Thank you Vesa!vesa wrote: ↑Sun Mar 04, 2018 7:00 amHi Olivier
You cannot force it to anything, humidity chages will do the job - not physical force.
It may come back to the original shape if you return to humidity % where it was made and let the time do the trick (it can take days or weeks) in that case it should remain in the position (fastened in the solera?) it was when all this happened to get stabilized.
Other possibility is that you try to fiddle with different humidity levels.
Keep it simple as it is: if drier wood shrinks - if more humid it expands. Keep the other side covered and expose only one side to the humidity change. If concave it will need higher humidity, if convex it will need lower humidity to return to the original shape.
Everything happens with a delay, so if you have overdone it, turn the top upside down to even it.
It is possible, but do not rush - let the water do the job.
Hi Simon,simonm wrote: ↑Sun Mar 04, 2018 11:16 amThe second picture looks pretty good. The first picture would make me nervous but I may be missing something. If for some reason I have to leave a braced top for a couple of days before I close the box, I leave it on the solera with a jig pressing the top into the solera. You could leave it in the go-bar system for storage too - would need very little pressure just for storage. When I am building I aim to get the box closed up within two days. If I know I won't be able to do that, I don't brace the top or back. It doesn't stop me preparing everything or doing other stuff, but when it comes to bracing the top and back and closing the box I like a clear run at it when I have suitable humidity conditions.
Hi James,James Frieson wrote: ↑Sun Mar 04, 2018 12:25 pmIf your top has gone concave all by itself due to experiencing of atmospheric relative humidity , it has been predetermined to do so , by the moisture condition of the wood at the time it was braced . There is no fix for this , with the exception of removing the bracing and rebracing it again under ideal conditions for doing so .
Hi Micheal,Michael.N. wrote: ↑Sun Mar 04, 2018 1:03 pmI don't think it's far from what it should be, going by the second picture. It may well be a combination of a slight dip (from the centre joint) and the edges of the lower bout curling up a touch. I'd give it a few more days in the solera with the go bars. You could also lock the shape in by placing heavy weights across the bridge patch when assembling sides and gluing on the back - you just need to be able to get the weights out through the soundhole. This might seem a little radical but Hauser supposedly forced his dome by gluing the soundboard to the curved bridge.
I had many shops , and in most of them I had no way to control the RH % . I just waited for dry weather . I have had many tops and backs go flat or concave . But for a long time I work in a shop where I have a small sealed room with a dehumidifier in it . I can control the humidity and know what it is at the time of assembly . Tops braced in that room at usually between 30 and 40%RH , I can leave for a year hanging around in my shop and then go back to them later ; they never collapse . The likelyhood that the top in question , that you are concerned with , will encounter again in its life , a period of dryness , and thus be affected by it , is large ; attempting to "fix " the top with humidity cannot eliminate that likelyhood . It is an easy matter to remove the bracing and rebrace it , and then you can have confidence in it .Olivier77 wrote: ↑Sun Mar 04, 2018 6:05 pmHi James,James Frieson wrote: ↑Sun Mar 04, 2018 12:25 pmIf your top has gone concave all by itself due to experiencing of atmospheric relative humidity , it has been predetermined to do so , by the moisture condition of the wood at the time it was braced . There is no fix for this , with the exception of removing the bracing and rebracing it again under ideal conditions for doing so .
I have to say the top was really good when I braced it and for a while after. This is my first guitar and I do this in my free time, so it does take me quite a while to get from one step to the other. It was only when the humidity dropped that the top shrank...and it seems that putting it back at normal humidity level does bring it back to normal as well, or close to.
Thanks for your reply.