Primitive Archer
Main Discussion Area => Bows => Topic started by: stringstretcher on January 09, 2011, 12:16:37 pm
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I have watched Dean Torges video on self bows, and have made a couple in his style. I have met and share some time with Stim Wilcox, who has a book out on making self bows or a flat design, and I have now watched Gary Davis Rattlestick DVD. He also does a flat bow design. What have you found that for a bow of 40-45 lbs or 45-50 lbs design to be beter. This is not a debate question, but rather a performance question. What are the advantages or disavantages to these two totatly different designs?
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The 'style' or profile of the bow has to match the material. Osage can excel at many different profiles, either flatbows or ELBs, but most others can not. That's why osage is so prized as a first string bow wood... it's versatile. Yew, for example, excels at narrow profile, stacked & rounded belly shapes. However, a white wood, like maple, does not. In other words, it's best not to make a narrow D profile rounded belly ELB selfbow from maple. Maple performs better with a wide flat limb shape. For bow designs, I suggest you read the TBBs, especially Vol 1 and Vol 4. They have excellent chapters on bow design and performance.
As far as the pure physics of the designs are concerned, a wide flat limb will spread the compression and tension forces of the bending equally across the entire flat surface of the wide flat limb shape, where as a narrow stacked D profile belly concentrates the force at the apex of the profile. So, in other words, a second string wood, like maple, will survive as a bow wood if you spread the force over a wider and flatter area.
Have you noticed FG recurve limbs and compound bow limbs? Yes, they're wide and flat. That shape is the most efficient, but not always with all wood bows, like yew. You can make a nice flatbow out of yew, however. All said and done, if you match the design of the bow with the appropriate wood, you'll get the best performance.
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That makes sense !
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I agree 100% with adb! Any wood will make a bow but only certain designs work for certain woods. I believe this is one of the most difficult parts for most newbies to grasp. They see a design they like and only have a specific piece of wood and want to build that bow with that wood...and wonder why it failed, fretted or took too much set. ???
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Think in terms of what a round or flat belly will give you Charles. A round belly will put more wood under compression. Where as a flat belly/round back does the opposite. You can have a belly to round for say a BBO, and you can have a flat belly too flat, say for a wide limb hickory....Art
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I round all 4 edges. Because I use hand tools for tillering the belly becomes slightly radiused. It kind of just happens. Jawge
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I made a few osage bows flat bellied. They seem to perform slightly better. But I have switched over to deans faceted tilller technique and like it much better. Seems much easier to control the tiller. Flat, I would be moving along nicely and all the sudden out of nowhere get a hinge. But seems the faceted technique dean describes makes the layers of osage work as a unit.
With hickory, I still go flat. So would I with an ash bow I am planning.
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I just use mainly elm and hackberry, so that no mattter how badly I mess it up, it comes out pretty well anyway. ;D
Although, I am close to done, one way or the other, on my first attempt at an ERC longbow. It'll either turn out functional and pretty, or it'll look like an IED victim. Either way, it'll be "done" soon enough...
But yes, different types of wood tend to respond better to certian designs.
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Think in terms of what a round or flat belly will give you Charles. A round belly will put more wood under compression. Where as a flat belly/round back does the opposite. You can have a belly to round for say a BBO, and you can have a flat belly too flat, say for a wide limb hickory....Art
Actually a round/deep belly will put LESS wood under more compression...compressive forces will have to be soaked by the narrow, deepest part of the belly. Were as the compressive forces will be distributed over a wider area on a flat design. The cost of a flat/wide design is more mass compared to a slimmer, deeper design of the same draw weight and length.
Cheers
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I tend to round them just a bit,about like Jawges said,I still try and keep them pretty flat
just round the edges more than I use to. :)
Pappy