rounded belly or flat

[bsv]

I will be building my first self bow of osage,all winter I have been reading and watching all the videos I can watch, I have Ryan Gill's book ,Clay Hayes'S book,and Dean Torges's book,and Gary Davis's DVD.and all the you tube vids I could watch...I received a Very Clean osage stave for christmas my wife got from Carson Brown.All the info I have gathered from here and all the above,along with other sites,most say flat back except Mr. Torges,I would like to know what you think..I will be taking pieces from all my research and I will make it work for me.THE BUG HAS BITTEN ME..I am leaning towards Mr. Torges it make sense to me.. Thanks Burt     

[Roy from Pa]

Good wood, flat belly.

Mediocre wood, round belly.

But you can do a round belly on good wood because it looks cool.

Basically how you want your bow to look.

[bsv]

Good wood, flat belly.

Mediocre wood, round belly.

But you can do a round belly on good wood because it looks cool.

Basically how you want your bow to look.

Thanks Roy

[Bowjunkie]

Any half decent bow wood can make a bow with a fully radiused belly, you just have to coordinate other design aspects accordingly. They're actually better in some ways than flat bellies. If you read Dean's writings on it, you already heard about it.

I like all of my bow bellies radiused, never had a problem with it, and will never do it any other way.

[Pat B]

With a radiused belly all of the compression stresses are concentrated down the crown(center) of the belly. Osage and handle these stresses well. I always use a radiused belly on an osage stave selfbow.

[Bowjunkie]

"With a radiused belly all of the compression stresses are concentrated down the crown(center) of the belly."

This is not true. Not even close.

[Bowjunkie]

I shouldn't say I'd NEVER do it any other way.... since when I make bows with very small diameter staves and highly crowned backs, the bellies are more flat... still slightly radiused, but they could pass for flat at a glance. This is done to maintain lateral stability.

Any other bow, the degree of radius is figured in, coordinated with wood type, quality of the piece, and all other aspects of design. Even with the best wood, it could be a more shallow radius on a short highly stressed design, or very deep like an ELB. Lesser bow woods are made correspondingly wider and/or longer, and so the radius may be inherently squashed down, still a full radius, no flat area on the belly at all, the limb is just made wider and thinner. If you're gonna try to convince me all, or even most, of the compression stress on a 1 3/4 wide radiused belly of a limb 3/8 thick is right down the center? Well, lol, good luck with that.

[Eric Krewson]

I have made over 150 radius belled bows, sometimes the radius is hard to see and almost flat, particularly in wider hickory bows.

I like narrow, sleek, osage bows, 1 1/4" wide with skinny tips, a radius belly is just right for this design.

[bsv]

Thanks everyone it's radius for me..Any pic's would be very helpful. Burt

[Roy from Pa]

This is what a cross section of my bows look like.



Slight radius on this bow.

[kevsuperg]

From the few selfbows I've made the back usually has a slight crown. If you flatten that you'll most likely violate growth rings and have to back it with something.
  Hope this helps. Trying Tapatalk for the first time and can't see the responses so far.
 Good luck Kevin

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[kevsuperg]

Sorry just noticed belly not back. Yes I flatten my belly.  Most of the work is done by the outer limb and the belly is in compression so ring violation isn't as big a deal.
 Check out some of the hollow limb designs ( HLD) folks are doing you'll see what I mean

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[mwosborn]

"With a radiused belly all of the compression stresses are concentrated down the crown(center) of the belly."

This is not true. Not even close.

BowJunkie - would you mind elaborating a little on this?

Are the compression stresses evenly distributed regardless of the amount of radius of the belly?

What would be the advantage of a radiused belly compared to one that just has the edges rounded a little?  Weight?

Just trying to learn here - I have seen many people claim the stresses are more concentrated on a rounded belly.  But to be honest I simply do not know nor have I ever tried testing it. 

[bsv]

this has turned out to be very informative,thanks again, Burt

[Bowjunkie]

Mwosborn, I wouldn't say they're evenly distributed. I suspect there may be more stress at the apex of the arc, but how MUCH more is relative to several factors. Factors we can control in large part.

Fully radiused bellies have no corners to ding, splinter or crack. They make it easier to transition dips into working limb without washboarding, since growth rings taper and fade out over greater length by default than a flat bow in which they end in a line more straight across the width of the limb. The rounded belly shape perfectly lends itself to rounded fadeouts which taper in both width and thickness simultaneously which helps nicely to finesse the dips and keep added on handle pieces from wanting to pop off. The faceted limb shaping and tillering method excels on character bows, those with limbs leaning to and fro, whoopdy-do's and/or snakey osage especially. It's a natural fit where trying to build such bows with flat bellies and flat hand tools is torturous. Radiused bellied bows almost seem to add another helpful dimension.

Here's a good article that delves farther...

http://www.bowyersedge.com/complements.html

[michaelschwister]

I recommend the "flat oval approach" shown in several posts above by Eric, Roy, and many others. The flat belly is in theory superior in a perfect, laboratory, sterile world, and I consider the college grad level design concept.  But, nothing in nature goes purely as theory dictates, as nature is full spectrum variations.  IMHO, the Oval/Torges style is the PHD level/Grand Master design, superior for many practical and functional reasons. It is what is seen on the 10,000 years old plus bows dug from the bogs of northern Europe.  AlsoThe faceted reduction process consistantly results in superior and more visually pleasing bows. Lessons of time and hard knocks point one towards the oval cross section.