VT Phone Home

Over the last few years, we have integrated the VT Prusik into our Rope Rescue Support (RRS) course, and have dabbled with it in the Basic Mountaineering Course (BMC). This year, it will be a requirement to have in all our rope-centric courses, extending it’s use to BMC as well as Rope Rescue Operator (RRO) and Rope Rescue Technician (RRT). 

  

The term “VT Prusik” comes from the French Valdotain Tresse, or loosely translated, “French braid”, and refers more specifically to a type of hitch. The term is now used colloquially to refer to a style of sewn eye to eye prusik, that is often used to tie the VT hitch. This is similar story to that of the term “Prusik” itself. The prusik hitch was named after an Austrian mountaineer named Karl Prusik, who first developed the hitch tied out of smaller diameter cord, to ascend a host rope. The small cords carried by mountaineers and climbers, often tied into loops, at some point began being referred to as prusik cord, or prusik loops. With that being said, let’s look at the VT hitch, and the VT prusik individually. 

VT, The Hitch

To tie a VT hitch, you need to have an eye to eye cord. The hitch is tied by first wrapping the cord around the host rope about 3 times, followed by braiding the remainder of the cord around the host rope, and lastly connecting to both the sewn eyes. A popular hitch with arborists, it provides a reliable grab, while also being more releasable due to the gripping force being spread out across the braided section. Collapsing the braids straightens the rope, freeing the rope in most cases.  

VT, The Prusik

A VT prusik, refers to a supple sewn eye to eye cord, about 33 inches long, constructed with aramid fibers with very high melting points. The specific design criteria was developed to enhance the overall use of the cord. The suppleness, often achieved by reducing the number of core strands or using specific carrier and braid sheaths, allows the hitch to grip host ropes very tight, while the high melting point of the aramid fibers allows for the cord to move over the host rope without melting. This enhances the releasability of the hitch, and even allows for the cord to move aggressively over weighted host ropes. The term became common after Bluewater Rope started to manufacture the specialized prusik with all the above-mentioned features, calling it by the name VT Prusik. Aside from being used in the VT hitch configuration, the eye to eye length of cord can be used for any number of applications in mountain travel and rescue systems. It's use as a tether, draw, anchor or anchor extension, rope grab, belay component, liter bridal legs, autoblock, asymmetric prusik hitch, and stylish necklace to name a few that come to mind!

Not all VT prusiks are the same

 The Rope Rescue Oversight Committee endorses the use of the Bluewater VT Prusik. While we do not specifically exclude other makes from use, there is a few reasons for this endorsement we need to consider. First, the Bluewater VT Prusik best meets the design criteria mentioned. The cord is supple, it’s sheath is fully aramid fiber, and the 8mm version maintains a 19.5kN breaking strength end to end. And it is made in the USA. By comparison, other brands versions of VT Prusiks, can be found with a blended sheath, with both aramid and polyester fibers, which sacrifices that heat resistance. Other brands cord is a more dense sheath, making it stiffer, and less likely to grab finicky host ropes. Second, extensive testing of VT prusiks in rescue systems, has shown that when tied and deployed correctly, acts as a suitable part of belay, passing the ASTM F2436 standard for rope rescue belay system performance. What we do prohibit, is the use of VT prusiks that have been manufactured by non-reputable, off brand companies especially of unknown countries of origin. The brand GM Climbing is one such example. As the use of this product becomes more prevalent in our systems, a few key things should be remembered. Buy your gear from reputable sources and brands you know and trust. Practice using the gear in safe areas with knowledgeable mentors before using it on a rescue or recreationally. Never assume you are using it correctly, seek guidance and ask questions!

If you would like to read more about the VT prusik and its use in rescue applications, check out the following research papers. 

VT Prusik for Rescue Belays, Mike Gibbs

Down the Rabbit Holes of Small-Diameter Rope Systems, Justin Wheaton, Jonathan Wilson, Craig McClure

Joint Training Observations

I had the wonderful opportunity to attend a SAR training involving a number of different teams. The command post also was hosting new members to learn those skills. The event was fantastic. There are many positive experiences that came from it. However, this article discusses some of the challenges associated with waypoint format and phone apps.

SARTopo has quickly become the go to app for in field phone navigation as well as command post event organization. It can be very useful whether the SAR field personnel has cell service or not. With good field cell service, the command post may be able to watch the movement of a team in real time. A team may be able to monitor the location of other teams. As with all technology, there is a price to be paid, not just in dollars.

At the joint training, there was a huge QR code at the sign in table for all who were attending the event. A person would activate SARTopo on their phone and join in the map created by the command post. When I arrived, many people with Android and iPhones were frustrated trying to log on. I could not on my Android phone. My wife could not on her iPhone. We both had T-mobile service. We went to the command post and connected to their WIFI. We had to log off our SARTopo accounts and then log back on. Finally we connected to the map the CP built for the event. This logging on/off problem has happened to me twice before on real missions with other teams. Some of the people at the joint training still could not log on for the training. They were given printed maps.

My field team prepared to leave the CP and head to the trailhead. In preparation, we had to insert the single UTM waypoint the CP had given us. Three team members struggled with this. They had to figure out how to use UTM in SARTopo. Ultimately they determined that CP had given them a UTM with too many digits. I had preloaded significant landmarks on my phone from the night before. Off we went, hiking more than a mile to where the actual search would begin. We had also been given verbal description of where that UTM was. We arrived at the location marked on our phones. It did not match the verbal description. Meanwhile, another team arrived who initially could not get SARTopo to work. They were relying on a printed map. But eventually they could see a grid system on SARTopo that CP had added while they were hiking. They were heading to that. They ignored the printed, single UTM waypoint that CP had originally given them. They were a great inspiration for me. I hoped my phone would show the grid for my assignment. I opened up SARTopo and tried to use it to check my newly formed grid. The screen was a mass of different colored lines from all of the teams in the field. I tried to zoom in to only see my team and the other team near us. As soon as I moved my fingers off of the screen, it zoomed back out to the mass of lines. It was worthless. After many radio calls to CP, I was given three waypoints to head to. Ultimately we found the subject and the training missions was a fantastic success.

I am greatly in favor of SARTopo. I have built detailed maps for Mt. Baldy and San Gorgonio that I keep on my phone, separated into their own folders. With some warning of a pending mission, I can build a map on my computer with significant landmarks for a new location. In the field, I can turn on the tracking function; allowing CP to get my track in real time or when I return to CP or when I obtain internet access later. SARTopo has incredible features with historical maps, current snow coverage, weather, public lands, etc., etc. But I am still struggling to use it in the field. Admittedly all new phone apps need a learning curve. There may be subtle differences between the app on Android and iPhone. As of now, I can not rely on it. Hence I always run a second mapping program on my phone simultaneously. Gaia works well on both Android and iPhones. Some people use Backcountry Navigator or Avenza. I also use Locus Pro which is only built for Android.

For the format of a waypoint, I much refer decimal degrees over UTM. The only advantages I see with UTM are the ease of plotting a position on a paper map and knowing how far I am from a point. Otherwise, I find it cumbersome. With decimal degrees, it is much easier to cut and past into Google maps or SARTopo on my computer in order to go to a location. On Google maps, a “search nearby” can result in a decimal degree waypoint within a couple steps. A general internet search may result in a waypoint with degrees, minutes, seconds. With a couple of clicks, that can be converted to decimal degrees and inserted in SARTopo. It is easier to use when finding word wide locations.

RRS Course

Rope Rescue Oversight Committee (R.R.O.C.) is sponsoring a Rope Rescue Support (RRS) course. It will be held June 3, 4, and 5, 2022. Only members of San Bernardino County Sheriff affiliated departments and search and rescue teams are allowed to attend.

For each two students from a rope certified team, their team must provide one Rope Rescue Operator (RRO) or Rope Rescue Technician (RRT) to function as assistant instructor.

Students from non-rope certified teams are not required to obtain assistant instructors.

There will be pre-course assignments wherein the student learns to tie knots and studies material. A pass/fail test will be given on this material on the first morning. All students are required to pass the test. More information will be sent to participants a few weeks before the course. Students should seek assistance from their respective teams for the pre-course assignments.

The tentative location of the course is the fire department next door to VFU. Class starts promptly at 0800 on each day. Expect to end late at night on June 3 and 4.

To register, please fill out this form: https://forms.gle/uEvjWrjFtfGMYRHQ8

Theoretical Mechanical Advantage

On the final day of our Rope Rescue Operator course, a great debrief discussion came up during the final test evolution. Both groups that tested that day became challenged to lift a 4 person load up a moderate slope using a 3:1 mechanical advantage (MA) with the DCTTRS system they had built. The decision was quickly made by both teams to reconfigure the pulleys to a 5:1 MA - Great Work! As the raise continued, the two groups were faced with another decision, this time, they diverged. One team decided to re-direct the haul downhill, while the other team did not. Given the slope of the hill and the length of the haul field, hauling down hill was a reasonable decision. When rigging the redirect to haul downhill the team realized they did not have more pulleys left in the cache. They decided they were going to build the redirect with carabiners, another reasonable decision given the tools at hand. At this time, a few extra pulleys were provided by some instructors, and it was said that we would debrief on why after the scenario. So why the pulleys and not the carabiners?

The introduction of that carabiner rather than a pulley, reduces the mechanical advantage to almost a 2:1. Yep – a 2:1.

Before we explain why, it’s important to understand the difference between ideal MA, and theoretical MA. First, ideal MA is a broad estimate, designed to make decision making and evaluation easy in the field. This is how we almost always discuss MA - 3:1, 5:1, 9:1 and so on. These figures do not take into consideration many factors, but for simplicities sake, lets look at the big one, efficiency. To calculate a theoretical MA, we must consider the efficiency of the pulleys in our system. The higher the efficiency, the higher the MA, the lower the efficiency, you guessed it – The lower the MA. By using the “T” system for determining ideal MA and subtracting the inefficiencies it is not difficult to calculate a theoretical MA. This calculation is still “theoretical” because we are only accounting for pulley inefficiencies. To figure out the actual MA can be difficult to do in an equation. You may need to consider the angles rope enter and exit pulleys, the ropes construction, force acceleration such as bouncing, and a host of other factors. However, we can measure the actual  MA very simply by measuring input force and output force with scales called dynamometers.

So how does the carabiner being used as a redirect reduce my systems theoretical MA to a 2:1? Well, that’s the fun part. As tension is introduced into your system by hauling, the efficiency of each pulley strips away your MA turn by turn. Like water moving through a water line into your home from the street, the larger pipes in the street full of water volume are reduced to the smaller pipes in your home, that change from large to small creates the water pressure in your home. To understand what this has to do with reducing MA, let’s flip it around. If I had small waterlines in the street, and large pipes in my home, the small pipes would never fill the large ones in my home, and I would have no water pressure. No one likes a drizzly shower. A similar thing happens when we put our hauling tension into rope, that is then squeezed through an inefficient carabiner, before it goes through an efficient pulley. It deprives our system of much needed tension, like the big pipe deprived me of a good shower.

To demonstrate this, we will use the “T” method for determining MA, but we will show the theoretical MA by subtracting the efficiency from each pulley. Let’s say our system pulleys are 90% efficient, that’s about average for pulleys you see in rescue. And for the carabiner being used as a pulley, the efficiency is about 50%.

In a typical 3:1, If each pulley is 90% efficient, our tension is reduced by 10% at each. 

Let’s then say you only have 1 pulley with you. You decide to put it at the progress capture location to mind the prusik. Reasonable decision. However, that carabiner is going to reduce our tension by 50%

Then we will reverse the two. It presents operational issues but let’s see what it does to our mechanical advantage. 

Now Let’s apply this concept to the 5:1 system in our story. Here is the theoretical MA to a simple 5:1.

Next, we will redirect our haul. We have no more pulleys, but we have tons of carabiners! Remember a redirect ads no mechanical advantage, but we rarely consider what it is taking away.

Using the exact same gear, and what we have just learned, the easiest way to regain some of that mechanical advantage would be to use the carabiner as a pulley further down the system.

Our systems are never truly what they seem. And we are often tasked with doing the best we can with what we have. It’s not easy to calculate your actual mechanical advantage in the field, and it is typically not necessary to do so. But with this information, we can figure out what our theoretical mechanical advantage is. Some small changes to our rigging can make a considerable difference.

As with most things rigging there are many layers. You can always dig deeper and expand on your knowledge. If you would like to learn more about pulley efficiencies in rope systems, please check out these articles on pulley efficiencies in mechanical advantage progression, and an analysis on a systems overall efficiency as a function of the number of pulleys!

 http://rope-work-101.wikidot.com/pulley-systems

In a typical 3:1, If each pulley is 90% efficient, our tension is reduced by 10% at each 

BMC Coming Nov 21-22

Save the dates November 20 and 21, 2021. The classroom session for BMC will be held that Saturday and Sunday weekend at Volunteer Forces, 199 N. Hangar Way, San Bernardino, CA 92415.

Please sign up at: https://forms.gle/rx2AJMvBXRj9FFAh8. For members of San Bernardino county SAR teams, you must use your SBSAR email address.

At the end of the classroom session, participants will receive a certificate for Winter Alpine Awareness (WAA). This will allow you to participate on some non-technical winter missions involving snow.

Individuals who are certified as Rope Rescue Operators (RRO) may go on to take the BMC field session. After completion of that two day field experience, you will be BMC certified and can attend all winter SAR missions.

The situation with COVID-19 virtually changes day by day. We will not know until November if it affects class size. And, of course, it is possible the class could be cancelled entirely. Please be patient and understanding.

Fear the Gear: A Near Miss at RRS

Earlier this month during our RRS course, we had a near miss. A near miss is an unplanned

event that did not result in a serious injury, but had the potential to do so. A near miss is often

due to a fortunate break in a sequence of events. Sometimes it’s timing, distance, or a warning

from someone close by. In some instances, it’s hard to call it anything other than luck.

Continue reading the full article.

Please read your email as soon as possible from Donna Newlin for inspection information.

Zello: A Network Radio Solution

For a number of years, the Cave Team has been using network radios to augment existing radio communications. Recently, the tool that we have been using, Zello, has offered their commercial product for free to emergency services organizations. We jumped at this opportunity and transitioned from their free product to the commercial version.

Network radios are devices or applications that operate like traditional radio services in a one-to-many fashion. Instead of using trunked radio systems, conventional repeaters, or direct radio connectivity, they connect to a data network. This data network can be via cell data or that provided by a WiFi connection. In order for Zello to work in the field, you must have a cell connection. Once connected, however, you create your own push-to-talk (PTT) radio network that works anywhere you are in cell coverage.

In addition to voice PTT functionality there is also text and image messaging, and location sharing. Location sharing can be handy in many SAR scenarios. In fact, on a recent search mission some of my teammates were looking for the command post, and unable to find the right location. I was able to give them an idea of where they were relative to the CP location, and speed their arrival.

My team is spread out all over Southern California, and Zello has provided us a useful one-to-many tool for wide area coordination that is quickly deployed. After using Zello for a number of years, I have compiled a few thoughts that may help in understanding how you may integrate Zello into your team's activities. You can read it here.

Like any tool, regular training is necessary for success. Using Zello takes a bit of practice, and does not replace our existing radio networks. It is a powerful tool, however, and if your team is interested, feel free to contact Jeff Lehman (jlehman@sbsar.org) for more information.
 

Auto Tracking Teams in SARTopo

The Cave and Technical Rescue Team spent this last weekend executing a land navigation training. Set up was the same as most any other team in the county; maps, makeshift command posts, plotting coordinates, and of course - incoherent radio traffic. The only difference was our experiment with SARTopo.com’s additional access features.

Granting additional access to individuals in the field allowed us to track our teams in real time. The good news is that it worked well. The great news is that it wasn’t hard to do! In short, the command post can generate the additional access link and a QR code with just a few clicks, and from there any team member with the link or a smart phone could access the tracking map. Once a team member is linked to the map, any tracks they record, or waypoints they create will be automatically updated on the host map. The benefits of such a system include:

1. Reduced radio traffic, when the CP is aware of your coordinates without having to ask.
2. In field coordination, due to your ability to see other teams on the shared map via your mobile device.
3. Conspicuous observation of assignment execution and progress for the command post, facilitating on the spot planning.
4. Reduced post operation down time, from not having to download tracks from individual searchers devices.

All that being said, there are some issues to address. The first of all being cellular service. As you may have guessed already, for this system to function as exceptionally as described, you need to have cell service. However, this isn’t a total deal breaker. Most importantly, you need service somewhere near the command post to link to the map. From there, lack of cell service only prohibits instant tracking. Anytime your phone contacts service it will upload what it can. This still allows you to benefit from most of the advantages listed. Next would be phone battery life. Tracking with your phone, from any app, can eat up your battery. Teams should be prepared with external batteries to keep phones going through an entire operational period. You must have downloaded the sartopo app. Once in the app, it is easy to set waypoints and start tracking, but as with anything, there is certainly a small learning curve.

Check out this document for some set-up instructions, and try it with your own team.

 

Ice Axe Tether

The instructors for the Basic Mountaineering Course (BMC) have made a modification to the required gear list. The change has to do with the tether on the ice ax.

Ice axes may or may not come with a commercially made tether. Such tethers are geared toward recreational mountaineering use. They may have features that make them superior for general mountaineering. However, they lack one or two features that are quite useful for SAR. The mechanism for attachment may be very simple and not very strong. The tether itself may not be very strong. And the tether may not be easily adjustable. 

For BMC, we teach that ice axes can be used to build snow anchors. They may be a deadman, positioned vertically or horizontally. They may be a critical initial piece of equipment for use in escaping the belay. Consequently we desire a tether that is easily but securely attached to the ice ax. It should only reach to the bottom of the ax. It should be rated for at least a one-person load. It should be usable in an anchor system. It should act as a shock absorber. And it should be easily adjustable in length. Purcell prussiks satisfy these functions. Hence from now on as a minimum, all ice ax tethers used in BMC will be made out of 6 mm or greater diameter cord tied as a Purcell prussik. Commercially sewn Purcell prussiks are acceptable.

A student may wish to consider a tether made out of Dyneema instead of nylon. Dyneema is stronger and does not absorb water (and hence won’t freeze in the snow the way nylon does). In the attached photo, the ice ax is equipped with a Mammut 8 mm thick, 60 cm long Contact sling tied as a Purcell prussik. It breaks at 22 kN.  It is girth hitched to the ice ax. Next to it is a nylon cord tied as a Purcell prussik.

BMC 2020/2021

Save the dates November 21 and 22, 2020. The classroom session for BMC will be held that Saturday and Sunday weekend at Volunteer Forces, 199 N. Hangar Way, San Bernardino, CA 92415. Please sign up at: https://forms.gle/j45QaRQFopytxnwa8. For members of San Bernardino county SAR teams, you must use your SBSAR email address.

At the end of the classroom session, participants will receive a certificate for Winter Alpine Awareness (WAA). This will allow you to participate on some non-technical winter missions involving snow. Individuals who are certified as Rope Rescue Operators (RRO) may go on to take the BMC field session. After completion of that two day field experience, you will be BMC certified and can attend all winter SAR missions.

Temporary BMC certification

Unfortunately due to COVID-19, RRO classes had to be cancelled this year. As noted above, RRO is prerequisite for full BMC certification. Hence this year, there could be a deficit of SAR members certified to attend full winter missions. To accommodate this, for the 2020/2021 winter only, temporary BMC privileges will be granted case by case. Individuals requesting temporary certification will be evaluated by the BMC instructors. All interested SAR members are required to take the classroom session on November 21 and 22, even if they are already WAA certified. Those interested please apply at: https://forms.gle/iWmhr92Nvotw7Sqn9.

The size of the class is yet to be determined. It depends on the status of COVID-19 during the two weeks prior to the class. It is possible there will be a waiting list with notification of acceptance the week prior to the class. The BMC instructors will determine who is allowed to attend. And, of course, it is possible the class could be cancelled entirely. Please be patient and understanding.