damo
Well-Known Member
I have been getting quite a few pm's about the Yosemite bowline, so to save any more queries here is what I know.....
It is recommended by the BMC for use by climbers because
a) The knot is usually only loaded during a fall so, because unloaded bowlines tend to work loose, traditionally a stopper knot is tied with the tail. This is bulky, so rethreading the tail is a lot simpler and neater.
b) There is more rope in the knot and the curvatures are reduced slightly, so it is stronger. Without rethreading or using a stopper knot there is a rule of thumb which states that the loose end should be as long as 12 times the circumference for the sake of safety. This is a long length to have flapping about.
From Knot Break Strength vs Rope Break Strength the bowline breaks at about 63% of rope strength, and adding rope by rethreading puts it up to about the same strength as a Figure-of-8 (about 75%).
Interestingly, the variation where the tail emerges on the outside of the knot (Dutch bowline, amongst other names), which is usually not recommended because it is less safe, came out at the same strength.
c) Also because of b) it is easier to undo after a big load.
In the sailing situation I find it reassuring to know that the knot can't come undone, especially as the long tail you would normally have to leave is tucked away.
I also think that when tacking the lack of tail should mean that the genoa sheet is less likely to snag up as it comes across.
If you attach halyards with a knot then you would be advised to whip the tail, which increases the length needed between the sail and the sheave, as does a splice. This version of the bowline gets round that. (Yes, I know there are other knots you can use for halyards, but not if you want to untie them easily)
Anyway, I love the idea of a very simple mod to a traditional usage bringing about an improvement! It would never have been an issue with natural fibres but modern rope materials have much less friction, and it is friction which holds a knot together.
It is recommended by the BMC for use by climbers because
a) The knot is usually only loaded during a fall so, because unloaded bowlines tend to work loose, traditionally a stopper knot is tied with the tail. This is bulky, so rethreading the tail is a lot simpler and neater.
b) There is more rope in the knot and the curvatures are reduced slightly, so it is stronger. Without rethreading or using a stopper knot there is a rule of thumb which states that the loose end should be as long as 12 times the circumference for the sake of safety. This is a long length to have flapping about.
From Knot Break Strength vs Rope Break Strength the bowline breaks at about 63% of rope strength, and adding rope by rethreading puts it up to about the same strength as a Figure-of-8 (about 75%).
Interestingly, the variation where the tail emerges on the outside of the knot (Dutch bowline, amongst other names), which is usually not recommended because it is less safe, came out at the same strength.
c) Also because of b) it is easier to undo after a big load.
In the sailing situation I find it reassuring to know that the knot can't come undone, especially as the long tail you would normally have to leave is tucked away.
I also think that when tacking the lack of tail should mean that the genoa sheet is less likely to snag up as it comes across.
If you attach halyards with a knot then you would be advised to whip the tail, which increases the length needed between the sail and the sheave, as does a splice. This version of the bowline gets round that. (Yes, I know there are other knots you can use for halyards, but not if you want to untie them easily)
Anyway, I love the idea of a very simple mod to a traditional usage bringing about an improvement! It would never have been an issue with natural fibres but modern rope materials have much less friction, and it is friction which holds a knot together.