Direction of warping wood?

Although it probably doesn't apply to your project, if a number of boards
were to be edge glued or fastened,

Edge gluing, or solidly fastening the planks will not stop the tendency to
curl. The boards will still curl, but since they are glued, they will
crack.

Al


"Lynn Coffelt" wrote in message
et...

this is off topic but I figure there are enough telescope makers/
woodworkers
here ...

Gosh, up to now, there is one correct response, and one incorrect
response.
Take my word for this, it is based on the "school of hard knocks",
classroom
and field studies beginning in 1932:

To use your way of looking at the end grain, the center of the tree
must be UNDER the plank for the natural "curl" to go down at the edges.
Although it probably doesn't apply to your project, if a number of boards
were to be edge glued or fastened, every other board would face "up", and
the rest "down". Thus the average warping of the entire surface is near
zero. Like to type on here, but it's getting dark outside and clear skies
are calling.

Lynn (with new ok, third or fourth handed 10" dob)

Edge gluing, or solidly fastening the planks will not stop the tendency to
curl. The boards will still curl, but since they are glued, they will
crack.

Crack?, Oh, sure, but at least the glued up bed would not be in a giant "U"
before it cracked. Some of the really cool "show" truck beds are of fairly
narrow oak, fir or maple "tongue and groove", "end matched" flooring. Not
something to be left outside in the rain, of course, and pretty heavy, too,
with supporting joists, but really beautiful. Outside the scope of this
project, I fear.
Lynn (who once built a pickup truck bed of vertical grain fir flooring)
(don't like to brag, but it was awsome)

Edge gluing, or solidly fastening the planks will not stop the tendency to
curl. The boards will still curl, but since they are glued, they will
crack.

Crack?, Oh, sure, but at least the glued up bed would not be in a giant "U"
before it cracked. Some of the really cool "show" truck beds are of fairly
narrow oak, fir or maple "tongue and groove", "end matched" flooring. Not
something to be left outside in the rain, of course, and pretty heavy, too,
with supporting joists, but really beautiful. Outside the scope of this
project, I fear.
Lynn (who once built a pickup truck bed of vertical grain fir flooring)
(don't like to brag, but it was awsome)

If you want your planks to warp with the edges going down, to drain
better, you want the center of the tree ABOVE the planks. This site has
a nice diagram... http://www.electrophysics.on.ca/wwing.htm
Marty

If you want your planks to warp with the edges going down, to drain
better, you want the center of the tree ABOVE the planks. This site has
a nice diagram... http://www.electrophysics.on.ca/wwing.htm
Marty

Hi all...


thanks for all the info and pointers !

take care

Bll

Here is a good reference. It says wood will tend to cup more toward the
bark side, so you'd want the "center" to be up. In my experience with a
few decks though, wood cups toward the sunny side! It just plain makes
sense that no matter which side is up, the sun will bake it to death,
causing it to dry faster (and shrink more) than the underside. So while
strategic orientation might help, it won't completely eliminate cupping.

http://www.woodweb.com/knowledge_bas...in_Drying.html

Bryan

BllFs6 wrote:
Hi all....

this is off topic but I figure there are enough telescope makers/ woodworkers
here ...

.so I ask
....

I am rebuilding a trailer in which the only part left is the metal frame....

I am planning on redoing the bottom of the trailer with wood planks....pressure
treated 1 by 8's....

So, lets say Iam looking at the end of a plank where I can see the tree
rings...and say on this particular slice I can tell that where the center/core
of the tree was lies ABOVE the plank as it rest flat on the ground...


In that position....as the wood ages and dries out over the years....are the
sides going to curl UP or DOWN?

Iam asking because I want the edges to curl down over time...ie I definitely
prefer the plank to become convex rather than concave...

Or do I need to flip all the planks over so that where the center of the tree
was lies BELOW the planks rather than above?

Thanks for any input!

Bll