2.5 X 1.572 X 900 = 5, 546 pounds of breaking strength
"Knots and splices will reduce the breaking strength of a line by as much as 50 to 60 percent. The weakest point in the line is the knot or slice, but a splice is stronger than a knot."
Walk down the docks at any given time and take a gander at how the various boats are secured...
Now you have your yachties- the weekend (if that), warriors whose fiberglass boats are docked 90% of the year. The main issue with these vessels are that they have all sorts of expensive braided synthetic lines to moor the craft with, but usually are all run from the same hawse hole to the same cleat. (Same spots orignating and terminating)...So, if there is going to be a failure, what makes them think that doubling up is going to work? (and that is really not "doubling up")
Now, the fishing fleet, (big sturdy lines made fast in varying terminating points) - the common problem is thus: [see photo to left]. Most fishermen are reluctant to drop any money on their boats or gear until they absolutely positively have to do so....resulting in frayed dock lines and bulwarks that are rusting or rotting away. This puts the tension on the weakest link in the chain, so to speak.
[the best part of this photo is that the line that looks as if it is two lines doubled, is actually the same line wrapped twice... So when it frays through, the entire moorage point is a lost cause!]
The boat next to us has three of the five dock lines abraded away to almost nothing. I wish I had a formula for what the breaking strength of a synthetic line is when it gets to THAT point... not good I wager.
Having seen a 3/4" line snap under strain (and been fortunate enough to not witness the cleat come flying overhead-- I put great stock in correctly and safely tying vessels correctly to the dock.
On the other hand, there haven't been any runaways in the marina this year....yet.