11 Biplane Class Specifications
11.1 Introduction
The following rules and specifications are for the Biplane Class. All Common Rules apply as appropriate. The dimensions of Biplane Class aircraft are based on the Biplane Class Rules that follow.
11.2 General
11.2.1 All entries must be a scale representation of full size aircraft that have raced.
11.2.2 Any biplane type or variant that has raced in a Biplane Class at the Reno National Championship Air Races is a valid subject to model for the USRA Biplane Class.
11.2.3 Any new design or kit, including variations, must have prior USRA approval before entering a USRA sanctioned race.
11.3 Weight
10.3.1 Minimum aircraft weight is 20 lbs. (dry). Maximum weight is 30 lbs. (wet).
11.3.2 Aircraft weight may be verified at any time during a race.
11.4 Size, Shape and Scale
11.4.1 Aircraft are to be controlled first by outline and shape, then by actual measured wing area and finally fuselage and component minimums. The intent of this class is to have scale appearing race planes, not non-scale ones built to meet minimums.
11.4.2 Control surfaces may vary in size but must follow the full size aircraft's outlines.
11.4.3 Scoops are required if present on the full size aircraft.
11.4.4 All aircraft must have and use scale-like non-retractable landing gear and wheel pants.
11.4.5 Tail wheels must be in the scale location and steerable.
11.5 Fuselage and Component Minimums
11.5.1 Bumps, lumps, profiles, etc., are prohibited to obtain dimensions.
11.5.2 Overall length, including spinner, is preset on each approved aircraft with a deviation of +/- 1 inch. Minimum overall length is 60 inches.
11.5.3 Fuselage minimum (width at pilot's shoulder location) is 6 3/4" inches.
11.5.4 Cowl width minimum (at full size engine location) is 10 1/2" inches.
11.5.5 Minimum height of canopy to fuselage bottom is 11" inches.
11.5.6 Minimum spinner diameter is 4" inches.
11.5.7 Minimum wheel pant width is 2 1/8" inches.
11.5.8 Minimum main gear tire (diameter x width) is (3 1/2" x 1")
11.5.9 Minimum tailwheel tire (diameter x width) is (3/4" x 5/16")
11.6 Wings
11.6.1 Airfoils suitable for models are acceptable for both wing and tail groups.
11.6.2 The minimum wing area (combined) of the top and bottom wing is 1460 square inches. Aircraft shall have no less than 30% (438 sq. in.) of the 1460 sq. in. total combined wing area contained in the smaller of the two wings.
11.6.3 Minimum wing airfoil thickness is 12% of the chord.
11.6.4 Wing struts/cabanes are required and must be scale-appearing in shape and angle to those of the full size aircraft. Flying wires are not required.
11.7 Engine and Exhaust Systems
11.7.1 4.88 cubic inch displacement (81 cc) maximum size reciprocating engine. No modifications of any kind are allowed. This includes the removal of chokes, piston ring heating, porting, polishing, etc. Aircraft must use a stock 4.8 cu. in. (80cc) maximum, magneto ignition, Zenoah GT80TM or 445. No modifications of any kind are allowed. This includes removal of chokes, piston ring heating, porting, polishing, etc.
11.7.2 Any commercial brand of replacement spark plug is permitted.
11.7.3 Indexing of the spark plug by using various thickness washers is permitted.
11.7.4 Straightening of the crankshaft is permitted.
11.7.5 Engine may not protrude from the cowling. Carburetors, spark plug boot (cap) and wires may protrude from the cowling.
11.7.6 Exhaust pipes may not exceed 8 inches length, measured from the flange face along the centerline. The inside diameter from end to within 1 1/2" inches of the mounting flange must remain constant. (1 1/2" inches allows fit to rectangular exhaust port shape)
11.7.7 Tuned pipes or similar systems are prohibited.
11.7.8 The removal of the recoil spring starter is permitted.
11.7.9 Any extension shaft length is acceptable.
11.8 Fuel
11.8.1 Engine fuel will be the only liquid carried in the aircraft. Any foreign liquid, other than provided fuel, will be grounds for disqualification.
11.8.2 Fuel will be supplied by the race promoter/event organizer. Fuel will be formulated and mixed according to the USRA F1-GT Class fuel specification as stipulated in paragraph 4.10.4 of the Common Class Rules.
11.8.3 A means of defueling through the fuel supply line to the engine must be provided.
Please Note: Some sources for kits and plans of these aircraft include: ACE R/C, Byron Originals, Eagle Aviation, Ohio R/C, Horndog Aircraft, Lanier, KT Aviation, Godfrey, Wendell Hostetler Plans, Nick Ziroli Plans, Miles Reed Plans, RPN Racing (Ed Rankin) and RnR Products.