Chapter 7: Decision Tree
So you have a bow stave—is it a split stave, a sapling (too small to split) or a board?
Split Staves
First thing—consider which part of the stave is most desireable—the sapwood, heartwood, or both. Feel free to ask me or post on r/bowyer if you’re not sure. If the sapwood is desirable (whitewoods such as hickory, ash, elm, hazel etc,) go with a natural back. If it’s the heartwood (osage, mulberry, locust,) chase a growth ring. And if it’s a combo of heartwood and sapwood (yew), chase a sapwood ring close to the heartwood (unless the sapwood is very shallow.) Finally if there’s damage to the back of the stave you may have to chase a growth ring. Note that for Yew chasing a growth ring isn’t always a realistic goal so you may have to allow small violations.
Natural Backs
The goal here is to end up with a pristine, unviolated back made up of the first underbark growth ring. If the bark is stuck (typical in the winter, fall) you’ll have to remove it. You can steam the stave or pour boiling water on the bark to get it to peel off, or remove it with a drawknife and scrapers. If the bark peels easily, just seal the back of the stave with dilute wood glue or wood sealer such as shellac, so that it doesn’t crack as it dries. If a major mistake is made while removing the bark, and the back of the bow is violated, either chase a growth ring, back the bow, or for certain species (hickory, elm) allow the violation at a slight risk.
Chasing a Growth Ring
There are 5 situations where I recommend chasing a growth ring.
- The heartwood is the most desirable part of the stave (chase a heartwood ring)
- A combo of heartwood and sapwood is most desireable (chase a sapwood ring close to the heartwood)
- The back of the stave is rotten, violated, or otherwise damaged.
- A mistake is made while removing the bark from a whitewood (some species will tolerate this violation more than others)
- In some flatsawn boards it may be possible to chase a growth ring.
Violated Back
Some woods like yew, hickory, and elm can tolerate much more violation than others. For these woods you can allow more mistakes on the back, or even purposefully choose a violated back as a pragmatic consideration. If possible, it’s usually better to chase a growth ring instead.
Saplings
For tension strong whitewood species (hickory, ash, elm, hazel etc) ignore the crown and choose a natural back. You may have to design the bow to be longer and narrower than usual so the sides of the bow don’t get too thin.
For relatively tension weak species (debatably osage, juniper) decrowning is an option—if you have the skill to decrown near-perfectly. Otherwise you may want to keep the crown and instead round the belly as in an English longbow. Or you can built the bow normally and simply design it longer and or wider, which is my preference.
Backing
Hard backings are usually a design decision made from the start, so they won’t fit into this decision tree. The same goes for sinew most of the time, however you can apply thin layers of sinew much like a soft backing.
The situations where I might recommend adding a soft backing are when a mistake was made chasing a growth ring or removing the bark, or when using a board that is almost unviolated but could use a slight tension safety boost. Personally I prefer to chase a growth ring or simply select a better board, but the option always exists. In my opinion the best practical advantage of backings is scratch protection, and I don’t like the idea of using them to rescue boards that would be otherwise dangerous.
Decrowning
See the section on saplings. Usually I don’t recommend decrowning, especially for woods that are already tension strong and can handle a high crown. Woods that are relatively tension weak such as osage (it’s not that tension weak it’s just very strong in compression) are frequently decrowned and then backed with either sinew or rawhide.
Board Staves
Choose a board with straight fibers all the way across the back. Avoid the issues in the diagram below. You can use any growth ring orientation, as long as the fibers on the back are unviolated. If you need to make a tiebreaker between two boards: choose one with denser wood and less porosity visible in the endgrain.
Certain flat sawn boards that would normally be rejected may be salvageable by chasing a growth ring.
That’s all for today!
Please let me know if you have any corrections, and if I’ve left you with any questions, find me on reddit on r/Bowyer or leave a comment on my YouTube video. This site is riddled with spam so comments here may take much longer to reach me and I may not see them at all.
May your arrows fly true,
Go make a bow!