weakest link in the tie-down can be the knot you tie, and it is therefore
important to understand a little about various knots and how to tie them
properly. The knot should neither slip nor loosen, and it should be easy to
knot can fail in three ways: it can come undone through vibration and general
movement when there is little load on it, it can pull out when load is applied,
or it can break under load. Any break usually occurs where the rope enters the
ultimate strength of a knot is a matter of design and some knots are naturally
stronger than others. Security, on the other hand, can often be improved by the
manner in which the knot is finished off. But making a knot more secure may also
make it more difficult to undo when the time comes, so there is no point in
making a knot as secure as possible only
as secure as necessary.
US FAA Advisory Circular on aircraft tie-downs recommends the bowline and
the square knot (or reef knot).
suggests that a reef knot is not suitable for aircraft tie-downs. It is an
excellent general-purpose knot for tying two pieces of string or twine (of equal
thickness) together, but it is not a long-term or secure knot, and it is used
mainly in bandaging, tying parcels, etc.
a more secure method of bending two ropes together, use a sheetbend.
sheetbend is the most commonly accepted knot for joining two ropes together and
probably the best, particularly if the ropes are of different sizes.
The thicker rope of the two is used to form a bight, and the thinner rope
is passed up through the bight, around the back of the bight, and then tucked
The knot should be tied with the ends of the ropes coming off the same side of the knot. However it can easily be accidentally tied with the ends coming off opposite sides of the bend, when it is known as the left-handed sheetbend. This version is to be avoided, as it is less secure.
bowline is closely related to the sheetbend.
The bowline is the most useful and one of the simplest ways of putting a
fixed loop in the end of a rope. It is easy to tie and untie, it doesn't slip or
jam, and it has a high breaking strength.
is perhaps the best way to secure a rope to a tie-down ring. It's also very good
for attaching the tie-down rope to the anchors in the ground.
added security, you can finish the knot with a stop knot such as a figure
of eight knot to remove any possibility of the bowline slipping.
a small loop (the direction is important), and pass the free end of the knot up
through the loop, around behind the standing part of the rope, and back down
through the loop.
chant used by many to remember this knot is "The rabbit comes out of the
hole, round the tree, and back down the hole again", where the hole is the
small loop, and the rabbit is the running end of the rope.
the same way that a left-handed sheetbend has the running end of the rope coming
out of the wrong side of the knot, a cowboy bowline is a bowline
that also has the running end of the rope coming out of the wrong side of the
knot. It suffers the same problems
as the left-handed sheetbend, and is to be avoided.
To quickly identify if you have tied a normal bowline or cowboy bowline, check to see that the running end exits the knot on the inside of the loop.
Figure of Eight
single figure of eight is a useful 'stop' knot to
temporarily bulk out the end of a rope or cord. The finished knot looks like its
name. It is useful to temporarily stop the ends of a rope fraying, before it is
double figure of eight knot builds a non-slip loop
at the end of a rope. It is popular with rock climbers (as it is safer than a
bowline) who tie their belay rope to their carabineer or harness.
Tie a single figure eight knot near the end of the rope, loop the end of the rope around the carabineer or harness straps and retrace the figure eight.
Round Turn and Two
turn and two half hitches is used to secure a
rope to a pole or ring, or to start or finish a lashing. It does not jam.
is a good knot for securing a rope to the tiedown ring, and it is commonly used
by many pilots. While it is easy to tie, it can be more difficult to untie,
especially when the rope is wet.
Pass the running end of the rope over the pole or through the ring twice. Then pass the running end over the standing part of rope, and tuck it back up and under itself, forming a half hitch. Repeat this for a second half hitch.
become proficient in the art of tying knots requires practice, but it is a
useful skill. Although there are many hundreds of possible knots, most of us
need only be familiar with a few of the most commonly used ones.
are many books available on the subject. Learning to tie knots using
illustrations can be difficult. Fortunately in this age of technology there is a
better way. There are a number of web sites (particularly those of boy scout
troops) that have animated diagrams to assist in learning to tie a range of
www.troop9.org and click on Knots)
sure that you protect your aircraft adequately with suitable tie-down rope (and a
properly spliced loop in the end of the rope makes tying down easier), and that
you have the requisite knotting skill to make sure the tie-down does its job.
(Article reproduced from Vector)