maybe something close to 30 degree's will help with cutting ropes, i do mine at 20 cause i cut alot of meet with them...my carry knife i do at about 24, it is usually used to cut corn sacks, rope, zip ties, holes in the ear for a tag, open mail or what ever.
if ya like shaving with it go fer 18 er so. it isnt good for the edge to cut rope though, makes it to dull to shave with, but will cut rope fer a good while. good luck