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Span cedar just purchased 6-8% moisture-when can I use it ?
http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=27648		 Page 1 of 1
Author:  John A [ Tue Jun 01, 2010 1:23 pm ]
Post subject:  Span cedar just purchased 6-8% moisture-when can I use it ?
Hi,

So I just managed to screw up two necks this past week.

I went out this morning and got some Spanish cedar to make 4 more blanks to replace the ones I screwed up and to start the next two. I got the wood from a cabinet shop and they told me everything is kiln dried to around 6 to 8% moisture.
I plan to cut everything to size today - but how long should I wait to cut and glue my scarf joint and glue my head and heel blocks (classical)?
This has stopped all my work on the guitars until I complete this. I have every other part done, minus the kerfed liners, so the only thing left is the assembly.
So do I have to wait to acclimatize the wood? if I glue up now and I get some bending, it will be carved away anyway- or planed on the fretboard side.

ugh - I know this has been asked before - but the anxiety is killing me... need to know... gaah
Author:  Alexandru Marian [ Tue Jun 01, 2010 2:30 pm ]
Post subject:  Re: Span cedar just purchased 6-8% moisture-when can I use it ?
In ideal conditions you need to wait for a couple months or so, checking it every day with straight edge to see if there is any movement. Additionally you can cut a small sample and weight it daily using a 1/100th gram jewelry scale and track moisture loss.

But in any case, anxiety and impatience are your greatest enemies. It would be far better if you complete a decent guitar in 1-2 years, than something unusable in 2 months. And with less wood waste - which is very important.
Forum searches are your best friend. In my couple years I was spending like 2h a day rummaging archives.
Author:  John A [ Tue Jun 01, 2010 3:31 pm ]
Post subject:  Re: Span cedar just purchased 6-8% moisture-when can I use it ?
I tried searching and got everything from a week in my environment to a year or more. I did not find anything dealing with necks and Spanish cedar. The wood has been dried and kept in the hardwood shop for quite a while already. I have been looking at it already for several months.
Today they cut it for me into the sizes I need, and then I have to rip it again to get more specific sizes. I am just curious how long I should wait before I cut it yet again and glue it into a neck blank. Since the wood is dry - wouldn't it just have to acclimatize to my environment - which is 35% to 45% year around ?

I guess I am getting at this - what if I cut it to size today - into 24" by 3" sticks - and then let it sit for a couple of weeks till I am ready to glue it together - would I be ok or would I be strongly recommended to wait much longer ? What would happen to a neck blank ? how wold it move ?
Author:  JohnAbercrombie [ Tue Jun 01, 2010 3:33 pm ]
Post subject:  Re: Span cedar just purchased 6-8% moisture-when can I use it ?
John-
EDIT: John, you were answering some of these questions as I typed... I gotta get faster!

Though the wood may have been kiln-dried, how has it been stored in that cabinet shop? Is the humidity controlled there?

If you have a postal or other accurate (digital or triple-beam) scale you can just store the (unglued) blanks in your (humidity controlled) shop and weigh them daily; keep some records and watch for the weight to stabilize..

If you want to figure out the % moisture in your wood, you can take a small slice, weigh it, and then dry it in the microwave (carefully- wood fires in microwaves give all your food a BBQ flavor!). Calculating the %water is fairly easy using the before/after weights.

If you see the wood 'moving' when you rip it, that could be a warning sign that the moisture % is not consistent throughout the stick.

That said, if your Spanish cedar is fairly straight-grained, you can probably 'get away' with using it quite soon. I've found Sp. cedar to be quite stable, and you will have some chances along the way to straighten it up a bit if necessary.

Laminating a neck can help with these sort of concerns, but isn't traditional for classicals.

Are you putting carbon fiber or other 'reinforcement' into the neck?

If you aren't using epoxy to glue the fingerboard to the neck, you'll probably be affecting the water content of the wood a bit anyway.

All 'food for thought...'
Cheers
John
Author:  John A [ Tue Jun 01, 2010 3:56 pm ]
Post subject:  Re: Span cedar just purchased 6-8% moisture-when can I use it ?
John - thanks - your post is helpful
Quote:
That said, if your Spanish cedar is fairly straight-grained, you can probably 'get away' with using it quite soon. I've found Sp. cedar to be quite stable, and you will have some chances along the way to straighten it up a bit if necessary.


This is my thinking too - I have fairly straight grained wood.

I will cut it and see if there is movement - I do not have a scale - nor the funds to pick one up now.
I am not sure if the room they store the wood in was humidity controlled, I think it is - but who knows if they are actually keeping up with it. I see them building boxes and projects with the wood they sell. They are a hardwood dealer.

I am not using a neck re-enforcement nor epoxy either. I may slice it all tonight, maybe cut the angled scarf Friday and then wait for a couple of weeks or so - while I cut kerfed lining and begin the soundboards, and the backs of the guitars I am making. This will give me about 3 weeks. Then I can glue everything and carve it all in about a week (wishful thinking).

thx!
Author:  Alexandru Marian [ Tue Jun 01, 2010 4:27 pm ]
Post subject:  Re: Span cedar just purchased 6-8% moisture-when can I use it ?
This water/epoxy/FB concern is less valid for the Spanish method, where you glue the FB to an oversized wide uncarved thick neck. At least I never got any backbow yet using fish glue which is water based.
Author:  Jeff Highland [ Tue Jun 01, 2010 4:47 pm ]
Post subject:  Re: Span cedar just purchased 6-8% moisture-when can I use it ?
I had been using epoxy for fretboard gluing but recently had two where i did not want to deal with epoxy squeezout.One was a fretboard replacement on a 10 year old guitar.
So I spent a few minutes with a heat gun drying and heating the gluing surfaces on the neck and the fingerboard to compensate for the moisure I would be adding with the HHG.
Used a flat caul on top, no problems
Author:  truckjohn [ Wed Jun 02, 2010 1:28 pm ]
Post subject:  Re: Span cedar just purchased 6-8% moisture-when can I use it ?
Unfortunately, if you followed much of the "How long should I wait" wisdom out there... You would *Never* actually build an instrument.... but your kids and grand-kids would have a great stash of wood to use when they start building 20-40 years from now... :lol:

All of the cabinet makers I know locally insist on *ONLY* using properly cured and kiln dried wood with 6-8% internal moisture... They get too much movement if they don't... Translation -- their cabinets and cabinet doors split apart...
and guess what -- if the doors on your expensive hand made cabinets split apart.. The cabinet maker has to make you some new ones for free...

What you really need to know... Will the wood twist or warp crazy when it moves... or does it "Behave nicely?"...

Check out the wood carefully -- look for any twist or warp.. Joint an edge flat and true... Mark that edge.
Take it out in your garage or shed or some un-climate controlled space... Stand it straight up with air circulation all around. Leave it there for a few days to a week...
Check it daily -- look for CHANGES in warping and twisting... especially twisting.... If it twists when the humidity changes -- Reject it for neck use.... If it bows a little bit up/down -- it will probably be OK... If it bows side to side -- reject it. If it is rock steady and doesn't move... Great..

Then bring it back into your climate controlled area.. Stand it up straight and watch it again for a week... If it bows back to its original shape without twisting.. Great.. If it stays rock steady.. Great... If it twists as it dries out... Reject it.

Honestly, you will probably be able to tell most of what you need to know within 1-2 days...
Remember.. Twisting = Reject... Giant bowing = reject.. Side to side bowing = bad too... a bit of up/down bow is probably OK... but no shifting is really what you want...

Thanks

John
Author:  Jim Watts [ Wed Jun 02, 2010 2:39 pm ]
Post subject:  Re: Span cedar just purchased 6-8% moisture-when can I use it ?
John, you can probably start working with it very soon.
Here's a link to a chart that will help you. It list the EMC for a given RH.
http://www.finewoodworking.com/FWNPDFfree/equilibrium-moisture-content-chart.pdf
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