as a rule of thumb ,how much poundage does a bow increase or decrease per inch??

Depending on your draw length, a rule of 2.5-3# per inch is my experience.

Mike

Depends a lot on the bow.  Early in the draw you might see 2-3#, later it might be 4-6#/inch.  But for a static recurve, those can be reversed.  For a rally long bow, it might never increase until way past normal draw lengths.  I always assume 3#/inch until the last 3 inches and then I say 4# for a straight-limbed longbow.

I draw my longbows 30" (give or take a fraction depending on the thickness or shape of the handle)

I've noticed that my lighter bows do not increase as much per inch passed 28" as my heavier bows with limbs of the same length.

I am assuming therefore that bows go up by a percentage of their poundage every inch (to their reasonable limit) rather than at a fixed poundage increase for all bows.

Am I correct? I've never done any tests or tried  bows other than my own. I've wondered about that before.