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
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
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.
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
rate of climb
landing distance, ground roll
limiting and recommended speeds
design manoeuvring speed (Va)
never exceed speed (Vne)
stall, power off (Vsl)
landing approach speed
All specifications are based on manufacturer's
Landing gear Fixed conventional or trigear, or retractable