Lentus: Elapor at Its Best!
Inspired by prestigious modern full-scale gliders, does the latest Multiplex offering make the grade?
It has been six years since the Heron was released but its big brother, the Lentus, has been finally announced at the end of last year and it is already a dazzling success as Multiplex was quickly out of stock and had trouble meeting demand. With a 3m wingspan, semi-scale look, wings and flaps, towing hook, retractable gear and speed sensor as possible options, the Lentus sets the bar high on paper. Available in a simple kit or ready-to-run (RR) versions, it is the review of this second version, almost ready to fly, that is the focus of this article.
A Particularly Successful Aesthetic
Multiplex has had a very nice pencil stroke with this Lentus, which is inspired by prestigious modern full scale gliders right up to its name. The wing planform is indeed reminiscent of that of the Ventus and the fuselage rather the shape of the fuselage of an LS8, this could indeed explain the name Lentus. In any case, it’s very well done, curves are elegant, well balanced, and this from any view angle, personally I love it! And as we often say that ‘what is beautiful flies well’, all this is a good omen for the chapter about flying! Multiplex’s know-how in the world of foam gliders is well known, so let’s take a closer look at the contents of the kit.
An Ever More Complete Kit
When opening the impressive cardboard box, which can also be used as for transportation, you will find the different elements carefully packed and wedged in bubble plastic sheets. First of all the two wings: In this RR version, they are completely finished, decorated and equipped with two servos per wing. The molding quality is impressive, no mark of extraction nozzles or injection points. The surface is perfect and slightly glossy. On the lower surface, you can distinguish two carbon/aluminum spars, the longest of which goes all the way to the winglet. The second spar is shorter and goes up to the mid wingspan. This should provide good bending and torsional stiffness to the wing. The control surfaces also have aluminum insert as a stiffener. The wing decoration is finished with a very good quality adhesive decoration and perfectly adjusted. The leading edge is protected by a transparent adhesive. The four Hitec HS-65HB servos are perfectly integrated in their housing, with a plastic cowl protecting the servo horn and its control rod. Wires are neatly routed in their guides and covered with transparent adhesive. At the root is the large plastic rib which integrates the housing for the opposite wing joiner ends and the wing lock system. Unlike the Heron, this time the fuselage wing connection is using a green 6-pin plug, a very welcome addition!
The tail plane is stiffened by a flat carbon rod, and is screwed to the top of the fin by two plastic screws. The elevator control is based on the Heron system with a simple bent piano wire that connects into a plastic part with an integrated sliding tube. It is extremely convenient to assemble or remove, and absolutely slop-free!
Let’s now move on to the Lentus’ pretty large fuselage. It uses the Multiplex M-Space technology which consists of a large carbon tube 20 mm in diameter in the rear boom that ends with a plastic reinforcement that goes up into the fin. The latter receives the two Hitec HS-65HB servos for elevator and rudder. The top of the fin ends in a plastic inserted part which receives the tail. The front of the fuselage is reinforced at its bottom with a 10mm square fiberglass tube plus fiberglass flat rods on the sides. The canopy is perfectly adjusted, and seems to use a softer and therefore less brittle material. On the other hand, the canopy seat is hopelessly empty! A pilot, even a simple silhouette would be more than enough and would add much more realism in flight! The canopy lock uses a clip system. I find it lacks a little firmness, so watch out for it during the first flights. For the brave, the addition of a small magnet at the front can secure it.
At the front of the fuselage, which really offers a lot of space, the ROXXY C35–48–990kv motor is mounted in its plastic housing which also reinforces the front end of the fuselage. The speed controller, a ROXXY BL-Control 755 S-BEC is mounted on the side. The wiring is clean and wire lengths are suitable for any kind of cabling layout. The landing gear location is closed by a removable Elapor part which can be glued with cyano if you don’t want the retractable landing gear option. Just behind the motor is a space for the towing hook servo. The servo is optional but the hook system is provided with accessories.
That’s it for the overview of the kit. The quality of the moldings or assemblies, the technical solutions chosen, the choice of radio or motor/ESC components, everything is well thought out and carried out, this is really a premium kit and Multiplex shows once again its know-how and its advance on the foam models market.
Assembly in Less than Five Minutes
In this RR version, the only operations to be carried out are gluing the Elapor part to close the wheel hole, sticking the adhesive pad which is a thick and flexible vinyl that ‘hugs’ the shape of the fuselage without making folds, and finally mounting the receiver. I made a corrugated plastic cardboard receiver support to position the two antennas at 90°. The support is then slid in the bottom of the fuselage and blocked with some foam. I also added a small wire between the wing locking pin and the fiberglass rod on the side of the fuselage so that I never lose the pin which always remains in the fuselage.
Let’s quickly move on to the programming of the transmitter to take full advantage of its quadroflap configuration, which starts with three or four flight modes: a normal phase, a thermal phase with a little camber, eventually a second thermal phase with more camber, a speed phase with the control surfaces slightly up by 1mm, no more, and a landing phase. All phases are using the quadroflap mix (ailerons to flaps) to have a better roll rate in any situation. The left slider manages the motor throttle and allows launching with the right hand (I’m piloting in Mode 1); the throttle stick continues to manage the air brakes like a ‘pure’ glider. Here we are ready for the first flight. I forgot to tell about the flying weight which is a good surprise with only 2335g including a 2500mAh 3s battery. But expect to go up to 2600g in case you decide to install the retractable landing gear and some other options.
A Real In-Flight Presence!
Let’s start with the motor, ESC and propeller combo: I liked the Solius and Heron, I liked the Lentus just as much. The climbing rate is excellent at full speed allowing fast climbs of a few seconds under an angle of about 45°. I was able to measure a climbing rate of 7m/s. This is equivalent to about 20 seconds of motor to reach 150m. You can therefore expect 10 to 12 climbs for a 2500mAh battery, so plenty of flying time. My very first flight lasted 45 minutes with a small 1800mAh battery thanks to some small thermals here and there.
Let’s turn-off the motor and observe the glider’s behavior: first observation, the cruise speed is rather high, with a very good gliding ratio. The Lentus is stable thanks to the winglets, precise on all axes, the rudder is very efficient as the ailerons thanks to the Quadroflaps mixing! The glider clearly marks lift variations. The Lentus gives the illusion of a much larger glider as it swallows distances, easily crossing through sinking air areas. If the air is really bad, you can even escape quickly with the speed position. The Lentus can thus cover a very large flying volume, which makes thermal flying so interesting and highlights the flight strategy.
The circle holding is very good as long as you keep a minimum speed. However, if you slow down the glider and tighten the circle too much, stall is likely to happen, so you have to stay soft, particularly with this efficient rudder. The tip stall is gentle, comes out easily after half a turn, but nevertheless surprises you the first time, so be warned! You immediately understand that the Lentus must be flown in three axes at low speed, you engage the turn or the circle with the ailerons and the rudder, and then you maintain the rudder in the direction of the turn with the ailerons at the opposite, as on a bigger glider. However, in thermal flight with a low bank, it is possible to fly the Lentus only with the rudder.
By using a little camber, the glider nose rises immediately, so a some down trim compensation is necessary to retrieve the correct flying attitude for this flight phase. Increasing the camber (flap and ailerons aligned) increases the lift in the thermal, but also a bit of drag. I found that its use should be limited to the exploitation of thermals, the rest of the time the smooth airfoil gives a better compromise. If your radio allows it, I recommend you to program two positions of thermal flaps which will allow you to have a position with very few flaps allowing you to explore a wide area, and a second position to exploit a narrower lift zone. On the other hand, the speed position accelerates the glider. The Lentus flies even faster, still as stable. This position also allows you to better ride upwind, to escape from a sinking air zone, or to do a little aerobatics.
I admit that I wasn’t necessarily expecting the Lentus in this aerobatic exercise and yet the glider does rather well considering the wingspan, the aspect and taper ratio of the wing. The roll or four point roll with a prior dive to accelerate goes perfectly, vertical manœuvres such as reversal, Cuban eight or looping also. You can cheat a bit by using the motor to increase this amplitude even more. Wings bend very slightly during the resources at the beginning or the end of the manœuvres, but all in all, I found the overall stiffness at the level! Finally, inverted flight requires pulling the stick a bit with the original center of gravity, but improves if you move it backwards as the speed flight mode can also help.
Nothing to report concerning the landing phase, the comfort brought by the crow braking is real and allows to land safely on rather narrow areas. Also, if you are at high altitude and want to fly down and land quickly, just pull out everything, decide on the down slope angle and the Lentus will execute without accelerating until the final touch down!
Conclusion
What can I say at the end of this Lentus if not that it is a particularly successful glider both aesthetically and in terms of flight performance, especially considering that it is an Elapor glider with a 3m wingspan! The RR kit is flawless with only quality components and a well thought out and perfectly made assembly, not forgetting a contained flying weight. The Lentus offers a very wide flight envelope for a foam glider and will satisfy a large number of pilots, although it is not aimed at the beginner, as it is positioned more as a transition or improvement glider, with real capabilities, and more glider than ‘foamy’.
In any case, I can tell you that I really enjoy flying this Lentus, even though I am used to competition gliders. I never get tired of doing flybys or chasing thermals. In short, Multiplex produced a beautiful glider, which will bring you a lot of satisfaction. Good flights to all of you!
©2021 Pierre RONDEL
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