KR 1

The KR-1 is the creation of Ken Rand, EAA #30184, Huntington Beach, California and EAA Chapter 92. Back in 1968, Ken and Stuart Robinson, EAA #71345, started two homebuilts based almost equally on the Taylor Monoplane and their control line model airplanes.

The fuselage is the familiar plywood and spruce box. Two ladder-type sides are built up of 5/8" X 5/8" spruce stock and are covered with 3/32" plywood from the firewall to just aft of the cockpit with 1/16" used from there to the rudder post...just like most wooden airplanes from the early de Havillands to the Volksplane.

The "backbone" of the airplane is a 5 foot 5 inch centre section (actually the main and secondary spar carry throughs), which ties the fuselage sides together. This "backbone" serves as the support for the seat bottom and the retractable landing gear with its retract/locking mechanism, attach point for the side-mounted stick and trim control, and, of course, the mounting points for the outer wing panels.

Up front, the little 1200 cc VW engine has been somewhat modified for aircraft use. The crank has a 30 taper to match the tapered hub, the rear main bearing has an oil groove added, the oil breather line is relocated, thin wall exhaust stacks replace the auto equipment, a Revmaster injector carburettor is fitted, and the Wolfsburg ignition is replaced by a belt driven single magneto.

The retractable landing gear is operated by a single handle, which pivots the whole assembly through a fore and aft range of about 90 degrees. Two spring-loaded latches with detents lock the gear in the "up" or "down" position. To retract, the wheels move straight back and up into wells in the centre section leaving about 1 1/4" of the go-cart wheels exposed much like the early, conventional geared Bellancas. The only shock absorption comes from the tires. Whatever flexing the horizontal gear assembly has is from the pivot points outward, and the seat cushion.

The brakes used on the prototype KR-1 are simply tire scrubbers that are intended for differential ground steering and a little braking on the landing roll. Hydraulic go-cart brakes can be used, if desired.

The landing gear legs, including the wheels, are about 17 inches long, which means the leading edge of the wing is about the same height off the ground and the trailing edge literally brushes the grass. The tail wheel is a dolly caster bolted to a length of auto leaf spring. This extremely low-to-the-ground stance is one of the striking aspects in the appearance of the KR-1.

The engine cowl, fuel tank, fuselage turtle deck, vertical and horizontal tail surfaces, and outer wing panels are largely constructed of polystyrene foam! Slabs of polystyrene are glued in place, are trimmed and sanded to the desired profile, and have a layer of Dynel cloth epoxied on to form an amazingly tough and, when sanded, smooth exterior.

The vertical fin is two upright wood spars with a profile rib at the top and bottom. The rest of the fin is polystyrene foam -- including the leading edge! The rudder and elevator are even simpler; there is a leading edge wood spar plus a rib at each end and the rest is foam and Dynel, including the trailing edges, which are knife edged.

Ken Rand and his original KR-1

The turtle deck was built up by gluing on the polystyrene foam slabs and sanding to shape with no bulkheads or bracing of any type. Before the Dynel and epoxy application, you could smash the whole thing to bits with one half-hearted swipe of your hand, but after the Dynel covering had cured, Ken proved its strength to a slightly incredulous FAA inspector by standing on it!

In the area between the instrument panel (also of PS foam) and the firewall, an integral 7 1/2 gallon fuel tank is built in ... of PS foam/Dynel/epoxy, naturally.

The tight fitting cowling is formed around the VW engine by simply gluing the blocks of foam to the engine, shaping, etc. The builder then saws it off, splits it where necessary, bonds in fasteners and snaps it back in place.

Even the spinner is made with foam/Dynel. Ken sawed out a circular piece of wood, glued foam blocks to it, put the whole thing in a lathe and turned it to the shape he wanted and then laid on the Dynel. Sanding, cutting out the prop blade holes and drilling a center retaining screw hole completed the job.

PS foam has little to do with the strength of the finished product. It is merely a filler and, most important, a built-in mold or form for the final shape of the layer of Dynel and epoxy. This outer shell is incredibly light and strong

The wing is composed of two 60-inch built-up wooden spars with a rib at the inboard and outboard ends. Two foam ribs are installed at the Y3 and 2/3 positions between the end ribs for support and shape only. A thick plank is glued on to form the leading edge and the remainder of the wing is planked with one-inch thick slabs of PS foam, sanded to shape and covered with the Dynel and epoxy.

The ailerons are simply sawed out of the wing and are reinserted in the same space, attached to piano hinges that have been bonded in the wells. A spruce strip is installed in the leading edge of the aileron for mounting the hinge.

In summary, Ken Rand's KR-1 was one of the really significant homebuilts at Oshkosh '72 which pioneered the way for many new composite designs. The $500 total cost of the prototype and the prospect of a short construction period were the motivating factors, which made the KR-1 a successful design.

wing span
wing area
empty weight
useful load
gross weight
fuel capacity
VW 1834
12' 9"
17' 0"
62 sq. ft.
375 lbs
375 lbs.
750 lbs.
8-30 gal.
1400 miles


takeoff distance, ground roll
rate of climb
max speed
cruise speed
landing distance, ground roll
service ceiling
350 ft.
800 fpm
200 mph
180 mph
900 ft.
15,000 ft.

limiting and recommended speeds

design manoeuvring speed (Va)
never exceed speed (Vne)
stall, power off (Vsl)
landing approach speed
52 mph

All specifications are based on manufacturer's calculations
Landing gear Fixed conventional or trigear, or retractable conventional.