The Gee Bee Model "Z" Super Sportster

  • During the Great Depression the market for Sport airplanes was all but gone, the only thing left going was air racing, and an amazingly large sum of prize money was being offered at the Cleveland National Air Races. Robert Hall the Granville brothers engineer, convinced the Granvilles to build a racer that could win the Thompson Trophy Race.
    to help the Granvilles afford this project, Bob Hall got Pratt & Whitney to loan them the hopped up R-985 that the Laird Super Solution used to win the Thompson Race the previous year, and Curtiss loaned them a prop. Also the Springfield Air Racing Association (SARA) was formed to induct local civic pride and money.
    Shares of the association were sold to Springfield, Mass business men. So the Gee Bee-Z was built.

    The Gee Bee Z in flight.( Note that the #4 had not been painted on it yet(click picture for a larger view)This aircraft had a Gross weight of 2,280 pounds and the factory modified 535 h.p. Engine, this equated to a power loading of 4.26 pounds per horsepower.
    Bob Hall made the first flight of the Gee Bee-Z on August 22,1931.
    The 1931 National Air Races was a big triumph for the Granville Brothers and SARA.
    Racing the Z, Y, D and E models, they cleaned up in the Pylon events, but the Z took the head line races, Lowell Bayles won the Shell Speed dash at an average of 267.342 which was the fastest speed ever recorded for a land plane, then won the Goodyear Trophy race with an average of 206 mph.
    Bob Hall also had his turn and won the mixed free for all. Between Hall and Bayles they won over $12,050 and the model Y won $5,350, the SARA stock holders were happy.

    The only disappointment at Cleveland had been the Z's failure to break the World 3 Kilometer speed record for land planes, which was 278.48mph.
    The Z model was refitted with a P&W R-1340 that produced nearly 800 hp, now the power loading was 2.85 pounds per horse power.
    On December 1, 1931 Lowel Bayles attempted the speed record again and made four passes at an average of 281.75 mph, but did not surpass the old record by the required 4.97 mph.
    On December 5, Bayles tried again, but after diving into the course from 1000 feet and leveling off at 150 feet as rules allowed.
    The Z suddenly pitched up, the portion of the right wing outboard of the flying wire attachment points failed and the racer crashed killing Lowell Bayles instantly.

    In Tom Granville's hand written day by day diary, his entry on Dec. 5, 1931 reads verbatum as follows:

    "Bayles killed trying for record in Detroit. 75 feet off ground at estimated 300 MPH. body found many ft (50') from wreck wrapped in his overcoat. Prop found 200 ft from debris.

    Trying to better world mark set by Warrant Officer Bonnet of France 278.4 mph. Came close Dec. 1 281.9 mph.

    Thought he could do it since he did fly over 300 a couple of times during some passes - Had to fly over course at height of not more than 164 ft. To gain maximum speed started at point 5 miles from course and 1000 ft. altitude - dove down and came across course level.

    - Nearing end of courseon first pass when crash occurred. Ray Cooper chief observer in charge of speed test, Don Hanchett - a flag man said one wing gave way as plane passed over his head. Bayles had exceeded American record held by Al Williams 266 mph. Observers would probably claim American record for Bayles since he averaged 281.9 on Tuesday.

    Bayles 31 - Native of Mason Ill. forced to give up studies at U. of Ill because of eye trouble. Went to work as electrician intending to become mining engineer."

    Many causes for the crash have been speculated,one story is that two young boys brought in Bayles' smashed goggles and the plane's gas cap which they had found on the course some distance from the crash site. The conclusion was that most likely the gas cap blew off at 200 mph,stunning or killing the Bayles and causing him to make a violent movement of the stick, but after 67 years,analysis of the crash video has revealed the right wing failed either due to aileron flutter and/or due to a wing spar failure. Lowell Bayles landed too fast to stop before hitting the fence at the end of the runway on the flight prior to his fatal flight. Upon reaching the end of the runway, he ground looped to avoid the fence, and drug the right wing . . . and possibly damaging the spar. As there was no aerodynamic or mass balancing of any of the flight controls on the Model Z, it was probably a combination of both aileron flutter and weakened spar failure modes. The flutter induced loads on the weakened spar is most likely what caused the wing failure. it is obvious that the exact cause of this crash will never be known for certain. This ended the short, spectacular and highly successful Gee Bee Model Z.
    It was built in 5 1/2 weeks, flown over a period of 106 days from the start of its construction to its untimely end. Some 47 years latter another Gee Bee Z took to the air again.
    It would be Bill Turners Gee Bee Z.(Not an exact replica because it had a longer fuselage, longer wings, and 85 fewer HP) , It was completed and flown on November 25, 1978. This aircraft was ultimately purchased by the Disney Corporation and was used in the movie the Rocketeer.It was trucked to Oshkosh in 1991 and 1995 for the EAA's annual fly-in's Golden Age of Air Racing program and is now on display at the Santa Monica Museum of Flying.

    A second Gee Bee Z (An exact replica) has been Completed and is on display at Kermit Weeks Fantasy of Flight, Polk City Florida!)

    Gee Bee Z replica site! geebeelogo
    Check out The Jim Kimball/Jeff Eicher and Kevin Eicher, Gee Bee Z replica,Site!

    A few Model Z notes of interest:

    Harold Moon had invested $2000 in SARA, and was to have flipped a coin with Bob Hall for the first flight in it. However, before construction was completed, Harold Moon's parents pleaded with him to withdraw from SARA and get his money back. Keep in mind Harold Moon was a college aged boy of 24 or so whose parents had just put through Harvard. He might have met the same fate as Bayles. The engine loaned to the Granvilles for the Model Z by Pratt and Whitney was the same engine the Laird Super Solution used the year before.

  • The following is a transcript of an article that appeared in October, 1931 Areo Digest.

  • I would like to thank Scott Brener for transcribing and providing this very interesting article.

    Z.D. (Granny) Granville wrote this article)

    Aero Digest October, 1931

    Gee Bee Super-Sportster (Model Z)

    Winner of Thompson Trophy at 236.24 M.P.H.

    By Z.D. Granville

    Contrary to the general belief, the Granville Brothers Gee Bee Super-Sportster is not a radically new ship in general design and construction.

    Practically every part is either a duplicate or modification of the standard Gee Bee Senior Sportster two-place job now available commercially. The account of details, construction, mechanism, etc., following describes both models with the exception of several minor details.

    The motor is a Pratt & Whitney Wasp Jr. suped (sic) up to 535 horsepower at 2,400 revolutions per minute. The metal propeller is a Curtiss fixed pitch type with a diameter of 8 feet two inches and a pitch of nine feet three inches.

    The fuselage is welded chrome-molybdenum. The wing stub bracing is carried internally. With the exception of this bracing and general size, the fuselage construction is identical with the Senior Sportster, as are also the motor mounting. The N. A. C. A. cowling and other motor attachments.

    The landing gear is fork type, having a six-inch travel on the oil and spring shock absorber.

    The shock absorber unit is new but is a development of the original type used on the models E, D, and Y Sportsters. Aircraft Products Company wheels and brakes are actuated by the full-back position of the stick and the directional brake control by rudder pedals.

    The 23-inch Goodrich tires are 6.50 by 10 and the wheel tread is 71.75 inches.

    Boots and fairing are attached to the wheel forks in a way that they travel with the wheel straight up and down, keeping in the line of flight and keeping the wheel and tire covered to a maximum at all positions. The only difference in this construction and mechanism from that of the standard Senior Sportster is the absence of the emergency brake lever which locks the commercial job the same as a parked car.

    Wheel streamlines are 10.5 inches wide. The tail skid is of the spring leaf type, streamlined with rubber.

    The wings are of wood construction, using solid spars and are locked up with nuts. Ribs are spaced 5.4 inches apart and the main beams 35.5 inches apart.

    The flying and landing wires by Stewart Hartshorn are single. The wire pulls attached to the compression members relieve the spars of bolt holes and relieve the ribs of all except fabric loads.

    A hammered aluminum fillet fairs in the angle between the wings and body. The M-6 wing curve is used.

    Ailerons are torque tube type with formed sheet steel ribs welded to the torque tube. The hinges form bearings for the main torque tube.

    The extension of the hinges telescopes directly inside the wing compression member at the rear spar. Angular ball and socket controls are used with ball bearing mountings for all torque tubes. This type of aileron construction eliminates the danger of fluttering and minimizes the possibility of pulling off an aileron.

    The tail surfaces are welded steel tube construction with wrapped hinges working on the torque tube itself. The rudder, 19 inches wide, is actuated by cables, the 17-inch elevators by a push-pull tube and double cables.

    The stabilizer, which is 18 inches wide and has a span of eight feet, moves up and down at the rear and is controlled by the screw type jack with crank control in the cockpit, giving an irreversible micrometer adjustment.

    The adjustable stabilizer was found after a test to be unnecessary and when once set has no need to changed.

    The general construction of the wings, ailerons, landing gear, tail surfaces, controls, etc., is identical in all respects other than size with the commercial Senior Sportster. The cockpit cover or windshield is comprised of a large cover having a celluloid dome of sufficient size to give the pilot head room.

    This cover drops on after the pilot is seated and is held securely in position by quickly releasable door fasteners.

    In case of emergency this entire cowling over the cockpit can be released by one pull of the lever, allowing the pilot absolute freedom in leaving the ship.

    The Fiberloid portion of this cover is so designed as to give vision in every direction other than straight back, and also so that the line of vision is approximately at right angles to the Fiberloid.

    This arrangement allows the pilot full protection from the wind, effecting the consequent minimum of resistance, yet affords undistorted and unobstructed vision ahead, up, down, and on all sides.

    Cockpit ventilation is accomplished through tubing which brings in fresh air from the wing stubs, and is controlled by a ventilator in the instrument board.

    Contrary to the usual design, the fuselage is faired out to form a gentle outside curve from the 46-inch diameter N. A. C. A.

    cowling back, gradually flattening to the vertical tail surfaces at the rear.

    This plump fuselage gives it the appearance of being abnormally short coupled. The company has received criticism of this so-called short coupling, but its engineers state that their past experience with the various Sportster models has proved to their satisfaction that this design is as rigid, maneuverable, and as stable as the longer types of fuselages.


    Top speed ....... 270 miles per hour

    Cruising speed .. 230 miles per hour

    Landing speed .... 80 miles per hour

    Fuel capacity ........ 103 gallons

    Oil capacity ............ 11 gallons

    Cruising range ......... 1,000 miles

    Wing area, including ailerons .......... 75 square feet

    Wing span ......... 23 feet 6 inches

    Chord at root .......... 50.4 inches

    Length overall ...... 15 feet 1 inch

    Load factor, high angle of attack ........................ 10

    Incidence angle .......... 3 degrees

    Dihedral angle ......... 4.5 degrees

    Aileron area ....... 9.5 square feet

    Stabilizer area .... 8.4 square feet

    Elevator area ...... 6.9 square feet

    Fin area ........... 2.2 square feet

    Rudder area ........ 4.9 square feet

    Power, supercharged Wasp Jr. ............... 535 hp at 2400

    Weight empty .......... 1,400 pounds

    Gross weight (full load) ......... 2,280 pounds

    Wing loading (full load) .. 30.2 lbs. per sq. ft.

    Power Loading (full load) ...... 4.26 lbs. per hp

    Bob Hall taxies the Gee Bee Model "Z"(click picture for a larger view).

    Bob Hall and the Gee Bee Model "Z"(click picture for a larger view).

    Gee Bee Model "Z"(click picture for a larger view).

    Gee Bee Model "Z" Bill Turner replica used in the movie the Rocketeer. It now is on display at the Santa Monica Air Museum(click picture for a larger view).

    Gee Bee Model "Z" Jim Kimball/Jeff Eicher replica now owned by Kermit Weeks. It now is on display at the Fantasy of Flight Museum at Polk City, Florida (click picture for a larger view).

    Gee Bee Model "Z" Jim Kimball/Jeff Eicher replica now owned by Kermit Weeks. It now is on display at the Fantasy of Flight Museum at Polk City, Florida (click picture for a larger view).

    Gee Bee Model "Z" in flight. Note that the #4 was not yet painted on the aircraft yet.(click picture for a larger view).


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