Usually less than 10 Hatz biplanes show up at Oshkosh in a given year, but 2008 will deviate from that norm for the 40th anniversary of the CB-1 design that was created by the late John Hatz of Gleason, Wisconsin, and first flown in 1968.

The Hatz Biplane Association type club is organizing "40 for the 40th" to mark the milestone and hopes to have as many as 40 aircraft attending this year. But even if it doesn’t reach that number, it’s optimistic about setting a record for the most Hatzes to congregate in one place.

"We really don’t have a number of how many Hatzes will fly to Oshkosh; that will depend on the weather," says Chuck Brownlow of Waupaca, Wisconsin, and past president of the type club. "We’re hoping to get the largest gathering ever—at least 15 or 16."

Along with the original model are the Hatz Classic, Hatz Bantam, Hatz Custom, and the Smith Mehlin Warner Hatz.

The planes and pilots were scheduled to converge in Brodhead, Wisconsin, July 25-27 for the 10th Annual Hatz Biplane Fly-in and annual meeting. Then as many of them as possible will fly to Oshkosh on July 27 as part of "H2O"—Hatzes to Oshkosh.

The association estimates there are 150-175 finished Hatzes worldwide, although nearly 1,000 sets of plans are in circulation. The last Hatz gathering in Oshkosh was in 1990, when 14 of the biplanes gathered, Brownlow said.

"It really is a miracle to get a number of these planes together because they are spread throughout all 50 states and seven or eight foreign countries," he says. The group has members in Germany, New Zealand, Australia, France, and Great Britain, and Hatz projects are underway in South Africa and Switzerland.