The first few days of a new guitar's life

[Mark McLean]

Last weekend I strung up my latest build (my 3rd). It is a walnut SJ with Swiss spruce top - I will post some photos soon. I am interested in your observations about how a guitar should behave in its first few days. Let us assume that we are talking about a steel string acoustic.

When all of those individual bits of wood and their glue joints get put under sustained string tension they are going to take a little while to settle into a stable configuration - and then that 'stability' will gradually evolve over time anyway. How much do you normally expect the soundboard, neck angle and neck relief will move in the first days/weeks? Do you often find that you go back and adjust the neck angle (if it is a bolt-on)? If you are gluing the neck joint do you allow for anticipated movement?

With this and my other 2 guitars I did the initial setup as follows:
Bridge height about 9.5mm
Neck angle set so that a straightedge running across the top of the frets arrives just on the top of the bridge
Saddle moderately high (about 3.5 to 4mm above the bridge)
This means that if the straightedge runs from the nut slot (actually a zero fret on this instrument) to the saddle there is a clearance of about 3.5 mm at the 12th fret (low E string). This is a higher action than I eventually want the string to have but I expect to be taking the saddle down later.
The neck is bolt-on and I haven't glued the fingerboard extension yet; so it is easy to take the neck off and adjust the angle
Is this what you do, or would you set it up differently?

Then I strung it up (11-54 strings, to concert pitch). It sounds really good!! The action is 3.5mm on the low E at the 12th (high, but about what I expected). The bridge doesn't fly off, and the top doesn't implode - so far so good. A little bit of neck relief appears from the string tension but I adjust that (and love the Allied truss rod from the group buy). After about 48 hours there is a bit of movement in the top. I can now appreciate a very slight belly below the bridge, but it is not much. The straightedge now falls below the top of the bridge (by about 3mm) indicating a bit of rising of the top and rotation of the bridge. The string action at the 12th is now 4mm and the intonation is a bit off with that string height. After a further 3 days it has not got any worse.

Is this more than movement than normal? I am able to revise the neck angle and take a bit off the saddle and correct all of this fairly easily. But I don't want to do that if it is going to keep changing. If this is normal I will adjust my initial setup to anticipate early changes. I would love to hear your observations of newborn instruments to know what to expect.

cheers

Mark

[Puff]

Mark my take.

[Dave White]

Mark,

I think that most makers set the neck angle so that without string tension the straight edge is slightly above the top of the bridge rather than at the bridge height as the top will "dome" under string tension and as things settle - you will certainly see movement in the first few days but it may be a few weeks/months before it fully settles. Sounds like you have enough saddle height to do any adjustments but as you haven't glued the fingerboard extension down yet if it were me I would probably make a slight adjustment to the neck angle to give the action you are looking for with the string height above the brisdge that you want for your instrument. Alternatively set it so that with no string tension the straight edge is a little higher than the bridge. Belly behind the bridge is good in my view (all great sounding guitars have this) and what you need to watch for is any significant collapse in front of the bridge and around the soundhole. It's way too early to be contemplating something like a bridge doctor in my view.

[Steve]

Beautiful timing Mark - this has just happened to me too. Thanks to Puff & Dave for your responses - you've given me somewhere to go next.
Steve

[Mark McLean]

Thanks for the help guys. Over the last few days the guitar seems to be quite stable. The slight doming of the top is not excessive and it doesn't seem to be collapsing in front of the bridge. I am hoping that it is like Dave says - a sign of the soundboard responding nicely to string tension. Dave, you have confirmed my thoughts that I probably just set it up a bit too high in the action, and I can correct that. With my next one I will anticipate this a bit better.

Puff, your thought about a Bridge Doctor is a good one if it gets worse. I have actually been down this road before with my first guitar. On that one I made a fatal mistake with scalloping and thinned the X-brace between the X and the soundhole resulting in a weak top which deformed in a bad way. I thought I would need to take the top off that one and rebrace it, but a Bridge Doctor has actually saved that guitar. I find this part of guitar building the most challenging. I guess if I build the same type of guitar 4 or 5 times in a row I could get it right by trial and error. But each one I have done has been different (an OM, a L-00 and now a SJ) so the rules change a bit each time. Anyway - something new to learn each time. I'll get back to you in 20 years with all of the answers.

Hi Steve. I look forward to seeing and hearing more about your new creation.

cheers
Mark

[Puff]

You may need a secure connection with the other side to get back to me in 20 years' time
Things change at every turn; different woods, different designs..... the parameters are infinite.
An idea for the "Doctor" is to take the adjust function to the tail end.
This is my last post on this forum. Arohanui and Godspeed.

[Mark McLean]

Hi Puff
I am a bit worried about the finality of that last post. Everything OK? I sent you a PM last night. I hope we will see you posting here again today - or give me a call.
Mark

[Tom West]

Mark : I like to be about 1/16" over the bridge with the straight edge placed along the frets on a new guitar set up.The dimension from the top to bottom of strings is about 9/16".This is with a planned .500 from top to strings after settling in and any minor saddle adjustments in a few months time. I build with bolt on mortise and tenon necks.
Tom