Here are plans for the Eclipse that I electronically scanned from
page 24 of my purchased copy of the October 1974 American Aircraft
Modeler magazine. You might be able to scale up the image below
if you cannot find a source for ordering plans. Plans for this fine
model were drawn by Mr. Hal Cover. All copyrights (if any) are hereby
The Eclipse is an all-balsa radio-controlled sailplane model
with a 16-foot wingspan, geodesic ribs construction, and "V" tail
configuration. I remember first seeing the model on the cover back
in 1974 and really wanting to have one. Unfortunately,
I was only 16 years old at the time and was barely able to afford
control line models, let alone a huge RC sailplane!
It casts a big shadow - with 16 feet of wing it should! Designed
specifically for extended duration, the Eclipse will ride thermals
By Hal Cover
a glider with a 180" span and the name Eclipse? You will understand
the first time it flies over your head with its gracefulness and
beauty. When it lands the size becomes very apparent, and you might
even expect a pilot to climb out looking for his glider trailer.
In comparing the performance of the Eclipse to a smaller version,
interesting performance variations appeared. First it flew in much
higher winds than the smaller one, even thought both had a an 8
oz./sq. ft. wing loading. Also, still air flight times were as much
as 50% better with the larger model. Probably the larger glider's
only weakness is that it is hard to pick up thermals at low altitude.
The relatively large tail and long tail moment contributes to its
extremely stable flight characteristics.
In calm weather, flights of up to ten minutes have been made
without aid of the controls - in other words, free flight ... that
includes the launch, too! If the plane is allowed to fly straight,
it will turn into lift by itself and stay in lift; so let it find
the lift for you. The spoilers are just effective enough to allow
a good controlled sink, with only up trim needed for proper attitude.
This makes spot landings a cinch.
The spoilers proved their worth on one flight where the plane
rode a thermal until it disappeared in the clouds. At this point,
the spoilers were opened and a large circle set in the controls.
Without further action, the plane came down safely ... but it took
half an hour! This plane is big, and therefore can't be treated
like a small plywood and foam glider. If it gets way up in a thermal,
use the spoilers and up trim; don't dive it or spiral it in because
the plane picks up speed fast and it is not indestructible.
Locating a fiberglass tail boom for the Eclipse may pose a problem
for prospective builders. However, there are several approaches
one can take. First, as the author did, contact your local sporting
goods store and have them recommend a fishing pole manufacturer
from whom you can make a selection.
The Eclipse is not, as it looks, a myriad of little pieces -
it's a myriad of big pieces! Using geodetic construction is
the only way to build a 16-foot soarer with a reasonable wing
loading and good strength.
Detail shot of the wing structure shows spar webbing and warren
The modular wing center section houses the spoiler servo. The
model disassembles very quickly and stores easily with this
The V-tail is ultra-light, yet rugged. Minimizing drag on a
50" tail moment is critical to maneuverability.
The back servo slides on a tray. The link to the forward servo
is drilled right into the servo case top. The slender pod decreases
The author launches the mammoth beastie. The light wing loading
makes hi-starts practical.
If no manufacturer is readily available, perhaps the sporting
goods store will order one for you. The fiberglass rod should be
about seven-nine ounces in weight, eight to nine feet long and have
a diameter of approximately 1 1/4" at the large end. If you have
difficulty with either of these approaches, contact me, c/o AAM,
and I'll supply you with a boom equivalent to the one used on the
Building Tips: Always use spruce wherever shown
- don't substitute balsa. Web all areas indicated with hard balsa.
The wing and stab structures require a web for necessary structural
The wing center section needs the 1/16" piano wire and fiberglass
cloth covering on the trailing edge; it is also recommended that
the center section leading edge and tip dihedral leading edge and
trailing edge joints be fiberglassed. Use epoxy and glass cloth
as needed wherever wire hooks or tubing are installed.
Fuselage Construction: The fuselage is constructed
from medium balsa sheet and blocks. The sides are cut from 3/4 x
5 x 24" sheet, the nose block is 9 x 2 x 4" and the rear fuse block
is 5 x 2 x 8". 3/4 x 2 x 12" sheet is used on the top and bottom.
The tail boom size may vary depending upon what is available, but
the author's plane had a boom 50" long, 1" in diameter tapered to
Cut out the blocks as shown on the plans. Glue
the blocks, top and bottom sheet to a side sheet. When dry, sand
the edge of the unplanked side to obtain a good flush joint. Glue
the second side in place. Don't carve the fuselage to the correct
cross section until the tail boom is installed.
Tailboom Installation: The tail boom installation
is critical and should be done carefully. Place the fuselage upside
down on a flat surface at least six feet long. Block up the wing
mount platform to the correct incidence angle, as follows: The leading
edge portion of the wing platform (at former B) should be 1" off
the bench, and the trailing edge should be 1-9/16" off the bench.
This will position the wing platform on the fuselage at the correct
incidence angle, with the bench surface representing 0°.
In the next operation, the tailboom is going to be used as a
drill. Carefully sharpen the large end by chamfering the inside,
as shown on the plans. Alignment of the boom is achieved by blocking
the small end of the boom to the same height (1-9/16") above the
table as the trailing edge portion of the fuselage-the boom is now
at 0° also. A straight line drawn on the bench may be used for boom
alignment left to right. With the fuselage and boom held in the
proper position on the locating blocks, push the boom into the block
and drill by rotating with a fair amount of pressure. Once the boom
is into the block about one inch, the assembly may be removed from
the bench to finish the boring operation. This method may seem a
bit strange, but it gives an accurately aligned and tight fitting
boom. Remove the boom from the fuselage, take the plug out of the
boom and reinstall with five-minute epoxy.
Carve the fuselage, using the templates shown for correct contour.
Then cut out the cockpit with a band saw or coping saw.
Cut the plywood skid from 1/8" plywood and bond to the fuselage.
With the canopy in place, cover the entire fuselage with one layer
of one-ounce glass cloth. Put an additional two layers on the nose
and bottom of the fuselage, including the skid. Remove the canopy
and grind out the nose block as shown with a Moto-Tool or similar
device. The canopy can be held in place using several methods. The
original was held with a locating dowel in the front and snaps in
Servo Installation: The servo tray is made from
3/32" plywood. The servo cutout size will depend on the servos used.
The sliding servo is mounted to two pieces of 3/32" plywood: 1/4"
x servo width, plus 1/4". The guides for the sliding servo are made
by cementing 3/32" sq. hardwood to the strip on both sides, 1/8"
away from the servo cutout. Glue a strip of 1/16 x 3/16" hardwood
on top, with the overlap to the servo side. When cementing this
assembly, make sure the sliding servo can move freely up and down
the tray slide.
Towhook Installation: The towhook is made from
soft .032 aluminum and 1/16" wire. Bend the wire to shape and cut
out the 1/4 x 2 x 5/8" plywood support. Place the piano wire in
the fuselage as shown. Slip the aluminum hook in place and bolt
to the skid using 4-40 bolts.
Wing Hook Installation: These are formed from
1/16" piano wire and epoxied to the side of the fuselage, as shown.
For additional strength, cover them with two layers of glass cloth
Do as much finishing work as possible on the fuselage prior to
stab installation, because of the sheer size and awkwardness of
the fuselage/stab assembly.
Stab Construction: Only half the stab is shown
on the plans but, since the airfoil is symmetrical, build two halves
on the plan and flip one over for the other half.
Using blocks, pin the leading edge and trailing edge in place
1/4" above the plans at the center and 1/8" above at the tip. Cut
out the ribs using the template shown. Note that half of the ribs
are solid, or uncut, and zigzag to the tips. These should be installed
first, followed by the installation of the cut ribs.
The method of obtaining the correct airfoil for all ribs is done
as follows. Mark the 1/16" sheet balsa with the required rib length
and the 1/4" leading edge and 5/16" trailing edge height. Use airfoil
template "A" for the odd numbered ribs 1, 3, 5, etc., and template
"B" for even numbered ribs. Lay the airfoil template on the sheet
balsa with its leading edge placed so that the top mark just shows.
Position the rear of the template in a similar manner, with the
trailing edge mark just showing, then cut the top airfoil. Repeat
the operation for· the bottom surface.
Spar Installation: The tapered spruce stabilizer
spars are installed by marking the spar location and width (mark
both sides) on the inner rib (1) and the tip rib (13). Next lay
an aluminum yardstick or straightedge over the front marks, and
cut a notch 1/16" deep in all ribs. Move the yardstick to the back
marks and notch again. Then cut out the material between the notches.
Turn over and repeat the operation on the bottom of the stab.
Add the tip block and glue the spruce spars in place, but make sure
there are one or two inches extra in the center for stab installation
to the tail boom. Shape the LE and TE, then sand all ribs.
Stab Installation: Fit the leading and trailing
edge to the boom carefully. Epoxy the dihedral brace (G) to the
end of the boom, making sure it aligns with the wing platform. The
spars will lay over and under, as shown on the plans, and should
be butt jointed. When all items fit correctly, epoxy the stab halves
to the boom again making sure it aligns with the wing platform.
The hinge mechanism is bent to shape using 1/16" piano wire and
1/16" ID brass tubing. The lower portion of the hinge or clevis
attachment is made from 1/8" ID brass tubing soldered to the wire
and flattened. Drill a hole into the brass for the clevis.
The brass tubing portion of the hinge is epoxied to the rear
spar. The fixed portion of the 5/16 x 2" trailing edge is notched
to fit over the tubing and wire. The elevons can now be fitted and
sanded, but not permanently attached (5/16 x 2" light aileron stock
works well for the elevons, if available).
Web and stab spars using hard 1/16" sheet with the grain vertical
(the web should run to half span), then sheet the top and bottom
Push rods: Carve out the push rod holes as shown,
and fabricate the push-rods from 1/4" hard balsa 48" long, with
threaded clevis wire on both ends. The wire length is determined
by the servo installation and hinge connection hole location. When
the linkage is installed and working, one should get ± 40° travel
out of each surface.
Tail Skid: Two 1/2 x 10 x 2" blocks can be cut
to the shape you desire. These are then hollowed out for both linkage
clearance and weight. Next, they are carefully fitted to the tailboom
and glued in place. After final sanding, the tail skid should be
covered with a layer of fiberglass cloth and resin.
Wing Construction-Inner Panels: The 28 inner
panel wing ribs are cut from medium 1/8" sheet, using the diagonal
rib template. The false ribs (5) are also cut from the same medium
1/8" sheet. All inner panel spars are spruce, with 1/8 x 1/2" used
for the center spar, and 1/8 x 3/8" used for the front and back
spars. Medium hard balsa wood should be selected for the leading
edge and trailing edge. Before the wing is constructed, add 3/32
x 3/16" spruce to the back of the trailing edge. This strip is very
effective protection against dings and cuts when building and flying.
Cut two number 3 ribs from 1/8" hard sheet balsa. Do not cut
the ribs apart at each spar location until the spar has been installed
in. a later building step.
Pin the LE and TE down over the plans. Block up the plywood ribs
1/16" when installing to allow for the bottom sheet. Glue the geodetic
ribs in place, noting which are continuous and which are cut in
half when forming the geodetic structure. When the basic structure
is dry, remove from the plans and build other inner panel in a similar
Wing Tips: The tips are built using medium balsa
for the LE and TE, and medium hard balsa for the front and back
spars. The center spar is cut from 1/8 x 3/8" spruce.
Cut the wing tip ribs out of light 1/8" sheet balsa using the
diagonal rib template. Use the same procedure for these ribs as
used on the stabilizer ribs. Some ribs will be slightly thicker
than necessary and must be sanded to the correct contour after the
spars have been installed. The actual construction of the tips is
done in the same manner as the inner panels.
Wing Dihedral: Pin or weight the inner panel
down to the bench and block the tips up with 7" of dihedral. Sand
carefully to fit, then glue together. Add rib 3 (still not cut apart).
When dry, remove from the bench and carefully mark the spar locations
on the tip rib 4. To notch out for the inner panel spars, lay an
aluminum straightedge over the ribs, using the plywood rib notches
and dihedral rib 3 notches for position reference. Cut a 1/8" deep
notch in each rib-repeat this step until all spars are notched at
both the front and back edges. Trim out all notches to 1/8" deep.
Notch the tip ribs in a similar manner, except use the marks on
rib 4, and the notches of rib 3 for spar location reference.
The spars should be glued in place 1/16" above the plywood ribs
to allow for sheeting and be flush with all balsa ribs. Add the
lower spars first. Cut out the spaces between rib 3 sections so
that the 1/8" plywood dihedral braces D, E and F, can be installed.
Next add the upper spars. When the spars are added to the tips you
will find that some ribs are too high. These should be notched deep
enough to allow the spars to be flush with the top of the lower
or thinner ribs. Use a straightedge on top of the spars to make
sure it is flat and not irregular due to incorrect spar notch depth.
The center spar is webbed with hard 1/16" sheet balsa out to the
center of the tips. The front and rear spars are webbed to the tip
dihedral break. The grain of the web must run vertically if it is
to be effective.
Spoilers: Laminate two pieces of 1 x 12 x 1/6"
plywood to two pieces of soft 1/8 x 1 x 12" sheet balsa. Epoxy the
hinges and horn to the plywood. Add the 3/16" ID aluminum tubing
to the center ribs (2) and glue the 3/32" plywood bellcrank and
mount in position. Set the spoiler in place and epoxy the hinge
to rib 6, then glue rib 7 in place. Rib 7 acts as a stop, to locate
the spoiler in the proper position when closed. Sand the upper surface
of the spoiler (1/8" sheet) to match the upper airfoil contour.
Epoxy the Teflon or vinyl tubing in place as shown. Slide the 0.012
braided cable through the tubing and attach it to the spoiler horn
and bellcrank. Then add a light tension spring to the spoiler, as
shown, to hold the spoiler closed.
The action for opening the spoiler is quite simple. The servo,
mounted on its side in the center section, pushes two rods out,
which press against one end of a 3/16" dowel located inside the
aluminum tubing of the inner wing panels. The dowel pushes against
the bell crank, which pulls on the cable and opens the spoiler.
This system requires no actual center section-to-wing hookup. The
worst problem that can occur in flight is, if the wings slide out
on the rods a bit, the spoilers will only partially open when activated.
Wing Center Section: Slide four of the number
2 ribs on four brass tubes cut to the correct length (the center
tube is two pieces, to allow for the servo mounting in the middle).
Place on the plan and block up 1/16" to allow for sheeting. Coat
all rib ends with glue and place the LE and TE in position. Hold
them in place with pins or weights. When dry, remove from the plans
and add all the spruce spars. Web the spars with 1/16" hard wood
or plywood. Next install the servo and drill holes in each rib to
allow the clevis rod to pass through and mate with the inner panel
aluminum tubing/spoiler assembly. The entire top and bottom is sheeted
with firm 1/16" sheet with only a cutout in the bottom sheet for
Wing Assembly: Position the brass tubes into
the inner wing panels. Check alignment with the center section tubes.
If all aligns, epoxy the tubes in place. Block off the end of each
tube with a 1/2 x1" piece of plywood, so that the tubing cannot
be pushed into the wing. The tubes should then be webbed top and
bottom with 1/16" spruce or plywood.
A beautiful study in sailplane aesthetics, the Eclipse is elegant
and spirited in flight.
Assemble the wing, using six rods of piano wire 3/16" dia. approximately
7" long. Check out the spoiler mechanism and, if all works well,
sheet the top and bottom of the inner panels with firm 1/16" sheet.
Shape the leading edge and ribs to remove any burrs or rough spots
on the wing surfaces.
Covering: The covering is accomplished with
the help of the Bank of America and four rolls of MonoKote. All
surfaces are covered with normal MonoKote procedures. Cover movable
surfaces before installation. The original Eclipse was covered with
red MonoKote on the top surfaces and orange MonoKote on the bottom.
Chrome mylar trim is used on the leading edge for visibility and
directional reference. You will be surprised how effective these
strips are when the plane is a dot in the sky - and with this plane,
Flying: Balance the plane to obtain a flat,
straight glide with all trim adjustments set in neutral. Use the
CG shown on the plans for a reference. Balance may take as much
as 12 ounces of lead, depending on your construction weight and
With this flight setup, you will find full right or left trim,
along with full up trim, will give you a nice circle for hands-off
Good luck with your Eclipse and, if you have half as much pleasure
from your plane as I have, you will agree that the work building
it was well worth it.
<click for larger
<click for larger
The AMA Plans Service offers a full-size
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