Long 2X12's (20 Foot)

[Greg Cook]

I posted this in the Sawing & Milling section, but some of y'all may not read that one very often.
Tell me what you think...

I'm sawing poplar for my barn, and just starting on some 20 foot logs for long 2X12's . As I squared up the 3rd side, it occurred to me I might gain some strength by leaving the "live edge" on that 4th side.  I will have to notch the ends, leaving a 12" wide tail to sit across my beams, so that the tops are uniform for the floor of the loft. That would leave the rest of the joist 14" to 18" deep. 

My questions:
1. Will notching the ends to 2X12 dimensions void the strength I'm hoping to gain by leaving the added wood in the middle?

2. How will this affect the drying (air drying)? Will I have more pronounced bow from leaving this edge? Maybe less?  Which way would it tend to bow? Toward the bark edge or sawn edge?  (Toward the sawn edge would be ok, since that side would be crowned up.)

3. Would leaving the sapwood cause me problems, like insects, which would have been sawn away? I am peeling the bark off the logs before I start to saw them, so it won't cause problems.

4. Any other things you can think of?

   While leaving the edge would save a little time, I'm mostly looking at the added strength, if any.  This is such a long span, I want all I can get.  Your opinions are most appreciated.

Thanks,
Greg

[Don P]

Nothing beats continuous straight grain. If you can avoid a sharp "re-entrant corner" in the notch, the NDS says that a gradual tapered notch at the ends is almost as good as the full depth piece.

The tendancy will be to bow out towards the bark most times so that works for crowning the rafters most times. The sapwood is much more prone to powderpost beetles. A good soaking with borate would help with that.

A spike knot or a big knot down in the tension edge is still a grain interruption and worth little, I wouldn't use it as an excuse to put lower grade material in that increased width area but I think it would help.

[jfl]

Hi,

You can look at www.awc.org (american wood council).  They have nice powerpoint about notches.  At the end of a beam, a notch can be up to D/4 (depth of the beam). The thing is that the highest tension and compression is in the middle of the beam, so they don't allow notches (or anything) in the middle third.

However, another thing they point out is that even if you notch a fraction of the depth of the beam, you can end up with something weaker than  what is left of wood: in your case 2x12.  If the notch help creating a check in the wood you might end up with something not so good.  As Don mentions, gradually tappered end will reduce the chance of end checks.

jf

[beenthere]

Hi,

....................  At the end of a beam, a notch can be up to D/4 (depth of the beam). The thing is that the highest tension and compression is in the middle of the beam, so they don't allow notches (or anything) in the middle third..............

When you say "in the middle of the beam", I think you mean middle of the beam length, and not the beam depth.  Right?   The way it is stated, could be confusing (at least it was when I first read it.      which is easy to do to me. 

[Jim_Rogers]

when they say middle third they mean middle third in the total length of the beam.....

[jfl]

Beenthere,

I try to use reference in my post to support what I mean. That's why I added the link to the awc web site.  I'll try to be more precise:

http://www.awc.org/HelpOutreach/eCourses/MAT105/MAT105eCourseV09-2007.pdf
Please follow the link and check page 10.

An image is worth a 1000 word...

jf