A guitar that DOES NOT WANT to get built!

[nnickusa]

Have you ever had a guitar that just doesn't want to get built?

The one I'm working on now, the same one on which the back turned inside out, has decided to turn the bloody top inside out as well!

The only thing I can think is that the dry box I built is getting REALLY dry, and the two humidity metres I have aren't recording it properly. It's been quite dry here the past few weeks, and everything was going well. The top sat in the box for a good month, along with the braces. On every inspection, after bracing, it was fine. I carved the braces, and stuck it back in the box, and viola! Next morning, very neatly inside out ...

Now I've got the terrors about re-bracing the back

I'm at my wits end on this one. i think I'm going to take it out, and let it sit at the RH in the open and see what happens.(round about 40-50% lately). Way too much bracing to scrape off the top, as the bridge plate and all is in....Starting to feel like my middle name is Job!

[Tod Gilding]

Hi Nick, This one is giving you some trouble,and unfortunately I'm not experienced enough to offer too much advice, but I was wondering what type of hygrometer you are useing ? Digital or analogue, if it is analogue then you can check it with a salt and water mix (you possibly already know this procedure),I have also been braceing tops and backs and I'm not that far south from you (we would have similar RH ) and whilst I have had to do it a little here and there due the fluctuating RH as I don't yet have a humidity controlled area to work in ( Yet ). but my plates have not been experiencing any more movement than I would expect. whilst I'm sorry to hear about your probs, I will be watching this post and hopefully someone here can work out what's happening.

[Tod Gilding]

Sorry Nick I should have asked if you check the RH at Cape Byron, They list the current RH every 30min by the look of things here http://www.bom.gov.au/products/IDN60801 ... 4599.shtml

My workshop is about 2Klm from Smokey Cape Light house and I can get the RH from there 3 times a day, it is not always the same as my Taylor Hygrometer tells me in the workshop but is a good way of telling if something is not quite right and as a guide'

sorry if I'm telling you something you already know.

[kiwigeo]

I'm at my wits end on this one. i think I'm going to take it out, and let it sit at the RH in the open and see what happens.(round about 40-50% lately). Way too much bracing to scrape off the top, as the bridge plate and all is in....Starting to feel like my middle name is Job!

I keep my workshop at 40-50% RH. What sort of humidity is your dry box running at?

If humidity in the open is 40-50% then leave it for a few days and see what happens.

Re scraping off bracing....you might as well get in some practise as its something everyone gets to do at some stage. Dont muck around...just pick your biggest meanest chisel and go for it. I actually love attacking a back or top with a chisel and demolishing braces. The chisel work shouldnt take very long....I then follow up with 80 grit sand paper until the worst of the debris is gone.

[charangohabsburg]

The top sat in the box for a good month, along with the braces. On every inspection, after bracing, it was fine. I carved the braces, and stuck it back in the box, and viola! Next morning, very neatly inside out

Sorry to read about your bad experience Nick!

If I understand you well you put the not braced top in the drying box for some time, take it out, brace it, and put it back to the box. So when you take the top (or back) out of the box it immediately starts to pick up moisture - much quicker than you might believe*). So by the time you are finishing gluing on the braces the top's moisture content has gone up considerably putting the braced and nicely domed top back in the drying cabinet will have the effect that the top will lose again the picked up moisture leading to the result you got. If you would leave the top outside the box it probably would achieve an even higher doming (in the right direction).

*)
When I receive wood orders in wintertime (which means ca. 25% RH inside our heated buildings, outside RH may be well above 40%, RH at the place of origin (Spain) about 60%) and leave an unpacked back on the table, after 10 minutes or even less it will be cupped, the edges pointing upwards, because the moisture evaporates really fast on the upper, to the air exposed surface, but much slower on the underside where the table top slows down moisture loss of the wood. This just shows how fast moisture gets in and out of the wood.

[charangohabsburg]

The chisel work shouldnt take very long....I then follow up with 80 grit sand paper until the worst of the debris is gone.

After the chisel work, instead of the sandpaper my personal preference would be to would first scrape down further with a cabinet scraper and then get rid of the remains of brace wood slivers and glue with steam, then press the top flat between two pieces of plywood, chipboards or whatever, weighing it down with some books you don't plan to read or consult during the next 24 hours.

[nnickusa]

Well, I just got back from the shop, and after a day at around 45-50%Rh, according to my checks on BOM for Cape Byron, Thanks Tod, GregL had sent me the link when the back flip-flopped, and the top is absolutely perfect. The metres(1analogue, 1 digital) have been reading between 35 and 50%Rh for the past month, but, while I can check for saturated conditions, I can't sheck for really dry ones. I believe they aren't reading the lows properly, and I'm gluing the top on in the morning, and gluing up the back braces too.

Markus, my dry box IS my go-bar press. I only do 10 minutes at a time, and close it back up. I'd guess that if I'm knocking 20-40%RH out, at 45%RH ambient, it may get down to 20% in the box, and that may explain the potato chip effect.

Anyway, buggered if I know, and I'm tired---busy night cooking.....

[charangohabsburg]

Markus, my dry box IS my go-bar press. I only do 10 minutes at a time, and close it back up. I'd guess that if I'm knocking 20-40%RH out, at 45%RH ambient, it may get down to 20% in the box, and that may explain the potato chip effect.

Nick, it's these 10 minutes which gets you into the problem.

[nnickusa]

RIGHT! I now plan on marching into the bedroom, boldly and brashly informing the wife that I am turning the guest room into my new fully climate controlled guitar building studio.



Try not to get hit with the blood splatters

[Tod Gilding]

Yeah Nick Get some sleep mate, but then let us know if those readings you are getting are in the dry box or outside ? as Markus has said,I find that the plates Less than 3mm will react to change in RH almost immediately where as the braces, neck block and end block will react a little slower due to their thickness, we are told to leave wood at the required RH for day's to adapt but I am finding that wood dry's and is hygroscopic in a lot less time than most think,and I am finding it to be minutes rather than day's. granted that I don't have available a moisture meter, but I have learnt through observation that it IS MINUTES not day's.

[charangohabsburg]

Try not to get hit with the blood splatters

I was thinking about how I would solve the problem (I am really privileged with normally no big RH fluctuations within summer or wintertime). I can't help pointing out that the old masters did not use climate controlled guest rooms when creating their great guitars. But it is known that Antonio de Torres, when building in Almería (south coast of Spain where it can get really humid) used to do the critical assembly steps "burning his midnight oil" as José Romanillos said. This meant that it was enough for him to wait until the relatively dry evening wind coming down from the hills was enough to bring his wood to a consistent and reasonably low enough MC. He seems to have used a shop made hygrometer made of wood strips, probably very similar to the one I made:



So, consistent RH at assembly is much more important than low RH. The doming of top and back will be enough to prevent cracks when the guitar gets brought into dryer climate, while completely flat (or too flat) tops and backs may crack in dry climate when built at high RH.

I hope this helps to prevent a massacre in your bedroom.

[Tod Gilding]

Nick, You Just said that your getting 45-50% on BOM but when I just looked it's saying 78% this evening ????

[nnickusa]

Thanks Markus, I might make a little thing similar to your timber meter and see what happens here. I've also wondered about how absolutely critical the RH actually is, given that controlling our environment is a relatively new phenomenon, and guitars have been built for centuries, without the benefit of climate controlled factories. I built my first one without benefit of RH concerns, and it's fine, though I did buy a humidifier for it, and keep it in it's case whenever not being played, just to be on the safe side. Now, a few guys seem to use a variant of the dry box. Markus from what you are saying, It seems to be unneeded, as 10 minutes out of it will undo all the drying that's been done?

Tod, yeah yesterday got a bit damper, but over the past few weeks, it's been largely 50% ish. Also, I have a hygrometer inside and outside the box and they are usually 20-30% apart. Also, I'd guess that, as warmer air holds more moisture, I think I was told, that the RH ought to flucuate to some degree during the day according to temperature differentials, so lower in the warmth of the day and a bit higher in the cooler night. Does that sound right?

[ozziebluesman]

G'day Nick,

In my research on humidity levels and guitar building it is more about where the guitar is going to live. For instance up her our average humidity is about 60% so 60% is fine to build a guitar in if the guitar is going to live here. The problems arise when the guitar goes on a trip down south where it is much drier for say two weeks. Also if the guitar is taken on airoplanes constantly it is in danger of drying out as the baggage part of a plane is subject to near freezing conditions and very dry humidity at 30,000 feet in the air. Sometimes I can't get the humidity down here when it is stinken so I believe that 50% in my drying box is better than 80% humidity levels in the workshop. My first few guitars where built at a constant 60% and they have not developed any issues.

Better though if you can get a setup so you can keep the wood stable at 45% during storage and building.

Cheers

Alan

[Tod Gilding]

Yeah, That sounds right Nick, but also we get changes with wind direction, if the wind comes from the west you will normally find a dramatic drop in RH. regardless of temperature.

I have a Taylor Hygrometer and a digital, they read different, but I know that the Taylor is accurate, the digital ones reads close around 40-50% but then starts getting increasingly less accurate as the RH increases.

[graham mcdonald]

If you are living on or near the east cost you need some sort of climate controlled environment to do your gluing. A 'dry box' is not going to cut it, as Nick has found. Think about enclosing an area about twice the size of your go-bar deck, which doesn't have to much bigger than 900 x 1800, with a door on one end or the side. Cheap Bunnings 4x2s for the frame, a second hand door and wrap with plastic sheet and or sisilation (did I spell that right? basic aluminium foil insulation stuff used under roof tiles)to seal it. A large knock-down wardrobe might work as well. You can get dehumidifiers for around $200 and you will be surprised at how much water you pull out of the atmosphere.

cheers

graham

[charangohabsburg]

Markus from what you are saying, It seems to be unneeded, as 10 minutes out of it will undo all the drying that's been done?

I don't think that in 10 minutes all drying will be undone, but in the beginning the drying process is pretty fast and then slows down considerably. Although also hardwoods will cup quickly when laying flat on a table after having been brought from low RH to a much higher one (or vice versa) it will take several days until it will stop moving, e.g. reaching its new EMC. With spruce or western red cedar EMC is reached much quicker, I reckon that for a 2 mm spruce top this will be the case in about 24 hours. Or maybe in 12 or 36 hours. I never measured it, just observed the movements of the wood (some hardwoods will just stay in its cupped state, so it is better to get it acclimatised either clamped or stickered, e.g. exposing either both sides or no side of the board/veneer/top/back to the air).

[jeffhigh]

Ive got 4 moisture meters. 1 digital, two dial and one cross laminated stick. Right now they are all reading around 35RH yet I am 50 metres from the sea, go figure.
My work area is in my garage, which I cannot control and getting sick of waiting for a dry day, I put a Dimplex dehumidifier in my music studio room and simply move the portable go bar deck and materials in there for critical gluing operations.

[Tod Gilding]

Yes Jeff no use trying to figure it out I don't recall last Winter's air being this wet, I managed two guitars last year with very little trouble, this year I'm struggling to get one box closed.

Also Jeff, A cross laminated Stick ???

[charangohabsburg]

Also Jeff, A cross laminated Stick ???

If this is a question about what that stick is, and in spite of me not being Jeff, the pictures here would tell you the answer.

[jeffhigh]

Yep thats the idea

[Tod Gilding]

Thank you very clever idea. learn something every day. hopefully

[charangohabsburg]

The nice thing with the "cross laminated stick - hygrometer" you can see in 1:1 scale what happens with a braced top, and how fast it happens. Observing a "cross laminated stick", depending on weather conditions even opening your shed's door for just two minutes will make you think seriously about what you will do in the next hour!