Primitive Archer
Main Discussion Area => Bows => Topic started by: Badger on August 01, 2019, 01:59:29 pm
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I was looking up heat resistant tapes for backing bows during a heating process. I am hoping to be able to put an entire bow in a makeshift oven and set it at somewhere between 250 degrees and 300 degrees until desired color is reached without burning the back. I found a tape on line that is 3.5 mil thick and will withstand temps up to 500 degrees. Naturally I would do some experimenting with scrap woods to get the best settings needed. The tape runs about $100.00 per roll and is only 36 yards of tape 2" wide so it runs about $1.00 per foot. I think it could be used more than once if installed over a clean back. So if I could use it 2 or 3 times it would cost about $2.00 per bow. Any opinions on how something like this might work?
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Great idea. I think you should be looking more at insulating value than heat resistance. Well, both but you get my drift. It may not stop the back from over heating. What do you plan on for an oven?
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For an oven I am toying with the idea of something with a glass front and long screws coming through the top that I could use to force the bow around a caul and then continue to heat for a while. I would use propane or natural gas as the heat source.
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I wonder how the heat will effect the adhesive on the tape.Is there any chance that it will “set” or “cure” it to the back of the bow making it difficult to remove? Might try a small piece on a scrap before permanently running a bow.
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You might need more than 300 degrees to heat-treat
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You might need more than 300 degrees to heat-treat
I was wondering about that, I guess it would take some experimenting. I am really curious if a longer lower temp heat treat might have more effects or not.
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My question is, does the tape insulate against heat, or simply resist degradation due to heat... I have my doubts about the insulating properties.
At the price, it seems an inquiry to the manufacturer is in order.
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Regularly thinking of better ways. :OK (-P
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My question is, does the tape insulate against heat, or simply resist degradation due to heat... I have my doubts about the insulating properties.
At the price, it seems an inquiry to the manufacturer is in order.
This is my thought too. Obviously the back of a bow can still get very hot during heat treating too. We probably don't exactly know how hot it can get without suffering .
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This has been a question on heat treating I have had for a long time. Is it the heat alone that transform the wood, or does it take pace with the charring. What is the catalyst for change?
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I think there's the whole Farenheit/Centigrade thing going on here ::)... I recon on about 200C for heat treating... which is, as Marc says is say well over 300 F (~390F)
Personally I've gone metric every inch of the way ;) ;D ::) 8)
I agree with the point about needing insulation, that's the great thing about a heat gun, you can direct the heat and shield sensitive areas.
Almost needs an oven with adjustable sides so it can clamp down on the sides of the timber leaving the back outside the oven and the belly exposed to the heat... a bit impractical :( >:(
On the other hand maybe slathering the back with clay, like they use on knives when heat treating?
Del
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Hmmm,,,I'm stumped (W
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This has been a question on heat treating I have had for a long time. Is it the heat alone that transform the wood, or does it take pace with the charring. What is the catalyst for change?
Slimbob, the heat treating method I use seldom involves any charring. Currently I use a heat gun and go from one end of the limb to the other in about a 3 second stroke. hen I am finished the back of the bow is too hot too touch and the belly is just darkening a bit kind of like how it does just sitting out in the sun for a few days. There is a very distinct smell that I am looking for. It is a little different with different woods but unmistakable. I am hoping to find the temp setting where I can get this smell and then hold it there for a while.
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This helps identify the proper range. Bamboo is not technically wood but it is close enough. Keep in mind this scenario has the whole piece equally treated.
http://www.powerfibers.com/BAMBOO_IN_THE_LABORATORY.pdf
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That is a good article Pat, not sure how the thickness of bow limbs as opposed to bamboo would affect this, I would think about 1/8" of depth on the belly side would be mainly what was needed. They don't seem to concerned about the tension side of the boo being scorched.
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When I heat a bow there will hardly ever be char on the wood any more. After probably a thousand hour on the heat gun you learn a few tricks no matter who you are. I use the barbecue test for steaks
For heat range. Heat the wood and put your fingers on the area heated. 1-2-3 whoa that’s 350 hands off. Keep the gun moving as Gary would say . Then gently clamp if needed. Arvin
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You might need more than 300 degrees to heat-treat
I was wondering about that, I guess it would take some experimenting. I am really curious if a longer lower temp heat treat might have more effects or not.
Steve,
longer times at lower temps could be a worthwhile experiment, but I think a protective tape like you describe would only be effective if the heat treat times were very short.
perhaps your oven design could incorporate a floor that would allow the belly to be inside the oven, and the back to be outside the oven, or immersed in water or at least stay damp somehow
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I would not put the whole wooden bows or limbs in oven. I have been thinking about buying a "Mandolin Side Bending Silicone Heat Blanket w/Controller". I want to use it for dry bending limbs and tips. But it might be useful for heat treating as well. They are cheaper than the tape you are talking about.
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There is a specific reason I bring this up. Made an Osage bow few years ago. 65 inch flat bow. I flipped the tips early, but towards the end I decided to go with a some pretty radical reflex. Around 6 inches. It was a lever bow so some was in the non bending levers but some was along the working limb as well. I turned the dial up on the heat gun and did a pretty shallow, high temperature temper. The belly turned the color of dark chocolate. It has held up well. Some pulled out over time but no more than any that were tempered deeper and more slowly. I have not measured it lately but it ended up with around 3 to 4 inches. This bow has made me ask this question.
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There is a specific reason I bring this up. Made an Osage bow few years ago. 65 inch flat bow. I flipped the tips early, but towards the end I decided to go with a some pretty radical reflex. Around 6 inches. It was a lever bow so some was in the non bending levers but some was along the working limb as well. I turned the dial up on the heat gun and did a pretty shallow, high temperature temper. The belly turned the color of dark chocolate. It has held up well. Some pulled out over time but no more than any that were tempered deeper and more slowly. I have not measured it lately but it ended up with around 3 to 4 inches. This bow has made me ask this question.
The bamboo link that Pat supplied does a pretty good job describing the changes that take place at different stages. I didn't read it in detail but plan to go back and reference it as needed.
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There is a specific reason I bring this up. Made an Osage bow few years ago. 65 inch flat bow. I flipped the tips early, but towards the end I decided to go with a some pretty radical reflex. Around 6 inches. It was a lever bow so some was in the non bending levers but some was along the working limb as well. I turned the dial up on the heat gun and did a pretty shallow, high temperature temper. The belly turned the color of dark chocolate. It has held up well. Some pulled out over time but no more than any that were tempered deeper and more slowly. I have not measured it lately but it ended up with around 3 to 4 inches. This bow has made me ask this question.
I've not tempered a lot of Osage bows but from the ones I did I found that Osage reacts differently to heat than a white-wood. It turns brown faster and the heat seems to penetrate faster, could be the quantity of oil in the wood does this. I quick temper on HHB or Elm will not do much
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I too see a difference in Osage and white woods when it comes to heat treating. I will add Mulberry to that as I just finished one. I did a fairly quick heat treat with a dark color, just as I would do Osage and most of the reflex has held up. Maybe the oils do allow the heat to penetrate more quickly. I haven't had the chance yet to read the post PatM posted but I will.
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I’d be worried about the tapes insulation ability too, the company I work for makes industrial kilns so we use similar products on a regular basis.
What you described sounds like it is meant to hold insulation in together, not provide insulation it self.
Something that might work in combination with said tape for you is some sort if ceramic fiber paper.
At work we have it down to 1/8” thick and anywhere from 1200-3000 F
It’s not cheap but a strip of that fiber would definitely be reusable a couple of times.
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I’ve always thought a salamander would be good for heat treating, basically a broiler oven open on both ends. I’m thinking just the radiation heating without all the convection should probably be better for not scorching the back. I like del’s idea of the blacksmiths clay or mud, that was my first thought as well. Maybe reusable putty could be made of silicone...
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Hi Steve
any further thoughts/experiments about this concept? I think a differential heat treat may be worth looking into
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Hi Steve
any further thoughts/experiments about this concept? I think a differential heat treat may be worth looking into
I wish I was as motivated as I was even 10 years ago. Sometimes I throw ideas out there and I don't always get around to trying them. I actually like the mud idea mentioned above, clay is easy to get and easy to wash off. A slower much longer bake is really what I would like to accomplish. Sometimes things happen when they hit a certain temp and sometimes things happen when they are held at a temp for a longer period of time. I recently bought a souz vide for cooking roasts mainly. I can cook a roast at about 134 degrees for 24 hours and it melts all the connective tissue that makes it tough. Something slow and low is what I am hoping to try with wood.
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Steve could this be done on a straight stave bow and then induce the reflex in another heat treatment ? Arvin
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Arvin, that is kind of what I was hoping for. Not really sure but I think so.
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a thought I had a while back when you first posted this thread was to bed your stave on the caul with the mud or tape and have some sort of reflector holding a electric radiant element above it to shine down in the belly surface. you would not neccesarilly have to keep he caul inside the heated area or have the assembly enclosed for that matter.
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[/quote]I actually like the mud idea mentioned above, clay is easy to get and easy to wash off.
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Dont't try this without glasses and helmet! I did it some time ago and the wet clay sucessivly exploded in little pieces while I did heat treating...the little pieces are quite aggressive and hurt badly in the face. Something like mud is maybe the better opition...
Cheers
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This has been a question on heat treating I have had for a long time. Is it the heat alone that transform the wood, or does it take pace with the charring. What is the catalyst for change?
Slimbob, the heat treating method I use seldom involves any charring. Currently I use a heat gun and go from one end of the limb to the other in about a 3 second stroke. hen I am finished the back of the bow is too hot too touch and the belly is just darkening a bit kind of like how it does just sitting out in the sun for a few days. There is a very distinct smell that I am looking for. It is a little different with different woods but unmistakable. I am hoping to find the temp setting where I can get this smell and then hold it there for a while.
Badger maybe get an infared thermometer, do your standard HT and then you can get the desired heat range with the thermometer
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I use an infrared thermometer when I'm heat treating and the "turning brown" temp seems to be right about 425f.
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Ok I might be missing the whole point of this experiment but why not just bake the whole thing then add a backing. Unless you are also trying to also heat the backing but to a lesser degree. If it were me ( once again I could be missing the point of this) I would rip the back off the stave bake the whole thing then add the backing back to the bow. That way its the same wood. But then again your probably wouldnt be able to know if the performance increase( if there is one) would be from the backing you just added or the baking you did.
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Need some heat shield tiles from a he space shuttle.
I agree with Marc. Seems to be a big difference between Osage and HHB in the way they respond to heat treatment.
Bjrogg
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Ok I might be missing the whole point of this experiment but why not just bake the whole thing then add a backing. Unless you are also trying to also heat the backing but to a lesser degree. If it were me ( once again I could be missing the point of this) I would rip the back off the stave bake the whole thing then add the backing back to the bow. That way its the same wood. But then again your probably wouldnt be able to know if the performance increase( if there is one) would be from the backing you just added or the baking you did.
This is on my to do list. I think a good idea.
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I agree, Nasr probably has a good idea there. I can't remember where or what exactly I read once about a heat treating method that modified the wood so that the wood did not want to re-absorb as much moisture as before. Maybe something to do with a longer treating time?
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I'm working on Nasr's idea. I sawed the back off a piece of Ocean Spray. Then I wanted to heat treat the belly part. I have a radiant heater I built a few years ago by stretching out an old 1500 watt heater element. Earlier in this thread Badger had said he wanted to heat the wood in an oven and force it to shape while it was in the oven. I could get close to that. I heated one side until it was 450°f. At that point the other side was 250° or so. Then I flipped it over and started heating that side. The side that was 450° dropped to 200°. I heated this side until it was 450° and the other side had gone back up to 230° or so. This meant that the whole thing was at least 230°. Then I quickly clamped it to the form. It was really tough to get it to bend. I let it cool for a couple or three hours and unclamped it. It straightened right out. OS bends quite well with steam and this was hotter than steam but it wouldn't bend. If I take a piece of OS and steam bend it and then lock it in with dry heat it holds its position very well. I don't know why this wouldn't work. I'm steaming the piece now and I will dry heat it tomorrow. We'll see what happens.
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hey! I was just about to say we should try it! (lol)
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Go for it, the more people do this stuff the more valuable the results.