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Slingsby T-37 Skylark Manual

1/3-scale

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1/3-Scale Slingsby T-37 Skylark ~ by Peter Goldsmith Designs
Wings
• Wings are constructed in four panels. Panels
are joined by laminated plywood joiners with
the inner two panels permanently joined
around a center laminated rib.
• Locate the plywood center wing joiner parts
and the center rib plywood and G10 parts.
Stick T-pins through alignment holes and
epoxy parts together.
The center and outboard wing joiners are three
pieces of plywood laminated together. The center
rib is three pieces of plywood and two pieces of
G10 laminated together with the G10 added to
the outsides of the lamination.
• Locate all the wing ribs and shear web parts,
break them out of the laser cut sheets, lightly
sand off the nubs, and group them in order.
This helps ensure that you have all the
necessary parts identified and speeds the
build process.
• Peter recommends NOT build the wing
panels over the plans, but rather to use the
plan as a reference. The reason is the paper
plans can change dimension with time and
humidity causing a mismatch between the
parts and the plan. Establish and straight
reference line on your building surface and
scribe a perpendicular reference line at one
end. Align the lower spar with the reference
line running down the worksurface and the
first wing rib with the perpendicular
reference line.
V 1.10 11/14/2018
1

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Summary of Contents for Slingsby T-37 Skylark

  • Page 1 1/3-Scale Slingsby T-37 Skylark ~ by Peter Goldsmith Designs Wings • Wings are constructed in four panels. Panels are joined by laminated plywood joiners with the inner two panels permanently joined around a center laminated rib. • Locate the plywood center wing joiner parts and the center rib plywood and G10 parts.
  • Page 2 • For many kit builders, building over the plan is preferred…so we used the plan just to see how well things would go. First step is to get the lower spar pinned into place. • Locate all the ribs and shear webbing for each wing.
  • Page 3 • Continue out board adding a shear web and then a rib, another shear web and then another rib. Add the spoiler servo mount plate being very careful to get the correct orientation. Add the TE parts along the trailing edge (they are like mini shear webs). The servo mounts are made to exactly fit the Spektrum A7020 or A7050 thin wing servos.
  • Page 4 • Do not use the rubber grommets on the servo mounts. Servos are hard mounted directly to the servo mounting plates. Best to program your radio, attach the servo arm, and adjust for the correct travel of the spoiler servo. Also make sure there is enough clearance around the servo arm for the spoiler door stirrup to retract down into the wing.
  • Page 5 • We did not build the wing tips over the plan. Instead, we use the reference lines on our workbench. Take time to get the spar, first rib, and shear webs properly aligned. The wing tip joiner was wrapped in wax paper and used as a spacer.
  • Page 6 • Add top spar, top trailing edge sheeting, and 3/8” square leading edge. Shape the top of the leading edge to follow the contour of the ribs. Using a razor plane speeds this process. • Lay the top wing sheeting over the wing and mark the root and tip overhang.
  • Page 7 • Flip the wing over, install the aileron servo extension cable and then add sheeting as was done on the top side. The plywood end cap rib is added, and the leading edge is sanded round. After a final sanding to level out any uneven joins, the wing is now ready to cover.
  • Page 8 • First, add a strip of covering about 3/4" wide to the top edge of the aileron. Then, holding it place against the wing in the down position, seal the strip to the wing. Then flip the aileron over onto the top of the wing and apply a second strip of covering over the bottom side of the hinge line.
  • Page 9 engages the music wire stirrup to hold the spoiler closed. Springiness of the covering hinge naturally wants to close the spoiler as will the air pressure against it in flight. There is no direct connection between the servo arm and the spoiler blade. Stab/Elevators •...
  • Page 10 • Pin the stab TE to a straight reference line on your workbench. Note the predrilled holes for the hinge points. Also note the tabs that hold the hinge line level with the workbench surface. Laminate the center S1 & S2 ribs together and glue the elevator servo mounting plates between ribs S3 &...
  • Page 11 • Install the elevator servo arm and screw it to the servo mount plate. (again, this is a good time to program your transmitter and to set the servo travel for the elevator servos). Do not use the rubber grommets, hard mount the servo directly to the plywood plate. •...
  • Page 12 • Elevators are constructed in a similar manner. Use a scrap piece of 1/16” balsa to make a spacer between the E2 ribs. This forms the slot for the G10 elevator control horns. Once constructed, add the balsa donuts to the inside of hinge point holes. Add the LE to the elevator halves and sand it to a V along the center hinge line.
  • Page 13 Fin/Rudder • Locate all the parts to complete this section. The ribs have build tabs that allow the structure to be assembled on a flat surface without the need for special shims. The leading edge of the rudder is like the elevators. There are two pieces with pre-drilled hinge point holes.
  • Page 14 • Dry fit the parts together and make sure the slant of the ribs is correct according to the plan. Once you are sure, tack together with thin CA. • Stand this structure on the fin tail post using the etch lines to place the ribs and make sure the ribs are centered over the centerline of the hinge point holes.
  • Page 15 Fuselage • Fuselage has a top and bottom 1/4" square longerons that run its length. These are constructed by scarfing together 48” balsa and basswood sticks. • Using the plan as a reference, transfer the position of the formers onto a pair of the longerons.
  • Page 16 • Once the longerons are set, pins are used to lock the fuselage sides in place on the workbench surface and 1/16” x 1/2" balsa strips are added to the outside of the 1/4” square longerons. This creates a lip for the 1/4" square sticks that make the aft fuselage formers.
  • Page 17 • Continue working forward adding the cross pieces and then the diagonals to form the fuselage truss work. Use weights and builder’s triangles to keep fuselage sides perpendicular to workbench surface. • Add the top fuselage formers F15 – F19 and then top 1/8” x 3/8” basswood spine between F15 and F7.
  • Page 18 • Separate the fin from the fuselage and add pieces of 1/16” scrap balsa to the lower edge of the fin sheeting. When the fin assembly is reinserted into the fuselage, the lip created by adding the scrap balsa makes the joint between the plywood fuselage sides and the fin sheeting sides blend together with a smooth joint.
  • Page 19 other and cause the nose to be offset to one side. If this happens, use a razor saw to make partial cuts through the 1/4" longerons on the side resistant to bended. Make enough cuts to gain symmetry between the sides. •...
  • Page 20 • Add the battery box panels, the tow hook mount plate, and the rudder servo mount. Make sure servos fit properly in these mounts before gluing them in place. • Motor battery is an E-flite 4S 30C 14.8V 4000mAh LiPo pack. •...
  • Page 21 • Add F10 and F11 parts to the top of the fuselage. Set completed wing center section in place and check for fit in wing saddle. Once satisfied, drill through wing into F10 to make wing bolt attachment. F15 is laminated to the bottom of F10 and blind nuts are added to the bottom side of F15 for the wing bolt attachments.
  • Page 22 Flat sand the space between the top stringer and fuselage side and add another section of the pre-cut 1/32” plywood sheeting. Continue on back with the next section of 1/32” plywood sheeting and then up between the wing mount and angled side. •...
  • Page 23 • Glue Install the G10 control horns into the slots on both sides of the rudder. Install double arm on rudder servo and run cable for the rudder pull-pull system. • This is also a good time to decide where and how you will mount your receiver, receiver battery, switch, and Electronic Speed Control for the motor.
  • Page 24 • We added a receiver mounting plate to the F4 former below the rudder servo mount. You will also need to run the servo extension wires for the elevator servos. We used rubber grommets in the holes we made for the wiring to pass through. •...
  • Page 25 • Fit access door to fuselage bottom and use a screw to hold the door shut. Use scrap pieces to box in both ends of the keel and sand off the sharp corners. • Laminate the balsa nose blocks together and then add them to the front of the fuselage making sure that there is clearance around the motor.
  • Page 26 • Do this on each of the flat sides. • Make a recess in the final nose block to fit over the front of the motor. Also make an air inlet to allow cooling air to be drawn through the motor. •...
  • Page 27 Takeoff Dolly • Plywood parts are included to construct the takeoff dolly. You will need a pair of 4-1/2” wheels to complete. • Drill a hole in the bottom of the keel to locate the dolly as shown on the plan. This needs to be a very loose fit so dolly will easily fall away on takeoff! Pilot Figure is available through www.petergoldsmithdesigns.com...
  • Page 28 Completed Prototype built by Peter Goldsmith (Caroline Goldsmith holding model) Completed Kit #1 built by Jim Dolly (view build thread on www.forum.scalesoaring.com) V 1.10 11/14/2018...
  • Page 29 Specifications: • Wing Span: 188” (4.7m) • Fuselage Length: 85” (2.18m) • AUW: 12-13 pounds • Airfoil: Modified SD3021 Items Used to Complete Model Spektrum Servos: • A5060 (SPMSA5060) (note: need one of these for the rudder)* • A6320 (SPMSA6320) (note: need one of these for the tow release) •...