Crown a concave back?

[Stickhead]

I have this unusual 20 yr old Osage stave, 64" long.  The good news is that it has excellent growth rings, the grain is pretty straight, and it has about 5" of natural reflex.  The not-so-good news is that it has a bit of twist on one end (I'll heat that out), and it has this groove running down most of the length, giving the back a concave shaped cross-section.  I've never seen a concave-back bow, and I'm assuming that would be a bad thing.

I went ahead and chased the first heartwood ring (which was painstaking), just to see what was lurking under there, but I may not stick with that ring for a back. 

I was considering "crowning" it to give it more of a D-shape than a C-shape cross section.  By crowning, I mean just the opposite of decrowning, whereby I'd leave extra rings toward the center, and shave off rings toward the edges.  If I did this, I'd make that groove be the centerline of the bow, and vertical lines would appear down the length of the bow, exposing older growth rings towards the edges.  Anybody ever do this?

Another thought was to just flatten the back and back it with bamboo or something.

Any opinions?

...Tom

belly-up pic:

[Jim Davis]

The only issue I see with that concavity is that it is not centered. Could end up with a dip on one edge and not on the other.

Looks like if you were to drop down 4 rings or so, the issue would be gone. There is no way I would crown or flatten the back.

[bradsmith2010]

looks like you could go down a few rings and it would not be an issue, Jim I was posting same time as you

[bownarra]

I've seen it once before. Years ago I got a stave like that, it was full of 'character' as well as the concave back....It was my first and so far only osage bow that has blown on me. It went on the 'edges' of the concavity. I wasn't very experienced when I made that bow so take it for what it's worth.
The raised edges would be more strained on a bow with a concave back however I'm sure if the limits weren't being pushed it could be done.
I would also be tempted to go down a few rings if I had to make a totally dependable/durable bow from this stave. On the other hand it is also something fairly rare to have a play with. You certainly could go with your plan to crown the back. All you need to make sure of is that the exposed rings are parallel, no dips etc. As long as the fibers aren't 'dipped' through then I see no problems arising. 

[PatM]

There's some  Victorian era longbows with a concave groove in the back.  Maurice Thompson also had a prized  Hickory backed Snakewood with  the same feature.  Not sure if it was made by the same maker.

 eta:  Here's a(broken) link to the examples.   https://w ww.bow-international.com/features/bow-history-the-story-of-peter-muir/
 

[HH~]

Cut in half and find another piece and make billet bow with it.
Maybe not in half but enough to make one good 35-37” billet.

They do get tons of stress on outer edges when ya have a trench like that. They seem to usually lift a splinter from edge over time shooting.

Go down four big rings on that stave there is not much left.

HH~

[Stickhead]

There's some  Victorian era longbows with a concave groove in the back.  Maurice Thompson also had a prized  Hickory backed Snakewood with  the same feature.  Not sure if it was made by the same maker.

 eta:  Here's a(broken) link to the examples.   https://w ww.bow-international.com/features/bow-history-the-story-of-peter-muir/

Very cool article, Pat.  Thanks for sharing that.

I might have enough wood to go down a few rings.  I may have to build up the handle, but that’s okay.  Sure would like to keep this stave in one piece if I can.  Kinda keen on using that natural reflex.

[HH~]

Some of the best shooting bows I have came off unmatched scrap wood laying around the barn floor and billeted up. I like to think that was just luck but after speaking to Gary D years ago about billet bows, he convinced me. He was very much correct. They as good or better than a one piece "easier to get two clean billets than a clean stave".

I have done a bunch staves with Vee Trenches and crowned on other side. They shoot good for awhile but at 62" GTG with 27-28" draw length that puppy gonna take a pounding. They all have a shelf life. Some years, some days, some hours.

Had that exact setup you have there but in a 70". Shot thousand s of bullets out of it! Took it down to Terry's HH shoot last year. Took it out of truck, let it acclimate a bit, strung it up, exercised it twice and "tic" right on edge of a center trench on lower limb. Had a 6" spike hanging off! Unstrung it wrapped it with thread, super glued it and shot the tournament.

That Bow is now "half a holler" which laid down a monster score at the 2021 Pre Spring Fling. So, If I think back. . . .  I should have just cut that stave in HALF kept the Crowned Billet and Half a Holler would have been a Silver or Gold three years earlier and I wouldn't of been sucking my thumb at that big shoot in Bama last year.

Hedge

[George Tsoukalas]

Just leave it and make a bow. I've worked staves with troughs. Jawge

[Hamish]

+1 with George.

  No bigge, just use a pair of calipers to make sure you aren't leaving a weak spot along the length.

Osage is incredibly tolerant of minor flaws anyway.

[George Tsoukalas]

You can still heat it as needed and move some wood.
How long would it be if you cut that reflexed part in the foreground.
Jawge

[HH~]

Cut a primo billet and make a bow that will last half a million shots. I may have a orphan billet that would match that grain ratio on that stave.

Do more makin and a lot less breakin. Then again if ya need a challenge test....

HH

[Del the cat]

Just leave it and make a bow. I've worked staves with troughs. Jawge

+2.
I've worked plenty of Yew with concave areas on the back... I like 'em, it's character... don't see why it should be an issue.
You could just as well argue that a convex stave has too much strain in middle...
Del

[HH~]

You could but with Hedge it just dont work that way. If the Vee is center well and near the tip OK. Get it near the working part of limb it will last awhile look nice on the bow rack, Yep, will fill yer challege on fix but over time it'll fail on the the edge. So, what im saying is cut that dirty ol path of woe short and just make a shooter from the giddy up and have it around a bit. If you want to shoot it alot, hunt it.

HH~

[Stickhead]

You can still heat it as needed and move some wood.
How long would it be if you cut that reflexed part in the foreground.
Jawge

I don’t think shortening the bow is an option.  That groove is pretty deep for most of the length is the stave.  I’m thinking I’ll compromise and go down a few rings to get it a little flatter, then have at it.