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Pros and Cons of Gluing back or top first
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Author:  pjsch [ Tue Jul 06, 2010 10:24 pm ]
Post subject:  Pros and Cons of Gluing back or top first
It seems there are different ideas about which to glue to the sides first, top or back.

For those who have done it both ways, what are some of the advantages/disadvantages of gluing the top or back first?

A couple of pros/cons that come to mind are:

Gluing the top first gives access to the top braces to get a good fit when tucking the brace ends in the lining pocket. Whichever goes on second is more of a blind fit when assembling with limited access to inspect or rework the brace ends if the fit needs rework after gluing.

Gluing the back first makes it easier to do a better cleanup of the areas visible from the soundhole.

Any other advantages/disadvantages from those with experience in both methods of assembly?

Pat
Author:  Alan [ Wed Jul 07, 2010 6:31 am ]
Post subject:  Re: Pros and Cons of Gluing back or top first
I glue the back on first so I can make sure that any glue squeeze out is cleaned up and everything looks nice. It seems that one of the first thing people do is look throiugh the sound hole to check it out.

Others glue the top on first because that gives them access to the braces for fine tuning. It's much easier to do this with the back off than reaching through the sound hole.
Author:  Pat Hawley [ Wed Jul 07, 2010 8:04 am ]
Post subject:  Re: Pros and Cons of Gluing back or top first
"inspect or rework the brace ends if the fit needs rework after gluing"

Not sure how you could rework a tucked brace end after gluing. I fit both the top and back individually prior to gluing eithor. Then I glue the back first to allow for clean up of areas that could be seen through the sound hole.

Pat
Author:  woody b [ Wed Jul 07, 2010 9:20 am ]
Post subject:  Re: Pros and Cons of Gluing back or top first
Filippo Morelli wrote:
Alan wrote:
Others glue the top on first because that gives them access to the braces for fine tuning. It's much easier to do this with the back off than reaching through the sound hole.


You'll have to explain this one, Alan. What fine doing is being done with sides mounted to the top? Not sure I get it ...

Filippo



The tap tone of most tops is drastically different when it's glued to the rims instead of just held at one point. I've seen some people use .....boxed to firmly hold the plates for tuning.

It really isn't hard to clean glue squeeze out through the soundhole. This is especially true for areas that can be seen looking through the soundhole. I've seen some really nice guitars with soundports......but on some of them when you looked through the soundport the squeeze out from the top looked like a mess. It's hard to clean squeeze out through a soundport.

I glue my tops on first, after test fitting the top and back. Use whichever way works for you.
Author:  bluescreek [ Wed Jul 07, 2010 9:48 am ]
Post subject:  Re: Pros and Cons of Gluing back or top first
I only built 106 guitars so far and I use the back first method. This allows you to clean out any glue mess that can be seen through the sound hole. As for tuning the top .I don't do that till the strings are on. I don't think you can learn much on a top by tapping. I feel you get a better voice when you make adjustments to the top when it is a guitar.
Author:  Darryl Young [ Wed Jul 07, 2010 12:06 pm ]
Post subject:  Re: Pros and Cons of Gluing back or top first
I have vast experience......I've closed the box on one guitar! :lol:

With that said, I glued the back on first. Of course it was nice to clean the back as previously mentioned. Also, before glueing the top I noticed the back joint brace below the soundhole was slightly misaligned (wouldn't you know the one not perfectly aligned was in the most obvious location!). Anyhow, I planed it off and re-glued it. That would have been more difficult through the soundhole.

The main thing I liked about glueing the back first. The back is more arched than the top and the arch adds strength and stiffness to the back and may help maintain playability (action height) through humidity swings so I want to make sure I maintain that arch while glueing. I laid the back on the radius dish and placed the rims on top of it for glueing. This allowed me to place a couple of go-bars near the middle of the back to ensure the proper arch was maintained on the back while the glue was setting. The top arch is flatter so is a little easier to maintain.......and some folks build a completely flat top so even if you loose a tad bit of arch it likely isn't a significant change. I sprang my radiused top onto a flat rim on my OM build so I was changing the top radius anyhow (the top had a 1 1/2 deg taper above the sound hole).
Author:  Rick Davis [ Wed Jul 07, 2010 12:19 pm ]
Post subject:  Re: Pros and Cons of Gluing back or top first
I fit both top and back before gluing. Then I glue the top first, using my arched form to maintain geometry and provide support. The back goes into its arched form, the box (still in the mold) is placed on top, a simple cork-lined caul that follows the outline is placed on the top, and the whole shebang clamped.

Unlike some, I believe in clamping the blocks very solidly.

The caul allows easy access to the soundhole(s) and I can clean squeeze-out fairly easily using a small plane blade as a scraper. De-Glue-Goo finishes clean up later if I miss a spot.

Rick
Author:  Zach Ehley [ Wed Jul 07, 2010 12:42 pm ]
Post subject:  Re: Pros and Cons of Gluing back or top first
Back first here. The reason I started this is for glue cleanup, but as put a sound port on all mine, that doesn't make much of a difference anymore. You can see top and back through the sound port. I just kept doing it that way out of habit.
Author:  Alan [ Wed Jul 07, 2010 5:21 pm ]
Post subject:  Re: Pros and Cons of Gluing back or top first
Filippo...sorry that I didn't get back to you earlier. The day job keeps getting in the way of my forum ussage.

As Woody said, gluing the top on will change the tap tone, so some want to take the opportunity to fine tune the braces before gluing the back on. Of course, one could reach through the sound hole to sand more on the braces, but it's just easier before the back is glued on.

That being said, I don't do it that way. I glue the back first so that I can make sure everything looks nice for those sound hole peepers.
Author:  DennisK [ Wed Jul 07, 2010 9:46 pm ]
Post subject:  Re: Pros and Cons of Gluing back or top first
Filippo Morelli wrote:
No worries, Alan. I was just hoping someone would explain how tuning the top when the sides were on was somehow worthwhile. I know no one that does that, nor do I understand how shaping braces at that stage makes any sense. Was hoping for enlightenment but it seems to have been suggested with no forthcoming explanations ... ?

Filippo

As I understand it, the idea is that it gives you a closer sound to the final box than holding up the free plate and tapping it, while still giving you easy access to the braces for shaving. Makes a lot of sense to me, being able to hear the tap without damping any part of the plate to hold it up. Might even get some of the air chamber resonance too, with it sitting on a hard table.

On the other hand, free plate tuning gives you more access for flexing the plate to feel the stiffness. I suppose I'll try both as soon as I get all my braces glued on. Tune the free plate, then glue the sides and tune some more :)

And I'll be gluing the top first in the Cumpiano book mould-less construction style. I suppose the sides-on tap tuning style would work better with a mould to hold the sides more steady though.
Author:  Alan [ Thu Jul 08, 2010 6:57 am ]
Post subject:  Re: Pros and Cons of Gluing back or top first
Filippo Morelli wrote:
No worries, Alan. I was just hoping someone would explain how tuning the top when the sides were on was somehow worthwhile. I know no one that does that, nor do I understand how shaping braces at that stage makes any sense. Was hoping for enlightenment but it seems to have been suggested with no forthcoming explanations ... ?

Filippo



I suppose that you're right Filippo, it doesn't make sense. When one gets a few years on them the memory begins to fade and I'm probably just confused. I'm sorry. Please ignore my response to the person that posted the question.
Author:  Tom West [ Thu Jul 08, 2010 9:39 am ]
Post subject:  Re: Pros and Cons of Gluing back or top first
Filippo: In ref: to who tunes bracing after gluing just the top on, Dana Bourgeois did at one time, Ervin Somogyi does it I think,and I try to do it. To me I try to get the most out of the top that I can before gluing it on the sides,the same in the top glued on stage and then again once the box is all glued together. I just see it as a progressive process that seems quite logical. I think everyone has to use what works for them.
Tom
Author:  Brock Poling [ Thu Jul 08, 2010 2:31 pm ]
Post subject:  Re: Pros and Cons of Gluing back or top first
Filippo Morelli wrote:
No worries, Alan. I was just hoping someone would explain how tuning the top when the sides were on was somehow worthwhile. I know no one that does that, nor do I understand how shaping braces at that stage makes any sense. Was hoping for enlightenment but it seems to have been suggested with no forthcoming explanations ... ?

Filippo


Somogyi does it that way (not new news now that I read the thread clear to the bottom :-$). Glues the braced top to the rim then voices it. It is just the way he does it.

I have build a hybrid type model where I clamp the top into a tapping mold (similar to what he shows in his example videos) to voice the top. Then glue the back on first to control the clean up. It seems to work pretty well.
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