Here is another sailplane that, like the
Aquila, really appealed to me back when I first saw it in the
August 1974 edition of American Aircraft Modeler. The Astro-Jeff's 12'-7" (151") wingspan and 1370 sq.
in. of wing area, was too much for my 16-year-old wallet. The cost to build and cover it, and then the
launch system needed was way more than what I was accustomed to compared to my Standard Hi-Start and
72" and 99" gliders (the 2-meter class hadn't been created yet).
I had forgotten about the Astro-Jeff until a few years ago when I ran across a re-kitting of it byMr. Jim
Ealy of Vintage Sailplaner. He offers
a short and full kit of the Astro-Jeff with a fiberglass fuselage.
Maybe now that I have a lot more money (don't I wish), someday I probably will finally build one
of my own.
Grand Champion of the 1973 SOAR NATS, this soarer has set a standard of excellence for sailplanes. It's
rated among the top RC glider designs of all times.
by Jerry Mrlik
The Astro-Jeff is the
result of an attempt to design an attractive looking, large RC sailplane which would have good thermal
qualities, long range, good maneuverability, and a device to aid its pilot in making successful landings.
Larger sailplanes seem to be scoring better and, as the soaring sport progresses, more fliers are using
the big gliders to obtain the higher levels in LSF.
great deal of thought and effort have gone into the design of the
Astro-Jeff. Primary consideration
was given to strength versus weight, and every attempt was made to optimize the usual design compromises.
The biggest question was what to use for wing wires in a sailplane having close to 1400 sq. inches
of wing area. Having witnessed numerous large sailplanes fold their wings on the tow, while using 125-lb.
test line, I decided to design a wing system that would exceed the tow line requirements. Making the
necessary strength calculations, I decided on the 1/16 x 5/8" spring steel cross section. The advantages
are several (greater strength with less weight): (A) The modulus of this section is the equivalent of
using six pieces of 3/16" diameter music wire; (8) The weight savings are in ounces; (C) The spring
steel blade, when used on edge, has the flexibility in the fore and aft direction equivalent to one
piece of 3/32" diameter music wire.
I feel that item C is very important, since this flexibility reduces the chances of wing damage in
a hard landing. The steel blade acts as a shock absorber. Using round diameter wires to take the towline
forces means that the wing must be equally strong in all directions. The
Astro-Jeff wing is designed
to take the forces through the spars, then to the ply box which houses the nylon wing blade channel.
This method requires no extra spars or ply ribs. The airfoil is a modified Cirrus section, flat bottomed.
The spoiler mechanism is simple, with no worry about linkage disconnection on a hard landing. No
hook-up is required when assembling the wing. The spoilers are located on the wing outboard of the wing
wash on the elevator, in order to prevent stab flutter.
The rudder can easily be removed for transporting, adjusting or repairs. The canopy attachment is
simple, positive and very reliable. All controls are internal, with no stress risers in the fuselage
and, therefore, minimum drag. The scale pilot gives the sailplane a realistic appearance.
The grades of balsa and plys indicated on the plans have been carefully selected, and should be followed
explicitly. Carefully review the plans, and read all the notes.
is elegant in the air, floating on the lightest lift, yet solid in turbulence.
can be built with either a balsa or epoxy fuselage. The plans for either version are available from
AAM's Plan Service. (See page 86.) The Astro-Jeff is available in semi-kit form for $48.00, plus shipping (check your local
UPS office for the rate under 25 lb., and exceeding 84 inches combined length and girth), from Jeff's
Models, 6730 Halyard Road, Birmingham, Michigan 48010. The semi-kit includes: (A) One assembled epoxy
fiberglass fuselage; (B) One plastic canopy and dash; (C) Two spring steel wing strut blades (WSB);
(D) Two nylon wing strut channels (WSC) with machined groove; (E) One fuselage strut box (FSB), machine
grooved and assembled.
Fuselage: The epoxy fiberglass fuselage comes with both halves assembled. Sand interior
areas for epoxying, per instructions on plan. Use Hobbypoxy No. 1 throughout, unless otherwise noted.
Cut out the foam bulkhead, then epoxy the antenna Nylaflow tubing in the bulkhead, and provide clearance
for the rudder push rod and a hole for the elevator Nyrod. Epoxy the bulkhead to fuselage. Fit and epoxy
the 1/4 x 1/4" spruce and 1/8" ply reinforcements. Cut out a slot for the tow hook, and epoxy the maple
tow hook mounting blocks. Add the 1/8" Sig Lite-Ply support for the elevator Nyrod on the centerline
of the fuselage. Trim the rear of the fuselage (per section H-H) and fit FRP. Epoxy the ply reinforcements,
as shown in section A-A, making sure that the right side is longer than the left, and leave space for
FRP. Place the VFJ jig in place, and fit 4F. Epoxy 3F, 4F and FRP in place. Drill out hinges for 1/32"
hinge wire (RHP) and epoxy each in place.
After fabricating ECHP, drill a 1/8" hole for ECHP, making sure the hole is in proper alignment (check
by inserting a 1/8" tube and slighting from front). Install ECHP and mark the location of the 2-56 screw.
Drill and tap for same. Fabricate ECH, and slot out the front hole in the vertical fin to match ECH.
Using the plan for templates, cut out two 1/8" ply root ribs. Clamp together and drill location of
the two screw eyes with a 1/16" drill. (These will be used as dowel holes and to locate the remainder
of the holes to the fuselage.) Drill the other holes (1/8" and 3/16") and cut out the 1/16 x 5/8" slot
for the steel wing blade. Make this a close fit, so that proper alignment can be maintained. Mark the
ribs left/right and place on the fuselage. Line up the bottom front edge and transfer the two 1/16"
holes. Insert pieces of 1/16" wire (dowels) to hold and locate the ribs to the fuselage. Drill the 1/8"
and 3/16" holes. Drill 1/16" holes at the top and bottom of the 1/16 x 5/8" slot. Remove the ribs, mark
the opening for FSB (use 1/16" holes for reference) and cut out. Do the other side and insert FSB through
the fuselage. (Note: The four center round-head screws can be removed and replaced. After alignment,
trim the width of FSB to fit the fuselage width.)
The radio compartment is spacious enough for any gear. The installation on the left
uses a different method of spoiler actuation than the one shown on the plans, The spoiler linkage used
in the Astro-Jeff is very
simple to install and reliably accurate.
Place root ribs on the dowels in the fuselage and insert WSB through the ply rib and into FSB. Support
the fuselage by placing blocks under WSB (both sides), and check alignment of the fuselage from the
front to be sure that the fin is vertical. Tack-glue FSB to the fuselage with epoxy. Do not epoxy the
ply ribs to the fuselage. When dry, remove blades, dowels and ribs.
Drill a 3/16" hole in the 1/2 x 3/4 x 5/8" pine block and locate it to the fuselage (use 3/16" tubing
to check squareness). Tack-glue in place with epoxy. When dry, epoxy the pine block and FSB, using fiberglass
cloth, as shown on plan. If eight- or ten-oz. cloth is not available, use several layers of lighter
cloth to obtain the equivalent. Do not skimp on this reinforcement - use plenty of Hobbypoxy NO.2. Remember
to rough up surface of FSB to insure good adhesion of epoxy.
Cut out the slots for the wing rubber bands, add the spoiler Pro-rods, and canopy hold-down block.
Complete the radio installations at t is time. The Kraft installation is shown and can be used as a
guide. There is lots of room left, even for a thermal sniffer.
Rudder: Cut out the ribs, using templates. Pin ribs to plan, glue on the top spar,
LE, top TE and cap strips. When all glue joints are set, remove from plan and cut off the tabs from
the ribs. Glue in the bottom spar, TE webbing and spar webbing. Sand a bevel on the rear TE and glue
in place. Next, glue in the gussets and cap strips, Sand the end faces and add balsa blocks. Shape blocks
per plan. Locate hinge positions and epoxy in place. Drill the hinges and block, and secure by epoxying
in toothpicks. Epoxy the balsa fillers and control horn. Assemble rudder, using RHP, and determine cap
rib thickness between the fuselage and rudder. Remove the rudder, add the cap strips and sand completely.
Three Astro-Jeff's on the author's workbench. Jeff's is in the foreground, Jerry's
is next, and the balsa version is in the back.
Elevator: Cut out the two aluminum templates 4E and 10E.Stack 14 pieces of balsa,
clamp together with screws, and shape ribs. Use the plan templates to cut out ply ribs 1, 2, and 3 (make
two of each). Stack pairs of" ribs and drill 1/8" holes for the brass tubes, making sure that this dimension
is the same as ECH. Make sure that there are tabs on all ribs for building purposes. Pin the spruce
spar to the plan and glue all ribs. (Don't forget to tilt the root rib for dihedral.) Glue TE, LE, top
spar and cap strips. When dry, remove from plan and remove tabs from the ribs. Glue the TE and TE webbing,
after sanding bevel on the 1/16 x 3/16" TE and cap strips. Plug the tube ends and epoxy in place. Glue
on balsa ribs and balsa tip blocks. Contour the" balsa rib to the vertical fin and sand completely.
Center Wing Section: Make aluminum templates for all balsa wing ribs (seven templates
required). Cut balsa for stacking, with appropriate template ribs 1BF through 11BF, 1BR through 11BR,
12B through 22B, and 23B through 37B. (Note: 22B and 23B are identical templates, except for spar width,
so cut accordingly.) Assemble stacks, drill holes and bolt together with long screws, or fabricate screws
using bicycle spokes. Both right and left ribs can be cut together. If both right and left ribs are
cut together, mark alternate ribs Rand L when disassembling stack to maintain a consistent taper. Add
3/16" holes to ribs 1BF through 8BF for spoiler Pro-rod (5/16" from bottom of rib, other dimensions
The tail feathers of this bird are well-proportioned. That large rudder makes for
Fabricate the spar box as follows:
Glue VWR to top and bottom spars. (Glue VWM and five pieces of 1/8 x 3/8" Sig Lite-Ply braces, fitted
to length. Determine thickness of RN by stacking FN and WSC. The total thickness of these, when subtracted
from the 3/8" spar, is the thickness of RN (nylon sheet has a .03 tolerance, and this variation is made
up with RN).
Rough up the top, bottom and rear of WSC (nylon) for better adhesion. Epoxy RN to VWR (between spars),
and WSC to RN (Hobbypoxy 1 or 2). Coat WSB (steel blade) with light oil, or silicone film, and place
in WSC (oil film will prevent epoxying WSB in place). Epoxy FN to WSC and spars. Glue or epoxy VWF to
FN and spars. Place this assembly in position on sheeting, with root rib in place to insure proper alignment,
and clamp the entire assembly (do not glue root rib to sheeting). Slide WSB to insure slip fit. Make
sure VWR/VWF match spars, and check ribs 1 BF through 11 BF for correct height with spar box. Let the
above assembly dry thoroughly, then wrap with nylon thread, per plan.
Pin down and glue bottom
sheeting, cap strips and stringers. Sand spar box assembly square at the root rib and glue to bottom
sheeting. Glue on the false leading edge. Notch the ribs to accept the stringers and glue ribs 1 through
11, front and rear, along with 12B. Cut a strip from 1/8" hard balsa 181/4" long for horizontal webbing
(check height between spars on ribs 12 and 21 for dimensions). Cut these pieces with excess length,
and glue webbing and ribs 12 to 21B in place. Glue in PB1, PB2, and PB3. Cut 22B to fit and tilt, per
plan. Add re webbing (grain is horizontal), gussets and top stringers. Slide WSB into the spar box and
glue in the root rib. Add spoiler linkage and Pro-rod. The inner portion of the Pro-rod should be cut
off to a known dimension, at the root rib, for reference. Use the plan as a guide. When making SW (spoiler
wire), be sure that there is enough clearance in the Ace Swing-in-Keeper to provide a swiveling effect
with the keeper. If using 1/16 wire, drill keeper with a No. 50 (.070) drill. Glue in the screw eye
and. tubing reinforcements, and epoxy the 5/32" OD brass tubing.
Sand a bevel on the underside of the top rear TE and glue. Frame
the spoiler opening with balsa, per plan. Shape the top of the front false LE, and glue all top sheeting
and cap strips.
Spoiler Construction: Cut ply to fit opening, with 1/32" clearance on back and two
sides. Layout holes per plan, stack ply top to top, clamp to board and drill holes. Use Hobbypoxy 1
for gluing spars, while they are clamped to a rigid surface. I recommend a combination square ruler.
Epoxy in place ribs S1, S2, linkage lever rib and spring return rib. Clamp ribs with clothes pins.
The spoiler has the curvature of the wing, so place the spoiler ribs (per plan) for right and left,
to avoid interference with balsa ribs. Insert 1/8" ID brass eyelet and crimp over in the linkage lever,
as shown in enlarged view S. Fit spoiler in wing opening, and notch balsa ribs to miss spoiler spars.
Outer Wing Section: Pin bottom sheeting and TE to plan. Glue cap strips and bottom
spar in place. Mark completed inner wing panel for the 36" polyhedral point, as shown on plan. Block
up 3-1/4" at this point, and glue PB1, PB2 and PB3 to spar and bottoming sheeting, making sure to bend
PB1 as shown. Glue in false LE and ribs. Place washout shim at TE, glue in top spar, and three thicknesses
of vertical webbing. Also glue in the TE horizontal webbing and gussets. Sand the top of the false LE,
and glue on the top sheeting, TE (bevel underside of TE) and cap strips. Sand LE and glue on the hard
balsa LE. Sand the wing tip and glue on the tip blocks. Shape the LE and sand the complete wing. Use
MonoKote or equivalent for spoiler hinge.
Make SS (spoiler swivel) and file a screw, so that the screw clamps SW, but has clearance for the
brass eyelet. Add spring and adjust.
A double wing securing system is necessary, so that the spoiler linkage will remain
in" equilibrium. Any amount of gap between the wing and fuse would delay spoiler actuation, thus causing
an aileron effect in flight.
Balsa Fuselage Construction: Begin by cutting out all bulkheads B1 through B12,
using templates as shown on plans. Using 1/8" Sig Lite-Ply, except B7, which is 1/4" ply. Bulkheads
B3, B4 and B5 include shaded portion for initial build-up on the jig. Mark a vertical centerline on
the bulkheads, and drill out the two holes for attaching to its corresponding jig piece (see charts
for dimensions). Make jig from any grade commercial plywood, making sure that the vertical members J1
through J8 are 5/8" wide. Mark the vertical and horizontal centerlines in the J pieces, and layout the
top hole (see chart for dimensions).
Drill a clearance hole, and assemble the bulkhead with bolt and nut, lining up the two matching vertical
centerlines. Tighten the bolt, clamp bulkhead to jig piece and drill bottom clearance hole (using bulkhead
as a jig). Repeat procedure for all eight bulkheads and jig pieces. Disassemble bulkheads. Mark jig
base with fuselage centerline. Glue and nail jig together, making sure that the jig is square and that
the centerlines are aligned. Use plan for spacing J1 through J8, making sure that the angle of J7 is
maintained. This bulkhead sets up the incidence in the wing. Let the jig dry.
Cut the 3/4" triangular longerons with a razor saw in two directions (perpendicular to its length,
as shown on plan) so that it will bend to the contour. Make right and left longerons. Splice and glue
the 3/8", 1/2" and 3/4" triangular longerons, leaving the front long (trim it later). Leave the right
rear bottom longer for the angle at the rear. Cut out B22-L, B22-R, B13 and RTG (gauge). Glue B22-L
and B22-R to its 3/8" triangular stock (the bottom is flush). Trim the 3/8" and 1/2" triangular stock
to accept B12, B13 and RTG. Glue B10, B11 and B12 to the plan view, and tack-glue RTG. Cut out B15 and
glue B13 (with B15) .to B22-R and B22-L.
Place jig on plan view, lining up centerline. Anchor it to the building board. Assemble bulkheads
B1 through B8 to jig, with screws and nuts. Glue in the 3/16 x 3/16" front stringers. Cut out and glue
B19 in place, and glue 3/8" triangular stock at the front. Make aluminum clamps and epoxy F5B to B7.
Clamp should be inside the outer edge of B7 by at least 1/8", leaving room for RB 1. Check alignment
by inserting W5B.
Place jig blocks at the rear of the fuselage and at B 10 (see side view for dimensions). Glue the
bottom assembled longerons to B7 and B8 (hold in place with rubber bands) and place on the two jig blocks.
Glue the top, right and left longerons (trim like the bottom ones) to B13, B12, B11 and B10 (clamp around
with rubber bands). Glue B9 and clamp. So far, the triangular stock should be flush with the bulkheads
on all sides. Continue gluing and clamping the triangular stock to the bulkheads, while fitting it at
B1. Trim the inside edge, per section B1. Cut out and glue B17. Glue 3/16 x 3/8" spruce to B8. Glue
1/32" sheet filler in front of B22-R/B22-L, and sand to plan taper when dry. Do not remove from jig.
Cut out, add taper and glue 51-L/51-R (the taper goes outside) to B1 through B8 and the 3/4" longerons.
Cut out, add taper and glue 54-L/54-R to B17, B6, B7, B8 and the top 3/4" longerons.
Add the elevator Nyrod, fitting it at the rear and through B13. This is a good time to think about
the antenna too. You can epoxy a 3/16" 00 Nylaflow tubing the full antenna length, while putting the
actual antenna inside a 1/8 00 Nylaflow tubing. Tie a knot in the antenna wire end and slip this through
the other tubing.
Cut out 52-L/52-R, the two pieces of 55, 53-L/53-R and the two pieces of 56 per template shown and
glue to jigged fuselage in the sequence noted above, Cut out RBIs along with the wing root ribs, as
shown on plan sheet two. Drill corresponding holes, while stacking these four pieces to insure proper
alignment. Cut out, drill hole and epoxy the 1/2 x 3/4 x 5/8" pine block used for the spoiler, as shown
on plan sheet one, Fill in the space between 56 and RBI with 1/8" balsa sheet, fit and glue.
5and the rear of the fuselage. Remove RTG, cut out B14 and glue. Glue the four pieces of 1/16" ply
to B22-L/B22-R and B14. Drill a 1/8" hole for ECHP (see section K-K). Fabricate ECHP and assemble. Mark
hole location and drill and tap for 2-56 screw. Cut out and glue B16 and LE of fin.
Saw the upper end of J 1 to J8 and remove the top of the jig. Remove all screws holding the bulkheads
to the jig. Remove fuselage by lifting vertically.
Spoilers deployed, the Astro-Jeff becomes a real target drone, capable of zeroing in on the landing spot.
Cut a piece of 1/4 x 1/2" to the required length for anchoring your tow hook. Add blind nuts and
glue block to B6/B7.
Cut out 5B1, 5T1, 5B2, 5T2, 5B3, and 5T3 per plan template, and glue to fuselage in sequence noted
above. Glue in the 1/4" gusset and 1/16" sheet on vertical fin. Add extra 1/16" sheet at the base of
the fin for a fillet (see section H-H).
Fill in space between 53-L/R and RBI with 1/8" balsa sheet, fit and glue. Glue balsa blocks in the
space at the front and rear of RBI and the fuselage. Glue 1/8" balsa on the top side of nose. 5and the
canopy opening and glue B21, B20 and B18. Drill hole in B1/B20 and epoxy tubing in place. Hollow out
the pine nose block (can be made in two pieces and glued) and shape to outline of B1 section prior to
Get a big basket and start shaving. I used a small X-acto razor plane and very course sandpaper block,
while keeping an eye on the various sections B 1 through B12. You can see the different sheets and triangular
stock change with the eye. It is really fun now. For the fillets, use sandpaper on a dowel. The larger
the dowel, the larger the fillet.
Cut out the tow hook opening and fiberglass with Hobbypoxy 1 or 2 and three-oz. cloth. Remove shaded
area from B3, B4 and B5 by sawing. Make canopy, radio installation, and push rods and you're ready to
apply the finish. I'll leave the rest to your preference.
Finish: The finishing method used was MonoKote on all flying surfaces, and the fiberglass
fuselage was painted with Ditzler Acrylic Lacquer.
Before you go to the the flying field, check all surfaces for warps, and assemble the e rudder, stabs
and wing. Check all controls for proper function and make sure that the linkages are not sloppy. Add
nose weight until the model balances at the CG shown. Make sure that you 1-1/2° down elevator when the
transmitter is at neutral and the trim is centered. Place the tow hook approximately 3/4" forward of
Disassemble the model, pack up and head f or the field. Before flying, range check the equipment
again. You have made a new installation, so don't rush it-make sure to try your controls again! Oh yes,
do you have the frequency pin? If there is a slight breeze, don't use a hi-start for the first flight,
since you have not optimized the tow hook position. If you have a strong arm, give it a strong throw
and check it out. When you're satisfied, hook it up to the winch line, point the nose up about 300,
tighten the line and keep standing on the winch to obtain sufficient height before pulsing the winch
and release. Get the model to fly level hands-off and see what it's doing by checking right and left
turns. Smooth out the turns and you're on your way. Make long approaches on the initial landings, until
you get the feel of it. Make several flights, moving the tow hook back to a comfortable towing position.
The Astro-Jeff will really
tow up, so work at it. I would recommend that when you're ready to try the spoilers, you don't start
at low altitude. Instead, start up 25 to 30 feet, then put the spoilers up slowly and be ready to apply
up elevator. Play with coordinating the spoiler with up elevator, and the spots will comes with practice.
If you have any questions or comments, contact me through AAM.
<click for larger version>
<click for larger version>
All rights to the Astro-Jeff
are now owned by Mr. Jim Ealy. He has done the soaring world a great service by making this exceptional
craft - available in kit and short-kit form at the
Vintage Sailplaner website.
The AMA Plans Service offers a full-size
version of many of the plans show here at a very reasonable cost. They will scale the plans any size for you. It is always
best to buy printed plans because my scanner versions often have distortions that can cause parts to fit poorly. Purchasing
plans also help to support the operation of the Academy of Model
Aeronautics - the #1 advocate for model aviation throughout the world. If the AMA no longer has this plan on file, I
will be glad to send you my higher resolution version.
Try my Scale Calculator for Model Airplane Plans.
Posted July 24, 2010