Setup "in-the white"

[Alastair]

Hi all,

On a classical, what are the thoughts on doing a temporary bridge glue-up, using white pva, to confirm setup etc, and then marking bridge position, heating and removing, before doing the FP finish, rather than the 'traditional' of fp with the bridge in place?

My reasons are 3-fold:

To allow easy remediation of any marking during the bridge positioning
To allow an assessment of the final action under tension, (and allow fixing, before the finish goes on)
To simplify FP, by having a clear soundboard, and doing the bridge seperately.

And also a fourth, I'm dying to find out what it will sound like.

Any drawbacks I don't know about?

[kiwigeo]

I generally FP the top first and then scrape back FP to glue on bridge. My main reason.....FPing around a bridge is a P in the A.

[Alastair]

Hi Martin,

+1 for that.

Any negatives to fitting bridge, and then removing for finishing?

[jeffhigh]

I position and fit my bridge to the top fairly early, before final sanding. I drill holes through the saddle slot and use plastic pins to locate it. It goes on and off as needed but obviously not with string tension.
I then finish the top, install the bridge with the locator pins, scribe around, scrape off the finish and glue.
This way it always goes back in the same position.

The downside with gluing on with pva then removing is contamination of the joint with the pva and possible damage when removing.

[auscab]

Hi Alastair,

In the furniture game, wood turning , carving, if I need to glue and then release later, a single sheet of news paper in the glue join makes for a perfect release,

It's how wood turners get two perfect halves to a column .

Would it stand up to string tension ? My guess would be 50 /50

Wouldn't it be a great tool though , if we had access to a strong glue with an easy release method ,

I think HHG is easier to release later than PVA .

Just my 2 cents worth from the woodwork furniture side

[kiwigeo]

Hi Martin,

+1 for that.

Any negatives to fitting bridge, and then removing for finishing?

If you mean gluing the bridge on and then removing it........there's a good chance damage to top will result from bridge removal process.

On a classical the compensation is generally a bulk value applied to the saddle as a whole.....considering the hastle involved I cant see justification for gluing on a bridge to check location is correct and then removing it to finish the top. Double check your measurements for bridge location, check you've got correct amount of compensation at saddle and then mark top accordingly.

I guess its really a matter of personal choice but Ive tried finishing with and without the bridge on and I prefer finishing with the bridge off.

[Alastair]

Hi Martin,

Basically the idea comes from the Cumpiano book. He routinely does this for the acoustic; glues on the bridge using pva on the tailbock half, then heats and removes after setup, and does the finishng, then scrapes the bridge area clear and glues on the bridge permanently. Doesn't mention it for the classical, tho'...

Rob,

Ive done that regularly woodturning, both as a chucking meyhod when I first started, and also for split turnings.. Might be an alternative, if strong enough.

Still not sure though.

[jeffhigh]

A classical is a bit different. All the tension of the strings is taken by the glue joint rather than being anchored by the ball ends under the bridgeplate.
Whilst a pinned bridge actually needs very little strength in the glue joint a classical relies totally on the glue and sudden and catastrophic failure can occur with the loose bridge and string tension causing damage to the guitar top

[simso]

I would discourage you gluing and then trying to release, the potential for burning the top when heating or having tear out when attempting to seperate, is too high.

[Alastair]

Thanks guys,

From the weight of evidence and logic, all statements to the effect that this idea is still a going concern are now inoperative..........

[kiwigeo]

Thanks guys,

From the weight of evidence and logic, all statements to the effect that this idea is still a going concern are now inoperative..........

That would be a fair assessment of the situation

I actually glued on a classical bridge once...got halfway through FPing the top and then decided to lift the bridge and finish the FPing with the bridge off. The guitar still has a visible top gouge at one end of the bridge where the pallete knife slipped.