Primitive Archer
Main Discussion Area => Bows => Topic started by: apg on March 22, 2018, 07:07:48 pm
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Hi all,
Been working a stave into a 45 lb self bow. Made from Osage, and it was evenly tillered before I started working the heat.
I dry heated the limb (no oil) and set it on my jog, weighted the other limb to let gravity pull it down as it heated even more. After about 15 min of heat, I clamped the end, and worked the rest of the limb to flatten it.
I did the same to the second limb the following day after it had 24 hours to set into position.
I found a hairline verticals crack on the bend though on that first limb, see photo. And on the second limb I can see a fraction of a layer has cracked horizontally. I can post a photo tomorrow, but both cracks are in the belly of course.
It should weigh in as a 50 lb draw at 28” I think.
Two questions :
Has anyone had this issue and then shot the bow successfully for a period? Or did it blow?
Does anyone know why the Osage cracked? I heated it until the back was too hot to touch, and the belly was very very hot. It was hot all the way through thoroughly. I bent it slowly. No idea why this would happen!
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was the wood all the way dry? sometimes when the wood isnt dry enough it has a tendency to crack vertically. the bow cracks across the bends usually when they limb wasnt heated enough or bent to fast. The limb itself could of also had a hairline crack you didnt see before heating it. Once heated the wood expands and makes it more visible. The vertical crack shouldnt be any problem. Fill it with CA glue and sand.
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happens to me almost every time. Thin superglue until the crack is filled, and you will be fine. I have thousands of shots on bows like that.
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The stave was definitely dry, and I really heated it a lot, short of toasting the wood. I’ll try the superglue technique.
Maybe I bent it too fast. I’ll go even slower next time.
How about the horizontal crack, like a slight dela, but only in the surface of the grain. Glue that too?
Ash
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apg,
I have had this type of check many times from dry heat bending /correcting with no ill effects, and shot many bows many times with this type of check in them. "But" the difference with what I do than many bowyers is instead of super glue I use a two part epoxy. SG is not a good gap filling glue where epoxy is a good gap filling glue. Use a heat gun when applying the epoxy and you will get good penetration.
JMHO
DBar
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Great tip - thanks.
I find it hard to know if the superglue actually penetrates the crack - seems often just to glide over the top, but I guess that's normal to not know that?
And here's the crack on the other side - same style to fix?
Ash
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That crack is a lot different. it is not with the grain it is across the grain due to bending. Hopefully you have enough wood the remove that crack and continue with the tillering to make your weight.
DBar
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Hmmm. So even though this crack is in the belly where the wood compresses you feel like I should be scraping it out? It will actually matter?
Makes sense it will. Especially at 50 lb draw I guess.
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Its all about how much wood you have available, if you can remove the cracks and not create a hinge then your OK. If you leave as is it will act like a fret/crystle and will hinge in time.
From the looks of it your doing everything right. I've had this happen many times. don't give up remove the crack and see if you have enough wood. If not next time add a little more wood if you cant make the weight you are looking for......but you would be surprise how thin osage can be to make weight. Especially at the tips.
DBar
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Put a thin underlay over the belly side of both recurves. You can narrow the tips to reduce any physical weight they may add. I've done it with great success. You could make brush nocks that would cover the cracks.
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happens to me almost every time. Thin superglue until the crack is filled, and you will be fine.
HA! It only happens to me MOST of the time. I feel so smug and superior. >:D :P
Yeah, I all the time will fill those with glue if they are small. If they are big, or more like the second one, I sand or scrape down a bit an add belly overlays to stiffen the recurve. No big.
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Great... now what on earth is an overlay?
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As PatB says it is called an underlay not a overlay. Maybe Springbuck can tell you how to add an underlay to a recurve tip.
DBar
BTW an overlay is a layer of wood on the back side of the bow an a underlay is on the belly side of the bow....
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Okay I see. So given this is a self bow, maybe I could do an underlay with a couple of strips of leather?
Ash
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As PatB says it is called an underlay not a overlay. Maybe Springbuck can tell you how to add an underlay to a recurve tip.
DBar
BTW an overlay is a layer of wood on the back side of the bow an a underlay is on the belly side of the bow....
Really? I didn't know there was a strict definition. How did I miss that? I've been calling it an overlay for over 20 years regardless whether it went on back or belly.
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No, no, no! :( Nope, not leather, wood. :o
What you want is a nice, strong, thin slat of wood you can either curve ahead of time with heat or steam, a scrap piece of osage or ipe, maybe, OR multiple thin layers so they conform to the curve you want on the recurve.
You sand or plane out the cracks on the belly side of the curve, or at least down in to the wood, making it very flat and squared up, then glue the slat on to the belly to reinforce the recurve, basically replacing the wood you had to sand out, and then some. Then you trim any extra and smooth in the transition so you don't leave a stair step where your recurves start.
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I was sending the same time ......................
An underlay with leather will not give you back the strength you need from wood. a thin layer of wood is needed. But first remove the crack and continue tillering and see if the wood is bending too much compared to the rest of the limb at your target weight before you add the underlay. chances are you will not need the underlay. How thick and how wide is the limb at the crack? And how far is it from the tip? How long is you bow? and one more question what is your target weight? I ask these questions because I might be able to tell if you need a underlay or not.
DBar
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As PatB says it is called an underlay not a overlay. Maybe Springbuck can tell you how to add an underlay to a recurve tip.
DBar
BTW an overlay is a layer of wood on the back side of the bow an a underlay is on the belly side of the bow....
Really? I didn't know there was a strict definition. How did I miss that? I've been calling it an overlay for over 20 years regardless whether it went on back or belly.
Well..... all I can say is that you haven't payed attention to details for over 20 years.....
DBar
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On Osage, I like dry heat on a caul for reflex...Serious bends always get steam, for me, I have had better success using steam time after time, no issues...My theory is the wet outer wood seams to stretch better with moisture instead of the dry heat expansion...Especially on thin ringed Osage...No scorch and nothing brittle in the bend...Osage bends like butter with the right temperature but I feel safer and have had great results with steam...I will never change back now...
Don
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I would flex the bow before I did anything, if the area in questions is still stiff you are good to go without any special treatment. A cosmetic crack that may not have any effect on the bow itself. If the bow is appreciably thicker at that point you can sand it out if you like if not you may just choose to live with it.
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Thanks everyone. I took the bow off the jig this afternoon and scraped and sanded the horizontal crack out of it. It wasn’t deep, but I had to fix the tiller so lost about 5 it feels like.
But it’s smoOth, there are no weird noises and this method helped a lot.
In future I’m going to recurve the bow before I get to final roller and weight, to keep space for exactly this issue.
Thanks all so much again.
Ash
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Glad to here it worked out for ya.....
DBar