Stits Flut-R-Bug Project Mike, Chris & Ed Cosman

Ray Stits designed the Flut-R-Bug in the mid-1950's as a very simple, very low cost personal "puddle-jumper". The original design was a strut-braced mid-wing, tricycle gear, open-cockpit, single-place craft powered by a 4-cylinder Continental engine. The wing was constructed with wooden spars and band-sawed 3/8" plywood wing ribs, with a leading-edge wrap of aluminum. The ailerons were full-span narrow strip-types so they could be actuated with a simple set of push rods on the outside of the fuselage. The remainder of the aircraft was 4130 steel tube, and everything was covered with doped fabric. Shortly after it was introduced, he created an extended version that had two seats in tandem, and this was the version that most people built. He sold plan sets for $25, which got you a dozen C-size blueprints and one full-size wing rib template.

As 'Bugs took to the sky with larger and larger engines, he put out several modifications and improvements to solve problems people were discovering. One of these was to enclose the cockpit to reduce turbulence on the tail, and to weld some diagonal bracing around the rear-seat passenger to stiffen the truss box containing the rear spar compression tube. An additional brace was put on the horizontal stabilizer, and some primitive fairings were developed to reduce drag due to the large gap between the wing and the fuselage.

A completely stock Flut-R-Bug is a study in drag. There are two struts on each wing, built from round 4130 tubing. The struts that were added to the stabilizer, along with the flying wires that braced the vertical and horizontal tail members, were all round stock--no streamline stuff at all. It was designed so the wings could be easily removed for storage at home, so there was a fairly wide gap between the wing root and the fuselage. The cowling was all flat-wrap aluminum, which gave a pleasing profile but functioned more like a large strainer, aerodynamically speaking. It had Cub style eyebrow cowls on the cylinders, and used standard wheelbarrow wheels and tires for the main and nose gear. The "brakes" were home-made mechanical band-type affairs which would hold the 'Bug against the run-up if you pulled on the lever hard enough. The "suspension" was a rubber bungee cord that was exceptionally stiff, unless you landed really hard, in which case it wasn't stiff enough. The exposed cylinders were right in front of the wing root, and pretty well spoiled all the airflow along the sides of the fuselage. The wings were great big barn-door affairs--about seven inches thick, with a five-foot chord and a total span of 26 feet. But it was light--about 625 pounds empty, with a gross of 1125. Unfortunately, Ray is a small guy, and the Flut-R-Bug is only a two seater if both occupants are "svelte", since they both sit behind the aft CG limit. Back when I was a comparatively fit fellow of 220 pounds, I started expanding the CG envelope by putting bags of sand in the rear seat. When I got to 80 pounds, I could no longer trim it for hands-off flight, and decided that it should best be treated as a single-place airplane. However, Marian was able to fly with our toddler-size kids.

The Flut-R-Bug is a fairly short-coupled airplane, and there is effectively no stick force in the pitch direction. This makes the transition from something like a Cessna 150 quite interesting. On the other hand, the ailerons only seem to want to "suggest" rolling, no matter how far you deflect them. If you take your feet off the rudder bar, the plane will slowly start cocking itself sideways until the ball is nearly to the limit, but responds quite readily if you manage the rudder properly. Full power [stalls], it flies clear down to where the airspeed is just bouncing off the peg, but the stick forces finish disappearing and you can put the stick anywhere and not much happens. If you try to hold it with rudder, you will wind up upside down unless you react quickly when it finally lets go. Stits wisely declared "No Aerobatics!"

The other (and only other) bad habit relates to the landing. The 'Bug will get off in about 400 feet at Airport 2 [in Salt Lake City] on a hot summer day, indicating about 40, and land similarly short. But the airframe is so draggy that you need a lot of extra speed if you expect to arrest its huge sink rate in the flare. Otherwise, you will do a carrier-style landing, and maybe break the bungees (and a few other things).

Over the years, Flut-R-Bug N7371C has been pranged several times this way by previous owners. We learned that if you keep 70 all the way down the approach. you can break the decent nicely, squeak it on, and the speed drops smoothly to zip, all in about three seconds and two hundred feet of runway. If you try to fly the approach at 60, it gets really hairy, and at 50, you're going to hit hard for sure. Fortunately, you can turn short final at pattern altitude, crank it into a forward slip, and make the numbers every time.

We’ve owned two 'Bugs. This one was built right here in SLC in 1957 by a local doctor, and came to us in the year 2000 in essentially dead-stock condition. Since then we have converted the canopy from fabric covered to a smooth fiberglass shape, built aluminum fairings for the wing/fuselage area, and modified the front-seat area for more room and a more reclined seating position. We also modified the wing struts to have a streamline cross section, and built a larger gas tank (17 whole gallons, now).

Aerodynamically, we’ve upped the cruise from 80 to about 90, and significantly improved the rate of climb. Last February we brought the 'Bug back to the shop to put a real cowl on it. We expect the new cowl to add perhaps another 10 mph, and some more rate of climb. Our previous Flut-R-Bug would true out about 105, and this will be a little cleaner when we are done.

Mike Cosman - 2006


a little history