Primitive Archer
Main Discussion Area => Bows => Topic started by: WindhoverMark on November 27, 2022, 04:38:41 pm
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Been lurking for a while now and this is going to be my first post. Thanks for all the help you have already provided. This forum is an incredible resource for a beginning bowyer.
I've been working on this hackberry stave for a couple weeks now. 66 inches, static handle, has a fair amount of character including a bit of natural deflex on both limbs. I've gotten it pretty much to final tiller; ~45lbs at 28". I was shooting it over the weekend and noticed that a chrysal has formed in the upper fade.
(https://i.imgur.com/Xf1ttrF.jpeg)
I understand that localized chrysals are a sign that there is too much strain/bend in one area, but the fades aren't really bending. Anywhere else on the limb I would scrap wood from either side of the chrysal to try and distribute the strain more evenly across a larger protion of limb. but in this case I can really only remove wood north of the chrysal. As I type this I realize that I could remove wood below the fade if I am willing to convert the bow to a bendy handle, which is an acceptable answer.
So here are my questions... Can I fix this chrysal, or do I just give up and move on to my next stave? If so, how? And once fixed, how do I prevent it from coming back?
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I would really like to see a picture of it strung up and full draw, kind of odd place for a Christal. Also did you try and add reflex or take out deflex at the handle, looks like it had a lot of heat there. :)
Pappy
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the grain shows that part is thin
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That doesn't look like a compression chrysal/fret. It looks more like a tension failure. Did you try to heat it and reflex it there?
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I think Brad may be onto something there. The shape of your grain looks thinned out in the area of the “stress fracture”. I agree with dances with squirrels too that it looks more like a tension failure. This could be a result of pulling beyond intended weight early on in tiller or over drawing bow at poundage. A few solutions could perhaps be to even it out a bit as the belly seems a bit week you could trap the back of this bow a bit to even up the tension with the belly. You may loose a little poundage though. Other thing is you could fill this area with super thin ca glue and even up that belly where it thins out and Match other side and see where you are on the tiller. It’s hard to know until we see the bow on the tiller tree being bent. If you have too much inner bend happening it may have hinged a bit early on too there on that week spot. So many possibilities. We need to see the bow on a tiller tree bending. Keep us posted.
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When I blow the photo up larger it looks like maybe a crack running with the grain or the right edge, and smaller chrysalis below and left of the larger one. I could be wrong though, but if so there might be more going on than we can see.
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I think Squirrels is right
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I'll post some more comprehensive pictures of the tiller later this afternoon.
The stave has some interesting kinks to it (for my experience level). I think that's what you are seeing in the grain. My calipers measure a consistent taper through the area. But maybe this is an example of me not following the flow of the grain?
A tension failure is possible. I did a couple heat corrections in that area. There is/was a natural deflex about 3in up from the failure point on the limb. I first attempted to steam the area and bend it over my knee when it was at floor tiller stage. That was moderately successful, leaving a small bit of deflex behind. I left it for a few days and then did some long string work before trying to get the last of it out, this time using a heatgun and a weight on the tip. The reason I assumed chrysal was that it didn't become visible until after I had a put a few dozen shots through it, plus it's on the belly...
Thank you all for your help.
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I feel pretty sure it's a tension failure then. You likely overstressed it and/or it wasn't hot enough when you attempted the correction.
I don't do the 'over the knee' thing. I can't sufficiently gage what I'm doing, or hold it still and precisely where I want it until it's cool throughout.
It's all good though... all part of the learning process... learning how far we can push it... and when not to.
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Sorry I forgot to post photo of what I saw.
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Agree that big dark failure is a tension issue. Fill it with epoxy and you are good to go--load will be in compression.
Left circled area looks like rasped area not quite cleaned up.
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Bentstick54; the line to the right is just a dark grain line, not a crack. The cluster to the left is tool marks. The bow is still a pretty raw.
Jim; Thank you sir, that was exactly what I was about to ask.
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I agree with Brad. In my early days I've had chrysals at the fades. Jawge
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Windhover? Is this in reference to the Old English name for the kestrel?
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Here is a full set of photos of the bow as it is today. I marked the location of the failure in each picture. It's currently holding just shy of 2" of set all of which seems to have accumulated in the spots that were naturally deflexed to begin with. I don't have enough experience with straightening staves to say if I just failed to really get the deflex out or if my tiller is just bad in exactly the same way that the stave wanted to bend naturally.
(https://i.imgur.com/F8xiWTL.jpeg)
(https://imgur.com/KRIHMMp.jpeg)
(https://imgur.com/2RUniXu.jpeg)
(https://imgur.com/mVAFnuy.jpeg)
Windhover? Is this in reference to the Old English name for the kestrel?
Yep, it's the farm mascot.
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I made a ridiculous tiny hackberry that I cracked in three places forcing too much reflex in during heat treating. I ended up filling with CA glue and tillering it anyway.
It ended up flat after shooting in, and the tension fractures on the belly did not seem to have any real impact on the performance of the bow. It has been fired around a thousand times now and is going strong, although I know now to be more gentle with my application of force until a larger part of the limb is warm.
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Another vote here for tension failure from heat corrections. Feeling very confident that’s what it is. I’ve seen that happen a lot with hackberry when trying to fix wiggles too aggressively with dry heat.
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I've been monitoring it for the past few days and a couple hundred arrows. It hasn't gotten bigger or changed in any observable way so I feel comfortable just filling it and letting it be.
Thanks everyone for the help. I really appreciate it.
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Bending wood can take some experience.Steam or heat gun???It's best to learn from this experience for next time.