Smooth Operator
(BluuGnome version of the Fiddlestick)
Pull Cord and Release Considerations
The layout of a rappel and what you choose to use as a pull cord can
have an impact on the safety of using the Smooth Operator.
After the Smooth Operator is rigged and everyone is down the pull line
is pulled on to release the Smooth Operator from the stone knot.
How much force does it take to pull the Smooth Operator out? As
with many things the answer to this is ........ it depends. It
depends on things like how well the stone knot was cinched down, how
much weight was the stone knot weighted to, what kind of Smooth
Operator
are you using, what kind of rope were are using, does the pull and
rappel go over any ledges or around corners and other factors to consider as well.
It is not the intent of this page to explore every possible
combination of variables. This page will explore the force
required to pull the Gnome Gear Smooth Operator from the stone knot
using common rope and the how that may effect your choice of pull
cord or deciding when not to use the Smooth Operator.
It is assumed that those reading this understand the basic concept
and use of the Smooth Operator. If you do not know what a
Smooth Operator is or the basics of how to use it, please read the
information on the main Smooth Operator
page before continuing.
Terms and Procedures
Before moving on lets get some clarity on some of the terms and
procedures used.
Tied for No Twists After Release
The stone knot is a bit deceiving when you try to tie it so it wont
have an twists in it after it releases. It can be tricky and
counter intuitive to achieve a stone knot that will not leave twists
in the rope after it is released. For an explanation of
this see the Stone Knot for Smooth Operator page. All the stone
knots tied for the test on this page were tied so the stone knot
would not leave a twist in the rope when released.
Cinch in the general sense. I cinch the stone
knot around the Smooth Operator the same way I recommend it to be
cinched normally. That is tie the stone knot, pull lightly on
the rope from both directions until the knot begins to tighten
slightly, place your hand over the top of the knot (with the
upper strands running up between your fingers) then pull down on the
top of the knot until the knot cinches tightly around the
Smooth Operator. As you cinch in this manner the knot will tighten
around the stick the roll a little as it situates itself neatly
around the Smooth Operator.
Lazy Cinch
When you see the term Lazy Cinch on this page it means I cinched the
stone using the above method and stopped when the stone knot rolled
into a natural position and visually looked like a neat and tight
knot.
Standard Cinch
When you see the term Standard Cinch on the page it means I made a
Lazy Cinch then pulled down on the top of the knot with more force
to cinch it down even tighter. I tried to stay fairly
consistent when doing this and aimed for an amount of force that
felt like what most people would consider reasonable force to make a
nice tightly cinched knot while in a canyon environment.
Hard Cinch
When you see the term Hard Cinch on the page it means I did a
Standard Cinch then pulled down on the top of the knot using my
entire body weight and bounced on it a little to cinch the stone
knot down very tight.
Middle Strands Straight
It is important to keep the middle strands of the stone knot
straight (not wrapping around the Smooth Operator) when cinching it
down. Keeping the middle strands straight does two things.
It allows the stone knot to untie easily after the Smooth Operator has
been released. Keeping the center strands of the stone knot
straight also allow the stone knot to grip the Smooth Operator more
securely which reduces the risk of the Smooth Operator slipping out.
If the stone knot is tied in the UP position and cinched as
described above the stone knot will fall into the desired
configuration naturally.
When you see the stone knot was tied with the Middle Strands
Straight it also means the stone was tied in the UP position.
Middle Strands Form a Bight
When cinching the stone knot around the Smooth Operator it is important
to prevent the middle strands from bending around the Smooth
Operator
forming a bight. If a bight is allowed to form in the center
strands they can form a bight making it difficult for the stone knot
to release after the Smooth Operator has been pulled. A bight
formed in the center strands will also create a stone knot that does
not grab the Smooth Operator as securely. However some people may
not pay careful attention to how they tie the stone knot and may end
up with a bight formed in the center strands.
When you see the stone knot was tied with the Middle Strands Form a
Bight it also means the stone knot was tied in the DOWN position.
L'MAR
Safety precautions can be set in place for everyone but the last
man. The last person need to remove the safeties and rappel
down last. While relatively safe the last man does assume
additional risk. This is commonly referred to as Last Man at
Risk. I kind of think of the Last Man at Risk as a character
of its own with the name of L'MAR. ....... L'MAR is a
bad ass!
Measuring the Release Force
I measured the release force for pulling the Smooth Operator free from
the stone knot with a luggage scale. The stone knot was tied
then cinched down. Then a luggage scale was attached to a pull
hole in the Smooth Operator and was steadily pulled on. The force
was gradually increased until the Smooth Operator was pulled free and
the max force on the scale was recorded.
What are we Looking For?
When the Smooth Operator / stone knot is weighted (while someone is on
rappel) it can be difficult to pull the Smooth Operator out of the stone
knot. When the Smooth Operator / stone knot is not weighted
(nothing is applying weight to the system) the Smooth Operator can be
removed with minimal force. The major concern is that the
Smooth Operator is not accidentally removed until everyone is is at the
bottom of the rappel and off the rope.
Using the Smooth Operator in a Group
If you are in the canyon with other people (not going solo) the
Smooth Operator is set up and a safety carabiner is inserted in the
Smooth Operator to keep it from being removed. Everyone except the
last person rappels when the safety carabiner is in the Smooth
Operator
which locks the Smooth Operator in the stone knot.
The last man at risk (L'MAR) removes the safety carabiner then
rappels down. When the safety carabiner is removed there is
potential for the Smooth Operator to be pulled from the stone knot.
While the last man is weighting the rappel rope it takes
considerable effort to remove the Smooth Operator from the stone knot
and L'MAR is pretty safe.
There are two dangerous moments for L'MAR when the rope can be
unweighted. The first moment is when the safety carabiner has
been removed and the last man is not yet on rappel weighting the
rope. The other time there is risk is when the last man
unweights the rope during rappel. Unweighting the rope in the
middle of the rappel can be done if there are ledges or potholes to
cross during rappel. The last man may also stop on a small
ledge to adjust their harness or rappel device which unweights the
rope.
In a group situation the dangerous moments are for L'MAR (last man
at risk) when the rope is unweighted. Fortunately the pull
line has been set by the previous people (they did set it for L'MAR
right?) and the system has been weighted by everyone which has
cinched the stone knot tighter and tighter with each person who
rappelled before.
Using the Smooth Operator while Soloing
In some cases you may use the Smooth Operator by yourself. This
can happen if you decide to solo a canyon or if you are separated
from your group and for some reason decide to use the Smooth
Operator
for a rappel. In this case there are no people to rappel
before L'MAR ........ you are L'MAR and you are alone. The
difference in this situation is you have no one to set the pull line
ahead of you while the safety carabiner is inserted in the
Smooth Operator and there is no one to rappel before you to help cinch
the stone knot down on the Smooth Operator.
In some cases you can just toss the pull line and know it is
set properly before you rappel. But in some cases there is too
much vegetation, there are large ledges or other things that might
make it impossible to just toss the pull line down. In some
cases you need to attach the pull line to you and haul it down while
being careful not to pull on the Smooth Operator until you at the bottom
of the rappel. Multi stage rappels can make this a little
difficult at times.
In a solo situation the dangerous moments are the same but the stone
knot has not been cinched down well by previous rappellers and pull
cord has not been set for you. Another issue is you were not
able to sit and watch the stone knot and Smooth Operator while others
rappelled first, you set it and hope you got it right.
The main concern is
The main concern is minimizing pull force on the Smooth
Operator during
those couple dangerous moments for L'MAR. How much force does
it take to remove the Smooth Operator when the rappel rope is unweighted
and how much does my pull line weigh any way? There are three
moments we are mostly concerned with for accidental pulling of the
Smooth Operator.
-
Group situation with L'MAR removing the safety carabiner and getting
onto rappel.
- Solo situation with L'MAR getting onto rappel after the
Smooth Operator
is rigged.
- Unweighting the rope mid rappel.
- This is the same for group
situations or solo.
The Smooth Operator / stone
knot has been weighted and is temporarily unweighted during rappel.
Testing Stuff
The tests below use a Gnome Gear Smooth Operator and an Imlay Canyon Gear Canyon
Fire 8.3mm rope. Both the Smooth Operator and the rope were in used condition
with rough surfaces. The tests were done with dry conditions
and free of sand. I used the Gnome Gear Smooth Operator because
that is what this section is all about. I chose the Imlay
Canyon Gear rope because I have it on hand and it is one of the
common ropes in use. Using different ropes or different
Smooth Operators will obviously give different results.
How much weight does the anchor experience? And how much force
is needed to remove the Smooth Operator after it the weight is removed?
In cases where a rappel rope travels from the anchor then over an
edge before going vertical, it is common for an anchor to experience
less force than the weight of the rappeller. If all the people
in your group are light weights the anchor wont see a lot of force.
I guestimated a number of 80 pounds.
With the Middle Strands Straight, a Standard Cinch and the rappel
rope weighted to 80 pounds......
I did six tests and measured the pull force required to remove the
Smooth Operator from the stone knot after the weight was removed.
The numbers were 11, 12, 12, 9, 14 and 10 pounds.
With an average of 11.3 pounds of force needed.
In cases where a rappel goes vertical straight down from the anchor
(like a bolted station on a wall) the person on rappel is generally
able to weight the rope smoothly with no significant bouncing.
I used my body weight of 175 and feel I am in the middle weight
range of the average canyoneer.
With the Middle Strands Straight, a Standard Cinch and the rappel
rope weighted to 175 pounds......
I did six tests and measured the pull force required to remove the
Smooth Operator from the stone knot.
The numbers were 15 13, 13, 12, 13 and 9 pounds
With an average of 12.3 pounds of force needed.
In some cases the anchor may experience more weight so I decided to
see how things went with more weight. I decided to take the
easy road and just add my weight to the rappel rope then do 3 to 4
bounces of about one foot on the rope.
With the Middle Strands Straight, a Standard Cinch and the rappel
rope bounced on with 175 pounds......
I did six tests and measured the pull force required to remove the
Smooth Operator from the stone knot.
The numbers were 20, 20, 25, 32, 31 and 33 pounds.
With an average of 26.8 pounds of force needed.
So how much of a difference is there if the center strands are
forming a bight and not kept straight? The amount of force
needed to remove the Smooth Operator dropped by around 4 pounds.
This can also result in difficulty with the stone knot releasing.
Avoid setting your Smooth Operator up like this.
With the Middle Strands Forming a Bight, a Standard Cinch and the
rappel rope weighted to 175 pounds......
I did six tests and measured the pull force required to remove the
Smooth Operator from the stone knot.
The numbers were 9, 5, 6, 16, 5 and 11 pounds.
With an average of 8.6 pounds of force needed.
So now we have a little bit of an idea of the forces needed to
remove the Smooth Operator after the rope has been weighted. But
what about the guy going solo and using a Smooth Operator? He has
to set up the pull cord and get on rappel on a Smooth Operator that has
not yet been weighted. Since no one will be rappelling before
L'MAR cinching the stone knot around the Smooth Operator becomes more
important. Being sure to cinch down the stone knot well can
add a significant safety margin when using the Smooth Operator solo.
With the Middle Strands Straight, a Lazy Cinch and the rappel rope
never weighted........
I did six tests and measured the pull force required to remove the
Smooth Operator from the stone knot.
The numbers were 6, 7, 7, 8, 6 and 5 pounds.
With an average of 5.7 pounds of force needed.
With the Middle Strands Straight, a Standard Cinch and the rappel
rope never weighted......
I did six tests and measured the pull force required to remove the
Smooth Operator from the stone knot.
The numbers were 15, 9, 13, 12, 16 and 12 pounds.
With an average of 12.8 pounds of force needed.
With the Middle Strands Straight, a Hard Cinch and the rappel rope
never weighted.......
I did six tests and measured the pull force required to remove the
Smooth Operator from the stone knot.
The numbers were 15, 13, 17, 13, 24 and 17 pounds.
With an average of 16.5 pounds of force needed.
What if someone uses the Smooth Operator solo AND ties the Smooth
Operator
the wrong way and allows the center strands to form a bight?
Tying the stone knot wrong and allowing the center strands to form a
bight can reduce the force needed to remove the Smooth Operator
significantly.
With the Middle Strands Forming a Bight, a Standard Cinch and the
rappel rope never weighted......
I did six tests and measured the pull force required to remove the
Smooth Operator from the stone knot.
The numbers were 6, 5, 8, 8, 4 and 5 pounds.
With an average of 6 pounds of force needed.
Conclusion
From the tests above we have some numbers to play with. The
tests were done with only one kind of rope and Smooth Operator and in
dry conditions. Keep in mind different conditions and
different gear will effect things. This is intended to get an
idea of the forces at play and help make a judgment on best
practices.
In a group situation all but the last person rappels down with a
safety carabiner in the Smooth Operator so it will not pull out.
As each person rappels down they weight the anchor cinching the knot
a little tighter. In most cases the anchor will be subjected
to less than 200 pounds of force to cinch the knot. So L'MAR
(last man at risk) removes the safety carabiner and rappels on a
stone knot that has been cinched down with less than 200 pounds of
force. If the stone knot has been tied properly (Middle
Strands Straight) and cinched down well; the force to pull the
Smooth Operator from the stone
knot while the rope is not weighted would be about 12 pounds.
In a solo situation there are no people to rappel ahead of L'MAR and
cinch the stone knot down. If you are sure to cinch the knot
very tight you can make it so the force needed to pull the
Smooth Operator is also about 12 pounds. If you are using the
Smooth Operator solo it is very important to tie the stone knot
correctly and cinch it down very tight. In a solo situation
greater care must be taken when setting the pull line since there
will be no safety carabiner in place while it is being set.
Note:
Tying the Smooth Operator wrong and allowing the middle strands to from
a bight can reduce the force required to about 8.5 pounds. Also
not cinching down the stone knot can greatly reduce the force needed
to pull the Smooth Operator from the stone knot. It is very
important to tie the stone knot properly and cinch it down tight.
Keep in mind the weight of the pull line can be pulling on the
Smooth Operator as it hangs down the rappel. As a rule of thumb it
is a good idea to keep the weight of the pull line to 8 pounds or
less. With 8 pounds of pull line on the Smooth Operator it may
only take about 4 pounds of force to pull the Smooth Operator during
moments where the rope is not weighted. If the rappel is
dropping over a ledge or around corners this will reduce the amount
of force the pull line exerts on the Smooth Operator.
For longer drops or if you just want less weight on the pull line a
Dyneema pull line may be a good choice. 1/8 inch Dyneema is
very light, packs down very small and has a breaking strength of
about 2300 pounds. You can order Dyneema from marine shops
online for about 35 cents a foot. Keep in mind the Dyneema
pull line can NEVER be used as an emergency rappel rope or for
lowering. Dyneema is very strong for its size but has a low
melting point. The friction involved with rappelling or
lowering can melt Dyneema causing catastrophic failure.
The main takeaways are......
Always tie the stone knot properly. If you don't know how
check out the Stone Knot for
Smooth Operator page.
Always cinch down the stone knot well. Don't just pull till it
looks good, cinch it down tight.
Try to avoid using more than 8 pounds of pull line on the
Smooth Operator.