Hi
I was investigating materials for benchwork and was wondering if there was a preference in using select pine (1x4’s) over knotty pine for joists etc. Will there be any loss in strength etc. I’m doing L-girder construction…
Thanks
I don’t know a whole lot about construction, but do know that wherever there are knots in wood, they are the weak spots. That’s why it is best to use wood clear of knots.
Bob Boudreau
There is a preference, but in most circumstances of building MRR, if you can’t bust it with your hands at the knot’s focus of weakness, it is a structural non-issue for the loads it will experience. If you are using solid rock (granite, not pumice) for your scenery, loading all your cars with lead, and jumping up and down on your completed benchwork, you may have a problem. Otherwise, unlikely.
Knotty wood does present another, more common challenge. If the wood has not been dried either properly or completely, the knots also serve as focuses for the movement the wood will experience with changes in humidity. This CAN be a problem with a layout.
The best way to overcome these challenges is to use engineered wood, aka plywood. It is stable, and in L-girder construction will be plenty strong enough for your purposes. Of course, the downside is accurately cutting the plywood down to manageable sizes can be a challenge.
There’s no need to consider D select or C or better pine for your benchwork. Number 2 pine carried by quality lumber yards will be fine for this use. I am not talking about lumber from a Home D centers, these so called lumber stores sell a pine that would be turned away if tried to deliver to a lumber yard. They should be ashamed to sell wood under the grading crieria they use. The #2 is almost utility or #3 at best, and “premium” pine( thats what they call it) no such grade of pine- but allows them to compare with others select or clear I guess. Also beware of the plywood carried, Substandard, voids, delam and min of plys for grade. In one forum or group some one was complaining about 1/4" luan from such a store. Was warped coming off the lift. Don’t give it a stress test- you can snap a corner off with min effort, try that on the full dimension 1/4" underlayment grade from a lumber yard. If you check the price difference it is generally only a dollar or 2 for a far better product. So much for the Home Depo rant but I am sick of these outfits suckering people who don’t know there is a difference.
Now, if you go to your friendly local lumber yard, The #2 pine should be flat stacked and kept neat (make sure you leave it that way), Pick though an select the cleanest pieces. Many times a board looks almost clear w/ exception of a couple knots. Look for the small or tight knots and look for the tighter graining- you don’t what wild far spaced grain- much weaker and quaranteed to warp.
I don’t know if you are set on the style of benchwork construction or not, but there are many other alternatives. many of which have been discussed on this forum at great length. Foam construction over plywood base, quality 3/4" plywood ripped to 1x4 instead of pine, L girders replaced with commercially avail or hand crafted truss “I” beam for long continuos support w/o all the legs, are just some of the options.
Sorry for all the venting, Hope this helps or has answered your question.
Bob K.