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John Abela
(JohnAbela) - MLife
JetBoil Sol Ti (titanium) Cup Resizing Modification on 11/27/2013 14:21:11 MST Print View

Hey All,

I do not really like, nor normally post my articles here at BPL, but I got something I need some help with...

Some of you folks here at BPL are waaaaaaaaay smarter in the math department than what I am (because I just downright suck at math)... and in an article I published this morning I asked for help from folks that understand the whole "when a stove is at its peak performance" from a weight-per-milage-per-fuel-consumption whatever.or.whatnot that you'all seem to have the brain-gifts for that I do not.

I have tried to post as much information as I could think of. If you need more data from me to help with calculations let me know and I can maybe/hopefully(?) provide it.


http://hikelighter.com/2013/11/27/jetboil-sol-ti-titanium-cup-resizing-modification/

Thanks to any of you math-smart people that can help me out on this one.

+John Abela

Marko Botsaris
(millonas) - F - MLife

Locale: Santa Cruz Mountains, CA
Re: JetBoil Sol Ti (titanium) Cup Resizing Modification on 11/28/2013 05:33:29 MST Print View

John,

Just my two cents. If you were modifying a more traditional stove, especially if you were changing the width of the base, but even to a lesser degree the height, then I would expect potential efficiency changes because of the way the heated air flows past the pot bottom and sides for a given stove. A good example of this is how different a cat stove will work depending on the ratio of the cat stove and pot diameters.

In the JetBoil I suppose there might be some issue w/respect to that, but in this case the heat exchanger is a constant, and we might assume to lowest order that the rate of heat *flow* into the pot would be more or less unchanged - basically less susceptible to pot shape. I don't find a lot of heated air outside my Sol Ti, so that is a good thing. It means most of the heat is efficiently transferred to the water through the heat exchanger, so for that stove expect the shape to be less of a concern.

I emphasize flow here because there are two different things which I believe you might be conflating in your blog post - heat flow and temperature. You could have a lot of heat flow into the pot, but if the heat is transferred to the water efficiently the actual temperature may not be that great. In practice the having water in the pot will probably be the main thing that will prevent the temperature of the pot from getting too hot. A good heat conductor such as thin metal of any kind should spread the heat rather quickly through the metal, so it would be reasonable to assume if the pot was filled with water the water would act as a temperature buffer. At first the energy of the heat will go into raising the temperature of the water, and then after the water reaches boiling temperature the energy goes into converting the water into vapor at a constant temperature. So to first approximation I would guess that you are not going to generate a higher temperature in the heat exchanger by cutting down the pot.

Just make sure the pot is full of water at all times when you have the stove turned on. However, as many people have learned the hard way, one of the things that makes such pots efficient (a low heat capacity) is the kind of thing that will rapidly lead to a damaged pot if the water is not there. So the pot will rapidly overheat if you don't have water in it, and a cut down pot will burn more rapidly. But since you should never do this, you should not have this issue.

What may become an issue is if you boil so little water the time to boil may become unmanageably short, and maybe you will waste energy. I think turning down the burner a low as possible, as least a well as you can on a jetboil, would help both issues.

I'm not too clear on what you are trying to gain by cutting down the pot. Is it just weight? Or were you somehow hoping for efficiently. I don;t think the latter will change much in this case. The right way to measure is the amount of gas used to boiled a certain amount of water. Here, if I am reading you correctly, you merely lowered the amount of time and fuel by boiling less water. My guess, but you can check this, is that if you simply put the same amount of water in both pots you would used approximately the same amount of fuel and take the same amount of time, so zero change in efficiency, except if you count the weight savings of the pot itself.

I am also not too clear what exactly you want help with math wise. I guess %90 is stating the issue clearly. I'll give it a go if you can explain. In theory I am way over qualified for the job, but that doesn't guarantee anything. LOL

I'm not sure what you meant by 'distance' in the blog article, but is sounds like you are interested in determining the inverse efficiency, or weight carried per boil (for some standard boil like 2 cups (but you can easily convert this later into weight per oz of water, or whatever units you like, including weight per unit of distance using *your* stats on typical distance traveled per boils), in a way that includes the weight of the canister. Others have done this before, of course, but the weight carried per boil would be

R = Wg + (Wc/n)

where Wg is the weight of gas used to do one "standard" boil, Wc is the canister weight, an n is the number of boil you need before resupply, assuming your canister doesn't run out. If you are a true UL purist you would replace Wc with the combined weight of the canister + stove + pot + other paraphernalia like windscreens ans the like for each system (the weight of the whole stove system, and what you will get when comparing a specific alcohol stove with the jetboil will be R curves as a function of the number of boils that will cross at a certain number of boils, and for more than that number of boils the jetboil will be more efficient (less weight carried on a trip requiring n or more boils).

The crossing point will be at

n = (Ws2- Ws1)/(Wg1 - Wg2)

where Ws1 and Ws2 are the weights of the stoves systems for system 1 and 2, and Wg1 and Wg2 and the weight of the gas used for a boil for the two systems. This assumes Ws2 > Ws1, and Wg1 > Wg2 (as would be the case for an alcohol stove as stove 1, and the jetboil for stove 2).

Since it sounds like you have carefully measured Wg for your stoves, and of course you know the Ws, you can use that formula to tell you at exactly how many boils the heavier more efficiently stove wins out over the lighter less efficient one. So you have everything you need to calculate n for your esbit stove (stove 1) and your jetboil (cut down or otherwise).

Edited by millonas on 11/28/2013 06:12:17 MST.

Greg Mihalik
(greg23) - M

Locale: Colorado
Re: JetBoil Sol Ti (titanium) Cup Resizing Modification on 11/28/2013 08:00:07 MST Print View

John - on your blog you said -
"I cannot lie when I share that in the back of my mind is a serious amount of concern and worry about whether whacking off around 75% of the Sol Ti cup is going to cause a greater amount of heat build-up in what little bit of material there is, and whether or not that is going to cause issues with the welding points of the Fluxrings."

If you have water in the cup you will be OK.

BallonBoil

In This Video , two tablespoons of water in a generic latex balloon are boiled over candle flame.

If water can suck the heat through latex it can suck heat through titanium.

[As beat to death in other threads, Water Only - with anything else all bets are off.]


PM sent on Part Two - Weight Dis/Advantage

Edited by greg23 on 11/28/2013 08:33:03 MST.

John Abela
(JohnAbela) - MLife
Re: Re: JetBoil Sol Ti (titanium) Cup Resizing Modification on 11/28/2013 08:33:14 MST Print View

Hey All,

So I have had a bunch of people suggest to me that I *should* have done a test of the full size cup with 400ml of water in it BEFORE we cut it down in size.

To be totally honest, I agree, and I am sorry we did not do that. Ken and I got yapping and were enjoying a few hours of just hanging out playing around with all of this. It is my fault and I should have thought of doing that test, but I did not. My bad.

So this morning I performed a comparison of 400ml of water in a full-size cup and the 400ml-cut-down-size cup.

Results:

Both the full size cup and the cut-down-size cup averaged 1:20 seconds with 400ml of water.

Identical amount of fuel consumption

Therefore it would seem, right?, that cutting down the size of the cup does NOT result in any saved time nor fuel consumption.

I did up a low quality video too show this test for anybody that is interested in seeing the results. http://www.youtube.com/watch?v=pKv65qW3u9I

Again, sorry for not doing this before we started whacking away on the cup... but, at least now we know the results.

None of this has meant to be scientific by ANY means. I just really really wanted to know how much a Jetboil would weigh if it were not so dang tall and more the size of water volume of what I use when out on the trail. It really was just meant as a "hmm, I wonder??" kind of thing.

Edited by JohnAbela on 11/28/2013 08:33:53 MST.

Greg Mihalik
(greg23) - M

Locale: Colorado
Re: Re: Re: JetBoil Sol Ti (titanium) Cup Resizing Modification on 11/28/2013 08:44:47 MST Print View

Ahhh, the wonders of variability....



From your blog -

"This second resizing ... to 400ml ... resulted in ... a boil test ... duration [of] 59.98 seconds"

From the post above -
"Both the full size cup and the cut-down-size cup averaged 1:20 seconds with 400ml of water."

...and...

"None of this has meant to be scientific by ANY means. " You got that right!

A 33% difference between two "identical" tests opens up a lot of doors ...

Edited by greg23 on 11/28/2013 08:52:12 MST.

John Abela
(JohnAbela) - MLife
Re: Re: Re: Re: JetBoil Sol Ti (titanium) Cup Resizing Modification on 11/28/2013 08:54:19 MST Print View

A 33% difference between two "identical" tests opens up a lot of doors...


Isn't the whole aspect of the temperature of water such an amazing variable to totally screw with results LOL. The water used when we were doing the modification had been sitting in my backpack for probably 4 hours. The water I used this morning had been sitting out in my house, which was around 56(f) [my house, not the water] for all night.


It is for this reason that I have always thought "speed tests" of cook systems was/is the *stupidest* thing ever. Its not like we carry a thermometer with us when we go hiking (and if you do, you seriously need help).

People need to focus more on fuel consumption and less on whether their water is hot in two minutes or four minutes. (with the exception of speed hiking/adventure racing, in which case it very much does matter - but not a lot of us here at BPL into that)

But anyway, I actually care very little about most of this technical stuff... I just wanted to take a 90 dollar jetboil cup and whack it down to be the size of cup that I normally use, and see how it weigh against the eby265 system that was posted about here back in January 2013 by Jason Quick that I have slightly modified for my own preferences.

Greg Mihalik
(greg23) - M

Locale: Colorado
Re: JetBoil Sol Ti (titanium) Cup Resizing Modification on 11/28/2013 09:29:10 MST Print View

Part 2: From your blog -
"That makes the cut down sized Jetboil 106 grams / 3.74 ounces heavier than the eby265 system that I have pieced together. What weak math logic my brain has, seems to indicate that a stove that is 3.7 ounces heavier, yet has an initial 10 ounces of less fuel, it would be a good choice for those hikes where you cannot resupply for 18-20 days. Right??"

Here is the weight-by-day -

EsbitJB5

So for the first 9 days the JB system is an advantage. After that the Esbit system wins.
And over the 20 days you would carry 570 grams more with the JB than the Esbit.

Another advantage of the Esbit system is that you burn Only 6 4 gram tablets per day, whether or not your water boils. With the JetBoil system, you can easily burn more than your allotted fuel, through inattention, or waiting for "the boil".

(Yes, I realize Day 1 and Day 20 would probably have only one burn.)


[Edit: fixed a couple of inconsistencies]

Edited by greg23 on 11/28/2013 13:45:11 MST.

Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
Re: Re: Re: Re: JetBoil Sol Ti (titanium) Cup Resizing Modification on 11/28/2013 12:55:33 MST Print View

"This second resizing ... to 400ml ... resulted in ... a boil test ... duration [of] 59.98 seconds"

I seriously doubt the accuracy of your measured time.

--B.G.--

John Abela
(JohnAbela) - MLife
Re: Re: Re: Re: Re: JetBoil Sol Ti (titanium) Cup Resizing Modification on 11/28/2013 12:58:25 MST Print View


I seriously doubt the accuracy of your measured time.


Thankfully, I don't care what you doubt or trust.

Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
Re: Re: Re: Re: Re: Re: JetBoil Sol Ti (titanium) Cup Resizing Modification on 11/28/2013 13:04:01 MST Print View

"Thankfully, I don't care what you doubt or trust."

John, that is not a very positive way to get assistance with the math, as you posted initially. Here we are studying over your numbers to get to the bottom of the matter, and now you say that you don't care. OK.

--B.G.--

John Abela
(JohnAbela) - MLife
Re: Re: Re: Re: Re: Re: Re: JetBoil Sol Ti (titanium) Cup Resizing Modification on 11/28/2013 13:08:19 MST Print View

John, that is not a very positive way to get assistance with the math, as you posted initially. Here we are studying over your numbers to get to the bottom of the matter, and now you say that you don't care. OK. --B.G.--


Perhaps if I found even 1% of your posts to be positive and helpful, and not just sarcastic and argumentative posts, I might actually seek assistance from you... but we here all know you are not capable of that.

Thankfully others here are not that way.

Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
Re: Re: Re: Re: Re: Re: Re: Re: JetBoil Sol Ti (titanium) Cup Resizing Modification on 11/28/2013 13:13:38 MST Print View

"Perhaps if I found even 1% of your posts to be positive and helpful, and not just sarcastic and argumentative posts, I might actually seek assistance from you... but we here all know you are not capable of that."

John, you might find more posts to be positive if you understood the math better, as you initially posted.

My post here was neither sarcastic nor argumentative. I was pointing out the fact that it is extremely difficult to get a time measurement as finely cut as this.

--B.G.--

John Abela
(JohnAbela) - MLife
Re: Re: Re: Re: Re: Re: Re: Re: Re: JetBoil Sol Ti (titanium) Cup Resizing Modification on 11/28/2013 13:31:32 MST Print View

So we are suppose to get:

I was pointing out the fact that it is extremely difficult to get a time measurement as finely cut as this.


from:

I seriously doubt the accuracy of your measured time


Ok BG... if you say so.


Have a good Thanksgiving. Let us allow this thread to get back on-topic.

John Abela
(JohnAbela) - MLife
Re: JetBoil Sol Ti (titanium) Cup Resizing Modification on 12/09/2013 18:40:32 MST Print View

Hey All,

Jon from FlatCatGear asked me if I would perform some tests on turning the stove down reaaaaaly low and having much longer boil times to see if it resulted in less fuel consumption.

I have been testing this over the last 10 or so days and it seems to not have any negligible difference.

I have continued to get in the 2.5 through 2.8 grams of fuel consumption.

However, there reached a point I turned it down so low that it resulted in a boil time of 6 minutes, 18 seconds - and it consumed 3.1 grams of fuel.

Just thought I would share for anybody interested.

Ian Van Halen
(IDBLOOM) - MLife

Locale: PNW
Re: Re: JetBoil Sol Ti (titanium) Cup Resizing Modification on 12/09/2013 19:32:50 MST Print View

I've seen the same thing pairing up the Soto ODR1 with the Olicamp XTS pot. There's a sweet spot for fuel economy. Too low and I end up burning more fuel to reach a boil.

John Abela
(JohnAbela) - MLife
Re: Re: Re: JetBoil Sol Ti (titanium) Cup Resizing Modification on 12/09/2013 19:34:05 MST Print View

ps: I forgot to thank Greg Mihalik for the chart -- thank you sir!!

Marko Botsaris
(millonas) - F - MLife

Locale: Santa Cruz Mountains, CA
Re: Re: Re: Re: JetBoil Sol Ti (titanium) Cup Resizing Modification on 12/10/2013 20:38:33 MST Print View

Greg's post made me realize that I was basing my calculation on the starting weight, but that lots of people care about the average weight over the whole trip, so that is a different calculation - too hard core for me. My main concern to to brag to the people I'm with how light my bag is on the first day when they are really hurting. LOL