Photo by Marissa Daeger on Unsplash Improve your odds of getting the best-quality wood by selecting large-dimension stock and ripping the boards to the needed dimensions.
I sometimes forget that skimping on wood quality, even when tackling simple carpentry projects, is a false economy, and what holds true for everyday work holds just as strongly for boatbuilding. I recently built sliding doors for a boat shed, and in order to reduce the hanging weight chose 2×3 framing rather than using 2×4s.
Although I know that 2×3 studs are generally cut from quite small trees, I let my pocketbook win over rational thought and picked through the pile at the lumberyard, choosing what at that moment were reasonably straight 2×3 studs 8′ long. As I began assembling the frames and attaching T-111 plywood in my heated shop, the partially dried 2×3s began twisting and warping. Long story short: I now have permanently warped doors.
I can live with slightly warped doors on a shed, but wood joinery in boat construction has much finer limits. Uncontrollable warping or twisting could spell a ruined boat. Selecting the best quality will save headaches later.
Harvesting Small Trees
In recent years, forest management practices in the United States have promoted the commercial harvesting of comparatively small softwood conifer trees. In the western states, this has been touted as a tool to remove overstocked stands that are wildfire hazards. In the East, small trees can be used for producing fuel in pelletizing plants or for chip production to feed paper mills or wood-composite plants.
The market for pulp, composites, or fuel pellets tends to be unstable, and prices are less than what could be realized at dimensional lumber mills. As a consequence, some small-diameter logs—in the 4″ to 10″ range—have been ending up at stud mills in recent years. The smallest of these logs yields only one 2×3 and some residue for fuel.
Wood near the center of a tree, which is known as juvenile wood, has properties that differ from wood produced after about 15 to 20 years of growth, which is considered mature wood. Most notably, juvenile wood is weaker and shrinks to a greater degree longitudinally—so a stud that contains only juvenile wood and has a centered pith will shrink even in length, and a stud with juvenile wood on one side and mature wood on the other will warp considerably. In the accompanying photo, the 2×3 stud at the upper right will be more prone to warping than the one to the upper left. However, the longitudinal shrinkage of the stud on the left can lead to wracking problems when used in combination with mature wood studs in frame-and-panel construction.
The Dilemma
Because a pile of dimensional lumber at a big-box store may have arrived as recently as yesterday, the moisture content can be as high as 19 percent on the surface and even wetter in the center. This means that warping, cupping, and twisting are possible with further drying.
Dimensional changes with drying after purchase will be greatest for 2×3s cut from the juvenile zone near the center of a tree. As the width of dimensional lumber increases, we know that trees of greater diameter must have been the source. Although a 10″ tree would yield one 2×8 board, that board would contain juvenile wood and central pith and should be avoided.
In order to get some 2×8s that contain only mature wood, the harvested tree size would likely have to be greater than about 16″ in diameter—and that would be for a flat-sawn board, as shown in the example below. A tree approaching 2′ in diameter would be needed to get quarter-sawn 2×8s that contain only mature wood.
Richard JagelsThe pieces labeled A and B were purchased as 2x3s, and both show significant amounts of juvenile wood, which is the least-stable type. Because of its dimension, the 2×6, labeled C, had to have come from a tree that was larger, and therefore more mature, at harvest than the trees cut for the 2x3s in A and B. Milling the 2×6 would yield two 2x3s that would both have higher-quality wood than that found in either A or B. In the 2×4 samples D and E, wane indicates that the wood came from the outside of the tree, so again juvenile wood is minimized. Sample F, a 2×8, shows that the best wood is often found in wide dimensional stock, which by necessity is cut from mature trees.
The cross-sections shown in the photo are, top to bottom: two 2×3s, one 2×6, two 2×4s, and one 2×8. Except for the top left 2×3, all were picked from lumber piles to maximize mature wood. The clipped corners on the 2×4s show wane—the absence of wood is due to the curvature of the log—demonstrating that these boards were taken from the very outside of the tree.
The Solution
To improve the odds of getting structural lumber from near the outside of a large-diameter log, you could choose large-dimension stock and then rip those boards to the needed dimensions. Carefully selected 2×6 boards could be ripped to get two 2×3s, just as 2×8s could be ripped for two 2×4s. In either case, these would be stronger and more dimensionally stable than boards of similar sizes milled from smaller trees; they usually have fewer knots, as well.
A standard carbide-tipped table-saw blade produces a kerf width of less than 3⁄16″. The nominal, dry dimensions of a 2×3 are 1.5″ × 2.5″, while a 2×6 is 1.5″ × 5.5″. Deducting for saw kerf still yields oversized 2×3s after ripping. The same is true for the yield of 2×4s from 2×8s or 2×6s from 2×12s.
What is the cost comparison? Dimensional lumber prices vary among tree species, grade, and drying method. For this comparison, I chose common studs available at one big-box store in Bangor, Maine, of spruce, pine, or fir. Studs 8′ long were priced at $2.14 for 2×3s, $2.58 for 2×4s, $4.63 for 2×6s, and $7.35 for 2×8s. Thus, purchasing two 2×3s rather than one 2×6 would save only 35 cents, while purchasing two 2×4s rather than one 2×8 would save $2.19.
Sawing one or two studs from a small tree is more costly and wasteful than producing several studs from a larger tree—hence the premium price for 2×3s and the tiny savings versus resawing a 2×6. The differential becomes larger when producing 2×4s from 2×8s, but the effort may still be worth the extra cost for the potential quality improvement—if the boards are carefully selected at the yard.
The 2×8 shown in the photo would produce two very strong and stable 2×4s. It would also be a prime candidate for producing 1 1⁄2″-wide quarter-sawn strips for planking a canoe or kayak, especially if it were cedar.
When selecting a decay-resistant wood, like one of the cedars, choosing larger-than-needed stock will improve the chances of finding boards that have the highest resistance to rot. Small-dimension stock is more likely to contain decay-prone sapwood.
So I hope you will benefit from the lesson I painfully learned: Purchase large-size stock and rip to the dimensions needed as a way of improving the quality of the finish-dimensioned stock. The price premium could offset later heartache.
Dr. Richard Jagels is an emeritus professor of forest biology at the University of Maine, Orono. Please send correspondence to Dr. Jagels by mail to the care of WoodenBoat, or via e-mail to Senior Editor Tom Jackson, tom@woodenboat.com.