Great Planes RV-4

Great Planes RV-4
Model Airplane News, Jan 2003 by Onorato, Jim

Sport-scale aerobatic Sunday flyer

The RV-4 ranks among the most popular homebuilt aircraft in history. Between 900 and 1,000 of them have been built and flown in countries all over the world. Although it isn't specifically intended to be a vehicle for showy aerobatics, the RV-4 has proven quite capable of such maneuvers. Much like its full-size counterpart, the Great Planes RV-4 model seems to exhibit the same split personality; although it's a natural for smooth Sunday sport flying, this model can also be an aerobatic powerhouse.

THE KIT

The RV-4 kit features balsa and lite-ply construction with basswood wing spars and an ABS plastic cowl, wingtips and wheel pants. Other items include a generous hardware package; hinges; an adjustable engine mount; preformed, aircraft-grade aluminum landing gear; self-adhesive decals and a vacuum-formed windshield. A rolled, two-- sheet, computer-drawn plan and an excellent 52-page instruction manual complete the package. This is a typical Great Planes kit, with the high-quality materials and excellent parts fit that modelers have learned to expect from this company.

CONSTRUCTION

I used Great Planes' thin and medium Pro CAs and accelerator for most of the construction, but I used six-minute and 30-minute Pro Poxy on the firewall, wing-- spar joiners, wing-bolt blocks and landing-- gear blocks.



* Tailpieces.

The fin, rudder, stab and elevator were all built directly over the plan using 1/4-inch stripwood and laminated 1/8-inch die-cut balsa parts. I added an extra piece of balsa at the bottom of the fin to provide a place for the covering to adhere. The model came with CA-type hinges, but I didn't install them until after I had covered the model.

* Wing.

The wing has a constant chord and a fully symmetrical Selig 8036 airfoil. It uses a one-piece, notched shear web onto which I positioned die-cut balsa ribs, followed by two 1/8x1/4-inch basswood spars and an inch die-cut balsa trailing edge.
I assembled the whole thing over the plan and then glued the pieces together with thin CA. One discrepancy I noticed in the plan and instructions concerned the placement of root rib W1. To correspond to the wing's dihedral angle, this rib has to be set at a slant-it instead of vertically, as shown. A dihedral gauge would have been helpful here. I didn't remove the wing from the building board until after I had glued on the 3/32-inch leading-edge sheeting, the trailing-edge sheeting and the capstrips. I then turned the wing over and sheeted the bottom.
The instructions covering the construction of the trailing edge where the wing bolts are to he installed were a bit complicated. Study each step carefully before you begin this part of the construction. I found it easier to shape the balsa blocks before they were glued into place.
The RV-4 has molded ABS plastic wingtips. These were trimmed and glued into place, and I sanded the wing to match their contours.
You can leave the tips off until after the wing has been covered; then paint and attach them. Next, I built the ailerons and functional flaps using the plan as a guide.
I then trial-- fit them to the wing with the provided hinges. I joined the wing halves with an 1/8-inch lite-ply dihedral brace and an 1/8-inch dihedral brace doubler then slid this assembly into the openings in the ribs and twisted it into place against the spars. I used 30-minute Pro Poxy for this joint. I assembled four servo trays for the aileron and flap servos and glued them into the wing at the locations shown on the plan. The addition of the center sheeting completed the wing's construction.

* Fuselage.

The fuselage is primarily constructed of die-cut, lite-ply parts. The die-cutting is excellent, and the parts fit perfectly. Great Planes uses computer-designed, interlocking parts to ensure a strong and straight fuselage. Pushrod routing holes on all of the formers take the guesswork out of the installation. After the side, top and bottom subassemblies were built, I assembled the fuselage upside-down over the plan.
Make sure that you build both a left and a right fuselage side, and that the firewall notches are correctly cut so that the firewall has built-in right thrust. Also, when you assemble components that reference the right or left side of the fuselage, take the time to be sure you are working with the correct side. I sheeted the turtle deck and the top of the fuselage forward of the canopy with 3/32-- inch balsa. Patterns are provided with the kit, but a lot of trimming is required. I sprayed the out-facing sides of the balsa sheets with water and ammonia so that they wouldn't split when bent around the formers.

* Engine and radio installation.

Great Planes recommends an engine in the .40 to .52 2-stroke or .52 to .70 4-stroke range. If you select one from the upper end of this range, keep in mind that the RV-4 is a scale model intended to fly at scale speeds; prudent throttle management should be practiced. I chose an O.S. .46 FX 2-stroke engine for my RV-4 and side-mounted it using the Great Planes adjustable engine mount provided. I used a Bisson Pitts-style muffler that fit entirely inside the cowl. The RV-4's roomy fuselage made it easy to install the radio equipment. I installed the rudder, elevator and throttle servos behind the fuel tank, and I secured the receiver battery behind the servos, close to the trailing edge. I wrapped the receiver in foam and installed it alongside the fuel tank. I used standard Futaba servos throughout and connected them to the control surfaces with the hardware provided. The elevator halves required two pushrods that were connected at the servo.

* Final steps.

The RV-4's ABS plastic cowl is molded as two pieces-a top and a bottom. The molded-in cut lines on my cowl weren't very well defined, and I had to be very careful when I trimmed the halves. I had the same problem with the wheel pants. Related Results I covered the entire plane with Top Flite white MonoKote, used silver, black and royal blue MonoKote trim sheets for the stripes and used the included self-stick decals for the graphics. I painted the cowl and wheel pants with white Top Flite LustreKote. I added a 1/8-scale DGA pilot figure and attached the clear canopy with R-56 canopy glue. I used an 11x7 Top Flite wooden prop and a 2 1/4-inch Great Planes plastic spinner.

CONCLUSION

The Great Planes RV-4 is a high-quality, easy-to-build kit that looks great on the ground and in the air. If you're experienced at flying low-wing sport planes, give this one a try. It's highly aerobatic yet stable at low speed. You'll be proud to take this one to the flying field. DGA Designs (716) 393-1838; dgadesigns.com. Futaba, distributed by Great Planes Model Distributors; futaba-rc.com. Great Planes Model Distributors Co. (800) 682-- 8948; greatplanes.com. O.S.; distributed by Great Planes Model Distributors; osengines.com. Top Flite; distributed by Great Planes Model Distributors; top-flite.com. Copyright Air Age Publishing Jan 2003 Provided by ProQuest Information and Learning Company. All rights Reserved