Milled the 26' Douglas Fir 8 X 12 beam today

[Brmorgan]

Last night I did some figuring on the weight of the log I skidded home that I cut this beam out of. It was between 18-20" diameter at the butt and about 16" at the top, so I figured the log volume based on 18" diameter and 26' length as a rough estimate. This gave me just a hair over 3.6 cubic meters of wood. Air-dried Douglas Fir density seems to be in the 520 KG per cubic meter neighborhood, which gives me 1872 KG. Multiply by 2.2 and I get 4113 LBS, or a little over TWO TONS! This log wasn't particularly dry, either!

I have also heard that box heart is hard to dry, I guess I'll get some experience with that soon. Per the grading rules, I thought only splits were allowed inside the cant, and not to the ends? Do you know if that is so? I'm no grader, but trying to learn. I need to cut some #2 or better for the rafters.

I'd like to be able to scan the applicable section of the NLGA rule book but it's got copyright all over it. Or do you already have a copy?

At any rate my rule book has the following for No. 2 structural joists:

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Knots - Too complicated to list everything but the sizes are between 50-55% of the width of the widest face of the piece, the size changes proportionately the closer they are to the centerline of the wide face, or the ends of the piece, because such knots are less structurally damaging than ones near/at the edges or in the middle of the span where the most stress will be on the piece.

Unsound knots - limited to half of allowable knot size

Checks - not limited

Honeycomb/peck - firm; spots or streaks to 1/6th width of the piece

Pitch streaks - not limited

Pockets (pitch or bark) - not limited

Slope of grain - 1 in 6 (actually quite steep, I thought)

Skips - Heavy; 1/8" deep up to 2' length or up to 1/16" deep full-length

Stain - not limited

Torn grain - not limited

Unsound wood - small scattered spots, limited to 1/6th width of the piece

Wane - 1/3rd of any face or average equivalent; or 1/2 of any face for 1/4 length of the piece.

Whitespeck - Firm; limited to 1/3rd volume of the piece.

Shake - 1/2 length of the piece by 1/2 width of the piece (meaning from the edge to the pith on a box-heart-center piece); if through at the end of the piece, considered as a Split (below)

Splits - Medium or equivalent end checks.

Medium is defined as "Equal in length to twice the width of the piece and in no case exceeds 1/6th the length". This means that on an 8" X 8" beam, the maximum split length would be 16". However if the piece was less than 96" long (6 X 16 = 96) the split must be proportionately shorter. A 72" piece would be 3/4 the length, so the maximum split length would be 12" in that case.

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So, clear as mud? LOL. Going by these numbers, No. 2 is essentially the "Stud" grade of timbers and beams. Stud grade itself where lumber is concerned is really a combination of No. 3 / Utility structural defect rules and No. 2 / Standard edgewane/skip rules (to guarantee a good nailing edge).



I just got back to work grading lumber at the mill yesterday after being laid off a year ago at the end of February. It's good to be back at it, and the pace is a little more laid back with a better log quality than before, so it's easier for the most part. I'm pretty sure the lumber inspector will be in sometime next week to make sure I didn't forget everything in the last year, so if I manage to talk to him I'll try to remember to ask about the twist thing. He's conveniently the same fellow that was my instructor all three times I've gone to get/renew my grading ticket. Super nice guy. One time he wanted me to come help him go through a couple of my slings of lumber because "it'll go faster with two people, and if we go faster I might not be as picky!". LOL. I've never failed a check yet though in 7 years.

 

[BobL]

Last night I did some figuring on the weight of the log I skidded home that I cut this beam out of. It was between 18-20" diameter at the butt and about 16" at the top, so I figured the log volume based on 18" diameter and 26' length as a rough estimate. This gave me just a hair over 3.6 cubic meters of wood. Air-dried Douglas Fir density seems to be in the 520 KG per cubic meter neighborhood, which gives me 1872 KG. Multiply by 2.2 and I get 4113 LBS, or a little over TWO TONS! This log wasn't particularly dry, either!.

I can't see how you got 3.6 cubem

18" diam = .454 m or radius = 0.227 m
26' length = 7.88 m

Cross sectional area = PI x 0.227^2 = 0.162 m^2
x length = 1.27 m^3

= 1.27 x 520 = 664 kg

 

[Ted J]

I can't see how you got 3.6 cubem

18" diam = .454 m or radius = 0.227 m
26' length = 7.88 m

Cross sectional area = PI x 0.227^2 = 0.162 m^2
x length = 1.27 m^3

= 1.27 x 520 = 664 kg

MAN..... Don't make this complicated... I only gots 10 fingers and ten toes. :biggrinbounce2: ...and that metric stuff doesn't help either :bang:


This is easier:

Species: Douglas-fir, Interior north
Small End Diameter: 16.00
Large End Diameter: 20.00
Length: 26.00'
Quantity: 1.00
Estimated Weight: 2290


Species: Douglas-fir, Interior north
Small End Diameter: 18.00
Large End Diameter: 18.00
Length: 26.00'
Quantity: 1.00
Estimated Weight: 2265


I usually look at the Sherrill log weight chart (PDF FILE) but Douglas Fir isn't listed????

Later,
Ted

PS: I understand this is for green cut weights, so it could possibly be the max weight. I calcualted it two ways also as shown

 

[losttheplot]

Slope of grain - 1 in 6 (actually quite steep, I thought)



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I manage to talk to him I'll try to remember to ask about the twist thing. .

I am only assuming, and we all know what that does, but wouldn't twist be covered by slope of grain ?

 

[BobL]

MAN..... Don't make this complicated... I only gots 10 fingers and ten toes. :biggrinbounce2: ...and that metric stuff doesn't help either :bang:

That's funny because that the easiest way for me but I can think in Imperial or Metric so I'll do it again and leave the metric out completely:

Diameter of tree = 18"
Radius of tree = 9"
Radius of tree in ft = 9/12 = 3/4 ft
Length = 26 ft

Volume = PI x (3/4)^2 x 26 = 46 cubic feet

Density of Green DF = 35 lb/cubic feet
Weight =Density x Volume = 35 x 46 = 1610 lbs

Density of Dry Df = 30 lb/cubic feet
Weight =Density x Volume = 30 x 46 = 1380 lbs
(This is slightly less but similar to my previous answer in kg)

Either way they are a some way from being a ton, more like about 3/5 ton.

 

[mtngun]

That other Forest & Tree forum that we are not allowed to link to has a log weight calculator. It claims an 18" x 26' doug fir weighs 1746 pounds green.

Then I tried the calculator at Woodweb, it says 2290 pounds ! ! ! Presumably green.

Let's see if AS will let me link to Woodweb. log weight calculator

 

[olyman]

That other Forest & Tree forum that we are not allowed to link to has a log weight calculator. It claims an 18" x 26' doug fir weighs 1746 pounds green.

Then I tried the calculator at Woodweb, it says 2290 pounds ! ! ! Presumably green.

Let's see if AS will let me link to Woodweb. log weight calculator

ive posted the woodweb calc wherever i could--its very close to accurate,as ive weighed a few at the elevator scale--

 

[TraditionalTool]

Multiply by 2.2 and I get 4113 LBS, or a little over TWO TONS! This log wasn't particularly dry, either!

That sounds right...most of my logs that are 32 feet long are in the same range as they have the sides milled off of them.

I'd like to be able to scan the applicable section of the NLGA rule book but it's got copyright all over it. Or do you already have a copy?

No, I don't have a copy, wish I did. This info is very helpful.

Slope of grain - 1 in 6 (actually quite steep, I thought)

I agree, that's about 16 percent, but still when your cutting quarter sawn they also allow quite a variance in the angle of what is considered vertical (i.e., quarter sawn).

Wane - 1/3rd of any face or average equivalent; or 1/2 of any face for 1/4 length of the piece.

Geez, I can't believe that. We had 3 logs flagged for too much wane, and they were just along the edge by the milled face...no where near 1/3rd, that's for certain.

So, clear as mud? LOL. Going by these numbers, No. 2 is essentially the "Stud" grade of timbers and beams. Stud grade itself where lumber is concerned is really a combination of No. 3 / Utility structural defect rules and No. 2 / Standard edgewane/skip rules (to guarantee a good nailing edge).

This is a lot clearer than the ext that I have, which is just the Norwood supplied sawmill book and the lumber calculator from Cooks.

I just got back to work grading lumber at the mill yesterday after being laid off a year ago at the end of February.

WooHoo! Congrats Brad, I've been out of work for over a year myself, although I worked a short job a few weeks ago...I'm looking forward to getting back to work myself...Let's all have a toast for Brad, getting work is not so easy to come by these days!

I am only assuming, and we all know what that does, but wouldn't twist be covered by slope of grain ?

No, I don't believe so. The angle of the grain will basically determine how it is sawn, but twisted grain will spiral and cause the wood to twist if it straightens out. Most likely grain that is slopped would only cause the wood to bow or cup, depending on which way it is running.

 

[Brmorgan]

OK so I figured out that I accidentally plugged the diameter into the volume calculator instead of the radius, which explains why my log weight numbers were so high. I thought they seemed a bit steep to be honest, especially since I can lift one end of the cut beam off the ground at a time, though barely. Still, I come up with well over 500 lbs for the weight of the beam either way, so maybe I'm in better shape than I thought...

Alan, "slope of grain" doesn't refer to the angle of the growth rings re: being quarter/flat/rift sawn. It basically refers to grain runout from either the piece being cut off-axis from the log, or from spiral grain that is growing off-axis. Here's a page from my grading training materials PDF that I uploaded here a while ago:

There's nothing in those materials about copyright and nobody's complained yet, so I think they're OK to post. In resinous trees like the Spruces, Pines, and Douglas Fir (but not the True Firs e.g. Amabilis, Grand, Noble, Subalpine etc.) you can usually see "resin ducts" (like pores in hardwoods, but smaller) that will always follow the grain and let one measure the slope angle. There's also a saying, "Stain follows the grain, rot does not" - meaning that things like the blue stain fungus in beetle killed Pines will follow the direction of the grain as well, because it is spread through the water-carrying channels in the sapwood of the tree and feeds off the moisture and sugars in the sap. Rot, on the other hand, feeds off of the wood cellulose itself and will spread across the grain at random. Lastly, seasoning checks (but NOT necessarily splits) will usually follow the grain direction as well.

In the case of the 6X6 I cut:

The shake visible on the top extends approximately half the length of the piece, in this case about 5'. In that length, it covers about 4.5 inches of the width of the piece (guessing from the photo here). So that would be 60"L / 4.5"W = 13.33333, so the slope of grain is about 1 in 13; well under the 1 in 8 allowable in a No. 2 structural beam according to my rule book.

A higher slope of grain ratio equals a lot less load bearing capacity because the grain will want to shear across the piece. In Stud grade lumber, the allowable slope of grain is 1 in 4 - meaning that in a 2X4, the grain can go completely across the piece within only 14" of length. This is because Studs are graded to hold a vertical compressive load, so there isn't such a worry about shear stress on the board.

I think I have a couple short Pine 2X4 blocks with a steep slope of grain and stain to show it; if I do I'll take a couple pictures and try to get a shot of resin ducts too.

 

[TraditionalTool]

Alan, "slope of grain" doesn't refer to the angle of the growth rings re: being quarter/flat/rift sawn.

What I was trying to describe is where a log does have slope, opposed to twist. Just using the variance for ring growth as an example of how much they allow for quarter sawing, so it doesn't surprise me that they allow so much slope.

It basically refers to grain runout from either the piece being cut off-axis from the log, or from spiral grain that is growing off-axis. Here's a page from my grading training materials PDF that I uploaded here a while ago:

I remember you uploading that now, I have it squirreled away on the computer.

well under the 1 in 8 allowable in a No. 2 structural beam according to my rule book.

That is quite surprising also. It doesn't look as if it weakens the cant though.

A higher slope of grain ratio equals a lot less load bearing capacity because the grain will want to shear across the piece.

That does make sense also.

Do you know how graders charge for grading material? The last guy that did the grading on the logs in West Virginia was a real PITA, but I guess he had his reasons why the 3 logs needed to be replaced.

The better I understand the grading rules, the better chance I will stand of dealing with the next grader. I'm gonna have to get the rafters graded as well...

 

[BobL]

I played around with the Woodweb log weight calculator and could not believe that my calculation of the weight of Brads log could be that far out from that obtained by the wood web log calculator .

I got between 1380 and 1610 lbs, while Woodweb shows 2290 lbs.

So I did a bit of digging around and found I was using a green douglas fir density that was too low (35 lbs/cuft) while Wood web uses a wood density that is on average slightly too high (46 lbs/cuft). Woodwed probably uses such a high value because they would prefer users to over estimate the weight of logs so they do not get into problems.

I also found this very interesting article by the USDA (http://www.fs.fed.us/pnw/pubs/pnw_rp347.pdf) on the density of Douglas fir and this interesting graph is presented.

What this shows is the density of DF varies with the height up the tree. At the base the Density is close to 50 lbs/cuft while half way up the tree it's around 37 lbs/cuft. The average density for DF is ~42 lbs/cuft.

It turns out that this variation in density is closely associated to the MC variability in trees. This means the MC content in lumber from any one tree will vary considerable and this has an impact on lumber drying.

So back to Brads log. Using an average density of 42 lbs/cuft, the most likely value is 1932 lbs so not quite a ton.

 

[TraditionalTool]

It turns out that this variation in density is closely associated to the MC variability in trees. This means the MC content in lumber from any one tree will vary considerable and this has an impact on lumber drying.

This is key to know when calculating the weight of a log. On another forum, one of the members questioned a 9000 lb. weight I posted, saying the log would only weigh 7700 lbs. where they live. It's all relative as you can never calculate exactly how much moisture content a log has, unless one measures the MC.

So back to Brads log. Using an average density of 42 lbs/cuft, the most likely value is 1932 lbs so not quite a ton.

Well, I have a doug fir that I figure is over 3,000 lbs. and it's less than 17 feet. It's about 36" in diameter. I estimate it by how it feels when lifting it on my forklift, which can lift 6000 lbs.

FWIW, your 1932 lbs is not far from what Ted calculated up in the thread, at 2290 lbs.

 

[BobL]

Well, I have a doug fir that I figure is over 3,000 lbs. and it's less than 17 feet. It's about 36" in diameter. I estimate it by how it feels when lifting it on my forklift, which can lift 6000 lbs.

Assuming it's 17 ft long and green I calculate that log to be 5000 lbs, which means under these conditions 3000 or even 4000 lb is a serious underestimation. Woodweb calculates this to more than 6000 lbs
When it's at 12% MC I reckon it will 3600 lbs
To be 3000 lbs at 12 % MC a 36" diam DF will need to be less 13 ft 6"

FWIW, your 1932 lbs is not far from what Ted calculated up in the thread, at 2290 lbs.

Ted looks like he just used the woodweb calculator.

 

[Ted J]

Assuming it's 17 ft long and green I calculate that log to be 5000 lbs, which means under these conditions 3000 or even 4000 lb is a serious underestimation. Woodweb calculates this to more than 6000 lbs
When it's at 12% MC I reckon it will 3600 lbs
To be 3000 lbs at 12 % MC a 36" diam DF will need to be less 13 ft 6"

Ted looks like he just used the woodweb calculator.

You bet.... I just copied the woodweb info after I punched in the numbers. If you look at my previous post I link to the Woodweb log weight calculator above my "copied" estimations.

You guys are using moisture content, the Pythagorean theorems, circle sectors, Binomial Coefficients, and transcendental numbers such as Pi. (I myself like coconut cream but also many other types of Pi too!) :hmm3grin2orange:

The only question I would ask is if Brad gave us the dimensions with or without the bark.
Woodweb gives me this weight if I subtract 2" for bark.

Species: Douglas-fir, Interior north
Small End Diameter: 14.00
Large End Diameter: 18.00
Length: 26.00'
Quantity: 1.00
Estimated Weight: 1817

I'm sure Brad gave us dimensions excluding the bark, this is not the first time he's done this....

Ted

PS: This IMO would be a "worse case scenerio" as far as weight, as Woodweb states "Note: the assumed moisture content (MC) of the log(s) is 75%."

 

[BobL]

You bet.... I just copied the woodweb info after I punched in the numbers.

You guys are using moisture content, the Pythagorean theorems, circle sectors, Binomial Coefficients, and transcendental numbers such as Pi. (I myself like coconut cream but also many other types of Pi too!) :hmm3grin2orange:

I'm a fan of Pecan myself!

PS: This IMO would be a "worse case scenerio" as far as weight, as Woodweb states "Note: the assumed moisture content (MC) of the log(s) is 75%."

In that case then their assumption of a density of 46 lbs/cuft is even "more worse case" since average green density is 42 lbs/cuft and 75% MC would make it 39 lbs/cuft.

 

[TraditionalTool]

I'm a fan of Pecan myself!

:agree2:

Funny, Ted is in Texas, that is like the home of pecan pie, and he's eatin' coconut creame...

In that case then their assumption of a density of 46 lbs/cuft is even "more worse case" since average green density is 42 lbs/cuft and 75% MC would make it 39 lbs/cuft.

Too many numbers...it's a friggin' log, weighs more than 100 lbs. and less than 10,000 lbs...

 

[Ted J]

I'm a fan of Pecan myself!



In that case then their assumption of a density of 46 lbs/cuft is even "more worse case" since average green density is 42 lbs/cuft and 75% MC would make it 39 lbs/cuft.

OH... now your tryin' to use logic on me HUH...... ?:jawdrop:

OK, what if we use Moisture content at 100%. With the Specific gravity of Douglas Fir being .53 and at 100% would bring it to a density of 65 lbs/cuft(red arrow).

If you use the sameWood Handbook density chart it has the density at 57 lbs/cuft. for 76% MC. (blue arrow)

I guess most of everything is dependant on whose chart you want to look at. Woodwebs chart was the fastest and easiest for an answer at the time. According to the same chart 39 lbs/cuft would be a MC of 20% (green arrow).

Ted

 

[Ted J]

:agree2:

Funny, Ted is in Texas, that is like the home of pecan pie, and he's eatin' coconut creame...

Too many numbers...it's a friggin' log, weighs more than 100 lbs. and less than 10,000 lbs...

That's 'cause they don't make pecan creame pie..... most people I know who make pecan pie seem to like alot of sugar or own a sugar plantation.

That's like brownies... How many people like brownies with fudge icing on top? Well, I don't like the icing on top of brownies at all. I've been called weird and other names...

 

[Ted J]

Oh.. it could be that the higher up the tree the less MC the tree has, as it was previously stated........ probably 'cause water weighs more and the wicking properties are less in a douglas fir than say.................. wait for it.......................... a cottonwood...! :blob4:



That's funny, I don't care who you are!!!


Ted

 

[BobL]

Oh.. it could be that the higher up the tree the less MC the tree has

In part yes - check this out - it's from the same article I quoted above.

Looking firstly at the top line of the lower striped area on the graph, at the base of the tree the water content of green DF reaches a maximum of 21 lbs/cuft, about 1/3 of the way up the trunk the max water content is 14 lbs/cuft and then it increases again and on average it is about 17 lbs/cuft

OH... now your tryin' to use logic on me HUH...... ?:jawdrop:
OK, what if we use Moisture content at 100%. With the Specific gravity of Douglas Fir being .53 and at 100% would bring it to a density of 65 lbs/cuft(red arrow).

Sorry it doesn't work like that. Green or standing DF never gets to be 100% MC or densities above 50 lbs/cuft.

From real measurements shown on the graph (bottom line of the solid grey area), the average overdry dry density of the wood is 28lb/cuft.
The average water content is 17lb/cuft, so the max MC is 17/(28+17) x 100% = 38 %MC

The 75% MC referred to in Wood web is not a 75% MC - but 75% of the maximum MC so 75% of 38% = 28.5% MC, even on your chart this show up as a density of 42 lb/cuft.

I think the original post from Brad was that his piece of wood weighed more than 4000 lbs and I think we have established that it's not quite that. Whether its 2300 lb or 1600 lb or somewhere in between I'd go with 2300 lb to be on the safe side.