OK Models DJ-1

Model Airplane News, Dec 2003 by Bell, Rick

A zippy flying wing for ducted fans

Back in the '80s, OK Models' Pilot kits were the hottest ones on the market. It seemed as if everybody was building one and had another kit waiting to be built. Tragically, the factory where the kits were produced was destroyed in an all-consuming fire. Today, Pilot kits are highly treasured by collectors and builders alike.

I had never built a Pilot kit, so when the opportunity came along to build and review OK Models' newest laser-cut kit, the cool-looking DJ-1 flying wing, I was only too happy to tackle it.

THE KIT

The DJ-1 comes in a rather small box that's packed well. My first thought was: "Where's the rest of the kit?" When OK Models' engineers designed the DJ-1, they designed it as a fast, easy-to-build model with a low parts count. They used a laser to cut the parts with incredible accuracy; if you've never built a laser-cut kit before, you're in for a pleasant surprise.

The rolled, one-sheet plan is very nicely drawn and includes the instructions to build the model; there's no separate instruction manual. To help you build the model, there are quite a few photos on the plan sheet that show several stages of construction. The photos are laid out sequentially and are very detailed.

The kit includes vacuum-formed plastic parts for the cockpit tub and the rear deck, a fairing for the main wheel, a blue-tinted canopy and miscellaneous hardware. Surprisingly, control horns, pushrods, hinges, decals and the main wheel aren't included in the kit.

If you want to make the DJ-1 logo, you can go to okmodel.co.jp/DL-sticker.htm and download the DJ-1 images for patterns. (The website is in Japanese, but if you scroll down the page, you will see "DJ-1" with a link to a 22kb pdf file to the right of it; there's also a link on that page to download Adobe Acrobat Reader, if you need it.)

CONSTRUCTION

Before you start to build the DJ-1, you have a couple of decisions to make: which power system to use and whether you want the nose gear to retract. By far the coolest way to power the DJ-1 is with the ducted-fan unit (DP-2) that MRC offers (item no. 043573). It's a complete package that includes a .18 Toki pull-start engine, a tuned pipe, the fan and duct unit and all the necessary hardware. You could also use a .15 engine mounted on a pylon in a pusher configuration.

Your last decision concerns the nose gear. The kit provides a long wire that acts as a skid, but I think MRC's retracting nose gear (item no. 033198) is the way to go.

Fuselage pod. Before you begin, identify the parts in the laser-cut sheets. I followed the plan and assembled the fuselage, making sure that I built a left and a right side that I later joined with formers and internal braces. Because the fuselage construction is tab-and-slot, hold the assembly together with rubber bands before you apply any glue. This allows you to line everything up on the fuselage top view for perfect alignment.

I glued the nose blocks into place and then added the bottom sheeting before I shaped them. (For all the construction, I used an assortment of ZAP CAs and epoxy.)

If you use the retractable nose gear, outline the wheel opening with the included balsa when you install it. For a smooth transition, I trimmed the canopy and the cockpit tub and placed them on the fuselage as guides. The canopy/tub assembly is held in place with a tab and slot at the front and a single screw toward the rear.

The DJ-1 doesn't come with a fuel tank, and the area designed to hold one is small. OK Models made a tank especially for the DJ-1 (item no. 033017), but I wanted to see whether I'd be able to squeeze in something else. The fuel-tank compartment tapers at the rear and herein lies the problem. I found that a round, 4-ounce, Sullivan tank fits with some massaging; the tank's rear was a little too wide, so I used a heat gun on it until it was pliable; then I pushed the rear sides in until it fit in the compartment.

Wing assembly. The wing is easily built in halves (thanks to its simple layout and interlocking parts) that are attached to each side of the fuselage. To attach the wing securely to the fuselage, three braces pass through the fuselage and into the wing. The airfoil is semisymmetrical, and the ribs have tabs on their trailing edges so that they'll line up when they're pinned down. Before you begin to assemble the wing, splice the sub-leading edges together and make two sets. This is also a good time to splice together the leading edge sheeting; build the left wing panel first.

Pin the bottom spar and the ribs to the plan sheet, which you should protect in some way (I used Great Planes' Plan Protector). Before you pin down ribs C1, D1 and E1, add the servo mount to the ribs, but don't glue them yet! The servo openings in the mount are sized for miniservos, so if you plan to use a servo of standard size, enlarge the openings now because it will be very difficult to do so later. The top spar, the sub-leading edge and the trailing edge are added to the ribs without glue; align all of the parts and use thin CA to tack-glue them together.