Navy radar may pick up some unidentified low flying objects Oct. 13, but there will be no need to scramble our air defenses.

It’s only squash.

Yes, thanks to the ingenuity of a Coupeville woodworker, squash will be flying through the air Sunday as part of the town’s annual HarvestFest.

The squash will be launched by a trebuchet, a medieval military engine replicated by Gary Leake, a woodworker who sits on the Coupeville chamber’s board of directors.

“It was Sandy Poust’s idea,” Leake said. “So I volunteered to build it.” Poust is another chamber board member.

The squash hurling event will be a fund-raiser, with participants paying a modest fee to pull the firing pin. Ammo will be supplied from the culls on Dale and Liz Sherman’s squash farm where the trebuchet will launch its weapons.

The trebuchet was used by medieval armies to hurl objects over walls of castles they had under siege. Rocks weighing up to 300 pounds could be tossed over a wall.

Leake’s trebuchet is a smaller model, custom-built for squash hurling. He’s been practicing with rocks and melons. So far, honeydew is his favorite.

“They make an interesting splat,” he said.

In a test firing of rocks recently, the first effort aborted, as the rock failed to escape the sling.

“That was not good,” Leake said. “The rock stuck.”

On the second attempt, the trebuchet’s arm impressively whipped the five-pound rock high into the air and about 200 feet into the Shermans’ field.

The concept of the trebuchet is simple. A large weight (Leake uses 330 pounds of cement bricks duct-taped together) is dropped. The attached 12-foot wooden arm is pushed into action. It picks up a satchel containing the ammo and swoops it into the air, expelling the contents at just the right angle to send it downfield.

Leake said he has test-fired objects weighing nearly 20 pounds, but for Harvest Fest the squash will weigh an average of five pounds. He finds that weight to provide the best trajectory and distance.

Coupeville businesses donated the cedar wood, metal and paint for the trebuchet. Leake said he built the frame in one day and the arm another day, but it took two weeks to “finesse it” into operating condition.

“It’s a Rube Goldberg thing,” he explained. “There are no plans on the Internet.”

Leake’s wife Sharon assisted with the effort and helps with the demanding job of cocking the big arm for another firing. The cedar frame and arm have the flexibility the structure requires, and make some interesting noises under stress.

“It cracks and groans,” Leake said. “I love the noises it makes. It makes you want to get dressed up in some costume.” There are no plans to wear medieval military costumes, but who knows what might develop over time.

While the trebuchet’s arm moves at tremendous speed, launching squash will be safe. The launching pin is attached to a rope, so participants can stand well out of harm’s way when firing.

“Kids can pull the pin and shoot. A 2-year-old can pull it,” said Sharon Leake.

How well the trebuchet stands up to intense use has yet to be determined. That won’t be known until the squash toss is held Oct. 13.

“I just hope it holds together,” Leake said.