Steaming A Bow Stave

There are very few nearly perfect bow staves. There are more nearly perfect bow staves and many many, more that would require the self- bowyer to accomplish something in order for them to be considered nearly perfect.

The cost of the nearly perfect stave is higher and the cost of the stave that needs adjustment is lower because of the need for the bowyer to accomplish this additional work. And there are other times when the shape of the stave requires adjustment in order for the wood to meet the bowyer’s vision. For instance the gull wing design of the Plains Indians of North America or a simple recurve.

Nature seldom accommodates man so man adjusts nature. In this case man bends wood. He heats the wood and then bends it. Direct application of heat can damage the wood fibers and even lead to scorching or turning the wood into firewood. The preferred alternative is using steam.

Early bowyers borrowed a technique for heat treatment from flintknappers. They buried the stave in the earth and lit a fire over it. If you want to try this method I would recommend using clean sand to line the burial pit. Dig the hole deep enough to bury the stave about 6 to 8 inches below the surface where you are going to burn your fire. Then lay in the stave on a bed of clean sand and soak the pit with water. Finish filling the pit and again soak the entire pit with water. Then light your fire. Keep the fire going all day. Experience will teach how long to burn the fire but it does take a few hours for the ground to be thoroughly heated.

When your determined time is finished, quickly remove the stave and bend it. Have heavy gloves on as the stave will be very hot and could burn your hands. If it is not hot it won’t bend.

Enough for primitive methods. A far easier and quicker method is to produce steam and use this to heat your stave. I use a steel five gallon can, a stove pipe and a propane crab cooker.

I use the crab cooker because it can heat the water quickly and create the steam I need without taking hours to do so. The steel 5 gallon gas can with a flexible steel spout actually increases the pressure on the steam as it is generated thus increasing the temperature of the steam (steam under pressure can become very very hot so don’t let it get on you)!! The pressure is not that great and is a consequence of the gas can opening through the flexible steel sput being restricted in size. Just add about 4 gallons of water, light the fire and your steam generator is ready to produce steam. Now, for the heating chamber.

I have found through experimentation that the layout of the heating chamber is important. I use 6 inch stove pipe and cap the ends. I use enough lengths of the pipe to accommodate the bow staves I am heating. 74 inches is typical. I support the pipe at a height that allows my steam generator to be placed below the pipe. You can use saw horses or build supports if you like. I then insulate the pipe and I prefer to use the aluminum foil backed bubble wrap insulation. Fiberglass would also work.

I then drill a hole that permits the gas can’s flexible steel nozzle to be inserted into the pipe. I also drill some small holes along the bottom of the horizontal pipe to allow steam condensate to drain. The steam will cool and condense into water. Just a little physics and that is that water can only be heated to a certain temperature and then it turns to steam. Steam can be heated to much higher temperature than water and this makes it an ideal medium for transferring heat from the fire to the wood of your stave. So you don’t want the condensed stem to accumulate in your heating chamber as it will restrict how hot your wood can get. Another tip is to place small pieces of wood along your pipe to keep your stave out of the condensate or water in the bottom of your pipe.

Light your fire and heat your wood. Again, experience will tell you how long to heat your wood before it become flexible enough to bend. Once steam is being generated I usuall try to heat the wood for an hour or so.

Once the wood is heated you have very little time before it cools so have your forms ready. I used to use the fork in a tree and applied pressure myself to the stave. As I gained experience I built wooden forms. I cut these from dimensional lumber in the shape that I sought. I used a band saw to achieve this shape. Recurves, gull wing designs, reflex-deflex, or easier stave straightening forms. On sharper recurves or siyahs I would use straps of steel on the outside of the curve to help in preventing splintering of the wood.

A rule of thumb to get you started is to bend your woo further than you have targeted by about fifty percent. For instance if you need to bend your stave four inches in order to get it straight, then bend it 6 inches and it should relax to a straight stave when removed from your form. I leave the stave in the form over night at least before removing it, and I wait two weeks before trying to tiller. In all cases experience will be your best teacher, but you need to try in order to learn. A final tip is to bend more than one stave at a time. Better mileage for your propane when you do so and we know that no one can make just one bow.