Primitive Archer
Main Discussion Area => Bows => Topic started by: upstatenybowyer on December 11, 2016, 05:56:29 pm
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This has been happening especially when adding reflex against a simple caul. I think the heat gets trapped between the bow and the caul. Crowned staves are worse. I guess I could thin the caul so it doesn't stick out to the side of the bow. Any thoughts?
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Patience ..........drop the heat gun temp down a notch, pull it back an inch or two and slow down.....patience.. from experience. ;)
DBar
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Can you post a picture of your caul? Are you trying to heat it to quick? Are you holding the heat gun so it blows on the belly of the bow or on the sides of the limbs?
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I tried making a 3/4" caul for that reason but found I couldn't bend the bow sideways if I wanted. The bow was stronger than the caul.
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Can you post a picture of your caul? Are you trying to heat it to quick? Are you holding the heat gun so it blows on the belly of the bow or on the sides of the limbs?
I hold it directly over the belly about 4" away. Maybe it's happening when my arms get tired and I unknowningly lower it. Sounds like slower and further away is the key.
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Are you holding the heat gun in one spot for a long time or do you keep it constantly moving?
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I just hold the gun at about a 45* angle to the wood and keep it moving. I go slow enough that you don't want to hold your hand on the wood once the gun passes. Then just keep doing slow passes until the wood get to the color you like. The only time I have issues with a little edge and back scorch is when I try bending out a side kink and I get in a hurry. I think that between concentrating the heat in one spot and the heat rebounding onto the back. Though I've never had an issue from a light toasting on the back.
Kyle
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I made a jig to hold the heat gun. It's hard to hold it an even distance away for 45 minutes.
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I've been meaning to make one of those DC. I think Marc has a pic of one he made in TBB 3.
Moon that sounds like a smart way to do it. I've been staying on one spot until it browns up and that could be the problem.
How do you guys add reflex? I usually clamp near the handle, start heating and bend and clamp as I go. I never want to bend the wood into reflex while it's cold.
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I hold the heat gun 1" to 2" above the belly working it back and forth over a 6" area. When that area is chocolate brown I move out to the next 6" going back over the previous area(s) until I'm at the end of the working area of the limb. Once it's all tempered and the clamps are in place I go over the entire limb again then let it cool over night at least before I unclamp it. Doing it this way I can lightly temper a limb in 30 minutes or less.
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One thing i think is important, if your caul is charred you need to sand it down. Once it is charred it is charcoal basically and it ignites faster than uncharred wood and will char the back faster with less heat
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clamp side cheeks to the edges of the bow.
http://bowyersdiary.blogspot.co.uk/2015/02/two-steps-forward-one-step-back.html (http://bowyersdiary.blogspot.co.uk/2015/02/two-steps-forward-one-step-back.html)
This youtube video shows it in action:-
https://www.youtube.com/watch?v=kM1_A2A0_TI (https://www.youtube.com/watch?v=kM1_A2A0_TI)
Del
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It is very simple - just make your form narrower than the bow.
If you need a form to bend limbs sideways etc then make a separate on that is up to the job.
Mine is a piece of oak 1 inch wide and 4" deep.
Making a holder for the gun is pretty much essential if you are going to be doing more than a few heat treated bows. Forget holding it.....BORING!
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I do like Mike, 1 for straightening and reflexing and one for heat treating if I decide to do so. :)
Pappy
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These comments are amazingly helpful. Thank you kindly gentlemen
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Same as Mike and Pappy, I scorched a few before I got around to building the narrower caul. I always heat the entire limb in long passes just going back and forth. It takes me about 6 seconds for one pass and I make about 200 passes, comes out to about 20 min per limb. I think it is a bit faster because I can hold the heat gun closer if I am doing a larger area and keep it moving. I never go for a toasted look but rather a specific smell and slight darkening of the wood.
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With the help of all your insight, I narrowed my caul, sanded it down and revised my approach to using the heat gun. No scorching! Thanks as always for taking the time to share your knowledge and experience!
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Like Mike and pappy.I even make narrower duplicates of your static bend forms.I steam bend most statics.Then I temper them after they cool and dry.I'm one who will stand there holding it 4" away in one spot moving very slowly according to the color for a nice even treatment.A 3" c clamps' height is just right at 4" tall for a reference.Correcting propellers/whoopteedoos/ and balancing profiles of limbs are on your standard 1.5" wide forms.Every great now and then a little edge over browning occurs but nothing bad.