slight OT: truck hauling capacity

[Norman D. Crow]

2" long? Whatcha making, plates?

[Doug Miller]

In fact, the specific gravity of walnut when green is *lower* than when kiln-dried to 12%MC [*] -- remember that it shrinks in volume as it dries -- and the OP is making his volume measurements on green wood. He'll be OK.

[*] 0.51 green, 0.55 KD12. And it's not just walnut. This is generally true of nearly all North American woods, that the green MC is about 90% that of the KD-12 MC.

[Patriarch]

[e-mail] (Doug Miller) wrote in news:T2sqe.4223$ [e-mail]:

OK, so what I thought I understood is all screwed up now. Why wouldn't wet (or more accurately, 'green' or 'fresh') wood weigh more than that with 12% MC at equilibrium?

The green wood I've moved is heavier. Drying turned objects relies on measuring weight loss until it stops. What am I missing here?

Patriarch

[Robert Bonomi]

Simple, really. The piece *shrinks* as the moisture content goes down.

Total weight goes down, *but* depending on rate of shrinkage, weight per _unit_of_volume_ does 'something different'.

[mac davis]

hmm... maybe wood table saw blades? *g*

thanks for catching that, it was supposed to be 2'

mac

Please remove splinters before emailing

[Tom Quackenbush]

Using the figures from:

20% MC walnut weighs 38 lbs /cu ft (same as your figure), green walnut weighs 57 lbs/ cu ft.

So the dry walnut has 81% the weight of green walnut, or looking at it the other way, green walnut weighs 50% more than the dry walnut.

R, Tom Q.

[Tom Quackenbush]

Doh! 38/57 = 67%, NOT 81%

[Timothy Drouillard]

his thinks probably goes....

if 20% MC weighs 38lbs /cu ft and green weighs 57lbs /cu ft,

then green weighs 57-38=19 lb more. ok so far?

ok, then 19 is 50% of 38.

so the 57lbs is 38lbs plus 50% of 38lbs (19lbs)

so 38lbs + 50% of 38lbs =38+19=57.

so in a sense, the green (57lbs) is 20% MC plus 50% of the 20% MC.

[Tom Quackenbush]

The way you described is how I arrived at the 50% figure. From the point of view of the smaller figure, so to speak.

Just as valid is looking at it using the larger figure as the point of reference, which gives 67%. Unfortunately, I first said 81% instead of 67%. I should 've caught that, it's a pretty obvious mistake.

NO EXCUSE, SIR!

R, Tom Q.

[Timothy Drouillard]

[Tom Quackenbush]

Not much, I don't think. Green wood certainly weighs more seasoned wood, and it's also less dense (AFAIK - there may be some exceptions, but I doubt it).

I don't doubt Doug's SG numbers at all, but there are several flavors of SG when dealing with wood. Some don't reflect the change of weight between green and dry wood, but only the change in volume.

E.g.,

lists the specific gravities for walnut as .51 / .56 (oven dry / green). The weight used to calculate those particular SGs is oven dry in _both_ cases.The volume used is oven dry volume & green volume, respectively. IOW, those different SGs reflect the change in volume but not the change in weight. I don't know how the SG figures that Doug quoted were derived, but I suspect that it was similar to this example.

"The Encyclopedia of Wood" has a few pages that discuss density measurements of wood. Also, online:

"Specific Gravity, Moisture Content, and Density Relationship for Wood"

"Wood handbook--Wood as an engineering material" chapter 3, but the other chapters are good, too.

Too much information?

R, Tom Q.

[Norman D. Crow]

I knew that! Just couldn't resist!

[Tom Quackenbush]

Jeez, I need to hire a proofreader.

Should have read:

Green wood certainly weighs more than seasoned wood, and it's also MORE dense (AFAIK - there may be some exceptions, but I doubt it).