Woodworker's Journal 2007-Winter, страница 79
Odd is Better than Even
Always use an odd number of boards. The eye is usually drawn to the center of a panel, and a center board looks better than seeing a glue joint here instead.
Create a Composition
Arrange interesting areas in a balanced, random pattern. Don't cluster knots or swirly grain at one end of the tabletop or in the middle. Consider disguising transitions from board to board by placing similar grain patterns together.
Arrange for Effect
Frame a top with straight-grained boards along both outside edges. Run-out grain at an edge carries the eye with it.
A board's edge will show grain direction
Color can be a Surprise
Check for color differences. Neighboring boards shouldn't be dramatically different in color. Wet boards with water, alcohol or mineral spirits to get an idea of their finished appearance. Think twice before using sapwood or other distinctly different features.
Make Planing Easier
Try to line up all the boards so the edge grain runs the same way. If you're successful, you'll avoid tearing out the wood when planing the top by hand.
Give it a Rest
This is important. Walk away from your best arrangement for a day or two, then come back later to have a fresh look. See if it's still pleasing to the eye.
Keep Joints Simple
For a tabletop, butt joints are fine. Biscuits, dowels or splines will help align a top, but they will not make a well-fitted joint much stronger.
Joint with a Purpose
Long joints should be sprung. This means that the edge will be planed or jointed in a slightly hollow manner. Two sprung boards will touch at their ends but have a minute gap in the middle. Since boards lose moisture from their ends faster than out their sides, unsprung joints can separate at the ends over time. Check for tight joints before you glue.
Know Your Limits
Don't try to glue up too much at once. Thick, unsightly glue lines result when there is too much open time. Consider gluing the top in halves. Be sure to apply glue completely to all edges about to be joined.
The Last Rule
Draw a zigzag line down the length of each joint, then plane the panel by hand. When all the lines are removed the joints should be flush. Holding a light at a low
angle will reveal any defects. _
End Grain Debate
Like so many other things in life, woodworking is not always cut and dried. One controversy that divides many woodworkers has to do with orienting the end grain patterns in a panel made up of several boards, such as in a tabletop.
All of us know that wood moves with changes in seasonal moisture.Along with the expansion and contraction of the wood often comes some warping, which usually shows as a slight cupping of a board. The challenge for woodworkers is planning for this tendency of the wood to cup so a panel will remain as flat as possible.
The adherents to the first school of thought might be called the "ripplers." These woodworkers alternate the end grain pattern of every board so half the boards have their bark side facing up and half have their pith side facing up. Typically, a board cups toward its bark side. In this panel configuration, as every board warps slightly, each one in the opposite direction from the one next to it, the panel looks like a series of ripples and the overall effect is minimal. Holding the panel with tabletop fasteners or breadboard ends will limit the distortion, but not eliminate it.
The "big wave"proponents orient all their boards with the end grain repeating in the same direction. As the boards cup in this panel, the whole piece will distort into a uniform bowl shape, which can be controlled with just a few fasteners. The panel then feels smooth even if it's not perfectly flat.
Both theories are right, but neither is foolproof. It's probably a sign that no matter how hard we try, we can't control everything.