The Bill of Materials in our plans often use the terminology “random-random”, meaning varying lengths and widths. Most large lumber suppliers, particularly those supplying wood commonly used in boat building, don’t buy material already milled such as the common 1″ x 6″ or 2″ x 4″ sold in lumberyards catering to home construction.
Their lumber comes unfinished; neither the edges nor outer surfaces are milled or planed. The material comes in lifts or groups of a common thickness; neither the length nor width is consistent. A lift containing four quarters material will be slightly more than 1″ (hence “four quarters”) in net thickness in the rough. Widths and lengths will vary; the lumber is rough cut at the sawmill to obtain the most stock from the felled tree without thought of what the finished size may be. Think about it; if a tree is sawn up to make a special sized lumber there will be a lot of material that is scrap. Guess who pays for it; you the customer. More valuable lumber could be very expensive if sawn to specific sizes with excessive waste. Using the entire tree with minimal waste holds the cost down and reflects to the consumer.
Many small yards will mill and stock lumber to standard sizes. Obviously someone must pay for the waste and the time spent in sawing to size, again that’s you the consumer. Some yards finish the stock to thickness, usually 3/4″ to 13/16″, for four quarters stock. Lengths and widths remain as they came from the mill. That’s the stuff for boatbuilding you want. You can rip it to size yourself getting as much from the stock as possible. Obviously, if you have a choice, select the longest and widest stock available without paying a premium. Most suppliers do charge extra for wide widths and long lengths.
Many boat parts are irregular in shape. Arc-shaped parts, such as deck beams, can often be nested one inside the other. A 5 1/2″ width may provide a single beam while two may be obtained from an 8″ width. A 6′ long beam can be made from a single length, but perhaps two can be obtained from a 9′ length. It is readily apparent the wider the width and lengths the more usable material you obtain for your buck.
Check the Bill of Materials for the boat being built. Find the widest width needed and roughly total all the strips or other pieces and change to square feet of a given thickness. Be generous; material lists seldom cover the interior structure and some waste (or don’t you ever goof?) is inevitable. Remember when using random-random stock it’ll be cheaper than sawn-to-size material, so in the long run you’ll be ahead cost wise.
That’s why we prefer to call out random-random stock, particularly for frames. When we were producing frame kits for our designs, in our shop the random widths were piled in roughly the same widths. Working from the templates, we would select the most appropriate width and length for the parts being produced. Outfall filtered down to parts for a smaller kit so the waste was minimal. The footage of lumber we used to make a frame kit would always be less than for the typical home boatbuilder; since we had the selection advantage and templates to work from.
With care however, any boatbuilder can save on lumber by thinking and taking advantage of random-random stock.