buttressed yew

[Jodocus]

Ok, I got that "buttressed" from a dictionary, hope it's the right word. I have a piece of yew that's nicely straight, but it has a concave back, as yew often does.

"decrown" it flat? or not use for a bow?

[wizardgoat]

Ive heard bad things about concave backs, lets see a pic though.
Id probably opt to flatten it out as much as i could

[mikekeswick]

It's not a problem to reduce the edges into a more convex 'normal' shape. Just follow the rules of de-crowning eg. leave parallel lines and then you  haven't violated any fibres.
It may work out if left concave but I've had a bow break that was left like that - i'll never do it again!

[blackhawk]

Ah..."riding the rails" is what some of us call that because all the tension will ride on the edges. Let's see a pic of how bad it is.  If its severe then something will need to be done...but if its not that bad it could be OK. Lucky for you its yew and it can be violated some,and you can flatten it down some following the grain like you should when Decrowning. I've seen folks also sinew the concave area building it up to where it rises above the edges.

[Del the cat]

It's called "character" 
just charge yourself twice as much for the finished bow
I've had a few staves with concave features on the back... I like the look of 'em and it's somewhere to rub your thumb whilst contemplating whatever it is we contemplate.... mind it depends how severe it is.
Del