Primitive Archer
Main Discussion Area => Bows => Topic started by: osage outlaw on February 14, 2016, 09:28:17 pm
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I've been heat treating most of my bows lately and I keep getting cracks in them. They don't really hurt anything from what I've seen so far. I soak them in superglue and keep on building the bow like they aren't there. I thought maybe I was overdoing it with the heat so I just lightly toasted a bow this evening and it still cracked. When I take the bows off my form I usually find a few cracks that opened up on the back. I know moisture will cause it sometimes. The bow I did yesterday was from a stave that was cut sometime in the early 90's. It's been in my shop for the last year and a half. I roughed the bow out and left it alone for a week or two in 50% humidity. I didn't think it would have that much excess moisture left in it. Is there something I could be doing different to avoid these cracks?
The lightly toasted bow
(http://i666.photobucket.com/albums/vv22/Outlawstaves/20160214_191118_zps3b5rwo65.jpg) (http://s666.photobucket.com/user/Outlawstaves/media/20160214_191118_zps3b5rwo65.jpg.html)
The old stave that I put a darker temper on.
(http://i666.photobucket.com/albums/vv22/Outlawstaves/20160214_191141_zpssq49mfn2.jpg) (http://s666.photobucket.com/user/Outlawstaves/media/20160214_191141_zpssq49mfn2.jpg.html)
The same bow on the back. This crack was barely visible before the tempering. It opened up quite a bit.
(http://i666.photobucket.com/albums/vv22/Outlawstaves/20160214_191221_zpsalxzaeex.jpg) (http://s666.photobucket.com/user/Outlawstaves/media/20160214_191221_zpsalxzaeex.jpg.html)
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I used to use oil. When I quit I started getting cracks. Went back to oil and no cracks. No science just experience.
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Thanks Jon. I'll try oil on the next one. I used it on my first couple bows but haven't since. Do you just oil the belly or do you put it on the back also?
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Moisture is my bet. 50% is still a bit high, unless you had constant air moving past it.
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Even seasoned staves have mosture. You've taken out what moisture was in the stave by heating the limb to hot to quick causeing the cracks.
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Moisture is always the culprit in this case and it seems that the denser the wood the more of a problem it becomes
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When I use dry heat, I always grease it up good all the way around where I'm aiming that heat gun. If I am steaming, I put on 2 coats of shellac. Seems to work well, haven't had one crack in a long time
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Doesn't matter how long wood has been seasoned it can still shift move warp and crack when the ambient conditions change (e.g when you heat it).
Del
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It's just one of those things, Clintster. Can't do much about it. Oil does seem to work however, it is hard to glue on a snakeskin over top the oil. Or sinew...
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That's why I quit using oil Matt. I had an entire sinew backing peal off in one big strip. I didn't get all the oil out of the wood.
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I have had oil lathered sticks do that, that's why I don't use oil anymore. When moisture expands and needs to escape, its going to go right through a film of veggy oil.
Just chalk it up to being a rookie......
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Cracks like that were the death of my Marshal bow from last year. Well, that or me being a bit over zealous trying to get that lower lim to work its way around. I filled them with super glue, but must have missed something, drew it back and heard a crack, one of them(the largest) had grown. Haven't drawn it since.
Does make me feel better that someone with as much experience as Clint still runs into the problems I have.
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Was the back sealed, Clint? I seal newly exposed backs wit shellac and make sure they are sealed before correcting with heat.
Filling with super glue is what I've always done.
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Moisture is always the culprit in this case and it seems that the denser the wood the more of a problem it becomes
I second this. I live in a very dry climate, and get sall kinds of drying checks, but almost never have checks during heat treating........except on black locust and red mulberry heartwood. I don't get a lot of osage, but the one time I tried heating some jatoba and ipe, I got some checks.
Definitely try oil. I started using coconut oil recently and it's the bomb. Also, in lieu of a hotbox, maybe try running over the wood with the heat gun, warming it all over the belly, but not toasting it, and letting it settle a day or two before the actual tempering?
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Thanks guys.
Pat, the back was sealed with a thick layer of polyurethane.
Jackson, there are a lot more experienced guys on here than me. That's why I'm asking them for advice.
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I too have the same problems once in awhile. I can never seem to put my finger on the cause though cuz there's always so many variables. I have noticed or at least I'd like to claim that certain batches of Osage are more prone to this. And other batches I've had never seam to get a crack. Obviously moisture plays a big part in it but I also believe that where it was grown and possibly mineral content or whatever else makes up wood may have something to do with it. I guess that's one for the scientists. One thing that does help me is slower preheat. Now I'll keep that gun moving up and down that limb for a good 12 inches at a time before I start dumping real heat into it. Sort of the same concept when your welding heavy metal or cutting with oxy fuel. Preheat has helped me but sometimes it does nothing. Sorry Clint not much help here
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That was helpful Paul. Now that I think about it, the bows that have cracked the worst have been red osage. The bows from the more yellow colored wood have had less cracking. And I try to move the heat gun down the limb to preheat it like you said. I reflex it and temper it at the same time. On the next one I think I'm going to reflex it on the form and then wait a day to come back and temper it while its still clamped down. I'll see if that makes a difference.
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I use Crisco everytime I dry heat bend and never had a problem with cracks. If I add snake skins I just "wash" it in acetone before I glue them.
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when you heat it use oil.you wont have cracks.Tony
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That's what I use mullet, Crisco
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I don't have problems with cracking during heat bending. I'm getting cracks during the tempering.
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I've seen PLENTY of oil slathered cracked bows. Its not that cut and dry. Pardon the pun :)
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I have had it happen from time to time, mostly on fairly new wood 1 or 2 years old. I do usually seal the back and sometime use cooking oil on the belly, still happened from time to time. I don't usually heat temper Osage but have had it happen when it needs some heavy corrections. ;)
Pappy