DeHavilland DH88 Comet INSTRUCTION MANUAL A semi scale ARF R/C model of the famous winner of the 1934 MacRobertson, England to Australia Air Race. Technical Specification Wingspan: 88 inches (2235 mm) Length: 59 inches (1500 mm) 2 x.32~.40 2 stroke Engine/ 2 x.52 4 stroke Motor: 2 x brushless electric motors. Radio: 5 or 6 channel History of the DeHavilland DH88 Comet The original DeHavilland DH 88 Comet was specially designed to compete in the 1934 England to Australia MacRobertson Air Race. Three were designed, built and tested in eight months with the first flying on the 8th September 1934. The all wood aircraft was powered by two special DH Gypsy Six R engines producing 230 h.p each. The Comet was the first British aircraft with retractable landing gear, flaps and controllable propellers. Sponsored by Australian MacPherson Robertson, the MacRobertson Air Race was the longest ever Air Race from Mildenhall in England to Melbourne, Australia with the winner receiving 10,000 English pounds. Piloted by Charles Scott and Tom Black, the winning aircraft GACSS (named Grosvenor House after its sponsor, a luxury hotel in London) won the race in 70 hours and 54 minutes. Wingspan - 44ft (13.41m) Wing Area - 212sq.ft. (16.69m 2 ) Length - 29ft (8.84m) Height - 10ft (3.05m) Empty Weight - 2,840lb (1,288kg) Max Takeoff Weight - 5,320lb (2,413kg) Fuel Capacity - 258 gal Engines - 2 x 230 h.p. DH Gypsy R Cruising Speed - 220mph (354km/h) Maximum Speed - 237mph (381km/h) Service Ceiling 19,000ft (5,790m) Range 2,925 miles (4,707km) Page 1
Additional Items Required to Complete the DH88 Comet: 2 x Metal geared micro servos for aileron control 3 x Standard size high torque servos for rudder, elevator and flap control 1 x Additional micro servo required if optional retractable landing gear is fitted 2 x Additional standard size servos required for glow engine power (throttles) 2 x Suitable ESCs for electric power version 5 and 30 Minute epoxy glue Medium and thin CA adhesive Masking tape 2 x.32~.40 2 stroke engines & 10 x 6 to 11 x 7 props or (for i.c. version) 2 x.52 4 stroke engines & 10.5 x 8 to 12.5 x 6 props 2 x 36-30-2/1500 RP/V motors & 8 x 5 props or (for electric version) 2 x 36-30-3/1000 RP/V motors & 10 x 5 ~6 props Safety Warning: This R/C aircraft is not a toy. Serious injury or damage to property can result through misuse and abuse. It is recommended that this aircraft is flown at a dedicated R/C flying site and that a qualified instructor thoroughly checks over the model before its first flight. Your local model shop should be able to assist you regarding flying clubs in your area. Page 2
STEP 1: Trial fit the tailplane to the fuselage and mark where the area of covering will need to be removed to expose the wood and enable the glue to adhere properly. Carefully cut through the film covering inside the marks - ensuring that you do not cut into the wood sheeting. STEP 2: Make a groove in the tailplane for the pre-assembled elevator joiner/control horn to rest. STEP 3: Using a sharp knife or a round file, make a small notch in the fuselage to clear the elevator joiner and the rudder/tailwheel assembly. STEP 4: Connect the elevator pushrod to the elevator joiner/control horn and fit into position in the fuselage. STEP 5: Connect the rudder/tailwheel pull/pull cables to the assembly then slide the tailplane in position. Before gluing the tailplane in position, make sure that is correctly aligned in relation to the wing. STEP 6: Now run a small bead of medium CA around the outside tailplane/fuselage joint. This will prevent glue running onto the tailplane covering when applying medium CA adhesive to the inner joint. Page 3
STEP 7: Using 5 minute epoxy, secure the vertical fin in position making sure that it is square in relation to the tailplane. After the epoxy has set, run a bead of medium CA around the outer joint. STEP 8: Using the supplied hinges, fit the elevators and rudder in place by applying a few drops of thin CA adhesive to both side of the hinge. STEP 9: Feed aileron extension leads though the centre wing panel. A hole approximately 16cm from the leading edge will have to made in the center section for the leads to exit. STEP 10: Then fit the aileron servos to the removable hatches with some double side foam tape. For extra security we would suggest fitting additional hardwood mounting blocks. STEP 11: Measure and mark the half way point of the alloy wing joiner tube. Glue the alloy tube into one of the wing panels. Only insert tube up the half way point. Let epoxy set thoroughly before moving to the next step. Page 4
STEP 12: Before glueing the outer wing panel to the centre section, apply masking tape around the edges of the panels to be joined to help prevent glue running on to the covering. Join the panels with 30 minute epoxy. Remove the masking tape from the panels before the epoxy has set. Use rubbing alcohol or methylated spirits to remove any epoxy residue. STEP 13: Secure the ailerons in place with a few drops of thin CA adhesive applied to both sides of the hinges. Fit the control horns to the ailerons and assemble the pushrods from the supplied parts. STEP 14: Install the elevator and rudder servos in the plywood servo tray in the fuselage. Elevator Servo Rudder Servo Adjust the length of the elevator pushrod and the rudder pull/pull cables and fit to the appropriate servo. STEP 15: The DH88 Comet is designed to use either glow or electric power. The supplied engine mounts are used for both glow and electric power. STEP 16: Fitting Glow Engines. For glow engine power the pre-assembled throttle servo mounts need to be installed alongside the fuel tanks in each of the engine nacelles. Page 5
STEP 17: Installing Electric Flight Batteries The installation of electric flight batteries will vary depending on the battery type and size used. The suggested mounting position (for Li-Poly batteries) is under each motor using Velcro straps. We recommend that hardwood rails be installed in this area for added strength and security. STEP 18: Fixed Landing Gear Position the pre-assembled fixed landing gear assembly in the slotted hard wood mounting rails in the engine nacelles. Secure with the supplied landing gear straps and screws. STEP 19: Optional Retracting Landing Gear The retractable gear units use the same mounting rails as the fixed landing gear. Route the airlines so they exit through the same hole as the servo leads. The air tank, retract servo and valve can all be neatly mounted on the wing centre section. Secure with the supplied landing gear straps and screws. STEP 20: The receiver and receiver battery are mounted on the pre-installed plywood tray at the front of the fuselage. Secure the hatch with four of the supplied small self tapping screws. Page 6
STEP 21: Fit the tail wheel fairing using some medium CA adhesive. STEP 22: Fit the engine nacelle fairings to the wing using medium CA adhesive. STEP 23: Fit the clear nose cone and canopy in position with the small screws provided. STEP 24 - Balancing the Model: As with all aircraft it is imperative that the model balances at the correct Centre of Gravity. The C.G. for the Comet is 115mm from the leading edge measured at the fuselage side. Note: if the optional retractable landing gear is fitted, balance the model with the landing gear retracted. STEP 25 - Setting the Control Throws: Aileron - 10 mm up/down Elevator - 25 mm up/down Rudder Flap - 30 mm left/right - up to 40 degrees. Flying Tips: Retractable Landing Gear: Because the landing gear retracts rearwards there will be a change in the aircraft s trim. While the change in trim is small, it is noticeable and the pilot should be aware of this characteristic. Use of Flaps: With the flaps lowered the Comet will balloon upwards slightly and will require some down elevator trim. It is recommended that when flaps are deployed for the first time, do this at a safe altitude and re-trim accordingly. Torque Effect: Being a twin engined aircraft, and with no direct prop wash acting on the rudder, the torque of the engines/motors has a greater effect during the initial part of the take off. The aircraft will veer left and the pilot needs to be ready to correct this with right rudder input. The amount of rudder needed for correction will decrease as speed increases. Landing: Do not attempt to slow the model drastically on landing. It is recommended that wheel landings be performed rather than three point landings. Page 7
Guarantee Advanced Scale Models guarantees this kit to be free from defects in both material and workmanship at the date of purchase. This does not cover any component/parts damaged by use, misuse or modification. In no case shall Advanced Scale Models liability exceed the original cost of the kit. In that Advanced Scale Models has no control over the final assembly or the material used for final assembly, no liability shall be assumed for any damage resulting from the use by the user of the final user assembled product. By the act of using the final user assembled product, the user accepts all resulting liability. Distributed in the USA by: Distributed in Europe by: Distributed in Australia by: Global Hobby 18480 Bandilier Circle, Fountain Valley, CA 92708. USA. Ripmax Ltd., 241 Green Street, Enfield, EN3 7SJ. UK. Model Engines (Aust.) Pty. Ltd. Unit 1, 158-168 Browns Road, Noble Park, VIC., 3174 Page 8