Dedicated to the Promotion of Electric Propulsion in all types of Aeromodeling

A Fun Ray from Multiplex Repair(ed) Experience

By Carl Murphy

In Which We Patch Up a New Fun Ray (Multiplex)

This is the first time I’ve had a fine quality Radio Ready (RR) to fly modern RC airplane in my hands, a current RC airplane as semi-hotliner (it came out seven months ago) which needed repairs before ever making a decent landing. Not including the 3S LiPo it cost €390/$440- in addition to which the new 3S LiPo was wrecked. What luck, we have two more LiPos sitting around ready. How much, materials cost and labor, to make an airplane out if it again?

More Foam RC Airplanes than the Law Allows

I have lost track of how many foam airplanes I have assembled, with the count for flying wings at fifty-five (I haven’t assembled any in a decade) and often assembling kits for others it is over a hundred. Until recently most of them had to be reinforced, as in Rhein-Main we enjoy flying close to home, without a mowed, free of rocks, grass as a crop landing zone and in SoCal I don’t usually have the Mission Bay (sandpaper) field to land on. All of my personal airplanes the propulsion was tuned. There were a couple of thousand carefree flying sessions, mostly airframes from Zaggie and Multiplex. Which included some duds (the Xeno flying wing, a single flying session, and a similar built up balsa) and a hard stalling semi-hotliner, the Blizzard (five and ten flights respectively). I issued a series of articles in which I bought up a used, owner assembled ARFs, dissected them, and, if they were worth it, fixed them (Twin Star II), or, discarded them (The Too Old Gemini, The P.O.Deleted DT-80, The Too Old First Generation Fun Glider, The Fun Glider).

A goal is not so much fly the Fun Ray at our home (farm) fields so much as those great places we keep reading about in Southern Tirol, Bavaria and Austria. Get the hang of it here and go fly there. So far though, its been hanging out with the locals as there was no wind. With a Fun Ray he’d have taken to the air. To date my personal slope soaring (zu Deutsch Hangflug) is mostly a distant memory of Estancia in Costa Mesa CA (before the trees wrecked the lift, nobody slope soars there anymore) and a single session at Point Fermin CA (difficult landing) decades ago. An alternative would be Torry Pines in San Diego CA. The Fun Ray is tough enough to land at Point Loma, until the drones got us run out of there. Our nearest slope soaring to our west end of Rhein-Main is in Appenheim. Three sessions for the other pilot, were enough to wake up his interest. Me, at a three hour round trip drive my two times there was no wind.

This is an original how to article, mostly to stay in contact with a friend with vastly better legal skills, made available to the Silent Electric Flyers of San Diego this year 2020. Were this a typical motor mounted at the rear, wonderfully built up out of balsa, plywood and iron on plastic covering, after planting the nose from a thirty-three feet up (ten Meters) there would be nothing to fix. With the motor front mounted to a combination of fiberglass and plastic reinforcement joined to impact resisting Elapor foam, it got a second chance.

Don’t fly with a Hangover, after Dental Surgery, or Something this Hot when out of Practice. Just before I bugged out (zu Deutsch abhaute), of what was expected to be six months, for what turned into two years in Way Northern California and SoCal, we in Rhein-Main had started with two motor-thermal RC airplanes, again from Multiplex, the Heron and Solius. The Heron was purchased RR, it is a fine flier requiring no changes of any kind. I built up a Solius from a kit (see the archived report) and although I deleted the belly wheel and beefed it up (with scab on fiberglass the nose and wing leading edges) it was my assessment that, for a vast majority of pilots (those with a reasonable place to land) that there need be nothing done to improve these airplanes. To us they seemed slower in “real life” then the videos or on simulators, they are not beginner airframes. I tried, I couldn’t break my Solius in the air, although the motor could be improved, that wasn’t for most worth doing. Just buy a RR Heron or Solius and go fly was our assessment.

Nothing but carefree flying after you accepted that snagging the wing on landing was going to happen. My estimate was the average time between catastrophic failures was fifty landings. For the first time RR RC airplanes that really were finished right, right out of the box! Catch a wing on a frozen molehill with a wing though (we both dented up reinforced foam airplanes the previous December year 2019) the expectation was then write off the airframe and start over. As such the inexpensive Roxxy outrunner motors are a match for about the number of flights to be expected out of any long, thin winged, thermal hunter. Something else to be reminded of, the width of the correct center of gravity is a band about a quarter of an inch wide (circa fünf mm) or an eighth of an inch on either side of those cast in balance points.

Although having hard plastic wing and horizontal stabilization leading edges vastly improves the durability of the Fun Ray, the basic assessment is the same.

At the end of year 2019 it was demonstrated to me by a semi-pro RC pilot that what I had been interpreting as turbulence, a sunlit slope surrounded by vineyards RC flying field (ideal for a Fun Ray) at almost, but not quite, freezing temperature, was in fact thermals. But, for a decade at an €uro per km and fifty km round trip, I not only couldn’t afford to be a member, I couldn’t even afford the drive. For a little while that has improved. The Fun Ray is a wide ranging airplane, which could be enjoyed in San Diego, however benefits from flying at a place where you can look out and enjoy the scenery too. You can reach the AMA height restriction of (350) feet above the surrounding ground, from glide in level flight, in about four seconds of full amps with a Fun Ray.

The Reviews Were Great

We had an interest in something faster, not F5B or F5D (way too fast for our farm field flying place in Rhein-Main and way too expensive) and not the howl of pusher flying wings (been there, done that). Our respective Blizzards from Multiplex had lasted just five and ten flights respectively, most of a decade ago. After taking a two year break for a really fancy aquarium and enjoying his daughters while his airframe and power mechanic was off in California trying to get reestablished in construction, a Fun Ray was purchased. Arriving already built, Radio Ready, for €390/$430- (plus a new battery) it took hours to program the four control surface wing. He had to relearn the programming and that he could have copied the settings over from the Heron, which also a four control surfaces wing. The Fun Ray has already hardened leading edges, wing and tail both. That is vitally important when landing on grass as a crop with mole hills containing rocks hidden and sometimes frozen. Although no match for a $2500/€2250- (plus radio and so on and so forth) F5B racer, it should be in the near hotliner category, able to be flown by an experienced RC pilot. We were hoping for a Blizzard replacement, without the dozen hours of assembly required but mostly without the disastrously abrupt, hard stall of that airframe.

It comes out of the Box Ready to Install the Radio and Battery, then go fly.

As noted in the Solius article, you only have a very narrow (quarter of an inch, (5) mm) wide band for balance, it was flown with the recommended battery, which would should put the Center of Gravity right on. Unfortunately, the pilot out of flying form, making a downwind turn stalled it from ten foot up into firm mud ending the first flight. In practice a near competition capable RC pilot (he also flies in gliders, I in bush planes), out of practice, maybe too trusting that the correct capacity 3S LiPo would place the balance correctly, it may have been tail heavy. A couple of months later we had a fine time with our (way overpowered, as in take off straight up) Fun Cubs, Gemini and Mentor (landing gear omitted, reinforced for our somewhat rough landing on grass as a crop field) at which we deciding we liked flying RC again. At the start of year 2020 the mostly intact Fun Ray was delivered up for evaluation. The nose was bent back a little past the canopy, there were some compression ridges along the fuselage, but, it otherwise looked repairable.

A check of the Internet for spare parts was €80/$88- for a complete, already built fuselage (pry the tail servos out and reuse them, re-glue in the wings power connections), a whole kit costs €140/$155-. A recommendation, you can’t buy new, equal quality parts and assemble a Fun Ray for what Multiplex will sell you a completed one for. Other then possibly the motor and propeller blades, unless you have suitable stuff laying around, for less than the assembled Airframe and Power. Depending on how you buy it the Roxxy motor costs €48,50/$53,50- to €70/$77- (Scorpion about $120/€108-, Sport Hacker a little more), and, I had a couple of similar motors, brand HiMax, near new (read the upcoming Mentor as a Motor Testbed article) sitting ready to use that could bolt in. A basic evaluation was that if the wings are OK, maybe this Fun Ray can/should be fixed. That €80- plus an estimated three hours to pry the servos out, pry the wing connectors out and reconnect them into a whole sets the upper limit of repairs. If the motors bearings are damaged, we have other motors waiting. A whole kit costs€140/$154-.

First Evaluation and Start the Repairs

The screw attaching the spinner to the folding propeller carrier could not be made loose, the end was ground off. At which the remains of the screw came out. A new screw and a washer were later fitted.

The propeller carrier came off easy, it, and the folding propeller blades appear OK. For such a simple assembly it works well. Similar from Aero-Naut costs €50- and performs only slightly better. Here in Germany replacement blades from Aero-Naut are easily available. Reportedly the 12X6 of the Heron already has a chip out of it. Those moles dig up rocks, their little dirt piles weren’t even frozen into icebergs.

The motor came out easy, it may not have been damaged. Run up on the bench it felt fine.

Although sometimes we can straighten Elapor foam, the cast plastic bracket holding the motor was broken, the foam precluded pulling it out straight.

The damaged Elapor was cut away freeing up the motor mount.

Although the nose bracket which is the motor mount and attachment to the fuselage spar was partly broken away, what was left was enough to reestablish alignment, it was glued back on.

Taping the canopy on for reference, the foam was cleaned up (cut away what could not be saved, clearenced the rest) and “stabilized” with a layer of lightest foam ((25) grams per square meter or (3/4) ounce per square yard) and Hobiepoxy two component resin. For that first go we are just using the fiberglass (zu Deutsch GFK) to fix things in alignment. Although you can handle it after a couple of hours, it is at least a six hours wait, better overnight, before being able sand it. This stuff really loads up sandpaper, a couple of hundred strokes and that piece done.

Time session one: An hour and a half. Materials cost about €2- for sandpaper, resin and fiberglass cloth.

Rebuild the Nose

The fiberglass was lightly sanded. More was added locking the assembly together and in alignment, although the length of attachment to the black fiverglass spar the length of the fuselage is insufficient for use. Depron (a lightweight foam material, see indoor fliers) was built up with the expectation that the entire load, previously carried by the white plastic motor mount to the (square) fiberglass beam nearly the length of the fuselage, would now have to be carried out and around the outside by the fiberglass transferring the load to the foam. Enough new foam was scabbed back on over the first layers of fiberglass to be sanded smooth (making a form) and the first of successive layers of fiberglass was required.

Time, sessions two through four, about three hours costs about €8- for sandpaper, resin and fiberglass cloth.

Time, for the final, fifth session, another hour of fiberglass overlay and sand, about €4- for materials. A personal choice was to not make it look “spiffy” (zu D. ein seit Generationen nicht mehr im gebrauch genommen Amerikanisch Sprachgebrauch was etwa “dufte” also sieht gut aus, entspricht). You can’t see the difference in flight and the slight unevenness probably makes no measurable difference.

The Motor and Propeller Carrier(s)

The motor was mounted in a Mentor (see the motor test bed article) and run up. Keeping in mind that the distance between the blades is a little wider than usual, were the other motor to be installed, despite the testing in a Reinforced Mentor, the power would have to be readjusted. With Multiplex 11X7 folding propeller blades on a 3S 3200 mAh LiPo it drew (37) amps at (400) watts-in. At the narrower carrier it would probably take 12X7/6 folding propeller blades to get the same power draw. Even with a watts-in/watts-out efficiency of (65)% that ought to move it up and out fast. The same weight Mentor will go vertical at that power and the propeller will cavitate in level flight! What sets the limit is that although slick, the cast in moulds wings are thicker than their sheeting over foam or fiberglass similar.

Speed costs money; How fast (and how often do you want to make repairs) do you want to go? The time for flight, if not thrilling at last satisfyingly fast, verses the time and expense to fly, spikes at the Fun Ray. Built up costs less and can be faster, breaks at the first hard landing, repairs are required after almost every flying session. The assessment for this beat up nose Fun Ray, after trying to get a lower quality motor mounted for a few test flights (motor wires too short) and a HiMax motor bending the leads at the motor case was too much risk, was to reuse the Roxxy motor. Something unexpected though, once warm from being run the bearings dragged, something experienced with four similar sized HiMax motors and not a single Scorpion or Sport Hacker motor. That took an hour.

Total time for the repairs is probably in the four hours range, materials in the €10-. The repair isn’t pretty, will however hold. Crash it again and the new crease will be further back, you can’t reinforce this type of airframe the way the slower, less exciting to fly, blunt front end, semi-scale Fun Man and Fun Cub. See above; For €80/$88- plus an estimated three hours to remove and reinstall everything in a new, factory assembled, fuselage sets the upper limit on repairs.  We determined that the transmitter is ok (flying the stuffing out of Reinforced Fun Cubs), the RC pilot has his (just under competition) flying skills back and my basement workshop was full, it was returned with the request to fly it.

Although weather has been warm all the first half this winter in Rhein-Main, no ground freezing so I can’t walk the fields and find my 14X9 flew off folding propeller assembly (two sessions of mud wandering are enough) with a rain front on the way. At that power level I’m going to (6) mm output shafts where available.

The owner is working, I’m doing my USA tax return and thinking about working again. I’ve been flying RC with electric propulsion since year 1995, this year 2020 I bought my (22) bicycle, my first electrical power assisted E-Bike. For the five hours or so the battery charge it lasts it gives a sixty year old the bicycling strength of a forty year old.

I’m planning on being back in California the start of February year 2020. So, if the scrounge looking (I get my hair cut in Ocean Beach) older guy on a faded red, pedal only, bicycle seems to know a whole lot more about RC flying then the similar appearing Mission Bay bums; It’s me. The intention is to be back in SoCal for the Super Bowl as during that five hours no Game Warden is going to be interested in what I’m up to. I can (finally) afford to pay cash to have that NeuMotors 1107 I bought from the Editor (a decade ago) fitted with a transmission, need although some fine dining to trade NeuMotors for the labor though. Unless I bring a kit with me, Multiplex products are no longer distributed in the USA by (previously) HiTeck. NeuMotors isn’t the only place I barter, those bums pay for their bike repairs in welfare vouchers and that’s what I tip my hairdresser…