Tiggermoth (oz14705)

About this Plan

Tiggermoth. Radio control sport electric model, for speed 400 motor and 3 channels.

Direct submission to Outerzone.

Update 27/7/2023: Added article, thanks to RFJ.

Quote: "Full size free plan feature. A dainty 38 inch span electric Tiger Moth lookalike for geared 400 motors and three-channel control. Tiggermoth designed by Bill Lister.

Tiggermoth is the result of a resurgence of my aeromodelling interest following my retirement from thirty years of intensive activity in the aircraft industry. Having kept somewhat lightly in touch with current aeromodelling development via the occasional magazine, I had witnessed the emergence of electrical flight and the establishment of cheap reliable radio-control. Triggered by my daughter's marriage to a United States Airforce staff sergeant, pet-named Tigger, I looked into the possible redesign of my free-flight biplane Gadfly (oz10525) from the late fifties, and Project Tiggermoth was spawned.

This model has only been flown under electric power, but I have been asked to suggest an IC alternative, which I believe would be 1 to 1.5 cc or 0.06 to 0.09 cu in mounted sidewinder, as in the earlier design. All dimensions are in inches unless otherwise stated.

Construction - Fuselage: I always start with the fuselage, as the accuracy of this will determine the flight characteristics of the model and it is generally the most complex part of the structure.

Cut out all the pieces from F1 to F16, the motor mounting plate, pylon, marked-out fuselage sides and doublers. Incorporate all chamfers and dry assemble the 1/8 ply motor mounting plate, pylon and 1/16 balsa/ply sandwich formers F2 to F4 to a sliding but not a sloppy fit, checking for squareness.

Bend up the undercarriage from 12 swg piano wire and only when true attach to the ply face of F3 using fuse wire binding and solder. Cement together the pre-drilled motor mount, pylon and formers F2 to F4. When dry, mount the motor and gearbox assembly (with plug) to the motor mounting plate. Whilst this is drying, the longerons, spacers (vertical matching pairs), doublers F14 and F9 should have been cemented to the fuselage sides incorporating the pushrod cut-outs.

Invert the fuselage sides and pin over the planview of the fuselage aft of F5. Check and double check for squareness and fit the horizontal matching pairs of spacers and upper and lower F11s. Allow to dry and then remove from plan.

Carefully fit the motor plate, pylon and undercarriage unit assembly to the aft fuselage. Add Fl, F5 to F8 and the fuselage spine F12 and then add the 1/8 balsa gussets either side of the wing cut-out. Add 1/16 sheeting to the lower rear fuselage, 1/8 sheet doublers between F2, F3 and F4 and lower 1/8 sheeting from wing cut-out to F2. Then add the internal fairing on the front face of F2 and add the lower cowl blocks with plate.

The upper fuselage 1/8 x 1/16 stringers may now be fitted from F1 to F8, the 1/16 ply tailplane mounting platform F13 and 3/16 x 1/16 balsa fill-in pieces aft of this, fitted and sanded to shape. Fill in between stringers to aft of F6 with 1/16 sheet. Fit block between F1 and F2 around the motor, relieved to maximise the airflow about it. Sandwich N1 to N4, add I mm ply cheek cowls and their contour pieces F15. Allow to dry and sand the whole assembly. Fit the 18 round dowels in the plywood wing pylon. Now add 3/16 sheet either side of the pylon, chamfered to fit the upper fuselage decking and round off fore and aft. Check for squareness and add the wing mounting platform of 1/16 sheet balsa. Skin with a layer of 1 mm ply.

Bend up the 18 swg piano wire tailskid, stitch it to a 1/16 ply plate and attach it to the fuselage as shown. Fit the 1/8 round dowel lower wing retainers. Cut out the cockpit area, which affects cooling of the motor and BEC. If F12 is retained, it will serve as an attachment point for a profile photograph of a pilot of your choice. Finally, add the two inch diameter main wheels.

Wings: First cut out a 1/16 ply rib and use it as a template to cut out all 44 ribs or cut out another ply rib and sandwich strips between the two and sand to shape. Make up the main 3/16 x 1/8 spruce spars and dihedral braces incorporating sweep for both upper and lower wings, bind with bandage and cement or fibreglass the joints. I prefer the former as it is quicker and quite adequate.

Place one made up spar over the other to check that they are identical in sweep and dihedral. Notch the preshaped 3/4 x 1/8 trailing-edge (TE) stock to take the ribs, and pack the front edge to allow for camber for the port top wing bay. Lay down the 3/8 x 1/8 strip leading-edge (LE), pack up the 1/8 square rear spruce spar and add ribs. Allow to dry, then add the main spar assembly and check that the spar is parallel to the building board When dry, remove and repeat for the starboard top wing, being careful to support the port half parallel to the board, when the main spar is attached to the starboard ribs parallel to the board. When dry remove from the board.

Build up the centre-section as for the wings. When dry, slide the wings into position and add top sheeting. Remove from the board and add the lower sheeting. Chamfer the LEs and add the top LE sheeting to port and starboard wings. Add the wing tip blocks and sand to shape. Repeat this for the lower wings.

Tailplane and elevators: Cut out all parts, 16 1/32 and four 1/16 ribs to root section, 1/8 sheet LE T2, joining piece T1, tips T3, doublers T5, elevators T7, doublers T6 and T8 and key plate T9. The 1/16 sheet fin base tailplane centre-section piece T4 requires the position of the root ribs to be marked before fitting to ensure fin alignment (note grain direction). Lay and pin down the tailplane 1/8 x 1/4 aft spar, 1/8 sheet LE T2, joining piece T1 and tips T3. Cut ribs to fit chord-wise, retain rear sections to make up elevators later and then add the 1/8 square top spar..."

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