Windrider aviation EPP Bee

Windrider aviation EPP Bee

Garwood, Dave

Fast-build slope soarer

Windrider Aviation is a relative newcomer to the U.S. RC plane market, but It sets a new standard for completeness in expanded-polypropylene (EPP) slope sailplanes with its EPP Bee model. Although the Bee is well suited to less experienced slope pilots who may be ready for an acrobatic plane, it’s also quick and agile enough to keep experienced pilots entertained. EPP foam doesn’t break; even if crushed on a hard landing, it will go right back to its original shape.

All necessary parts and materials (and more) are included, and the Bee can be assembled and ready to fly in 2 hours or less, as it doesn’t need glue. The total project cost (without radio) is $50 plus shipping. I found that ordering the kit from Hong Kong over the Internet worked well, and order fulfillment was accurate and timely.

KIT CONTENTS

The exceptionally complete kit contains the expected basics of molded EPP foam wing halves, sanded balsa elevons, precut wingtip vertical fins, complete control linkages and a five-page building instruction booklet with 10 photographs. The translated inductions are at times difficult to understand, but the photos show how the wing goes together. The kit goes beyond the basics by including the unexpected extras of filament tape, color finishing tape and precut component hatch covers. In addition to the airframe parts and finishing materials, the kit includes two types of whistles and three decorative stickers.

To build it, you’ll need scissors and sharp razor blades to cut and trim tape, a medium Phillips screwdriver for servo arms, a small Phillips screwdriver for control-horn screws, a 5/64-inch drill to enlarge the servo-arm hole to accommodate the control-linkage wires, and a small saw to cut off the unneeded servo-control arms.

RADIO SELECTION

A flying wing combines the functions of elevator and ailerons into one pair of control surfaces, so you’ll need a transmitter that mixes these functions. I used a single-stick Hitec Focus III SS transmitter, a pair of Futaba S3004 servos and a JR 600mAh flat battery pack. I used a Hitec HAS-2MB 2-channel receiver, but, of course, the Hitec HAS-3MB 3-channel receiver that comes with the Focus III would work as well. I exchanged the servo leads to shorten the wires and allow the Futaba servos to be plugged into the Hitec receiver.

There is plenty of space in the molded pockets in the wing halves to install this equipment, and the layout is shown clearly on the photos in the instruction booklet.

ASSEMBLY

Windrider Aviation specifies that the EPP Bee can be built in 1 1/2 to 2 hours and that no glue is required. I believe both claims are true, but I did use a little Goop glue on my Bee to strengthen and make aligning the wing-halves joint easier, to secure the servos and to fit the hatch covers. Here are the steps to build an EPP Bee in three evenings:

On the first night, read through the instructions, then glue the wing halves together with Goop. Take care to align them accurately, and temporarily apply masking tape to hold them in position. Let the glue cure overnight.

On the next evening, remove the masking tape, apply filament tape as directed and trial-fit the servos, receiver and battery pack. The battery compartment needed a little trimming to accept the specified 4 AA cells and a little shimming for the receiver to fit snugly, but the Futaba S3004 servos fit perfectly. I ground away some foam at the upper side of one molded servo compartment to allow the servo arms to extend the same distance above the wing’s top surface.

You’ll need fairly long servo arms for this installation. Center the trim levers on the transmitter, trial-fit the servo arms to get one arm nearly perpendicular to the servo case, then cut off the other three arms of each. Check the fit of the control-wire Z-bend in the servo-arm holes and enlarge the holes, if necessary. I drilled them out to 5/64-inch diameter to get my control wires to fit.

Cut a 1/4-inch-deep slit from the receiver compartment to a wingtip, and insert the receiver antenna into this slot with a Popsicle stick or similar tool. Leave the excess antenna wire coiled up inside the receiver compartment (not hanging out at the wingtip, the way I did).

Make sure that the radio mixing works before you glue the radio gear into place. Forward and back stick movement needs to impart down- and up-elevator movement, and side-to-side stick movement must impart opposite aileron movement (one up, one down). I installed the servos with a smear of Goop to hold them securely in place. The battery pack and receiver are held in place with the provided corrugated plastic material and then covered with filament tape. I used Goop again to secure the hatches and let them cure overnight. Be sure to leave a hole or a small hinged door in the receiver compartment hatch to charge the battery and to plug it into the receiver when ready to fly.

On the third night, apply filament tape to the wing according to the instructions. Work carefully to apply the tape smoothly, as wrinkles will add drag and slow the plane in flight. The strapping tape is important to airframe integrity; remember that the foam gives the wing shape, and the filament tape gives it strength and some stiffness. Strapping tape also acts as a hinge for the ailerons. The proper hinge gap is important: too tight, and control-surface movement is restricted; too loose, and the hinge is sloppy. Try for about a 1/16-inch gap at the top hinging surface, and allow the bottom hinging tape to come into contact with the top tape for a strong hinge.

Decorate the top and bottom of the wing with the two rolls of colored tape provided in the kit. Putting a light color on the top side of the wing and a dark color on the underside makes the plane easiest to see. Purple and red came in my kit, and I bought a third roll of yellow tape to have a light color on top of the wing. Might as well use your creativity and decorate your plane distinctively. If you make a mistake, just peel the tape off and apply another piece. The kit came with enough tape to cover three planes!

Install the control linkage by fitting the Z-bend ends of the control wires into the servo arms, then clipping the clevises into the control horns. To position the horns on the elevons, slide them left and right until the row of holes in the control horn are aligned over the hinge line, then install the screws and backing plates. Install the wing tiplets with the self-stick hook-and-loop fastener provided in the kit.

Last, check the center of gravity; this is very important to flight performance. The plane should balance at a point between 7.5 and 8 inches from the nose. Farther forward will make the plane more stable and docile; farther aft will make it less stable and more agile. You may need to add weight to the nose or the rear to get the plane to fly the way you want it to. Mine balanced between the specified points without adding weight-a tribute to careful design and production of this molded airframe.

FLYING THE EPP BEE

As good as the kit is and as smoothly as the building goes, the flight report is even better: this plane rocks! It launches easily, tracks a steady course in flight, performs commendable aerobatics and lands predictably.

Our flight testing involved two days with two pilots on coastal 60- to 80-foot hills, the first day in light, 8 to 10mph wind, and the second day in medium, 15 to 22mph wind. Though the EPP Bee launches without a hitch and is easy to fly smoothly, one thing I had to get used to compared with slope planes that have tails is that its roll control (aileron) is perhaps a little less sensitive than I expected, and its pitch control (elevator) response is more sensitive than I expected.

I think this is because although the “ailerons” have about the same area as expected, the “elevators” are about four times larger than expected. You could adjust this using a computer transmitter, but I was used to it after a couple of flights. The Bee’s roll rate is about 270 degrees per second, and the elevator is powerful enough to fly snappy square loops.

Climbs, dives and level flight are all smooth and confidently flown. The Bee has good inverted flight performance and will make repeat circuits flying bottom-side-up in good lift. Large and small loops are smooth and easy with little tendency to fall out to the side. The plane resists stalling, and I did not see a tip-stall in any of our 10 flights. During intentional stall tests, the Bee holds its nose up and slows way down before it stalls, and then it falls off to one side and enters a spin. Spin recovery is easy: just release the control-stick pressure, and the plane will fall a few feet and then begin to fly again on its own.

My favorite part about flying the Bee is the ease with which it does outside loops, including consecutive ones. I consider it an excellent training plane for aerobatics in general and outside loops in particular.

Given the EPP Bee’s reasonable cost for an extremely complete kit, the fast build time and the excellent flight performance, I nominate it as the best new flying-wing glider of the year; it’s particularly suitable for less experienced slope pilots who may be ready for an aerobatic plane and for those who appreciate a quick-building slope plane.

Copyright Air Age Publishing Oct 2003

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