Alpine Tips
Sterling rope technical manual
What are the two chemicals you should always avoid getting on your rope? If a rope is wet, is it less strong, and by how much? Can I safely mark my rope with a Sharpie pen? Learn all this and more from the experts at Sterling, in their technical manual.
Think you know “the ropes”? The Sterling Rope Company has a great 16 page technical manual (.pdf file). Check this link and learn a few tricks.
(It's a 6 MB file, be patient on the download, it may take a few seconds.)
Learn about . . .
The difference between S twist and Z twist
Details of rope construction
The differences in manufacturing process between a static and dynamic rope
The five requirements of UIAA rope testing
The dramatic loss of strength that happens to a wet rope
The two chemicals you should ALWAYS avoid getting on your rope
The Word on marking your rope with permanent (Sharpie) pens
Sterling rope technical manual
Backup battery and charging cable - the 11th Essential
If you bring electronics in the backcountry, (smartphone and GPS app), it's pretty much mandatory to carry an extra power source. Here’s a great choice, at about 3 oz and $20.
With smartphones ever more common as vital backcountry navigation tools (try our favorite, Gaia GPS), it’s also crucial to have a means of charging them. While always putting your phone in airplane mode at the trailhead to save battery is good practice, having some backup power is inexpensive and lightweight.
Some people only will take an auxiliary battery on a multi-day trip. That works great provided you remember to charge your phone fully in your car driving to the trailhead, but that is a little task that's easy to forget. For me, it's more reliable to just carry a fully charged extra battery and cable as standard practice.
Anker makes great auxiliary batteries in a variety of sizes. With the larger batteries of modern phones, probably 5,000 mAh is the smallest do you want to go, which should give you one full charge. (Geek note: “mAh” means milliamp hours, a way to describe battery capacity.)
If you're going on a longer trip, sharing your battery with partner(s) or don't mind carrying a little more weight, go with a 10,000 mAh battery. That should easily last one person a week or so.
I like having both - this small one for short term emergency backup, and a 10,000 for longer trips.
In addition, you can get a tiny 4 inch long charging cable for your iPhone; no need to bring the long cord you use at home. I'm sure there's one for Android folks as well.
Tip: cheap charging cables can get damaged getting banged around in your pack and fail when you most need them. Try to buy cables that are a little more durable, and consider bringing two of them on longer trips, they are inexpensive and extremely lightweight.
The auxiliary battery and the charging cable together cost about $20, and weigh 3.5 ounces. Personally, I consider a battery and charging cable the 11th essential, and carry this tiny additional weight with me on every trip.
Note - If you search online, you'll find loads of different battery options, many from off-brand companies. I’ve tried a few of these trying to save a few bucks, and been disappointed. I recommend you pay a tiny bit more and get a name brand like Anker.
The photo below is a few years old; now I'm using a 5000 mAh battery. but you get the idea.
(Sharpie pen shown for scale)
Steri-Strips for the first aid kit
Here's a great item to have in your first aid kit that most people don't carry.
Steri-Strips, a cross between a band-aid and a suture, are narrow strips of super strong first aid tape that really stick to skin and are used to close cuts in place of a suture. 3M makes them, so you know the adhesive is good stuff.
They're inexpensive, weigh nothing, and could save the day if you need to care for a substantial cut in the backcountry. Consider adding them to your first aid kit. Get them at better stocked pharmacies and medical supply stores, and through the usual online retailers.
Could this be the best free firestarter?
Want a terrific firestarter that’s free and burns great? Look no further than a supermarket - waxed cardboard produce boxes are your friend.
This tip is more for car camping or a home fireplace. For a superb fire starter, go to the produce section of any supermarket, and ask the produce person for a dark brown waxed cardboard box or two. (Or look around the back of the store and find a pile as shown below.)
These boxes are regular cardboard dipped in paraffin, so they can hold wet veggies like lettuce without falling apart. The boxes are free for the asking.
Tear the boxes into strips, and use them as starters for your next fire. They burn furiously for several minutes, are lightweight, mostly waterproof, and free. One box makes a LOT of fire starters!
Belaying the second from the anchor - pros and cons
Belaying a second can happen off your harness, or direct off the anchor. Learn the benefits of this technique - and one time to consider not using it.
Most climbers start out learning to belay off of their harness. For most snow climbs and most all instances of belaying a leader, this is still usually the best method. But for belaying a second when rock climbing, belaying directly from the anchor with either a Munter hitch or some version of an autolocking belay device has a host of advantages. Here’s a few of them.
Advantages . . .
better on difficult pitches (where fall is likely for the second), as it’s usually easier to catch and hold a fall
better for easy terrain (where second is moving fast and will likely not fall) as you can take in rope faster
puts less force on the anchor (only the weight of the second)
autolocks with Reverso, ATC Guide, or other modern belay devices (or just use a Munter hitch to keep it simple!)
belayer is free to move around more
easier to escape the belay and initiate a rescue
easy to rig a mechanical advantage haul to pull up the second if needed
easier to properly equalize the anchor toward the direction of load
Disadvantages . . .
fall directly impacts anchor (rarely a problem on rock if the anchor is stout.)
So, when might you want to belay the second off of your harness? Basically, when the anchor is anything less than 200% solid.
That means most of the time when you are snow climbing, and in many alpine rock climbing situations. When climbing alpine rock (which typically means many pitches over a long day and trying to move as efficiently as possible over relatively easy climbing) an "anchor" might be one decent cam plugged into a crack, or a sling around a small tree or over a rock horn, or some other single point of gear.
In this case, the belayer will typically sit down, try to brace their feet in a solid position, and belay off of their harness. By doing this, the belayer takes the impact force for any fall onto them, and the anchor is essentially backing up their stance.
Note: if you choose to use an auto locking blade device such as an ATC Guide or Petzl Reverso, keep in mind that there have been many serious accidents when people use these devices in correctly, often when trying to lower someone when the rope is under load. Be absolutely sure you know how to use these devices correctly before ever trying it on a real climb.
image: “Multi-Pitch Belaying- Potentially Fatal Errors to Avoid” - youtube.com/watch?v=s9np7B1Zao4
Belayer’s responsibilities to the climber
The belayer has a LOT more to do than it may first appear. Do you know all of these duties? Did I leave any out?
The belayer has many duties beyond feeding out or taking in rope. A good belayer, when belaying either a leader or a second, will consider doing the following:
image: https://www.petzl.com/US/en/Sport/Spotting-and-belaying-at-the-start-of-the-route?ActivityName=Rock-climbing
Belaying the leader, most important! If you're on the ground, spot the leader before (or even after) they make the first clip! No need to “belay” if there’s no gear in. This usually means the belayer drops the rope and stands with hands outstretched, ready to keep the leader’s head and upper body from smacking anything if they fall before clipping the first piece of gear. The moment the leader clips the first pro, the belayer drops their hands to the rope and starts the belay properly. Keep your thumbs tucked in and your fingers together (aka “spoon”), and not fingers spread out (aka ”fork”) to avoid injury.
If you are with a new partner and top roping, ask how much slack is desired. Many beginners want you to keep the rope fairly tight, while more experienced people will probably want a little slack.
Never pull the leader off by keeping rope too tight! Always gives them a meter or so of slack rope so they can move freely. If the leader is climbing above a ledge, you can snug it up the rope a little, but never restrict their movements.
Be attentive and watch; feed rope if they need to clip, take rope in if they are looking sketched.
Keep the rope out of the leader’s way before the first clip. This may mean you stand off to one side to keep the rope away from their feet.
Help build a multidirectional first gear placement, if needed.
Give encouragement to the climber, but avoid idle chatter. Keep your communication as short and clear as possible.
Tell leader about rope getting stuck in cracks or around horns (“flip rope”).
Warn leader (“grounder alert”) if they have climbed too far above their last piece of gear.
Tell leader about amount of remaining rope if it’s getting close to the end. Use the call, “feet 2-0”. (Most belayers underestimate the amount of rope left.)
Make sure the rope feeds freely. Flake the rope well, and watch for tangles. Tarps, rope bags or duffel bags are good for this.
If you're on a single pitch climb and plan to lower your leader, be sure the middle mark of the rope does not pass through your belay device, and you have closed the rope system by having a knot in the end of the rope. These steps prevents the common accident of dropping your climber when lowering because your rope is too short.
Tell leader if they back clip (more of an issue when sport climbing, not a concern with long runners).
When belaying the second up to your stance, as the second approaches the anchor, the belayer tells them two things: 1) where to clip and 2) where to stand.
image: https://www.petzl.com/US/en/Sport/Spotting-and-belaying-at-the-start-of-the-route?ActivityName=Rock-climbing
Stuck rappel rope? Try the “rubber band” trick
Yep, stuck rap ropes suck. But there are a few Crafty Tricks to help you solve this.
You start to pull the rap rope, but can’t get it moving. Try a few tricks before you descend into utter despair.
You and your partner grab opposite ends of the ropes and pull, hard. One of you keeps the “pull” pressure on, while the other suddenly releases her end. The “rubber band” effect of one end of your dynamic rope “springing” upwards often will get a stubborn rope moving.
You can also do this with a Grigri or similar belay device. Crank as much tension as you can on the rope through the Grigri, and then pull hard on the handle to open it. The release in tension might be enough to free your rope. (This clever Grigri tip is from Andy Kirkpatrick.)
Slinging a boulder for an anchor - two cautions
When you put a sling around a boulder for an anchor, the angles can get wide very easily, magnifying the load.
A common anchor on alpine routes is the simple sling around a boulder or rock spike. Even though the boulder itself may be super solid, there are some things to watch for when using this method.
1) Check the boulder carefully all the way around for any sharp edges. A new sling that can hold 20kN can cut very easily under tension combined with the sharp edge of rock or a crystal.
2) A short sling around a large boulder may make a wide angle in the sling that put a larger-than-ideal load on the sling material. (An angle of 90 degrees or less is the rule of thumb, and 60 degrees or less is ideal). Solution: Use a longer sling to make the anchor angle smaller. The diagram below shows how a small change in sling angle and greatly increase the forces on your anchor.
The diagram is from the excellent book "The Complete Guide to Climbing and Mountaineering" by Pete Hill.
DIY - Mark your tent stakes for easier tracking
Dang, those little tent stakes are easy to lose if you put them down for a moment and don't remember where. Here’s a tip to help them stay found.
How many of you have had this situation happen? It’s early in the morning and you’re about to strike your tent. You casually pull the stakes, maybe toss them on the ground, rocks, snow. After the climb you get home and find you now have 7, not 8 stakes. Here’s two tips to help you out.
1) Spray paint part of each stake for easy visibility. A clean way to do this without having to hand hold each stake is to get a piece of scrap cardboard from a box. Make a small hole or slit in the cardboard for each stake. Shove about 3/4 of the stake through the cardboard. Spray paint one to two coats of some kind of easy to see color on the top of the stake. Day-Glo Orange is a good choice, as its easier to spot. Rustoleum brand works well.
2) To make sure you don’t lose any, store them in a Zip-lock bag and write the amount of stakes in the bag on it with an indelible marker. That will make a no-brainer out of the “how many stakes did I bring" question.
Is it a knot, hitch, or bend?
Does every climber need to know these definitions? No. But for the Type A personality, (which is probably most of us climbers) the difference between these three different terms is actually quite interesting.
Not all “knots” are true knots. Technically, a true knot is capable of holding its form on its own without another object such as a post, eye-bolt, or another rope to anchor it.
Example: Figure 8 on a bight
A hitch, by contrast, must be tied around something to hold together; remove the thing it’s tied to, and a hitch falls apart.
Example: clove hitch. Unclip this from the carabiner, and you don't have a knot at all.
A bend is a knot used to join two rope ends. Example: flat overhand bend
(Formerly known as the "EDK", or "European Death Knot"; let's not use that term anymore, OK?)
In practice, we use “knot” as an umbrella term to cover all these types, but the distinction is useful to know.
If the context makes it unclear what you mean, you can use the term “hard knot” to distinguish a true knot from a hitch or bend.
Shorten a sling with carabiner wraps
Sometimes, to better share the load on an anchor, it's helpful to shorten a sling just a centimeter or so at a time. Here's a nifty way to do it.
Often it's handy to temporarily shorten a sling or cord by just a cm or two, typically done when anchor building. Doing this can help fine-tune anchor load distribution by shortening the arm that's going to your strongest piece, adjust a cordelette if the direction of pull has changed a bit, or shorten one sling if the bolts you’re clipping are not quite in the same horizontal plane.
One easy way to do it is to simply wrap the sling a few times around the carabiner. With a skinny Dyneema sling like this, each wrap shortens the sling about 2 cm.
Probably best not to use more than two wraps. If you need to shorten your sling more than that, it’s probably time to rerig your anchor.
Other methods: put some twists in the sling, or tie a clove hitch.
Safety note: Don’t do this unless you're dealing with a completely static anchor. If you do this on lead the sling loops can loosen in such a way as to slip down over the gate and then when loaded can open the gate. That may be hard to visualize, but if you take the setup below, and jiggle it around a bit as might happen on a long pitch, and then just keep randomly loading it, one of those extra wraps could loosen up, slide around, and potentially open the gate.
2023 Update:
I’ve received a few frosty comments on this technique over the years, most of them saying something along the lines of “this is going to weaken the carabiner, because you're putting the load closer to the gate”, or something like that.
I was curious if this has any merit, so I had my buddy Ryan at HowNot2 test this. Guess what?
It DID NOT weaken the carabiner
It DID weaken the sling.
Ryan did two different break tests on this with a Dyneema sling. First test the sling broke at 12.4 kN, the second test is broke at 15.4 kN. The sling was rated (I think) 22 kN.
Would this be different with nylon? Probably. Is this concerning? Maybe. Does it concern me? Not really, because these numbers are still significantly higher than you're ever going to see in any recreational climbing situation. But it’s still an interesting data point that I wanted to share.
I don't think I can embed this short form YouTube video in my webpage, so here's a link to see it yourself.
Screen grab from Ryan's video is below.
Pros and cons of the Garda Hitch
The Garda hitch is an old-school method to make a one-way ratcheting knot. This can occasionally be useful for hauling a light load, and in some self rescue scenarios. However, it does have a few significant downsides, and there are some modern tools that can usually do the job better.
Do you need to haul a small load? Did you forget your Petzl Traxion or Tibloc? Might be time to break out the old-school Garda hitch, aka “alpine clutch”.
The Garda hitch is a one-directional, self-locking hitch that lets you haul, but lets you relax your grip when you need a break, capturing your hauling progress.
To haul, simultaneously pull UP on the load side of the haul rope and DOWN on the brake side of the rope. Don’t just pull down on the brake side, because the garda hitch adds a LOT of friction. An informal test I did with a spring scale and a 10 pound barbell weight showed it took about 60 pounds of pulling force to lift a 10 pound weight through a Garda hitch; just 17% efficient. That is terrible!
The Garda hitch can work (reasonably) well when you create slack from doing something else, and then pull the slack rope through the hitch. If the rope has any kind of load on it, it's going to be very difficult to pull through. So, be sure you lift UP on the load side, and not just pull DOWN on the brake side.
Locking the knot is simple: just let go.
A few notes:
Ideally, use identical snapgate carabiners. Some people think it works better with oval carabiners, but personally I don't think they make much of a difference. You can hang two quickdraws together and use the bottom two carabiners.
Avoid locking carabiners with a sleeve, as the sleeves can prevent the rope from locking down properly.
Adding the girth hitch from the anchor sling is optional. But, in my experience having the top of the carabiners held together makes the hitch better behaved. Try it with and without and go with what works for you.
While some sources suggest this can be used in a crevasse rescue operation as the progress capture, many folks think this is not such a great idea because the hitch can be a little squirrely if the carabiners are not properly oriented, it's hard to release under load, and depending on how it's configured, it can add a LOT of friction to your hauling system. The few times I've used it, it's been for non-critical situations such as hauling up a backpack. (Having said that, I recently went to a crevasse rescue clinic taught by a pro guide, and he used a Garda as a progress capture in a 6:1, creating slack and then capturing it with the Garda.)
It's important to monitor the Garda hitch carefully. If you get a loop of slack rope above the carabiners, weirdiosities can happen and the entire thing can unclip itself! Yikes! (Another reason why I am not a fan of this for rescue purposes. )
Downsides to the Garda hitch:
Lots of friction. Yes I mentioned that, but it's worth mentioning again.
Very difficult to release under load.
A bit tricky to remember which is the load strand and which is the haul strand.
Depending on the carabiners used, it can be a little wonky and unreliable. Adding a girth hitch to squeeze the tops of the carabiners together, as shown in the previous photo, can help with this.
This hitch works best if the carabiners are hanging free instead of lying against the rock. When you start hauling, the rope will run along the spine of the carabiner, see photo below. If the carabiners are resting against the rock, it could have the rope rubbing against the rock, creating extra friction, or even do something weird to the carabiners or so they don't “lock” together as you expect them to.
It usually flips after it’s loaded and looks completely different than how you originally tied it, which is a little unnerving! There is no other climbing knot that does this. See photo below.
Having said that, it can be used for crevasse rescue; in this case, to ascend a rope. Here's a great video on crevasse rescue techniques from some top German guides. Watch the video below, starting at around 3:15, to see the demonstration..
Here's how to tie it.
Start with two identical carabiners (non-lockers preferred) clipped to the anchor, gates facing down and out. Clip the rope through both carabiners.
In the photo below, the hauling rope is on the left (purple carabiner) and the loaded rope is on the right (blue carabiner).
in the haul strand of the rope on the left, make a loop as shown.
Clip this loop into the right side carabiner.
Done. If you've tried it correctly, the haul strand should be coming down between the two carabiners. Pull on this, and the load will come up. If you stop pulling, the load tensions the carabiners together, pinching the rope.
Keep your water from freezing in a snow camp
Camping in sub freezing conditions? Drinking water is a valuable commodity. Here's how to keep it from freezing.
When you're in a frozen environment like a Denali high camp, liquid water is precious. After you melt snow, preserve that water by burying your pots of water.
You need a pot of water, a stuff sack or large plastic bag that goes over the pot (this is essential to avoid frozen ice against the pot the next morning), four wands, and a shovel. Bury your pot about 10 inches below the snow’s surface and cover it with snow (if powder is not available, use the shovel to pulverize snow as much as possible). It is key not to leave any air pockets. Use the wands to locate it the next morning. Even if it’s 60 below, your water will not be frozen! This works with water bottles as well, but you might have to bury those a bit deeper.
More tips:
If your water is in bottles, store those upside down so any ice, if it starts to form, will do so on the bottom, not the lid.
To keep the cap from freezing to the bottle you can coat the threads of your bottle with vaseline or lip balm.
If you have a platypus-type bottle, you can wrap the tube in foam insulation, and be sure to blow water back into the bladder after you take a sip so it won’t freeze in the tube. (Better yet, don't take a water bladder in the first place, they are prone to all kinds of problems when alpine climbing.)
If the water bladder water line freezes, just put the line under your jacket next to your skin (not as bad as it sounds, really!) Your body heat will melt the ice in a few minutes.
Get water on the go - 3 tips
Climbing on snow or hiking near mountain creeks? Here’s 3 tips to keep to you hydrated.
Here are some tips for “water harvesting” on the move.
1 - If climbing or hiking across a snowfield, keep your water bottle easily accessible. Frequently add handfuls of snow to your water, without stopping. On a warm, sunny day, this snow will melt or form a drinkable slush — bring a straw and some Gatorade powder for a poor-man’s Slurpee. (One more reason not to use a water bladder - you can't easily refill like this.)
When you grab or cut snow chunks to add to your water bottle, collect from the bottom edge of a snowfield or serac. This snow is heavily saturated with percolation and will add more water than the same snow volume gathered from lighter, fluffier snow.
2) Water running down a rock face face in a broad, yet shallow, curtain can be hard to collect. Here’s 2 tricks.
A - Carry a small length of aquarium tubing type hose; buy it any a decent hardware store or aquarium shop. Use it as a flexible straw to suck up water that you can't reach. (This is especially handy in desert areas, where water may be just a tiny trickle.)
B - Remove your jacket and long-sleeved shirt, and then spread and flatten your hand across the rock, giving the wet slab a chest-level “high-five.” The water will collect on your fingers and run down to your elbow in a stream; fill your bottle from this drippage point. (This last tip and image are from Climbing magazine.)
Face your tent door into the breeze to avoid bugs
Mosquitos. We all hate ’em. Here's a tip to help keep them at bay.
When it’s breezy, mosquitoes will congregate on the lee side of objects to avoid being blown away. So pitch your tent door into the breeze. You’ll be able to enter without bringing the swarm in with you.
Ridgelines often have more wind than hollows or valleys. If it's really buggy, try to camp on a ridgeline if you can.
Face the door of your tent toward an oncoming breeze to help avoid mosquitoes.
The three types of mechanical advantage
Mechanical advantage (MA) systems have been described as like a blind date: what’s promised is always better than what's delivered. There can be a significant difference between theoretical, calculated, and real-world mechanical advantage. Learn what these are and see some examples.
This article has some diagrams made with the very cool rope rigging software, vRigger.
Use discount code “ALPINESAVVY” to get 10% off vRigger software.
Short version : sort of like a blind date, the mechanical advantage you’re hoping for is never as good as what was promised. =^)
Mechanical advantage (MA) systems are typically described with a nice, tidy number, like 2:1, 3:1, or 6:1. In theory, this means with a 3:1 system, one unit of input force (that’s you pulling on the rope) results in three units of output force that gets applied to the load.
So in theory, with a 3:1, you can move a 100 kg load by pulling with only 33 kg of force. Wouldn't that be nice!
While this is a convenient number to generally describe an MA system, unfortunately you’ll never achieve that in real life. Why?
There actually three different flavors of MA that need to be considered:
Ideal
Theoretical
Actual
Let’s have a look at each one.
Ideal MA
With a 3:1 system, you need to pull 3 meters of rope through the system to move the load 1 meter. With a 6:1 system, you need to pull 6 meters of rope to move the load 1 meter. Pretty simple idea, right?
Unfortunately this would only be true in an imaginary universe with no friction. While the ideal MA is useful for generally describing a system, it doesn’t tell you much about the pulling force that’s actually applied to the load. So for now, we’ll step away from it.
Theoretical MA
In the real world, every time the rope changes direction, friction enters the system. Your pulling energy, instead of being 100% transmitted along the rope, is converted to heat from the friction, and this heat is lost to the atmosphere. With a good quality pulley this friction will be minimal. With a carabiner this friction is substantial.
The term used to describe friction in rigging systems is efficiency.
A good quality pulley is around 90% efficient. That means that 90% of your pulling force gets moved through the system and you only lose 10% to friction. That's good! On the other hand, using a carabiner, which is about 50% efficient, means that you lose 50% of that input force to friction, and only half of it comes out the other side of the carabiner. That's not so good!
By using a technique called the “T method”, it’s fairly easy to calculate the friction involved in your system to get a more realistic view of the “pull” needed to move your load.
Here’s a quick example of the T method on a 2:1 system, one with a pulley and one with a carabiner. (This diagram was made with a very cool software, vRigger.
Use discount code “AlpineSavvy” to get 10% off vRigger software.
When you start looking at Theoretical MA, things get interesting!
On the left, using a high-efficiency pulley on the load, you need to pull with less force, but you also have a higher load on the anchor.
On the right, with a low efficiency carabiner on the load, you need to pull with more force, but that puts a lower load onto the anchor.
images made with vRigger
Have another look at “El Puerco” at the top of the page. Both set ups are for a theoretical 3:1.
The one on the left is set up with good quality pulleys at every change of direction. With that, you get about the best possible MA of 2.7 to 1.
However, the system on the right, which is one often improvised by climbers with minimal gear, introduces a lot more friction into the system from the Grigri and carabiner. This gives a rather pathetic calculated MA of 1.65 to 1. Big difference!
Side note: Do mechanical advantage systems magnify load on the anchor?
An MA system, in theory, does not magnify the load on the anchor. At the theoretical level, with a simple system like a 2:1 or 3:1, you're never going to apply more load on the anchor then the weight of your load.
At rest, the anchor sees the weight of your load.
When you're pulling, you are supporting some of the load with your hand, so that gets subtracted from the load on the anchor.
However, when you start adding in real world factors, such as friction of the rope running over an edge, forces can start to become higher than the load. But, at a theoretical level, it's important to know that the MA system itself does not magically increase anchor force.
Actual (aka real world) MA
Finally, there’s the third flavor of mechanical advantage, actual.
Actual MA is the actual result of all the messy and hard-to-quantify variables encountered when actually trying to pull something. For example:
the rope running over a ledge or through climbing protection (LOTS of friction can come from this; ledges are bad)
rope strands that cross, are twisted or rub (try to minimize this)
whether your rope is dynamic or static (static is better)
Whether your rope sheath is old and crusty or new and slippery (slippery is better)
the diameter of the rope (smaller is better)
the diameter of your pulley wheel (larger is better)
the angle of your pulling hands relative to the anchor (try to pull in line with the other rope strands)
So, squirrely things like that! You might have calculated your MA with the T method perfectly, but when you start introducing some of these other factors into your system, your real world MA decreases even further. About the only way we can measure this is using scales and load cells with a real load.
So, the takeaway: theoretical MA will always be greater than calculated MA, and calculated MA will always be greater than real world MA.
The 3:1 Spanish Burton haul system
After you have the basics of a 2:1, 3:1 and 6:1 hauling system dialed, rope geeks and mechanical advantage fans might want to learn some more esoteric rigging. Here's one of them, the 3:1 Spanish Burton. It lets you pull down, instead of up, which could be helpful in a vertical haul. Practice with it, it's fun!
When learning mechanical advantage for rope rescue, I think it’s important to start with the basics: a 2:1 “C” and a 3:1 “Z”.
Once you have those dialed, one can be added on top of another one to create what’s called a compound 6:1 if you need extra pulling power.
In just about every rope rescue scenario, some combination of a 2:1, 3:1 or 6:1 should cover all of your needs.
However, if you like playing around with ropes (and I know you do, otherwise you wouldn't be reading this) here’s an interesting one to learn: the 3:1 Spanish Burton.
(No, I have absolutely no idea why it’s called the “Spanish Burton”. Guessing it had to do with a guy named Burton who found himself on a Spanish sailboat about 400 years ago . . . )
Why might the Spanish Burton be applicable in rope rescue?
In a vertical lift, you can pull DOWN with your body weight to lift the load. (In a more typical 3:1 Z drag, you need to pull UP.) For a vertical lift, it's helpful to have the anchor point as high up as possible so you can use your body weight most effectively.
It lets you set up a 3:1 with basically zero extra rope. Such as, you're only carrying a meter or two of extra rope, your partner falls in a crevasse, and you need to set up a 3:1. (Yes I know, not super-practical, but could be helpful.)
Spanish Burton rigging notes . . .
The purple sling is tied to the green rope with a Klemheist hitch. You could also use another rope grab here, like a Tibloc. (I used a sling here; any bit of cord or sling will work.)
The 120 cm purple sling means you need to reset the system often. If you have more room to work, you could replace this with an untied cordelette, which would give you a much longer pull.
The always handy Petzl Micro Traxion is the progress capture pulley on the anchor.
We have two “traveling” rope grabs moving toward each other. This means you need to reset your system more often, which can be a hassle if you have a small workspace, or no big deal if you have a large area to work in, like on a snowfield.
Note that the Spanish Burton increases the load on the anchor. For example, if you pull with 1 “unit” of force, this puts a load of about 4 “units” on the anchor. Compare this with a traditional 3:1 Z drag. With a Z drag, if you pull with 1 unit of force, you have 2 units of force on the anchor. If your anchor is unquestionably strong, no worries. If it's not, this may be something to consider.
Using the “T method” to determine the mechanical advantage
There's a technique called the “T method”, or the tension method, which can determine the mechanical advantage of many rigging systems.
We start with an input force of 1, that's your hand pulling on the purple sling.
At the blue pulley, the input force is doubled to 2. That gets transmitted to the prusik hitch, and to the green rope.
The 2 on the green rope goes into the Traxion. That is doubled for a total force of 4 on the anchor.
The input force of 2 comes out of the Traxion on the other side as 2.
This force of 2 travels down the green rope on the load side. There, it meets the force of 1 on the left side of the purple sling.
You add those together for total mechanical advantage of 3:1.
If you want to learn more about this, here’s an excellent tutorial video on how to count tensions using the T method.