Gluing top and backs while in mold using go bars?

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patrickb
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Gluing top and backs while in mold using go bars?

Post by patrickb »

I researching and trying to learn as much as possible ahead of my first kit build which will be a Martin style 14 fret dreadnought.

I'm liking the idea of using the BluesCreekGuitars.com mold and keeping it on as much as possible so my question is about leaving the mold on and gluing the top and back using go bars while the sides stay in the mold. Does John have a video of this technique? In this video Kit Build - Glueing Top and Back Using Halo Patterns John removes from the mold and uses clamps but in the YouTube comments he says he will sometimes leave it in the mold and use go bars. I would love to see this on video.

Thanks!
tippie53
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Re: Gluing top and backs while in mold using go bars?

Post by tippie53 »

John Hall
Blues Creek Guitars Inc
Authorized CF Martin Repair Center
president of Association of Stringed Instrument Artisans
http://www.bluescreekguitars.com
patrickb
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Joined: Sat Nov 25, 2017 9:26 pm

Re: Gluing top and backs while in mold using go bars?

Post by patrickb »

Awesome, thanks!

I couldn't tell in the video but was the back already on? If on, was it glued and dried or glued and not dried or merely in place but not glued at all?

Could you do both back and top at the same time like this?
tippie53
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Re: Gluing top and backs while in mold using go bars?

Post by tippie53 »

I do the back first then the top so this is just the same process repeated
jh
John Hall
Blues Creek Guitars Inc
Authorized CF Martin Repair Center
president of Association of Stringed Instrument Artisans
http://www.bluescreekguitars.com
nkwak
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Location: Pittsburgh PA suburbs

Re: Gluing top and backs while in mold using go bars?

Post by nkwak »

I'm bumping this because I'm working hard to get to this point on my second build and the plates are not cooperating. Is there a specific height or length of gobar that is ideal to apply adequate pressure for a plate that doesn't want to follow the arch along the length of the body? I've measured and notched and sanded and planed and frequently dry fit the plates with a light source inside the body to check for good contact and still the plates want to flex under the gobars. What am I doing wrong?

FYI: my I recently modified my gobar deck to be adjustable with a minimum height of 24". It's presently set at 32" high and my nylon gobars are 28." I'm building a medium jumbo so the body is around 4-3/4" deep.

For my first build I actually used wooden bars that didn't have as much flex. Unfortunately, when one failed it was like a spear flying. I had that happen and don't want to deal with the fallout from THAT again. Fortunately, I was lucky that I was able to just have to repair a brace through the soundhole. I've actually had worse mishaps but I don't want to tempt fate; my luck has been good so far.

Should I just drop the height on my gobar deck?
~ Neil
tippie53
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Re: Gluing top and backs while in mold using go bars?

Post by tippie53 »

what I use is about 1/2 in more than the open length so I have about a 10 lb force
1/2 in dowels work if your only doing a few a year
also if you have a table saw rip oak or hickory about 3/16 to 1/4 thick and 3/4 wide
John Hall
Blues Creek Guitars Inc
Authorized CF Martin Repair Center
president of Association of Stringed Instrument Artisans
http://www.bluescreekguitars.com
nkwak
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Joined: Sat Nov 13, 2010 9:55 pm
Location: Pittsburgh PA suburbs

Re: Gluing top and backs while in mold using go bars?

Post by nkwak »

Thx John. FWIW I'm using the nylon rods from the wire running kit sold at Harbor Freight. I cut off the male ends and use wooden blocks as cauls for groups of 2-3 gobars. I also used LMI's brace radiusing jig to contour the underside of the braces. I don't use a radius dish; I'm relying on the radius of the braces to determine the geometry.
~ Neil
Kbore
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Re: Gluing top and backs while in mold using go bars?

Post by Kbore »

nkwak wrote:.... Is there a specific height or length of gobar that is ideal to apply adequate pressure for a plate that doesn't want to follow the arch along the length of the body??
You might consider clamping the plate with spool clamps or other to tame your unruly plates. After the clamps are applied I've seen videos where builders also wrap the body with cotton twill tape before the glue dries.

Does the length of the bar affect the pressure the bar exerts or is it the thickness/ spine of the go-bar?
Measure Twice,

Karl B
nkwak
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Re: Gluing top and backs while in mold using go bars?

Post by nkwak »

Kbore wrote:
nkwak wrote:.... Is there a specific height or length of gobar that is ideal to apply adequate pressure for a plate that doesn't want to follow the arch along the length of the body??
You might consider clamping the plate with spool clamps or other to tame your unruly plates. After the clamps are applied I've seen videos where builders also wrap the body with cotton twill tape before the glue dries.

Does the length of the bar affect the pressure the bar exerts or is it the thickness/ spine of the go-bar?
That’s a good idea, but my mold isn’t designed to accommodate spool clamps. The back fits on with less clamping pressure than the top. I’m thinking that I can glue the back on first so that the waist is at least semi stable so that the mold isn’t necessary and then make some spool clamps to lock the top in.

The alternative is to make a fail to fit over the plate that I can screw down into the mold with like in Johnathan Kinkead’s book.
~ Neil
tippie53
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Re: Gluing top and backs while in mold using go bars?

Post by tippie53 »

it you have to force the plates you may not have your geometry right on the bottom.
It shouldn't take that much to close the box. there may be some light that will show at the joints of the kerfed lining
I just use the gobars and it really doesn't take a lot of pressure.
John Hall
Blues Creek Guitars Inc
Authorized CF Martin Repair Center
president of Association of Stringed Instrument Artisans
http://www.bluescreekguitars.com
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