QUICK-DRYING STAVES
Fell and split a tree into staves. Take one of these and pull or work the bark free. Floortiller the stave just as if making a finished bow, but leave it full width for its entire length--this to prevent lateral warping as it dries. The more uniform in thickness its crossection the less it will want to warp also.
Tiller until the green bow will bend 3-inches or so when pushed with about 15lb of force against the grip (per 50lb bow). This will not cause set, but will tell you how far the stave can be thinned. This 15lb will about double when the stave is dry, leaving plenty of stiffness for finish tillering. Wood stiffens by about 6% per each 1% drop in moisture content
Rest the stave horizontally, with spacers of some sort beneath it, allowing air to move freely over all surfaces.. Place the stave in air which is as close to 40% relative humidity (RH) as possible. In damp areas this may be high up in the kitchen, or near the floor of the basement in dry areas. A humidity meter will locate the best location. The warmer the air the faster the stave will dry. A fan shining evenly over the stave, or any gentle flow of air, will shorten drying time considerably, just as with clothes on a line.
Under unusually fast drying conditions the stave may try to warp gently. If so, tie it down on a 2 by 4 or such, with spacers beneath it. Or place it in cooler or damper air.
A side benefit of quick-drying is that the stave is reduced while green, and green wood is far easier to work. If you have the time reduce all staves to near bow thickness. Or place unworked staves where they can dry slowly enough for their girth. A floortillered stave will dry as much in two days as a bark-on split stave may dry in many months, even years.
Its difficult for wood to decay once under 30% MC. A floortillered green stave will drop below 20% in as short as one day. Wood cant decay at all once below 20% MC. This is one reason to debark and floor tiller staves of wood which are not decay resistant. Especially in warm, moist climates.
You may prefer an unworked, character-full, natural back--a nice look on a primitive bow--but a coating applied to the back to slow drying must be worked off, taking the pristine surface with it. Quick-drying solves this problem also.
RELATIVE HUMIDITY (RH) DETERMINES MOISTURE CONTENT Wood left in air of a given RH will eventually reach the moisture content given in the chart, below. Thin wood reaches this point quickly, thicker wood reaches in more slowly.
TEMPERATURE Raising air temperature will shorten the time needed for wood to reach its RH-determined target MC.
DRYING TIME Once floortillered and placed at room temperature and in moderate 50%RH air, a floortillered stave will reach 10.5%MC in about ten days, about 9% a few days later.. 10.5% is usually close enough for finish tillering. In air of 40%RH a floortillered stave will reach 9% in about ten days, 8% a few days later.
A deep, narrow design, such as an English longbow, will take up to twice as long to dry. Leave such designs as wide as you can for their entire length. Narrow staves are more prone to lateral warping.
YOUR MOISTURE CONTENT Dry a stave to a moisture content matching the humidity in which the bow will be stored. Otherwise it will gain or loose weight over time as it adjusts to its home RH.
EQUAL MOISTURE CONTENT At a given relative humidity all woods dry to the same moisture content. No higher, no lower.
Relative humidity at room temperature is given on the left, equilibrium moisture content on the right: Numbers vary only slightly at higher/lower temps. Its convenient to post this chart on your shop wall. A handy key to remember is that 55%RH yields 10%mc.
30% = 5%
43% = 8%
55% = 10%
65% = 12%
75% = 14%
DRYING WITH A SCALE Two of the most valuable tools a bowmaker can own are a humidity meter and a low-weight scale. If you know the airs relative humidity, and consult the above chart, you can know how dry your stave will eventually be. But you cant know exactly WHEN. A scale will tell you this: Weight the drying stave every day or so with a five-pound or lighter scale. For convenience write each days weight on the belly. When the stave has lost NO weight for one-third of the time its been drying you will know the stave is dry. Scale-monitoring is only effective for staves of near floortillered thickness. Thicker wood dries too slowly for weight changes to resister accurately. If only twice as thick the eventual belly may not be fully dry for two or three months. If twice thick again it can easily need a year.
The scales dial should be large enough to clearly show the needles movement between ounce marks. The last few percentage points of moisture content take two-thirds of total drying time.
An average floor-tillered stave will weigh up to about 50oz if dripping-wet green. Too heavy for a two-pound scale. But it neednt be weighed for the first few days, by which time it will have fallen below two-pounds. To weight it green put one end on the scale, support the other parallel to the ground, and the scale will display half the staves weight.
PRIMITIVE? Primitive bowmakers didnt use scales or humidity meters. But they didnt live in artificially heated house, with resulting unknown and sometimes dangerously low relative humidity. And they inherited generations-old techniques which told them just how to dry the various woods they used. We have to learn all this in a small part of a lifetime.
FORCED DRYING
In a drying box wood can be taken dripping green from the tree to finish tillered in as few as five days. At 100f and 40% relative humidity a floortillered stave will reach 10% moisture content in about five days. Its heading for just under 8%, which lets it reach 10% more quickly. It will reach 8% in a couple of more days, if allowed. Again, higher temperature shortens drying time, relative humidity determines final moisture content.
WHY A DRYING BOX? Drying boxes are convenient if you need a dry stave during your high-humidity season. Or if your dry-seasons RH is just high enough so that it takes a very long time for a staves MC to creep down to tolerable levels.
CONTROLING HUMIDITY A humidity meter will let you maintain an optimum drying RH of about 40%, and an optimum RH of 50% for storing dried staves and finished bows. Do this by opening vents in the early stages of drying, letting damp air out. And later, by closing vents, and adding wet rags or green wood if needed to keep humidity from falling much below 40%.
Moisture escaping from drying wood raises RH in the box. On the other hand heating the air lowers RH. Relative humidity can easily drop below 30%, taking the wood below, and possibly well below, 6%MC, where it becomes dangerously brittle.
High heat and very low RH can cause even thin wood to occasionally check and warp. You must know the RH of the air to know the moisture contend your stave is heading for. Drying wood in a drying box without a humidity meter inside is like driving a car without a steering wheel.
A DRYING BOX The heat source can be solar, light bulbs, a crock pot, or an electric heater. Light bulbs work well for small to medium-sized boxes. Often an electric heaters thermostat wont allow plus-90f temperatures. A cheap no-thermostat heater, with low, medium, and high settings, will reach desired temperature in a larger box. If the boxs floor is combustible you might set the heater on a steel plate or large cookie pan.
One-inch vent holes should be evenly spaced every several inches in or near the floor and ceiling. Only the top holes need be adjustable, and this can be done as simply as placing moveable slats over them. A small fan inside the box is valuable--look how much faster clothes dry on a windy day. And circulating air promotes uniform drying. Point the fan away from the wood.
In open air a floortillered green stave looses about 25% of its weight in one day, 35% in three days. Free water leaves the stave so quickly during this phase there is really no point in putting it in the drying box. In room-temperature, 50%RH air, the stave will drop from dripping wet to about 14% in less than a week. At 50%RH the wood is aiming for just under 10%MC. It will get down to about 11% in another few days. That last 1% can take quite awhile. This 1% can be ignored, or the stave can be placed in drier air A drying box is most useful for going from 15%MC or so to dry. Largely because you can lower the target moisture content. For example, if aiming for 10%MC, reachable at 55%RH, adjust RH to 40% and the wood will think its reaching for just under 8% and will run down to 10% more quickly.
IF AIR IS HOT AND DAMP outside the box then box temperature must be elevated higher than 100f to lower internal RH. If you cant reach low enough RH you might consider using a dehumidifier. Or dry staves during the least humid time of the year, seal them well, and store them in the lowest RH air you can find.
IF AIR IS COLD outside the box then heat inside the box will cause box RH to drop far below outside RH. Once the bulk of a staves water has departed, box RH can then fall dangerously low, even into the teens. Vents, wet rags or fresh green wood are easy remedies. Percentage-wise, more wood is wrecked in drying boxes than any other way. All avoidable with a $15 humidity meter.
A LOW-BUDGET BOX One corner of a basement can be made into an effective wood drying chamber for just a couple of dollars. The floor, ceiling and two walls of the basement can be the floor, ceiling and two walls of your chamber. Just tape or staple plastic from ceiling to floor for the other two walls. From eye-hooks in the ceiling hang wires to trapeze-like cross pieces, one, two or three deep. A 3 by 7-foot space with three levels of hangers will hold about 30 flootillered staves. Place the hangers about 10, 20, and 30 from the ceiling. Put a space heater or dehumidifier on the floor.
A STAY-WET BOX Sometimes you need to slow the drying process. Some woods will check or crack unless dried very slowly, plumb for example. If natural conditions would dry the stave too quickly, and if youd like to keep the staves back pristine and uncoated, raise the humidity in the box to 90% or so, then slowly decrease this in safe increments over time. Even osage can be debarked and dried without its sapwood checking. Drying time will be slow, but it will be as fast as safely possible.
CONVENTIONAL DRYING
Bow-thin wood dries quickly and safely. But thick wood must dry slowly or it can suffer several kinds of damage. Ironically, air-dried staves typically show more checking, cracking, twisting and compression damage than lumber staves. But knowing just a handful of drying techniques will let you avoid such problems. Essentially, surface wood must be prevented from drying much faster than inner wood. Safe drying techniques all have this as a goal.
SIZE The thicker the wood the slower it must dry. The higher the temperature or the lower the humidity or the faster air moves over the wood, the faster a given thickness of wood will dry.
DRYING TIME A stave can season for twenty years and still be too wet, if local RH is too high. A stave drying in 65% RH, for example, could not fall below 12%MC in a thousand years. But worse, it can take a very long time to creep down through the last few percentage points of MC to that 12% mark. It might be at 14% when tillered, and take far too much set. Wood aiming for 10% and reaching 12% is not as bad off as wood aiming for 12% and reaching 14%. When stuck with high RH its more important to take the extra time to let your wood get as close to equilibrium as possibly before tillering.
BARK is almost waterproof. Typical year-old, sealed, split staves will be about as damp under the bark as quick-dried staves after two days. Floortiller thick staves ten days or so before making a bow, as per Quick-Drying, above, and they will be ready.
LOW RH OR HIGH HEAT OR STONG WIND can wreck thick wood. Unless you reduce wood to near bow thickness, or coat it heavily, you might as well leave the bark on. Coat the ends, and the sides too if conditions are severe.
IF WOOD IS CHECKING for any reason, act immediately. Wet it well. or seal it well, or, lower the temperature, or get it into higher RH air until later stages of drying, or some mix of these. Let the inside catch up with outside Wet rags placed in a drying box or other small enclosed spaces raise humidity quickly. Reducing the wood to bow thickness will prevent future checking.
CURING KERFS prevent staves from warping, prevent full-diameter logs from checking, and causes a log to split true and easily. Make full-length straight cuts with a Skill saw where you would otherwise split the log into staves. Especially useful for drying wood with the bark on. .. get more staves per tree cause can cut closer to width of finished bownor splitting damage
HIDDEN CHECKS Quickly-dried surface wood begins to shrink and check. When later split and reduced the inner wood then dries and shrinks also, causing the surface checks to close. Later, if dried further and quickly, they can open up again.
CASE HARDENING An old woodworkers misnomer. Improperly kiln-dried wood is drier on the outside than the inside, creating uneven stresses. If such a board is resawn the sections warp as they pass the blade. Nowadays, during and after kiln drying, humidity is raised long enough for uneven forces to equalize. This is seen less often in air dried wood because humidity likely naturally rises and falls during the longer drying process.
FORCING A STAVE INTO REFLEX WHILE DRYING The stave is just pretending. Most of this reflex will pull out when drawn, especially in main working portions of the limbs. Staves that dry naturally reflexed do better, as do staves which are steamed into reflex. Steam-bending temperatures let cellulose plasticize somewhat, assuming a true altered position. But steamed reflexes also surrender somewhat.
DARK WOOD Heartwoods which are especially full of extractives may be slower to dry. And would be slower to gain moisture. Black walnut, osage, locust and redcedar, for example.
USED WOOD Any time you dont know the full history of a board or split stave you have to assume it may have been mistreated. It may have spent years drying in an attic, or resting on a damp floor. A simple wood test is useful here
REHYDRATING WOOD If a stave is too dry reduce it to near-bow thickness and place it in destination RH air for a few days. Wood is stiffer when dry, so dont determine proper limb thickness based of floortiller resistance while too dry.
MOISTURE METERS Electrical-resistance, prong-type moisture meters cost about a days pay, are convenient to use, and are accurate enough if used with care and insight. Different woods yield different meter readings, and supplied correcting charts are incomplete and imperfect. Readings from same-species staves of equal MC can be of by a few points, possibly due to minerals in the soil during growth, or differences in density.
But the greatest error comes from uneven dampness on and in the stave. If just the very surface is moist the meter reads high. If the surface is bone dry but underwood is damp the reading will he high. It might read 10% while the surface, the wood that does the work, might be 5%, causing the bow to break There are dozens of such scenarios in which the stave and meter outsmart us. Common sense is the best protection here. A more certain way to know the moisture content of wood is to know the relative humidity of the air its in.
WINTER DRYING Even if initially at 100% RH, once this air is heated to room or drying -box temperatures its RH can drop into the teens. No matter what the outside humidity, without a humidity meter beside the stave or bow you cant know if its dangerously dry.
VERY DRY WOOD If forced to use very dry wood treat it as lighter, weaker wood. For equal safety make the limbs wider (therefor thinner, more bendible) or longer (needing less bend).
VERY WET WOOD If made wider or longer, to counter the set expected of by damp wood, increased mass tends to counters any gain.
KEEPING A BOW DRY The moisture content of an unsealed bow can rise or fall many points in just a few days. One wood or another might absorb moisture faster or slower when exposed to higher or lower RH, but a reasonable sealer will protect against moisture content spikes for several days, until safely back in the lodge. If required to be in very damp air for day or weeks you can protect your bow from large, permanent string follow: When not in actual use keep the bow in a tube or sealed plastic sock containing packets of Damp-Be-Gone, or such. Available at larger hardware stores. This is a granular material which can absorb more than its weight in water. Later it can be heated and reused. An old sock is a handy granule container
HUMIDITY METERS are not highly accurate, typically having a several-point margin of error. Sling psychrometers, costing $50 and up, are the most accurate and even these can be off a couple of points. Still, using a meter its far better than guessing.
Humidity meters are inexpensive--as low as ten-dollars. Buy your meters where many are displayed for sale. Some will read high, some low, and in the middle many will read within a point of each other. Buy from that group. Note, if when placed outside, it comports with announced local humidity. If consistently off by several points, tape a new set of numbers over the dial. Try to do his calibrating at 50% relative humidity. These meters take many minutes to react to changes in humidity.
In time youll develop a sense of how fast water moves in and out of wood of different dimensions in air of different dampness and temperature. A humidity meter alone will then let you know with good-enough accuracy the moisture content of you staves, blanks, and bows.
Jeff Schmidt once suggested that a strand of horsehair or a long strand of sinew could be rigged to a needle and serve as a humidity meter. Sinew might do better--it shrinks up to 4% of length when drying.
Its good to keep a humidity meter wherever you store or dry wood, or finished bows.
Fell and split a tree into staves. Take one of these and pull or work the bark free. Floortiller the stave just as if making a finished bow, but leave it full width for its entire length--this to prevent lateral warping as it dries. The more uniform in thickness its crossection the less it will want to warp also.
Tiller until the green bow will bend 3-inches or so when pushed with about 15lb of force against the grip (per 50lb bow). This will not cause set, but will tell you how far the stave can be thinned. This 15lb will about double when the stave is dry, leaving plenty of stiffness for finish tillering. Wood stiffens by about 6% per each 1% drop in moisture content
Rest the stave horizontally, with spacers of some sort beneath it, allowing air to move freely over all surfaces.. Place the stave in air which is as close to 40% relative humidity (RH) as possible. In damp areas this may be high up in the kitchen, or near the floor of the basement in dry areas. A humidity meter will locate the best location. The warmer the air the faster the stave will dry. A fan shining evenly over the stave, or any gentle flow of air, will shorten drying time considerably, just as with clothes on a line.
Under unusually fast drying conditions the stave may try to warp gently. If so, tie it down on a 2 by 4 or such, with spacers beneath it. Or place it in cooler or damper air.
A side benefit of quick-drying is that the stave is reduced while green, and green wood is far easier to work. If you have the time reduce all staves to near bow thickness. Or place unworked staves where they can dry slowly enough for their girth. A floortillered stave will dry as much in two days as a bark-on split stave may dry in many months, even years.
Its difficult for wood to decay once under 30% MC. A floortillered green stave will drop below 20% in as short as one day. Wood cant decay at all once below 20% MC. This is one reason to debark and floor tiller staves of wood which are not decay resistant. Especially in warm, moist climates.
You may prefer an unworked, character-full, natural back--a nice look on a primitive bow--but a coating applied to the back to slow drying must be worked off, taking the pristine surface with it. Quick-drying solves this problem also.
RELATIVE HUMIDITY (RH) DETERMINES MOISTURE CONTENT Wood left in air of a given RH will eventually reach the moisture content given in the chart, below. Thin wood reaches this point quickly, thicker wood reaches in more slowly.
TEMPERATURE Raising air temperature will shorten the time needed for wood to reach its RH-determined target MC.
DRYING TIME Once floortillered and placed at room temperature and in moderate 50%RH air, a floortillered stave will reach 10.5%MC in about ten days, about 9% a few days later.. 10.5% is usually close enough for finish tillering. In air of 40%RH a floortillered stave will reach 9% in about ten days, 8% a few days later.
A deep, narrow design, such as an English longbow, will take up to twice as long to dry. Leave such designs as wide as you can for their entire length. Narrow staves are more prone to lateral warping.
YOUR MOISTURE CONTENT Dry a stave to a moisture content matching the humidity in which the bow will be stored. Otherwise it will gain or loose weight over time as it adjusts to its home RH.
EQUAL MOISTURE CONTENT At a given relative humidity all woods dry to the same moisture content. No higher, no lower.
Relative humidity at room temperature is given on the left, equilibrium moisture content on the right: Numbers vary only slightly at higher/lower temps. Its convenient to post this chart on your shop wall. A handy key to remember is that 55%RH yields 10%mc.
30% = 5%
43% = 8%
55% = 10%
65% = 12%
75% = 14%
DRYING WITH A SCALE Two of the most valuable tools a bowmaker can own are a humidity meter and a low-weight scale. If you know the airs relative humidity, and consult the above chart, you can know how dry your stave will eventually be. But you cant know exactly WHEN. A scale will tell you this: Weight the drying stave every day or so with a five-pound or lighter scale. For convenience write each days weight on the belly. When the stave has lost NO weight for one-third of the time its been drying you will know the stave is dry. Scale-monitoring is only effective for staves of near floortillered thickness. Thicker wood dries too slowly for weight changes to resister accurately. If only twice as thick the eventual belly may not be fully dry for two or three months. If twice thick again it can easily need a year.
The scales dial should be large enough to clearly show the needles movement between ounce marks. The last few percentage points of moisture content take two-thirds of total drying time.
An average floor-tillered stave will weigh up to about 50oz if dripping-wet green. Too heavy for a two-pound scale. But it neednt be weighed for the first few days, by which time it will have fallen below two-pounds. To weight it green put one end on the scale, support the other parallel to the ground, and the scale will display half the staves weight.
PRIMITIVE? Primitive bowmakers didnt use scales or humidity meters. But they didnt live in artificially heated house, with resulting unknown and sometimes dangerously low relative humidity. And they inherited generations-old techniques which told them just how to dry the various woods they used. We have to learn all this in a small part of a lifetime.
FORCED DRYING
In a drying box wood can be taken dripping green from the tree to finish tillered in as few as five days. At 100f and 40% relative humidity a floortillered stave will reach 10% moisture content in about five days. Its heading for just under 8%, which lets it reach 10% more quickly. It will reach 8% in a couple of more days, if allowed. Again, higher temperature shortens drying time, relative humidity determines final moisture content.
WHY A DRYING BOX? Drying boxes are convenient if you need a dry stave during your high-humidity season. Or if your dry-seasons RH is just high enough so that it takes a very long time for a staves MC to creep down to tolerable levels.
CONTROLING HUMIDITY A humidity meter will let you maintain an optimum drying RH of about 40%, and an optimum RH of 50% for storing dried staves and finished bows. Do this by opening vents in the early stages of drying, letting damp air out. And later, by closing vents, and adding wet rags or green wood if needed to keep humidity from falling much below 40%.
Moisture escaping from drying wood raises RH in the box. On the other hand heating the air lowers RH. Relative humidity can easily drop below 30%, taking the wood below, and possibly well below, 6%MC, where it becomes dangerously brittle.
High heat and very low RH can cause even thin wood to occasionally check and warp. You must know the RH of the air to know the moisture contend your stave is heading for. Drying wood in a drying box without a humidity meter inside is like driving a car without a steering wheel.
A DRYING BOX The heat source can be solar, light bulbs, a crock pot, or an electric heater. Light bulbs work well for small to medium-sized boxes. Often an electric heaters thermostat wont allow plus-90f temperatures. A cheap no-thermostat heater, with low, medium, and high settings, will reach desired temperature in a larger box. If the boxs floor is combustible you might set the heater on a steel plate or large cookie pan.
One-inch vent holes should be evenly spaced every several inches in or near the floor and ceiling. Only the top holes need be adjustable, and this can be done as simply as placing moveable slats over them. A small fan inside the box is valuable--look how much faster clothes dry on a windy day. And circulating air promotes uniform drying. Point the fan away from the wood.
In open air a floortillered green stave looses about 25% of its weight in one day, 35% in three days. Free water leaves the stave so quickly during this phase there is really no point in putting it in the drying box. In room-temperature, 50%RH air, the stave will drop from dripping wet to about 14% in less than a week. At 50%RH the wood is aiming for just under 10%MC. It will get down to about 11% in another few days. That last 1% can take quite awhile. This 1% can be ignored, or the stave can be placed in drier air A drying box is most useful for going from 15%MC or so to dry. Largely because you can lower the target moisture content. For example, if aiming for 10%MC, reachable at 55%RH, adjust RH to 40% and the wood will think its reaching for just under 8% and will run down to 10% more quickly.
IF AIR IS HOT AND DAMP outside the box then box temperature must be elevated higher than 100f to lower internal RH. If you cant reach low enough RH you might consider using a dehumidifier. Or dry staves during the least humid time of the year, seal them well, and store them in the lowest RH air you can find.
IF AIR IS COLD outside the box then heat inside the box will cause box RH to drop far below outside RH. Once the bulk of a staves water has departed, box RH can then fall dangerously low, even into the teens. Vents, wet rags or fresh green wood are easy remedies. Percentage-wise, more wood is wrecked in drying boxes than any other way. All avoidable with a $15 humidity meter.
A LOW-BUDGET BOX One corner of a basement can be made into an effective wood drying chamber for just a couple of dollars. The floor, ceiling and two walls of the basement can be the floor, ceiling and two walls of your chamber. Just tape or staple plastic from ceiling to floor for the other two walls. From eye-hooks in the ceiling hang wires to trapeze-like cross pieces, one, two or three deep. A 3 by 7-foot space with three levels of hangers will hold about 30 flootillered staves. Place the hangers about 10, 20, and 30 from the ceiling. Put a space heater or dehumidifier on the floor.
A STAY-WET BOX Sometimes you need to slow the drying process. Some woods will check or crack unless dried very slowly, plumb for example. If natural conditions would dry the stave too quickly, and if youd like to keep the staves back pristine and uncoated, raise the humidity in the box to 90% or so, then slowly decrease this in safe increments over time. Even osage can be debarked and dried without its sapwood checking. Drying time will be slow, but it will be as fast as safely possible.
CONVENTIONAL DRYING
Bow-thin wood dries quickly and safely. But thick wood must dry slowly or it can suffer several kinds of damage. Ironically, air-dried staves typically show more checking, cracking, twisting and compression damage than lumber staves. But knowing just a handful of drying techniques will let you avoid such problems. Essentially, surface wood must be prevented from drying much faster than inner wood. Safe drying techniques all have this as a goal.
SIZE The thicker the wood the slower it must dry. The higher the temperature or the lower the humidity or the faster air moves over the wood, the faster a given thickness of wood will dry.
DRYING TIME A stave can season for twenty years and still be too wet, if local RH is too high. A stave drying in 65% RH, for example, could not fall below 12%MC in a thousand years. But worse, it can take a very long time to creep down through the last few percentage points of MC to that 12% mark. It might be at 14% when tillered, and take far too much set. Wood aiming for 10% and reaching 12% is not as bad off as wood aiming for 12% and reaching 14%. When stuck with high RH its more important to take the extra time to let your wood get as close to equilibrium as possibly before tillering.
BARK is almost waterproof. Typical year-old, sealed, split staves will be about as damp under the bark as quick-dried staves after two days. Floortiller thick staves ten days or so before making a bow, as per Quick-Drying, above, and they will be ready.
LOW RH OR HIGH HEAT OR STONG WIND can wreck thick wood. Unless you reduce wood to near bow thickness, or coat it heavily, you might as well leave the bark on. Coat the ends, and the sides too if conditions are severe.
IF WOOD IS CHECKING for any reason, act immediately. Wet it well. or seal it well, or, lower the temperature, or get it into higher RH air until later stages of drying, or some mix of these. Let the inside catch up with outside Wet rags placed in a drying box or other small enclosed spaces raise humidity quickly. Reducing the wood to bow thickness will prevent future checking.
CURING KERFS prevent staves from warping, prevent full-diameter logs from checking, and causes a log to split true and easily. Make full-length straight cuts with a Skill saw where you would otherwise split the log into staves. Especially useful for drying wood with the bark on. .. get more staves per tree cause can cut closer to width of finished bownor splitting damage
HIDDEN CHECKS Quickly-dried surface wood begins to shrink and check. When later split and reduced the inner wood then dries and shrinks also, causing the surface checks to close. Later, if dried further and quickly, they can open up again.
CASE HARDENING An old woodworkers misnomer. Improperly kiln-dried wood is drier on the outside than the inside, creating uneven stresses. If such a board is resawn the sections warp as they pass the blade. Nowadays, during and after kiln drying, humidity is raised long enough for uneven forces to equalize. This is seen less often in air dried wood because humidity likely naturally rises and falls during the longer drying process.
FORCING A STAVE INTO REFLEX WHILE DRYING The stave is just pretending. Most of this reflex will pull out when drawn, especially in main working portions of the limbs. Staves that dry naturally reflexed do better, as do staves which are steamed into reflex. Steam-bending temperatures let cellulose plasticize somewhat, assuming a true altered position. But steamed reflexes also surrender somewhat.
DARK WOOD Heartwoods which are especially full of extractives may be slower to dry. And would be slower to gain moisture. Black walnut, osage, locust and redcedar, for example.
USED WOOD Any time you dont know the full history of a board or split stave you have to assume it may have been mistreated. It may have spent years drying in an attic, or resting on a damp floor. A simple wood test is useful here
REHYDRATING WOOD If a stave is too dry reduce it to near-bow thickness and place it in destination RH air for a few days. Wood is stiffer when dry, so dont determine proper limb thickness based of floortiller resistance while too dry.
MOISTURE METERS Electrical-resistance, prong-type moisture meters cost about a days pay, are convenient to use, and are accurate enough if used with care and insight. Different woods yield different meter readings, and supplied correcting charts are incomplete and imperfect. Readings from same-species staves of equal MC can be of by a few points, possibly due to minerals in the soil during growth, or differences in density.
But the greatest error comes from uneven dampness on and in the stave. If just the very surface is moist the meter reads high. If the surface is bone dry but underwood is damp the reading will he high. It might read 10% while the surface, the wood that does the work, might be 5%, causing the bow to break There are dozens of such scenarios in which the stave and meter outsmart us. Common sense is the best protection here. A more certain way to know the moisture content of wood is to know the relative humidity of the air its in.
WINTER DRYING Even if initially at 100% RH, once this air is heated to room or drying -box temperatures its RH can drop into the teens. No matter what the outside humidity, without a humidity meter beside the stave or bow you cant know if its dangerously dry.
VERY DRY WOOD If forced to use very dry wood treat it as lighter, weaker wood. For equal safety make the limbs wider (therefor thinner, more bendible) or longer (needing less bend).
VERY WET WOOD If made wider or longer, to counter the set expected of by damp wood, increased mass tends to counters any gain.
KEEPING A BOW DRY The moisture content of an unsealed bow can rise or fall many points in just a few days. One wood or another might absorb moisture faster or slower when exposed to higher or lower RH, but a reasonable sealer will protect against moisture content spikes for several days, until safely back in the lodge. If required to be in very damp air for day or weeks you can protect your bow from large, permanent string follow: When not in actual use keep the bow in a tube or sealed plastic sock containing packets of Damp-Be-Gone, or such. Available at larger hardware stores. This is a granular material which can absorb more than its weight in water. Later it can be heated and reused. An old sock is a handy granule container
HUMIDITY METERS are not highly accurate, typically having a several-point margin of error. Sling psychrometers, costing $50 and up, are the most accurate and even these can be off a couple of points. Still, using a meter its far better than guessing.
Humidity meters are inexpensive--as low as ten-dollars. Buy your meters where many are displayed for sale. Some will read high, some low, and in the middle many will read within a point of each other. Buy from that group. Note, if when placed outside, it comports with announced local humidity. If consistently off by several points, tape a new set of numbers over the dial. Try to do his calibrating at 50% relative humidity. These meters take many minutes to react to changes in humidity.
In time youll develop a sense of how fast water moves in and out of wood of different dimensions in air of different dampness and temperature. A humidity meter alone will then let you know with good-enough accuracy the moisture content of you staves, blanks, and bows.
Jeff Schmidt once suggested that a strand of horsehair or a long strand of sinew could be rigged to a needle and serve as a humidity meter. Sinew might do better--it shrinks up to 4% of length when drying.
Its good to keep a humidity meter wherever you store or dry wood, or finished bows.
