Odie sent in the pics below showing some of his 3D printed projects. The blue plane is a GB R3. This is a scratch build using mainly plastic 3D printed parts. Like many models of full size planes there were compromises such as increasing the wing area to reduce the wing loading. The chord was increased to 120% and the area increased to 160%. Other challenges include making the plane light but also stiff and strong. Wall thicknesses are alway in mind and must be kept thin as possible. He says one needs a good printer to maintain the structural integrity of thin components.
He started with an imported drawing of the plane and created the segmented parts in a professional version of Solidworks.
To keep the tail light he uses balsa for the stabilizers. This also helps with balance. He uses a slicing program, along with Solidworks, to help calculate the weight and balance on the computer before printing the parts.
Printing time is proportional to the amount of plastic used (mass). The GB took about 16 hours of printer time. As with most 3D printed planes, the parts are printed in sections and glued or snapped together.
I just put together the FMS T-28 Trojan. I painted to fuselage this morning. This went together way to easy. Still deciding on sticker numbers or make a stencil. My number is #00. See you on the course. – Carl Cox.
I’m using quarantine to work on a Sebart Avanti XS. It has a 120mm fan running on 12S. The fuse is fiberglass, the wings are wood, and it has a wingspan of 1.8m. For comparison, the plane in my hand is the Freewing foam Avanti S (wingspan 1236mm) that many of us have. I chose a carbon-fiber 17-blade fan (optimized more for thrust than for top speed). – Mark Davis
Hi, Fellow COVID Exiles.
Since I can not fly at either the electric field or the Chula Vista club, I have spent time on a new foamy from Motion RC. This is a FlightLine FW-190 44” model, a bit smaller than I like (due to my old eyes). The model is a reboot of an older design which now has added flaps – but not the proper “scale” split flaps : ( I guess the days when I would spend 1500 hours on an over-the-top scale project are probably over anyway.)
This plane runs on a four-cell, which is one of the reasons I got it, since I have several batteries that can be used in it. The battery bay is extremely tight and required some surgery to get everything in. The model is spectacular in detail and fairly good in terms of scale fidelity. I did it in the optional Heinz Bar #13 scheme, adding my own Photoshopped swastika which was missing on the tail (PC reigns). I decided to try some weathering which I have really never done before. My attempt is terrible compared to the incredible models I see on the internet – but I had fun and it isn’t too bad after all. A little black to hit the panel lines, ocher for oil leaks and where the guns dirty the wing, and blotched silver to look like chipped paint on metal… Everything on the model has been coated with some acrylic floor finish, which pulls it together – as well as sealing down the stickers which, on this model, were not good. The colors and detail was great but they really didn’t stick very well at all – especially the small/thin ones.
Today was spent binding the new RX and setting the throws, etc. Hopefully I will be able to handle this fast little plane, once the field is open again.
I hope all is well with all of you,
I have a plane that was featured in the latest April 2020 Model Aviation magazine. – Randy Mann
A co-worker kindly lent me his Ender 3 3d printer. I have taught myself to use it and am now printing missiles and bombs. In particular, Hell Fire missiles and GBU -12 Paveway laser guided smart bombs for my MQ-9 project. So am learning new skills and moving the MQ=9 project forward in these difficult times. I can recommend the Ender 3d printer as a nice and economical beginner’s printer as it is producing a fine product(s). – Bob Kruetzer
Like most everyone I have done some repairs to my airplanes. But here is something a little different. It’s flying related but not an airplane. In a prior life I had a video business where I would record various events and provide DVD’s and/or downloads. For this purpose I purchased a Servocity Pan and Tilt device (picture below). I would mount my video camera on it and using a hand held wired remote I could move the camera both left to right and up and down. – George Sullivan
Taking video of RC aircraft is a pain in the …. I always hoped I could use this device but aiming it was a problem. So the project I have is in 2 phases. The first phase is to convert the controls from the hand held wired controller to a wireless receiver and my Spektrum transmitter. This was surprisingly easier than I expected. I now have a 4 channel receiver mounted on the device and can control the pan and tilt motions using the right stick of my Spektrum transmitter. I will output the video from the camera to either a small monitor or perhaps a pair of goggles. Here is a short video showing the Pan and Tilt mechanism controlled by the Spektrum transmitter. (https://www.youtube.com/watch?v=TpZS2jtaciw )
The second phase is to solve the problem with aiming the camera. My plan is to put a “headtracker” on the output display (monitor or goggles) and input that into my Spektrum transmitter. So at least in theory the camera should point where I’m looking.
The first phase is completed . Phase 2 is waiting on the delivery of the electronics for the headtracker. I hope to get the electronics by 4/15. If all goes well, an update for next months newsletter.
Like the rest of us, I’ve been “hunkered down” in my case at Casa Gagliardi trying to keep my brain from going to sleep with way too much TV ! So let’s build something…..First it was the Wanderer Glider that Mike Morgan so graciously laser cut for me as it was my first glider back in ’75 after going to Torrey Pines and watching the action there. I had just been transferred here after Recruiting Duty with the Marine Corps in Indiana (can you say FLAT?)
I bought this FD 421 Cessna at Weedwackers and I’m just about done with it. – David Pothier
The stock mechanical retracts that came with the Hurricane were underperforming. I replaced them with the main retracts that normally come with the Freewing Avanti Jet. They fit pretty well with only moderate fiddling and fussing with the mounts. One of the great things about these retracts is they are very inexpensive. Only $50 for the set!
If you are looking for retracts for a project, check out MotionRC.com. They sell the retracts for nearly all their models. You can find all sorts of sizes, configurations and styles. – Steve B.
By Steve B.
Last year I bought the Avanti S from MotionRC.com. Although this is an excellent jet, I wanted it to go faster. The modification required replacing the entire fan assembly, the motor and the speed control. It was all pretty simple to do because al the new parts fit right in where the old ones were. No foam cutting, just a slight change to the ESC mount.
The test flights went perfectly. It is significantly faster than the stock setup. The flights are shorter due to the higher currents. Unfortunately, I forgot to get video.
In order to get the correct motor and fan, I took the easy route and went to our very own ‘motor master’, Steve Neu of Neutronics and asked him. If anyone knows how to make airplanes go fast. . . well, you’ve seen him fly, enough said. Steve created a special wind motor just for this application: NeuMotor inrunner 1412/2D/S/5mm with a Kv of 2400. In this application the motor is using 2700 Watts. The stock motor’s Kv was 1900.
The stock fan that comes with the Avanti is plastic and specially made to mount on their outrunner motor that itself mounts from the rear. The motor and fan are cantilevered off the back of the motor. Seems crazy but it works. This fan cannot accept a motor that mounts from the front. Turns out they have fan housing made of metal and it fits a front mounting inrunner (p/n P0806). I used the fan housing but the fan that comes with it cannot mount to a standard motor shaft. So I purchased a Jetfan 80 V3 from eJets in France. It is made to fit the NeuMotor 5mm shaft.
I bought a Castle Phoenix Edge 130Amp ESC to replace the stock 100 Amp ESC. Current at full throttle is 135Amps. The battery is the stock 6S 5000mAh Li-Po.
I’ll take you through a pictorial explanation of the conversion process:
Below you can see how I took off the motor hatch. The screw eyes made it easy to lift it off (after you remove the screws). Otherwise it is a pain.
By Frank Sutton
Alex received his Motion RC AL37 jet airliner as a Christmas gift. Of course, he was thrilled. As many of you already know, Alex plans to be a jet airliner pilot and is already flying actual sailplanes as a member of Cypress Soaring (https://www.cypresssoaring.org/) in addition to flying R/C planes with Silent Electric Flyers San Diego (SEFSD). He is preparing to solo in a Cypress Soaring sailplane later this year.
Alex assembled his brand new Motion RC AL37 jet airliner on Christmas Day, and he installed a known good SPECTRUM AR620 6-Channel Sport Receiver from another plane. Unfortunately, he soon discovered that the lights and retractable landing gear worked but the twin jet engines would not start. Alex spent many hours unsuccessfully troubleshooting the engine problem for several days. All of the receivers he tried would work fine and start the engines on other aircraft, but none of his receivers would start the the new AL37 jet engines.
We reached out to Motion RC’s Technical Support for assistance and eventually attempted to troubleshoot the engine problem via E-mail and text messages with Motion RC’s Technician “Andrew”. Unfortunately, all the troubleshooting by Andrew and Alex remained unsuccessful – the jet’s engines would simply make a beeping tone and not start.
We were planning to ship the engines and electronics back to Motion RC for troubleshooting when Andrew told us he lives not too far away in the Lake Elsinore area, and he invited us to bring the plane, or at least the electronics and jet engines, to his home to troubleshoot himself. We gratefully accepted his generous offer and met Andrew at his home in Lake Elsinore on Saturday afternoon, 04JAN2020, after Alex’s sailplane flight at Hemet Airport with a Cypress Soaring Instructor. Continue reading
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. Continue reading
Thanksgiving Day, all the relatives were in the kitchen helping out in prepping the turkey and the many other goodies going with it, grabbing samples, my wife is in the middle of making egg rolls and it was smelling good. Me, I was sitting by the TV watching football, my Kona Brewing Hanalei beer next to me, computer in hand and I was feeling pretty good that day. With my computer, I’m doing the massive internet searching and watching the football game. I like to check out Motion RC for their aircrafts (to my opinion) look pretty cool, for a foamy. I have had my eye on this one very cool looking aircraft, it was the Flight Line B-24 Liberator Olive Drab.
Then my eye caught sight of this airliner, Freewing AL37 Airliner Twin 70mm EDF, I’m like really, that just looks so cool and so was the price, $499.99. I still had to see what this was, watch some videos and as I was doing that, drinking my Hanalei beer and I was getting excited (PG). At this point I had to get some eggrolls so I paused. Picking my eggrolls, I start taking to my wife, Phi, (pronounced like paying a “Fee”) about this new airplane that I just found on the internet and of course she says back to me “Oh Jovi, here goes more money”. I said with a smile, you need to see it later……. Here’s the good stuff on the AL37:
- • Wing loading: 110g/dm2
- • Wing Area: 39 dm2
- • Length: 78.74 in
- • Wingspan: 72. In
- • Motor: 3048-2150KV O/R Motor
- • Servos: 9g MG digital servo (6pcs), 9g Hybrid digital servo (4pcs)
- • ESC: 60A with 5A BEC (2pcs)
- • Ducted fan: 70mm 12-blade fan (2pcs)
- • Weight: 7.385 pounds (w/o battery)
Also included were, Electric Landing Gear, with doors, scale LED lights and best of all the two pilots figures, why who else was going to fly this bird???? The Li-Po Battery needed, 6S 4000-6000mAh.
Phi, my wonderful wife gave me the go-ahead so when we got home from our Thanksgiving trip in Arizona, I got to Motion RC web site and “Pushed the Button”, it was order, now, patients for the deliver day. When order, I was told this was a pre-order, should ship mid-December.
Meanwhile while waiting for the Jetliner, I had asked Randy if he know of anyone who could make decals and I was looking to make my airline look like Hawaiian Airlines, my favorite way to go when heading to the Islands. Randy mentioned Callie Graphics. Found their web site so I left them an e-mail with my request. Couple of days later I got a response back with “heck yeah”. Again, I got excited… (PG).
Here it is December 10th and I got the e-mail; your order has shipped……Oh Yeah!!!!! A day later, Callie Graphics advise me that my order had shipped as well. This was great, very thing is falling into place. Besides having the problem with Fed-Ex and there so call on time deliver, my was delayed by three days. The decals arrived and I was very impressed with the way they came out. I was also surprised on how large these decals were. Well finial on Sunday evening the package arrived. I was like, box is not that large and I could not believe how light the package was. Open it up and was happy seeing how the packaging was very well done; each piece was well place in a cradle that was created in its shipping box. Once I look at it, I got amazed on how large of a Jet this really was….
On Monday right when I got home from work I started to work on AL37. Putting the fuselage together was really easy and it goes on straight. Now came the time to put the decals on. If anyone has done this, you know to use Luke warm water and some soap. This really helps in putting the decals on and getting them as straight as possible. I took the rest of the week to get it done.
December 28th, it was ready for flight. Randy was very kind to help me get it in the air. Check it out and soon it was in the air. This aircraft fly’s really fast. Randy flew it for about 4 minutes and then wanted to bring it down. And he did. It hit hard and had some damage. All could be repaired. By the following weekend the AL37 was ready for flight. This time Brad was at the field. I don’t how much I can thank Brad for taking the time, about over an hour and spent the time setting up my radio and making sure that AL37 was perfect. He check it out from top to bottom. Now it was time to fly. Brad got it up, flew it around trimmed it out and it flew great, hands off.
Then the moment was mine, with a freshly charge battery the AL37 was ready for flight again. This time I took control. Powered up, she started to roll, increasing the power she started to lift off the ground, I was excited….I flew her for about 4 minutes and let Brad have the last minute to bring her back. He brought her back on a very nice approach and he landed it very gently. WOW this is one fun airplane.
Without the help of Brad and Randy, I don’t think I could have done this on my own, got to take it home in one piece……Thanks again for the help you both provide me with my Hawaiian Air.
By Carl Murphy
Flight (10) 11 End of January year 2018 (So.) The wind swirls over the hills and between the apartment buildings where I live, so, I was way off, ninety degrees on the wind direction and half down on the strength. Up in the Tanus Hills, where I expected the wind to be blowing up the saddle, the wind was blowing up a forested hill and back down. Which is normally too turbulent to fly a plane of this type, except that, right at the saddle is a pocket of not much swirl and I’m here. The Panda flew for twelve minutes, just not right and it was quickly evident this is a still air airplane. I’ve been flying a medium speed, way up powered Mentor which responds directly to control inputs, I had to relearn how to fly with just ruder and elevator. Even full stick throw, which seemingly doesn’t do enough, until putting full amps to the Panda.
Flight 12 same day At the nearest slope soaring hill (38) km away. With rain or snow every other day and the winter darkness of this fifty degrees north latitude I’ve been stuck in a tunnel for months, I just had to get out some. This can be a gently slope soaring experience looking out over the valley. Instead the wind is blowing up the slight slope covered with trees, conditions aloft are turbulent, the view under the clouds a thousand feet up clear. The Panda flew for fifteen minutes, this time using all the down trim the transmitter had and holding the elevator down from stick neutral too.
Flight 13 I marked the elevator for reference, then moved the aileron one tooth at the servo arm. Now it needs all the up trim and some more holding down. The flight went twenty minutes. Considering the unsuitable flying conditions and that the battery still had a third more usable charge there was more to be had.
I put my Reinforced Mentor in the air, what a difference.
I reset the full flying elevator to correct neutral. That (1/16) inch off (about one and a half millimeters) as measured at the leading edge of the full flying stab is likely why the original owner gave up on this Panda although that casting lip at the wings leading edge made it worse too. It is now up for sale or trade.
A Multiplex Panda
A True ARF Easy to Carry Ok to Fly
No Longer In Production
I could add more rudder and elevator (half an hour, nominal cost), even add in ailerons (two to three hours, thirty to forty bucks, plus forty grams) and more power (an hour or two, fifty to a couple of hundred bucks). But I won’t. They had a near identical RC airplane with from the factory ailerons (also discontinued, although a local store in Rhein-Main has a new one in stock) I won’t be looking for one at any price. Multiplex insisted if it had their name on it that the quality would be up to their high standards, there can’t have been any profit for them with the Panda at what they sold for. Kind of like the Edsel, the Panda didn’t fit a need for when it came out. Unlike the Edsel though (the Edsel may have set the all time record for poor build quality of American cars) the Panda quality was consistently rather better than comparable ARFs. You get what you pay for! Continue reading
Anybody with a bomber model eventually gets around to experimenting with dropping models of bombs from airplanes. These are usually solid foam pieces, or break-apart plastic shells filled with chalk.
If you want to try one out, and don’t have a 3D printer, contact me and I can give you one of these prototypes, as long as you promise to drop it from a plane and take a video. I have only dropped them by hand so far, and I wonder they behave when hitting the ground at much higher speeds. I also have some 3D printed mounts for the Eflite release that could be glued to any of these.
Here are two youtube videos showing tests:
Here is a link to the .stl files on Thingiverse:
After getting the rear end or the MQ-9 project sorted out, it was time to work on the front end.
The most prominent feature is the IR/EO ball. This is the acronym for the Infrared/electromagnetic Optical sensor array. There is a whole lot more going on here and you will have to look up the Raytheon site to get more information because there is a LOT of information about this sensor suite! Please note the size of the front “ball” on the full scale aircraft”.
In the next picture you can see that the Chinese model makers did not have the complete engineering drawings at the time of manufacture and as such, the proportions are a little bit off. I am only guessing that they might have been preoccupied with procuring model 35 information during this time period.
By Robert Stinson
On April 13th, there was a small airshow at Gillespie Field. Our field was supposed to be closed that day, so I went there instead. What luck! One of the planes on display was a 7/8th Scale Fiesler Storch, and I spent nearly an hour talking with the pilot and owner Steve Lund.
Those of us who have flown models of the Storch know that it isn’t the most forgiving of airplanes. Steve confirmed that our models exhibit authentic behaviors, and that they require a lot of attention. I thought I’d share some of his observations.
Due to its slow airspeed and zero dihedral, the Storch’s ailerons are not very effective. The pilot has to work the rudder constantly to stay on course. Flying from his home base in Torrance, he was berated by Air Traffic Control because he couldn’t maintain a constant heading!
I asked why the Storch had such relatively small wheels, since so many STOL planes use tundra style tires. Apart from the aesthetics, he said that landing speeds were so slow that they weren’t necessary, and would create substantial unwanted drag.
On one occasion though, the landing speed issue caused some damage to the plane. His plane originally had a skid on the tail. He was landing on a dirt field, and approach speed was about 30 mph. At that speed, there is so little airflow over the control surfaces, in his words, “you were just a passenger”. Once he touched down, without a tail wheel ground steering could only be accomplished by using the wheel brakes individually. He stepped on the right brake, the wheel dug in, and he veered right and hit a telephone pole alongside the runway, bending a landing gear strut. Fortunately, the field operator knew of a nearby machine shop. They removed the strut, straightened it out and were back in business in two hours. He now has a tail wheel instead of a skid.
Steve has spent many years making the plane as authentic as possible. He had 7/8th scale instruments custom made so that his panel matched the plane scale. The real plane had a map compartment under the panel. He made a fake map cover that masks his modern avionics.
The birdcage cockpit canopy is oversized, to meet the requirements for a reconnaissance aircraft. Sitting under glass, the pilot gets very hot! Steve fashioned prototypical accordioning roof and side shades and uses them all the time.
Great pains were taken to make the paint scheme authentic. For instance, the green “Z” on the fuselage denotes a headquarters squadron, and the yellow wing tips are Eastern Front theatre markings.
There was a lot more, that I won’t go into here. If you’re interested, search YouTube for Steve Lund FI-156. He posted a lecture covering much of this there.
So, for those of you who have struggled to fly an R/C Storch, just know that you are in good company flying a piece of history!
By Bob Kreutzer
The fitting of the empennage.
After fitting the motor, the empennage needed to be installed. As the factory was advocating just gluing the empennage onto the airframe and I realized that that would not work if I ever wanted to remove that nicely tucked-in motor I would need to make the stabilizers removable. This was easy enough with some hitch-pins and some more graphite rods.
Note the little copper L-pins I used for set-up. These were replaced with the proper sized hitch-pins.
Note also, the tight linkage set-up. This factory set-up was a disaster and the controls clashed with each other at full deflection. Yikes! What you cannot see is the severely misaligned dihedral of the stabilizers .The dihedral was off by almost 1 inch” I guess the poor Chinese worker was distracted on that day. I don’t think this is going to fly straight.
It took a little minor surgery to correct this.
Next up: the elevator linkages.
Oh, wait. The supplied elevator ball link is split!
Imagine that, the rudder link is split too . These early production run models had a history of falling out of the sky. I bought all new hardware.
Here is the factory set up with new hardware. This is when I found out the elevator was going to crash into the rudder on full up and full left. I had to cut off the rudder and cut down the wire and re-bend about an inch lower and re-install it. That took care of it.
This is the final flight worthy result. It is a bit busy in the back. Here you can see the final hitch pins that allow the elevators to be removed for motor servicing.
Here is the final result. It is starting to look like a real MQ-9!
By Bob Kreutzer
I mounted the motor finally!
I did it the hard way so if you want to do it your way it might be best. I did get the motor and spinner mounted well enough as an assembly so the result is flyable.
I used a 3d printed spinner thanks to ‘donandthereasa’ at rcgroups. Thanks! It took some work to get it to run true but it’s worth it. The spun aluminum finish took me 3 times to even get it to this point. (still needs another try)
The tricky part was making the motor spacer. Some nice person reported that this plane needed some right thrust. (imagine that…) So I put a tapered aluminum spacer plate between the fiberglass mount and the spinner. Matching up the thrust offset of the aluminum spacer and the motor spacer took a lot of time to get it right. The M3 x 16 screws are hard to get.
A different view. Note the long M3 x 16 mounting screws.
Pretty “tucked-in” mounting on this little motor!
If I recall I used a Cobra 3520 from Lucien at Innov8tiveDesigns.com. Nice quality motor in my opinion. That nice motor is mounted on the EXACT opposite of the nose of the aircraft. So, the weight of the battery must be accounted for in the weight-and-balance sheet. I found a 4S 2200 MaH battery to balance about right. Light motor, light battery.
The lead-in picture is the back side of a motor mount stand used for servicing. It was bizarre enough that I found it interesting. (but that’s me…)
And another warning, this project failed utterly. The foam was just too old, too much of the rest was damaged beyond recovery or so cheap it should not have been used in the first place. I’ve had a hundred foam airplanes, the tail surfaces warped like nothing before. I grafted the tail of a Fun Cub on, it wasn’t worth the effort.
Warped Tail from Behind
11 May 2017 (We.) I’ve lost track of how many times I’ve done fiberglass on this airframe, in about the ninth and tenth time the upper ailerons were fixed in position and some more minor dents spachteled and sealed.
It might have been warped up the whole time, on application of fiberglass hardening of the horizontal stabilizer it was evident the right side was up. It’s starting to feel like too much fiddling with this airframe.
02 May 2017 (Tu.) It was time to do it. Although not run up with them, two high discharge 3S 850 mAh LiPos were ganged together. I’ve forgotten the balance point.
Flight 1/20 Hidden Valley Flying field 02 May 2017 (Tu.)
It may be tail heavy and it pulls up too much on application of power. The top wing flutters at some speeds and attitudes. So bad that the upper wing went blurry. The left aileron was not secured, the corrosion made the nut feel tight, it wasn’t. The flight was stopped way early.
30 April 2017 (So.) The airframe is now built out to an RC airplane. All that is left is to fit batteries and go fly.
The white plastic motor mount it came with was not going to function by just redoing the back side with fiberglass. The hack job done by the previous owner and the small bolt circle for the three screw mount transmission were just too on the not enough. So, a plywood plug was fitted (to be drilled out later) and another bigger plug, a single layer of fiberglass in between, two over the top, were done. Sanded even, not much fiberglasss left on the front, but it should have enough strength to secure the transmission(s).
Well, after fooling with it some, it wasn’t worth doing. Just too much clearancing for the folding propeller. I’d be better off just making a new mount out of aluminum.
After reviewing the situation, all of my RC fleet is over old, the foam tired, it’s time to start over with fresh airframes. There is only one thing holding me back, money, or rather, the lack of. As it turns out one of the last places to get Multiplex stuff anymore is the best venue anyway, Discount Hobbies in San Diego CA. In the “musical chairs” of finding a summer project I wound up in Rialto CA, so, the hobby shop in Corona (Hobby City) is the venue of choice. They can’t remember who to order a Twin Star II or Fun Cub from. So, I bought parts to build out an Horizon Hobbies Apprentice at Hobby City (Corona CA) and since the only easy source for a Multiplex kits is at Discount Hobbies (San Diego CA).
About the Multiplex Gemini
This will be my third personal Gemini and the fifth I have reinforced. Now obsolete (no longer in production) they are great sport biplanes as in semi-scale, and semi-aerobatic. Actually, it is about as aerobatic as the airplanes it is a model of.
Between a friend, and, in Germany’s Rhein-Main with a couple of dozen RC airplanes at our disposal, when we just want to go over to our flying place (a farm field with all-weather access roads) to relax and play with RC airplanes the Gemini is THE favorite with the Twin Star II in brushless for use on days with a little more wind or mud. For the Gemini it takes reinforcing the nose, for the third and fourth ones we deleted the landing gear, modify the nose (clearance and fiberglass reinforcement) for folding propellers and reinforcing the wings. We liked them so much that dismayed when our first onew wore out (two hundred and one hundred and sixty flights respectively) we found new, old stock kits. Furthermore, they fit in my camper. A close alternative, and still available, is a Reinforced Fun Cub, also covered in an archived SDFSD article.
This is an original year 2017 article for the Silent Electric Flyers of San Diego. In the SEFSD archives is a previous article about building up a Reinforced-Gemini from new kits and the experience of twenty different propulsion combinations.
This new article goes over the common mistakes made by a first owner and trying out a couple of new propulsion components including two that should be the “ultimate” choices. That correcting mistakes, and the advantages of correct propulsion, are what transform my notes to a general interest article.
Included is adding enough fiberglass and redrilling from the original four hole to three holes of the first series of plastic motor mount to mount a modern NeuMotors 1105 series with a 4.4:1 transmission. It will be to be run at about half of the available (600) watts-in and an (80) gram sport Hacker to be run at the limit of (300) watts-in. In particular, having once modified a motor mount for the NeuMotors transmission (the modern style with three mounting screws) the same combination can be used in a Multiplex Fun Cub or Multiplex Mentor or Fun Cub, by just undoing a couple of screws and moving it over. That, and not the airframe, proved to be the most valuable to me portion of the original purchase. Or so I though…
Think This Is Expensive, Try Full Size
Rusted Out (new reciprocating) Motor(s)
While we are at it lets laugh, and cry, about an 60s era Aero-Commander (a sort of full scale Twin Star II, what the author flew by RC while building back up a Gemini) derelict, on Corona CA Airport. Somebody fitted it with new engines over twenty years ago as the start of a general build back up, however, the owner fell out, the motors remained open while the airframe sat for twenty years (which ruined them) the interior and propellers lay about in a garage, until the $1500- it is worth as scrap pales in comparison to the mechanics lien, unpaid tie down and back taxes.
And seeing the remains of a Piper Apache, another just after WWII general aviation twin, the type of which the propulsion (engine, propeller and all the stuff attached to them under the cowl) had been retrofitted to my father and I’s last airplane, a 1956 Piper Pacer PA-20, started out in. My father bought one like it new, his second one was older than I am. As preparation for ours, I helped overhaul two other ones, at which the conclusion was, ours wasn’t worth it. Full size or RC there is a place on the curve where writing it off is the best option. For our Piper Pacer (the basic engine was in ok shape, the propeller already recently overhauled) replacing the, some of them obsolete, entire instruments alone would run an estimated two hundred hours and fifteen thousand dollars plus recovering it and… The twin Apache with it’s retractable landing gear wasn’t just two motors more complicated, more like four times, no wonder it’s remains sit at the Oakdale CA airport.
That puts the thirty hours of sanding, fiberglass and writing this up plus a couple of hundred dollars outlay for an expected sixty RC flights (at twenty minutes to half an hour a flight) in perspective.
In Search Of a General Purpose RC Airplane Which Fits In My Camper
Maybe a good direction for me, looking for something which could be transported in my camper and used wherever I happened to be, would have been Multiplex Park Master Pro. Available complete ready to fly (less battery and receiver plus the usual RC stuff) over the counter for $230- plus tax at Discount Hobbies in San Diego Ca and needing only a couple of batteries in addition to the stuff I already have. That would put the investment at about $275-. But the friend with one wasn’t that enthused about his, what we flew most were Twin Star IIs and the out of production Gemini.
But, the Park Master Pro is for not more than walking speed winds and I like to fly in the wind. A former slope soarer, to me the wind is a fascinating ally and opponent both. Thermals, yawn, even if I recently put a Multiplex Reinforced-Merlin out in Hidden Valley way over the Mission Bay altitude limit riding one on up to the limit of my eyesight. As a club safety officer once put it; “Please tell me that dot up there isn’t your airplane and quit laying on your back to fly”. I have since reformed myself, but out where there is room (way outside San Diego) have an occasional relapse. My stuff must be able to withstand rough field landings, with it’s almost zero forward landing speed and long landing gear a Park Master (Pro) will. With other airframes rough field landings usually require folding propellers and some reinforcement.
But the worst about a Park Master Pro was not having three hundred dollars for a new toy.
I priced out refitting my beat up, bought last year for the new motor and computer radio it contained (full size) Apprentice. That figured in at around $110- for replacing all the airframe parts. The new motor (with an epoxy stirrer for a propeller) and a radio and receiver I wanted were the real deal. The three dead 3S LiPos went in proper disposal. The airframe was beat up and patched as I bought it, in a moderate dive the tail went into flutter, the wing should not be further repaired. In short with the exception of the new cowl the airframe was done, I didn’t trust the (possibly) beat up servos and motor controller either.
Now with more experience on others Apprentices I consider them an excellent choice for out of the box trainers. A careful balance between decent quality, average time between crashes and durability. Who, other than the author, expects over a hundred flights out of such an RC airplane anyway?
Except that the Apprentice as it comes with the motor mounted to the fuselage firewall with a canopy, if you hit the nose, you break it. And only a specific motor with extension fits. What’s the fun in that, if you don’t have a runway? I had a pile of motors, correct for the Apprentice size, I wanted to try, which won’t fit. I wanted a front mounted motor (gone out of fashion) so I could play with different combinations. I find the search for optimum interesting. For the Apprentice I’d have had to designing and build a whole new nose. Easy enough in a shop, but not in a camper.
That getting things really right, along with basic quality and good flying skills are why I am considered a bad example. The club members out in Corona CA were slightly dismayed at what I could do with their worn out Apprentice, using new batteries, propeller, a motor controller set up outrunner correct and my flying skills. “If I knew it still flew that well I wouldn’t have sold it”. As in half an hour flights including a dozen touch and goes plus inverted. Blast off the runway, do a roll, half split then glide for a while. I had to keep the speed in a dive down though as the damaged and repaired tail went into flutter and it won’t due to tempt fate with worn out equipment too many times. When it comes to fixed wing they just haven’t gotten a grip on substituting electric power for fuel out there, as is the case for many clubs. The form fitting batteries it came with were shot, so I built up some packs out of “get these out of here” low C discharge (5,000) mAh cells I’d been given and cut up the belly to make them fit. Run at (17) amps on 3S 3200 mAh (that original capacity is down a bit as they age a few percent a year) and use of the amps stick flights are in the half an hour range, even with the beat up wing. They also made for worthwhile performance in a Fun Cub and Twin Star II.
But at (400) grams those battery packs are too heavy for a Gemini. In case you were wondering; My airplanes are infamous for looking like expletive deleted and flying very well.
I’d have overhauled my SoCal Apprentice (they are also very popular in Rhein-Main) except the last day before returning from Rhein-Main I found a complete, unbuilt, Multiplex Mentor kit (same motor mount as the Gemini and Fun Cub) for use testing motors. So, I left most of my prospective medium power stuff back in Germany.
And I needed a modern production motor controller suitable for outrunners in that the timing can be set.
Half of my pile of average (150) gram motors are geared inliners, the other half outrunners.
In case you were wondering, in year 2017 with Multiplex stuff disappearing from the USA Market, The Apprentice is the best available trainer for roomy airfields such as the Silent Electric Flyers of San Diego at Mission Bay, San Diego CA.
The Merlin didn’t Do It
A friend had two of them, the second built, but unused. His first was in the learning to fly and try everything phase. He reported the Merlin as too fast and too small for him. The Multiplex Merlin, no longer in production, was an in-between, smaller and with ailerons more agile than the rudder and elevator Twin Star I with it’s “can” motor barely enough for flight, the Merlin as introduced was at the leading edge of the brushless motor plus LiPo batteries, it later lost out when the Easy Star II with its brushless motor (and a lot less howl changing from six inch to eight inch pusher propeller) and ailerons became available. The Merlin is small for outside, it is fidgety in flight, neither fast nor really acrobatic and easily damaged. As received (flown as the 3S tuning version) the elevator throw was just right (factory preset) the rudder fine, but the ailerons a little too quick. Flights were in the ten to twenty-five minute range. Which might seem reasonable, but they somehow the Merlin didn’t connect with me. I’m not as pleased with mine as the people who wrote them up back when they first came out around 2008.
In truth if you know what you are doing, or even more so, if you don’t, an up motored Easy Star II is a better choice than the Merlin. Part of that was that neither airframe is acrobatic, but it would take a computer radio to deploy the ailerons as either flaps or spoilers to make the Merlin land as well as the Easy Star II. Since they both take the same servos and receiver, the bigger diameter propeller of the Easy Star II cuts the pusher prop howl back to acceptable, and the difference in the price of the batteries makes little difference, for which you get longer, relaxing flights with no concern about scratching up the rear mounted folding propeller or dinging up the wing on landings…
After twenty five flights I put the Merlin on the shelf. Un-reinforced it needed a golf course to land on. Mine had some light fiberglass “hardening”. Hidden Valley with a wind out of the east, the grass still long, was ideal for that airframe, and yet other modern airframes did everything better, the small size was a disadvantage.
A Third Gemini
I haven’t been carrying as much back and forth between Rhein-Main (West Germany) and SoCal as previous years. Still, with me, was a new, great little (35) mm Hacker outrunner in the (80) gram size which swings a 9X6 folding propeller on 3S Lipos. Two of them would make a “killer” Radial Motored Twin Star II (and great for a light winds Fun Cub) but I’m bored with the Twin Star II (and bored with the Fun Cub) plus they take up too much space in my camper.
For the Gemini we liked the (105) gram motor size, run at well under maximum input, best for Geminis although I flew ours with motors from (40) grams through (135) grams on 3S and 4S. Somewhere out around (400) watts-in and you are forcing a low to medium speed (by the standards of outside) faster than is fun at the cost of weight taking the fine handling away. Gemini’s (set up right) fly fine in still air, yet they will buck some wind, up to two or three times walking speed (as much as San Diego’s Mission Bay ever gets) too. My personal Modified Gemini(s) stay up for twenty minutes or more per flight. The expected life of a Multiplex Gemini, if I build it new from the kit and reinforced it before it takes a beating, is one hundred to two hundred flights by which time the flight loads will have fatigued the wing foam to replacement. Flown gentle way longer. Cost new (no longer in production) fully fitted out, four hundred to six hundred dollars plus batteries and the usual RC stuff.
My total budget for the next airplane was in the hundred dollar new outlay (use what I had as much as possible) range. And, if possible, fit it with an economical motor and sell it afterwards.
In case you were wondering; I’ve had over twenty propulsion combinations in various Multiplex Geminis. Probably the best is propellers (all four I assembled were fitted with either Aero-Naut or Graupner folding propellers) in the nine to ten inch range, 3S 2200 mAh LiPos and motors in the (35) mm diameter size weighing between (80) and (105) grams. I tried (40) to (60) gram motors in the (28) to (30) mm diameter, brands Hacker and Scorpion, on small 4S LiPos with fixed propellers. The currently available common little outrunners are rated at 2S and 3S, all 4S did was wear them out too quick. Bigger motors put out more power than the (250) watts-out that seems to be optimum, left too little room for the battery and usually were nose heavy. The original (80) gram motor is average efficiency, also with its equal diameter to length a little short on torque. The Hacker puts out more watts-out for the same watts-in and with it’s larger diameter swings a bigger prop better.
Found a Gemini Core To Overhaul
The drive over to the Lakeside for the swap meet on an oddly gray morning, 18 March 2017 (Sa.) was an easy twenty-five miles over mostly freeway. When I first arrived in San Diego County this section was kind of like being in the country, not any more. On arrival it turned magnificently sunny. The field is located in a valley between steep rocky hills, currently green like not in decades and even wild flowers!
Not a lot for sale, and not many buyers either, but a very nice place in a steep valley to fly RC. I decided on a (likely ten to twelve year) old Multiplex Gemini fitted out with a, current to then, sport electric motor and good servos. The main landing gear had been rereinforced, it was painted a simple yellow above and black below with sprayed on paint, nominal scrapes and dings. That included a short range Spektrum receiver of the period, a motor and speed control. Per the owner bind it to your Spektrum receiver, put a battery in it and go fly.
After which I hung out for a while, took a bike ride (first time in that area since year 2006) and watched just a few people fly on a great flying morning. Actually, if they weren’t so fragile (by today’s standards) that 90s era Ugly Stick refurbished by an 70s era pilot (his likey birth date too) did well. Until on a typically hot landing (required by the high wing loading, semisimetrical wing and no wind) the nose wheel snapped off.
That is a great asphalt runway they have, and our Silent Electric Fliers of San Diego Mission Bay hard packed sand is good too. But I needed something for everywhere.
First visual check
In general minimal wear and tear.
The front landing gear mount is gone (a chronic weak part, just not big enough to get a grip on the foam) replaced with a plywood and a decently brace to the always too weak main landing gear. Kind of small wheels though. Just glueing on a plywood mount for the landing gear, the same size as what tore out, isn’t a sufficient solution. That rear wheel was never strong enough either.
Fuselage servos are HiTek HS-65s, more expensive, stronger and most important, better responding than the same size case of HiTek HS-55s.
I can’t see the identification plate for the wing servos. However, one of them the servo arm with the ailerons centered is at right angles to the wing, the other back about (25)% degrees! Both wings needed more aileron up then down (positive differential) one was about equal each way, the other negative differential! It never flew as well as it could.
That motor was likely sold by the now gone for a decade Sureflite hobby store on Convoy, they were ok motors for back then.
It has an older Castle Creations Phoenix motor controller rated at (45) amps on 3S LiPos with the BEC and 4S LiPos without it. Deans type connectors. That sounds fine, except to my knowledge there was no way to advance the timing from the (5) degrees for inline motors to the (20) degrees a typical outrunner needs. The outrunner still turns, but used power inefficiently. As in shorter flights at less thrust then they could if the motor controller just fed the pulses correct for their type.
The rear wheel assembly is intact, but the thin wire loose in the mount. I doubt it was ever glued in place.
The whole airplane had been spray painted a high intensity yellow, then the bottom of the wing was spray painted black over the yellow, including some yellow overspray on the APC 8X6 propeller. I used to slope soar, I learned the hard way don’t make the underside of an RC airplane the same blue as the sky. From experience somehow the Gemini is hard to see at a distance.
Some scrapes on the lower wing tips, a leading edge ding and some abrasion, otherwise it appears to be straight.
The motor mount has had the four adjustment screws removed, it is held flat to the motor mounts. That made for too much up thrust. A weak point of the original, the four adjustment screws gouged into the side rail mounting plates until there was no adjustment although there is no indication the screws were ever used on this airframe. It has the original white plastic motor mount, which are prone to warping, modern production is aluminum.
I had carbon fiber motor plates of this type, but they (along with a motor plus propeller plus motor controller) went missing after a flying session in the vineyards of Rhein-Main. I can’t clearly remember, but that would explain the case of local wine and the empty bottles on the floor of my camper one morning.
Three of my geared motors, now a decade old (two from Multiplex, another an old stock NeuMotor) the transmission used four bolts, my one modern production NeuMotor’s gear box uses three mounting bolts. For which there is no “standard” Multiplex motor mounting plate. With four they bolt straight to the white plastic motor mount as do smaller motors. But, they always warp. Sanding and fiberglass take a couple of hours to correct that. A couple of hours as that plastic is surprisingly tough, and after thinning it out it needs some additional reinforcement. Still better, if you have several airframes that take the same mount, then whittling one out of plywood, which still needs fiberglass to hold up in service. You can’t get carbon fiber ones anymore.
The nose has been cut flat with the motor mount. As good a way as any to easily repair the damage from a nose over.
Disassemble and Sand
As so often, be it a new kit or a used airplane, it was taken apart (the wing came off easily, just unscrew the two screws) and then sanded. About an hour and a half, which used up one of three sanding blocks. Just going over things deciding what did I have and how much was left.
The Gemini kit comes with sharply pointed wing leading edges. Too sharp for the intended speeds. The reason is to get them out of the moulds with a minimal casting flange. That is a chronic problem, casting flanges at the wing leading edge, with foam ARFs! And I can’t convince the owners to take five minutes with a block of sandpaper to make them right. These wings had taken nominal use, the leading edges were a little worn (plus a dent and a tear) so, I sanded until they were an even, if blunter, round. The dent was patched with lightweight spachtel and a layer of thinnest fiberglass. A critical issue as if the wings were not really usable, with no replacements available, I could just strip the hard parts and junk the airframe.
The aileron control horns are from then production, the attachments to the “barrel” connectors are loose in the holes! Well, it no doubt flew, but with that slop, it flew uneven.
The Motor is a Dualsky XM3548CA 1080/rpm/V weight 165 grams. That information from the tag on the motor. On research in the Internet they are still available although, current production is listed as 1000/rmp/V so they might have made some changes. From Dualsky the best efficiency is at (14) amps, the maximum amps (fifteen seconds) is (24) The maximum power is (250) watts. I take that that is (250) watts-in at whatever efficiency. To keep that in perspective that is one third of a horsepower. If it weren’t for the excessive weight and length that would actually be ok for a few flights. Ho hum flights that would make you wonder why you bothered, except nobody else’s did any better. Well, if they all keep making the same cheap choices…
The motor was run up with a 3S 5200 mAh LiPo, old stock that hung around too long. That battery is good for hour and a half long flights (you read that right, (1.5) hours) in a Twin Star II with cheap motors. So, the voltage under load seems a little low.
With the as purchased (used) Phenix (old stock, circa ten years) (45) amp controller
10.4 Volts under full load It that seems kind of low, that’s what happens when a LiPo sits on the shelf too long.
22 Amps In case you were wondering that is the same load as two smaller motors when used in a Twin Star II.
230 watts-in A guess at watts-out, two thirds of that or about (150) watts to the propeller. At that weight of motor it would have only flow on, and landed fast. The previous pilots likely wound up flying way nose heavy too.
Next up was an out of box traded for (35) amp motor controller
156 Watts-in WtExpletive Deleted That friends and readers is why you use a power meter and check things. Something was wrong, might be the motor controller or it’s settings.
Then a latest series (new) Castle Creations (25) amp Talon motor controller with no changes to timing or brake. Later the brake was set, there are no timing adjustments other than the frequency.
So, the motor was being operated at maximum input. Except we want that power to turn the propeller, not heat up the already going shot bearings of the Daulsky motor in addition to eddy losses of the inexpensive materials and ineffective transfer of inexpensived watered down magnets. The assembly (motor, motor mount, propeller collet) was disassembled. Somebody did an ok job of drilling out a motor mount intended for the original bolt circle for a bigger one. I’ll likely unsolder the connectors and throw the motor away. From the gouges pliers were used on the propeller collet, that goes in the garbage, too. After sanding it approximately flat (the white plastic always war
Norbert, his wife Susanne and good friend Egon are here in San Diego to fly his one-of-a-kind giant scale RC V-22B Osprey at the Miramar Airshow. Norbert designed and built the Osprey from scratch at home in Austria. I had the pleasure of meeting them and witnessed their pre-airshow flight test at Alpine Aerosquadron’s field on Thursday before the airshow. Click the pic and you can see pictures and a video of the Osprey. If you can make it to the airshow, please go visit them in the model airplane tent near the flight line. Like most modelers, they are some of the nicest people you will ever meet. – Steve
Norbert’s website: http://www.avens.at/cms/index.php/en/
Another great video and pictures here.
Some interesting facts below:
|Original V-22||Model data|
|2 Rolls-Royce AE1107C||4.586 kW||Length||2,05m 6,72 feet 80,7inch|
|Length||17,48m / 57,3feet||Width||9,84 feet / 118,1 inch|
|Width incl. rotors||25,78m / 84,5feet||Rotor diameter||14,52 feet / 54,3 inch|
|Rotor-diameter||11,60m / 38feet||Weight inc. batteries||about 48,5 pound|
|Max. height (nacelles vertical)||6,73m / 22feet||Motor||Kontronik Pyro 1000-40|
|Max. starting weight||23.859 kg / 52.600pound||ESC||Kontronik KOSMIK 200 HV|
|Max. travel speed||500km/h / 300 kts||Batteries||12s 4x5100mAh (2p) LIPO|
|Range||790 km / 428mn||External tiltelectronic||Benedini|
|Max. hovering time (Loiter time)||20 min||Flight controller||Flip32 Board|
|Payload||24 men or weight up to 20.000 pound||Remote control||Jeti DC-16|
|Maiden flight||March 19.1989, deployed 8.12.2005||Scale ratio||1:8,5|