Rope Strength

[mehs]

How much weight can the ropes in pathfinder bare? They have strength check DC for bursting the rope, but nothing that translates into weight

[Geddy2112]

Disclaimer: not RAW, just my 2 coppers

If a rope has a break DC that is strength based, then the rope would be able to carry the weight as if its strength was one lower. So if it has a break DC of 23, it has 22 strength for what it can support. A max heavy load is 520lbs. If you are going for absolute strength, 22 strength can lift 1040 off the ground but only stagger around with it. So at very max, the rope could support this much material but it would be at the breaking point and more than 5ft of movement a round would likely break it.

I would also say that it would have to be a sufficient length of rope and the load secured properly. A character with gear weighing 450 lbs should be able to climb a secured DC22 rope without issue. If a 23 DC rope is secured to 1000lbs of cargo in a ship it would need a proper rope net and even then it is pushing the safe limits of the rope.

[The Kool]

Expanding on your numbers a bit, assuming we're using your break DC - rope strength relation, and comparing to some actual tables I found. I'm going to adjust the numbers a bit. The breaking point (tensile strength) of a rope of DC 23 would be... let's call it 23 strength, meaning when a pull of that force is exerted it breaks. A character of 23 strength can drag as much as 3,000 lbs under normal conditions. I'm aware that hemp rope is the example given but I don't have stats on that, so looking at manila rope. 3,000lbs tensile strength correlates with just over 1/2 inch diameter, which sounds entirely reasonable. It's worth noting that the safe working load is significantly lower, sometimes as low as 10% the tensile strength. If you want to introduce some realism, you could have the rope be weakened if it is overloaded, or require heavier loads to be secured better. In the case of the 9/16" manila rope I'm comparing to, the safe working load is 388 lbs, or just shy of a Heavy load for a character with 23 strength. Fancy that. Fall down into the light load category and it could be lightly secured, go up into the heavy load category and you need to secure it extra well.

We should be able to take these numbers to other ropes, so let's look at two more: Spider Silk (DC 25) and Bloodvine (DC 30). By our method, the Spider's Silk rope has a tensile strength of 4,000lbs and a safe moderate working load of 533lbs, which correlates to a slightly thinner Nylon rope than our Manila example (and, much like comparing those two actual ropes (having worked with them both myself), is more flexible and smooth). The Bloodvine rope has a tensile strength of 8,000lbs and a safe moderate working load of about 1,000lbs (comparable to a nylon rope about 5/8" diameter). It's worth noting that the material differences in terms of strength may be significantly different in D&D than in real life, leading to the actual dimensions of the spider's silk and bloodvine ropes being notably thinner if you so choose. When it comes to working loads, you can actually increase the safe working load by simply doubling the rope back against itself. If the 1500lbs is being held by two ropes (given they're secured competently) then each is only under a strain of 750lbs.

So I hope I've shown this system has realism, and the numbers seem to be fair. It's easy to see why a player might want a block and tackle setup now, as a block and tackle makes it incredibly easy to lift greater weights by evenly splitting the load between several ropes, in addition to the pulley benefits. I advise that if this is to be a relevant element that you expand a bit on the shelf-bought options seen in the SRD. Shorter and longer ropes should be entirely reasonable purchases, as well as thinner and thicker ropes for lower and higher DCs. Sure, your thin rope may have a break DC of only 16, but it's only 3/8" thick and can securely hold well over 100lbs, is dirt cheap, and is nice and light. Similarly, a large ship may have dock lines that are 2" thick with a break DC of 40 or more.

TL;DR: The break DC is the rope's Strength. The max it could drag (5x max carry weight) is the breaking point. Medium load limit is comfortable working strength, with light/heavy being less/more securing required.

[Psyren]

+1 approximating it using the break DC, corresponding strength score, and corresponding max load.