I’m partly to blame, just when he was about to give up, he watched me being a (bad) example flying in the rain, slope soaring a 150 Watts-out reinforced Mini Mag above a village with the only landing spot between the trees the three feet of long grass between the asphalted farm road and plowed fields full of snow covered rocks. Nobody but a fool would fly under those conditions.
While browsing the Internet I came on the website for the American magazine Fly RC. Most of the news stand print copy (unfortunately without the adds, which are also a vital part of the content) was available on screen, it was my first look in an American RC magazine in about five years. The German based authors leave out a whole lot of important stuff, most of it the bad side. So, to calibrate my English , I looked up reports for two airplanes with which I have personal experience, the Multiplex Fun Jet and the Graupner Junior S.
Reliable Multiplex
The Fun Jet write up was just about what I experienced. Good old Multiplex, just does what it’s suppose to. Take note that although employment wise he has moved on, the power systems offered by Multiplex were worked out by a SEFSD member. However, the authors universally report right after the first test flights, before durability sets in.
All of Multiplexes airplanes benefit from a heat shrunk on layer of packing tape on the leading edges of both the wing and horizontal stabilizator. Without that leading edge protection the performance of the airframe quickly detoraites. After about fifty flights some of the hinges start giving out (again tape or fiberglass) and the control arms begin tearing out. As noted in my book “So You want to Fly RC” I built over (50) flying wings, mostly tape covered foam. Even with all that experience one layer of tape in five still has to be removed and replaced.
At the club field in Mission Bay we are landing on either sand paper, or weathering shredded wood. In Hessialand on weeds and dirt farm fields. Both abrade even EPP and Elapor foam quickly. That pre-issue Multiplex Dog Fighter I saw the middle of August 2011 at a flight show already had a ruined wing leading edge at (25) flights landing on golf (ick) course like airfields. Fifteen flights on a Multiplex Merlin and the leading edge of the wing and fuselage forward of the wing to the nose are already beat up. We use Tessa brand 4224 clear packing tape here (the most expensive), it heat shrinks like iron on covering. A portion of a roll has been sent to our long time members at NeuMotors.
In comparison to Multiplex Deutschland, where only their recommended systems are proposed (no virtual dyno) Multiplex USA gives the range of power for which their airplanes may be expected to perform reasonably, the numbers have been confirmed to be right on, the motors consistent and durable if only mediocre performers. If they come with folding propellers they are Graupner’s. I received a personal call from them a while back (bottles clinking in the background, way after normal work hours), did I really stick an F5D one horse power motor in an Easy Star?
When (no, not if) an airplane hits the ground the nose (including the motor and propeller if they hang out front) takes nearly all of the impact, then the wings tips hit too. When it flips or spins the tail takes it. Although they can cast airplanes in foam molds that we cannot reproduce ourselves, there is a low structural limit on how much strength they can build in with just foam thickness.
All of my Multiplex airplanes have added strength from fiberglass with two part resin from the wing attachment to the nose. Most of them have a forward bulkhead with the motor BEHIND it, so the airframe and not the motor take the hit. Many are treated to a surface hardness (often the wing tips and belly) of very light fiberglass held on with water based hardwood flooring paint or heat shrunk on tape. As noted in my book; My airplanes are built better and last longer then anybody else’s, because they have to”.
If you break something of a Multiplex airplane they will sell you any and all parts at a reasonable price. Walk into Sure Flite San Diego and they either have them or will get them from Multiplexes Poway center quickly. An important consideration not mentioned in any of the reports.
The truth, the whole truth, and nothing but the truth. The Graupner Junior S
But the report on the Graupner Junior S test left out a whole bunch of bad things about the airframe, and left out some surprisingly good things about the motor and folding propeller.
Graupner was, in a poverty ruined after the last big war here in Germany the first to offer model things. Today as a company if the name Graupner is on it you may expect better then average quality, reliably at a commensurately slightly higher price. I buy Graupner not because it is the cheapest, but because their products (foam airframes excepted) are good to top quality. I am a master scrounger, if I am using their stuff it’s only because it works. One thing you in the USA are missing out on is that Graupner has great propellers, both fixed and folding. Although not all that good, at least if the name Graupner is on a motor it works for a while.
However, their initial foray into foam airplanes, at a price a fifth of most of their airframes, has gone bad.
The biggest censorship omissions were that the Graupner Junior S six foot motor sail plane is made from foam so soft you can’t even assemble it without dents and scratches, and that there were no adjustments to control surface throws other then at the transmitter. That not commenting on the miserably soft foam is an unacceptable omission! It dominates the construction and use of the airplane.
It has one speed, slow. Why that would be left out of the other reports I don’t understand as that is a critical part of flying.
It did handle well, if slow, and very predictably. The controls, if set up as Graupner recommended were well balanced. If you hit a turbulent eddy on landing you just corrected for it and went in and set down gently. The slow speed kept you from getting too adventurous with anything more then a mild (four times walking speed) wind. If it weren’t so fragile it could be used as a basic trainer. Considering it’s only application was hunting thermals (unless you consider just cruising around in slow circles) where that’s all the wind it would be subject to, they control surfaces were sufficient. That’s not always the case with beginner airframes!
Unexpectedly, it flew inverted well.
Both aerodynamically and mechanically the airframe was well thought out, everything fit. If you ignore the durability issues it goes together easily and quick. Only if you were careful to get the control arms perfectly centered would you later realize the disadvantages of no way to center the control surfaces to the servos other then the trim on the transmitter.
On the ground transport without surface hardening and securing the horizontal T stabilizator would never survive our landing conditions. That little threaded insert holding the horizontal stabilizator would pull out at the first tug. Even in Mission Bay the slight ruts and little rocks would leave scars starting with just setting it on the bench, that quickly accumulate. If Elapor and EPP are subject to abrasion too this near styrofoam would be quickly just gone.
Although time consuming, 25 grams per square meter fiberglass with either two component resin or water based floor paint went a long way to making the foam last. As noted in my book; The scars from the repairs are the proof that my stuff flies.
The write up did mention that the canopy comes off, I too had the battery fall out. A really good grade of electrical tape became the canopy latch.
I only flew the airframe 25 gentle flights before cutting up an intact flyable airplane for the electrical parts, I was just bored with it. At which time the Junior S plastic motor mount, not once subject to a hard landing, was found to be irreparably cracked.
Graupner will not sell you spare foam airplane parts, you break the airplane, buy another one. That important purchase consideration was left out of all the reports on their foam airframes!
The Graupner Junior S airframe kit has been withdrawn from the German market. If it is the case that all of the kits came from a single production run, there was no chance for the motors in the kits to have improved glue in the motor’s magnets.
My two Multiplex Mini Mags have a collective 600 flights on then with no major repairs, some of best flights were with a 45 gram Graupner motor and controller that came out of a Graupner Rookie, some really great flights were with Graupner folding propellers. With the motor mounted behind a forward bulkhead and lots of fiberglass (40 grams) they have survived crashes with no measurable damage that would have turned a balsa airplane into wood chips, smoking electric’s and write off mechanicals. Even a “normal” Mini Mag would have needed extensive repairs and replacement parts. Don’t try to copy my flying with your standard airplane!
Graupner rates their motors very conservatively, about 40% of what they can output. I used mine at power levels comparable to similar constructed motors, so maybe I shouldn’t blame them if my bearings give out, except that if you ran them as specified you had lousy performers. As for the magnets breaking lose, I would expect that by now word got back to them and they refined their specifications to their manufacturers (Graupner itself does no manufacturing any more) to deal with that.
The Junior S motor, spinner and prop did hold up well, a friends Gemini is still using the hub for folding propellers. That hub went on straight, didn’t vibrate or rust and just went about it’s assigned task with no need to think about it. That is not the case for the lesser expensive stuff! Those folding props last at least a hundred flights. How long I really don’t know as sooner or later I hit a rock on landing…
Graupner rated the 135 gram outrunner motor far below what it can accept, like 20 amps on 2S. I ran it at 35 amps (on the bench, in the air that goes down) on 3S until the magnets came lose at about 75 flights by which time the bearings were exhausted anyway. No vibration, no rust, everything concentric, no soft cheap shaft that bent, just one less thing to worry about until it wore out. Considering that the separate purchase of the motor/spinner/hub/propeller blades would represent about Euro 70 of the Euro 93 I paid for the kit, maybe I shouldn’t be so disappointed. But I had an extra (8) hours in fiberglass to get the thing to live at all that went to waste. It was just a dull airplane.
The same was true for the motor system with the Graupner Rookie, the airframe of which has equally aggravating characteristics. The Rookie airframe is made of the same unacceptably soft foam, the control throws are insufficient for all but no wind days. The motor and controler are worthwhile things. Originally rated for a 5,7X3 prop on 3S (8 bench amps), I run mine with a pair of Graupner folding blades (6mm hinges) at 18 bench amps. So far (70) flights and doing fine. Don’t let those “have to keep the price of the package down” cheapest props in their selection that come with a Rookie influence your opinion of their other great equipment.
The older folding propellers with 3 mm hinges date from an era where we were doing good to have a hundred Watts-out. Even cheap modern stuff can output way more then that, for a while. Get modern blades with 6 mm hinges, put the 3 mm folding props along with their hubs in retirement! Graupner and Aero-Naut specify the RPM limits of their products, there are enough engineers around the SESFD to help you with the math.
The Hype Fox Conclusion
This is one evil handling airplane. It has been flown four times, and crashed four times. If there is any joy in flying it, it is only because it looks like a „real“ airplane. The included propulsion is insufficient, even before it breaks on the first nose landing. The only successfully flights I know of they used the power to get to a slope where it reportedly soars on the wind ok.
The advertised Fox price has been dropping (now Euro90/$145 for a whole ready to fly airplane including a battery, it was Euro 110) as the mail order companies try to get rid of their inventory. The (4) servos are worth about Euro 7 each, the battery separate goes for Euro 15.
For now, put it in the attic. When you get over the disappointment, get rid of it. There are better uses for the time then constantly repairing an airplane that will not fly right no matter how much time is spent fixing and modifying it. It’s not worth ruining the other parts, like the replacement motor, propeller, receiver and battery with constant crashing.
If flying a scale like motor sail airplane is desired, get a Multiplex Cularis.
Flight 4? Wiesbaden Bierstadt Reithof Neiderfeld Mid September 2011
big puffy clouds clear because it’s been raining breezy I like test flights with a little wind, it’s already nearly up to flying speed that way.
Up in the air, the little replacement 45 gram 100 Watts-in at probably .65 efficiency door-bell motor with the new 6X3 Aero-Naut folding blades (3mm hinges) and the used Graupner hub for 3 mm output shafts vibrates, but it pulls it up. As expected from it’s size it really needs more like a 70 gram motor on 3S or 4S. My estimate is that this six foot EPP motor sailplane needs at least 200 Watts-in at .7 efficiency on about a ten inch folding prop to function well. With this about equal to the original set up it takes about a count of (20) to get to 65 meters up.
The balance was confusing. The wing is straight to the airflow with no wash-out. If the wing tips are dropped slightly from crashes, since they aren’t warped that is ok for first flights. A simple fix that’s both effective and quick is inletting some small carbon fiber rods into slits in the wings. Usually a straight swing balances on the spar, but there are two hand drawn Xs further forwards that might have been meant for the balance point. In the air it acts tail heavy. But, put it into a shallow dive and it does not pull out on it’s own which would demonstrate being nose heavy. In flight this thing rears up and down in addition to rolling uncontrollably.
When it glides ok it glides flat, better then anything else currently in the collective fleets although another similar, but bigger, Fox with it’s replacement Multiplex Cularis wings might be as good. The older member with his aging reflexes couldn’t get the hang of his with the from the factory wings. As an observer it looked like he was trying to get it to fly too slow. After flying the smaller Fox I have my doubts if there is any satisfactory flight profile!
The Fox handling is evil. Get it sideways and it’s a problem to get it flying straight again. It’s so bad I never did get a chance to do a coordinated aileron/rudder turn.
There is no way to increase the throw of the original aileron servos, and they aren’t effective enough. Although the rudder is inefficient with the big hinge gap (easily improved) that isn’t what decides on flying. The elevator is effective only if the airplane is otherwise going straight, loops can be small, if entered from level flight with the fuselage aligned with the airflow.
After ten minutes of uneven flight, if this thing gets crossed up it’s hard to recover, it was brought in for landing to try moving the balance forwards. Just as I decided I’d missed the eight foot wide farm road to put down in the cut wheat stubble the wind caught it. It blew up about 1,3 meters, fell over to one side and landed on the nose to flip over hitting the wing tip and bending the rudder.
When it went into a spin with the original owner flying it that ended with a head first crash into a wheat field we thought it was a case of an inexperienced pilot and maybe the balance was off. I have loads of motor glider experience, I couldn’t get this thing to fly satisfactorily either.
The replacement motor, bought used in Lampertheim for Euro 2, popped out of it’s mount. On examination on the bench probably no new damage, it may not have been in perfect order even when I bought it. A piece of fiberglass secured with hardwood flooring paint chipped off. The ruder bent back straight, for now, so no real new damage.
It took about (4) hours to get the airframe in shape for a new trial.
The nose was worked over with fiberglass. That included a strip of carbon fiber down the inside of the nose to stabilize it straight after being bent by impact, a layer of thick fiberglass in the battery tray and thinner fiberglass over the outside for future durability. For now the nose is blunt, the front was cut off back to the factory plywood motor mount.
The canopy hold down was fixed.
The wings had the casting flash on the leading edge. That can be disaster in flight causing the airplane to constantly veer up or down. The wing leading edge was rounded, a layer of clear packing tape heat shrunk on.
The control surfaces were adjusted to neutral.
It was fitted with a new Spektrum 5 channel receiver.
To get balance, unexpectedly, a 3S 1100 mAh 90 gram battery had to go all the way rearwards. Odd, the fiberglass didn’t add that much weight forwards of the balance point.
Es geht hier um ein Scale Motorsegler die fuer Wenig Geld komplett gekauft wurde. Leider, teils Unerfahrenheit, wurde es mehr Mals hart gegen den Boden geflogen. Eigentlich ist es nie erfolgreich eingesetzt worden. Im Übernahme zustand ist die Nase zur Seite gedruckt, aber es ist noch versprechend.
80 Rumpf ohne Kabine
Kabine
27
Flügel Rechts
090 Flügel Links
Die Flügel sind weitgehend unbeschädigt. Die Servos sind über Kipphebel an den Leitflachen gelenkt, beide Funktionieren noch. Auch wenn sie an einem Spektrum (nie wieder in der Luft zu gebrauchen) Empfänger angeschlossen nicht richtig zentriert sind. Doch die Vorderkanten sind noch spitz. Das kann verheerende Flugeigenschaften verursachen. Es bricht andauernd entweder auf oder ab. Dabei sind die wenige Minuten mit einem Schleifklotz sie abzurunden unentbehrlich. Das die Flügel unterschiedliche Gewicht aufweisen ist an den angemessen Preis ok.
Die Aufkleber ließten sich mit der Bügeleisen noch befestigen. Weil die eine Seite am Rumpf fehlt wurde der Andere entfernt.
Der Rumpfs ist anschient nur leicht beschädigt. Hauptsächlich die Nase ist gestaucht.
Doch wahrend der Servo Untersuchung wurde festgestellt daß das Höhenruderservo nicht halb so schnell regiert wie das Seitenruderservo. Die Verbindung wurde gelockert, das Höhenruder hundertmal auf und ab gebogen (üblich für Schaumstoff Scharnier) und es geht besser. Beide wurde zentriert.
Ein Stück hinter die Kabine das zu verrieglung der Kabine dient wurde am Platz geklebt.
Die Vordernase wurde getrennt. Das Stück Hartholz ist zwar gerissen, doch so schnell wollen wir es nicht los.
Als erstes wurde ein Kohlestab am Boden der Nase geklebt.
Die Schaumstoff Streben wurden entfernt damit die Wände glatt sind. Danach wurde eine Lage …
Von meinem Buch „Schlag gegen den Boden oft und hart genug wird alles kaputt gehen“. Leider, obwohl der Motorregler noch Kraft an den Empfänger liefert, kommt am Motor nichts an.
Der Motor ist ein Außsenlaeufer von Türklinge Konfiguration. Was das in lexter Zeit außer Mode gefallen ist. Die Klappluftschraube ist von einfachem Konstruktion, doch wie es aussieht könnte es weiter gebraucht werden. Leider, obwohl der Motor immer noch dreht, ist der Innere welle gebogen. Kein Wunder bei dem Sturz (ich war vor Ort) den er erlebt hat.
Martin went and spent the Internet Euro200/$290 for a fully fitted out Multiplex Merlin. Although it looks like a smaller Easy Glider Electric, it isn’t! Flying it a little heavy with a 3S 800 mAh instead of the recommended 3S 450 mAh, it looked like a blast to fly. Stable in the wind with enough spirit to be fun. He showed it the second Sunday in August on a breezy day to Rudy and I. It just flew and flew. Poor Martin was on the edge of his ability, his reflexes tired before the battery(s) went flat. Me, I was so badly fogged I didn’t even bring an airplane to fly. Even though with the 5 channel receiver there is no adjustment for the useful differential of the ailerons, or configuring them as flaps/spoilers, it looked like it handled well. A handy thing that there were more experienced members in attendance. The Ds6i transmitter allows for wonders, if you a 6 channel receiver to run the aileron servos separately. Out in the wind my mind cleared a little. And it was fun flying with Rudy, who demonstrated taking off from the ground with a Twin Star II fitted with worthwhile motors and landing gear.
The Merlin complete package included a worthwhile fabric cover for to the foam shipping box the airplane comes in making transport with the removable wings and horizontal stabilizator really handy, and one battery.
One thing we wondered, could Jacob fly it on the property back in Jamul California? No, it’s too fast. Unexpectedly the Multiplex USA power combination for the first time is optimized for 4S.
End
