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Message: <blockquote data-quote="Cleon" data-source="post: 8142224" data-attributes="member: 57383">Yes, DC 17 seems way too low for a 5E hemp rope.  That suggests an "average humanoid" with Strength 10 has a 20% chance of snapping the rope just by yanking on it with all their power.Would you risk hanging from a cliff by a rope with a 20% chance of failure?Well while "researching" for rope data I wandered into checking on silk fibres since "rope, silk" is a standard SRD equipment item.Here's the base stats:Rope, Silk, 50 ft. (3/3.5/Pathfinder): This rope has 4 hit points and can be burst with a DC 24 Strength check. Price 10 gp, Weight 5 lb.<a href="https://www.d20pfsrd.com/equipmenT/goods-and-services/hunting-camping-survival-gear/#TOC-Rope" target="_blank">Rope, Spider's Silk</a> (Pathfinder): This rope has 6 hit points and can be burst with a DC 25 Strength check. Price 100 gp, Weight 4 lb.First ApproachUsing the "Break DCs vs Strength/Carrying Capacity" method.Silk Rope: Break DC 24 => safe Strength bonus +13 => Str 36-37 => max lift 3,680 or 4,160 lb. => max load 7,360 or 8,320 lb.Spider's Silk Rope: Break DC 25=> safe Strength bonus +14 => Str 38-39 => max lift 4,800 or 5,600 lb. => max load 9,600 or 11,200 lb.Rounding that to a convenient number, that suggests a regular silk rope has a breaking load of 7,800 pounds and a spider's silk rope 10,500 pounds.  Assuming a "safe load" ratio of 1:6 that's 1,300 pounds for silk rope and 1,750 lb. for spider's silk rope.A standard silk rope is probably made from regular insect silk (as in the stuff spun by silk moth larvae), while a spider's silk rope is specifically stated to be made from the silk of <a href="https://www.d20srd.org/srd/monsters/monstrousSpider.htm" target="_blank">Monstrous Spiders</a>. Possibly very big ones, since a Gargantuan Monstrous Spider's web only has a Break DC of 24. Then again, that Break DC may represent a single strand that "is strong enough to support the spider and one creature of the same size" and according to the <a href="https://www.d20srd.org/srd/combat/movementPositionAndDistance.htm#bigandLittleCreaturesInCombat" target="_blank">Creature Size and Scale</a> table that's a minimum of 32 tons or 64,000 pounds (since 3E uses US short tons).More likely it's a silk strand from a Large Monstrous Spider as the standard weight range of a Large creature is 500-4,000 pounds, so a "safe load" of 1,750 lbs. falls within that range.  A Large spider's web has a Break DC of 17 however.  Possibly a Monstrous Spider web is easier to break than a single "support strand" because it's a collection of thin strands which can be snapped individually rather than a single large one.A spider's silk rope could be made from hundreds of strands of silk from a Small or Tiny spider braided together like a normal hempen rope rather than a single strand from a Large one, if only because smaller Monstrous Spiders would be a lot easier and safer to keep "domesticated" than massive ones.I guess it's possible the +7 difference between a Large Spider's Break DC 17 web and a Break DC 24 spider's silk rope is because the rope has been specially treated for strength and durability - some kind of secret drow alchemical mixture perchance? It'd explain why the stuff costs 100 gold pieces!Also, a Large Monstrous Spider's web has 12 hit points per 5-foot section, twice the 6 hp of a spider's silk rope so maybe whatever treatment is used to turn their silk into rope makes it stronger but less durable?  Or it just uses half the silk of a 5 ft. by 5 ft. stretch of Large spider webbing.  A Medium Monstrous Spider's web has 6 hit points per 5 ft. section, for what it's worth.Hmm, I seem to be wandering off the issue…Second ApproachMy best guess is <a href="https://en.wikipedia.org/wiki/Spider_silk" target="_blank">spider silk</a> rope should have approximately the same strength as high quality nylon rope, but the strongest known spider silks such as that from <a href="https://en.wikipedia.org/wiki/Darwin%27s_bark_spider" target="_blank">Darwin's bark spider</a> (Caerostris darwini) are approximately twice as strong (up to 10 times stronger than kevlar!), so should produce a rope roughly twice as strong as nylon.It's important to note that claims of a fibre being "X times stronger than steel/kevlar/whatever" are often deceptive, since they're usually for microscopic perfect fibres. An actual rope is only as strong as its weakest point, and will contain millions of individual fibres, many of which are weak, flawed or poorly bound to their neighbours, meaning the rope's breaking strength will be a lot less than the maximum theoretical strength of the material.Regular silk from insect cocoons and the like is typically not as strong as spider silk, and can be much weaker depending on how the silk is harvested/spun and what particular insect it's from. I'll assume that regular silk ropes are made from the strongest varieties such as the standard silk of Mulberry silkworm cocoons from the <a href="https://en.wikipedia.org/wiki/Bombyx_mori" target="_blank">silk moth</a> (Bombyx mori) which is 50% to 60% spider strength.Okay, so a regular silk rope is 10 feet long per pound (or 0.1 lbs. per foot).  That's 148.9 grammes per metre.  A spider's silk rope is 12.5 feet long per pound (or 0.08 lbs. per foot). That's 119.1 grammes per metre.According to Engineering Toolbox data on <a href="https://www.engineeringtoolbox.com/nylon-rope-strength-d_1513.html" target="_blank">Nylon Rope Strength</a>:A 16mm diameter nylon rope weighs 147 g/m and has a minimum breaking strength of 8,910 pounds.A 14mm diameter nylon rope weighs 119 g/m and has a minimum breaking strength of 7,200 pounds.So, if silkworm silk were 60% as strong as nylon, its minimum breaking strength ought to be 0.6 times the the breaking strength of 16mm nylon rope which'll be… 5,346 pounds, or approximately the same strength as the standard hempen rope.If a spider's silk rope is as strong as nylon, its minimum breaking strength is 7,200 pounds.Those figures seem a bit low.  However, those are minimum breaking strength, and good engineering conduct is to include a healthy safety factor.  The average breaking load could be noticeably higher.According <a href="https://www.smackdock.co.uk/rope.htm" target="_blank">Smackdock</a> Average Rope Breaking Loads:A 16mm diameter three-strand nylon rope has an average breaking load of 6,640 kg (14,625 pounds).A 14mm diameter three-strand nylon rope has an average breaking load of 5,100 kg (11,233 pounds).Using the above:60% of 5,100 kg would translate to a standard silk rope having a breaking load of 8,775 pounds.50% of 5,100 kg would translate to a standard silk rope having a breaking load of 7,313 pounds.And a standard spider's silk rope having a breaking load of 11,233 pounds.Those figures are reasonably close to the First Approach's breaking loads of 7,800 lb. for silk ropes and 10,500 lb. for spider's silk ropes.Silk's a bit denser than nylon (mulberry silk's typically 1.35 g/cm³, spider's dragline silk 1.31 g/cm³, nylon 6.6 is 1.15 g/cm³). That doesn't make a difference to our Strength calculation, but might affect the actual thickness of the rope.All things being equal, the rope's diameter will be that of the equivalent nylon rope times the square root of the density ratio (nylon density divided by silk density).Silk Rope: 16 mm × square root (1.15/1.35) = 14.77 mm => roughly 6/10th of an inch.Spider's Silk Rope: 14 mm × square root (1.15/1.31) = 13.11 mm => roughly 1/2 of an inch.However, a silk rope could be "fluffier" than a nylon rope with more airspace between its fibres.  I don't really know, since I couldn't find any data on actual silk ropes.This might be because a real-like silk rope would be much more vulnerable to abrasion damage than a nylon rope.  Since individual silk fibres are so thin, it'll take very little to break one and a silk rope (in theory) might fray very easily when it rubs again something (including itself at points where it's knotted).  A Monstrous Spider silk rope presumably would not suffer from this problem as its fibres would be much thicker than a regular Fine-size spider's.As for a standard silk rope, maybe it's made from the cocoons of Giant Silkmoths the size of pigeons rather than regular sized insects? Considering the abundance of giant insects in D&D, Giant Silkworms are definitely a possibility and would be a simple answer to the abrasion problem.Or silk rope is only used for a few days or weeks and chucked away or unwoven and used for regular fabric as soon as it becomes too worn to be safely used.  That seems rather profligate, but adventurers tend to have money to burn.ConclusionRounding to some convenient numbers:The SRD standard silk rope is a 9/16th inch diameter silkworm silk rope (possibly from Giant Mulberrry Silkmoths) that can support 1,300 pounds safely, or up to 3,900 lbs with an increasing risk of it breaking.The Pathfinder spider's silk rope is a 1/2 inch diameter Monstrous Spider silk rope that can support 1,800 pounds safely, or up to 5,400 lbs with an increasing risk of it breaking.</blockquote>

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