An in-depth look at that other model airplane building material!
By Frank Fanelli PHOTOGRAPHY: FRANK FANELLI C
ardboard.... high tech? Well, yes. That plain old stuff we take for granted is highly engineered for its intended use. And while model air- planes that fly wasn’t on the priority list of those intended uses, Chuck Felton has proven through the years that it just might be one of those undiscovered materials that satisfy a number of modeling requirements: cheap, light, strong. Granted, this material is better suited for large planes. You won’t find a freeflight Peanut constructed of even the lightest cardboard. Granted also is the fact that it may not be easy to come by pieces suitably sized for a 60-inch span plane. It was time to find out some more about corrugated card- board, the material Chuck calls for in his model designs.
Fortunately, the Sutherland Packaging Company is only ten minutes from the FM
offices. Joe Sutherland, one of the four- brother team involved in this family busi- ness, graciously agreed to play host to ques- tions and a tour of the plant. For an hour, he was mercilessly grilled and here are some of the more pertinent facts.
First of all, he corrected the terminology. What we commonly call cardboard is actual- ly a stiff single solid sheet of paper fiber. What Chuck uses and what we see in boxes is really corrugated fiberboard or board, or corrugated paper, as it’s also called. It is thoroughly strong enough for model flying if used properly.
Just to offer some statistics about its strength, Joe mentioned two tests that de- termine the material’s strength. First there’s the burst test. This measures how many pounds per square inch the board will carry. Commonly it’s about 200–275 pounds/square inch. The other test is the
ECT or edge crush test. It measures how many pounds pressure per inch of width the corrugated board withstands.
Like balsa, it does have a grain. As Joe ex- plained, his company takes pre-sized corru- gated cardboard from the plant in Hazleton, PA where it is manufactured from rolls of paper that come from a mill. The boards (in varying thicknesses) are commonly referred to as kraft paper in its unbleached and un- coated forms.
The mill, where the paper is made, sprays a slurry of fiber onto a belt and the move- ment of the belt pulls the fibers into the same front to back alignment. As the slurry of fibers moves through the machine the moisture is pulled out the fibers and results in a solid paper sheet used for the flutes. The same is true of the liner on either side of the flute.
So, like wood, the grain of the corrugated
Joe Sutherland, of Sutherland Packaging Company, holds a 4 x 8 sheet of “kemi” corrugated board (top of page). He considers this type of corrugated board—what we commonly but incorrectly call cardboard—the best for model planes because it has a smooth white surface that doesn’t allow bleed through
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when painting. This J&L Specilaty Folder Gluer (above left) has five glue heads that each can lay down 3-6 beads of hot or cold glue on the boards, and can fold them. Workhorse of the plant is the Flexo Folder Gluer (above right). It prints, scores, slots, glues and folds, and then feeds into an automatic bundler.
JULY 2013
Corrugated Guide to
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