Primitive Archer
Main Discussion Area => Bows => Topic started by: Little John on January 11, 2019, 10:28:37 am
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I cut an elm sapling (about 2 1/2 inch diameter) this past summer, intending to make a de crowned back and belly bow. I went ahead and de crowned the belly but left the handle section big enough for handle so that it would draw itself into some reflex. It really did work, now I have the back de crowned and the bow is dry and kind of roughed out and has about 6" of reflex. I am shooting for a performance type simi flight bow with narrow light weight tips. I just finished a bow of the same design from a tamarisk (salt cedar) of about the same diameter and with about 2 and a 1/2 inches of reflex, it finished up at 55# and pretty much straight with just a bit of reflex. I would like the elm bow to end up with a couple of inches of reflex when finished and shot in but the 6" or more of starting reflex has me kind of concerned. That would be about 10 inches of tip movement just to get a string on it. Any ideas welcome. Kenneth
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I've always found that a lot of that "drying reflex" will pull out when you start to tiller. The bad part is you never know how much will come out. I usually work it out to about 20" on a tight long string and then decide what to do. Hopefully by then it's kind of settled. I've never worked Elm so I can't help you there but as long as you can stay away from string alignment issues reflex is good. I've never decrowned a bow either so I would lean toward less reflex because of that but only because I'm chicken :D
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Dried in reflex really doesn't mean much. You really shouldn't have de-crowned it though.
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Thanks for the replies DC and Pat. I do not worry too much about the string alignment as the handle and tips are still wide with plenty of room for adjustment. Maybe I will go with what I have till I get it floor tillering then can maybe decide what I want to do. I de crown these small diameter trees so as to have a rectangular cross section with all the wood doing its share of the work, this is my third of this design (basicly a board bow) and have had good luck so far.
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Kenneth, about 3 1/2" and when I use a form for straightening and adding full bow reflex it is about the same. Elm lends itself well to belly tempering which will help set the reflex.
When I get staves with too much reflex(more than 4") I reduce and even up that reflex by putting it on the form and temper it to set it. Near the end of the tillering process I like to clamp the bow back on the form and give it a final heat treating.
I've only done one decrowned bow and that was many years ago so I'm just assuming my process will work with decrowned staves.
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I de crown these small diameter trees so as to have a rectangular cross section with all the wood doing its share of the work.
This is not necessary and an outdated idea, especially for an Elm sapling.
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Elm is one of the best woods for decrowning very unlikely to lift a splinter. If you are going for performance and not sinewing the bow I have always felt it is more important to keep as much of your starting profile you can instead of starting with a lot of reflex and then hoping to finish with 2". I would rather start with 3 and finish with 2 than start with 6 and finish with 3. When a bow takes set it also greatly increases the hysteresis in the bow. Thats why wood bows are generally built without much reflex as opposed to horn composite bows that use extreme reflex. 2 different materials require vastly different designs.
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Thanks Pat and Steve. Now I am a bit confused as to what to do. Basically right now it is what it is, the good part is that I have nothing but a bit of time invested so far. Maybe I will remove some of the reflex and then heat treat. Oh Pat I do not remember haw much reflex the osage pole you gave me back when had but now still has two inches, I de crowned it also and sinued as it had a lot of pins.
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John, my first piece of advise is to do what these other guys say. They have way more experience than me. The bow I'm working on at the moment has 4.25" of reflex. When I finish/break it I will have a little more experience ;D
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I hear you brother
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What DC said, but if I get little set, no set,or reflex I have made a bow that I can live with as long as the set is no more than an inch.
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You would still have a hot bow with 2" of set. It wouldn't kill it. Have you considered deflexing a bit through the handle? The real tip off to what kind of set you have happens when you un brace the bow. If it gains a lot reflex back you will have hysteresis, If it just gains back a little you should be in good shape. Set is really hard to identify, some of it is just the shape pulling out with no real damage to the bow, other times you will be crushing the belly fibers. I have found that I can gauge it pretty good by watching how much it returns when unbraced, the less the better in my understanding.
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Badger, did you say once before that you can tell the difference between pullout and set using that method. Pullout is permanent and set kinda comes and goes?
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Little john...6" is a bit much even with the most elastic type woods out there backed with air.I'd tone that down deflexing the handle & fades some leaving you with 4" or so.I did'nt get the length on the bow though.
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I have found that Elm bows performs better when they have a high crown and they take less set. This is probably due to the wood having lower compression strength with a high tension strength. If the wood has fine growth rings then a high crown can might be a bit tricky
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Badger, did you say once before that you can tell the difference between pullout and set using that method. Pullout is permanent and set kinda comes and goes?
Not 100%. but I have noticed bows that tend to come back after unbracing seem to have lower efficiency than bows that stay the same after unbracing. So it kind of leads me to believe that not all set is alike. I have had bows that lost 3" of induced reflex but still behaved like a bow without much set, these same bows also remained mostly the same after unbracing.
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Thanks Steve, I'll try and remember that. I think it will be handy. Most of my bows have induced reflex and it can get real confusing at times trying to distinguish between the two.
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The stress on the limb is going to be related to total limb movement. At 28 inches of draw the limbs are only moving a portion of that distance. I can't remember exactly how far they move. It also depends on brace height and if it has reflex/deflex. Anyway increasing reflex increases, significantly, the limb movement required to get similar draw lengths. So ask yourself, would you be comfortable adding that much extra to your draw if it was a straight bow. At your 6 inches of reflex it would be stressing it like if you drew it to 34" given your normal draw is 28". Actually it would be even more than 34" since there is more draw distance acheived for a given limb movement, but you get the point. A lot of people won't hesitate putting 3 inches of reflex on a bow, but if you instead asked them to build that same bow with no reflex out to a 31" draw they would be hesitant. More and more, I am leaning away from reflex. Like badger, I'm thinking it's better to start with no reflex and get no set, than to start with lots of reflex only to end up with just a little.