Please excuse me if I get some terminologies wrong.

I'm not sure if Ash is a good wood for a bow.  It seems like it would be too stiff.  I haven't been to Primitive Archer in a while, so I dunno if its true or not.

You want a good mix of flexibility and stiffness for a bow.  That's why osage and yew and even hickory make good bows.  I think Ash may even be too heavy for arrows.

ash isnt the best choice for a bow
but it will make a good bow if the right piece of wood is chosen

im guessing this is in board form
if so you want it to be quarter sawn lumber with little to no run off from end to end

as far as thickness goes every two pieces of wood of the same species of tree made in to identical bows
will have slightly different demensions

this because growth ring thickness varies
the same growth ring can be thicker or thinner in different areas in the circumference of the tree
not to mention from top to bottom its going to be thicker/thinner also

the current osage bow i am making is only about 62" long and the difference from end to end in the thickness of the same growth ring is quit noticeable
there for to get the limbs to bend evenly the limb thickness varies from one limb to the other

for the best advise on making a self bow i recomend either getting the TRADITONAL BOWYERS BIBLE series of books,or go to PALEO PLANET . COM
some of the best bow makers in the world are there

as far as your cherry bow being to stiff,could have been
bu that is very common to have happen for cherry when making a self bow
cherry is not that great of a bow wood for some reason
the old adage of "if it has thornsor grows fruit or nuts it will make a good bow" doesnt apply to cherry

I use ash for arrows, my bows are or were always maple or yew...

ash is very stiff

all good bow woods are stiff
what matters is how well it can handle compression and tension
also the specific gravity of the wood helps to determine if its a good bow wood
woods with low sg dont make good bow woods,nor do woods that cant handle tension and compression

Ash is frequently used for the riser and siyahs (rigid limb tips) on Asian-style bows. My Istvan Toth Magard bow has ash siyahs.