Golden Era 60 Bipe - 2009/02

Left: This model’s looks are reminiscent of
the Payne Knight Twister published in the
1938 Air Trails. It has the look of a
Schneider Cup racer as well, and the
groovy performance.
Two wings are as
much fun as one—
this model
offers a choice
WHILE ON A Sunday drive with my parents
in 1938, I bought my first model aviation
magazine. We had stopped at a variety store
for ice cream, as was usual on these outings,
and I browsed the magazine rack while we
waited for our order.
A picture inside Air Trails magazine
caught my eye; I begged my mother for the
15¢ to buy the periodical, and she relented.
The object of my interest was the tiny Knight
Twister biplane that was powered by a Ford
Model A engine, modified for air-cooling.
The airplane was Vernon Payne’s landmark
home-built of the prewar period.
It was love at first sight for a 5-year-old
aviation nut, and the little airplane carved a
permanent niche in the back of my mind. The
magazine also ignited an interest in aircraft
modeling that has stayed with me for almost
70 years. I kept the magazine until I married
in 1956 and moved out of the house in which
I was born. I wish I still had it.
Flight photos by Mark Lanterman Construction photos by the author Static photos by Michael Ramsey
02sig1.QXD 12/22/08 1:11 PM Page 18
Type: RC sport
Skill level: Intermediate builder and pilot
Wingspan: Upper, 55.375 inches; lower, 49.375 inches
Wing area: Upper, 540 square inches; lower, 425 square inches
Length: 51 inches
Weight: 10 pounds
Wing loading: 24 ounces/square foot
Engine: .60-.91 two-stroke, .91-1.20 two-stroke
Construction: Balsa, light plywood (Laser-cut short kit is available.)
Finish: Film covering (Sig AeroKote was used) and matching paint
Radio: Four channels minimum, three ball-bearing standard servos, two lowprofile
aileron servos
Other: 3-inch
spinner, 3-inch main
wheels, 14-ounce fuel
tank, 1/6-scale pilot
bust, Sig 4-Star 120
aluminum landing
gear and wheel pants
While committing the Golden Era 60 (my
model design in the May 2008 MA) to CAD, I
made a few pencil sketches of how it would
look as a biplane. The similarity between it
and the Bearcat-engine-version of the Knight
Twister cannot be coincidental.
Since I had built a second fuselage and
empennage for the magazine pictures,
building a biplane conversion was a foregone
conclusion. ModelCAD 3000 was my weapon
of choice, and the pattern files were at
Creative Hobbies for laser cutting within a
week.
This build is typical for any modeler who
has discovered the joys (and frustrations) of
scratch building. The only unusual materials
are a few pieces of inexpensive, light, and
very strong composite tubing from
Kitebuilder.com.
Creative Hobbies sells a laser-cut kit of all
fabricated parts for the Golden Era 60
monoplane; only the biplane conversion kit;
or the fuselage, empennage, and bipe wing kit.
You can purchase the plans from the AMA
Plans Service.
A great fiberglass cowl is available from
Fiberglass Specialties. National Balsa or Balsa
USA can supply your balsa and plywood
needs. If you have already built the
monoplane version, you’ll need only the
biplane plans set.
This project’s mission was to create a
simple sport flier with no 3-D aspirations. I
equipped it with standard ball-bearing servos.
However, the control surfaces are more than
adequate for spirited aerobatics, and I have no
doubt that, with better servos and long throws,
the bipe would give a good aerobatic account
of itself at anybody’s club field.
This build is predicated on the concept of
using one fuselage and tail section as a basis
for two aircraft: a monoplane and a biplane. I
designed the monoplane first, and I didn’t
want to extensively modify the fuselage to
convert the Golden Era 60 to a biplane.
That decision led to the use of an adapter,
which allows the narrower biplane lower wing
to fit into the monoplane’s wing recess. The
adapter is also responsible for the wing-saddle
setup for the upper wing mount. The Golden
Era 60 is convertible with no readily
observable compromises.
This article will cover only those
assemblies and procedures necessary to
convert the Golden Era 60 to a biplane and
back to a monoplane. Field conversion should
take only minutes. Simply head to the field,
choose your set of wings, and fly.
If you are interested only in the biplane,
feel free to redesign the wing mountings,
struts, etc. One of the neat things about scratch
building is the option of doing it your way. If
you do, I’d love to see the result.
CONSTRUCTION
As with all scratch builds, it is best to have
all components fabricated and ready for
assembly. You should also have a completed
fuselage available for parts fitting.
I took great care, when making the
drawings, to ensure that the holes for pegs,
spars, wing LE, etc. are accurate within 1/32
inch. But the process of duplicating prints can
create small errors. It is the builder’s
responsibility to ensure that all critical drilled
holes are accurate for size and location.
When using the short kit, you’ll need to
scuff the burned area where cement, either
epoxy or cyanoacrylate, is being applied.
Adhesives bond poorly to a charred surface.
It’s unnecessary to remove all traces of
brown; sand enough to get loose surface scale
off. Don’t remove so much material that the
parts fit is impaired. Using the preceding tips,
I have not had a glue joint fail using the lasercut
parts.
In the remainder of the article, unless
otherwise noted, “cyanoacrylate” will mean
the medium adhesive and “epoxy” will mean
the 30-minute variety.
Adapter: This tool for the lower wing adapter
provides a means to mount the narrower lower
wings into the existing Golden Era 60 wing
recess. The adapter is an uncomplicated
structure consisting mainly of a few pieces of
1/4 plywood, scrap balsa, and basswood spar
material.
The adapter’s fit is critical to the angle of
incidence and the alignment of both the upper
and lower wings. If the finished assembly
can’t be made to comply with any of the
conditions in the following paragraphs, it’s
best to start over.
Epoxy is used for adapter construction.
Employ a lower wing rib as a pattern, and
ensure that the forward peg hole and the spar
holes in the adapter sides are coincident with
the corresponding holes in the wing rib. In
addition, ensure that the pegs in the adapter
front will line up with the holes in the
fuselage F1 assembly.
Using the adapter diagram on the print as
a guide, epoxy and clamp together the
adapter sides, front, and back. Make sure
that the assembly is square.
Install the wing mounting plate in the
slot provided. It should be flush with the
bottom of the assembly. Epoxy the 1/4-inch
pegs into the front of the adapter; they
should protrude approximately 3/8 inch and
have a slight chamfer at the exposed ends.
Cut the 1/4-inch LE positioning dowel to
extend past the adapter by 1 inch on either
side. Do not add epoxy at this time.
Check the assembly’s fit. The pegs
should engage the holes in fuselage former
F1, and the adapter sides should fit snugly
against the wing recess in the fuselage
sides. If the fore/aft fit is too tight, remove
some material from the rear of the adapter.
With the adapter temporarily installed
in the fuselage, insert the composite spar
through the opening in the adapter. Use a
large square to ensure that the spar extends
at right angles to the fuselage sides.
When the fit is satisfactory, install the
1/8-inch square adapter bottom support,
following the contour and recessed 3/32
inch. Mount the 3/32 balsa bottom. It should
be flush with the bottom of the adapter. I
used a 1/8 x 1/4 basswood crosspiece to help
support the balsa. The accompanying
pictures should clarify things.
Lower Wings: The lower wing panels are
identical as assembled over the plans. Protect
the plans with waxed paper, since both the left
and right lower sections will be constructed
over them.
Cut a piece of 1/8 x 1/4 basswood for use as
a bottom middle spar, and secure it in place
on the plans. It will be used as a guide to
ensure proper rib placement.
The lower ribs are the same. Using
cyanoacrylate and a small square, cement
them in place at their stations on the plans.
The break-off tabs should be flush against the
building board.
When the cyanoacrylate has set, install the
two 1/8 x 14-inch top spars and the 1/8-inch
square spar at the top rear. Cut a piece of .317
composite tubing to length, and use
cyanoacrylate to adhere it in place at the wing
LE. Its ends should be flush with the outside
surface of the center and end ribs.
Remove the wing from the plans and
install the remaining spars. Cut a length of 3/8
square balsa TE to size, and shape it as the
plans show. A razor plane and sanding block
will make short work of this task. Make a TE
for the left wing and set it aside.
Before performing the next steps, note that
the two inboard ribs on the lower wings are
spaced closer than those remaining. Don’t
make the mistake of attaching the wingtip to
the wrong end of the wing.
Cyanoacrylate-glue the TE to the wing and
26 MODEL AVIATION
secure the wingtip. Ensure that the wingtip
bisects the wing center and extends
horizontally, at right angles to the ribs. Cut
and install the spar extensions, beveling the
ends for a flush fit against the wingtip.
Snap off the rib stubs, and then sand the
area smooth. The wing should be symmetrical,
with no top or bottom. Decide whether it will
be a right or a left wing; mark it in several
places with your choice.
The false ribs used for the I-strut adapters
need to be installed. Using a scrap piece of 1/8
plywood as a temporary spacer to establish a
slot and cyanoacrylate-glue them in as
indicated on the plans.
Repeat the previous wing-building
instructions to construct the opposite wing.
The only difference will be when you mount
the servo plates and the interplane strut
mounts. Be careful; you cannot imagine how
easy it is to find yourself with two right or two
left wings.
Cut stiffeners of scrap spar material for the
servo plates, as shown on the plans diagram,
and adhere them in place with cyanoacrylate.
The side rails provide a gluing surface for
attaching the plate to the ribs, and the
transverse pieces provide a secure seat for the
servo mounting screws.
Test-position the servo plates on the
bottom of the wings. Make sure they don’t
interfere with insertion of the main spar. When
satisfied with the fit, epoxy the servo plates in
place as flush as possible with the bottom of
the ribs.
Because of the thin wing, it’s necessary to
use low-profile servos. I recommend the Blue
Bird BMS-706. For roughly a $20 street price,
you get dual ball bearings and 65 ounce-inch
of torque. Standard servos almost fit, but who
needs a lump in the wing covering?
At this point, insert a .505 main spar
through the adapter and into the wings. Make
sure that the LE positioning dowel engages the
.317 composite tubing. If it does not, reshape
the peg hole in the adapter fore or aft for a
proper fit. The vertical position must remain
unchanged. When satisfied, cyanoacrylateglue
the dowel only to the adapter.
The lower wings will not be permanently
mounted to the adapter until they are planked.
The strut adapters have been added and the
wings have been covered.
Shape the ailerons. Using the plans as a
pattern, cut the 3/8 x 2-inch tapered stock to a
shape that conforms to the wing TE. Install
hinges after you have applied the planking.
Upper Wings: Remove the lower-wing plans
from the building board, and secure the upperwing
plans in its place. The procedure for
building the upper wings is identical to the
procedure for building the lower, less the
servo mount.
After removing the wing halves from the
plans, decide whether or not you want hinged
ailerons on the upper wings, as are on the
lower. It is also time to cyanoacrylate-glue a
1/4 x 6-inch dowel into one LE at the wing
root. Allow 3 inches to protrude from the LE.
The dowel will slide into the opposite wing’s
LE as an alignment aid when they are joined.
There is generous aileron area on the
lower wing for general sport-flying, but I
chose to employ working ailerons on both
wings. I initially had the ailerons fixed to the
upper wings, as shown in the photo(s), but I
cut the upper ailerons free before covering.
This decision was prompted by discussions
with friends and, notably, a suggestion from a
certain magazine editor.
I have used a simple method to link the
upper and lower ailerons. The link is
positioned directly behind the aileron servo
for positive operation. Many biplanes’ slave
links are behind the interplane struts;
however, because of the I-struts’ outboard
location, that wasn’t a prudent solution with
this model.
Follow the plans for aileron shaping and
cutting. If the upper ailerons are going to be
fixed, you can adhere them to the TE with
cyanoacrylate after planking. Otherwise, cut
the ailerons as the plans indicate and shape the
LE for hinging.
This decision is reversible. The fixed
ailerons on the upper wings can easily be cut
free and hinged.
Wing Planking: The upper wings need 1/16 x
6 x 24 balsa for LE planking; the lower wings
require 1/16 x 5 x 24 balsa. If you are gluing
two pieces to get the width, use a 2- and a 4-
inch (or 3-inch) sheet to prevent the sharpest
bend from being at the glue joint.
Spray Windex generously to make the
balsa pliant enough to bend around the LE’s
tight radius. After it soaks for several minutes,
you should have no trouble making the bend.
The remaining planking is effortless. And
except for the wingtip LE, no further soaking
should be necessary. Capstrips are used on
both wings. I like the appearance, and they
add little weight. I also planked the entire
wingtips. (Doing so or not is the builder’s
choice.)
After planking is complete, use a few
small spots of planking cyanoacrylate to
temporarily attach the ailerons to both sets of
wings. Shape the ailerons to blend with the
wing TEs. After shaping, use cyanoacrylate
debonder or a hobby knife to remove the
ailerons.
This is a good time to cut aileron hinge
slots. I chose leaf hinges rather than the
typical cyanoacrylate type. I used four on each
side, spaced to avoid the ribs.
When you have completed the upper wing
halves except for covering, join them.
Install—but do not epoxy—the .505 spar. It
must be free to slide past the root rib, to the
wing saddle that will be inserted later. Use
the peg in one LE and the composite spar for
alignment, and epoxy and clamp the wing
halves together.
Upper Wing Saddle: Since making as few
modifications as possible to the original
fuselage was a priority, I had a problem. I
pondered how to attach the upper wing for far
longer than I care to admit. I was concerned
that a balsa-and-light plywood, “N”-style
cabane-strut system might not be strong
enough, and I didn’t want to resort to
aluminum; I’m not much of a metalworker.
The answer came to me as I worked on my
ham radio tower. I had some large UV-proof
tie-wraps I used to attach a heavy switchbox
to one of the tower legs. The old Knight
Twister had a pylon between the upper wing
and the fuselage; it would be simple to attach
the wings using a pylon or wing saddle and
these heavy-duty straps. Better still, it would
require only four small holes in the fuselage to
hold the straps in place.
The drawings on the plans show parts
outlines and materials for the wing saddle. It
is attached permanently to the upper wing and
uses two sections of industrial-strength nylon
tie-wrap to secure the saddle to the fuselage
using nylon bolts.
The tie-wraps are inexpensive and
extremely strong. I used the black Leco
Plastics L-48-175 wraps, which have a 175-
pound tensile (pull) strength. Although holes
have to be drilled in the ends, these tie-wraps
are good for the job. They are available at any
good hardware or construction-equipment
store.
The wing saddle is built up using several
pieces of balsa and plywood. Some shaping
and carving is necessary but shouldn’t present
a problem to an experienced builder. The
rectangular holes in the plywood are best
made by drilling the ends and then using a
Dremel or scroll saw to cut away the material
between the drilled holes.
The bipe-conversion short kit includes
laser-cut plywood saddle parts. Furnished are
one 1/4 plywood piece for the core of the
assembly and two 1/8 plywood outer pieces
with blades that go into the upper wing and
engage the spar. The two 3/8 balsa finish
pieces are left to the builder to fabricate.
The balsa parts have a channel for the
straps that terminates in a rectangular opening
at the lower, outside edge. The easiest way to
make the balsa parts is to shape the outline
and then cut notches in the bottom. Use a
rotary tool to rout out the inside to allow for
passage of the straps.
Align the five pieces and clamp them
together. The top of all four pieces should be
flush. The holes in the two outer plywood
parts are slightly larger and lower, to allow for
the curve in the retaining straps.
While the parts are clamped together, testfit
a length of strap. The tie-wraps are snaked
through the rectangular slots in the saddle
assembly. These should be able to pass
through the wing saddle and slide freely. Use
pliers to curve the end of the strap; that should
make it easier to fish through the wing saddle.
When satisfied with the fit, remove the
straps and epoxy all five parts together,
clamping them until set. Ensure that the
strap holes remain clear. Use a file or a
rotary tool to contour the bottom to closely
match the curve of the fuselage, and then
round the front and rear.
Finish the entire saddle per your taste.
Then insert the straps, leaving roughly 6
inches extending on either side of the
saddle, front and rear.
Make the holes in the fuselage for the #8
bolt hardware. The holes should be large
enough for the 8-32 captive nuts to be
epoxied inside the fuselage.
The front mounting holes in the fuselage
should be just aft of former F1 and 1/4 inch
below the junction of the curved top and the
fuselage sides. The rear set of holes is 51/2
inches farther aft. (See the assembly diagram.)
Carefully center the wing saddle, hold it in
place with masking tape, and mark and drill
the straps for 8-32 nylon screws. It’s a good
idea to mark center with a bit of striping tape
as a permanent alignment aid.
Be careful to ensure that the straps will
hold the saddle tightly against the fuselage.
The tie-wraps will not stretch, so the position
of the holes is critical.
Glue a felt pad to the bottom of the saddle,
to prevent damage to the fuselage. Install the
pad after drilling the holes. It will take up any
slack in the straps and ensure a tight fit. Use a
couple layers of felt if necessary.
Cut 1/8-inch slots in the planking on the
bottom of the upper wing for the wing-saddle
blades. Cover the area with a 4-inch strip of
film, to eliminate the need for meticulous
trimming around the wing saddle when
covering the wings. Remove the film from the
area of the slots.
Slide the composite main spar all the way
to one wingtip, and then apply epoxy to the
inside of the blades extending from the wing
saddle. Use a couple strips of masking tape
applied to the wing bottom to prevent the
epoxy from migrating.
Insert the blades into the slots,
sandwiching the root ribs. Seat the wing
saddle snug against the wing and center the
composite spar, sliding it through the holes in
the blades.
Apply epoxy to the spar at several rib
intersections, securing it permanently. Put
some weight on the bottom of the saddle to
hold it firmly against the wing, and set it aside
to cure.
Interplane Struts: These consist of six
separate pieces: four fixed adapters that are
fabricated and epoxied to the upper and lower
wings after covering and two struts that are
permanently hinged to the top wing adapters
using Sig Giant Scale hinges. (See the
assembly drawing for clarification.)
The upper and lower wing I-strut adapters
are made from 1/8 plywood. Assemble them
according to the plans, sand them smooth, and
check for fit in the appropriate slots.
The interplane struts are made from 1/8
light plywood and 1/8 balsa. Use the plans
pattern to make two pieces of each material. It
is important to have the balsa lamination
inboard on each side.
Adhere the parts with cyanoacrylate, and
then sand the edges to a rounded contour.
Finish the struts and adapters with fuelproof
paint.
Using the assembly drawing as a guide,
epoxy hinges in the fixed upper adapter and
February 2009 31
the I-struts. You can fill the recesses in the Istruts
with balsa filler after hinging, or you
can make a skirt to conceal the hinge
mechanism. In any case, be sure that the
hinges can move a few degrees in the
direction they need to go, and don’t forget to
peg the hinge stubs recessed in the I-struts.
The free part of the hinges on the bottom
of the I-struts extend into the fixed lower strut
adapter during field assembly, and two 3-48 x
1/2-inch button-head screws secure them in
place on each side.
With the wings covered, cut the strutadapter
slots in both wings. The upper adapter
should have the I-struts permanently installed.
Make sure that the hinges are free enough to
let the struts fold inboard, flat against the
wing, for storage and transportation.
Use epoxy to install the strut adapters in
the lower wing. Ensure that they’re properly
oriented. This completes the building portion
of the Golden Era 60 biplane conversion.
An assembly diagram is included on these
pages, and no further explanation should be
necessary. I sent the original bipe to AMA
Headquarters for testing. Following is MA
Editor Michael Ramsey’s review.
Flying: Ground-handling the Golden Era 60
biplane is similar to driving a motor home;
just set the cruise control and go make a
sandwich in the galley. It’s that assuring and
easy.
The long tail moment and wide landing
gear do everything to keep the taxi stuff
friendly. Even the high-speed run before
liftoff requires little or nothing to be done
with the rudder. When this model rolls down
the runway at a speed where it looks like it
should fly, haul back on the elevator and up it
goes, straight and true.
The GMS .61 engine, which this airframe
is built around, is a nice sport power plant for
such a model. It’s reminiscent of the “old
school” power philosophy; the airplane flies
on the wing and not on the propeller.
As noted during testing, the Golden Era
can handle, and in some cases deserves, the
power a .91 two-stroke or four-stroke engine
could give it. If that’s what you have in your
engine drawer, by all means put it in.
With its 900 square inches of wing area,
this model can cruise around comfortably at
65% power. Coordinating the turns is
unnecessary when the speed is kept up, but in
the wind it likes slight rudder mixed in the
same direction as the aileron input. Elevator
in the turns, whether they’re inside or outside,
can crank the bipe around as tightly as the
pilot wants, given that the power in the
engine is willing.
The rudder is ghastly effective, which,
given its size ratio comparison with the rest of
the surfaces, was a huge yet pleasant surprise.
I set the high rate travel to maximum
deflection and found it to be extremely
touchy for normal flight but the heart of the
tumbling trickery that this model has in its
bag of magic.
For the most part, 50% throw in the
rudder plus approximately 30% exponential
was a decent setup. That way, the stall turns
can be done in a tight half circle.
A large amount of rudder input can tuck
the nose toward the landing gear, so watch
during landing if heading corrections are
required. In knife-edge flight, the rudder
corrections want to naturally roll the model
back to level flight, and it’s already pushing
away from the canopy. For the most part, the
pilot can hold these corrections in for a
wicked-cool knife-edge pass down on the
deck, but a P-mix or two into the rudder will
fix the habit completely.
The twin ailerons are a delight; both
wings work together, rather than one wing
with ailerons having to overcome the drag of
the other. Little deflection is needed for
normal flying, and the ailerons’ movement
requires no differential mixing because their
travel is minimal.
Point rolls are possible that we can relate
to the crispness we see at air shows with the
Pitts biplanes. That includes the “wow”
factor.
Landing the Golden Era bipe is almost
easier than landing a trainer. Because it flies
where the pilot points it, bringing the model
home is a matter of “X” marks the spot. With
a throttle setting of roughly 50%, this airplane
sets itself into a natural glide slope; all the
pilot needs to do is gently pull on the upelevator
before touchdown and ease the
throttle back to idle.
Make the Golden Era biplane your
everyday flier. I’ve tested it in calm and
hurricanelike conditions, and I was
phenomenally impressed by how solidly it
performed.
Thanks for the airplane, Fred. I’m having
a blast! MA
Fred Randall
[email protected]
Sources:
Payne Knight Twister information, full-size
home-built plans:
www.steenaero.com
Creative Hobbies
(508) 473-8259
www.creativehobbies.net
Composite tubing:
Kite Studio
(800) KITE-991
www.kitebuilder.com/catalog/index.php
AMA Plans Service
(800) 435-9262, ext. 507
www.modelaircraft.org/plans.aspx
Fiberglass Specialties
(479) 359-2259
www.fiberglassspecialtiesinc.com
National Balsa Co.
(413) 277-9500
www.nationalbalsa.com
Balsa USA
(800) 225-7287
www.balsausa.com

Left: This model’s looks are reminiscent of
the Payne Knight Twister published in the
1938 Air Trails. It has the look of a
Schneider Cup racer as well, and the
groovy performance.
Two wings are as
much fun as one—
this model
offers a choice
WHILE ON A Sunday drive with my parents
in 1938, I bought my first model aviation
magazine. We had stopped at a variety store
for ice cream, as was usual on these outings,
and I browsed the magazine rack while we
waited for our order.
A picture inside Air Trails magazine
caught my eye; I begged my mother for the
15¢ to buy the periodical, and she relented.
The object of my interest was the tiny Knight
Twister biplane that was powered by a Ford
Model A engine, modified for air-cooling.
The airplane was Vernon Payne’s landmark
home-built of the prewar period.
It was love at first sight for a 5-year-old
aviation nut, and the little airplane carved a
permanent niche in the back of my mind. The
magazine also ignited an interest in aircraft
modeling that has stayed with me for almost
70 years. I kept the magazine until I married
in 1956 and moved out of the house in which
I was born. I wish I still had it.
Flight photos by Mark Lanterman Construction photos by the author Static photos by Michael Ramsey
02sig1.QXD 12/22/08 1:11 PM Page 18
Type: RC sport
Skill level: Intermediate builder and pilot
Wingspan: Upper, 55.375 inches; lower, 49.375 inches
Wing area: Upper, 540 square inches; lower, 425 square inches
Length: 51 inches
Weight: 10 pounds
Wing loading: 24 ounces/square foot
Engine: .60-.91 two-stroke, .91-1.20 two-stroke
Construction: Balsa, light plywood (Laser-cut short kit is available.)
Finish: Film covering (Sig AeroKote was used) and matching paint
Radio: Four channels minimum, three ball-bearing standard servos, two lowprofile
aileron servos
Other: 3-inch
spinner, 3-inch main
wheels, 14-ounce fuel
tank, 1/6-scale pilot
bust, Sig 4-Star 120
aluminum landing
gear and wheel pants
While committing the Golden Era 60 (my
model design in the May 2008 MA) to CAD, I
made a few pencil sketches of how it would
look as a biplane. The similarity between it
and the Bearcat-engine-version of the Knight
Twister cannot be coincidental.
Since I had built a second fuselage and
empennage for the magazine pictures,
building a biplane conversion was a foregone
conclusion. ModelCAD 3000 was my weapon
of choice, and the pattern files were at
Creative Hobbies for laser cutting within a
week.
This build is typical for any modeler who
has discovered the joys (and frustrations) of
scratch building. The only unusual materials
are a few pieces of inexpensive, light, and
very strong composite tubing from
Kitebuilder.com.
Creative Hobbies sells a laser-cut kit of all
fabricated parts for the Golden Era 60
monoplane; only the biplane conversion kit;
or the fuselage, empennage, and bipe wing kit.
You can purchase the plans from the AMA
Plans Service.
A great fiberglass cowl is available from
Fiberglass Specialties. National Balsa or Balsa
USA can supply your balsa and plywood
needs. If you have already built the
monoplane version, you’ll need only the
biplane plans set.
This project’s mission was to create a
simple sport flier with no 3-D aspirations. I
equipped it with standard ball-bearing servos.
However, the control surfaces are more than
adequate for spirited aerobatics, and I have no
doubt that, with better servos and long throws,
the bipe would give a good aerobatic account
of itself at anybody’s club field.
This build is predicated on the concept of
using one fuselage and tail section as a basis
for two aircraft: a monoplane and a biplane. I
designed the monoplane first, and I didn’t
want to extensively modify the fuselage to
convert the Golden Era 60 to a biplane.
That decision led to the use of an adapter,
which allows the narrower biplane lower wing
to fit into the monoplane’s wing recess. The
adapter is also responsible for the wing-saddle
setup for the upper wing mount. The Golden
Era 60 is convertible with no readily
observable compromises.
This article will cover only those
assemblies and procedures necessary to
convert the Golden Era 60 to a biplane and
back to a monoplane. Field conversion should
take only minutes. Simply head to the field,
choose your set of wings, and fly.
If you are interested only in the biplane,
feel free to redesign the wing mountings,
struts, etc. One of the neat things about scratch
building is the option of doing it your way. If
you do, I’d love to see the result.
CONSTRUCTION
As with all scratch builds, it is best to have
all components fabricated and ready for
assembly. You should also have a completed
fuselage available for parts fitting.
I took great care, when making the
drawings, to ensure that the holes for pegs,
spars, wing LE, etc. are accurate within 1/32
inch. But the process of duplicating prints can
create small errors. It is the builder’s
responsibility to ensure that all critical drilled
holes are accurate for size and location.
When using the short kit, you’ll need to
scuff the burned area where cement, either
epoxy or cyanoacrylate, is being applied.
Adhesives bond poorly to a charred surface.
It’s unnecessary to remove all traces of
brown; sand enough to get loose surface scale
off. Don’t remove so much material that the
parts fit is impaired. Using the preceding tips,
I have not had a glue joint fail using the lasercut
parts.
In the remainder of the article, unless
otherwise noted, “cyanoacrylate” will mean
the medium adhesive and “epoxy” will mean
the 30-minute variety.
Adapter: This tool for the lower wing adapter
provides a means to mount the narrower lower
wings into the existing Golden Era 60 wing
recess. The adapter is an uncomplicated
structure consisting mainly of a few pieces of
1/4 plywood, scrap balsa, and basswood spar
material.
The adapter’s fit is critical to the angle of
incidence and the alignment of both the upper
and lower wings. If the finished assembly
can’t be made to comply with any of the
conditions in the following paragraphs, it’s
best to start over.
Epoxy is used for adapter construction.
Employ a lower wing rib as a pattern, and
ensure that the forward peg hole and the spar
holes in the adapter sides are coincident with
the corresponding holes in the wing rib. In
addition, ensure that the pegs in the adapter
front will line up with the holes in the
fuselage F1 assembly.
Using the adapter diagram on the print as
a guide, epoxy and clamp together the
adapter sides, front, and back. Make sure
that the assembly is square.
Install the wing mounting plate in the
slot provided. It should be flush with the
bottom of the assembly. Epoxy the 1/4-inch
pegs into the front of the adapter; they
should protrude approximately 3/8 inch and
have a slight chamfer at the exposed ends.
Cut the 1/4-inch LE positioning dowel to
extend past the adapter by 1 inch on either
side. Do not add epoxy at this time.
Check the assembly’s fit. The pegs
should engage the holes in fuselage former
F1, and the adapter sides should fit snugly
against the wing recess in the fuselage
sides. If the fore/aft fit is too tight, remove
some material from the rear of the adapter.
With the adapter temporarily installed
in the fuselage, insert the composite spar
through the opening in the adapter. Use a
large square to ensure that the spar extends
at right angles to the fuselage sides.
When the fit is satisfactory, install the
1/8-inch square adapter bottom support,
following the contour and recessed 3/32
inch. Mount the 3/32 balsa bottom. It should
be flush with the bottom of the adapter. I
used a 1/8 x 1/4 basswood crosspiece to help
support the balsa. The accompanying
pictures should clarify things.
Lower Wings: The lower wing panels are
identical as assembled over the plans. Protect
the plans with waxed paper, since both the left
and right lower sections will be constructed
over them.
Cut a piece of 1/8 x 1/4 basswood for use as
a bottom middle spar, and secure it in place
on the plans. It will be used as a guide to
ensure proper rib placement.
The lower ribs are the same. Using
cyanoacrylate and a small square, cement
them in place at their stations on the plans.
The break-off tabs should be flush against the
building board.
When the cyanoacrylate has set, install the
two 1/8 x 14-inch top spars and the 1/8-inch
square spar at the top rear. Cut a piece of .317
composite tubing to length, and use
cyanoacrylate to adhere it in place at the wing
LE. Its ends should be flush with the outside
surface of the center and end ribs.
Remove the wing from the plans and
install the remaining spars. Cut a length of 3/8
square balsa TE to size, and shape it as the
plans show. A razor plane and sanding block
will make short work of this task. Make a TE
for the left wing and set it aside.
Before performing the next steps, note that
the two inboard ribs on the lower wings are
spaced closer than those remaining. Don’t
make the mistake of attaching the wingtip to
the wrong end of the wing.
Cyanoacrylate-glue the TE to the wing and
26 MODEL AVIATION
secure the wingtip. Ensure that the wingtip
bisects the wing center and extends
horizontally, at right angles to the ribs. Cut
and install the spar extensions, beveling the
ends for a flush fit against the wingtip.
Snap off the rib stubs, and then sand the
area smooth. The wing should be symmetrical,
with no top or bottom. Decide whether it will
be a right or a left wing; mark it in several
places with your choice.
The false ribs used for the I-strut adapters
need to be installed. Using a scrap piece of 1/8
plywood as a temporary spacer to establish a
slot and cyanoacrylate-glue them in as
indicated on the plans.
Repeat the previous wing-building
instructions to construct the opposite wing.
The only difference will be when you mount
the servo plates and the interplane strut
mounts. Be careful; you cannot imagine how
easy it is to find yourself with two right or two
left wings.
Cut stiffeners of scrap spar material for the
servo plates, as shown on the plans diagram,
and adhere them in place with cyanoacrylate.
The side rails provide a gluing surface for
attaching the plate to the ribs, and the
transverse pieces provide a secure seat for the
servo mounting screws.
Test-position the servo plates on the
bottom of the wings. Make sure they don’t
interfere with insertion of the main spar. When
satisfied with the fit, epoxy the servo plates in
place as flush as possible with the bottom of
the ribs.
Because of the thin wing, it’s necessary to
use low-profile servos. I recommend the Blue
Bird BMS-706. For roughly a $20 street price,
you get dual ball bearings and 65 ounce-inch
of torque. Standard servos almost fit, but who
needs a lump in the wing covering?
At this point, insert a .505 main spar
through the adapter and into the wings. Make
sure that the LE positioning dowel engages the
.317 composite tubing. If it does not, reshape
the peg hole in the adapter fore or aft for a
proper fit. The vertical position must remain
unchanged. When satisfied, cyanoacrylateglue
the dowel only to the adapter.
The lower wings will not be permanently
mounted to the adapter until they are planked.
The strut adapters have been added and the
wings have been covered.
Shape the ailerons. Using the plans as a
pattern, cut the 3/8 x 2-inch tapered stock to a
shape that conforms to the wing TE. Install
hinges after you have applied the planking.
Upper Wings: Remove the lower-wing plans
from the building board, and secure the upperwing
plans in its place. The procedure for
building the upper wings is identical to the
procedure for building the lower, less the
servo mount.
After removing the wing halves from the
plans, decide whether or not you want hinged
ailerons on the upper wings, as are on the
lower. It is also time to cyanoacrylate-glue a
1/4 x 6-inch dowel into one LE at the wing
root. Allow 3 inches to protrude from the LE.
The dowel will slide into the opposite wing’s
LE as an alignment aid when they are joined.
There is generous aileron area on the
lower wing for general sport-flying, but I
chose to employ working ailerons on both
wings. I initially had the ailerons fixed to the
upper wings, as shown in the photo(s), but I
cut the upper ailerons free before covering.
This decision was prompted by discussions
with friends and, notably, a suggestion from a
certain magazine editor.
I have used a simple method to link the
upper and lower ailerons. The link is
positioned directly behind the aileron servo
for positive operation. Many biplanes’ slave
links are behind the interplane struts;
however, because of the I-struts’ outboard
location, that wasn’t a prudent solution with
this model.
Follow the plans for aileron shaping and
cutting. If the upper ailerons are going to be
fixed, you can adhere them to the TE with
cyanoacrylate after planking. Otherwise, cut
the ailerons as the plans indicate and shape the
LE for hinging.
This decision is reversible. The fixed
ailerons on the upper wings can easily be cut
free and hinged.
Wing Planking: The upper wings need 1/16 x
6 x 24 balsa for LE planking; the lower wings
require 1/16 x 5 x 24 balsa. If you are gluing
two pieces to get the width, use a 2- and a 4-
inch (or 3-inch) sheet to prevent the sharpest
bend from being at the glue joint.
Spray Windex generously to make the
balsa pliant enough to bend around the LE’s
tight radius. After it soaks for several minutes,
you should have no trouble making the bend.
The remaining planking is effortless. And
except for the wingtip LE, no further soaking
should be necessary. Capstrips are used on
both wings. I like the appearance, and they
add little weight. I also planked the entire
wingtips. (Doing so or not is the builder’s
choice.)
After planking is complete, use a few
small spots of planking cyanoacrylate to
temporarily attach the ailerons to both sets of
wings. Shape the ailerons to blend with the
wing TEs. After shaping, use cyanoacrylate
debonder or a hobby knife to remove the
ailerons.
This is a good time to cut aileron hinge
slots. I chose leaf hinges rather than the
typical cyanoacrylate type. I used four on each
side, spaced to avoid the ribs.
When you have completed the upper wing
halves except for covering, join them.
Install—but do not epoxy—the .505 spar. It
must be free to slide past the root rib, to the
wing saddle that will be inserted later. Use
the peg in one LE and the composite spar for
alignment, and epoxy and clamp the wing
halves together.
Upper Wing Saddle: Since making as few
modifications as possible to the original
fuselage was a priority, I had a problem. I
pondered how to attach the upper wing for far
longer than I care to admit. I was concerned
that a balsa-and-light plywood, “N”-style
cabane-strut system might not be strong
enough, and I didn’t want to resort to
aluminum; I’m not much of a metalworker.
The answer came to me as I worked on my
ham radio tower. I had some large UV-proof
tie-wraps I used to attach a heavy switchbox
to one of the tower legs. The old Knight
Twister had a pylon between the upper wing
and the fuselage; it would be simple to attach
the wings using a pylon or wing saddle and
these heavy-duty straps. Better still, it would
require only four small holes in the fuselage to
hold the straps in place.
The drawings on the plans show parts
outlines and materials for the wing saddle. It
is attached permanently to the upper wing and
uses two sections of industrial-strength nylon
tie-wrap to secure the saddle to the fuselage
using nylon bolts.
The tie-wraps are inexpensive and
extremely strong. I used the black Leco
Plastics L-48-175 wraps, which have a 175-
pound tensile (pull) strength. Although holes
have to be drilled in the ends, these tie-wraps
are good for the job. They are available at any
good hardware or construction-equipment
store.
The wing saddle is built up using several
pieces of balsa and plywood. Some shaping
and carving is necessary but shouldn’t present
a problem to an experienced builder. The
rectangular holes in the plywood are best
made by drilling the ends and then using a
Dremel or scroll saw to cut away the material
between the drilled holes.
The bipe-conversion short kit includes
laser-cut plywood saddle parts. Furnished are
one 1/4 plywood piece for the core of the
assembly and two 1/8 plywood outer pieces
with blades that go into the upper wing and
engage the spar. The two 3/8 balsa finish
pieces are left to the builder to fabricate.
The balsa parts have a channel for the
straps that terminates in a rectangular opening
at the lower, outside edge. The easiest way to
make the balsa parts is to shape the outline
and then cut notches in the bottom. Use a
rotary tool to rout out the inside to allow for
passage of the straps.
Align the five pieces and clamp them
together. The top of all four pieces should be
flush. The holes in the two outer plywood
parts are slightly larger and lower, to allow for
the curve in the retaining straps.
While the parts are clamped together, testfit
a length of strap. The tie-wraps are snaked
through the rectangular slots in the saddle
assembly. These should be able to pass
through the wing saddle and slide freely. Use
pliers to curve the end of the strap; that should
make it easier to fish through the wing saddle.
When satisfied with the fit, remove the
straps and epoxy all five parts together,
clamping them until set. Ensure that the
strap holes remain clear. Use a file or a
rotary tool to contour the bottom to closely
match the curve of the fuselage, and then
round the front and rear.
Finish the entire saddle per your taste.
Then insert the straps, leaving roughly 6
inches extending on either side of the
saddle, front and rear.
Make the holes in the fuselage for the #8
bolt hardware. The holes should be large
enough for the 8-32 captive nuts to be
epoxied inside the fuselage.
The front mounting holes in the fuselage
should be just aft of former F1 and 1/4 inch
below the junction of the curved top and the
fuselage sides. The rear set of holes is 51/2
inches farther aft. (See the assembly diagram.)
Carefully center the wing saddle, hold it in
place with masking tape, and mark and drill
the straps for 8-32 nylon screws. It’s a good
idea to mark center with a bit of striping tape
as a permanent alignment aid.
Be careful to ensure that the straps will
hold the saddle tightly against the fuselage.
The tie-wraps will not stretch, so the position
of the holes is critical.
Glue a felt pad to the bottom of the saddle,
to prevent damage to the fuselage. Install the
pad after drilling the holes. It will take up any
slack in the straps and ensure a tight fit. Use a
couple layers of felt if necessary.
Cut 1/8-inch slots in the planking on the
bottom of the upper wing for the wing-saddle
blades. Cover the area with a 4-inch strip of
film, to eliminate the need for meticulous
trimming around the wing saddle when
covering the wings. Remove the film from the
area of the slots.
Slide the composite main spar all the way
to one wingtip, and then apply epoxy to the
inside of the blades extending from the wing
saddle. Use a couple strips of masking tape
applied to the wing bottom to prevent the
epoxy from migrating.
Insert the blades into the slots,
sandwiching the root ribs. Seat the wing
saddle snug against the wing and center the
composite spar, sliding it through the holes in
the blades.
Apply epoxy to the spar at several rib
intersections, securing it permanently. Put
some weight on the bottom of the saddle to
hold it firmly against the wing, and set it aside
to cure.
Interplane Struts: These consist of six
separate pieces: four fixed adapters that are
fabricated and epoxied to the upper and lower
wings after covering and two struts that are
permanently hinged to the top wing adapters
using Sig Giant Scale hinges. (See the
assembly drawing for clarification.)
The upper and lower wing I-strut adapters
are made from 1/8 plywood. Assemble them
according to the plans, sand them smooth, and
check for fit in the appropriate slots.
The interplane struts are made from 1/8
light plywood and 1/8 balsa. Use the plans
pattern to make two pieces of each material. It
is important to have the balsa lamination
inboard on each side.
Adhere the parts with cyanoacrylate, and
then sand the edges to a rounded contour.
Finish the struts and adapters with fuelproof
paint.
Using the assembly drawing as a guide,
epoxy hinges in the fixed upper adapter and
February 2009 31
the I-struts. You can fill the recesses in the Istruts
with balsa filler after hinging, or you
can make a skirt to conceal the hinge
mechanism. In any case, be sure that the
hinges can move a few degrees in the
direction they need to go, and don’t forget to
peg the hinge stubs recessed in the I-struts.
The free part of the hinges on the bottom
of the I-struts extend into the fixed lower strut
adapter during field assembly, and two 3-48 x
1/2-inch button-head screws secure them in
place on each side.
With the wings covered, cut the strutadapter
slots in both wings. The upper adapter
should have the I-struts permanently installed.
Make sure that the hinges are free enough to
let the struts fold inboard, flat against the
wing, for storage and transportation.
Use epoxy to install the strut adapters in
the lower wing. Ensure that they’re properly
oriented. This completes the building portion
of the Golden Era 60 biplane conversion.
An assembly diagram is included on these
pages, and no further explanation should be
necessary. I sent the original bipe to AMA
Headquarters for testing. Following is MA
Editor Michael Ramsey’s review.
Flying: Ground-handling the Golden Era 60
biplane is similar to driving a motor home;
just set the cruise control and go make a
sandwich in the galley. It’s that assuring and
easy.
The long tail moment and wide landing
gear do everything to keep the taxi stuff
friendly. Even the high-speed run before
liftoff requires little or nothing to be done
with the rudder. When this model rolls down
the runway at a speed where it looks like it
should fly, haul back on the elevator and up it
goes, straight and true.
The GMS .61 engine, which this airframe
is built around, is a nice sport power plant for
such a model. It’s reminiscent of the “old
school” power philosophy; the airplane flies
on the wing and not on the propeller.
As noted during testing, the Golden Era
can handle, and in some cases deserves, the
power a .91 two-stroke or four-stroke engine
could give it. If that’s what you have in your
engine drawer, by all means put it in.
With its 900 square inches of wing area,
this model can cruise around comfortably at
65% power. Coordinating the turns is
unnecessary when the speed is kept up, but in
the wind it likes slight rudder mixed in the
same direction as the aileron input. Elevator
in the turns, whether they’re inside or outside,
can crank the bipe around as tightly as the
pilot wants, given that the power in the
engine is willing.
The rudder is ghastly effective, which,
given its size ratio comparison with the rest of
the surfaces, was a huge yet pleasant surprise.
I set the high rate travel to maximum
deflection and found it to be extremely
touchy for normal flight but the heart of the
tumbling trickery that this model has in its
bag of magic.
For the most part, 50% throw in the
rudder plus approximately 30% exponential
was a decent setup. That way, the stall turns
can be done in a tight half circle.
A large amount of rudder input can tuck
the nose toward the landing gear, so watch
during landing if heading corrections are
required. In knife-edge flight, the rudder
corrections want to naturally roll the model
back to level flight, and it’s already pushing
away from the canopy. For the most part, the
pilot can hold these corrections in for a
wicked-cool knife-edge pass down on the
deck, but a P-mix or two into the rudder will
fix the habit completely.
The twin ailerons are a delight; both
wings work together, rather than one wing
with ailerons having to overcome the drag of
the other. Little deflection is needed for
normal flying, and the ailerons’ movement
requires no differential mixing because their
travel is minimal.
Point rolls are possible that we can relate
to the crispness we see at air shows with the
Pitts biplanes. That includes the “wow”
factor.
Landing the Golden Era bipe is almost
easier than landing a trainer. Because it flies
where the pilot points it, bringing the model
home is a matter of “X” marks the spot. With
a throttle setting of roughly 50%, this airplane
sets itself into a natural glide slope; all the
pilot needs to do is gently pull on the upelevator
before touchdown and ease the
throttle back to idle.
Make the Golden Era biplane your
everyday flier. I’ve tested it in calm and
hurricanelike conditions, and I was
phenomenally impressed by how solidly it
performed.
Thanks for the airplane, Fred. I’m having
a blast! MA
Fred Randall
[email protected]
Sources:
Payne Knight Twister information, full-size
home-built plans:
www.steenaero.com
Creative Hobbies
(508) 473-8259
www.creativehobbies.net
Composite tubing:
Kite Studio
(800) KITE-991
www.kitebuilder.com/catalog/index.php
AMA Plans Service
(800) 435-9262, ext. 507
www.modelaircraft.org/plans.aspx
Fiberglass Specialties
(479) 359-2259
www.fiberglassspecialtiesinc.com
National Balsa Co.
(413) 277-9500
www.nationalbalsa.com
Balsa USA
(800) 225-7287
www.balsausa.com

Left: This model’s looks are reminiscent of
the Payne Knight Twister published in the
1938 Air Trails. It has the look of a
Schneider Cup racer as well, and the
groovy performance.
Two wings are as
much fun as one—
this model
offers a choice
WHILE ON A Sunday drive with my parents
in 1938, I bought my first model aviation
magazine. We had stopped at a variety store
for ice cream, as was usual on these outings,
and I browsed the magazine rack while we
waited for our order.
A picture inside Air Trails magazine
caught my eye; I begged my mother for the
15¢ to buy the periodical, and she relented.
The object of my interest was the tiny Knight
Twister biplane that was powered by a Ford
Model A engine, modified for air-cooling.
The airplane was Vernon Payne’s landmark
home-built of the prewar period.
It was love at first sight for a 5-year-old
aviation nut, and the little airplane carved a
permanent niche in the back of my mind. The
magazine also ignited an interest in aircraft
modeling that has stayed with me for almost
70 years. I kept the magazine until I married
in 1956 and moved out of the house in which
I was born. I wish I still had it.
Flight photos by Mark Lanterman Construction photos by the author Static photos by Michael Ramsey
02sig1.QXD 12/22/08 1:11 PM Page 18
Type: RC sport
Skill level: Intermediate builder and pilot
Wingspan: Upper, 55.375 inches; lower, 49.375 inches
Wing area: Upper, 540 square inches; lower, 425 square inches
Length: 51 inches
Weight: 10 pounds
Wing loading: 24 ounces/square foot
Engine: .60-.91 two-stroke, .91-1.20 two-stroke
Construction: Balsa, light plywood (Laser-cut short kit is available.)
Finish: Film covering (Sig AeroKote was used) and matching paint
Radio: Four channels minimum, three ball-bearing standard servos, two lowprofile
aileron servos
Other: 3-inch
spinner, 3-inch main
wheels, 14-ounce fuel
tank, 1/6-scale pilot
bust, Sig 4-Star 120
aluminum landing
gear and wheel pants
While committing the Golden Era 60 (my
model design in the May 2008 MA) to CAD, I
made a few pencil sketches of how it would
look as a biplane. The similarity between it
and the Bearcat-engine-version of the Knight
Twister cannot be coincidental.
Since I had built a second fuselage and
empennage for the magazine pictures,
building a biplane conversion was a foregone
conclusion. ModelCAD 3000 was my weapon
of choice, and the pattern files were at
Creative Hobbies for laser cutting within a
week.
This build is typical for any modeler who
has discovered the joys (and frustrations) of
scratch building. The only unusual materials
are a few pieces of inexpensive, light, and
very strong composite tubing from
Kitebuilder.com.
Creative Hobbies sells a laser-cut kit of all
fabricated parts for the Golden Era 60
monoplane; only the biplane conversion kit;
or the fuselage, empennage, and bipe wing kit.
You can purchase the plans from the AMA
Plans Service.
A great fiberglass cowl is available from
Fiberglass Specialties. National Balsa or Balsa
USA can supply your balsa and plywood
needs. If you have already built the
monoplane version, you’ll need only the
biplane plans set.
This project’s mission was to create a
simple sport flier with no 3-D aspirations. I
equipped it with standard ball-bearing servos.
However, the control surfaces are more than
adequate for spirited aerobatics, and I have no
doubt that, with better servos and long throws,
the bipe would give a good aerobatic account
of itself at anybody’s club field.
This build is predicated on the concept of
using one fuselage and tail section as a basis
for two aircraft: a monoplane and a biplane. I
designed the monoplane first, and I didn’t
want to extensively modify the fuselage to
convert the Golden Era 60 to a biplane.
That decision led to the use of an adapter,
which allows the narrower biplane lower wing
to fit into the monoplane’s wing recess. The
adapter is also responsible for the wing-saddle
setup for the upper wing mount. The Golden
Era 60 is convertible with no readily
observable compromises.
This article will cover only those
assemblies and procedures necessary to
convert the Golden Era 60 to a biplane and
back to a monoplane. Field conversion should
take only minutes. Simply head to the field,
choose your set of wings, and fly.
If you are interested only in the biplane,
feel free to redesign the wing mountings,
struts, etc. One of the neat things about scratch
building is the option of doing it your way. If
you do, I’d love to see the result.
CONSTRUCTION
As with all scratch builds, it is best to have
all components fabricated and ready for
assembly. You should also have a completed
fuselage available for parts fitting.
I took great care, when making the
drawings, to ensure that the holes for pegs,
spars, wing LE, etc. are accurate within 1/32
inch. But the process of duplicating prints can
create small errors. It is the builder’s
responsibility to ensure that all critical drilled
holes are accurate for size and location.
When using the short kit, you’ll need to
scuff the burned area where cement, either
epoxy or cyanoacrylate, is being applied.
Adhesives bond poorly to a charred surface.
It’s unnecessary to remove all traces of
brown; sand enough to get loose surface scale
off. Don’t remove so much material that the
parts fit is impaired. Using the preceding tips,
I have not had a glue joint fail using the lasercut
parts.
In the remainder of the article, unless
otherwise noted, “cyanoacrylate” will mean
the medium adhesive and “epoxy” will mean
the 30-minute variety.
Adapter: This tool for the lower wing adapter
provides a means to mount the narrower lower
wings into the existing Golden Era 60 wing
recess. The adapter is an uncomplicated
structure consisting mainly of a few pieces of
1/4 plywood, scrap balsa, and basswood spar
material.
The adapter’s fit is critical to the angle of
incidence and the alignment of both the upper
and lower wings. If the finished assembly
can’t be made to comply with any of the
conditions in the following paragraphs, it’s
best to start over.
Epoxy is used for adapter construction.
Employ a lower wing rib as a pattern, and
ensure that the forward peg hole and the spar
holes in the adapter sides are coincident with
the corresponding holes in the wing rib. In
addition, ensure that the pegs in the adapter
front will line up with the holes in the
fuselage F1 assembly.
Using the adapter diagram on the print as
a guide, epoxy and clamp together the
adapter sides, front, and back. Make sure
that the assembly is square.
Install the wing mounting plate in the
slot provided. It should be flush with the
bottom of the assembly. Epoxy the 1/4-inch
pegs into the front of the adapter; they
should protrude approximately 3/8 inch and
have a slight chamfer at the exposed ends.
Cut the 1/4-inch LE positioning dowel to
extend past the adapter by 1 inch on either
side. Do not add epoxy at this time.
Check the assembly’s fit. The pegs
should engage the holes in fuselage former
F1, and the adapter sides should fit snugly
against the wing recess in the fuselage
sides. If the fore/aft fit is too tight, remove
some material from the rear of the adapter.
With the adapter temporarily installed
in the fuselage, insert the composite spar
through the opening in the adapter. Use a
large square to ensure that the spar extends
at right angles to the fuselage sides.
When the fit is satisfactory, install the
1/8-inch square adapter bottom support,
following the contour and recessed 3/32
inch. Mount the 3/32 balsa bottom. It should
be flush with the bottom of the adapter. I
used a 1/8 x 1/4 basswood crosspiece to help
support the balsa. The accompanying
pictures should clarify things.
Lower Wings: The lower wing panels are
identical as assembled over the plans. Protect
the plans with waxed paper, since both the left
and right lower sections will be constructed
over them.
Cut a piece of 1/8 x 1/4 basswood for use as
a bottom middle spar, and secure it in place
on the plans. It will be used as a guide to
ensure proper rib placement.
The lower ribs are the same. Using
cyanoacrylate and a small square, cement
them in place at their stations on the plans.
The break-off tabs should be flush against the
building board.
When the cyanoacrylate has set, install the
two 1/8 x 14-inch top spars and the 1/8-inch
square spar at the top rear. Cut a piece of .317
composite tubing to length, and use
cyanoacrylate to adhere it in place at the wing
LE. Its ends should be flush with the outside
surface of the center and end ribs.
Remove the wing from the plans and
install the remaining spars. Cut a length of 3/8
square balsa TE to size, and shape it as the
plans show. A razor plane and sanding block
will make short work of this task. Make a TE
for the left wing and set it aside.
Before performing the next steps, note that
the two inboard ribs on the lower wings are
spaced closer than those remaining. Don’t
make the mistake of attaching the wingtip to
the wrong end of the wing.
Cyanoacrylate-glue the TE to the wing and
26 MODEL AVIATION
secure the wingtip. Ensure that the wingtip
bisects the wing center and extends
horizontally, at right angles to the ribs. Cut
and install the spar extensions, beveling the
ends for a flush fit against the wingtip.
Snap off the rib stubs, and then sand the
area smooth. The wing should be symmetrical,
with no top or bottom. Decide whether it will
be a right or a left wing; mark it in several
places with your choice.
The false ribs used for the I-strut adapters
need to be installed. Using a scrap piece of 1/8
plywood as a temporary spacer to establish a
slot and cyanoacrylate-glue them in as
indicated on the plans.
Repeat the previous wing-building
instructions to construct the opposite wing.
The only difference will be when you mount
the servo plates and the interplane strut
mounts. Be careful; you cannot imagine how
easy it is to find yourself with two right or two
left wings.
Cut stiffeners of scrap spar material for the
servo plates, as shown on the plans diagram,
and adhere them in place with cyanoacrylate.
The side rails provide a gluing surface for
attaching the plate to the ribs, and the
transverse pieces provide a secure seat for the
servo mounting screws.
Test-position the servo plates on the
bottom of the wings. Make sure they don’t
interfere with insertion of the main spar. When
satisfied with the fit, epoxy the servo plates in
place as flush as possible with the bottom of
the ribs.
Because of the thin wing, it’s necessary to
use low-profile servos. I recommend the Blue
Bird BMS-706. For roughly a $20 street price,
you get dual ball bearings and 65 ounce-inch
of torque. Standard servos almost fit, but who
needs a lump in the wing covering?
At this point, insert a .505 main spar
through the adapter and into the wings. Make
sure that the LE positioning dowel engages the
.317 composite tubing. If it does not, reshape
the peg hole in the adapter fore or aft for a
proper fit. The vertical position must remain
unchanged. When satisfied, cyanoacrylateglue
the dowel only to the adapter.
The lower wings will not be permanently
mounted to the adapter until they are planked.
The strut adapters have been added and the
wings have been covered.
Shape the ailerons. Using the plans as a
pattern, cut the 3/8 x 2-inch tapered stock to a
shape that conforms to the wing TE. Install
hinges after you have applied the planking.
Upper Wings: Remove the lower-wing plans
from the building board, and secure the upperwing
plans in its place. The procedure for
building the upper wings is identical to the
procedure for building the lower, less the
servo mount.
After removing the wing halves from the
plans, decide whether or not you want hinged
ailerons on the upper wings, as are on the
lower. It is also time to cyanoacrylate-glue a
1/4 x 6-inch dowel into one LE at the wing
root. Allow 3 inches to protrude from the LE.
The dowel will slide into the opposite wing’s
LE as an alignment aid when they are joined.
There is generous aileron area on the
lower wing for general sport-flying, but I
chose to employ working ailerons on both
wings. I initially had the ailerons fixed to the
upper wings, as shown in the photo(s), but I
cut the upper ailerons free before covering.
This decision was prompted by discussions
with friends and, notably, a suggestion from a
certain magazine editor.
I have used a simple method to link the
upper and lower ailerons. The link is
positioned directly behind the aileron servo
for positive operation. Many biplanes’ slave
links are behind the interplane struts;
however, because of the I-struts’ outboard
location, that wasn’t a prudent solution with
this model.
Follow the plans for aileron shaping and
cutting. If the upper ailerons are going to be
fixed, you can adhere them to the TE with
cyanoacrylate after planking. Otherwise, cut
the ailerons as the plans indicate and shape the
LE for hinging.
This decision is reversible. The fixed
ailerons on the upper wings can easily be cut
free and hinged.
Wing Planking: The upper wings need 1/16 x
6 x 24 balsa for LE planking; the lower wings
require 1/16 x 5 x 24 balsa. If you are gluing
two pieces to get the width, use a 2- and a 4-
inch (or 3-inch) sheet to prevent the sharpest
bend from being at the glue joint.
Spray Windex generously to make the
balsa pliant enough to bend around the LE’s
tight radius. After it soaks for several minutes,
you should have no trouble making the bend.
The remaining planking is effortless. And
except for the wingtip LE, no further soaking
should be necessary. Capstrips are used on
both wings. I like the appearance, and they
add little weight. I also planked the entire
wingtips. (Doing so or not is the builder’s
choice.)
After planking is complete, use a few
small spots of planking cyanoacrylate to
temporarily attach the ailerons to both sets of
wings. Shape the ailerons to blend with the
wing TEs. After shaping, use cyanoacrylate
debonder or a hobby knife to remove the
ailerons.
This is a good time to cut aileron hinge
slots. I chose leaf hinges rather than the
typical cyanoacrylate type. I used four on each
side, spaced to avoid the ribs.
When you have completed the upper wing
halves except for covering, join them.
Install—but do not epoxy—the .505 spar. It
must be free to slide past the root rib, to the
wing saddle that will be inserted later. Use
the peg in one LE and the composite spar for
alignment, and epoxy and clamp the wing
halves together.
Upper Wing Saddle: Since making as few
modifications as possible to the original
fuselage was a priority, I had a problem. I
pondered how to attach the upper wing for far
longer than I care to admit. I was concerned
that a balsa-and-light plywood, “N”-style
cabane-strut system might not be strong
enough, and I didn’t want to resort to
aluminum; I’m not much of a metalworker.
The answer came to me as I worked on my
ham radio tower. I had some large UV-proof
tie-wraps I used to attach a heavy switchbox
to one of the tower legs. The old Knight
Twister had a pylon between the upper wing
and the fuselage; it would be simple to attach
the wings using a pylon or wing saddle and
these heavy-duty straps. Better still, it would
require only four small holes in the fuselage to
hold the straps in place.
The drawings on the plans show parts
outlines and materials for the wing saddle. It
is attached permanently to the upper wing and
uses two sections of industrial-strength nylon
tie-wrap to secure the saddle to the fuselage
using nylon bolts.
The tie-wraps are inexpensive and
extremely strong. I used the black Leco
Plastics L-48-175 wraps, which have a 175-
pound tensile (pull) strength. Although holes
have to be drilled in the ends, these tie-wraps
are good for the job. They are available at any
good hardware or construction-equipment
store.
The wing saddle is built up using several
pieces of balsa and plywood. Some shaping
and carving is necessary but shouldn’t present
a problem to an experienced builder. The
rectangular holes in the plywood are best
made by drilling the ends and then using a
Dremel or scroll saw to cut away the material
between the drilled holes.
The bipe-conversion short kit includes
laser-cut plywood saddle parts. Furnished are
one 1/4 plywood piece for the core of the
assembly and two 1/8 plywood outer pieces
with blades that go into the upper wing and
engage the spar. The two 3/8 balsa finish
pieces are left to the builder to fabricate.
The balsa parts have a channel for the
straps that terminates in a rectangular opening
at the lower, outside edge. The easiest way to
make the balsa parts is to shape the outline
and then cut notches in the bottom. Use a
rotary tool to rout out the inside to allow for
passage of the straps.
Align the five pieces and clamp them
together. The top of all four pieces should be
flush. The holes in the two outer plywood
parts are slightly larger and lower, to allow for
the curve in the retaining straps.
While the parts are clamped together, testfit
a length of strap. The tie-wraps are snaked
through the rectangular slots in the saddle
assembly. These should be able to pass
through the wing saddle and slide freely. Use
pliers to curve the end of the strap; that should
make it easier to fish through the wing saddle.
When satisfied with the fit, remove the
straps and epoxy all five parts together,
clamping them until set. Ensure that the
strap holes remain clear. Use a file or a
rotary tool to contour the bottom to closely
match the curve of the fuselage, and then
round the front and rear.
Finish the entire saddle per your taste.
Then insert the straps, leaving roughly 6
inches extending on either side of the
saddle, front and rear.
Make the holes in the fuselage for the #8
bolt hardware. The holes should be large
enough for the 8-32 captive nuts to be
epoxied inside the fuselage.
The front mounting holes in the fuselage
should be just aft of former F1 and 1/4 inch
below the junction of the curved top and the
fuselage sides. The rear set of holes is 51/2
inches farther aft. (See the assembly diagram.)
Carefully center the wing saddle, hold it in
place with masking tape, and mark and drill
the straps for 8-32 nylon screws. It’s a good
idea to mark center with a bit of striping tape
as a permanent alignment aid.
Be careful to ensure that the straps will
hold the saddle tightly against the fuselage.
The tie-wraps will not stretch, so the position
of the holes is critical.
Glue a felt pad to the bottom of the saddle,
to prevent damage to the fuselage. Install the
pad after drilling the holes. It will take up any
slack in the straps and ensure a tight fit. Use a
couple layers of felt if necessary.
Cut 1/8-inch slots in the planking on the
bottom of the upper wing for the wing-saddle
blades. Cover the area with a 4-inch strip of
film, to eliminate the need for meticulous
trimming around the wing saddle when
covering the wings. Remove the film from the
area of the slots.
Slide the composite main spar all the way
to one wingtip, and then apply epoxy to the
inside of the blades extending from the wing
saddle. Use a couple strips of masking tape
applied to the wing bottom to prevent the
epoxy from migrating.
Insert the blades into the slots,
sandwiching the root ribs. Seat the wing
saddle snug against the wing and center the
composite spar, sliding it through the holes in
the blades.
Apply epoxy to the spar at several rib
intersections, securing it permanently. Put
some weight on the bottom of the saddle to
hold it firmly against the wing, and set it aside
to cure.
Interplane Struts: These consist of six
separate pieces: four fixed adapters that are
fabricated and epoxied to the upper and lower
wings after covering and two struts that are
permanently hinged to the top wing adapters
using Sig Giant Scale hinges. (See the
assembly drawing for clarification.)
The upper and lower wing I-strut adapters
are made from 1/8 plywood. Assemble them
according to the plans, sand them smooth, and
check for fit in the appropriate slots.
The interplane struts are made from 1/8
light plywood and 1/8 balsa. Use the plans
pattern to make two pieces of each material. It
is important to have the balsa lamination
inboard on each side.
Adhere the parts with cyanoacrylate, and
then sand the edges to a rounded contour.
Finish the struts and adapters with fuelproof
paint.
Using the assembly drawing as a guide,
epoxy hinges in the fixed upper adapter and
February 2009 31
the I-struts. You can fill the recesses in the Istruts
with balsa filler after hinging, or you
can make a skirt to conceal the hinge
mechanism. In any case, be sure that the
hinges can move a few degrees in the
direction they need to go, and don’t forget to
peg the hinge stubs recessed in the I-struts.
The free part of the hinges on the bottom
of the I-struts extend into the fixed lower strut
adapter during field assembly, and two 3-48 x
1/2-inch button-head screws secure them in
place on each side.
With the wings covered, cut the strutadapter
slots in both wings. The upper adapter
should have the I-struts permanently installed.
Make sure that the hinges are free enough to
let the struts fold inboard, flat against the
wing, for storage and transportation.
Use epoxy to install the strut adapters in
the lower wing. Ensure that they’re properly
oriented. This completes the building portion
of the Golden Era 60 biplane conversion.
An assembly diagram is included on these
pages, and no further explanation should be
necessary. I sent the original bipe to AMA
Headquarters for testing. Following is MA
Editor Michael Ramsey’s review.
Flying: Ground-handling the Golden Era 60
biplane is similar to driving a motor home;
just set the cruise control and go make a
sandwich in the galley. It’s that assuring and
easy.
The long tail moment and wide landing
gear do everything to keep the taxi stuff
friendly. Even the high-speed run before
liftoff requires little or nothing to be done
with the rudder. When this model rolls down
the runway at a speed where it looks like it
should fly, haul back on the elevator and up it
goes, straight and true.
The GMS .61 engine, which this airframe
is built around, is a nice sport power plant for
such a model. It’s reminiscent of the “old
school” power philosophy; the airplane flies
on the wing and not on the propeller.
As noted during testing, the Golden Era
can handle, and in some cases deserves, the
power a .91 two-stroke or four-stroke engine
could give it. If that’s what you have in your
engine drawer, by all means put it in.
With its 900 square inches of wing area,
this model can cruise around comfortably at
65% power. Coordinating the turns is
unnecessary when the speed is kept up, but in
the wind it likes slight rudder mixed in the
same direction as the aileron input. Elevator
in the turns, whether they’re inside or outside,
can crank the bipe around as tightly as the
pilot wants, given that the power in the
engine is willing.
The rudder is ghastly effective, which,
given its size ratio comparison with the rest of
the surfaces, was a huge yet pleasant surprise.
I set the high rate travel to maximum
deflection and found it to be extremely
touchy for normal flight but the heart of the
tumbling trickery that this model has in its
bag of magic.
For the most part, 50% throw in the
rudder plus approximately 30% exponential
was a decent setup. That way, the stall turns
can be done in a tight half circle.
A large amount of rudder input can tuck
the nose toward the landing gear, so watch
during landing if heading corrections are
required. In knife-edge flight, the rudder
corrections want to naturally roll the model
back to level flight, and it’s already pushing
away from the canopy. For the most part, the
pilot can hold these corrections in for a
wicked-cool knife-edge pass down on the
deck, but a P-mix or two into the rudder will
fix the habit completely.
The twin ailerons are a delight; both
wings work together, rather than one wing
with ailerons having to overcome the drag of
the other. Little deflection is needed for
normal flying, and the ailerons’ movement
requires no differential mixing because their
travel is minimal.
Point rolls are possible that we can relate
to the crispness we see at air shows with the
Pitts biplanes. That includes the “wow”
factor.
Landing the Golden Era bipe is almost
easier than landing a trainer. Because it flies
where the pilot points it, bringing the model
home is a matter of “X” marks the spot. With
a throttle setting of roughly 50%, this airplane
sets itself into a natural glide slope; all the
pilot needs to do is gently pull on the upelevator
before touchdown and ease the
throttle back to idle.
Make the Golden Era biplane your
everyday flier. I’ve tested it in calm and
hurricanelike conditions, and I was
phenomenally impressed by how solidly it
performed.
Thanks for the airplane, Fred. I’m having
a blast! MA
Fred Randall
[email protected]
Sources:
Payne Knight Twister information, full-size
home-built plans:
www.steenaero.com
Creative Hobbies
(508) 473-8259
www.creativehobbies.net
Composite tubing:
Kite Studio
(800) KITE-991
www.kitebuilder.com/catalog/index.php
AMA Plans Service
(800) 435-9262, ext. 507
www.modelaircraft.org/plans.aspx
Fiberglass Specialties
(479) 359-2259
www.fiberglassspecialtiesinc.com
National Balsa Co.
(413) 277-9500
www.nationalbalsa.com
Balsa USA
(800) 225-7287
www.balsausa.com

Left: This model’s looks are reminiscent of
the Payne Knight Twister published in the
1938 Air Trails. It has the look of a
Schneider Cup racer as well, and the
groovy performance.
Two wings are as
much fun as one—
this model
offers a choice
WHILE ON A Sunday drive with my parents
in 1938, I bought my first model aviation
magazine. We had stopped at a variety store
for ice cream, as was usual on these outings,
and I browsed the magazine rack while we
waited for our order.
A picture inside Air Trails magazine
caught my eye; I begged my mother for the
15¢ to buy the periodical, and she relented.
The object of my interest was the tiny Knight
Twister biplane that was powered by a Ford
Model A engine, modified for air-cooling.
The airplane was Vernon Payne’s landmark
home-built of the prewar period.
It was love at first sight for a 5-year-old
aviation nut, and the little airplane carved a
permanent niche in the back of my mind. The
magazine also ignited an interest in aircraft
modeling that has stayed with me for almost
70 years. I kept the magazine until I married
in 1956 and moved out of the house in which
I was born. I wish I still had it.
Flight photos by Mark Lanterman Construction photos by the author Static photos by Michael Ramsey
02sig1.QXD 12/22/08 1:11 PM Page 18
Type: RC sport
Skill level: Intermediate builder and pilot
Wingspan: Upper, 55.375 inches; lower, 49.375 inches
Wing area: Upper, 540 square inches; lower, 425 square inches
Length: 51 inches
Weight: 10 pounds
Wing loading: 24 ounces/square foot
Engine: .60-.91 two-stroke, .91-1.20 two-stroke
Construction: Balsa, light plywood (Laser-cut short kit is available.)
Finish: Film covering (Sig AeroKote was used) and matching paint
Radio: Four channels minimum, three ball-bearing standard servos, two lowprofile
aileron servos
Other: 3-inch
spinner, 3-inch main
wheels, 14-ounce fuel
tank, 1/6-scale pilot
bust, Sig 4-Star 120
aluminum landing
gear and wheel pants
While committing the Golden Era 60 (my
model design in the May 2008 MA) to CAD, I
made a few pencil sketches of how it would
look as a biplane. The similarity between it
and the Bearcat-engine-version of the Knight
Twister cannot be coincidental.
Since I had built a second fuselage and
empennage for the magazine pictures,
building a biplane conversion was a foregone
conclusion. ModelCAD 3000 was my weapon
of choice, and the pattern files were at
Creative Hobbies for laser cutting within a
week.
This build is typical for any modeler who
has discovered the joys (and frustrations) of
scratch building. The only unusual materials
are a few pieces of inexpensive, light, and
very strong composite tubing from
Kitebuilder.com.
Creative Hobbies sells a laser-cut kit of all
fabricated parts for the Golden Era 60
monoplane; only the biplane conversion kit;
or the fuselage, empennage, and bipe wing kit.
You can purchase the plans from the AMA
Plans Service.
A great fiberglass cowl is available from
Fiberglass Specialties. National Balsa or Balsa
USA can supply your balsa and plywood
needs. If you have already built the
monoplane version, you’ll need only the
biplane plans set.
This project’s mission was to create a
simple sport flier with no 3-D aspirations. I
equipped it with standard ball-bearing servos.
However, the control surfaces are more than
adequate for spirited aerobatics, and I have no
doubt that, with better servos and long throws,
the bipe would give a good aerobatic account
of itself at anybody’s club field.
This build is predicated on the concept of
using one fuselage and tail section as a basis
for two aircraft: a monoplane and a biplane. I
designed the monoplane first, and I didn’t
want to extensively modify the fuselage to
convert the Golden Era 60 to a biplane.
That decision led to the use of an adapter,
which allows the narrower biplane lower wing
to fit into the monoplane’s wing recess. The
adapter is also responsible for the wing-saddle
setup for the upper wing mount. The Golden
Era 60 is convertible with no readily
observable compromises.
This article will cover only those
assemblies and procedures necessary to
convert the Golden Era 60 to a biplane and
back to a monoplane. Field conversion should
take only minutes. Simply head to the field,
choose your set of wings, and fly.
If you are interested only in the biplane,
feel free to redesign the wing mountings,
struts, etc. One of the neat things about scratch
building is the option of doing it your way. If
you do, I’d love to see the result.
CONSTRUCTION
As with all scratch builds, it is best to have
all components fabricated and ready for
assembly. You should also have a completed
fuselage available for parts fitting.
I took great care, when making the
drawings, to ensure that the holes for pegs,
spars, wing LE, etc. are accurate within 1/32
inch. But the process of duplicating prints can
create small errors. It is the builder’s
responsibility to ensure that all critical drilled
holes are accurate for size and location.
When using the short kit, you’ll need to
scuff the burned area where cement, either
epoxy or cyanoacrylate, is being applied.
Adhesives bond poorly to a charred surface.
It’s unnecessary to remove all traces of
brown; sand enough to get loose surface scale
off. Don’t remove so much material that the
parts fit is impaired. Using the preceding tips,
I have not had a glue joint fail using the lasercut
parts.
In the remainder of the article, unless
otherwise noted, “cyanoacrylate” will mean
the medium adhesive and “epoxy” will mean
the 30-minute variety.
Adapter: This tool for the lower wing adapter
provides a means to mount the narrower lower
wings into the existing Golden Era 60 wing
recess. The adapter is an uncomplicated
structure consisting mainly of a few pieces of
1/4 plywood, scrap balsa, and basswood spar
material.
The adapter’s fit is critical to the angle of
incidence and the alignment of both the upper
and lower wings. If the finished assembly
can’t be made to comply with any of the
conditions in the following paragraphs, it’s
best to start over.
Epoxy is used for adapter construction.
Employ a lower wing rib as a pattern, and
ensure that the forward peg hole and the spar
holes in the adapter sides are coincident with
the corresponding holes in the wing rib. In
addition, ensure that the pegs in the adapter
front will line up with the holes in the
fuselage F1 assembly.
Using the adapter diagram on the print as
a guide, epoxy and clamp together the
adapter sides, front, and back. Make sure
that the assembly is square.
Install the wing mounting plate in the
slot provided. It should be flush with the
bottom of the assembly. Epoxy the 1/4-inch
pegs into the front of the adapter; they
should protrude approximately 3/8 inch and
have a slight chamfer at the exposed ends.
Cut the 1/4-inch LE positioning dowel to
extend past the adapter by 1 inch on either
side. Do not add epoxy at this time.
Check the assembly’s fit. The pegs
should engage the holes in fuselage former
F1, and the adapter sides should fit snugly
against the wing recess in the fuselage
sides. If the fore/aft fit is too tight, remove
some material from the rear of the adapter.
With the adapter temporarily installed
in the fuselage, insert the composite spar
through the opening in the adapter. Use a
large square to ensure that the spar extends
at right angles to the fuselage sides.
When the fit is satisfactory, install the
1/8-inch square adapter bottom support,
following the contour and recessed 3/32
inch. Mount the 3/32 balsa bottom. It should
be flush with the bottom of the adapter. I
used a 1/8 x 1/4 basswood crosspiece to help
support the balsa. The accompanying
pictures should clarify things.
Lower Wings: The lower wing panels are
identical as assembled over the plans. Protect
the plans with waxed paper, since both the left
and right lower sections will be constructed
over them.
Cut a piece of 1/8 x 1/4 basswood for use as
a bottom middle spar, and secure it in place
on the plans. It will be used as a guide to
ensure proper rib placement.
The lower ribs are the same. Using
cyanoacrylate and a small square, cement
them in place at their stations on the plans.
The break-off tabs should be flush against the
building board.
When the cyanoacrylate has set, install the
two 1/8 x 14-inch top spars and the 1/8-inch
square spar at the top rear. Cut a piece of .317
composite tubing to length, and use
cyanoacrylate to adhere it in place at the wing
LE. Its ends should be flush with the outside
surface of the center and end ribs.
Remove the wing from the plans and
install the remaining spars. Cut a length of 3/8
square balsa TE to size, and shape it as the
plans show. A razor plane and sanding block
will make short work of this task. Make a TE
for the left wing and set it aside.
Before performing the next steps, note that
the two inboard ribs on the lower wings are
spaced closer than those remaining. Don’t
make the mistake of attaching the wingtip to
the wrong end of the wing.
Cyanoacrylate-glue the TE to the wing and
26 MODEL AVIATION
secure the wingtip. Ensure that the wingtip
bisects the wing center and extends
horizontally, at right angles to the ribs. Cut
and install the spar extensions, beveling the
ends for a flush fit against the wingtip.
Snap off the rib stubs, and then sand the
area smooth. The wing should be symmetrical,
with no top or bottom. Decide whether it will
be a right or a left wing; mark it in several
places with your choice.
The false ribs used for the I-strut adapters
need to be installed. Using a scrap piece of 1/8
plywood as a temporary spacer to establish a
slot and cyanoacrylate-glue them in as
indicated on the plans.
Repeat the previous wing-building
instructions to construct the opposite wing.
The only difference will be when you mount
the servo plates and the interplane strut
mounts. Be careful; you cannot imagine how
easy it is to find yourself with two right or two
left wings.
Cut stiffeners of scrap spar material for the
servo plates, as shown on the plans diagram,
and adhere them in place with cyanoacrylate.
The side rails provide a gluing surface for
attaching the plate to the ribs, and the
transverse pieces provide a secure seat for the
servo mounting screws.
Test-position the servo plates on the
bottom of the wings. Make sure they don’t
interfere with insertion of the main spar. When
satisfied with the fit, epoxy the servo plates in
place as flush as possible with the bottom of
the ribs.
Because of the thin wing, it’s necessary to
use low-profile servos. I recommend the Blue
Bird BMS-706. For roughly a $20 street price,
you get dual ball bearings and 65 ounce-inch
of torque. Standard servos almost fit, but who
needs a lump in the wing covering?
At this point, insert a .505 main spar
through the adapter and into the wings. Make
sure that the LE positioning dowel engages the
.317 composite tubing. If it does not, reshape
the peg hole in the adapter fore or aft for a
proper fit. The vertical position must remain
unchanged. When satisfied, cyanoacrylateglue
the dowel only to the adapter.
The lower wings will not be permanently
mounted to the adapter until they are planked.
The strut adapters have been added and the
wings have been covered.
Shape the ailerons. Using the plans as a
pattern, cut the 3/8 x 2-inch tapered stock to a
shape that conforms to the wing TE. Install
hinges after you have applied the planking.
Upper Wings: Remove the lower-wing plans
from the building board, and secure the upperwing
plans in its place. The procedure for
building the upper wings is identical to the
procedure for building the lower, less the
servo mount.
After removing the wing halves from the
plans, decide whether or not you want hinged
ailerons on the upper wings, as are on the
lower. It is also time to cyanoacrylate-glue a
1/4 x 6-inch dowel into one LE at the wing
root. Allow 3 inches to protrude from the LE.
The dowel will slide into the opposite wing’s
LE as an alignment aid when they are joined.
There is generous aileron area on the
lower wing for general sport-flying, but I
chose to employ working ailerons on both
wings. I initially had the ailerons fixed to the
upper wings, as shown in the photo(s), but I
cut the upper ailerons free before covering.
This decision was prompted by discussions
with friends and, notably, a suggestion from a
certain magazine editor.
I have used a simple method to link the
upper and lower ailerons. The link is
positioned directly behind the aileron servo
for positive operation. Many biplanes’ slave
links are behind the interplane struts;
however, because of the I-struts’ outboard
location, that wasn’t a prudent solution with
this model.
Follow the plans for aileron shaping and
cutting. If the upper ailerons are going to be
fixed, you can adhere them to the TE with
cyanoacrylate after planking. Otherwise, cut
the ailerons as the plans indicate and shape the
LE for hinging.
This decision is reversible. The fixed
ailerons on the upper wings can easily be cut
free and hinged.
Wing Planking: The upper wings need 1/16 x
6 x 24 balsa for LE planking; the lower wings
require 1/16 x 5 x 24 balsa. If you are gluing
two pieces to get the width, use a 2- and a 4-
inch (or 3-inch) sheet to prevent the sharpest
bend from being at the glue joint.
Spray Windex generously to make the
balsa pliant enough to bend around the LE’s
tight radius. After it soaks for several minutes,
you should have no trouble making the bend.
The remaining planking is effortless. And
except for the wingtip LE, no further soaking
should be necessary. Capstrips are used on
both wings. I like the appearance, and they
add little weight. I also planked the entire
wingtips. (Doing so or not is the builder’s
choice.)
After planking is complete, use a few
small spots of planking cyanoacrylate to
temporarily attach the ailerons to both sets of
wings. Shape the ailerons to blend with the
wing TEs. After shaping, use cyanoacrylate
debonder or a hobby knife to remove the
ailerons.
This is a good time to cut aileron hinge
slots. I chose leaf hinges rather than the
typical cyanoacrylate type. I used four on each
side, spaced to avoid the ribs.
When you have completed the upper wing
halves except for covering, join them.
Install—but do not epoxy—the .505 spar. It
must be free to slide past the root rib, to the
wing saddle that will be inserted later. Use
the peg in one LE and the composite spar for
alignment, and epoxy and clamp the wing
halves together.
Upper Wing Saddle: Since making as few
modifications as possible to the original
fuselage was a priority, I had a problem. I
pondered how to attach the upper wing for far
longer than I care to admit. I was concerned
that a balsa-and-light plywood, “N”-style
cabane-strut system might not be strong
enough, and I didn’t want to resort to
aluminum; I’m not much of a metalworker.
The answer came to me as I worked on my
ham radio tower. I had some large UV-proof
tie-wraps I used to attach a heavy switchbox
to one of the tower legs. The old Knight
Twister had a pylon between the upper wing
and the fuselage; it would be simple to attach
the wings using a pylon or wing saddle and
these heavy-duty straps. Better still, it would
require only four small holes in the fuselage to
hold the straps in place.
The drawings on the plans show parts
outlines and materials for the wing saddle. It
is attached permanently to the upper wing and
uses two sections of industrial-strength nylon
tie-wrap to secure the saddle to the fuselage
using nylon bolts.
The tie-wraps are inexpensive and
extremely strong. I used the black Leco
Plastics L-48-175 wraps, which have a 175-
pound tensile (pull) strength. Although holes
have to be drilled in the ends, these tie-wraps
are good for the job. They are available at any
good hardware or construction-equipment
store.
The wing saddle is built up using several
pieces of balsa and plywood. Some shaping
and carving is necessary but shouldn’t present
a problem to an experienced builder. The
rectangular holes in the plywood are best
made by drilling the ends and then using a
Dremel or scroll saw to cut away the material
between the drilled holes.
The bipe-conversion short kit includes
laser-cut plywood saddle parts. Furnished are
one 1/4 plywood piece for the core of the
assembly and two 1/8 plywood outer pieces
with blades that go into the upper wing and
engage the spar. The two 3/8 balsa finish
pieces are left to the builder to fabricate.
The balsa parts have a channel for the
straps that terminates in a rectangular opening
at the lower, outside edge. The easiest way to
make the balsa parts is to shape the outline
and then cut notches in the bottom. Use a
rotary tool to rout out the inside to allow for
passage of the straps.
Align the five pieces and clamp them
together. The top of all four pieces should be
flush. The holes in the two outer plywood
parts are slightly larger and lower, to allow for
the curve in the retaining straps.
While the parts are clamped together, testfit
a length of strap. The tie-wraps are snaked
through the rectangular slots in the saddle
assembly. These should be able to pass
through the wing saddle and slide freely. Use
pliers to curve the end of the strap; that should
make it easier to fish through the wing saddle.
When satisfied with the fit, remove the
straps and epoxy all five parts together,
clamping them until set. Ensure that the
strap holes remain clear. Use a file or a
rotary tool to contour the bottom to closely
match the curve of the fuselage, and then
round the front and rear.
Finish the entire saddle per your taste.
Then insert the straps, leaving roughly 6
inches extending on either side of the
saddle, front and rear.
Make the holes in the fuselage for the #8
bolt hardware. The holes should be large
enough for the 8-32 captive nuts to be
epoxied inside the fuselage.
The front mounting holes in the fuselage
should be just aft of former F1 and 1/4 inch
below the junction of the curved top and the
fuselage sides. The rear set of holes is 51/2
inches farther aft. (See the assembly diagram.)
Carefully center the wing saddle, hold it in
place with masking tape, and mark and drill
the straps for 8-32 nylon screws. It’s a good
idea to mark center with a bit of striping tape
as a permanent alignment aid.
Be careful to ensure that the straps will
hold the saddle tightly against the fuselage.
The tie-wraps will not stretch, so the position
of the holes is critical.
Glue a felt pad to the bottom of the saddle,
to prevent damage to the fuselage. Install the
pad after drilling the holes. It will take up any
slack in the straps and ensure a tight fit. Use a
couple layers of felt if necessary.
Cut 1/8-inch slots in the planking on the
bottom of the upper wing for the wing-saddle
blades. Cover the area with a 4-inch strip of
film, to eliminate the need for meticulous
trimming around the wing saddle when
covering the wings. Remove the film from the
area of the slots.
Slide the composite main spar all the way
to one wingtip, and then apply epoxy to the
inside of the blades extending from the wing
saddle. Use a couple strips of masking tape
applied to the wing bottom to prevent the
epoxy from migrating.
Insert the blades into the slots,
sandwiching the root ribs. Seat the wing
saddle snug against the wing and center the
composite spar, sliding it through the holes in
the blades.
Apply epoxy to the spar at several rib
intersections, securing it permanently. Put
some weight on the bottom of the saddle to
hold it firmly against the wing, and set it aside
to cure.
Interplane Struts: These consist of six
separate pieces: four fixed adapters that are
fabricated and epoxied to the upper and lower
wings after covering and two struts that are
permanently hinged to the top wing adapters
using Sig Giant Scale hinges. (See the
assembly drawing for clarification.)
The upper and lower wing I-strut adapters
are made from 1/8 plywood. Assemble them
according to the plans, sand them smooth, and
check for fit in the appropriate slots.
The interplane struts are made from 1/8
light plywood and 1/8 balsa. Use the plans
pattern to make two pieces of each material. It
is important to have the balsa lamination
inboard on each side.
Adhere the parts with cyanoacrylate, and
then sand the edges to a rounded contour.
Finish the struts and adapters with fuelproof
paint.
Using the assembly drawing as a guide,
epoxy hinges in the fixed upper adapter and
February 2009 31
the I-struts. You can fill the recesses in the Istruts
with balsa filler after hinging, or you
can make a skirt to conceal the hinge
mechanism. In any case, be sure that the
hinges can move a few degrees in the
direction they need to go, and don’t forget to
peg the hinge stubs recessed in the I-struts.
The free part of the hinges on the bottom
of the I-struts extend into the fixed lower strut
adapter during field assembly, and two 3-48 x
1/2-inch button-head screws secure them in
place on each side.
With the wings covered, cut the strutadapter
slots in both wings. The upper adapter
should have the I-struts permanently installed.
Make sure that the hinges are free enough to
let the struts fold inboard, flat against the
wing, for storage and transportation.
Use epoxy to install the strut adapters in
the lower wing. Ensure that they’re properly
oriented. This completes the building portion
of the Golden Era 60 biplane conversion.
An assembly diagram is included on these
pages, and no further explanation should be
necessary. I sent the original bipe to AMA
Headquarters for testing. Following is MA
Editor Michael Ramsey’s review.
Flying: Ground-handling the Golden Era 60
biplane is similar to driving a motor home;
just set the cruise control and go make a
sandwich in the galley. It’s that assuring and
easy.
The long tail moment and wide landing
gear do everything to keep the taxi stuff
friendly. Even the high-speed run before
liftoff requires little or nothing to be done
with the rudder. When this model rolls down
the runway at a speed where it looks like it
should fly, haul back on the elevator and up it
goes, straight and true.
The GMS .61 engine, which this airframe
is built around, is a nice sport power plant for
such a model. It’s reminiscent of the “old
school” power philosophy; the airplane flies
on the wing and not on the propeller.
As noted during testing, the Golden Era
can handle, and in some cases deserves, the
power a .91 two-stroke or four-stroke engine
could give it. If that’s what you have in your
engine drawer, by all means put it in.
With its 900 square inches of wing area,
this model can cruise around comfortably at
65% power. Coordinating the turns is
unnecessary when the speed is kept up, but in
the wind it likes slight rudder mixed in the
same direction as the aileron input. Elevator
in the turns, whether they’re inside or outside,
can crank the bipe around as tightly as the
pilot wants, given that the power in the
engine is willing.
The rudder is ghastly effective, which,
given its size ratio comparison with the rest of
the surfaces, was a huge yet pleasant surprise.
I set the high rate travel to maximum
deflection and found it to be extremely
touchy for normal flight but the heart of the
tumbling trickery that this model has in its
bag of magic.
For the most part, 50% throw in the
rudder plus approximately 30% exponential
was a decent setup. That way, the stall turns
can be done in a tight half circle.
A large amount of rudder input can tuck
the nose toward the landing gear, so watch
during landing if heading corrections are
required. In knife-edge flight, the rudder
corrections want to naturally roll the model
back to level flight, and it’s already pushing
away from the canopy. For the most part, the
pilot can hold these corrections in for a
wicked-cool knife-edge pass down on the
deck, but a P-mix or two into the rudder will
fix the habit completely.
The twin ailerons are a delight; both
wings work together, rather than one wing
with ailerons having to overcome the drag of
the other. Little deflection is needed for
normal flying, and the ailerons’ movement
requires no differential mixing because their
travel is minimal.
Point rolls are possible that we can relate
to the crispness we see at air shows with the
Pitts biplanes. That includes the “wow”
factor.
Landing the Golden Era bipe is almost
easier than landing a trainer. Because it flies
where the pilot points it, bringing the model
home is a matter of “X” marks the spot. With
a throttle setting of roughly 50%, this airplane
sets itself into a natural glide slope; all the
pilot needs to do is gently pull on the upelevator
before touchdown and ease the
throttle back to idle.
Make the Golden Era biplane your
everyday flier. I’ve tested it in calm and
hurricanelike conditions, and I was
phenomenally impressed by how solidly it
performed.
Thanks for the airplane, Fred. I’m having
a blast! MA
Fred Randall
[email protected]
Sources:
Payne Knight Twister information, full-size
home-built plans:
www.steenaero.com
Creative Hobbies
(508) 473-8259
www.creativehobbies.net
Composite tubing:
Kite Studio
(800) KITE-991
www.kitebuilder.com/catalog/index.php
AMA Plans Service
(800) 435-9262, ext. 507
www.modelaircraft.org/plans.aspx
Fiberglass Specialties
(479) 359-2259
www.fiberglassspecialtiesinc.com
National Balsa Co.
(413) 277-9500
www.nationalbalsa.com
Balsa USA
(800) 225-7287
www.balsausa.com