Car as a Kiln

[Dave Weir]

I have been making necks out of stuff like Ipe and Goncalo Alves I get from a Deck Supply store. I know they don't bring it down to the moisture level I want, so I have been drying it in a converted supply cabinet with a heater and fan. Anyway, I was thinking about the worst thing you can do to a guitar is leave it in a car. So what if I do that first? Bring it to about 1/4" oversize and then leave it in the car? It would go through a daily cycle of heating up to 110, blast in with the air conditioner when I go to lunch, back up to 110, then blast it again on the way home from work. I build about a guitar a week so I could keep maybe 12 in a little rack on the floor. After a couple months of torture, it would be ready for anything. It works for Navy Seals.
I'm sure it's not my worst idea to date, and I'm going to try it anyway, but just wondering what you all think.

[Mark Swanson]

Might work fine. But, the reason leaving a guitar in a car is bad isn't as much because of the danger to the wood (of course that IS there) but it's because the temperature will melt the glue joints. It'll soften them enough to let the stresses on the guitar win out, and pull the guitar apart.

[Randy Roberts]

Steve Senseney routinely dried his wood from green in the car.

I believe he placed it in a black plastic trash bag and closed it and left the car in the sun. Once or twice a day he would take the wood out, turn the bag inside out, and seal the wood back up in the bag. By sealing it up he controlled how fast the wood dried, and I don't think he had muck problem with checking and cracks, because this kept the wood from shrinking too rapidly.

Haven't heard Steve around these parts for a while, but maybe he will chime in...

[Henrique Schneiter]

Actually it sounds like a pretty good idea to me. But please tell me about the string nut on that picture.

[Mark Fogleman]

I'm thinking you'll get higher than 110f in your car in SOCAL (assuming you are there) parked in the sun. I've not used them, but there are solar-powered exhaust fans that could be used to regulate the temperature and remove the humid air. One of the most popular references for solar kilns in the woodworking circles was published by Virgina Tech ~40 years ago. If you've not seen it click here: https://pubs.ext.vt.edu/420/420-030/420-030_pdf.pdf On the last page of a Woodweb document also by Wingert from Va. Tech is a procedure to calculate wood moisture % using a sample board, postal scale and an oven: http://www.woodweb.com/knowledge_base/S ... gns_4.html

[Dave Weir]

The car is not as practical as I hoped. I would need to build a fairly elaborat rack to hold 12 30" 2x4s at a time. It seems like for not much more effort I could a build the whole solar kiln. I'd like to do it with no external power required. Maybe a small solar powered vent system. The comment about reversing the black bag and how that would heat up and then dump off the condensation appeals to me. Thanks for the inspirations.

[David King]

You need a 1964, 21 window VW bus.

[Art Davila]

Actually it sounds like a pretty good idea to me. But please tell me about the string nut on that picture.

Looks like a brass string retainer, holding strings against zero fret.

[Dave Weir]

The "inverted nut" is made of 1/4"x 1/8" Nickle Silver bar. I bend it the radius of the fret board and the slot the bottom pretty much like you would slot the top of a regular nut. The strings slide freely, they aren't pinched. It creates somewhere around 9 degree break angle. There's more pictures Weir Guitars Facebook.

[Dave Weir]

I went ahead and built this little rack. I think the stationary solar kiln is the better option, but I thought I might learn something from this.
First I need to address safety concerns. I don't need 60 pounds of 2x4s flying around in a panic stop.
Also, I don't think I want direct sunlight on the wood. It will all get trimmed anyway, but doesn't seem good. So some kind of tent.
Pretty mild So Cal day. at 3:30 it was 65 degrees. 110 in the car. Humidity said 30%, dry. I assume anything in the dry range is going to be pulling water out of the wood.
I'm not sure how humidity percent relates to moisture percent in the wood. I know its not the same, but is there some relationship? Like if the wood is in a 30% environment for 100 years, will it go to 6% by weight? More research required. Please chime in if you have an info or ideas.
I have several kinds of wood. Maple, Lyptus, Merbau, Ipe, Cumaru, Kayu Kuku. Everything weighed and labeled.
Ulimately these get trimed to 1". Right now they are about 1.25 to 1.45". I'm thinking I may just trim them all to 1.25 or maybe a little less. If they are going to twist or bow more than a quarter inch over two and a half feet, I should probably scrap them anyway.

[David King]

There are charts relating RH to wood moisture content and 50% RH is about 8% MC so 30% RH might well get you to the 5.5 or 6% MC range.
Outdoor covered and unheated space around here (say 75% RH) will usually stabilize at around 12% MC.

[Mark Fogleman]

Short of using a moisture meter, I would weigh the individual pieces once a week and track their weight loss as they dry. Each species of wood looses water at a different rate. When weight loss slows/stops you're close to equilibrium moisture content.

I would also seal the ends of those boards if you haven't already. Moisture escapes from the ends much faster than the middle of the board. This can cause splits and warps. You can get the endgrain sealer at most woodworking shops or make a good one by grating a brick of Gulfwax paraffin (get it in the canning supply section of a grocery store for ~$2.50 for 4 brick package) with a coarse cheese grater. Add enough mineral spirits (~1qt) to create a solution about as thick as latex paint. It needs to be done on a warmish day or the paraffin won't dissolve. Brush on a ~1/16" coat on each end grain and ~1 inch up the board from the end and you're good. If you already have cracks you'll need to drill a hole through the board at the skinny end of the crack with a 1/8" or 1/4" (for larger cracks) drill bit. This creates a hinge relief for the crack and will stop its growth. Apply some of your sealer to the crack too.

[Jason Rodgers]

I've heard of drilling out the point of a crack in a ride cymbal to stop its travel, but not in stickered, seasoning wood. Good idea to salvage a few inches of usable wood, instead of lopping the whole end off.

[steve flicker]

these guys i knew used an enclosed horse trailer with a couple heat lamps and a couple dehumidifiers. they were furniture makers and would dry from freshly sawed down to a certain percentage then bring them into the shop. im sure you could use a closet with a dehumidifier if you had one to spare, but the solar kiln is a greener solution.

[Dave Weir]

I've had the wood in a storage cabinet with a heater and fan and some kind white crystal stuff that absorbs moisture. It keeps it up around 90 degrees, but the weight of the wood hasn't changed much since January. It was already air dry so I'm not sure what to expect.
My moisture doesn't have a chart for the actual wood I'm using, so I have to guess it's kind of like rosewood or something. But on some of the Ipe it says it's 50% water. I'm pretty sure that's not right. Anyway, I'm still using that drying closet also so I can compare the two.

I sealed the ends with some latex paint. I'm sure the Wax mixture is better but I have about 6 half full gallons of assorted off white house paint.

I checked one of the moisture/humidty charts and this was kind of interesting. At 3:00 it's 100 degrees and 30%. After 15 minutes of medium air conditioning, it's 80 degrees and 25% humidity. According to the chart, the wood is going to seek a lower moisture content in the air conditioned car than in the sun baked car.
http://www.csgnetwork.com/emctablecalc.html
Then I park it and it goes back up to 100, the humidity is still at 25%. So I think the cycling may be useful.
I'm not sure if my logic is even sound, but I am trying to get it very dry, and then let it come back up to equilibrium.
I feel like this is going to give me the most stability in the long run.

[Mark Fogleman]

You're bringing in drier cooler air. The air RH should fall as the temp goes up if the actual number of water molecules (Absolute Humidity) stays the same. It's how the closet heater dehumidifier works. Warm air has more energy and it takes energy to move the water molecules out of solution....sorry to get all physics nerd on you...I worked for a medical device company that makes respiratory humidification systems for critical care.

Another Old School way to estimate moisture content is in a dry environment (like SOCAL) crosscut a salvage piece of the lumber, wave it in the air a few times to cool off from being cut and place it against your skin. If it is cool, the moisture content is higher than your air content. If it's really cool then it's really wet. Repeat this with a piece of wood that you know is dry. It should be warmer to your skin.

I suggest stop worrying about the RH of the air and focus on the air temp and ventilating the space.