| Racing and Slope Planes |
RC Direct Opus V |
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This is my first molded plane, and so far it's the best flying sailplane that I've owned. The slick Opus looks a bit like an undersized F3F racer. It's smooth, high speed peformance has made it a popular slope sport plane in southern California. With so many 60" and 3 meter race planes out there, the 2 meter span Opus, along with a couple other planes, fills a void in the mid-size slope glider class. The Opus is big enough to feel like a larger plane, but small enough to be as practical as a 60" plane.
Wing: The wing is a single piece unit, with a flat center section and slight dihedral on the outer wing panels. The planform is a straight center section with elliptical wing tips2. Airfoil is the RG-14. The flaps and ailerons have live skin hinges, and are hinged on the top3. The hinge line is scored on the wing surface, so the hinges aren't overly stiff. There are no wipers, unfortuantely. Molded servo covers are included, though. The skin is a fiberglass/Rohacell/fiberglass sandwich, with a carbon fiber capped spar for strength (which it has plenty of). There is a ballast tube installed on the CG, which extends out to the flap servo bays. It holds 9 brass ballast slugs, which all together weigh about 10 ounces. The wing is mounted with a single metal bolt at the rear, and at the front with a curved tab that slides in underneath the fuselage.
V-tail: The v-tail is a single piece unit. It's attached to the fuselage with 2 nylon bolts. Construction is similar to the wing, though with no spar. The elevators are also live hinged (again with no wipers), and the ball link topped control horns are installed.
Fuselage: The fuselage is made of fairly thick fiberglass. It might have kevlar reinforcement, but I'm not sure. One unusual feature is the lack of either a slip on nosecone or a canopy. The only access to the forward fuselage is through the wing saddle opening. This design may be due to the Opus wing being shared by another plane, the Colt 2, an electric sailplane with a fuselage slightly wider, but with a similar shape to the Opus'.
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Fit and Finish: Overal, the fit and finish on the Opus is excellant. The quality of the gel-coated finish, especially on the wing and v-tail, is essentially flawless (at least to my eye). The surface is mirror smooth, and the 3 color paint job is crisp and bright (you can get the Opus in a white or yellow base color, with a variety of trim colors on the top and bottom of of the wing). I wasn't sure about the fit of the wing to the fuselage at first, though. Initially, it seemed very difficult to get the wing attached properly without using some force to wrangle it into position. I couldn't really see any reason why this was happening, but as the wing was successively removed and reattached during the construction process, it got easier and easier to attach. Perhaps there was some extra material left in the wing bolt hole or in the internal nut in the fuselage that eventually wore away. Whatever the case, the wing now fits perfectly.
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Construction: There really isn't much construction, since all the main components come built and ready to bolt on to the fuselage. In fact, the plane doesn't come with any instruction sheet at all. Actually, mine did include a printed copy of Doug Reel's highly recommended Opus V setup information web page, which provides radio installation, construction, and setup tips. Unfortunately, not all Opus V's seem to come packaged with this. With this information in hand, I proceeded to install the wing servos, install v-tail push rods, and build and install the fuselage servo tray (remember, there's no nose access).
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| Here you can just see the two bolts in the nose that hold in the radio tray. The bolt under the wing is for carrying extra ballast in the fuselage. |
I also did the "Doug Reel Opus flap mod," which is detailed on his web page. Because the Opus has top hinged flaps, they don't come down more then 45 degrees. I wanted to be able to slow this puppy down for landings on our narrow ridged slope site, so this modification was a must for me. Basically, it involves installing new flap control horns and cutting away a bit of the flap leading edge and the wing sub-trailing edge in front of the flap. This allows the flap to bend down without being stopped by the upper or lower wing surface. The drawback is that it creates a large gap between the wing and the bottom surface of the flap, but this is easily sealed with gap tape. My flaps now come down nearly 90 degrees, so to me, it was well worth it. Having bottom hinged flaps and molded-in wipers would be a much better solution though.
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| Flaps up: Note the slot cut for extra flap travel. |
Flaps down:Almost 90 degrees of travel. |
Radio Gear: For the v-tail surfaces and the ailerons I used JR 341 micro servos. Hitec HS85 metal gear servos were used for the flaps. For the receiver I'm using a Hitec Supreme 8. Everything is powered by a big 1400 mAh NiCad in the nose. That's a pretty big battery, but the plane needs the nose weight anyway. Actually, a standard-sized square pack 1100 mAh will work fine too. It's lighter, but it fits a bit further up in the nose and will actually reduce the overal weight of the plane by 0.5 oz.
Final flying weight for my Opus is 48oz. With the plane's 483 square inch wing, this puts the dry wing loading at about 14.3oz/sq ft...so the Opus is not a light airplane. That's not what I'd call excessive, but it is higher then the more typical 11-12 oz/sq ft loadings seen in most of the other slope planes of this size.
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| Ready to fly! | |||
Flying: The first flight offered no suprises. The Opus is smooth and responsive, with no real bad habits. Of course, it's also very fast, even unballasted, and it retains energy very well.
I had heard that the thin RG-14 might not be able to yank it through pylon turns as well as an F3F racer, so I was not sure what to expect. With a bit of "snap-flap," though, the Opus will carve through the turns very nicley...better then my Renegade racer, in fact. It might not claw through corners quite like an RG-15 winged 100" racer, but it's turning peformance should offer plenty of excitement for the sport flier.
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Despite it's weight, the Opus offers pretty good light wind performance. As with most high performance slope planes, in light wind you need to keep the nose down and keep the speed up, especially in the turns. Of course, if the wind is so light that the Zagis and floaters are struggling, then you might want to wait for the conditions to pick up a bit before launching the Opus. If you do toss it out in light wind and you happen to find a thermal, be sure to droop the trailing edge a bit, because the Opus responds really well to camber. It will climb out nicely in light thermals, which can really add to the light lift performance.
Of course, going fast is what the Opus is really about, and it does this very well. Even when flying level, the Opus is always covering ground at a good clip. Add some ballast and drop the nose for a speed run and it really goes! The long tail boom and generous tail feathers make it rock steady, even in a screaming dive, and the great energy retention means you can zoom almost right back up to where you started and do it again.
The above qualities also make the Opus a great plane for dynamic soaring. The stability keeps everything smooth and somewhat lessens the white-knuckle factor while in the DS groove. The great energy retetion makes it easy to continue circling on the backside even if you get out of the optimal groove. I learned to DS with my Renegade on a hill with an often tricky DS zone, where the boundry layer is constantly shifting and is often fairly close to the ground. I could sometimes get the Renegade going pretty fast, but in shifting conditions I would often find myself running out of speed quickly, forcing a quick escape to the front side. The Opus will generally shrug off this type of thing, retaining enough speed to easily circle on the back side in less then optimal conditions. When DS conditions are good, and you get smooth, fast winds, and a nice boundry layer, the Opus will be absolutley screaming FAST! It should be noted that in low wind DS, the Opus is really the most comfortable with fairly round DS circles, versus the "bang-bang" eliptical pattern with hard turns on the top and bottom. The plane tends to bleed off more speed in these hard turns then other planes (the Nemesis comes to mind), but it will do them once it gets going.
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| Some shots from a couple of DS circles. You can see video of my Opus DS'ing here. | |||
Bad Habits: Most tapered wing sailplanes will tip stall if you try to pull them too hard through a turn at a given airspeed. The Opus is no exception, though it seems to be more resistant to this sort of thing then the other fast slopers I've owned (Renegade, Turbo, etc). That said, when the Opus does tip stall, it will give very little warning, and it will quite possibly "flick" (as the Brits say) quite violently. The first time this happened to me, the plane appeared to do a full-on snap roll. When I tried to recover from from the first snap without enough airpeed it then rewarded me with another snap in the opposite direction. Luckily, this happend high enough above the hill for me to finally recover safely. The Opus is not a difficult plane to fly, it just does not telegraph much of a warning as a stall approaches. Care must be taken when flying at lower speeds until you know the limits.
Aerobatics performance is good. I don't have much flap mixed into my ailerons, so the roll rate is respectable, but probably not as good as it could be. The weakest link, though, is the rudder fuction, which isn't very powerful (stall turns require early and judicious use of the rudder, for example). I suppose this might be a weakness of v-tails in general, but this being my first and only v-tail, I can't say for sure. One thing that becomes quicky apparently when doing aerobatics is that making large control movements often result in a shrill whistling sound as the exposed leading edges of the control surfaces bite into the airstream. It's kinda a cool sound, but I know it's just wasted energy. Once again, wipers would really help. Overall, though, it's a really fun plane to tear around the slope. I'd say it's more suited to large, carving/gracefull aerobatics then it is to the more violent/wild type of manuvering.
Landing: Pretty straightforward here. With the flap mod, the plane will slow down nicely and hover when pointed into the wind. The flaps will extend just a bit below the fuselage, so take that into account if you are coming in on a hard surface with the flaps fully extended.
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| Coming in for a landing |
The more I fly this plane, the more I like it. It's quickly become my favorite sloper. So, if you want a smooth, fast airplane that's lots of fun, I highly recommend the Opus.
(Another version of this review can be found on LiftZone).
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