RC Sopwith Camel

Here's a Radio Control Sopwith Camel 1/4-scale you can build and fly, I have all the steps posted online as "Build-Alongs" and you can check them out at www.modelairplanenews.com/camel1

By Gerry Yarrish

Viewed by many as the British aeroplane that best definedair combat during WW 1, the Sopwith Camel is one of the best known fighters to come out of the Great War. First introduced at the end of 1916 it was a replacement for the Sopwith Pup and about 5,500 Camels were produced.

I wanted a semi-scale model with the strength and building ease of a sport flyer so I started with Wylam drawings and used CAD to simplify most of the structures and replaced the thin under-cambered airfoil with a more
pilot-friendly flat bottom wing. If you’ve built a kit or two, you’ll have
little trouble with the Camel.

Construction

Everything can be easily made with basic shop tools, but to save time, there is also a laser-cut wood kit available from Arizona Model Aircrafters. The wheels and machine guns are from Williams Brothers, and the custom pilot bust is the work of Lyle Vasser from Best Pilots. The 20 oz. RotorFlow fuel tank is from JL Products fitted with Tygon fuel tubing from Nick Ziroli Plans. The 10.5 inch radial engine cowl is available from Fiberglass Specialties but it does have to be cut down a bit in length. The lower wing panels plug into place over an aluminum wing tube from TNT Landing Gear. I designed the Camel around the Zenoah G-38 gas engine, but the engine you choose will determine the placement of the firewall.

The bottom aileron servos are installed in the wing panels and 2-56 slave rods connect the bottom ailerons to the top ones. The entire cockpit and machine gun hump section comes off in one piece to provide access to the radio and fuel tank. It’s held in place with rare-earth magnets. The engine cowl is also secured with several large magnets and two sheet metal screws prevent the cowl from shifting while flying.

Tail Surfaces

The tail feathers are built directly over the plans. The tips are cut from sheet balsa and are shimmed up to center them with the leading and trailing edges. The center section is made with an upper layer of 1/4-inch balsa glued onto a 1/8-inch lite-ply base. This allows the four 4-40 bolts holding the tail to the fuselage, to sit flush with the top surface. Standard Du-Bro pinned hinges are used throughout. The vertical fin is held in place by two 2-56 screws and blind nuts in the fin’s bottom rib. The rudder’s bottom hinge uses a removable pin so the entire tail assembly can be removed in one assembly.

Fuselage

Made with fours lite ply sides, the fuselage has balsa longerons in the corners. The wing saddle doublers, vertical members, firewall supports and the forward formers are all glued in place before joining the sides together. The top and bottom pieces fit between the sides and are flush with the upper and lower edges. Lightly tack glue the parts together using rubberbands to hold the assembly together. Install the aft formers, check the alignment then permanently glue all the joints. I use Zap CA glue and Z-Poxy throughout. Now glue the top aft formers and the stringers in place between the cockpit and the horizontal stabilizer.

The muffler opening is not shown on the plans as you’ll have to determine its size and location from your own engine. The top forward section of the fuselage, (below the hatch), has four holes for the cabane strut wires. You will need to drill down through the upper longerons to fit the cabane wires against the inner surface of the sides. Build the removable hatch section on top of the fuselage. Tack glue the lite ply base in position then glue the top formers to it. Sheet the structure with balsa and thin plywood, then remove it and install the retainer magnets. Wood tabs and screws can also be used to secure the hatch. Now add the fuselage side formers and stringers then sheet with 1/8-inch balsa. The sheeting should end just above the bottom wings, so leave it a bit over-size and trim to shape using a wing rib as a guide.

Bottom Wing Panels

Build each wing panel directly over the plans. Pin the bottom spars and the trailing edge (TE) sheeting in place then glue the ribs into place. Glue the top spar into place then fit and glue the leading edge (LE) dowel in place. Glue the half ribs between the main ribs then add the aileron sub spar strip and LE pieces lightly tack gluing them together. Add the aileron ribs then fit the wing tip parts into place. Glue the top TE strip onto the TE sheeting, trim the TE assembly to fit the wing tip then glue everything together. Cut the ailerons free just before covering the wings.

Top wing

Built the two top wing halves over the plans then join them together. Laminate the center cutout bow from balsa strips and glue in place. Use a razor saw to cut a 1/8-inch-wide section out of the ribs just in front of and behind the main spars and epoxy the plywood center braces into place with 30-minute Z-Poxy. Clamp the panels and braces together until the epoxy cures. Now add the vertical-grain balsa sheer webbing to the front and rear of the main spars, then frame out the center window with lite-ply.

Cabane Struts

A wing alignment jig is shown on the plans. Glue it together and tack glue it to the fuselage where the hatch cover fits. Once the plywood attachment plates and blind nuts have been installed in the top wing, center the wing and tack glue it to the jig.

Bend the cabane wires to shape and slip the bottoms into the four fuselage holes. Attach the solder lugs to the wing with 6-32 cap-head screws and bend the barrel sections down. Cut the wires to length and slip them into the lug fittings. Fit all four cabane wires into place then use scrap lite-ply and Z-Poxy to capture the bottom ends against the inside of the fuselage sides. Measure the distance from each wing tip to the tail post, adjust until the distances are equal then solder the cabane wires into the fittings. Let everything cool off then add the 1/16-inch X-brace wires and solder. Now remove the wing, discard the jig and clean all the flux from the solder joints to prevent corrosion.

The interplane struts are made from 3/4 x1/4-inch bass wood strips with slots cut into the ends that slip over brass attachment L-brackets. Drill small holes in the long end of the brackets so they can be secured in place with 15-minute Z-Poxy. For the wings’ flying and landing wires, I used easy to install brass brackets, Sullivan steel clevises, Du-Bro threaded rigging couplers and braided 0.030-inch steel fishing leader. For details go
to: modelairplanenews.com/rigging.

Landing Gear

The landing gear struts are formed using music wire soldered together and covered with bass wood strips. The 3-section axle provides the travel for the suspension’s bungee shock cords. The tail skid also uses bungee shock cords. A complete “How To” article for the landing gear was published in the September 2015 issue of MAN.

Covering and Finish

Covered with Scale Stits fabric, the Camel is finished with
Poly Tone paint from F&M Enterprises. The covering and painting process is
shown in my online MAN Build-Along series. I used vinyl markings from Red5
Designs and the smaller “Petrol Tank” and “Lift Here” decals were made by
Cal-Grafx. The top and side plywood panels were glued in place with Dapp
heavy-duty contact cement while the front metal panels, (made from 0.015 in.
FTE G-10 fiberglass sheets), were glued and screwed into place. I used rubber
automotive vacuum hose for the cockpit combing.

In the Air

The Zenoah G-38 powers the Camel nicely. The original Xoar
18x8 WW1 Scimitar propeller from Falcon Propellers provided good climb
performance but did switch to a 20x8 prop to better load the engine. Smooth
application of throttle is a must but the smallish rudder does do a good job keeping
the Camel tracking straight.

My radio gear is a JR XG14 transmitter, JR RG731BX 7-channel receiver and six JR 821HV servos. The four ailerons provide positive roll rate and turns are improved with some rudder input. Pitch control is not overly sensitive, but proper balance is important. The CG location is shown on the plans.

Landings are fairly easy for a WW1 biplane with a fixed tail skid. Keep the throttle above 1/4 power and fly a shallow approach angle. Line up with the runway and when you’re about a wingspan above the ground, start applying up elevator to level off and begin your flair. Try to touch down in between a wheel landing and a full 3-pointer. Like most WW1 airplanes, if you land tail-high, the Camel can nose over. A low, reliable idle is a must. Once the wheels are on the ground, pull throttle to idle and use rudder to keep it straight. A little toe-in on the wheels helps prevent ground loops.

Bottom line

I’m very pleased how the Sopwith Camel turned out and I am sure you’ll find it easy to build and fly. To see the entire building project check out my Build-Along series at: modelairplanenews.com/camel1. Remember to keep the tail light.

Specifications

Model: Sopwith Camel

Scale: 25% (1/4-Scale)

Wingspan: 84 inches (top & bottom)

Wing Area: Top: 1,073.39 sq. in., Bottom Wing (total):
1,015.07 sq. in.

Total Wing Area: 2,088.46 sq. in.

Weight: 20 - 25 lbs.

Wing loading: 22.06 oz./sq. ft. @ 20lbs.

Length: 56 inches

Engine req’d: 30cc to 40cc gasoline.

Radio req’d: 4-channel (rudder throttle aileron elevator)

Gear Used
Radio: JR XG14 transmitter with JR 821HV servos (jeamericas.com)
Engine & Muffler: Zenoah G-38 (Horizonhobby.com)
Propeller: Xoar 18x8 & 20x8 (Falconprops.com)
Fuel Tank: RotoFlow (JLProducts.net)
RX Battery: 6.6VA123 NoBS (hangtimes.com)
Cowling: 10.5 In. Fiberglass Specialties (fiberglassspecialtiesinc.com)
Machine guns: Williams Bros. 1/4-scale Vickers (williamsbrothersmodelproducts.com/rc.html)
Wheels: Williams Bros. Vintage 6 5/8 in.
Pilot Figure: Best Pilots 1/4-scale (bestpilots.typepad.com).
Wing Tube: TNT 5/8 in.dia. (tntlandinggear.com)
G-10 fiberglass sheets: FTE (franktiano.com)
Finish: Scale Stits covering & aint (stits.com)
Markings: Red5 Designs (red5designs.com)
Decals: Cal-Grafx (cal-grafx.com)
Laser cut parts: Arizona Model Aircrafters (arizonamodels.com)
Bavarian Demon Cortex 3-Axis Stabilization System: DemonAero.com