08 Mar. 1981|
Build a small wood drying kiln,wood crafts store utah,plans for wooden doll house - How to DIY
Because they capture the energy of the sun, solar kilns are becoming increasingly popular for the hobbyist or professional woodworker who wants to dry his own lumber, and with good reason; dried wood sold at a lumberyard is expensive.
Solar-drying kilns are the simplest, cheapest, and safest way to dry green wood quickly, and they are good for the environment since they don’t generate CO? emissions. A solar kiln can also dry wood of varying shapes, sizes, or mixed species and thicknesses in the same load. The initial investment for a solar kiln varies, depending on the size and the building materials. A small solar kiln normally dries anywhere from 800-1,000 board feet, although some can be downsized to dry only a few hundred board feet. The Virginia Tech solar kiln can hold up to 1,000 board feet of 1-inch thick lumber per load and dry it in about one month of moderately sunny weather in the mid-latitudes of the United States. To alter the size of a kiln, one needs to keep in mind an important ratio: For every 10 board feet of capacity, one square foot of solar panel or roof area is needed. In order to circulate air through the stack of wood, it’s necessary to install an electric fan. Woodworkers first learning to dry lumber, especially lumber thicker than one inch, should monitor moisture content (MC) daily to avoid drying too rapidly. There are tables available that list the safe rates for drying 1- or 2-inch thick lumber from different species. Although moisture meters don’t work well when the MC is above 30%, the design of the kiln is such that it normally won’t allow the wood to dry too fast. One advantage of pin meters (only those that use longer pins with insulated shafts) is that wood can be tested at different depths in the wood. Wagner Meters, one of the leading manufacturers of American-made pinless moisture meters, says that “an accurate knowledge of the interaction between wood and moisture needs to be at the very foundation of each project a woodworker undertakes.” If not, every project is put at risk.
Solar kilns are ideal for the hobbyist or professional woodworker who wants to save money by drying his own lumber. Although solar kilns are designed to keep wood from drying too rapidly, it is wise to check the MC level, especially near the end of the drying cycle. Share!Troy EdwardsTroy Edwards is Technical Service Supervisor for Wagner Meters, Inc., where he oversees manufacturing, quality control and IT service for their electronic measurement products for the building and construction industry. For figured, thick, prized or check-prone wood, it’s best to start the drying process with the vents closed.
I added a couple of remote sensors in the middle of the stack so I could tell when the wood was dry without having to open the kiln (Photo 5).
When you’re done stacking your green wood, attach a plastic sheet to the bottom of the fan plenum and drape it over the stack (Fig.
American Woodworker magazine was acquired by F+W Media (parent company of Popular Woodworking) in 2014. Shrinking may cause the wood to split, twist, and contort in all sorts of other weird and wonderful ways.
Whether a piece of wood is wet or dry depends of the level or percentage of its weight that still contains moisture. I have not managed to locate (as yet) anyone willing or able to kiln dry logs as I have been told that due to the uneven shape the treatment would cause more problems than it is worth!
There is an old rule of thumb saying that for every inch of diameter wood should be seasoned for 1yr. I currently have a garage I store my seasoning wood in, however, before I had space I covered them up with a cheap tarpaulin, outside my house.
Kiln and air drying are the most common methods employed to season wood, however there are numerous other ways the process can be conducted and speeded up. The kiln heats when solar energy enters the clear glazing and is absorbed on the black painted interior surfaces.
When the evaporated moisture increases the relative humidity to where it gets too high in the chamber, it releases it through vents in the back of the kiln. If the kiln has too much solar panel area, one risks the wood drying too fast, causing the wood to check and split.
It’s important to monitor drying speed by measuring the MC of the sample boards and comparing the daily rate of moisture loss with the “safe rate” for that species. Still, when just learning to dry lumber in a solar kiln, it’s best to monitor the process to avoid any unforeseen problems.
If drying is too fast, part of the roof should be covered, or the fans turned off and the vents closed during the hottest part of the day. Wengert notes that the Virginia Tech solar kiln was designed so that it wouldn’t allow the wood to dry too fast.
A pin meter measures the MC of wood by running an electrical signal between the tips of two narrow metal probes that are inserted into the wood. The major disadvantages are the relatively small area tested with each insertion, their sensitivity to wood temperature, and the damage the pins do to the wood surface. Wagner has models for woodworkers who need to measure wood moisture in all wood species–from the more common softwoods and hardwoods to rare tropical species. However, the MC will vary if the wood is going to be exposed to rain or an outdoor sprinkler, or if it’s going to be in a dry climate such as in Albuquerque, a wet climate such as in Seattle or a coastal region.
It’s also recommended that woodworkers who are new to drying lumber in a solar kiln or who are drying wood thicker than one inch frequently check the moisture levels to prevent defects later on. I have managed to obtain green wood at a lumberyard at a fraction of the price of dry wood.
Because the wood is protected from the elements, this solar kiln offers more control with much less chance of defects than air-drying provides. This keeps the humidity in the kiln from dropping too quickly and slows the drying process.
The big pile of green wood in front cost the same as the tiny pile of kiln-dried wood behind me. To prepare a base for the kiln, I leveled treated landscape timbers on a bed of river rock in my backyard.
Different woods hold different amounts of moisture (some woods can hold more than double their own weight in water), however regardless of this the amount of water in a piece of timber is referred to as the moisture content as a percentage of the weight i.e. I have collected wood from the same place within a wood with one piece being nigh on perfect (it had been laying on top of other pieces of timber), another piece (from the middle of the pile), being sound but requiring more time to season, and a third (from the bottom of the pile) still very wet and what's more, due to a large amount of mulch on the ground had started to rot and was infested burrowing insects. I have found that to get wood dry enough to use, it normally takes 1-1½yrs (for an average didge sized piece of wood). By placing the wood in flowing water for a period of a few weeks or so, the sap is washed out, and the wood when removed dries very quickly. However doing so requires some knowledge as to correct temperature, air flow and evenness of drying.
Drying wood in a controlled environment requires much less time and allows the wood to contract without warping.
However, if there’s not enough solar panel area, there’s the risk of never being able to dry the wood below 15% moisture content (MC).
Although the temperature will likely rise inside the kiln, the trapped air will quickly reach 100% of its capacity to hold water and the lumber will stop drying.
However, if the kiln is only half full and the lumber inside is prone to cracking, such as oak is, it would be necessary to cover half the collector on the roof. In addition, if the wood is to be used for exterior house walls where it’s protected from rain, a good average is 12% MC. They use the free energy of the sun, so they cost nothing to operate except for the small cost of electricity needed to run the fans. A moisture meter is a woodworker’s best insurance for solar-dried lumber to prevent cracking, warping, or splitting in the finished wood product. Insulation in the walls and floor helps the kiln retain heat, which helps speed the drying process. They are closed toward the end of the drying process to help maximize heat and get the wood down to the target 8 percent MC.
This not only means allowing for warmth to evaporate the moisture at a rate less likely to cause the wood stress and therefore split and crack later on, to also allow air flow around the piece.
I have read several books with numerous suggestions for home-made kilns, but have deferred to letting it dry naturally, that way I can get on with the fun bit of making the didgeridoos. After the majority of the moisture is out of the wood, which usually takes a week or two, go ahead and shut the vents to maximize the temperature.
Corrugated roofing manufacturers offer various solutions to this problem, such as wood strips cut to match the undulating roofline or strips of foam that conform to the corrugations.
Attach a wire to each nail with alligator clips and run them out a hole in the side of the kiln. I am happy to use wood up to 15% moisture content and have not encountered any difficulties. For example, placing a piece of wood in the loft is NOT an effective way to season wood as there is little air flow to take the moisture away and also the temperature fluctuations can do more harm than good. Although there are different solar designs on the market today, the Virginia Tech design is the kiln model considered the standard by which other kilns are built. The wood also becomes significantly lighter (as I found out when I was carrying unseasoned wood through a forest and my friend was carrying the seasoned timber!). Some, more traditional wood users frown upon this technique stating that the wood needs to season naturally and that kiln-dried wood some of its character. After the kiln is loaded, all that’s required is some minimal vent adjusting while the wood dries.
It is critical when kiln drying wood that the wood is heated evenly, as not doing so can cause misshaping during the shrinking process. During the day, the kiln heats up and the fan comes on to circulate hot air through the stack. You may find it’s easiest to simply leave the vents closed all the time for thick or hard-to-dry wood. Moisture is drawn from the wood into the air and is vented outside through the vents or leaks out naturally through the kiln’s joints and seams. The surface of the wood gets wet and cool, relieving any drying stresses that built up during the day.