Primitive Archer
Main Discussion Area => Bows => Topic started by: Likemp on May 14, 2020, 01:55:34 pm
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I'm a little stuck/less-than confident in what the next steps should be on this black locust flat bow. One limb has some fun natural reflex to it, while the other is dead straight. I tried to mirror the reflex onto the flat side with steam - left it in the clamps for 24hrs and brought it inside for a couple days afterwards, but all the reflex disappeared before I could even try bending it and was I left with a handful of these fractures across the limb. They look like compression fractures but they occurred before they were even compressed so I assume they are from drying after steaming?? The other limb is looking good in terms of not having any similar chrysals or fractures, even though it has the natural reflex as well as a knot towards the end of the limb. Which, makes me feel like the cracks on the other limb have more to do with the steaming it received.
So, while there's still been a lot of wood to take off I've just been tillering as-is, hoping maybe I'd get past the fractures to where I'd be more confident in trying to heat some reflex into that side again and toast the belly a bit. I haven't seen any set at this point from long string tillering and working the limbs quite a bit. But, would I just end up ruining this bow if I try anymore heat corrections and/or tempering? Do I just accept it's asymmetry and continue forward? Am I limited in my options for any heat treating because of the fractures? Is it a dud altogether?
Any suggestion/wisdom is much appreciated!
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Scrape the belly smooth so you(and we) can see the possible frets better. If what I think I see, those frets look pretty bad.
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Well, it looks way worse now. Probably why I was subconsciously sticking with the rasp and avoiding the scraper. Especially that one farthest out towards the tip. I understand some fretting is ok, especially with black locust which is prone to it, but these seem bad... Did it just dry too fast after steaming? My acceptance of my inexperience had me waiting for this, but I expected it to happen on the difficult limb and from poor tillering...
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If you can reduce the thickness evenly along the limb to eliminate the frets(not just at the frets) you may be able to save the bow but good tillering after that will be paramount.
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Do you happen to know the history of the wood? I've had very little experience with BL but it looks like maybe early signs of rot. Is it sapwood? Just spitballing here, can't really tell without having the wood right in front of me.
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Thanks Pat, I'll take that as my best option at the moment.
DC - It's from a small tree, maybe 4-5in in diameter that I took down from a small grove on my property. I removed all the sapwood so this is just heartwood. Are you thinking the yellowing and darker toned wood is the pre-rot? The texture doesn't seem to change there or anything, it's actually really beautiful. I was looking forward to polishing it up. It is relatively wet where I'm at, but not overly so, we're not down in the valley where it floods or anything, but the trees I've taken down so far all have big fat rings, 3-4 rings per inch.
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Sounds like you did it right. Just a shot in the dark :D
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They look like tension fractures and not chrysal/fretted.i have found that wood not completely cured are suspect for such breaks across the grain.they can run quite deep and are not easily removed....with fretted a ridge line is easily felt .tension fractures feel smooth.
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I am with bushboy on this one. I have had this happen with black locust when trying to induce reflex. If you got these before ever tillering then you should not have frets. You should be able to keep moving forward with only aesthetics issues. However if you try an induce reflex on that limb again, they stand a good chance of getting worse.
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Yes how can they be compression fractures from steaming!?
they look like tension failures to me.
Also that doesn't look like great BL
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You are all confirming my fear that I was heating and reflexing while too green. I knew they came from tension and not compression, just used to seeing so much about frets/chrysals with BL, and they look similar.
Bushboy - They do feel smooth to the touch.
Mike - This has been my main question. They look nasty, but while working the bow, there is no set (yet) and those spots don't seem to be effecting the localized areas (yet) or getting any worse...
Bownarra - What about it doesn't look great? I've had a feeling it wasn't the best, but what do you see in the pictures?
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Are the "cracks" on the belly or the back? Compression fractures (aka. frets, chrysals, etc.) show up on the belly, tension fractions on the back.
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It's only on the belly. But they appeared after an attempt at inducing reflex with steam and before the limb was even worked after un-clamping.
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How did you steam it and for how long?
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Don't feel bad. The first 3 B Locust bows I made failed either from belly frets, or the back broke.It was really thin ringed wood so I didn't chase a ring.The last 3 I built turned out good.That log had thicker rings, and I was able to chase a heart wood ring ,and it was much better looking wood.I also trapped the back.Learn from that one,and build another. With B locust your tillering has to be spot on, so go slow. A gizmo will help.
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Although i am inexperienced.. i have seen those kinds of cracks happen when recurving and it ussually seemed to happen when it didnt get steamed properly..
-Fox
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Unless you put a radical, isolated bend in the limb or unless the wood is rotten it shouldn't have cracked in tension.
The discoloration is normal in locust from my experience unless the locust is infested in rot. You should be able to tell if it is rot if it is softer than the surrounding wood.
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DC/Fox - Steamed it over a large shallow pot on the stove, wrapped in a washcloth, covered in tinfoil, rolling boil probably for an hour. Then, right to the clamps in the shop for 24hr and then into the house.
Bassman - Thanks for the support, I'm really enjoying this process. The fact that every failure I've had so far directly translates into a new bit of first-hand knowledge I can use is pretty satisfying in it's own way, but it can be frustrating wanting to move quickly. I'm lucky that I have access to the little bit of wood that I do for rounds 2, and 3, and 4... If I was trying to source staves from somewhere or buy them that would be a different story.
Pat - I don't think the bend was too radical, I feel like I've been guilty of not going far enough out of lack of confidence. The fact that I lost most of the reflex after bringing it inside and before bending it makes me feel I did the same here. The texture of the off-colored wood is no different than whats surrounding it, it's actually quite attractive in my opinion.
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DC/Fox - Steamed it over a large shallow pot on the stove, wrapped in a washcloth, covered in tinfoil, rolling boil probably for an hour. Then, right to the clamps in the shop for 24hr and then into the house.
So you wrapped it in a rag, wrapped tin foil around it and suspended that bundle over a pot of boiling water?? If so the wood never even got warm, not through all that insulation. Maybe I'm misunderstanding.
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No problem! I wrapped the limb in a rag so the belly wasn't resting directly on the hot edges of the pot when I laid it across, then I covered the pot in foil with the rag-wrapped limb under the foil. Much like most of the pics I've seen on here.
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So the wood was exposed to the steam?
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Very much so, for about an hour.
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OK that's all I've got :D
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Do you have a heat gun? For reflexing, dry heat works well with black locust and you can temper the belly to black to help increase it's resistance to taking set and fretting.
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I agree with Bushboy. Those are tension cracks on the belly from when you added reflex. If you keep bending the bow with them still there they will start to collapse under compression and act like frets though.
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My first thought after looking at the picture was tension fracture, just as many people here said. One hour of steaming might have made the unseasoned belly suddenly too dry and when reflexed it just gave out eventually. That would explain the loss of reflex immediate upon un-clamping. I would forget about reflexing the limb and just deeply heat treat the belly and apply crazy clue or epoxy after it cools down. Good luck. I also would probably go for much lower draw weight.
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SCP - Thanks very much for your input, you just answered a lot of my additional questions. You think a shorter steaming session have left me without the fractures? I wasn't shooting for an hour, just erring on the side of "more-couldn't-hurt" and may have forgot about it while working :P. The wood is definitely not fully cured, but I had steamed/heated a rough bow I made from the same tree before and didn't have a problem so that may have given me some unwarranted confidence ;D.
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Do you remember which side, back or belly, was facing the steam? Unlike boiling in water, it might matter which side gets more steam and higher temperature. "Plastic[ized] wood can be compressed by up to 25-30 % but stretched by only 1-2 %. (This is why heating the inside of the curve is most important.)" This is somewhat counter-intuitive. I guess we cannot steam the belly too much, compared to the back, in reflexing the limbs.
Same goes with the dry heat bending. But in bow making, we cannot apply dry heat to the back too much because doing so might make the back too brittle, unless we are just making static recurve tips. Still counter-intuitive. I never apply dry heat to the back, even at tips.
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Pat B/Weylin - Thank you guys for chiming in as well! I do have a heat gun, would a deep tempering help the cracks better handle compression and keep them from turning into frets? or would any heat at this point make it worse?
scp - I made sure to do it belly side down. Everything I've read has been very clear on being careful to not heat the back too much, but are you saying for reflex maybe do back side down and for less time?
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I have a bad habit of leaving the bow tip belly up on the form and steam it while letting the weight of the bow itself bend in the static recurve. I used to steam it from above, on the belly. Doing it that way I did get the tension fracture on the belly a couple of times over the years. Now, I steam the back of tip through a hole in the form.
Many people are saying that the tip bending should be done at once after the bow tip is boiled or steamed fully, but not too much. I think the bending should be watched carefully especially if we are not using a metal strap to protect the belly. We also should not steam the tip too long. It would take less than 15 minutes of steaming to make the thin tip pliable.
Reflexing the limb, not just the tip, using steam on the back might be a different story. I doubt steaming the back would harm the bow as much as using dry heat. But I just use the deep dry heat treatment on the belly to reflex any part of the limb other than the tip.