Plate problem

[nnickusa]

So, I'm starting on another, while waiting for the dread to cure.

I'm very carefully following all the advice I've received regarding RH, and my Poor Man's Dry Room is holding nicely between 40-45%....

I made the braces, joined and thicknessed the back, and put everything in the box for a week. It was pretty dry around here up til then. Yesterday morning it was fine. This morning, I thought it looked a bit odd, and find out that the radius has reversed itself. That is, it's concave relative to the guitar body, and not convex as I planned.

I'm guessing that something I did is wrong, but have no idea what

Bracing is Qld Maple.....pretty well quartered.....had it left over from before....

I figure my only real option is to plane, chisel, scrape, sand off the braces and start over?

Each guitar I work on is allowing me to learn new problems

[jeffhigh]

Did you have the joined back and braces in your dry room for a week before you glued on your braces or only put them in after?
It does not read that way.

[nnickusa]

put everything in the box for a week

Yeah it was all in there. I'm putting all the parts in it whaen I'm doing these, now.....

No idea what happened, but off come the braces, and start over....bugger it!

On a happier note, I made my first rosette for this one out of some jarrah burl, and am very pleased with the result of that, at least.....

jarrah rosette 001 (Small).JPG (73.33 KiB) Viewed 10774 times

jarrah rosette 002 (Small).JPG (58.95 KiB) Viewed 10774 times

[jeffhigh]

How long was the back out of the box before you had the braces glued on?
Straight away or sooner is best
If you pulled it out, started measuring for brace locations, cutting notches in the centre strip etc that is too long.
I find that thin plates absorb moisture very rapidly.

[nnickusa]

Nope, all done in 10 minutes inside the box, and the door shut again. The only thing i can think is that the brace stock may not have been in the box long enough before I shaped them....?

No idea. Next time, I'll give it a bit longer in the box before gluing up.....

[auscab]

Nick is this back with the problem built off the same plans as your first ?

My one did the same , it went concave in the lower part of the back. it was slight and came good with a fair bit of scraping and sanding. From memory I had my timber sitting in my cabinet for a good while and I have wondered if it is also to do with the brace positions for the back, off those plans ?

[nnickusa]

Yeah, same plans, from Kinkade's bok, but I've modified them a bit for a cutaway.

One thought that has occurred to me is that the dish I made for the back is MDF, and has been stored under my house, subject to whatever conditions there are outside. It probably would have absorbed a degree of moisture, and then the back could have "sucked" some out while it was pressed into the dish...I did put it in the box for a week, but it's 19mm and MDF loves to absorb moisture...

Does this sound possible? That would leave a back with relatively more moisture content than wanted, and then as it dries out again, it would cause the problem?

I'll leave the dishes in the dry box for a week or two more before I try again, and maybe line with plastic wrap as well....I'lm leave the braces and back in there for a couple weeks after I clean up from this mess....

[GregL]

Hi Nick,

What timber is the back? I reckon the only way it could "turn inside out" would be if it had a lot of moisture in it before you put the braces on, then lost a lot of moisture when it was in your drying box. I had a look at Byron RH figures on the BOM site and they seem to be pretty high lately - all above 45% with ave around 65% for the last two weeks.

Thanks,
GregL.

[nnickusa]

This is the Rimu I got off Christian, which is a softwood. I don't know if softwoods are harder to deal with vis-a-vis moisture absobtion/retention or not, but this back quite literally turned inside out, with a reversed dome of around 4mm, when it started at around 3mm the other way. After taking it out of the box this morning, it was flat in an hour. I'll see where it ends up when I'm home tonight.....

All the compnents were in my dry box for a week at less than 45% RH, so ambient conditions should not be an issue, and only exposed to the ambient for 10 minutes while gluing up. The box gets back down to 45% very quickly when I close it back up....

[ozziebluesman]

G'day Nick,

I have issues with humidity here in Townsville. On my first acoustic guitar which has a sassafrass back the same thing happened to my plate. Sassafrass is also closer to a softwood than a hardwood so I put it down to that fact. Since then I stablise my material in the drying box for at least two weeks before working on it. If the humidity in the shop is high I have an aircon which will bring the humidity down to 45% in the workshop. I havent had any troubles since.

Cheers

Alan

[nnickusa]

Cheers, Alan,

that's my plan. Tomorrow, everything goes in the box, and I'll leave it shut for a couple weeks to make sure it's all good and dry before I do any more on this one.

[Allen]

Lutherie is a fickel mistress Nick.

I've had a few turn themselves inside out for no apparent reason whatsoever. Even when you do everything right, sometimes wood just want's to fight you the entire build. It happens to all of us. Thankfully not as often as when I first started.

[nnickusa]

SHIT! I thought I was over women problems

Looks like you all had a great week with the class. Well done. Do the ones that've posted here know they're on the hook?

[Allen]

Worse than that. Amy is from Lismore and is teed up to build another uke with Micheal helping out. We had a silent auction for the uke kit we made up as part of the Master Class at my place on Friday and she went home with some really pretty New Guinea Rosewood and Indian Rosewood trim. Will make a really pretty instrument. Must get photos of it when complete.

I also sent Miguel home with some Blackwood to get a little Aussie over to New Zealand.

[ozwood]

Hi Nick,

I have just used some of Christian's Heart Rimu , with No problems , so I don't think that is the issue , having said that I did have it sitting in my dry room for a long time all the way through the build ,but I have found it a wonderful wood to work with and pretty stable as well. I use two hygromters to keep them honest , I have both witnessed and heard of some horror stories caused by faulty or inacurate hygro's , so can I suggest you have a second one around to confirm what the first one tells you .
I have three in total, two in the dry room and one in the workshop.

Cheers,

Paul.