Construction/Supermarine Spitfire Mk I
A great-flying, electric battle of Britain superstar
Dateline England, July 10, 1940: The sun rises over the sod airfield, you scramble to your Spitfire, sirens wail and your ground crew chief is waiting. Within seconds, you are strapped in, the wheel chocks are pulled away and you advance the throttle of the mighty Merlin engine. The Battle of Britain has begun! Fast forward 79 years, and you can now realize your dreams of being a Spitfire pilot with this easy-building, electric-powered sport scale Supermarine Spitfire. The eighth model in my RC warbird series, the legendary Spitfire Mk 1 is rarely modeled, compared to the more popular later variants, but it’s a stunning warbird to build and fly. It’s also an excellent companion to two of my other warbirds, the popular Bf 109E and Fw 190A (both available from the AirAgeStore.com website). My friends and I have flown simulated dogfights with them, and it’s a great deal of fun and they look fantastic! If you have ever wanted a Spitfire but were hesitant because the kits or plans were too complicated, or because the model just didn’t look like a Spitfire, then this is the warbird for you. Though not for a beginner scratch-builder, it is easier than you might expect, if you use these simplified build steps.
THE FUSELAGE
Begin by laminating and cutting out the fuselage formers. Most are made of laminated 1⁄16-inch balsa. Add the 1⁄4-inch square stringer to F2. Pin F2, F4, F5, and F7 over the plan. Cut the full-length side 1⁄4-inch square stringers and glue them in place. Add F6 at this time, as it is a floating former that’s not pinned to the board. Install the top centerline 1⁄4-inch square stringer. Ensure that the fuselage is still straight and add the bottom centerline 1⁄4-inch square stringer. At this point, you may add the two short upper 1⁄4-inch square stringers and two lower stringers, alternating side to side to reduce any tendency to twist.
Glue in your firewall next. Do not forget to install it with the required downthrust.
You can add a temporary 1⁄8-inch square diagonal stringer in the nose area to maintain shape. Glue in the small F3 pieces on each side of the fuselage. While the fuselage frame is still on the board, begin sheeting
(or if you prefer, planking), by installing 1⁄16-inch medium sheet balsa on the sides from the full-length thrust line down to the lower stringers. Use the side view to judge how much to sheet. When you have sheeted the sides, sheet the turtle deck portion with medium 1⁄16-inch balsa sheet. Now, you can remove the assembly from the board. Using the former templates provided on the plan, trim the excess former material from F2,
F4, F5, and F7. Continue sheeting the lower portion of the fuselage.
After you have sheeted the fuselage, mark the area behind the canopy and carefully cut it out. Sheet the bottom area and back with 1⁄16-inch sheeting. Move to the nose and cut a 1⁄4-inch sheet to match the contour of the 1⁄16-inch balsa sides from the firewall to F2. This will provide strength and gluing area for the nose block, which you’ll add next. I advise against hollowing out the chin block, as it provides needed weight and strength, not to mention dent resistance on the chin. Carve the chin block to shape, then sand it with the appropriate grit paper. Add the doublers in the stabilizer area and, using scrap 1⁄8-inch balsa as a spacer, add the fill pieces above and below the stab. Using the template on the plan, cut the wing saddle, leaving a bit more wood than you need so you can drawsand for a tight wing and fuselage fit.
The hatch is built on the fuselage for the best fit. Begin by cutting the 1⁄16-inch balsa floor to fit. Place waxed paper under the floor and pin the floor to the fuselage. Measuring 1⁄16 inch from the edge, add the 1⁄8-inch square balsa. This allows room for the hatch sheeting. Cut out and install H1, H2, H3, and H4. Add the gussets and top 1⁄4-inch square stringer, and then carefully sheet the rear portion aft of H2 with 1⁄16-inch balsa. Trim the canopy/cockpit area.
I used pink foam for the front portion of the hatch forward of H2. The Spit has a somewhat flat section toward the spinner and bulges for the rocker covers. Considering these compound curves, foam is a natural material, though you could also use a light balsa block. After sanding the foam and hatch to shape, glass it with 1⁄2-ounce cloth and finishing resin.
TAIL FEATHERS
The stabilizer/elevator and fin/rudder are simple 1⁄8-inch balsa. Be sure to use true flat medium balsa and make them with the grain, as noted, to ensure they stay flat and are strong. I recommend that you cover the tail before you glue it in place, as this allows a much cleaner job of finishing. The elevator halves are joined with wire, or if you prefer, a piece of 1⁄8 x 1⁄4 x 6-inch spruce.
THE WING
Ah, yes, that dreaded, yet oh-so-admired trademark Spitfire elliptical wing! While certainly not as simple to assemble as a constant chord or double tapered wing, I think the method I’ve devised results in a strong, light, fairly easy-to-build wing. There are only six ribs on each panel!
The wing is built on two carbon fiber rods of about 0.2-inch diameter. These rods are supported on two common 7 1⁄2 x 2 x 4-inch bricks. Similar bricks are placed on top of the rods to keep them in place. You can remove the rods after you’ve sheeted the wing.
Begin wing construction by cutting the ribs from balsa of the appropriate thickness. Use solid, medium to hard balsa. Drill holes for the rods to slide through. Slide the ribs onto the rods, and then using 1⁄8-inch square spruce, add the top spars with the ribs pinned to the board. This will provide proper placement to the ribs. Next, with the top spars attached upside down, place the rib assembly on the bricks and add the bottom spars. Use the dihedral gauge to ensure that R1 is at the correct angle for dihedral.
You will see that the wing has some odd curves, but do not be alarmed. Add the rear 1⁄8-inch hard balsa spar to the rear ends of the ribs. This will not be straight, but will taper toward the root and tip. For this reason, use a piece that is about 1⁄2-inch high and sand or carve to shape after installing. Add the leading edge by using two pieces of medium 1⁄8-inch sheeting. Wet the wood and glue one piece to the ribs. After it has dried, add the second piece. Install all gussets. Now, install the shear webbing from 1⁄16-inch vertical grain balsa. I used shear webs on all three sets of spars as shown on the plan, which might be a bit of overkill but it has held up well. At a minimum, shear web the main center spars.
You can now sand the frame to get a beautiful taper to the leading edge and rear hard balsa spar. This ensures strength and a tight fit. At this time, add the small rib spacers in the handhold areas. Using the plan as a template, glue together enough 1⁄16-inch sheet balsa to make lower wing skins. Stack and cut the lower sheeting on each wing panel. With the wing frame inverted and held in place by the bricks, glue on the lower wing sheeting with slow-drying glue. When dry, place the panel right-side up on the bricks and slip a shim of 1⁄16-inch balsa under the rear of the wingtip brick for washout.
Assemble and install the torque rod and tube. Be sure they move freely. Add small pieces aft of the torque tubes. Stack and cut two identical top 1⁄16-inch sheets about 1⁄2-inch oversize in all directions and install one on the wing panel using slow-drying glue.
Once the glue has dried, remove from the bricks and add the wingtip. Repeat the procedure for the opposite wing panel, and then sand both to shape on the leading edge, trailing edge, and tip. Join them with 2 1⁄4-inch dihedral per tip with epoxy, and wrap with glass or nylon tape and epoxy. In order to make the epoxy absorb into the wood, I use a heat gun as well. Be absolutely sure that the two panels are joined straight, as any misalignment will result in a bird that is very hard to turn in one direction.
WHAT MAKES A SPIT A SPIT?
Besides the wing, the wing fillets are what make a Spit a Spit! Before starting on the fillets, however, draw-sand the wing saddle to accept the wing with a perfect fit. You shouldn’t be able to see any light around the joint, and it should fit very tightly in the saddle. When the fit is perfect, use epoxy to glue the wing to the fuselage. Do not be tempted to make the wing removable. It acts as a binding unit, adding greater strength to the thinly sheeted and lightweight fuselage. A Spit just doesn’t look right without those long, curvaceous wing fillets. While they are not simple to replicate, taking that bit of time results in a very good-looking bird.
Cut out and install the rear bottom portion of the fillets of 1⁄16-inch balsa, with the grain, as shown on the plan. If you install one side, make a card template of the location so you can be sure that the left and right match.
Cut the fillet formers out of 1⁄8-inch balsa using the template on the plan. Each will need to be trimmed and cut to size to match the wing angle and the curve of the fuselage. When you have a good fit, make a second for the opposite side. You can use as few or as many as needed; there is no hard and fast rule.
I sheeted the fillets with 1⁄32-inch balsa and used balsa filler for the extreme forward portion, since balsa just doesn’t like compound curves that tight! The key is to be patient and do a proper job. It will show when you are done, trust me.
ASSEMBLY
At this point, I typically do my radio installation. In this way, if I get hangar rash I can fix it before covering. This ship uses a clean installation of a single aileron servo and a single elevator servo. Mount them using your favorite method, be it double-sided tape or screws. Mount
your motor (I used an ElectriFly 42-40-800 with a Master Airscrew Electric Only 12x8 prop), ESC (Castle Creations Phoenix-35) and receiver, and check that the 3-cell LiPo (Tanic 2200mAh) will fit in the nose.
Now you can cover your Spit. I used doculam thin laminating film on the entire model, with the exception of the glassed hatch. On areas of high wear on the real bird, I used pieces of foil tape. Now it’s time to install the stab and finch. Make sure they are in proper alignment, and use slow-curing glue.
After covering your Spitfire, wipe it down with acetone. I sprayed mine with Model Master plastic model paints, available in small spray cans. Spray the light colors first, then the darker ones. Markings are a combination of paint applied with frisket and self-stick trim material. Finally, add the pilot and canopy, and then hook up the elevator. Balance the model on the center of gravity (CG), as per the plans. This is one bird that does not like a rearward CG. The control throws are approximately 5⁄16 inch on ailerons and plus or minus 3⁄16 inch on the elevator.
IN THE AIR
Before attempting flight, perform a radio range check with the motor running to look for any interference. Make sure that all control surfaces move the correct direction and with proper deflections. Double-check the CG, and you are ready to go!
With a fully charged pack, run it up to full power and give it a firm toss, wings level, slightly nose high. As long as your model weighs less than 36 ounces and you’re using a 225W or higher motor, there should be plenty of power. Once at altitude, make your turn away from the flightline and trim it out. Mine required minor trim to fly flat and level. Try not to get too wild with it on the first flight. Get it up there, trim it out, gain some air, and cut power down to get a feel for the stall. It can stall rather abruptly and with little notice, even with the washout.
The Spitfire will slow down rather well, but if taken a bit too far it will snap, so be warned. When landing, keep a bit of power on. The big prop can add a lot of drag if it isn’t spinning. Fly the Spit down nearly onto the ground, about a foot off the deck, then flare. Flaring too soon results in a none-too-pretty landing (like a 1-point or a 6-point).
After landing, go over all the linkages, motor mounts, and servo mounts to make sure nothing came loose in your shakedown flight. Now you can go up and really chase Messerschmitts and Focke-Wulfs out of the sky! The Spit performs very well as a warbird. It will do all aileron/elevator moves with style and grace, and with a rudder added you can do just about anything you’d like. Rolls are quite axial, and loops are large and round. Big, open, smooth moves look best. The real bird was not jerky but had a lot of flow in the air.