Laser Models Laser Arrow

Model Airplane News, Apr 2002 by Kulesa, Stan

A sweet flying delta wing

There's something eye-catching about a "delta-wing" type of aircraft. The mystique of an airplane with no fuselage or empennage piques our curiosity and challenges our instincts concerning aerodynamics. The Laser Models Laser Arrow delta wing is one in a new line of models distributed by Great Planes, and I quickly accepted the offer to review it.

Laser Models employs laser-cutting technology and claims that its Laser-Lock Building System ensures a lightweight airframe that's straight and strong. THE KIT

The kit consists of several sheets of laser-cut balsa and light plywood. To minimize damage, the wood sheets are secured to the bottom of the box with cardboard tabs. The hardware package is complete and includes pinned hinges, screws, devises, control horns, a fuel tank and other assorted parts. There is also a Nyrod (for throttle) and threaded-wire pushrods. The Laser-Lock building technique is very interesting; no plan is provided, nor is one needed. Instead, the building process relies on accurately laser-cut parts and interlocking tab-and-slot construction to ensure proper alignment.

CONSTRUCTION

The translated step-by-step manual is a little awkward to read, but each construction step is complemented by a 3D exploded illustration and a photograph of above-average quality; these help to clarify the written instructions.

Laser Models markets its products worldwide, so the instruction manual is written in four different languages, and I found it very useful to highlight the English instructions. That way, I didn't accidentally miss any steps. Metric measurements are used throughout the kit; in this article, I've converted them so they approximate standard inches.

To build the Laser Arrow, I used a variety of Great Planes adhesives such as Thin Pro CA and Thick Pro CA, and for high-stress joints, Great Planes Epoxy. Construction begins with an IA-inch plywood assembly, through which the landing skid passes; the Laser Arrow has no wheeled landing gear. This assembly, the engine mount, some corner gussets and the servo mounts are the only plywood parts in the model; everything else is constructed of balsa. You can understand how Laser Models has succeeded in keeping down the model's weight.

Begin construction with the skid assembly. Three small balsa formers are glued to two 1/8-inch-balsa wing spars and are then slipped into place between two balsa core ribs. Next, these are slipped into three spars into which slots have been cut for the rest of the ribs and formers. The framed-up assembly resembles a tic-tac-toe grid and makes it very easy to keep the assembly square. The model has 14 fully symmetrical, 1/8-inchbalsa ribs, and the leading edge is notched so it slips into place through the fore end of all the ribs. I added the leading- and trailing-edge sheeting last and then sanded the airframe smooth.

The Laser Arrow's twin fins have no rudders and are built out of two pieces of 1/8-- inch-balsa sheet that are butt-glued together. The elevator and ailerons (or elevons) are made of 2-inch tapered balsa. Because of the stresses placed on the control surfaces, I was pleased to see that the balsa for the elevons is of a superior grade with a tight grain. The model uses four hatches for access to the fuel tank, each servo, the battery pack and the receiver.

I built the engine mount by sandwiching two, laser-cut, 1/8-inch plywood pieces together and then cutting out the opening for my engine. To ensure that the mounting holes for the engine were properly aligned, I used my Great Planes Dead Center Hole Locator. I then installed the engine and the supplied, 8-ounce fuel tank.

* Radio and engine. The Laser Arrow is suitable for either a basic radio system or one that has delta-wing mixing; I used a basic radio without mixing. If your radio has mixing and you use it on this model, the control surfaces are cut in half and use three servos-one for throttle and one on each elevon. If your radio system does not have mixing capability, the control surfaces are cut into thirds and use four servos: one for throttle, one for each aileron and one for elevator. The servos are side-mounted on plywood trays, and I used socket-head screws to mount them; access to the screws can be difficult, and the socket-head screws make access easier. The instruction booklet gives the amount of throw for each control surface; I followed its recommendations exactly and had excellent flight results.

To power my model, I chose an O. S. .46 LA 2-stroke engine swinging an APC 11x6 fiberglass propeller. I also added a Great Planes 2 1/2-inch spinner.

* Finishing. This is the kind of model you can have a lot of fun designing a trim scheme for. Initially, I was tempted to finish it so it looked like a "yield" sign. I also considered covering it with aluminum MonoKote and trimming it with military jet-aircraft insignias. One important issue to be mindful of when designing the finish for a delta model is to be able to differentiate the top of the model from the bottom while it's in flight. I chose to cover the bottom of the Laser Arrow with yellow MonoKote and the top with true red trimmed with yellow and white lightning bolts.