat to try to release the glue. No more scorch marks! Heat and moisture are the enemies of plywood!
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Re: Restoration of a write-off archtop

Postby Nathan Dodd » Thu Jul 27, 2017 1:25 pm

Yes the block I'm thinking if would not be fixed but would come off once the glue joint with the filler is set. I would then reintroduce braces back to provide the support. It may be that I would use maple again for it's added rigidity as opposed to spruce
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Re: Restoration of a write-off archtop

Postby Nathan Dodd » Thu Jul 27, 2017 2:54 pm

earlier i removed my braces once again and a thought occurred to me. i took my razor saw and cut away the glue joint on the back edge of my patch (closest to the bridge) found a small block and placed it under the collapsed section. with some pressure to the top i found that the fallen area would raise above the original patch and reinstate the curve! i realised that i may have been planning to over engineer. i have now formed a second filler patch to go over the original one which i have weighted and glued to the edge top of the first and to the now raised edge of the soundboard, put a small piece of veneer and some more glue back on the edge of the original patch once dried i will re-shape the underside and reduce the second filler so that i can use it to follow the original arch. the result will be that the patch is made from 2 pieces of wood (not forgetting this is a laminated top anyway) but they will be carved above and below to follow the width of the rest of the soundboard meaning that there should be no loss as a result.

20170727_191903.jpg


The result may mean that 2 perfectly good braces had to be sacrificed but I believe that the end will outweigh the means and I must thank Bill and Barry for the words of wisdom - if i had lived with it, i may have been living with it for a very long time, and the application proved invaluable in practice.

Once the joint is dried i will start work on shaping, then bracing and will post up a picture of the result. Everything crossed that it comes out properly at the other end. If anyone is interested i will continue to post up pictures of my progress on this project up to completion.
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Re: Restoration of a write-off archtop

Postby Karl Wicklund » Thu Jul 27, 2017 8:44 pm

Thanks for sharing this with us. I find these deep repairs, salvage jobs even, fascinating.
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Re: Restoration of a write-off archtop

Postby Nathan Dodd » Fri Jul 28, 2017 5:39 pm

Thanks Karl - frustrating is another adjective that might be pertinent :lol:

Nevertheless, this evening the weights came off and the story is one of success! the arch has remained in place. while the curve isn't completely faultless it is within fractions of a millimetre which makes me a lot happier. i think the difference will come out with some final sanding now. thanks everyone for the help and support!

I have not reduced the underside yet as it's a little late in the evening for brace fabrication and i want to leave the filler as rigid as i can until i'm ready to add the braces but the hope is that this weekend I will shape the underside, create said braces and glue them in place.

20170728_215249.jpg

20170728_215300.jpg


You can see here where the upper filler has taken the shape of the new arch
20170728_215517.jpg


Finally, i will purchase a steamer and a basketball needle and steam out the remaining part of the heel so that the neck can be rebuilt and the top reattached.

After that, binding will be added to the fingerboard and body (front and back) and sanding will begin for the refinish.

At some point I will fabricate a replacement pickguard and install the replacement hardware. I intend on having a trapeze tailpiece, a Gotoh TOM bridge (because I am left handed and can't for the life of me source a left handed all rosewood bridge or even a blank in the UK) and some Schaller Grand Tune open backed tuners.
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Re: Restoration of a write-off archtop

Postby Barry Daniels » Fri Jul 28, 2017 6:08 pm

Looks much better. Definitely worth the extra work.
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Re: Restoration of a write-off archtop

Postby Nathan Dodd » Fri Jul 28, 2017 6:34 pm

Thanks Barry, I agree
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Re: Restoration of a write-off archtop

Postby Beate Ritzert » Sat Jul 29, 2017 8:31 am

[quote="Brian Evans"... but plywood I would be afraid of permanently de-laminating it. ... Heat and moisture are the enemies of plywood![/quote]

But plywood is formed under heat and moisture and pressure, and if You apply that correctly it will be fine. Like it was with my guitar. But You always need good bracing to take the load. As (really) strong braces have a negative impact on the tone, i did the fanned bracing - and that's an approach i would do once again.
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Re: Restoration of a write-off archtop

Postby Beate Ritzert » Sat Jul 29, 2017 9:10 am

Back to the guitar: really nice job until now.
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Re: Restoration of a write-off archtop

Postby Nathan Dodd » Sat Jul 29, 2017 4:58 pm

Thanks Beate, I will continue to post pictures of my progress
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Re: Restoration of a write-off archtop

Postby Nathan Dodd » Sat Jul 29, 2017 5:30 pm

Beate Ritzert wrote: i did the fanned bracing - and that's an approach i would do once again.


I found that a very eloquent solution and enjoyed reading about it in the link you provided
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Re: Restoration of a write-off archtop

Postby Nathan Dodd » Sat Aug 12, 2017 5:49 pm

The Story so far:

As mentioned above, I found the battered old Hofner on eBay one day while on holiday and thought that she could serve well as a practice piece in order to hone some restoration skills. little did I know what i was letting myself in for!

P7221936.jpg
P7221938.jpg


initially i could tell from the advert that there was a pickup mounted in the soundboard and that the pick guard was not original. only 5 of the original machine heads remained and one of those had a new knob attached at some point in the guitar's history. The advert clearly showed that the neck and snapped clean off the heal.

P7221939 (1).jpg


Upon receiving the guitar and giving it the initial once over and stripping it down I discovered that there were many areas of concern from a back bowed neck, cut bass bars (as discussed at length above) as well as a crack at the bottom of one of the f-holes potentially from some kind of impact in the guitar's past. it was also evident that the bridge had been ruined and the metal threaded bars were protruding from under the feet of the bridge base and had been happily marking the top in that area through use and time. the bridge does not sit flush against the body of the guitar. There were also score marks in the surface of the soundboard from some questionable period in the guitars past where it might at some point have had a different bridge. either that or some kind of tape may have been attached under the bridge in a futile attempt to prevent further damage from the damaged bridge base.

P7221959 (1).jpg
P7221951.jpg
Last edited by Nathan Dodd on Sat Aug 12, 2017 6:14 pm, edited 1 time in total.
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