Build and fly for the fun of it

Written by Fitz Walker Old School Model Works Javelin As seen in the October 2020 issue of Model Aviation. Review

Bonus Video

At A Glance

Specifications Flying weight: 5 pounds, 9 ounces Wingspan: 60 inches Length: 49 inches Wing area: 710 square inches Wing loading: 18 ounces per square foot Radio: Spektrum DX8 G2 Receiver: Spektrum AR637T sixchannel telemetry receiver Servos: Hitec HS-225BB; Hitec HS-322HD Recommended power system: .25 to .51 glow engine or equivalent brushless motor; 3S or 4S LiPo battery Motor used: BadAss 3515-940 Kv brushless Speed controller: 85-amp BadAss Rebel Battery: BadAss 4S 5,000 mAh LiPo Airfoil: NACA M12

Pluses

Well engineered and easy to build.
Great flying characteristics.
Unique looks.

Minuses

Some minor typos in manual and on the plans.
Motor mount box (see text).

Manufacturer/Distributer Old School Model Works (513) 755-7494 www.oldschoolmodels.com

The Javelin screams "classic sport plane," and it delivers!

THERE IS SOMETHING special about highwing sport airplanes. The configuration is not intimidating and almost trainerlike, yet it is capable of a fairly high degree of aerobatics. It is a "comfort food" type of model if you will—a lowstress airplane that you can fly anytime and on a whim. This seems to be the philosophy of the Old School Model Works Javelin, a .40-size glow/electric high-wing sport airplane kit. It’s an all-original design that invokes the merging of fun-fly performance with Pattern aircraft influences wrapped up in a stylish, if somewhat angular package. Nearly every wood piece that is not a balsa stringer is laser cut—even minor parts not normally thought necessary to bother with lasering. I inspected the kit contents and all of the parts were of good, consistent-quality wood. I counted roughly 24 sheets of laser-cut parts in addition to numerous balsa and basswood sticks. All of the precut parts are clearly labeled with intuitively named, engraved lettering. Both the balsa and plywood parts sheets were cleanly laser cut. A generous amount of hardware is included; the only items I needed to purchase were wheels and pushrods. The plans come rolled in two sheets, with one each for the wing and fuselage parts. The manual is 18 pages, with each step featuring an associated black and white photo. Those who like more color in their life can download an electronic copy of the manual, complete with color photos, from the manufacturer’s website.

Build

Construction starts with the wing, which uses the company’s own coined WEBLOCK wing construction technique. I guess that refers to how most of the wing pieces are laser cut, including the sheer webbing, and are designed to interlock like a 3D puzzle. Well, this "puzzle" begins with building the wing inverted, starting from the center section outward. All of the wing ribs have breakaway tabs on the rear to help with alignment of trailing edge (TE) components and to set the washout automatically. Pay special attention to how the center rib parts are assembled because I nearly glued the (H1/H2) cross members into the wrong position. Much thought was put into the wing construction and it shows. All of the wing ribs have large lightening holes cut out of them and even the sheer webs are precut to shape for a drop-in fit. I should note that the company provides a couple of laser-cut alignment triangles to help align the ribs, although I didn’t really need them because everything self-aligned when I slid them into position. After all of the ribs were in place, the precut center wing sheeting was added. The ailerons and center wing TEs are constructed using the aforementioned wing rib tabs as guides. This worked pretty well, although I did break a couple of tabs off prematurely. (Fortunately, they can be easily glued back on.) Ailerons are not solid wood, but rather a lightweight, built-up structure with ribs and sheeting. Capstrips and leading edge (LE) sheeting finished the wing construction. The fuselage begins with constructing a plywood subassembly. This front fuselage section is keyed together in a mostly foolproof way, with a balsa doubler that extends the sides to make up the tail. Both the balsa and plywood parts have generous lightening holes throughout. Everything assembled especially well; however, the front fuselage formers and landing gear mount were a bit fiddly, with quite a few tabs that needed to be inserted all at the same time. Other than for aligning the balsa fuselage side pieces, the plans were used mainly as reference because the fuselage can be built more or less in your hands. The complete fuselage is quite stout, especially considering the amount of wood that was cut out. With the fuselage completed, the final major parts are the tail and landing gear assemblies. Here is where I noticed a small error on the plans regarding the factory-cut corner fillets on the rudder. Because of the different corner angles, each fillet is uniquely numbered, but the plans showed the same number for all of them. This was a minor issue because it was easy to find which fillet went where by trial-fitting the parts. However, the next problem was my own fault. The metal landing gear legs are screwed into a wood crutch assembly that then bolts onto the underside of the fuselage. Apparently, I wasn’t paying close enough attention to the landing gear assembly instructions because I inadvertently built the entire assembly upside down. I glued some specific pieces of wood on the wrong side of the structure. I was ultimately able to correct the mistake, but it took some swearing, surgery with a razor saw, and a personal vow to pay better attention to the manual.

The kit includes intricately cut balsa, light plywood, and basic hardware.

The final ancillary parts, such as the aileron servo mount plates and electric motor mount box, went together quickly. Note that the removable electric motor mount box had some odd offsets just behind the motor plate that left a gap where it connected to the box. I ultimately filed off the small tabs in the wood so the plate would fit flush and provide more surface area to glue to the bulkhead. To stiffen the plywood slightly, I soaked the wood around the screw holes with Starbond thin CA glue. I should also note that there are alternate instructions and provisions for those who wish to use a glow engine. Either way, a large access hatch in the front is securely held on by magnets for easy access to the battery or fuel tank. As with any built-up kit, expect to sand the structure before covering. The ailerons and wing’s LE needed the most attention. Iron-on covering was done using blue and white UltraCote from Hangar 9. A small sheet of decals is included, but if you need more, Callie Graphics has a nice set of premade vinyl decals for this model with lots of color options. In the spirit of Henry Ford, I chose black.

The wing ribs have a lot of material cut out of them. Note the TE breakaway alignment tabs.

Power setup is a BadAss 3515-940 Kv electric motor and associated Rebel Series 85-amp ESC from Innov8tive Designs. Along with the company’s 5,000 mAh four-cell LiPo battery pack, this makes up one of the recommended power setups for the Javelin. This motor configuration is rated for roughly 800 watts, which is more than enough watts per pound for this type of model. I had no issue getting the recommended center of gravity (CG) balance point with plenty of room to move the battery pack around. There should be no problem balancing the model with larger- or smaller-size batteries.

The wing is primarily built inverted on top of the plans. Breakaway tabs aid in the aileron construction.

The fuselage consists of balsa sides glued to a plywood core. The structure is strong and lightweight.

The motor mount box is removable using bulkhead screws.

The completed airframe is ready to cover.

Flying

The Javelin tracks nearly hands off on takeoff. Little rudder correction was needed for the short takeoff run off of grass. The climb rate on the 4S battery and APC 11 × 7 propeller was good, with a nearly unlimited straight vertical. The BadAss motor and propeller combination supplied all of the power one could need on this type of airplane. In the air, I felt instantly comfortable while flying a few circuits, making minor trim corrections. Level flight "on the wing" can be easily done at 1/3 throttle setting or less, and the recommended aileron throws were effective and not twitchy when set up according to the manual. I generally found all of the controls to be well balanced. Although the turning authority is pretty sedate on the ground, the rudder is surprisingly effective in the air—not only for stall turns, but also for knife-edge flying, even with some excess rudder throw to spare. There was a small amount of elevator pull while in knife-edge flight, but the Javelin was stable in that maneuver and likely just needed a small tweak of the CG. Despite the high rudder authority, snap rolls are mild and not prone to wild gyrations. I noted that snaps were faster to the right than the left. Inverted flight needs a slight bit of down-elevator and felt as stable as upright flying. Stalls are barely noticeable, with just a slight bobbing in pitch, even with full up-elevator deflection and the motor power cut off. I was even able to use the rudder to execute turns while deep into the stall. Conversely, at full throttle, the Javelin zips by at a brisk speed.

You will find plenty of room inside the fuselage for your power system and radio gear.

Out of curiosity, I tried an APC 12 × 6 propeller, which provided slightly better climb, but not a drastic change in performance. Regardless of which propeller I used, I consistently achieved more than 7-minute flights with quite a bit of battery energy to spare. A surprising amount of momentum is maintained on the glide down to landing. Although having the flaperons programmed in according to the manual’s recommendations did help bleed off speed some, I still had a tendency to slightly overshoot the approach the first few times, so be prepared to cut the power back on the downwind leg earlier than you might expect. Good control authority is maintained well into the flair and touchdown. The Javelin is easy to build and a delight to fly. Much thought went into the design and construction techniques that were used to build a model with some clever engineering. Although it is not quite a beginner model, anyone who has soloed a trainer can fly it. Expert fliers will appreciate the Javelin’s wide performance range and easy handling characteristics.