• F3B-style soarer makes an ideal first aileron model. • Strong turbulated wing allows winch launching and low-speed sink. • Rugged, lightweight balsa/life ply construction. READ THROUGH THIS INSTRUCTION MANUAL FIRST. IT CONTAINS IMPORTANT INSTRUCTIONS AND WARNINGS CONCERNING THE ASSEMBLY AND USE OF THIS MODEL. WARRANTY Dynaflite guarantees this kit to be free from defects in both material and workmanship at the date of purchase.
Congratulations and thank you for purchasing the Dynaflite Bobcat. Once you have learned the basics of thermal flying, the Bobcat is an ideal "second" sailplane. With its "flat" wing and ailerons, the Bobcat is more maneuverable than beginner, two-channel, rudder-only models so you will be able to chase those elusive thermals more aggressively.
1. You must assemble the plane according to the instructions. Do not alter or modify the model, as doing so may result in an unsafe or unflyable model. In a few cases the instructions may differ slightly from the photos or plan. In those instances the text should be taken as correct. Your Bobcat is not a toy, but a sophisticated working model that functions like a full-size airplane.
REQUIRED SUPPLIES AND TOOLS REQUIRED ACCESSORIES These are the building tools and adhesives that you will need to build your Bobcat. These are the items "not included" with your kit, that you will need to purchase separately. Items in parentheses (OSMG2691) are suggested part numbers recognized by distributors and hobby shops and are listed for your ordering convenience. GPM is the Great Planes® brand, TOP is the Top Flite® brand and HCA is the Hobbico® brand.
• When you see the term "test fit" in the instructions, it means you should first position the part on the assembly without using any glue. Slightly modify or "custom fit" the part as necessary for the best fit. • Whenever just "epoxy" is specified, you may use either 30-minute epoxy or 6-minute epoxy. When 30-minute epoxy is specified, it is highly recommended that you use only 30-minute epoxy because you will need either the working time and/or the additional strength.
Q 5. Sand the glue joint on both sides of the fuselage sides so it is smooth and even. U 6. Place the fuselage sides together and accurately align them. Drill 3/16" holes in the dimples on the left fuselage side for the wing hold-down dowels. All the parts in the following steps are die-cut 1/8" plywood unless otherwise noted. After you remove die-cut parts from their die sheets, remove slivers and die-cutting irregularities with a bar sander and 80-grit sandpaper. U 7.
D 2. Optional: Drill a 3/16" hole near the bottom of bulkheads A and B for an antenna guide tube (not included). The hole in bulkhead B must be slightly off center so the guide tube will not interfere with the tow hook block. Q 7. Use a straightedge and a ballpoint pen to extend the centerline on the top view of the fuselage plan an additional 9" from the rear of the fuselage on the plan. Cover the top view of the plan with wax paper from bulkhead A to bulkhead D. LJ 8.
U 11. Remove the fuselage from your building board. Sand the bottom so the formers and fuselage sides are even. Sand the top of the fuselage sides and the crutch so they are even. LJ 15. Sand the bottom ply sheet so it is even with the fuse sides. LI 16. Glue the 1/4" x 3/8" x 4-1/4" basswood tow hook anchor to the inside of the forward fuse bottom, between bulkheads A and B with medium CA. Note that the 1 /4" side of the anchor is the side that contacts the fuse bottom. Q 12.
tip of the fin and in the cross braces. Test fit the tube to make sure the grooves are deep enough. U 8. Glue the tube in place with medium CA. Sheet the left side of the fin the same way as the right. Q 9. Sand the tip of the fin so it accurately matches the plan. Round the leading edge. U 10. If you will be building a functioning rudder, mark the location of the hinges on the fin and cut the hinge slots. Q 2. Place a sheet of wax paper over the rudder and fin plan.
Q 4. Glue the front hatch tongue to the bottom of the hatch so half of it protrudes past the front edge of the hatch. d 3. Apply 30-minute epoxy to the base of the fin, the top of the fuse sides and all other mating surfaces. Insert the fin into the fuse. Clamp the fuse sides to the fin TE with a clothespin. Push a T-pin through the top sheeting into the LE to hold the front of the fin down. Immediately proceed to the next step. U 5.
Skip to step 11 if you will not be building the functional rudder. Q 8. Cut a 36" outer pushrod guide tube to a length of 29". Use coarse sandpaper to roughen the outside so glue will stick. Slide the tube through the exit slot in the rear of the fuselage until the front of the tube extends past bulkhead C the same amount as the elevator guide tube (this should be about 2"). Make sure the rudder guide tube does not interfere with the fin LE or the elevator guide tube.
Q 2. Use the remainder of the 3/16" x 1/4" x 24" balsa s t i c k you used to build the fin and an additional 3/16" x 1/4" x 24" balsa stick, to build the rudder framework. Cut the pieces to the correct length. Pin them in their location over the plan and glue them together with medium CA. U 15. Make sure the front of the fuselage sides, top and bottom are flush with the front bulkhead D. Securely glue the balsa nose block in position with medium or thick CA. IJ 3.
HINGED RUDDER Perform steps 10, 11 and 12 only if you are building a fixed rudder. FIXED RUDDER 1/16" X 1/2" BALSA SHEETS EVEN WITH AFT EDGE OF "V" ON LEADING EDGE OF RUDDER 1/16" X 1/2" BALSA SHEETS EVEN WITH LEADING EDGE OF RUDDER Q 10. Cut two 1/2" x 7" strips from the remainder of the 1/16" x 3" balsa sheet you used to sheet the fin. Glue the strips to both sides of the leading edge of the rudder with medium CA so the front edge of the 1/16" strips are even with the leading edge of the rudder. Q 8.
Q 3. Use a hobby knife and a straightedge to bevel one end of the 3/16" x 1-3/8" x 3-3/4" balsa sheet to make the stab center. Glue it to the stab LE and TE with medium CA in the location shown on the plan. Q 4. Cut the stab ribs from a 1 /16" x 3/16" x 24" balsa strip. Glue them in position with medium CA. LJ 14. Make two fin tip fillers from leftover 1/16" balsa sheeting.
Some modelers prefer to glue the stab to the fin after they cover them with MonoKote® film. If this is your preference, perform the following steps but use T-pins to temporarily hold the stab to the fin instead of permanently gluing it in position. Continue building, skipping the rest of the steps that can't be done without the stab joined to the fin. Cover the fin, fuse and stab with MonoKote film after the parts have been final sanded.
LJ 9. If you are going cover the model before you glue the stab to the fin, set the triangle fin reinforcements aside until you are ready to glue them in place after you cover the fin and stab. Otherwise, glue the stab reinforcements to the stab and fin at this time. A nice-looking fuselage, isn't it? That T-tail is interesting and pleasing to look at. Clean up your workbench, vacuum the floor and get out the wing plan. LI 4.
1/8" X 3/8" BASSWOOD SPAR RIB NO. 1 1/16" VERTICAL GRAIN SHEAR WEB Q 8. Pin a 1/8" x 3/8" x 30" basswood bottom spar over its location on the plan. Do not attempt to insert the T-pins through the spar (basswood can be pretty hard stuff). Insert them over the spar in a criss-cross fashion as shown. Q 9. Pin one of the 1/16" x 1-3/8" x 30" balsa trailing edge sheets over its location on the plan. Q 10. Mark the bottom main spar and the bottom TE where the three #1 ribs contact them.
U 22. One at a time, remove the T-pins from the bottom TE sheeting. Replace them in the rear of the ribs to hold the aft end of the wing panel to your building board. This will allow you to glue the top TE sheeting in position without interfering with the T-pins. Q 23.
ribs - to the bottom spar and ribs with medium CA. Set the outermost shear web for the last set of #2 ribs aside for now. Remove the crossed T-pins that are in the way, but reinstall them through the shear web after you glue it in place. Q 26. Cut and glue five shear webs in the right side of the center wing panel the same way. Q 27. Position the 1/16" x 1-3/8" x 30" balsa upper TE sheet on the ribs. Mark the location of the 1/8" x 3/16" basswood stick and cut a notch in the TE sheet.
Q 8. Cut the 2" basswood grooved slider block into two 13/16" long pieces. t-1 4. Cut two more 1 /4" x 1 /4" tabs and one 1 /4 x 2" strip to secure the hatch. Glue the 2" strip to the top (inside) of the hatch. Glue the 1/4" tabs to the 2" strip. Q 9. Make the servo tray from the remaining 1/16" plywood sheet. For now, cut only the outside edges. Do not cut to fit your servo until the next step.
TRIM 1/16" FROM THE TOP OF RIBS 6 AND 7 BEHIND THE SPAR Build the right wing panel first so your progress matches the photos. 1/16" REMOVE 0 1. Arrange the wing plan so the right wing panel is over your building board. U LJ 2. Mark ribs #3, 4, 5 and 6 where the aileron pushrod guide tube crosses them. Cut or drill a 5/32" hole 3/8" above the mark on the ribs. Q Q 3. Cover the plan with wax paper. Pin a 1 /8" x 3/8" x 24" balsa bottom outer spar over its location on the plan.
Q Q 9. Glue the 5/16" x 24" hardwood dowel leading edge to the ribs. Use the dihedral gauge to make sure rib #2 it is at the correct angle when you glue the dowel to it. Q Q 10. Glue the 1/8" x 1/8" x 24" outer turbulator spars in the notches of the ribs. Use the dihedral gauge to make sure rib #2 it is at the correct angle when you glue the spars to it. Q Q 11. Make six shear webs from the 1 /16" x 3" x 24" balsa sheet to fit between the sets of ribs from #2 out to #7.
Q Q 1. Use a razor saw to trim the spars and leading edge dowel so the ends are nearly flush with rib #2 at the root of the panel and rib #10 at the tip of the panel. Sand the ends of the spars and leading edge dowel flush with the root and tip ribs. Q Q 2. Sand the end of the 5/8" x 1-3/4" x approximately 18" balsa aileron so it accurately matches the end of the trailing edge stock you glued to the wing. U U 5. Use a hobby carving knife or a razor plane to roughly carve the tip to the approximate shape.
U 1. Sand all three wing panels with fine-grit sandpaper to remove glue bumps. Blend all the ribs to the spars, LE and TE. Smooth all surfaces. U 6. Test join the wing panels with the dihedral braces and adjust the slots in the ribs or the length of the braces so the spars and LE's align and the wing panels fit together without gaps. U 2. Use a small 90 degree triangle or square to draw a 1/8" wide slot centered between the spars on the #2 ribs on both outer wing panels.
U LJ 2. Remove the clamps and separate the panels. Lay a piece of wax paper on your building table. Mix a batch of 30-minute epoxy. Coat the joining surfaces with 30-minute epoxy. Join the inner wing panels with the dihedral brace. Refrain from using excess epoxy so the shear webs will fit later. Place the wing on your building table. Immediately proceed to the next step. o o 3. Place a weight on the center section to hold it down. Prop up the outer panel so the tip is 3/4" above your table.
Q Q 10. Cut the threads off a Great Planes 2-56 (1/16") Threaded Coupler (included with the Great Planes Flexible Cable Pushrod set) so that 5/16" to 3/8" of the threaded portion remains. Silver solder the threaded coupler to one end of the aileron cable. Thread the coupler all the way into the dual end ball link (included with this kit). Q Q 4. Glue a 1/16" balsa strip to the inside of the sheeting on both sides of the slot to keep the sheeting from splitting. Q Q 11.
Q Q 14. Silver solder the clevis to the cable. If you find it difficult to cut the cable with wire cutters, use a MultiPro with a cut-off wheel or tin the cable in the area where it is to be cut with wire cutters. LJ U 15. Place the control horn on the aileron. Drill 1/16" holes in the aileron for the horn mounting screws. Remove the aileron and use a pin to poke holes in the aileron where the control horn will be mounted. Saturate the area and the holes for the horn mounting screws with thin CA.
Back to the fuselage for a little while. It will soon be time for covering! Q 1. Cut two 1 /4" x 4" strips from leftover 1 /8" plywood. Glue them together with medium CA to make the servo rails. U 2. From the strips you glued together, cut two servo rails that will fit between the fuselage sides in the servo compartment. 0 3. Position your servo(s) on the rails in the fuselage as shown on the plan.
U 11. Glue the outer pushrod guide tubes to the bulkheads with thick or medium CA. Q 12. Wrap your receiver and battery pack in foam rubber. Mount them in the fuselage where shown on the plan. Mount the on/off switch in a location that will not interfere with the pushrods or the radio system. Q 1. Inspect the wing, fuselage and tail surfaces for glue joints that don't look strong. Reinforce them with thin or medium CA.
Fuselage: 1. Bottom* 2. One side, then the other 3. Top forward, then aft of the hatch 4. Top aft of wing 5. Hatch * Many modelers cover the forward bottom section of the fuselage with two layers of covering or glass cloth and paint the forward bottom section for better protection during landings. U 2. Lay the center section of the wing on your building table. Place weights on top of it to hold it down. Twist the trailing edge upward while you heat the covering until the wrinkles disappear.
TEMPORARY PIN TO KEEP HINGE CENTERED CUT RUBBER BAND STRAIN RELIEF INSIDE FUSELAGE LJ 2. Join the elevator to the stab with the hinges. If the hinges will not stay centered, stick a pin through the center of the hinge. Remove the pins after the hinges are glued in place. Q 3. There should be a small gap between the control surfaces (just enough to see light). A small gap is desirable so you do not inadvertently glue the parts together. Q 4. Carefully apply 4 drops of thin CA to both sides of the hinges.
U 2. Measure the throws at the widest part of the trailing edge of the rudder and elevator. After a few flights you may change the throws to suit your flight style or the weather conditions. This section is important and must NOT be omitted. A model that is not properly balanced will be unstable and possibly unflyable. Q 1. Accurately mark the balance point on the bottom of the wing near both sides of the fuselage with tape or a felt-tip pen.
If you are at a club site or another area where there are other fliers present, make sure you are not on the same frequency. Learn the frequency control system if one is used. Range Check Your Radio Check the operational range of the radio before the first flight. Before you turn your radio on the first thing you always must do is make sure no one else is on you frequency (channel). Most model flying fields utilize frequency control so familiarize yourself with their system.
Bobcat nears the ground. It will continue to fly just a few inches off the ground for a surprisingly long distance. It is important you don't over-control the model. Make control inputs slowly and smoothly. If you are an inexperienced pilot, you should reserve first flight attempts for calm days when the wind is five to seven mph or less. Inexperienced pilots can find it difficult to keep a non-powered model upwind in heavy wind conditions.
FLIGHT LOG Date Comments Started construction Finished construction First flight 35
If you would like to keep your manual intact, photocopy the dihedral gauge shown below and use the copy to make your gauge. Instructions for constructing the gauge are listed at step 4 on page 21. Note: Be sure to copy the gauge at 100% or a 1:1 setting - no reduction or enlargement. BOBCAT DIHEDRAL GAUGE 1.