| Blueluck |
First, I'd talk to your GM about tying people up with chains instead of rope. If the GM likes this idea, get a chain, or adamantine chain.
Have your rope enhanced with a bonus to your favorite applicable skill. This strengthens the item.
* Add +2 hardness for each +1 enhancement bonus of magic items.
* Add 10 hp for each +1 enhancement bonus of magic items.
Enchanting with a skill bonus isn't very expensive. 5,000 gold for a +5, for example. (bonus * bonus * 100 * 2)
Rope
hardness 0, hit points 2, burst DC 23
Rope of Climb +5
hardness 10, hit points 52, burst DC ??
Iron or steel chain
hardness 10, hit points 5, burst DC 26
Iron or steel chain, Climb +5
hardness 20, hit points 55, burst DC ??
Adamantine chain
hardness 20, hit points 10?, burst DC ??
Adamantine chain, Climb +5
hardness 30, hit points 60?, burst DC ??
| MacGurcules |
The tensile strength of an object of any given material is roughly linear with cross section. So two lengths of rope will hold more or less double what a single length will. Possible overhead press weight seems to double every five points of strength. So each time you double your rope over, you increase the burst DC by about 2.5.
Really, though, I gotta feel like this kind of thing is covered in the grappling Tie Up mechanics already. Instead of making you speculate on the strength of various chains or count how many times you wind a rope around somebody, they just handle the whole thing with a CMB check.