Yachting Monthly — November 2017

November 2017 http://www.yachtingmonthly.com 73

Conclusion

It might be easy to think that if three strand is stronger

once you’ve tied a knot in it, you should ditch the rest.

Sadly it’s not that easy, as one should always consider

the creep, or elongation characteristics, of a rope

before choosing it for an application. For mooring

ropes a lot of elasticity is desirable to reduce the snatch

loading on the boat and her fittings; for halyards and

sheets elongation should be reduced to a minimum.

While tying a bowline in my new Dyneema sheets

will have reduced their break load to less than 40% of

their original strength, it has to be seen in context. My

sheets are 12mm with a break load of over 6000kg, by

tying the bowline it would reduced this to, say, 2400kg.

My winches have a safe working load of 850kg.

All the knots we tested reduced a rope’s strength by

at least 19%, most by two or three times that amount.

As the majority of knots were developed in the times

of three strand, it is no surprise that all the knots tested

fared well in three strand: only the reef knot and sheet

bend reduced the rope's break load by over 50%. On

average it retained over 60% of its strength.

What was curious was the best knots for three

strand, were the weakest for the D2 Racing, and the

strongest for the D2 were the weakest in three strand.

The difference between tying the best and the worst

knots in Marlowbraid, when attaching it to a shackle

could cost 20% of the rope’s break load. In all the other

ropes tested it was at least 10%. I would have loved,

at the end of all this

testing, to have been able

to say ‘learn this knot,

it’s the best’, but what

works well in one type

of rope, failed first in

others. Remember that a

buntline hitch is best for

three strand, but comes

out in the bottom two for

all other lines tested.

However, the scaffold

knot was consistently

in the top two, so if it’s

not in your repertoire it might be worth adding – if you

know a fisherman’s knot you just have to remember to

add an extra turn.

Tie a bowline in D2 Racing and you’ll have lost

12% more of the rope’s strength than if you’d have

used a figure of eight loop. Thankfully with the other

loops/ropes there is only between 5-7% (150-200kg)

difference between knot choice. So it’s worth thinking

how close to the limit the loads on your cordage will

be working at. I’d suggest that worrying about a 5-7%

strength loss with a bowline, for the most part, can be

forgotten about as fatigue, UV degradation and chafe

all affect the rope’s strength. If you can remember to tie

a Yosemite bowline in braided line, you’ll be getting the

best from that rope.

Joining three strand rope together, threw up an

unexpected winner, the blood knot, which retained

over 80% of the rope’s strength. The fisherman’s knot

managed 65%. Again if you don’t know the fisherman’s

knot it’s an easy knot to learn and by adding an extra

turn can be made into the scaffold knot.

Blood Knot

Usually tied in monofilament fishing line, the blood knot is
simple to remember, but cumbersome to tie in rope – it’s easy
to underestimate the amount of line needed to wrap each end
around the other five times. Unless load is added, or the loose
end secured in some way before tensioning, it can undo. Of all
the knots tested it retained over 80% of the rope’s strength.

Reef Knot

Left over right, right over left, the reef knot is easy to tie and
undo. Sometimes it can shake free if not loaded. At 200kg the
knot started slipping, and continued to slip until it pulled through.

Zeppelin Bend

Made by interlinking two overhand knots, the zeppelin bend is
more secure than either sheet bends. It's more suitable for tying
lines that come under irregular loading, such as a mooring line in
rough weather. Failed at the same load as bowline to bowline.

2640 2120 80.3

2640 1210 45.8

2640 1380 52.3

The scaffold knot

was consistently in

the top two, so if

it’s not in your

repertoire it might

be worth adding

Which knot is strongest? Technical

Rope Break

Load (kg)

Knot Break

Load (kg)

% Strength

retained

Rope Break

Load (kg)

Knot Break

Load (kg)

% Strength

retained

Rope Break

Load (kg)

Knot Break

Load (kg)

% Strength

retained