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Shrinkage (how long to cut?)

Post in 'The Wood Shed' started by Slow1, Dec 23, 2008.

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  1. Slow1

    Slow1 Minister of Fire

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    When wood seasons it dries. When it dries it shrinks. So, my question is how much does it shrink and should I consider this when cutting logs? My stove can take up to 20" and I would like to aim to get pretty close to that.

    IF wood were to shrink say 10% and I cut at exactly 20" then I'd end up with 18" after they were all seasoned... so adding another 2" at cut time could make up for this (i.e. start at 22", shrink 10% and end up with 19.8" just right!).

    So how much is shrinkage? I found a wikipedia article that says it is 5-10%, but that really didn't say to what moisture content level or anything... From a practical standpoint is this anything you experienced folks even consider? Is this a complete don't care?

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  2. LLigetfa

    LLigetfa Minister of Fire

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    They shrink mostly on their diameter, not on their length.
  3. Pagey

    Pagey Minister of Fire

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    I would agree that you'll see the real change in diameter, not length. Better to cut them to size and then have them end up a tad short than to leave them too long on the hope they'll shrink just the right amount. You'll end up cutting them twice if you bet that every split will shrink to exactly the right length.

    Note: I base that on no scientific understanding of what actually happens at the cellular level with a piece of wood dries. So, your mileage may vary.
  4. LLigetfa

    LLigetfa Minister of Fire

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    I cut my wood 3 inches shorter (20") than the stove can take (23"). That gives them a bit of space for the flames to come out the ends and lick the sides of the stove. Also, I wouldn't want to get a split wedged in and break the firebrick. It also gives enough room for error.
  5. Bigg_Redd

    Bigg_Redd Minister of Fire

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    It won't shrink enough to matter.
  6. fossil

    fossil Accidental Moderator Staff Member

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    There's nothin' real precise about this. Yeah, it would be nice to completely stuff a stove full and know you got every last BTU in there...but when you're reloading onto a nice hot bed of coals, and the splits are beginning to burn even as you're trying to get them just where you want them, you gotta be sort of quick about it, and having some wiggle room with the length of the splits helps a bunch. Stove might take a 20" split once it's inside the door and squared to the back wall...but just how wide is the loading door opening? Once you get the back of the stove loaded, you don't have much opportunity to do the diagonal squeeze through the door. I wouldn't cut 'em longer than 18", myself...maybe even 16". Rick
  7. drdoct

    drdoct Feeling the Heat

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    Been there done that. It's a sick feeling when you have to resaw your truckload to trim 1" off. My stove takes an 18" log. The door when loading E/W only takes a 16.5" log. I actually think loading N/S is +1" than loading horizontally. I cut all my stuff about 18.5" and had to bring a smoker back out and put it on the steps (brick) because it wouldn't fit. If it hadn't been for all the other posts titled..."Oops I just broke my door window" I would have probably broken it trying to jam it in. I'm just getting used to this length so when I start cutting I cut 1 or 2 and then come in and see how they fit. Then they are my reference pieces. After cutting 10 minutes or so it comes back and the reference pieces go into the pile.
  8. Slow1

    Slow1 Minister of Fire

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    Good point on the loading door... I'll have to try a few lengths to see what I can fit through easily... i.e. load the stove full when cold and see just what is easy enough to do with imaginary flames licking around them. Update: I just measured the front of the door, it is 21" at widest point, 19.5" at the top, the actual firebox is even wider but a bit too hot for me to stick my tape measure in at the moment to get an accurate measure :)

    As to shrinkage - thanks for the info that I can pretty much ignore that for length. Given that it will be two years before I burn what I plan to cut this winter I sure would hate to make a mistake here and go kicking myself that far down the line... especially if it ends up being a lot of wood! All the stuff that I bought seems to be cut pretty short - 15" or even less.. some pieces are decent lengths (18.5") but not many. I just don't think I want to go leaving 30-35% of the width of the firebox empty when I load it up full for the night....
  9. Gooserider

    Gooserider Mod Emeritus

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    As stated, length doesn't change when seasoning - just like boards in furniture making, you don't need to allow much for dimension changes on the length, but you do for cross-grain.

    That said, I think the concensus on length for cutting is around stove length - 2". IOW, if you have a 20" firebox, cut to 18".

    Two good reasons for this - one has been mentioned, the ease of loading and having some slack for flames around the ends of the wood. The other is that chainsaws are NOT precision cutting tools, especially given that most of us buck by eye or use the bar as a measuring stick, so the actual lengths you end up with are typically "target +/- an inch" - if you cut to a shorter than stove length target, then you will have a lower number of splits that need to be trimmed later...

    Gooserider
  10. crazy_dan

    crazy_dan New Member

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    I cut my wood about 18" that is 2" shorter than it will take but they fit both ways that way and it allows me 2" more glass protection
  11. Backwoods Savage

    Backwoods Savage Minister of Fire

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    If it were me, I would not cut them longer than what the stove takes.

    Our old stove would take 21" and we have some of that in our wood pile as I used to cut mostly 16" but did cut some longer. Now with our new stove that causes some problems. Present stove states 16" length but I've gotten some 19" stuff in there. The longer stuff either has to be cut down or sold or given away. I've already gave 1/3 of a cord to a neighbor who can burn those longer logs.
  12. jebatty

    jebatty Minister of Fire

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    For those who really want to know:

    http://www.woodbin.com/ref/wood/shrinkage.htm
  13. Jeff S

    Jeff S Feeling the Heat

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    As many have all ready stated,shrinkage along the logs length is negligible.Having said that I often accidentally cut logs longer ,lucky for me my boiler firebox is taller than it is long so I simply set aside any long logs until I have enough to fill the firebox with the logs standing on end.
  14. LLigetfa

    LLigetfa Minister of Fire

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    I just burn the long ones on the diagonal.
  15. Jeff S

    Jeff S Feeling the Heat

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    I do this also,anything is better than having to re-cut.
  16. Malatesta

    Malatesta New Member

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    I think if you buck up all your logs at 18-20 you'll be just fine . Put a 18 or 20 inch bar on your saw and use that for close enough measuring. No Need to get super precise on an inch of wood. I thaught BTU'S were measured on the woods density and hardness not its length
  17. jebatty

    jebatty Minister of Fire

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    BTU's are measured by dry weight of wood. One pound of dry aspen or popple has just about the same BTU's as one pound of oak or hickory. The pines run a little higher because of the sap/resin in the wood.
  18. Slow1

    Slow1 Minister of Fire

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    Fair enough - I don't intend to cut to the .10"... I'm pretty anal, but not THAT bad (yet?) :)

    As to BTU measurement - the thing I'm going for here is that the wood I bough is all pretty much around 15" - that means many are actually shorter too. Thus I have found it hard to really "fill" the box. I think that when VC says "up to 20 inch logs" they accounted for space around them in the firebox as the actual firebox has more than 20" in width. Thus when I load in 15" logs there is a lot of space on both sides. Now, if I want to get a longer burn I need to put more wood in there but I can only stack it so high and deep (I am getting good at this by now). However, the sides are big open gaps of space right now, perhaps 25% of the rated space for wood (5" of the 20") is being left open - that is a lot of potential wood to burn I think. So if I get a 3hr burn now with a "full" box (15") it seems to stand to reason that if I simply had 20" logs I could get that up to 4hrs all other things being equal. See where I'm headed here? (note I'm using round number in burn time for easy math in this illustration my actual burn times vary quite a bit of course...)
  19. ansehnlich1

    ansehnlich1 Minister of Fire

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    If I have short wood that won't fill the firebox, and I want a long burn, sometimes I'll take some choice pieces to the chop saw so they fit N/S in the leftover space available in the stove.
  20. Malatesta

    Malatesta New Member

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    Sloow1 you can also lay the 15 inch logs in the stove front to back . Maybe you can pack more in this way ?
  21. Slow1

    Slow1 Minister of Fire

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    NS I have just under 10" Bummer.
  22. Gooserider

    Gooserider Mod Emeritus

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    What I will do sometimes with my Encore is to load stuff in from the top, and keep pushing it all to one side or the other as I do so, then fill the resulting gap at the end with chunks or small short splits stuck in vertically.

    There are a few tricky aspects to the length of wood you can get into an Encore - the firebox is tapered top to bottom, and has some extra "lumps" that intrude into it near the top... At the bottom next to the grate, it's 22-23" wide, but it gets narrower as you go up, until it's only about 20" near the top, and you have a couple of bumps in the side from the thermostat lever that reduce that a bit more. In addition, the width of the top load door is an inch or two less than the firebox.

    Thus you can sometimes get 21-22" wood into the stove as the very bottom layer, but the upper layers need to be shorter. Also while you can "tilt" a split that is longer than the door is wide into the box by sticking one end in first and swinging it down, this gets harder as the box fills up since there is less angle to play with (Note that I find it will sometimes be possible to get a split in by sticking one side in first that won't go if you start from the other side...) IOW, if you want to play with different lengths of splits, you can get a bit more wood in than you would otherwise, but it can be tricky, and you can end up with the problem of a partly ignited split that doesn't fit.... :gulp: OTOH, if you stick w/ 18" splits, those will go in reliably almost top to bottom, as long as they aren't to big around. You might want a slightly shorter length for the last one or two chunks if you are loading all the way to the top, which IMHO is more useful for getting a long burn time than trying to fill every inch at the lower levels.

    Gooserider
  23. Gooserider

    Gooserider Mod Emeritus

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    As a side not for those that don't have Encore's, and haven't looked at their firebox, it is worth mentioning that the Encore firebox is a different shape than what many stoves have... It pretty much requires that you load E/W as it is wide from side to side, and very narrow front to back... It is also tall vertically, though I've never heard of loading wood in standing on end. This can be arguably a part of why the VC's give longer burn times - the wood at the top of the firebox tends not to burn a lot initially, instead the fire tends to mostly burn down near the bottom and the logs feed down into it as the lower logs get consumed.

    Gooserider
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