my bow is twiasting

[kdub]

I recently noticed that my 62 @28lb  68inch hickory longbow has developed a slight twist in the upper limb. I havent noticed any change in the preformance  of the bow.  The twist was barely niticeable by the naked eye, but when placed against a flat surface the upper limb sits about 1/2-3/4 of an inch highe than the lower limb.   I am new to the self bow thing, so here are some of my questions of which your answers will be greatly appreciated.
Whats wrong with my bow?
What caused it?
Is it going to get worse?
I know this would be easier if I could post a photo but I cant.
Thanks for any input.

[Dano]

It's made of wood

[kdub]

ok so this is just what happens?  Ive been practicing with it ALOT.  Ive never dry fired it or held back for a long priod of time, its been treated good, but used well for the last year.

[radius]

i have a hickory self bow that's doing something similar, twisting...it's rift sawn, and i think the direction of the grain may have something to do with it...hasn't hurt the bow's performance at all

[DanaM]

sounds like some set set im rather than prop twist, could be from too much moisture hickory likes it dry.
Like ya say a picture would help. My advice is to shoot it an have fun

[TRACY]

I have a hickory selfbow that has some propellar to it and it shoots fine.