I know I’ve been a bit quiet this month and haven’t posted many new articles. But I think this one will make up for that. I’ve been pretty busy writing this tool in a form that I could share on here with everyone.
This is my expedition fuel planning tool.
Planning for fuel usage can be kind of tricky. Different conditions, the choice of fuel type, the type of pot used, how windy it is each day, altitude, etc all have an effect on the fuel consumption of your stove.
I’ve been playing around with my set up, doing some experiments. I then used the data from those experiments to create a model of fuel usage that I could use to predict how much fuel I would probably need on a trip of a given duration.
This model is what is known as a Monte Carlo simulation. It runs many many scenarios given a set of data, and then outputs the average result of those scenarios.
How to use the tool
To use the tool, you will need to do two sets of experiments. You’ll notice I say “repeat several times” for each experiment. How many is “several”? Well, the more the better. At the most, 30 iterations. Empirically, 30 iterations will give us a normally distributed sample, no matter what the underlying distribution looks like. In reality, I’d say 5 or 6 runs should be plenty.
Boil 1 liter of water using your stove, pot, and fuel in the way you intend to use it on the trip. Time how long it takes to reach a boil. Repeat several times.
Calculate the mean and standard deviation (MS Excel will do this for you quite easily).
Measure a specific amount of fuel into your fuel bottle, and boil 1 liter of water. Time how long it takes for that water to boil. Measure the fuel remaining. Repeat several times.
Calculate the mean and standard deviation of how much fuel your stove uses per minute. Fluid ounces burned / minutes to boil is the formula you’ll use.
Those four numbers you calculated (mean boil time, SD of boil time, mean fuel usage, and SD of fuel usage) will be entered under “experimental data”.
Then, you select the type of fuel used (for now, I have only entered white gas and kerosene. . . if you really want to use this for unleaded auto gas or jet fuel, I can add that easily enough).
Finally, enter the volume of water you plan to boil each day, and the length of your trip in days.
For now, I output the mean, standard deviation, and mean plus two SDs in fluid ounces of fuel. I also calculate the mass of the fuel for the mean plus two SDs.
Two SDs results in a pretty conservative number in terms of probable fuel requirements. Lots of industries like to use six SDs, and you can easily calculate that yourself, or, if enough people ask, I can add that calculation to the tool. You’ll have to decide your risk tolerance for yourself.
Precision and Accuracy
This tool is written in PHP, and the results are similar to the results I get when using MS Excel for the calculations. I used the mt_rand function in PHP, as the documentation claims that it is a better random number generator than the rand function. I didn’t actually plot the results from mt_rand to see the distribution. I wrote all the statistical procedures myself (even for the mean and standard deviation calculations), so they depend on good inputs (e.g. real random numbers and solid experimental data).
I’d really like to hear feedback on this tool. With some more users playing with it, perhaps it can be made even better.
Here is an AP article. Humar has been found dead. It has been a rough year for climbing with so many lost. RIP
Tags: Tomaz Humar
Measuring the weight of your equipment, food, fuel, and clothes is an absolute necessity. The more weight you need to move, the more energy it takes, and the more money it takes.
Yes, I said money. Airlines charge by weight. If your baggage is over their limit, you will be paying by the kilo or pound. That is money and that is a cost for your expedition planning.
Base weight system
In my opinion, the “base weight” system is probably the worst way categorize weight. For anyone familiar with basic accounting, the base weight system reminds me a lot of transfer pricing. Basically, it has a high potential for abuse.
Transfer pricing is how a company sells things within the organization. Thus, this is a major system for allocating profit to different departments.
Base weight is subject to the same kinds of games that we see in transfer pricing. For example, if someone wants to reduce their base weight, they simply remove the item from the pack, and place it in a pocket or in their hands, and just like that, base weight is reduced.
This is useless for anything other than trying to entertain yourself with pissing matches about who has the lowest base weight and what base weight is considered light or ultra light or super light or amazingly light.
Fixed and Variable system
The system I use is very simple, much like a managerial budget (cost accounting). I have two types of weight; fixed and variable.
Fixed weights refer to the weight of things that will not change for the trip. These are the weights of items like boots, backpack, sleeping bag, sleeping pad, rope, carabiners, crampons, etc.
For a given type of trip, no matter the length, these items weigh the same over the entire trip.
To continue to use the accounting analogy, this is like the fixed costs associated with making something. You have a lease for your factory building. That cost is fixed over the term of your contract, you know exactly what it will cost you, no matter how productive you are (or how much time your expedition will take).
Variable weights are for items that change depending on the duration of the trip. The easiest examples are food and fuel. But, another example is first aid equipment. Using the accounting parallel, variable weights are just like variable costs. . .your electricity bill is a variable cost. It varies as you use more or less electricity. If you run an extra shift at the factory, your electricity bill goes up as you keep the lights and machines on for that time. If your trip goes an extra day, your food weight goes up.
The weight of antibiotics, pain meds, altitude drugs, etc for a 3 day trip is different than the weight for a 28 day expedition. The same effect is seen with gauze. To be able to change the bandages on someone during the course of an expedition requires much larger quantities than for a weekend trip that has easy evacuation possibilities for very minor injuries.
Another tricky variable weight is fuel bottles for liquid stoves. With an MSR style stove, 1 fuel bottle is a necessity and should probably be logged as a fixed weight, as part of the stove system. But as the duration of the trip increases, so too does the quantity of fuel needed. This requires more containers for carrying the fuel. These additional containers, whether they are plastic bottles or additional metal fuel bottles should be logged as a variable weight.
Water, of course, is another variable weight, as are the containers for carrying the water and, perhaps, chemical treatments for purifying the water. In many areas, there is little concern over availability of water. Following rivers, fishing on lakes, or in mountains with an abundance of glacial streams, water is everywhere and makes up a relatively small amount of variable weight. There is just no need to carry a large quantity.
However, in desert areas, water can be a significant portion of variable weight, when water suddenly is measured in days rather than in hours between streams.
Batteries are another variable weight. A lot can be done to minimize the weight of these energy sources, however, they still vary depending on the length of the trip.
Using a simple model for weight accounting results in several useful advantages. First, it is quite easy to know exactly how much weight you will be dealing with, and plan for weight decreases each day, which can correlate to mileage increases over the course of the trip as well.
Second, using this framework, it is possible to plan for expeditionary expenses, like the costs associated with shipping your gear to the destination.
Third, using empirical data, it is very possible to plan expeditions with a high degree of accuracy. Variable weights are tricky to master, as every person has preferences for how many hot meals they consume each day, what kinds of food they will eat, how they respond to altitude, how many calories they need to eat, etc. This is why experience is such a major factor in planning well.
I’ll cover more about weight accounting, cost accounting, and expedition planning in the next few weeks.
One of the biggest complaints I hear about softshell is that it weighs too much. I’ve decided to gather some examples to determine whether or not that is true.
Patagonia Speed Ascent versus R2 and a Patagonia hardshell
The Patagonia Speed Ascent jacket is their high end softshell for cold conditions. It has R2 fabric as the liner, and a polyester shell that is wind and water resistant. It also has a hood.
Speed Ascent jacket is quoted as being 28 ounces.
To get the corresponding system in hardshell means an R2 jacket plus a hardshell.
R2 jacket is 14.1 ounces and has no hood.
The Stretch Element hardshell jacket is 19.6 ounces.
The Rain Shadow hardshell jacket is lighter at 13 ounces.
At best, softshell is over a quarter pound lighter (28 ounces versus 33.7 ounces), at worst, it is equivalent (28 ounces versus 27.1 ounces plus a fleece hat to make up for the lack of hood).
Marmot Driclime Windshirt versus the Ion Windshirt plus a baselayer shirt
On the other end of the spectrum from the Speed Ascent jacket is Marmot’s Driclime softshell. This is a very light polyester shelled jacket with 2.7 oz/yard lining.
Driclime windshirt is quoted as being 11 ounces.
To get an equivalent product, we need a light baselayer and a light shell.
The Ion windshirt is 5 ounces, and it has an attached hood.
A Marmot lightweight crewneck base layer shirt is 6 ounces.
In this case, the edge goes to the Ion windshirt plus baselayer as the Ion has a hood that adds some weight. (11 ounces versus 11 ounces).
This quick comparison shows that softshell is roughly equivalent to a similar system of hardshell plus insulation. The weight argument doesn’t hold.
One of the key differences between hardshell and softshell is the breathability/waterproof tradeoff. I’ll not debate that here, as different people want different things. Some prefer the most breathable layers they can get as long as they are wind resistant and shed some water. Others want absolute waterproof layers and don’t worry about breathability.
In the past, I compiled data and compared the various –20F high quality down sleeping bag options. Now, I’m doing the same comparison chart of high quality down (700 fill power or greater) sleeping bags for 3 season use. These bags are rated in the 15F to 25F temperature range.
As I covered before, fill power is the metric for down quality. Fill power multiplied by ounces of fill gives the total volume of down fill. I cite the total volume of down fill in my chart.
There are more sleeping bags in this list. I’ve chosen to simply highlight the three best in each category using italics. Thus, the three lightest weight bags, the three most inexpensive bags, and the three highest fill volume bags will each be in italics.
Means and standard deviations have been calculated, and are reported at the bottom of the chart.
|MFG||MODEL||TOTAL WEIGHT||PRICE||FILL VOL|
|Western Mountaineering||Apache MF||33||410||16150|
|Western Mountaineering||Badger MF||40||445||19550|
|Western Mountaineering||Apache GWS||38||490||16150|
|Western Mountaineering||Badger GWS||44||540||20400|
|The North Face||Nebula||49||369||14400|
|The North Face||Hightail||32||379||17000|
|Mountain Hardwear||Spectre SL||44||430||12800|
As always, the data is compiled from the manufacturers.
In a previous post, I discussed the development of an efficiency factor for regular sized sleeping pads that takes into account warmth and weight. The warmth is given by the R-value, a standard measure used in the construction industry for insulation. I standardized the weight with the surface area, but I only included a chart with “regular” size pads. I was asked how well this held up with pads of different sizes. Well, because the efficiency factor is a function of the surface area divided by weight, it should be able to cope with pads of different dimensions.
Just like before, the efficiency factor is calculated such that a lower number is better. I’ve sorted the chart on that efficiency factor, putting the most efficient at the top.
I put a lot more data into the spreadsheet and I discovered something interesting. For the most part, smaller pads have a slight advantage. However, the Exped Downmats and Synmats seem to favor the larger mats. Perhaps this is because of the valve and pump weight being spread over more surface area.
I also multiplied the original efficiency factor by 1000 to make it easier to read. This doesn’t actually have any effect on the factor because it is uniformly applied to the original factor. It simply changes the decimal position.
I plotted the efficiency curve and noticed that it slowly increases and then suddenly goes up quite rapidly. It looks like the main inflection point occurs somewhere between 6 and 8.
Efficiency is not the only thing that is important though. One of the big things I look for is how small I can pack the pad.
I really don’t like having things hanging off my backpack. The streamlined shape of most internal frame packs is ruined when a big pad is strapped to it. This causes it get snagged on tree branches and brush. For me, this means I need a very small package that can fit inside my pack.
However, others do use their pads as a frame in ultralight packs. These folks won’t necessarily care about packed volume as much as the structure and rigidity of the pad when it is in the back of the pack acting as a framesheet.
For this reason, I’ve not tried to create a more unified factor that includes the packed volume of the pad. Users will have to decide for themselves what is important.
To give a complete picture of these pads, I’ve included the MSRP per the manufacturer or distributor, or if that was unavailable, I used information from REI to fill in the gaps.
Despite being included in the efficiency factor, I’ve included R-value and weight in the chart.
This way you can see better whether a pad fits your needs in terms of weight, warmth, efficiency, packed volume, and cost in USD.
Here is the updated chart:
|Exped Downmat 9 DLX||2.74||311||8||44.1||$ 180.00|
|Exped Downmat 9||3.00||254||8||34.6||$ 160.00|
|Exped Downmat 7 DLX||3.38||216||5.9||40.2||$ 165.00|
|Exped Synmat 9 DLX||3.38||423||6||40.9||$ 120.00|
|Thermarest Ridgerest Small||3.61||663||2.6||9||$ 19.95|
|Exped Downmat 7||3.65||254||5.9||31||$ 150.00|
|Thermarest Ridgerest Regular||3.74||1005||2.6||14||$ 24.95|
|Thermarest Ridgerest Large||3.80||1418||2.6||19||$ 34.95|
|Thermarest NeoAir Small||3.83||77||2.5||9||$ 119.95|
|Thermarest NeoAir Regular||3.89||113||2.5||14||$ 149.95|
|Exped Synmat 7 DLX||3.89||339||4.9||38.4||$ 110.00|
|Thermarest NeoAir Medium||3.94||113||2.5||13||$ 139.95|
|Thermarest NeoAir Large||3.95||175||2.5||19||$ 169.95|
|Exped Downmat 7 Short||4.00||177||5.9||22.2||$ 135.00|
|Big Agnes Insulated Air Core||4.07||177||4.1||24||$ 79.95|
|Thermarest Ridgerest Deluxe Regular||4.26||1161||3.1||19||$ 34.95|
|Exped Synmat 7||4.29||308||4.9||30.3||$ 100.00|
|Thermarest Ridgerest Deluxe Large||4.36||1697||3.1||26||$ 44.95|
|Thermarest Prolite Plus Regular||4.39||199||3.8||24||$ 99.95|
|Thermarest Z-lite Regular||4.42||550||2.2||14||$ 39.95|
|Big Agnes Two Track 2″||4.49||412||6.5||42||$ 82.95|
|Big Agnes Dual Core Large||5.03||596||5||49||$ 144.95|
|Thermarest Prolite XS||5.05||78||2.2||8||$ 59.95|
|Thermarest Prolite Regular||5.05||145||2.2||16||$ 99.95|
|Thermarest Prolite Large||5.19||207||2.2||22||$ 119.95|
|Big Agnes Dual Core Long||5.26||431||5||41||$ 104.95|
|Big Agnes Dual Core||5.28||367||5||38||$ 99.95|
|Thermarest Prolite Small||5.32||100||2.2||11||$ 79.95|
|Exped ComfortFoam 7 DLX||5.82||539||4.9||57.5||$ 105.00|
|Thermarest TrailLite Regular||5.85||305||3.8||32||$ 59.95|
|Thermarest TrailLite Large||5.88||432||3.8||43||$ 69.95|
|REI Camp Bed 3.5 Regular||6.35||797||7||80||$ 99.50|
|Exped ComfortFoam 7||6.51||339||4.9||45.9||$ 85.00|
|REI Trekker 1.75 Regular||6.61||376||4.2||40||$ 64.50|
|REI Camp Bed 2.5 Regular||7.65||617||4.5||62||$ 75.50|
|Zotefoams Evazote Winter||7.73||2.06||18.5||$ 33.30|
|Big Agnes Sleeping Giant||8.53||565||3.5||43||$ 64.95|
|Big Agnes Clearview Air Pad||10.42||49||1||15||$ 49.95|
|Big Agnes Air Core||15.28||100||1||22||$ 49.95|
I’ve mentioned in the past that a good shovel is an essential tool in the mountains. They can be used to build your shelter, whether it is a snow cave or trench. A good shovel can help with snow wall construction. And, a good shovel is an essential tool should the worst case scenario happen; an avalanche.
Avalanches really have a lot of compressive force. The snow gets packed very densely, requiring a burly shovel to dig out anyone that is trapped. For this reason, I consider any shovel without a metal blade to be dangerous in avalanche terrain.
Another key feature is a shaft and handle that is comfortable enough for use to dig rapidly and furiously in avalanche rubble. I’m a tall guy, so I prefer a longer shaft. In addition, my hands are large and the way I prefer to dig, I like a D handle as opposed to a T handle.
The D handle also provides a convenient location to tie a sling. I like shovel blades that have holes in them to allow it to be slung as a deadman in an emergency.
I strongly recommend not using your shovel as a tent anchor. This makes it difficult to retrieve it to dig out your tent during a snow storm. In addition, if you have set up a base camp, you need your shovel while you head up the slope.
I like using the Voile Telepro. It is comfortable, has a really durable aluminum blade, and allows me to really move a lot of snow efficiently. The blade also detaches easily from the shaft, which makes life easier when trying to dig out the interior of a snow cave.