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cursley ukulele's
05-21-2011, 08:05 AM
hi folks.. having had a bit of a setback this week with a lacewood back and front bending the way i didnt want them to.. since then and with the advice of rob c i have made a board with a number of caul's attatched to it, positioned for the back and front bracing.. so, all is well, ive re-glued everything and they are holding their shape lovely.. now, because of the set back ive lost a little faith in the bracing sizes i was using, 6mm wide by 8mm high.. question is.. should i just go back to this and not worry? is this about the size im looking for?

many thanks, darryl.

Allen
05-21-2011, 10:35 AM
Your description is a little vague as to what the problem was, but I'll take a stab at what seems to have gone wrong.

You glued up your cross bracing and after it dried and you took the clamps off the top and back ended up bending like a potato chip (the wrong way). If this is the case then you braced up in too high a humidity and then when the humidity dropped the top and back lost some moisture and shrunk across the grain (as wood does). It's not the size of the brace, but careful attention to your RH that you need to be paying attention to.

Also, if this is what has happened and the RH stayed pretty much unchanged from when you braced it, then got the instrument body closed up without any drama's, then the RH dropped back to normal levels, or much lower you face the very real probability that the top and back would concave and possibly split.

If you want to do this for a living, a serious hobby, or just build quality instruments that aren't going to self destruct because of being built in the wrong RH range, then you absolutely must get a good, accurate and reliable hygrometer and either some sort of control of your building environment, or only build when the readings are in the right range.

When I do a commission that I know is going to an area of the country that has a radically different average RH to what is the norm (in Australia it can get very, very dry in some areas in the centre) then I'll build to a much lower RH than one that will live near the coast.

For what it's worth, my soprano's use 6X6mm for the transverse braces.

cursley ukulele's
05-21-2011, 02:19 PM
correct Allen.. word for word... i glued up after the rain.. my workshop is a slow in progress transformation from an old garage, so its not exactly a controlled enviroment.. ive just googled a hygrometer and a digital one is around $40, would this suffice? i'll read into this more.. it seems the further i get into building, the more i need to learn.. thank you so much for your reply my friend :)

Allen
05-21-2011, 03:45 PM
The first hygrometer I got was a digital one in the $70 range here in Australia. Used it for a few years exclusively. It seems to be pretty accurate when the RH is in the 35 - 65% range, but suffers huge inaccuracies outside of that. Not that you'd ever want to be building outside that range anyway.

I now one of these Taylor Luthiers Hygrometer (http://rosetteguitarproducts.com/store/index.php?route=product/product&product_id=55). It's a much more accurate instrument. Easy to read and doesn't require batteries.

Moore Bettah Ukuleles
05-21-2011, 05:27 PM
Don't forget the wood you'll be using needs to be stored under the same conditions that you'll be building in.

Natsok
05-22-2011, 08:22 AM
HI, just thought to paste in this link for a hygrometer, they run on batteries, but are incredibly accurate 1%, they also store readings for max and min temp and humidity ( great for seeing into the dark and challenging world of cases and storage). There incredibly cheap as is the postage.
mark

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=280642857399&ssPageName=STRK:MEWAX:IT

cursley ukulele's
05-23-2011, 01:01 PM
thanks for your answers and link guys... its gonna have to be baby steps for me i think! and the purchase of the taylor i think.. and then building at the right time.. i can do other stuff though right? make braces, necks, that sort of thing?