Chrysalis in Birch.... can it be saved?

[Prarie Bowyer]

Hey guys.  Working a  little light weight bow (now) in birch.  Flat bow with ELB proportions.  I got in a rusn and the belly of one limb developed those little compression cracks at a hinge point.  Will those go all the way through?  I tried to sand it out and drop the weight but they seem to be coming back. 

i considered backing the belly somehow to get a shootable bow out of it.  Any thoughts?

It's 70" long.  No minimum draw weight requirement.

[Del the cat]

Nope, chrysals go much deeper than you'd think (I've seen 'em go 4mm deep)
I think an ELB profile is too deep for birch, needs to be wider & thinner.
Maybe heat treating beforehand would have helped, but I think once you have chrysals you're doomed.
Del

[Hunter Van Winkle]

flat bow with ELB dimensions?

"Backing" the belly?

Are you trolling us? 

[Baldmoose]

I would suggest just doing some sort of binding on the damages section... Not the greatest for appearance but it will work.

[Jim Davis]

I second Del's conclusion. The deep belly of an ELB design only works on woods that are stronger in compression than tension, such as yew and red cedar.

Birch is several times stronger in tension. Most folks making bows never consider the difference in tension and compression strengths. They should.

Jim Davis

[PEARL DRUMS]

I thinks its marginal as bow wood at best and maybe the worst canidate for an ELB. Scrap it and try a 2 1/2" x 68" flatbow next time and it may be okay.

[RobWiden]

I agree with Del and PD. Where I live it's mostly softwoods, birch is the most readily available hardwood so what I learned on. Make them wide and long and no dips or humps on the belly. They'll chrysal at the first sneeze.    Rob

[Baldmoose]

http://www.primitivearcher.com/smf/index.php/topic,30474.msg403685.html#msg403685  i would take a look at this bow...

[mikekeswick]

I second Del's conclusion. The deep belly of an ELB design only works on woods that are stronger in compression than tension, such as yew and red cedar.

Birch is several times stronger in tension. Most folks making bows never consider the difference in tension and compression strengths. They should.

Jim Davis

Absolutely right on.


I've made a 55lb silver birch bow (Betula pendula) it was 2 1/4 inch wide and about 68 intn. Birch is a good wood for backings in itself.

[Marc St Louis]

There seems to be a bit of confusion as to what is the cause of chrysals.  The cause is how elastic a wood is and not its tension/compression strength.  Black Cherry is stronger in compression than it is in tension but will chrysal if you look at it sideways because it is low in elasticity. 

Birch is a good bow wood but it is a bit low in elasticity.  You can get chrysals with Birch even with a wide flat belly if the bow is too short for the draw length.  It is not suited to a D section because it's low in elasticity but if made long enough you could get away with it. 

Heat-treating is a great tool but it won't help a wood that is low in elasticity.

[Prarie Bowyer]

Thanks guys.  I ripped the backing off (bmaboo) and used it on another bow.  Another odd ball.  Recurved ELB quad lam.  Seems to be working so far.

Use dhte rest fo the birch for taper grinding sleds.

[crooketarrow]

  CHRYSALS are crushed wood cells they can be repaired.  WHITE WOODS the cells crush easer. If there not to bad and you can tiller past them and sinew back to the weight you want.