Primitive Archer
Main Discussion Area => Bows => Topic started by: Dave 55 on June 03, 2009, 02:27:04 pm
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I picked up a yew stave and have marked out the profile on it ,but Ive been thinking ,it has about 1/2 inch sapwood that would make the limbs closer to the nocks mostly all sap wood,would it be desirable to thin the sap wood down to about 1/4 inch or should I leave it alone? This is the first time Ive worked with this wood,any help would be appreciated,Dave.
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I have made bows where the tips were almost all sap wood and they shot OK. The expert bowyers I have spoken to advise thinning the sapwood though. Some say it is not all thatimportant to follow the growth rings when doing so. Cutting down into grain (grain valleys) is not good but leaving grain standing poud (grain mountains) is apparently OK.
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The one I attempted I thined to less than 1/4". I am glad I did for the reason you mentioned. Thinning wasn't as hard as I thought it would be. But my yew was only 15-18 rpi. I bet with some real tight stuff that would be diffcult. I thined one ring at a time with a scraper.
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i have made bows both ways and both have their advantages. absolutely depends on the stave. sometimes its nice to remove the bark and sand the outer ring, sometimes its nice to file it flat.
I like the look of the final limb to be 50/50 sap/heart , this utilizes heartwoods strength in compression and sapwoods strength in compression. final tiller can be done through side tillering.
can we see a pic of the stave?
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Thanks for the information guys,Id like to show you a picture of the stave but I dont have a digital camera,time to get out of the stone age I guess.The staves is nice and straight ,arond 30 rings per inch with the sap wood having less,one cluster of about 3 or 4 pinknots,Dave.
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Any other thoughts?
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I would also advice you to thin the sapwood to around ¼". Yes, a bow can be made with yew sapwood only, but it is not desirable. The sapwood is softer, lighter, takes more set and has less structural value. You'll see that in a bow with ½" of sapwood, the bow will take more set than expected, and you'll need more wood (in volume) as compared to ¼" of sapwood only.
Thinning 30 rpi yew sapwood is not too difficult a task. It is okay to leave some spots with an extra growthring, or to go through the growthring one layer. Try to avoid it by all means, but damaging one growthring slightly is not as lethal as you may think.
BTW; with a deep-profiled ELB you can get away with a little more than ¼" of sapwood, while a wider flatbow requires a bit less than ¼" of sapwood.
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Dave,
You didn't specify which type of yew you have. I have made perfectly good bows without ever touching the sapwood, though more recently I have removed up to 8 layers to thin it down a bit. But it's also OK with some yew to completely remove the sapwood and use just heartwood - a lot of the dogma regarding the elasticity of the sapwood versus the compressability of the heartwood is just that - dogma. Depends on the yew.
Cheers, Dave
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Where there is a thin layer of sapwood IMO it is just as well to leave it undisturbed.
On an English bow it can run up to 50% thickness at the tips, between 25% or 33% at most in the working limb.
Depends on the quality of the wood.
I would not bother chasing a sapwood ring in close ringed yew, just follow the general line and make no radical departures.
Only on coarse ringed sapwood would I even try to chase a ring.
Rod.