Thread: #1 Acoustic Build

Sticker them, see here - Agroforestry they are too nice to treat any other way than the best you can manage.

You can still do a lot of lutherie in higher humidities, neck making, bending sides, make molds etc. We should get a dryer period in Sep/Oct and I recommend you brace a number of tops and backs then. When summer hits the Sydney humidity is consistently high.

Originally Posted by Sebastiaan56

Sticker them, see here - Agroforestry they are too nice to treat any other way than the best you can manage.

Thanks Sebastiaan. Would it be ok to keep them in the shed given that the humidity is swinging quite rapidly these days or should they be stickered in the house where it's a little more consistent?

I've spent the last couple of weeks contemplating body shapes... The Kinkead book came with a full size plan for making his Kingsdown model and the Chris Wynne workbook also had dimensioned body drawings to work with. I sketched up the Wynne body on some graph paper but found I didn't really like either that one or the Kinkead version. So some widening of the waist and slight lifting of the upper bout has gotten me to the template stage. I cut this one out of some sort of low density plastic sheet I had lying around. For obvious reasons I've named it #1.

Attachment 143101

While still collecting various items a box from Stewmac arrived with my bending iron and some other goodies. Couldn't wait to give it a go so I went all out on a thin strip of Meranti and I've now done my first bend. I did managed to split it a couple of times but I think this had more to do with the fact that the iron takes so long to heat up and I was keen to get bending...

Attachment 143102Attachment 143103

I leave my bending iron (same as yours) on for a good 30 mins before attempting any bending. Even then I have it just off the top setting for most timbers. Thinner bends more easily than thicker and sides can always be reinforced. Its a very cool experience bending IMO. One of my favorite parts of building.

As for the timber I'd try and keep it somewhere more stable than the shed. Ive been watching how much humidity changes during the day at my place and a 50% swing is not uncommon. That said it does take time for the moisture to change through a piece of timber. I used to make up drying curves when I was in the paper industry but havent got the gear to do it for timber so I just keep it under the house now. It is more humid than my workshop (the kitchen bench) but seems more stable than the garden shed.

I like your shape, big bottomed girls do it for me!

30 minutes to warm up the iron, OK, I'll keep that in mind. I did notice that it was still warm about an hour after I turned it off the other day, must be a sizable chunk of metal in there...

I've been thinking quite a bit about the humidity as I've recently been monitoring it myseIf. Now since what's actually being monitored is relative humidity I believe the swinging that I'm seeing is just the daily variation in the local airmass' ability to carry moisture. That is, as the temperature of the air drops overnight, the amount of moisture it can hold reduces and the relative humidity rises without any increase in the actual moisture content of the air.

I'd say this would tend to be more pronounced up your way Sebastiaan as the daily temperature swing on the ranges is often greater than down here in the basin.

Given the absolute humidity hasn't really changed I don't see how this daily variation would affect the timber.

I have also seen a longer term variation, from say last week where the shed averaged about 60 to 65% relative humidity to this week where it's been raining for 3 days and the average is now about 75 to 80%. This is indicating a real change in moisture content of the air and would certainly need to be considered but it's really only a 10 to 20% change over a period of a few days and will probably start to fall soon given our forecast is for drier weather to kick off next week.

Does this make any sense and have I been overly concerned about the wildly swinging daily variation in relative humidity?

Originally Posted by stevemc32

30 minutes to warm up the iron, OK, I'll keep that in mind. I did notice that it was still warm about an hour after I turned it off the other day, must be a sizable chunk of metal in there...

Spray a bit of water on the iron with a misting bottle. When the water beads immediately and dances around on the iron it's hot enough.

It's the Relative humidity rather than absolute which governs how the wood takes up or sheds moisture.and the equilibrium moisture content it attains
Yes there is some lag time between changes in RH and changes in the MC of a soundboard or back but it will still change within an hour. Once you glue a brace on across the grain you will see that effect quite readily

Thanks for the help guys.

I'm still struggling with this RH and AH thing so I'm off to do some more reading on climate control. Unfortunately when I built the shed I didn't think I'd ever have to consider sealing it off. The tin roof has a layer of insulation under it but the only door is a 1.5m roller door that I normally leave open when working...

Not sure I've got room for a controlled cabinet but might start to think about that. If I was using a cabinet would this just be for storing the wood that's not being used. Say I wanted to clamp up part of the job overnight would I have to build a cabinet big enough to house it in this state or would it be ok to leave the job out whilst clamped and then replace it in the cabinet when done?

Like you , I do not have a sealed area to build in.
The parts of the guitar which are most affected by RH are the top and back plates.
the critical operations are
gluing braces to top and back
gluing in the rosette.
gluing on top and back to the sides

These all have the effect of restricting cross grain movement and if done when the wood is too wet can lead to cracking and loss of doming when conditions are dry.
So at the time of carrying out these operations it is essential that the wood is at a suitable moisture content, which is generally considered to correlate with a RH of around 45.
Without climate control you have the choice of
-waiting till the weather is dry
-using a drying box for storage and working quickly after removing the plate
-drying the plate with a blow heater before glueup (but this requries some judgement)

Thanks Jeff, seems like a real pain in the butt having to rely so heavily on the perfect weather conditions...

The shed does tend to warm up quite quickly when I'm working in there with the roller door closed so I might try Martin's suggestion in the other thread of a small oil filled heater to try to regulate RH via temperature. They are pretty cheap so nothing to lose I guess but a few kWh on the meter for an experiment.

Thanks again guys, no further progress on the build at the moment as I'm finding myself drawn to researching shed air conditioning systems - must resist!

in this current weather and time setting ( ie dark at 6 00pm) i have found that the best chance for getting RH figures closer to 50-60% is to check the meter at 2 or 3 o'clock before the afternoon chill kicks in. Out of 3 weeks ive had 4 days where the RH has been right. Im currently making a ukelele and cant glue yet until better weather/warmer

I got hold of a very cheap oil filled heater yesterday to give it a bit of a try in the shed overnight. Only cost $23 for a 1kW model at the local Go-Lo.

It has three settings and the lowest one is just 400W so that's the setting I used with about 1/3 scale on the thermostat setting. Last night's weather definitely gave it a test with a solid night of continuous showers where the ambient RH got up to 90%. Good news is that the little heater kept the shed about 5 degrees warmer than ambient for the whole night and the RH in the shed topped out at just 71%.

With just a little bit of work I think I could get it mostly sealed off which I suppose would give even better results. The roller door would still be the limiting factor.

Combine that with the fact that these days you can get a little one horse split system air conditioner for not much more than the price of a bending iron and I think Summer just got a whole lot more pleasant in the shed.

Originally Posted by xray

in this current weather and time setting ( ie dark at 6 00pm) i have found that the best chance for getting RH figures closer to 50-60% is to check the meter at 2 or 3 o'clock before the afternoon chill kicks in. Out of 3 weeks ive had 4 days where the RH has been right. Im currently making a ukelele and cant glue yet until better weather/warmer

G'day xray, it has been terrible weather lately... Just to improve my understanding - are you happy to proceed when you spot the relative humidity reach the level you're after on any given day or are you waiting for a general (seasonal) change in conditions before proceeding with the critical operations as listed above by Jeff?

Thanks for your help guys, it's much appreciated.

Steve,

Try tacking a large sheet of plastic over the inside of the roller door to provided some seal.

Cheers Martin

Hmmm, good idea but not sure if I could do it since the roller door is the only way in and out of the shed. I could possibly build a small airlock around the roller door but this would take up quite a bit of space and I'd be back to the same situation as building another cabinet. Thinking about a set of double doors to replace it.

Martin, do you find that using your dust collector causes some climate control problems in your workshop. My dust collector is only a small one but it's rated to evacuate the full volume of the shed in about 3 minutes and I assume this air must be replaced by whatever happens to be outside at the time.

Originally Posted by stevemc32

Martin, do you find that using your dust collector causes some climate control problems in your workshop. My dust collector is only a small one but it's rated to evacuate the full volume of the shed in about 3 minutes and I assume this air must be replaced by whatever happens to be outside at the time.

All my machinery is in my garage....the workshop next door is a "clean" working area.