N646CH Super Cub, L-21

Factory New Lycoming O-320 B2B Modified by Aerosport Power
156 ttsn airframe and engine
2300 lbs Gross Weight
1250 lbs Empty Weight
48 Gallons of fuel at - 288 lbs
762 lbs useful load with full fuel

Experimental Super Cub fabricated from a Backcountry Super Cub Kit, built as a lend lease L-21 RAAF Korean era Artillery Observer. From the airframe and engine, to the instruments, this aircraft was built from 100% new components; no used parts were overhauled for use. Only the transponder was yellow tagged and not new. Build began in 2008, and first flown and licensed in 2011. Annual May 2015. Fresh annual with sale.

This is a very unique Cub with no expense spared or fine detail overlooked. Black walnut veneered light weight 6 ply floorboards, custom machined stick grips from stacked leather and brass, with an inset curved coin (Australian 1940¹s penny) at the top, powder coated aluminum throttle balls machined to allow push to talk installation in ball, and custom machined control knobs.

All instruments new, disassembled to allow period correct silkscreened faces (some up to 7 color screens) to match with same fonts and with appropriate makers marks. Even the modern vertical card compass has had the glass removed and the indicator rescreened to remove the swept wing image and replaced with a cub outline indicator. Panel instruments include a period correct NOS British turn and bank, disassembled certified and rescreened. Instrument panel laser engraved satin black powder coating. All stenciling inside cabin silkscreened for ultra sharp lettering, there is no vinyl lettering anywhere. Dual Grimes red/white, dimmable, removable coil cord cockpit lights. Aluminum chart case. Very detailed and dry engine compartment. All fuel lines mandrel bent and adel clamped paralleling frame members, all electrical wiring hand tied every 2 inches in bundles with waxed flat thread. Wires labeled under shrink tubing at both ends for easy identification (see images). Large capacity aluminum storage box under rear seat. Turtledeck, rear seat, and supporting light-weight plywood pieces are all designed for easy 10 minute removal, and hinged to fold so that they can easily be stored in aft tail section leaving the front baggage compartment and rear seat area as one large capacity carrying space. Toe brakes and 5-point seatbelt harness. 3" extended main gear with heavy-duty shock springs with 8.50 x 6.00 tires and wheels. Extended baggage compartment with aluminum walls. 48 gallons of fuel from two 24 gal tanks. Two sets of seat cushions come with plane, one is military khaki with leather trim, upholstered over multi layer and density foam from Oregon Aero, the other is all distressed leather.

Communication radio:       ICOM 210
Transponder: King KT 76A
ELT:  AK-451 s/n 16735  Hex ID AE2C41057C002CD,  new battery March 2016

Engine and mount.

Built up from a factory new zero time, Lycoming 0-320 B2B by AeroSport Power. All internal components balanced/weight matched, roller cam, and ECI cylinders flow ported and polished, putting out over 170hp. Sky Tech 149-12HT light weight starter, Plane Power AL12-C60 Alternator. Silicone heat pad mounted on oil sump for winter preheating. Engine mount is a zero thrust swing out type built using 0.49 tubing instead of the original 0.35 material in Pipers. Stainless steel firewall.

Frame details (please see images for quality of welds throughout).

All tubes are CNC cut, meaning each and every tube fits together as tightly as possible inside the jigs before the welding begins. There is no filling in any gaps or irregularities in the joints (which occur when tubes are cut by hand) during welding as they do not exist. The fuselage is a modified design for 4 inches of increased width at the widest point, and incorporates what are commonly referred to as Alaskan Mods, or Altee Dodge style modifications. One feature of this is that it is built with all 4130 chrom-moly 3/4” tubing all the way through to the firewall, with heavier wall thickness in critical areas, (the original Piper aircraft were about 35% in the original PA-18). The original fuselages tubing tapered from 3/4 to 5/8” for production purposes (they used to make the fronts separately and just slide them in). Original Piper tail spring mount square tubing was a significant weak spot, this has also been replaced by thicker walled chrome moly material. Overhead X bracing is one of the more well known modifications. It gives more strength to the upper cage when there is a wing strike. Nut plate brackets are installed on the bottom of the rear of the fuselage to allow for a larger access plate. Shoulder Harness Mounts welded on. (Original cubs have to use a heavy bolt-on bracket as per STC.) Front Seat Belt Brackets originally were installed on the seat itself. These are mounted directly to the fuselage. Pulley brackets and tabs are fabricated from one gauge heavier thickness to prevent the common bending seen in old Pipers. Z shaped door frames help seal the doors. Handles for the tail on both sides of the plane, for easier ground movement.

Landing Gear.

Main tube has been increased from 1 3/8 diameter to 1 1/2. The original gusset consisted of one piece of flat bar welded from the axle to the main tube. This area is now a scab plate welded on the two tubes, about 6 inches long. The new flat bar is welded the whole length of this plate to help distribute the stress area. 1 1/2 inch axles as opposed to the original 1 1/4 inch axles. Frame incorporates a 5/8 tube in between the front and rear pickups. Heavy duty springs make easy work of rough terrain. Wheels and brakes are Grove 6:00 x 6 36-2A, with Matco MCMC-4 cylinders. Tailwheel is an Alaskan Bushwheel 3224A (Scott 3200 style).


All wing structure is cut using CNC for precision. The original Piper aircraft used standard wire bracing in the wings. The design of these wings uses the much stronger drag and anti-drag compression tube design. It is basically the same concept as the first bay (where the gas tank is and uses a 4130 tube) in Piper planes. This design is used for the full length of the wing. Aluminum round tube instead of the original wood is used in the tip. Construction utiziles aluminum spars with doublers about which significantly strengthen the structure and increase the aircrafts gross weight to 2300 pounds. Dual lights landing and taxi lights installed. Lift struts are stock sealed Super Cub parts. Whelan Stobes.

This is a true 9.9 inside and out and flies as good as it looks. On a calm day 646CH flies with feet on the floor and hands off the stick, straight and true. This aircraft draws a crowd everywhere you go. This plane is regularly flown into many backcountry Idaho strips. On or off the pavement you won’t be disappointed with its performance.  Lots of pictures of the build available below. They load progressively in groups of about 25, and there are hundreds.  They are in no particular order as they were gathered from several different sources.

Comments by others

“The attention to detail in this plane is amazing. They have thought of the smallest detail and seen that it is present. From reproduction data plates in the cabin that trace a hypothetical a trip from the Piper factory to the USAF to the RAAF, every detail is period correct. The effort and expense put into the instrument face details, is something seldom seen. It’s a 10 point build without any qualifiers put on that statement.”
- JC Paul, Warhawk Air Museum, Nampa ID

“It takes many things to build a world class aircraft. Obviously technical talent plays a big part of it. But the desire to capture the smallest details, even if they will go unnoticed by most individuals, has to be there. Invariably this is all tied two other components that the builders of this aircraft had and those are patience to get it right, and money, to do it the best it can be done without compromise.”
- John Lane, Airpower Unlimited, Jerome, ID. Three time Oshkosh Grand Champion warbird winner.

“The craftsmanship on this plane is first rate. Beautiful tape lines, fabric and sheet metal work make this cub a one of a kind build. The fit and finish of everything is flawless. This plane is the product of craftsmanship where compromise, or good enough was never part of the process. ”
- Johnny Maloney, Plane of Fame Air Museum, Chino, CA

For further information, serious buyers please call either
Brian Hill at 949-278-4362 owner and co-builder, or Don Chapton, primary builder at 208-420-0041

Photo Gallery