Primitive Archer
Main Discussion Area => Bows => Topic started by: DC on June 26, 2015, 03:14:59 pm
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Not me, the bows ;) ;) For me that ship has sailed. Anyway when I started this I read somewhere that the belly of a bow should be flat to make it resist compression and avoid chrysals. Recently I've read a couple of posts where the writers have pretty much scorned flat bellies. Should a flat belly be restricted to high tension/low compression wood? Is there a rule of thumb I may have missed?
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I still like a flat bellied bow but I just feel that completely flat bellies are a product of power tools.
Hand tools will automatically give you a very slightly rounded belly...almost imperceptibly so.They work best that way.
Once I string a bow for the first time I generally use only hand tools.
Jawge
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You can bow your scraper and make the belly as flat as you like. Remember that flat tools make curved surfaces and curved blades make flat surfaces.
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I don't make flat bellied bows. I'll be honest. I don't like them as well. I don't need them. No offense meant, but they just seem 'incomplete' to me. So, all of mine are radiused to varying degrees. The abilities of the wood determine the bow's width & legnth, and the width largely determines the degree of radius in the crossection... i.e. how 'squished' the radius is. I have made fully radiused bows with minimal set, with woods that others would absolutely make flat as a board. It can be a fine line, and you have to want to avoid the flatness, and push limits to learn what's possible... and it turns out much is possible ;)
I would also rather have a bow a couple inches longer than flat. A bow with a shorter stiff handle section than flat... or NO stiff handle section than flat. In most designs, there are ways to work around flatness with virtually any wood.
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Dances with squirrels, what's the structural advantage of a radiused belly......or do you just like the aesthetics of it?
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My opinion is that a flat belly is usually better. For myself I like a slight radius just because I prefer to work a bow that way. There very well could be advantages to a radius belly because of the "poisen effect" I know I spelled that wrong. I have no idea how it would work but it possibly could have some effect.
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Drewster, I dont know whether there's a structural advantage or not. I'm guessing it's give and take... a compromise of sorts. Going from thin and flat to round makes a spring or lever stiffer and stronger, or equally as strong with less material, but going from round to thin and flat means it can bend farther without breaking. Most of my bows would be defined as flatbows, but are of such a cross-section as to perhaps share some structural qualities of each of the above.
I make them that way mostly because of how they look, but there are a few advantages and preferences when it comes to tool application, tillering techniques, and how they're better suited to some of the bows I prefer, like really snakey or odd shaped osage bows.
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I have been under the impression that as far as the physics of bows goes that a flat belly is technically superior, however I'm thinking there is a safety factor to rounding out your edges slightly.
I also thing that a flat belly is inferior on osage bows and now strive for a rounded belly on every bow to prevent the water fall effect of going through growth rings on the belly.
If I was to go make a white wood bow right now I'd shoot for a flat belly. Osage- rounded
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I did several experiemnts over the past few years with very wide very flat osage bows. Maybe 1/2 dozen. Like 1 3/4 to 2" wide. My plan was to reduce width as I went to get them down to a proper mass. Some of these were backed osage and some self bows. I was really shocked at how thin they wound up and how low in mass they came out inspite of being wide. Contradicts my own theory at some levels unless we are doing more damage to the wood cells than previously thought that is not showing up in set. Every one of them was a very good performer. I tend to believe that osage is very tolerant but still taking some damage at comonly accepted demensions most of us presently use.
I worked on one last week that didn't respond like this but moisture turned out to be too high, much higher than I expected.
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In Adam Karpowzi's book he explains about optimal cross sections with regard to the poisson effect. The Turkish hornbows that the book deals with are made with a flat back and rounded belly, of course this is linked into the materials used and maybe not so applicable to wood only bows.
Personally on a self bow i prefer a little radius dependant on wood used mainly for ease of using hand tools and wandery grain etc.
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I like them pretty flat, like Mike said as flat as I can with hand tools, just slightly rounded is the way the usually turn out. With Osage/black locus or any think ringed wood you can run into trouble if the rings are large with the ripple effect where the grain run out but I have learned over the years how to work the scrapper to eliminate that so it's not much of a problem for me. :) I do think they look better to me a little rounded but I rarely do anything just for look. ;)
Pappy
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It isn't JUST for looks if a good bow results ;)
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I like mostly flat, but certainly nothing like if you'd used a belt sander. As close as I can get without bowing the scraper like Pat mentioned is close enough for me. Alternatively I do enjoy a slightly concave look, though my staves are all too flat ringed for a true hallow limb design.
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It isn't JUST for looks if a good bow results ;)
Exactly. You cant just like flat or round bellies and do 'em all that way. Wait, I suppose you could, but you'd be missing the boat and the good fishing.
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Someone on the site has been working with hollow limb designs where the belly is concave to follow a growth ring on a high crowned stave. You should check that thread out. I'll be trying one with my next high crowned stave.
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what jawge and badger said,, I too think the wide flat osage can be efficient,, and I like that design,, I dont think it is always the best design,, but worth a try if you have not experimented with it,, i really like it on sinew backed osage,, my bows are not totally flat either,, just kinda flat :)
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It isn't JUST for looks if a good bow results ;)
it can be but so can flat. ;) back at ya. :)
Pappy
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Thanks for all the replies. It's looking like flat"ish" is usually preferred. Is there a time when a curved belly will produce a better bow?