Wood nerd question

[Blue Vomit]

I scrounge most of my wood. A lot of it is already cut into rounds by someone other than me. Some of it I can cut to my preferred length. When processing, i am always mindful of a long burn so I cut to around 22" for the Oslo when I can.
I just picked up a load of nice hickory already cut into about 15" rounds. This prompted a few questions in my head.

Comparing loading the stove with seasoned 15" hickory splits vs loading the stove with seasoned 22" cherry split, which will give me the longer, better burn?

Which is more important, volume of the splits (lengths), or species of the split (btu rating)? And where approximately will the btu rating outweigh the length of the comparable split?

I suspect there is some formula someone who loves numbers could use to calculate this. Ive seen some pretty nerdy things before on this forum... go to it boys!

Unfortunately I will be no help in this area. I spent the majority of my time in high school algerbra class dropping my pencil 50 times. Those of you who went to a co-ed catholic school will get that reference. ;-P

 

[bogydave]

If both are equally seasoned/dry wood.
The weight of the wood that goes into the stove will determine the BTU of the load.
(dry wood has about 7,000 BTUs per pound.)
1 pound of pine has the same BTU as 1 pound of hickory.
As for burn times, split size, how fast the wood off gasses, inside stove temp, draft, stove air settings & other variables come into play.
Smaller diameter splits mean more pieces in the stove, more surface area to off gas, & more air space:: will burn hotter & faster.

Do a test of each & see what yo come up with.
weigh the load
record the stove settings & weather conditions
try to use the same diameter splits.
Lots of things need to be the same, but you don't have a lab, so "wing it"
& try to stay close to the same conditions.

 

[Blue Vomit]

so you are saying with all other variables being relatively equal (outside temp, draft, MC, split diameter, etc) weight of the splits would be a good indicator of which piece will burn longer or better?

or if an overall weight of a load of 15" hickory outweighs a load of 22" cherry or poplar it will probably burn longer, better?

 

[kenny chaos]

Hey Man- People can, and do, get anal about everything. Remember, you're just burning firewood like your gandfatherx10 did in his cave.
Acuna matata-
kenny

 

[bogydave]

so you are saying with all other variables being relatively equal (outside temp, draft, MC, split diameter, etc) weight of the splits would be a good indicator of which piece will burn longer or better?

or if an overall weight of a load of 15" hickory outweighs a load of 22" cherry or poplar it will probably burn longer, better?

Yes, in the perfect word
more weight, more BTU in the heavier load, if the stove is putting out 40,000 BTU per hour, the heavier load will burn longer.
Better burn ?? is more like an "equal burn" , if the BTU output of the stove, per hour, is the same.
Multiply 7,000 X pounds of dry wood will give you the BTUs you loaded into the stove.
50 lbs X 7k = 350,000 btu of wood in the load ::: hickory
350,000 / 40k btu per hour = 8.75 hours

40 lbs X 7k =280,000 btu of wood in the load / cherry
280,000 / 40k = 7 hours

Now the perfect world with fire wood don't exist as each wood will burn a little different, & keep the stove putting out 40K btu per hour is very difficult.
But if the load of hickory out weighs the load of cherry, the hickory will burn longer, putting out the same BTUs per hour of heat.

I'm not the best at explaining it, others here have done a much better job.

If you buy wood & the price is the same for a cord of cherry or hickory. Buy hickory, you'll get more heat (5.8 million BTUs more) for the same money.

Cherry, Black lbs/cord: 3,145 BTU/ cord : 19.5 (million)

Hickory, Shagbark lbs/cord: 4,080 BTU/cord: 25.3 (million)
(ref: http://chimneysweeponline.com/howood.htm )

 

[kenny chaos]

so you are saying with all other variables being relatively equal (outside temp, draft, MC, split diameter, etc) weight of the splits would be a good indicator of which piece will burn longer or better?

or if an overall weight of a load of 15" hickory outweighs a load of 22" cherry or poplar it will probably burn longer, better?

Yes, in the perfect word
more weight, more BTU in the heavier load, if the stove is putting out 40,000 BTU per hour, the heavier load will burn longer.
Better burn ?? is more like an "equal burn" , if the BTU output of the stove, per hour, is the same.
Multiply 7,000 X pounds of dry wood will give you the BTUs you loaded into the stove.
50 lbs X 7k = 350,000 btu of wood in the load ::: hickory
350,000 / 40k btu per hour = 8.75 hours

40 lbs X 7k =280,000 btu of wood in the load / cherry
280,000 / 40k = 7 hours

Now the perfect world with fire wood don't exist as each wood will burn a little different, & keep the stove putting out 40K btu per hour is very difficult.
But if the load of hickory out weighs the load of cherry, the hickory will burn longer, putting out the same BTUs per hour of heat.

I'm not the best at explaining it, others here have done a much better job.

If you buy wood & the price is the same for a cord of cherry or hickory. Buy hickory, you'll get more heat (5.8 million BTUs more) for the same money.

Cherry, Black lbs/cord: 3,145 BTU/ cord : 19.5 (million)

Hickory, Shagbark lbs/cord: 4,080 BTU/cord: 25.3 (million)
(ref: http://chimneysweeponline.com/howood.htm )

I rest my case.
Kenny

 

[wishlist]

Two things I've learned from this post. Blue needs to give me that 15" hickory and since Dave has no sunlight , snow up to his a## and temps always below 0, he's got nothing better to do than weigh wood and check btu's. Lol....

Seriously, that was a good question blue and Dave explained it very well!

 

[Wood Duck]

It seems to me if you have 15 inch splits and a stove that will take 22 inch splits, you load the 15 inchers to one side leaving 7 inches of space for a north/south split or two. maybe 10% of my scrounged wood is the right length, even when I cut it myself, so I mix east/west and north/south on nearly every load. Works great.

If you find you are morally opposed to mixing east/west and north/south splits in the same load, then i figure the 22 inch cherry is better than the 15 inch hickory. (22-15)/15 = almost 50% more wood volume with the cherry load, while the BTU difference is (25 million BTU - 19.5 million BTU)/19.5 million BTU = about 25% more BTUs for hickory per cord. 50% more wood volume even at 25% less BTUs/volume is still more BTUs.

 

[iskiatomic]

Just burn it! Damnit!


KC

 

[cptoneleg]

15" to 16" is not a good length for the Oslo, I still have lots of it, I had some 20" to 22" Red Maple and Cherry, and it burned longer the the shorter Oak due to being able to get twice as much wood in stove. At least thats what I thought, I had cut lots of the 16" stuff before purchasing stove, now I cut 20" seems to be a good size.

 

[Blue Vomit]

Things I learned from this thread so far:

Heavier is better

Bigger is better

My grandfather burned wood in a cave

I should just burn it dammit.

Thanks guys for ALL the replies. Normally I am all about the "don't over think it" and "just burn it" philosophy. BUT if I can avoid getting up early to reload the stove, I'm all in!
Sleep is good.

 

[Dune]

Cut 1/3 of your 15" pieces in half. Fill the stove completely, burn.

 

[Kenster]

Cut 1/3 of your 15" pieces in half. Fill the stove completely, burn.

Bingo!

 

[cptoneleg]

Cut 1/3 of your 15" pieces in half. Fill the stove completely, burn.

Bingo!

There is your answer Blue - you can do that if you like I thought about it but no way i was going to that much trouble for a few more hours of burn time, my wood coming up for next season is all cut to the prefered length.

LOL

 

[gzecc]

Things I learned from this thread so far:

Heavier is better

Bigger is better

My grandfather burned wood in a cave

I should just burn it dammit.

Thanks guys for ALL the replies. Normally I am all about the "don't over think it" and "just burn it" philosophy. BUT if I can avoid getting up early to reload the stove, I'm all in!
Sleep is good.

I agree. Doing less work for better results is where I'm at. Thats why I look for cherry, hard maple, ash, black locust. I get the best burn for the least work. Oak has too long a return on investment. If its dropped in my lap (yard), I will take it, but I won't go get it.

 

[katwillny]

Things I learned from this thread so far:

Heavier is better

Bigger is better

My grandfather burned wood in a cave

I should just burn it dammit.

Thanks guys for ALL the replies. Normally I am all about the "don't over think it" and "just burn it" philosophy. BUT if I can avoid getting up early to reload the stove, I'm all in!
Sleep is good.

All I know is that my furnace has not ran for more than 1 hour combined since the cold weather started back in late October. Granted its been an unusually mild winter. So this is the place to ask those questions and they are all valid. 15 years of "teaching' has taught me that every question has a certain amount of validity to someone. Reminds me of the day my son discovered that the sky was "blue" and may daughter thought it was a dumb realization but to him, the sky looked blue. So asking questions is always a good thing. Now burn it darn it. lol.