Primitive Archer
Main Discussion Area => Bows => Topic started by: Badger on May 23, 2018, 07:31:05 am
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Next week I plan to build a drying box, I want to make something that is convenient to use and because of very limited space it has to be as compact as possible. My plan so far is to simply enclose a bow rack that hangs on a wall and will hold up to six bows. A thermostat will be installed mostly for safety reasons as my plan is to simply use enough wattage to maintain a temperature of about 120 degrees. dimensions will be about 6" thick, 18" high and about 6 ft long. A small computer fan will circulate the air. About 5 cubic ft of air space.
Questions I have? Will I need ventilation or would seam leakage provide enough. Does anyone have a rough idea how much wattage I need to use. I would like to stay under 100 watts if possible.
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I used waterbed heaters in mine but I don't know the wattage, they might not get hot enough. Mine is just controlled to 50% RH. I think the key is finding the balance between heat and ventilation. The more ventilation you have the more heat you'll need. If you seal it up too tight you'll just end up with 100%RH at 120 degrees. I would make sure there is a spot where you can add adjustable vents if your seams are too tight.
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My indoor RH usually stays around 50% naturally, outdoors about 64%. Since I moved the bows indoors they have really dropped in MC to around 6.5% on most species
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Mine is very simple. It's just actual "duct" tape and a sheet of foam board insulation. I don't remember which insulation but it had a higher temperature rating than the rest which eased my safety concerns.
One 75 watt light bulb gets me 100-110 degrees depending on the time of year. Two 75 watt light bulbs are 130 degrees plus. I use 1 light bulb 95% of the time. The seams at the top provide adequate ventilation for me. The RH gets pretty low in there. Like 30% if I remember right.
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I was surprised how much a small increase in temperature would drop the RH when the box was full of dryish wood. I was also surprised how much a wet stave would increase the RH. I have a dehumidifier attached to my box to use in the summer and when I add wet wood.
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Yeah I don't put soaking wet wood in there. It's normally wood around 20% MC getting it down that last 10%, or holding bow pieces I'm working on when the humidity gets really high in my garage.
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Questions:
1. How long do you put wood in there?
2. Is there a danger of cracks appearing?
3. How do you prevent warping and moving of staves/saplings you put in there?
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I'd be interested to see DC's response to your questions Filip. Those same concerns are the reason that I don't put wood in there that's above 20-30% MC. I let them air dry for a couple months to get to that level 1st, and even then it's a struggle to minimize warping/twisting/cracking etc right after it's been cut.
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I've never used a box as hot as what Badger is planning so it's unknown ground for me. My shop varies between 40 and 70 %RH depending on the season. I leave my staves outside under shelter for two or three months. Then I bring them into the shop for another two or three months minimum. When my warm box starts to look empty I move a few into it and start monitoring weight. When the weight starts to level out and go up and down with the RH I give it another month and then start shaving. I try to have way more drying than I'm going to use. That way this procedure is the bare minimum. Some sit in the warm box for six months. As long as the RH hovers around 45-50% they won't get too dry. A few months ago I cut some Hazel. I weighed it right away, it was still dripping, and stood it outside. I took a small offcut and stuck it in our toaster oven at about 175F for 7-8 hours. By then it had stopped losing weight. I compared this "bone dry" weight with the green weight. It was about 65%. So 35% of the stave was water. I'm thinking this will give me a target weight, or at least something to look forward too. I'll still wait until it's not losing weight but this may tell me I'm getting close.
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Good conversation here.My thoughts on making one involved about what Ben did to get his.Some of that 2" dense foam cut to make a box to accomodate most any bow or a few bows with a light bulb or two.It will have to ventillate some to let moisture out.Not really sure it would even need a fan at all then.
Would be even handy to heat cure that smooth on epoxy too for wooden laminated bows.
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Yeah BowEd, I use it to help cure uni-bond when laminating too. I wish I would have made it taller though, as I can't fit my form with long clamps in there.
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If you put a hole in the top and one in the bottom convection will take care of the rest. If you put one on either side, not so much. It's the hot air rises thing :)
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I have a real simple set up due to limited space I made some supports for a pup tent made out of 2 electric blankets & if I'm baking a lam bow I add 2 200 watt incandescent clip on shop lights , with just the blankets I can run up to 130 f if I'm baking with the bulbs it will go over 200f if I don't vent it well it's a very adjustable and adaptable system I don't have to move my forms just set up around them and when I'm done I just fold it up and put in the closet, one of these days I'm going to make a take apart one like Bens , it doesn't have to fancy to work !
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I went through checking a bunch of my bows this morning with a moisture meter. Since I brought them in the house I am surprised at how the moisture in them had dropped. A lot of them are measuring below 6% the highest one was a yew bow at 7%. So my bow will only be for uncured stave. I got a hickory stave from Bowed a week or so ago and it was 22% when it arrived. This morning it was 11% in the handle and 9.5% in the limbs. So I will really only be using it to finish staves for a few days at a time.
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If you just want to use it as a conditioning box to keep bows or staves dry, then you can use one of those mini plug-in dehumidifiers. They cost as little as $25, they are pretty energy efficient, and not putting a lot of heat into your house. You can use it with soaking wet staves if you want. It would be great for hickory bows or horn bows.
Alan
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I didn't know they had that Allen, I will check it out.
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I got a full sized dehumidifier on clearance for $125, thought I did well. I wish I'd seen these things. There's one that does 333 cubic feet for $15. I could have bought eight of them.
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I had to buy another here for my basement.It does 2500 sq.feet.It does do the job.Cost around 180.00 dollars though.Costs around 5 to 10 dollars a month to run with electricity too.It keeps things in the range of 50% humidity.I probably have 4 or 5 analog humidity gauges around the house.I don't own a moisture meter.I did for a while once till I broke the points off in a piece of wood.I can see their practical use though.
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Can this hot box remove humidity in a matter of days?
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20 years ago I made bows in a 5'X7' corner of the garage by the water heater, space was limited, I needed a drying box I could hang high on the wall and out of the way. I made a 12"X12" box with three light bulbs on a bar, vents at the top and bottom and a dimmer switch to control the temp. With the dimmer switch the light bulbs last forever. I can barely turn the lights on to a mild glow and get 100 degrees in the box, cranked up half way I get 120 degrees. I put a shelf in my box to sepperate the light bulbs from the drying wood.
I don't feel a fan is necessary because of the natural draft front the air heating in the box.
The first shot is one of the two top vents on my box, there is one large on in the center of the box on the bottom.
The box worked so well I took it to my new shop.
The third shot is my dimmer switch to control temperature.
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Pretty good Eric.Nice pictures showing things.
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I like that Eric! I really like the idea of a dimmer switch. My basic plan is almost identical to yours except I was afraid to have a wooden shelf over the light bulbs and planned to use aluminum as it also tends to spread the heat out. .
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Badger, one of my early tries I had a 300 Watt bulb in a six inch square tube made of 1/8" ply. I lined it with tin foil and the outside of the tube barely got warm. I didn't leave it on when I wasn't in the shop though ;D
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I turned up the light for the picture, the wood shelf is far enough away from the bulb to not get hot with my normal running temperature. I start out at about 90 degrees and bump it up over time, never over 110. The stringers on the shelf are to keep the wood off the shelf for even heating with no hot spots.
I have found that wood at 20% and over may check if you don't have it really sealed. I also found that you can dry full bore if the MC is at 16% or less. I don't usually move wood to the box until it gets to 16%. If I do, I put it in for a few hours and take it out to stabilize over night then back in the box for a few hours and so forth.
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I noticed that my wood drops down to 11 or 12% in about 2 weeks or less just sitting in the house. It seems to slow down a lt at about 10%. This is where I plan to start cooking it, under 12%.
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That would be the reason I would make a hot box.A faster way anytime of year and at an appropriate less dangerous moisture content to prevent any checking.The only way I get the wood down to 8 or 9 per cent moisture without a hot box is to put my enviornment down to 35 per cent[winter time] and still will take 2 weeks more as you stated to get that last percent or so.That's doing it with the mass weighing method.
I've read where 1 percent means 6 per cent performance.So from 12 to 7 or 8 percent could mean 25 to 35 percent difference.That's a fair amount as I'm sure you realize yourself.
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Ed, I know with hickory it really makes a difference in performance. Osage does well at 6% also but doesn't fall off as bad at about 8 %.
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Foam boxes work well. I use one for my g-bows
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Steve, I have had good luck with an old 4 foot flourescent shop fixture upside down in the bottom. T12 I think is the older style about 40 watts even heat per bulb, doesn't get too hot either.