Do you know where your wing spars come from?

I don’t know about you, but I don’t often think about where my food comes from. Sad, really, but truthful. I suppose I don’t really think about where most of the “stuff” I consume comes from —  including parts and pieces of aircraft.

For Ron Piercy, a fishing trip to southeastern Alaska five years ago turned into a supply of aircraft grade Spruce for the wing spars he sells at Rainbow Flying Service. Oh, and he can tell you exactly where the wood came from.

After the fishing trip, Ron’s friend bought some property in Alaska. A Sitka Spruce tree that stood behind his new cabin was cut down.

“It was a four-foot diameter tree at the base, and probably 40 feet up to where there were any limbs, which makes good wood for aircraft,” started Ron. “You can’t use the part where the limbs are. You gotta have the straight part up to where the limbs start.”

So Ron bought a five-foot chainsaw bar, chain, a portable mill, and flew back up to Alaska to help a contractor cut the tree into cants.

What’s a cant? “Cants are like railroad ties, more or less,” says Ron.

“We had two logs that were 18, maybe 19 feet long. We cut each one of those logs into four cants. Then, with his excavator, we loaded the cants onto a barge, and barged ’em over to Craig, Alaska, to a mill that could saw the cants into boards.”

The first time I spoke with Ron, those boards were in transit from Alaska to Seattle. The last time I spoke with Ron he had just returned to Moses Lake, Washington, after picking up the boards and trailering them back to Rainbow Flying.

Next up is “stickering and stacking the board so they can properly dry.”

Ron’s pretty excited about this new wood.

“I haven’t always been happy with the wood I’ve bought from my supplier,” continued Ron. “I don’t think they’re selective enough and they don’t grade it hard enough.”

Sometimes the trees twist, which creates a spiral grain, which means the grain runs off sideways in the board. “And that’s not good. So by actually going up and looking at this tree, I could tell the grain was great.”

Turns out only the outer part — 6-to-12 inches — of the tree is usable for aircraft spars. The middle of the tree is too coarse with spike knots.

“Then it has to be cut so the grain runs vertically across the board and not in the flat direction.”

Is this for strength? Not being sure, I asked Ron.

“Well, it doesn’t warp, for one. I don’t know whether it’s necessarily stronger one way or the other, but when you cut a board flat, a lot of times it’ll warp on you and you’ll get a cup-shaped piece of wood. And of course, it needs to be fine-grained. The grains on this wood are like a 16th of an inch apart, and the core of the tree will have grains that are about a quarter of an inch apart. I tried to count the grains on this tree, but it was hard to count because the grains are so close. The nearest I could figure, this tree was 300 years old.”

The primary use for this wood will be wing spars, but Ron will also use it for “window frames and stringers and stuff like that, but the primary aim is spars.”

“Spars require a piece of wood about 16 feet long. It’s fairly easy to find a good board that’s eight feet long, but getting a good board that’s 16 feet long is much harder.”

Ron hopes to make 200 spars from this wood. That’ll be enough to supply 25 aircraft, at four spars per plane.

While aluminum spars are available, Ron points out that “wood doesn’t fatigue like aluminum. You can stress a piece of wood a million times and it’s just as strong as it was to start with, as long as you don’t go beyond the point of causing damage.”

Ron’s Rainbow Flying Service has long been a supplier of wood wing spars for Aeronca, American Champion, Citabria, Decathlon, and Scout aircraft.

If you happen to need a set of spars for your plane, and care about where the wood came from, Ron can tell you.