Primitive Archer
Main Discussion Area => Bows => Topic started by: DC on June 20, 2018, 05:15:22 pm
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I just started steaming the maple for the next bow. It's about 1"x2". It had only been steaming for maybe 15 minutes and I was playing with clamp positions and such and I noticed that I had no problem moving it to the position I want it. What I'm wondering is should I stop now and let it cool or is there an advantage to going the full 45 min to an hour. Would I get more springback by taking the shortcut? Is there the possibility that the center isn't hot yet and that may come back to haunt me during tillering? By the time I get an answer the hour will be up but for next time.
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I usually air on the side of caution when it comes to steaming. I'm sure the wood species makes a difference, but they must have that rule for a reason.
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I bent small recurves on a yew bow I'm making with 15 minutes of steam for each tip.
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Depends on wood species, thickness and the mood of the wood fairies ;D
Steaming set up is important too, if you are getting real steam (steam is invisible) or just bathing it in water vapour (cloudy visible stuff).
Del
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Could the pro's maybe post a pic of their steaming device - I'm just a beginner and can therefore only steam max. the diameter of my wife's pan's ;D
As im planning to build a decent steaming device that would be very helpful for me.
Cheers
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This post from my blog shows how I do it.
Steam generated using a wallpaper stripper, they are pretty cheap, will give about 40 minutes of steam and shut themselves off if they run dry.
I've recently shortened the steam pipe to stop wasting heat and improve convenience. I use various things to contain the heat round the bow.. plastic 5L and 10L containers are good (best to wrap with something to keep the heat in). Drainpipes etc for longer sections.
https://bowyersdiary.blogspot.com/2012/02/spot-of-steam-bending.html (https://bowyersdiary.blogspot.com/2012/02/spot-of-steam-bending.html)
Del
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thanx del - this help's a lot - didn't even know that there's a device called "wallpaper stripper" - must have! [Edit: Orderd...]
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My steaming set up is a large pot of boiling water with alum foil over it and the area to be steamed and foil wrapped around the bow limb outside of the pot to protect it from the heat coming around the pot.
Clint has a cool set up with a steam generator and PVC pipe. I saw it in action at the Classic.
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Mine is a clothes steamer. Got it at a thrift store for $5. I steam in plastic bags. You can buy heavier plastic tubing that is reusable.
PS If I overfill this one I can get an hour of steam. A wallpaper stripper would probably last longer but an hour has done everything I need.
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How many times will you guys steam a piece before you give up on it. I have steamed this piece of Maple three times trying to get a sideways bend out and it keeps coming back. Is there a time when the wood turns to mush. I have steamed the full hour, overbent it by 20-30% and let it cool for 3-4 hours. sometime after that I look at it and the bend is back. Brat fuel?
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DC I have the same basic set up as you and with the bag it bends very fast, 10-15 mins
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IF a bend keeps returning, try fixing it in place with dry heat after steaming.
I had gorgeous piece of Yew that did that... got her fixed eventually.
I think patience will give out before the wood is ruined :)
Del
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I have some beautiful dogleg hickory staves that seem oblivious to steam straightening, they always go back. I will try a heat gun on the the next time I try to straighten them.
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IF a bend keeps returning, try fixing it in place with dry heat after steaming.
I had gorgeous piece of Yew that did that... got her fixed eventually.
I think patience will give out before the wood is ruined :)
Del
Do you do a full heat treat or just get it hot? I have an infrared thermometer.
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I like that clothes steamer setup. I'm going to have to keep my eyes open for one....
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Yes I do what you'd call a full heat treatment clamped onto original form.Holding heat gun 3 to 4 inches away until browned well on hickory recurves.That'll run temps up to well over 350 degrees F.I don't have any here that'll pull out then.Even from extreme reflex.
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DC I have the same basic set up as you and with the bag it bends very fast, 10-15 mins
What thickness are you bending in 15 min?
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DC I have the same basic set up as you and with the bag it bends very fast, 10-15 mins
What thickness are you bending in 15 min?
Half an inch or so
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I've done some testing where I rifle drill a piece and put a thermometer in the hole and then steam the piece. I used about 1" dia pieces and although I can't remember how long it took it was kind of an exponential curve. The first half heated up pretty quick but the last little bit never did get over 200 degrees. I did keep records but I have no idea where I put them :o :o
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100 Degrees C (212F) will soften for bending.
300 C (~570F ) will heat treat and fix a bend in place.
Del
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My wood starts to turn brown at 400f. 570 would be black. Does that agree with your thermometer?
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For sideways corrections I have the most success with dry heat so now that is al I use for corrections, for recurves I always boil or steam (in a pot, covered with alu foil). Since I started “setting” my boiled recurves with dry heat I have never had one come out.
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Dry heat work's well in my experience but take's experience and patience to avoid overbending leading to a tension break and/or to avoid scorching the wood. Multiple re heat's might be necessary. My theory is that dry heat will temper the bend into the bow so that it is unlikely to pull out. The best thing is that no heat gun's are necessary, it can easily be done over a small fire. Best of luck.
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My wood starts to turn brown at 400f. 570 would be black. Does that agree with your thermometer?
I'm just giving rough figures from a test I did ages ago... I think I was going on the heat gut setting not the actual wood temperature.
BTW, the fancy heatgun with the build in digital temerature readout didn't last long before the fan melted. The cheapo ones work just as well ::)
Del
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The best thing is that no heat gun's are necessary, it can easily be done over a small fire. Best of luck.
Try holding this over a small fire. Weighs about fifty pounds ;D ;D ;D
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I think this one's defeated me. This is the fourth time steaming and this time I followed up with a heat treat to just before browning then left it clamped to the caul overnight. It came out of the caul pretty straight and fifteen minutes later it looks like this.
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DC, put it on your form and use a heat gun(I like to oil the belly and sides before heating) and use clamps and wedges and you should be able to straighten that out.