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AGENDA ANNEX 7z F3 Pylon Sub-committee
Agenda Item 13.11 o)
ANNEXT 5Y – F3T Pylon Racing
ANNEX 5 Y CLASS F3T – SEMI SCALE PYLON RACING MODELS OF LIMITED TECHNOLOGY
5.W Intention: This class is defined for semi scale pylon racing at a limited level of technology in aircraft aerodynamic design, aircraft construction, propeller and power plant with maximum safety.
Rules strategy: The technical rules have the intention that speeds will not increase substantially over the years in order to maintain safety and controllability of model pylon racing aircraft. This is achieved by a limitation to approved models of a semi scale type, approved and unmodified engines plus exhaust systems and approved , propeller dimensions and materials.
A special CIAM-F3X committee with a minimum of 5 experts from different countries, nominated by their NAC’s controls the class by advising on:
Approval of F3X models
Approval of F3X engines
Approval of F3X propellers
The names of the members of the F3X committee are published on the CIAM web site.
The F3X committee works under the responsibility of the CIAM RC Pylon Racing Subcommittee
Approved models, engines and propellers are published on the CIAM web site.
The F3X rules and Annexes are similar to the F3D rules and Annexes (FAI Sporting Code section 4 – Aeromodelling Volume F3D Radio Controlled Pylon Racing) except for the technical specification of the models
5.W.1 Definition of Radio Control Pylon Racing Model Aircraft:
5.W.2 Technical Specifications of Pylon Racing Model Aircraft
The model aircraft must be of conventional design with forward wing and an aft empennage and shall be a recognizable replica of a full-scale, human-carrying, propeller-driven aircraft, that either raced in or was built for close course or cross country racing or a speed record attempt. No delta or flying wing type aircraft are permitted
Only models that have been approved by the F3X committee will be allowed.
For details of the approval procedure and criteria see Annex 5.W.A1
Weight, less fuel but including all equipment necessary for flight, shall be at least 1800 g and not more than 2200 g. If ballast is used it must be permanently and safely affixed.
5.W.4.1. Depth and width
Fuselage depth will be Minimum 127.0 mm at its deepest point; except that full-scale prototypes with belly-mounted radiators shall have a fuselage depth of at least 152.4 mm. Depth includes the radiator or belly scoop (if any) and the windshield canopy, pilot’s head, or headrest, but does not include tail surfaces, dorsal or sub fins, tail skids, or non-scale protuberances.
The fuselage shall have a minimum width of 76.2 mm, the measurement to be of the fuselage body and to exclude any fins, fillets, attachments or spacers. Width and depth points need not to coïncide .
5.W.4.2 Cross-sectional shape and features:
At some point the fuselage will have a minimum cross sectional area of 80.7 cm² excluding fillets and cheek cowls and competitors shall provide templates to prove this. Fillets are not considered part of the fuselage or lifting surfaces.
(a) Profile representations of any significant feature of the full-scale prototype are prohibited. Cross-sectional contours at the height and width measurements and at stations determining the likeness to the full-scale prototype shall maintain the integrity of the contours in the full-scale prototype. The only exception permitted shall be in the engine compartment for maintenance purposes.
(b) Cockpit, cheek cowls, canopy, and belly scoop, if any, shall have at least a 15.9 mm radius at their
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widest point so that a 31.7 mm diameter ball (pilot head in the cockpit) would fit inside, tangent to the outer surface. A cockpit, cowl, canopy, or scoop with an oval or rectangular cross-section and corners of less than 15.9 mm radius satisfies this requirement if the hypothetical 31 diameter ball would be fully enclosed. The cockpit need not be transparent and a dummy pilot´s head need not be fitted.
(c) The front end of the fuselage shall be configured so that the engine head and cylinder protrude on all sides at least 19.0 mm, not including the glow plug and the exhaust system is fully exposed for its entire length. However, the fuselage may incorporate a shallow channel, dimple or trough to provide clearance for the exhaust system. In addition, the access hole for the engine crankcase and mounting lugs may be covered with a piece of fiberglass, Mylar, or other stiff material that restores the original contours of the fuselage in that area.
5.W.5 Lifting Surfaces
5.W.5.1. Area of wing
Total projected area of the wing surface shall be a minimum of 25.8 dm².
5.W.5.2 Wing Span
The maximum wing span shall be 1422.4 mm.
5.W.5.3 Wing Thickness
Wing thickness at 75 mm from the wing centre shall be at least 22.2 mm. Thickness shall progress uniformly in a straight line or convex taper from root to tip; except that, if the full-scale prototype has a different progression, the progression on the model may be similar. The wing taper, in addition to other distinctive design features, is subject to the design approval requirements.
The engine must be of the single cylinder reciprocating piston type, with a maximum total swept volume of 6.60 cm3. Propellers must rotate at the speed of the crankshaft. The engine shall have only one front air intake and one side exhaust.
Only engines approved by the F3X committee are allowed. See annex 5.W.A1 for engine approval procedures and criteria.
Engine air intake shall be circular with a maximum diameter of 9 mm.
In case fuel without nitro content is supplied by the organizer ( see 5.W.12) , the diameter of the air intake shall have a maximum diameter of 12 mm.
No modifications to the following parts of the engine are allowed:
crankcase back plate.
piston, conrod, piston pin
technology of the bearings. (Only standard size, single row, full steel ball bearings allowed for the crankshaft and only plain bearings allowed in the con rod).
5.W.7 Exhaust system:
(a) General description: The engine shall be equipped with an expansion chamber muffler, zero-boost muffler, or tuned muffler as provided by the manufacturer for the engine being used, and having a single exhaust outlet with a maximum outlet area of 40.2 square millimetres (equivalent to the area of a round hole measuring 7.15 mm diameter).
(b) Inner configuration or tuned mufflers: A tuned muffler used in this event shall have only one internal part, a straight tube or extractor of the type commonly known as a “mini-pipe”. The mini-pipe shall have a constant, circular cross section and constant inside and outside diameter, with the following exception: the sidewall of the tube may be thickened not to exceed 2 mm wall thickness, within 12.7 mm of the front end of the mini-pipe where it attaches to the header.
(c) Outside dimensions: The distance from the centre of the piston to the centreline of the muffler shall not exceed 70 mm. The overall length of the muffler shall not exceed 185 mm, measured from the front of the header to the back of the exhaust outlet. The outside diameter shall not exceed 45 mm and both the inside and outside diameter of the outside shell of the muffler shall remain constant for at least 75 mm.
(d) Modifications: No modifications to the muffler, as provided by the manufacturer, are permitted except that the muffler may be tapped for a pressure fitting to supply pressure to the fuel system.
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5.W.8 Fuel pressure
If the tank is pressurized, only the pressure from the exhaust system is permitted.
5.W.9 Propellers and spinners
5.W.9.1 Propellers shall be fixed, with two (2) fixed-pitch blades of equal length, area, and shape.
Composite resin continuous fibre construction propellers and metal propellers are not allowed.
Either wood or a chopped carbon fiber filled injection-molded compound. The material of Injection moulded propellers needs approval of the F3X committee,
Wood propellers may be modified from a commercial product or can be home made . A wood propeller shall be made from a single piece of wood and may be finished with a clear coating for purposes of waterproofing or balancing only.
Wooden propellers: No limits
Injection Molded propellers.
Only stock propellers which are approved by the F3X committee and which commercially available shall be used.
A propeller once approved shall be eligible for competition so long as it remains commercially available. The propeller shall have a minimum diameter of 7.4” ( 188 mm ).
Only approved propellers can be used. See annex 5.W.A1 for propeller approval procedures and criteria.
Changes to the propeller blades are not permitted, except for:
a. one blade may be sanded on the top (front) side only for balancing.
b. One side of the hub may be sanded for balancing.
c. The shaft hole may be enlarged, but only as much as necessary to fit the engine crankshaft. The enlarged hole shall be concentric with the original hole.
d. Edges and tips may be sanded, but only as much as necessary to remove sharp moulding flash.
5.W.9.2 A rounded nose spinner of at least 25 mm diameter, with a nose radius of not less than 5 mm (ABR B.19.4) must be fitted. The spinner shall be made of metal only.
5.W.10 Landing gear.
1) Location and size: The landing gear shall be fixed and shall resemble that of the full-scale prototype aircraft as to location on the airframe and the number of wheels used. At least two (2) of the wheels shall have a diameter of at least 2-1/4 inches.
2) Streamlining: Wheel pants, wheel spats, or strut fairings are not required, and are permitted only if they were used on the full-scale prototype.
Only non retractable landing gears are permitted.
A tail skid may be used in lieu of a tail wheel. A positive means of steering on the ground shall be provided; rudder control is acceptable.
5.W.12 Fuel .
The fuel will consist of 60 - 80% methanol, a minimum of 18% oil, (wherein a minimum of 3% is castor oil) and will contain not more than 15 percent nitromethane. All percentages by volume. The fuel composition (or commercially available type of the fuel) shall be announced in the invitation of the competition and will be supplied and dispensed by the organizer.
In case an organizer supplies fuel without nitromethane, see 5.W.6 for air intake diameter.
5.W.13 Technical checks and safety requirements
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5.W.16 Transmitter and frequency check
5.W.17 Race Course, Distance and Number of Rounds
5.W.18 Race from Start to Finish
5.W.19 Timekeeping and Judging
5.W.20 Infringements and Penalties
5.W.21 Scoring and Classification
Note: 184.108.40.206 does not apply to F3X.
The following F3D annexes also apply to F3T
ANNEX 5Q - GUIDELINES FOR AIRFIELD LAY-OUT,
ANNEX 5R - GUIDELINES FOR DUTIES OF PERSONNEL
ANNEX 5S - GUIDELINES FOR TECHNICAL EQUIPMENT
ANNEX 5T - GUIDELINES FOR DRAW OF RACES
ANNEX 5U - GUIDELINES FOR PRACTICE FLYING
ANNEX 5V - GUIDELINES FOR ORGANISERS
Note: Within the annexes, references to World and Continental Championships do not apply to F3T.