In a world filled with so many 1.5 meter and 3 meter race planes, the Opus V fits nicely into the under-populated mid-size slope glider class. With a span of about 2 meters, the slick Opus looks a bit like an undersized F3F racer. Its smooth, high-speed performance has made it a popular slope sport plane in southern California. The Opus is big enough to have the smooth handling characteristics and speed of a larger plane, yet it's less expensive then a full blown unlimited F3F ship.
In a world filled with so many 1.5 meter and 3 meter race planes, the Opus V fits nicely into the under-populated mid-size slope glider class. With a span of about 2 meters, the slick Opus looks a bit like an undersized F3F racer. Its smooth, high-speed performance has made it a popular slope sport plane in southern California. The Opus is big enough to have the smooth handling characteristics and speed of a larger plane, yet it's less expensive then a full blown unlimited F3F ship.
I bought the Opus because of its reputation as a fast, tough, high quality slope plane, and I was not disappointed.
First Impressions
The Opus came packaged in two boxes, a small one for the v-tail, and a gigantic one for the wings and fuselage. Everything was well protected with lots of bubble wrap. The first thing I noticed after taking the Opus out of its box was the quality of the gel-coated finish. The mirror smooth surface on the wing, tail, and fuselage is flawless, and the 3-color paint job is crisp and bright (the Opus is available in either a white or yellow base color, with a variety of trim colors and designs on both the top and bottom of the wing). The overall fit of all the parts is also very good, except for a bit of gap where the rear wing fairing mates with the fuselage. This is a pretty minor thing though, as the fit of the wing on the wing saddle and the v-tail on the rear fuselage are excellent.
I should note that I wasn't sure about the fit of the wing to the fuselage at first. 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 assembly 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 with no effort required.
Description
The wing is a single piece unit, with a flat center section and slight dihedral on the outer wing panels. The flaps and ailerons are top hinged with live skin hinges, but unfortunately, there are no wipers on the surfaces (newer versions of the Opus feature molded-in wipers on all surfaces and bottom hinged flaps). Plastic horns are preinstalled on both flaps and ailerons. The servo bays are cut out, and molded servo covers are included. There is also a ballast tube is installed on the recommended center of gravity. The tube, which stretches out to the flap servo bays, holds 9 brass ballast slugs (included) that together weigh about 10 ounces. The wing is mounted to the fuselage with a single metal bolt at the rear, and with a curved tab at the front that slides in underneath the forward fuselage.
The wing skins have a Rohacell core, which is sandwiched between fiberglass. The Rohacell is quite a bit tougher then the thin balsa core skins often used in molded planes. This makes the wing skins stiffer and more resistant to dings and dents as well. The bulk of the overall strength of the wing is a provided by a carbon fiber capped spar.
The fuselage is made of fairly thick fiberglass, with what appears to be carbon fiber reinforcement through the wing saddle area. Whereas some molded planes feature lightweight, thin fuselage construction (the type where you can squeeze the sides together with your fingers), the Opus is very sturdy. The designers were not stingy with the fiberglass, and when you pick up the fuselage, its gives the impression of being quite stout. One of unusual features of the fuselage is the lack of either a canopy or a slip on nosecone. The only access to the forward fuselage is through the wing saddle opening. In theory, I suppose this should lead to a stronger structure, but it does complicate the radio installation.
Finally, the v-tail, which is a single piece unit, is attached to the fuselage with two nylon bolts. Construction is similar to the wing, though it has no spar. The elevators are also live hinged (again with no wipers on the version I have), and the ball link control horns are installed.
Assembly
Like many molded sailplanes, the Opus comes with absolutely no assembly or setup instructions from the manufacturer (whoever that may be...who actually makes the Opus is a bit of a mystery). Happily, though, the folks at RC Direct included a printed copy of Doug Reel's highly recommended Opus V setup information web page. Doug was one of the first people to popularize the Opus, and his web page provides great radio installation, construction, modification, and setup tips.
Wing
Each aileron servo bay has a piece of preinstalled carbon fiber that acts as a servo attachment surface. Oddly, the flap servo bays do not have this, so the first thing I did was to lay in piece of carbon fiber cloth in the bays to reinforce them. This prevents the upper wing skins from flexing when the servo arms move, and hopefully will allow the removal of the servo (if necessary) without damaging the upper wing skin.
Once the servos were wired up with a 4-pin Deans connector for each side of the wing, I was ready to install them. The servo bay cutouts are just barely large enough to accept a servo case, so using side mounting lugs or any sort of mounting system really isn't an option. Even with the mounting lugs removed, I found that I actually needed to sand down the sides of the servo cases quite a bit to get them to fit flush with the wing and properly fit under the servo covers. With this being the case, I had to use the tried and true method of using a bit of epoxy and a bunch of micro balloons to glue the servos to the carbon fiber base in each of the bays. I decided to wrap the flap servos with good quality masking tape, and then glue to the tape, rather then directly to the servos. This sounds a bit strange, but it does actually hold the servos in very well, yet still allows you to easily remove them (if a gear of a flap servo strips for example).
Since the wing's control surfaces horns are preinstalled, all that's left to do after installing the servos is to hook up the aileron and flap linkages. You can stop at this point, but there's one modification to the flaps mentioned in the setup instructions that I opted to make. The top hinged flaps of the Opus and the position and shape of the flap control horns mean that the flaps can only move down about 45 degrees. Because many slope sites in California often feature small or rocky landing zones, the ability to drop the flaps to a greater degree can be really helpful. At a minimum, the modification involves removing the existing flap control horns and replacing them with fiberglass horns with a shape that will allow the flap to drop to around 60 degrees. If you want more travel then this, you have to actually cut into this wing. With some trepidation, I decided to go this route, so I removed 1/16" of skin from the sub trailing edge on the bottom of the wing and 1/16" from the leading edge of the bottom of the flap. The 1/8" gap that this creates allows the flap to bend down without interference from the upper or lower wing skins. The drawback, of course, is the large gap between the wing and the bottom surface of the flap, but this is easily sealed with gap tape. The flaps now come down nearly 90 degrees, so to me, it was well worth it. The bottom-hinged flaps of the newer versions should eliminate the need for this step.
Fuselage
Two major tasks need to be accomplished for the fuselage includes building and installing the servo/radio tray, and installing push rods.
Since there's no opening in the forward fuselage, the servos need to be mounted either in the wing saddle area or on a removable servo tray that fits in the nose. I wanted to have the wing saddle area free for extra ballast, and I also wanted to mount the servos as far forward as possible (for nose weight), so I chose to make the servo tray. The setup instructions give measurements for building the 1/8" thick plywood tray, which holds the two v-tail servos at the rear and the receiver at the front. The tray sits on the floor of the fuselage, and the v-tail servos are glued together and in turn glued to the tray. The tray is then bolted in with two 4-40 screws that attach through the bottom of the fuselage and into a couple of blind nuts that are mounted on blocks attached to the tray.
Next, it was time to install the push rods. The Opus's tail boom has a hard foam former glued into it about halfway down. This is presumably to act as a support for solid metal pushrods, but since these are not included, the setup instructions suggest using a standard rod-in-tube push rod system, which is what I did. The first step is to remove the foam former with a sharpened dowel or something similar.
I purchased some appropriate length music wire and plastic push rod housings for the wire to slide in. Because I hate the idea of having to solder on a clevis coupler with the pushrod inside the plane, I opted to carefully measure how long the housings and music wire needed to be, and then soldered all the clevis couplers on before actually installing the pushrods in the plane. An important note here is that in order to remove the servo tray from the nose, you need to first slide it back a bit and remove the servo arms or else detach the clevises. This means that the pushrod housings need to be glued far enough back to allow you to push the tray backwards and expose the servo arms.
The path from the servos to the v-tail ball links is pretty much a straight shot, so installing the pushrods is fairly easy. Again using some advice from the setup instructions, I laid the fuselage on its side and applied a bead of GOOP glue to one side of the push rod housing. The housing was then slid into the fuselage, glue side up. When satisfied with the positioning, I simply flipped the housing over and let the glue take hold. The GOOP gives you several minutes to get the housings positioned correctly, but once dry, it holds tenaciously.
Finishing touches
The short nose moment of the Opus means you have to add quite a bit of lead to get the CG right. In addition to a 1400 mAh NiCad battery in the nose, it took around 7 ounces of lead shot to get the plane to balance right at the center of the ballast tube. The final touch was to add a Hollyday heavy-duty switch jack on the side of the fuselage. The final flying weight for my Opus is 48 ounces.
Flying
The first flight offered no surprises. The Opus was smooth and responsive, and little if any trim changes were needed.
I had heard that the thin RG14 might not enable the Opus to yank 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 nicely, better then my Renegade 60" racer in fact. It might not claw through corners quite like a large RG15 winged F3F racer, but its turning performance should offer plenty of excitement for the sport flier. (Indeed, the Opus is often used as an entry level F3F plane in southern California.)
Despite its 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. In really light conditions where the only lift to be found is very close to the hill, the weight is definitely a penalty. Throw a few light thermals into the mix, though, and this changes. With a bit of camber, the Opus will really climb out nicely, even in smaller thermals.
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 than the other fast slopers I've owned. That said, when the Opus does tip stall, it will give very little warning, and it will quite possibly "flick" quite violently. The Opus is not a difficult plane to fly, and I would not say that it stalls easily, but 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 its limits.
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. I did find that the nose was tending to rise during a high-speed dive when I was using the stock CG. I eventually removed a bit of weight from the nose, moving the CG back to the rear edge of the ballast tube. I also raised the leading edge of the v-tail up a bit using a few pieces of tape underneath it to reduce the incidence. This seemed to eliminate any major trim changes while flying at high speeds, yet still kept it smooth and stable.
Aerobatics
Aerobatics performance is good, but not what I would call spectacular. Because of the geometry of the flap linkage, I was not able to mix very much flap into the ailerons. Therefore, the roll rate is respectable, but probably not as good as it could be. The weakest link, though, is the rudder function, which isn't very powerful. Stall turns require early and judicious use of the rudder for example. Overall, it's a really fun plane to tear around the slope. I'd say it's more suited to large, carving and graceful aerobatics than it is to the more violent and wild type of maneuvering.
Dynamic Soaring
The Opus's high-speed handling characteristics make it a great plane for dynamic soaring (DS). The stability keeps everything smooth, and somewhat lessens the white-knuckle factor while in the DS groove. The great energy retention makes it easy to continue circling on the backside, even if you get out of the optimal groove The plane is probably best suited for dynamic soaring in medium to moderately heavy conditions, especially where you can fly a fairly large circular path, as opposed to a more elliptical one. Possibly due to the RG14 airfoil, the Opus gives up a bit of flexibility in lighter wind DS. It tends to lose speed if you try to pull it through an elliptical DS pattern that requires a very tight turn on the top and bottom of the groove. So far I've had my Opus clocked on radar as fast as 141 mph, and I'm pretty sure it's gone faster than that on a few days when we didn't have the radar gun available. DS is an obvious area where the Opus's heavy-duty construction comes in handy. I've yet to hear of an Opus having a mid-air failure while dynamic soaring (though it must be said that the wings start really flexing as it approaches 150 mph). Dynamic soaring is also a good excuse to do some high energy aerobatics. Wind the Opus up through a few DS circles, and then punch out on the front side for endless vertical rolls, loops, etc...almost anything you can imagine.
Landing
Landings with the Opus are pretty straightforward. With the flap modification, the plane will really slow down nicely and hover when pointed into the wind. At 90 degrees, the flaps will extend just a bit below the fuselage, so care must be taken to retract them at least part way before the plane actually contacts the ground.
Conclusion
The more I fly this plane, the more I love it. It's quickly become my favorite sloper. The quality is excellent and the plane has proven itself versatile and exceptionally tough (tough for a "moldie," anyway). If you want a smooth, fast airplane that's lots of fun, I highly recommend the Opus.
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