Margin of Error when Calculating Stove Fuel

[GreenNDark Timber]

I'm curious how much margin of error everyone uses when calculating how much fuel to bring on a backpack trip. In the past I've always just packed one of the larger 227 gram MSR canisters and it's been more than enough for my trips. I'm trying to shave some weight for an upcoming hunt and could drop about 7 oz if I can get by with the smaller 110 gram MSR canister.

My hunt will be first week of Sept for 8 days at about 12,500'. My current stove setup is a Soto Windmaster Triflex (2.75 oz) with a MSR Titan Kettle (4.80 oz). The stove burns approximately 6.5 grams of fuel to boil 2 cups of water (1500' elevation, 70 degree, no wind) and I boil 2 cups twice per day. This would put me using 104 grams of fuel with no loss factor for wind or temp. Is trying to get by with a single 110g canister cutting it too close?

Would going to a pot with a heat exchanger like the Firemaple Petrel pick me up enough efficiency to make any difference? Open to suggestions.

 

[S.Clancy]

Yes. You will absolutely run out of fuel. It's going to be much colder at that elevation when you are boiling in the morning and evening.

 

[Grady.J]

Colder air temp, wind, altitude, and probably colder starting temp for the water. I doubt there's an equipment option that could make a 110g can work for what you want it to do.

But, if you run out, it's just cold food, not enjoyable but not the end of the world. I think if you want something hot twice a day, the 227g is necessary.

 

[antaresproper]

Does an aluminum roasting pan cut to fit as a windscreen and an insulated pot cozy weigh more than the delta between the canisters?

Do you need the water to boil or just be hot?

Instant coffee, instant oatmeal, and I like the low water freeze fried meals. It may have to sit and soak a bit longer but faster than waiting to boil then waiting for it to cool.

 

[Koda_]

Use your MSR Kettle over the campfire in the evenings to conserve fuel...

 

[BBob]

I shoot for 20-25% margin but I’ve cut it closer. You need a more efficient system to do what you want. The Petrel might do it but it would be close. The non-existent Sterno Inferno can do it with a BRS stove for 8 days at altitude in September with fuel left over. There are several discussions on this forum that might give you more info. I have yet to actually test my Petrel with the Windmaster or BRS but others have and it won’t match the Inferno. I monitor pretty close and try not to hit full boil saving a little here and there.

 

[GreenNDark Timber]

Appreciate the input. I pretty much figured my current setup would fall short. I'll probably buy the Petrel pot and a BRS stove since both are a pretty low cost of entry and test boil times with both stoves and see how close I can get. With a 25% loss factor, my current setup should get me through 6 days. If I can't quite get there I'll decide if I want to do cold breakfasts for a couple days and just make a small fire for the last day or two's dinners or just carry the extra weight.

 

[S.Clancy]

Appreciate the input. I pretty much figured my current setup would fall short. I'll probably buy the Petrel pot and a BRS stove since both are a pretty low cost of entry and test boil times with both stoves and see how close I can get. With a 25% loss factor, my current setup should get me through 6 days. If I can't quite get there I'll decide if I want to do cold breakfasts for a couple days and just make a small fire for the last day or two's dinners or just carry the extra weight.

For an extra 6-7 oz I think the extra weight for hot food is manageable....

 

[BBob]

I'll probably buy the Petrel pot and a BRS stove

Your Windmaster Triflex is a much better match for the Petrel than the BRS. You can use it with no modifications.

 

[Dos Perros]

It's 7 ounces. You'll drink that much water putting your lips to your Nalgene one time. My personal opinion, don't invest the mental space in worrying about stuff like this. Just take the big feller and put all your focus on killing something.

 

[WCB]

Start cutting the tags off your clothes, handle off the toothbrush, and extra length of straps off your pack. Probably can find 7oz somewhere else. And if not...it is 7oz. Do an extra squat a day.

 

[GreenNDark Timber]

I thought this might be some low hanging fruit to cut almost half a pound but it sounds like I'm barking up the wrong tree. I'll just stick with the bigger canister and throw a few extra packs of coffee in to enjoy mid-morning with my extra fuel. My future self on day 7 of the hunt is probably thanking you for talking sense into me.

 

[Koda_]

I thought this might be some low hanging fruit to cut almost half a pound but it sounds like I'm barking up the wrong tree. I'll just stick with the bigger canister and throw a few extra packs of coffee in to enjoy mid-morning with my extra fuel. My future self on day 7 of the hunt is probably thanking you for talking sense into me.

If one is frugal and goes thru their total load out shaving ounces here and there they might save a couple pounds, but the real place to shave pounds is the baseweight items, and those are the expensive ones. Pack, bag and shelter. A true UL baseweight should land under 10lbs, L baseweight under 15lbs.
lightweight, cheap, strong.... pick two.

 

[MTHokie]

If one is frugal and goes thru their total load out shaving ounces here and there they might save a couple pounds, but the real place to shave pounds is the baseweight items, and those are the expensive ones. Pack, bag and shelter. A true UL baseweight should land under 10lbs, L baseweight under 15lbs.
lightweight, cheap, strong.... pick two.

Yep. This.

 

[35WhelenAI]

From 40 years in Colorado and many, many, many trips to higher elevation... water boils at a lower temperature at higher elevation. Just because the water boils (and will appear to come to a boil fairly normally because it boils at a lower temperature), it is NOT as hot as you are used to or need for cooking times. It's going to take longer to cook by boiling as a result, ergo more fuel.

At 12,500' boiling occurs at around 188 deg F. Living and playing at elevation, those are just common knowledge things.

You need to have fuel to cover your bases and butt, not worrying about 7oz. Taking more fuel is where you need to be.

As an aside, worrying about 7 ounces... You will be 2 MILES higher in elevation than what you share in your original post. Have you spent time at elevation before? What is your acclimation plan? Is water accessible at those elevations, you WILL dehydrate, once you realize, it's too late. Margin for error is thin at elevation if you haven't been there before. Sweat and moisture evaporates so quickly you don't realize you're sweating. Altitude sickness not only sucks, it's plain dangerous.

Be sure you are well versed before you go. A learning curve at elevation is not a fun thing to be playing with on the fly.

 

[taskswap]

Don't forget a windscreen. Titanium roll-up if you're feeling flush or just some foil. It's a nice-to-have lower down in the woods, but a must IMO higher up plus breezy. Has a big impact on fuel usage...

 

[GreenNDark Timber]

From 40 years in Colorado and many, many, many trips to higher elevation... water boils at a lower temperature at higher elevation. Just because the water boils (and will appear to come to a boil fairly normally because it boils at a lower temperature), it is NOT as hot as you are used to or need for cooking times. It's going to take longer to cook by boiling as a result, ergo more fuel.

At 12,500' boiling occurs at around 188 deg F. Living and playing at elevation, those are just common knowledge things.

You need to have fuel to cover your bases and butt, not worrying about 7oz. Taking more fuel is where you need to be.

As an aside, worrying about 7 ounces... You will be 2 MILES higher in elevation than what you share in your original post. Have you spent time at elevation before? What is your acclimation plan? Is water accessible at those elevations, you WILL dehydrate, once you realize, it's too late. Margin for error is thin at elevation if you haven't been there before. Sweat and moisture evaporates so quickly you don't realize you're sweating. Altitude sickness not only sucks, it's plain dangerous.

Be sure you are well versed before you go. A learning curve at elevation is not a fun thing to be playing with on the fly.

All good points. Yes, I've spent time at elevation before, every year for about the last 25 yrs. I hunted this same basin several years ago for 10 days, there's plenty of water and I'll be acclimated (as best I can). It's a long way in and it's a long way up and a hunt that's mostly type 2 fun. That's why I'm working on shedding weight where I can logically.

I realize it's only 7 oz....for this item, and that seems like small potatoes. But I'm not just looking at the stove and fuel. I'm looking at my shelter, pad, tripod, water system, clothing, basically everything I can to make adjustments where it makes the most practical and financial sense.

 

[Koda_]

I'm looking at my shelter, pad, tripod, water system, clothing, basically everything I can to make adjustments where it makes the most practical and financial sense.

Ive been down this road. Start with your baseweight and work out to the small stuff later. Otherwise it wont amount to much. Trust me this works. Take your current baseweight and subtract at least 15lbs and the difference is what your carrying you dont need to.
And there's no financial sense in going UL, its expensive. There are some more affordable options and Ive chatted with some really hardcore UL thru hikers on a budget that didn't invest much but they sacrifice their comfort (and in some cases their safety). Thats fine on a thru hike, backpack hunting is way different because what weight you can drop in your baseweight is often added back in hunting and meat hauling gear.

Personally, I would ditch the tripod. Learn to shoot over your pack or if you must get some UL shooting sticks Brownells sells one that weighs 8 oz.

Ideas.
Pack: 5lbs max for a meathauling pack. Lighter if not. Kuiu pro series, or Seek Outside perigrene are the lightest meat hauling hunting backpacks that Ive found.
Shelter: 1.5lbs per person max, Mine is about 3lbs cause I like the extra room for stuff at night. 6 moon designs Haven with net tent.
Bag: 4lbs max. this is the item that will cost you the most. Marmot Lithium 0deg down, 3.3lbs.
Sleeping pad: Thermarest Neo Air, .8lbs

Total baseweight: 11.3lbs. Cost: priceless and will last you years of adventures.

 

[GreenNDark Timber]

Ive been down this road. Start with your baseweight and work out to the small stuff later. Otherwise it wont amount to much. Trust me this works. Take your current baseweight and subtract at least 15lbs and the difference is what your carrying you dont need to.
And there's no financial sense in going UL, its expensive. There are some more affordable options and Ive chatted with some really hardcore UL thru hikers on a budget that didn't invest much but they sacrifice their comfort (and in some cases their safety). Thats fine on a thru hike, backpack hunting is way different because what weight you can drop in your baseweight is often added back in hunting and meat hauling gear.

Personally, I would ditch the tripod. Learn to shoot over your pack or if you must get some UL shooting sticks Brownells sells one that weighs 8 oz.

Ideas.
Pack: 5lbs max for a meathauling pack. Lighter if not. Kuiu pro series, or Seek Outside perigrene are the lightest meat hauling hunting backpacks that Ive found.
Shelter: 1.5lbs per person max, Mine is about 3lbs cause I like the extra room for stuff at night. 6 moon designs Haven with net tent.
Bag: 4lbs max. this is the item that will cost you the most. Marmot Lithium 0deg down, 3.3lbs.
Sleeping pad: Thermarest Neo Air, .8lbs

Total baseweight: 11.3lbs. Cost: priceless and will last you years of adventures.

This is a mule deer hunt and the tripod is for my binos and spotting scope. I'll be shooting a recurve, it's tough to shoot one of those off a pack

My base weight (for the items you listed) is already lower than that. I'm just fine tuning and not expecting to be able to reduce my total pack weight by more than a few pounds total.

 

[35WhelenAI]

All good points. Yes, I've spent time at elevation before, every year for about the last 25 yrs. I hunted this same basin several years ago for 10 days, there's plenty of water and I'll be acclimated (as best I can). It's a long way in and it's a long way up and a hunt that's mostly type 2 fun. That's why I'm working on shedding weight where I can logically.

I realize it's only 7 oz....for this item, and that seems like small potatoes. But I'm not just looking at the stove and fuel. I'm looking at my shelter, pad, tripod, water system, clothing, basically everything I can to make adjustments where it makes the most practical and financial sense.

Thanks for the backstory on that. Sounds like you are fine-tuning what you've already been doing.

Dropping body weight a few pounds, getting the cardio and endurance up allows for more comfort when you're in the woods because you're not cutting corners saving weight.