After finally catching a few thermals with my Climmax, I was encouraged to get more into HLG. I was really inspired by the impressive launch heights I had seen guys getting from the new discus launch gliders. At last, the answer to my wimpy launches! For a number of reasons, I chose the Polecat Sidewinder. First, the Sidewinder has a good reputation, as the design it is derived from, the "Disco," won the 2000 AMA NATS. It's also a rudder-elevator polyhedral plane. There's a variety of designs out there, ranging from poly's to full-house 6 servo ships, but for someone who has no intention of competing, a poly will work just fine. Finally, the Sidewinder is the least expensive of the composite DLG's. I hadn't really intended on getting a state-of-the art, composite winged HLG...the balsa sheeted wing on the Climmax suited me just fine. They are plenty strong, and less expensive. Unfortunately, there are no wood winged DLG kits I'm aware of, so Sidewinder became my first choice.
Okay, lets have a look at the Sidewinder. The basic configuration is a 59" span, polyhedral DLG. The fuselage is a narrow pod-and-boom design, with the pod being made of fiberglass with kevlar reinforcement and the long tail boom being made of carbon fiber. The wing has 4 sections, and is double tapered, with rounded tips. It's vacuum bagged fiberglass over Spyder foam (I think). The wing has spanwise carbonfiber reinforcement at the highpoint, both on the top and bottom. The tips have ovals of kevlar reinforcement for throwing, or for placing a CF throwing peg. Airfoils is modyfied Selig 6063. The tail feathers are balsa, covered with mylar. As with most DLG's about 1/3 of the vertical tail hangs beneath the tail boom to balance the high twisting loads that a conventional tail would otherwise cause on launch. Both control surfaces are activated by pull-pull cables, which are routed through the tail boom and into the servos in the cockpit.
Construction: The Sidewinder comes in as somewhat between a kit and an ARF. The wings are seperated into four sections, which you have to glue together with the proper polyhedral angles. This is pretty easy, though, since the angles are already precut into the sections, so no cutting or sanding is required. You just glue the parts together with 5 minute epoxy, then reinforce the joints with glass tape. The wing is mounted with 2 10-32 nylon bolts. The mounting blocks are already glued into the fuselage, so all you have to do is align the wing, drill the holes through the wing and blocks, and tap the blocks for the screws.
The fuselage is very nice, and the CF tailboom is already glued in place. You have to drill some holes near the end of the tailboom for the control line exits, plus cut a slot at the extreme end for the vertical tail to fit in. Up front, the canopy is precut and fits pefectly...no trimming required. There is also a nice integral tray in the cockpit , so you won't have to install mounting rails for the servos. All you need to do is cut access holes for the battery and receiver, and 2 more holes for each servo. The servos are actually held in place with strapping tape that wraps around the cockpit. This seemed strange at first, but it works very well.
The tailfeathers are precut to shape, but you do have to cut the rudder and elevator free. Marks are provided on the wood for this. The kit comes with 2 precut ply control horns, which you also need to install. Finally, the tails are coverd with a thin, transparent mylar covering, which is included. The vertical tail is glued into the slot at the end of the tail boom, and the horizontal gets mounted ahead of this, on a small block which raises it about 1/8" above the tail boom. You have to route the control cables from the tailfeathers up to the servos, of course. This is tedius, but not too difficult.
Well, that's it for contruction. It's pretty easy and quick to build. The instruction manual is very comprehensive, although it could use some clarification in a few places. Still, in the low production volume world of glider kits, its one of the best made manuals that I've seen.
Modifications: Before joining the wing halves, I dug out some foam underneath where the screws go through, and I filled them with a mix of epoxy and micro balloons. The idea here is to prevent the wing from crushing when the screws are torqued down.
Another mod was to route each pull-pull line through a thin push rod tube that extended from the rear of the cockpit to just behind the front wing mount. The reason for this is that the control lines were rubbing against the bottom of the wing mount. The push rod housings simply protect them from that.
I also added a 1/4" CF tube for a throwing peg out on the left wing tip.
Finally, I made a cosmetic change on the fuselage. There is no fairing between the wing leading edge and the bulkhead it butts up against. This means there's an abrubt ledge in front of the wing. This probably has no effect whatsoever on performance, but I wondered about it. I asked Denny Maize, owner of Polecat, about it, and he sent me the remnants of a discarded Sidewinder canopy, which has the perfect cross-section for a fairing. After a bit of cutting and sanding on the part, I had a nice little fairing between the fuse and wing.
Radio gear: The Sidewinder is designed for a 4 cell 100mAh battery pack, a Hitec 555 rx with the case removed, and two micro servos, such as the Cirrus CS-20's. With this combo, the plane will balance without any added weight needed. I also added a Cirrus MPG-1 gyro. The gryo sits on its side, just behind the servo. With the gyro in place, I had to add a penny-sized piece of lead to the tail to restore the balance. However, I didn't fully remove the gyro's case (I left the bottom piece intact), so I could probably shave off a bit of that tail weight if I had got rid of the whole thing.
Final flying weight without the gyro was about 9.6oz. That may be a tiny bit heavy, probably because of the extra epoxy I added in the wing. With the gyro, and the lead needed to balance it out, the weight climbs to 10.2 oz, though the added weight doesn't seem noticable at all (and its probably worth it for the extra launch height).