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

The Solius and Heron pt. 2 of 3



A Part 2 conclusion; Unless you already have all the required components sitting around paid for already, is buy a Radio Ready (RR) Solius or Heron, sell the motor and maybe the propeller combination too, do some light reinforcement before hitting the first twig, put in a more effective propulsion combination and go fly. Carefree flying either using the motor to play with, or climb out to hunt thermals, or for slope soaring days when the wind isn’t reliable enough. All of which requires a decent landing place though. Impacts that wouldn’t even dent a Easy Star II or Panda can result in writing off a Solius or Heron airframe. If you can’t yet reliably land you aren’t ready for these two.


Although hardening the wings leading edges (use the decals if nothing else) and the belly is always a benefit, there isn’t much to be done about the whole front bending up on an impact, or the wings at the root kinking when it spins on landing, or the wing shearing off the whole top of the fuselage. As in neither prior additional structural reinforcement nor repairs is going to make much difference. There just isn’t enough room to add much strength, a consequence of the thin dimensions required for thermal efficient airframes.


Just the same, Multiplex airframes go together better, fly better and last a whole lot longer than similar products as slightly less initial expense. Multiplex products have lowest net cost per flight and high satisfaction ratios. We are into a new era in RC flight, buy a Solius or Heron, enjoy them, and when they are damaged, repeat. My decades of repairing and the reinforcement expertise from that despite, for the physics of these seven foot wing span motor-thermalers isn’t much of an advantage. Most of the improvements over the RR for the Solius and Heron were confined to the motor and propeller selection.


Radio Ready or improved, you may expect under ten bucks a flight for the airframe and power plus the consumable parts of propeller blades and batteries over a fifty to hundred flights out of a Solius (simple transmitter) or Heron (seven channel computer transmitter). When you get done pry the servos out for reuse as they may be expected to outlast the foam. If the final crash didn’t damage the Original Equipment from the Manufacturer (OEM) motor-controller it, as the motor and propeller assembly, can be reapplied too.


Since after selection of the servos (get basic quality as in HiTek or Multiplex) there isn’t much to changing the airframe other than some hardening, most of the discussion will center on selecting propulsion. That takes up quite a bit of text, it’s the answers to questions that so often come up at the flying field(s). Which, even if you can’t directly follow it, leads to specific Solius and Heron suitable combinations. Even better, what powers a Solius or Heron can be used in other airframes, such as a Fun Cub.


Better and for Twice as Long

As for why change an effective OEM combination: My Mini Mag had four hundred flights on it when a new club member at Mission Bay commented that it looked like expletative deleted, flew like on rails and seemed to stay up there way longer then he thought possible. Two former club presidents didn’t even look up to identify me as the owner and pilot. Away from Mission Bay I’ve pulled the same with Fun Cubs, as in taking off straight up on the motor and slope soaring in gusting twenty five mile an hour winds for most of an hour to land at my feet no preparations for the next flight other then charging the 4S LiPo battery required. Our first pair of Geminis made a cumulative four hundred flight with every single landing what we previously would have described as a crash. My Twin Star II can out fly your RR one, trade airplanes and transmitters and I can fly your Twin Star better then you can. I’ve had Multiplex people at fly for the fun of it meetings come over and take a good long look at my stuff as they couldn’t believe what they saw demonstrated. As in a Mini Mag which can take off straight up, slow to walking speed and stay up for three quarters of an hour on a single battery in still air using standard (not all that expensive either), components.


If you need an introduction to these airplanes read the reports by others and watch the videos. I’m not into aero-modeling, these Multiplex airfames are just fine they way they come out of the molds if you spend just a few hours on them finishing out what they couldn’t afford to do at the nominal purchase price. Ya still have to trim the casting flash! My airframes look just about like all of them, stealth wise there are some important changes.


Slight Reinforcement

I was able to make some improvements to the airframe of the Solius and Heron, simple improvements anybody could make in a few hours. The goal is that pair of seven foot wing span motor-thermal RC airplanes, included is fiddling with a whole slew of equipment as it fits in with the theme of selecting RC components, as a carefree experience in wow, that so much was available for so little, at a low(est) net cost per flight. For me that means taking a few hours more during initial assembly doing simplest improvements such as sanding the casting flanges off, hardening the wing’s leading edges and improving the motor mount. For San Diego California’s Mission Bay’s sand paper runway I leave the belly wheel in, for Rhein-Main’s in Germany sometimes soggy and always a little rough grass as a crop fields (mud, snow, water and manure) I take it out.


The biggest airframe improvement, which applies to all cast foam airframes (almost never mentioned in reports by others) is taking ten minutes with grit (320) sandpaper (or finer) to smooth the casting miss-match over the leading edges and take that lip at the trailing edges off. Over and over again I see airframes where the owner forgot that vital basics of aerodynamics. Be it done with heat shrunk on packing tape, thin fiberglass held with water based paint (or new for the Solius and Heron) the supplied decals, my leading edges are smooth.


I took about a fifteen hours assembling my first Solius from a kit (half that sanding and additional abrasion reinforcement) as I’m a fussy builder. I expect that becoming “one” with my Solius (perfect the center of gravity and control throws for standard, fast and landing, plus in general learn the reactions of the flight profile etc.) to take a dozen flights although the parallel RR Heron of a friend’s was cause for grins and satisfaction within minutes. Then I’ll begin fine tuning the propulsion. Part 3 will be the specifics.


Compared to a “stock” Solius my bare airframe weighs about (50) grams or two ounces more despite deleting the belly wheel assembly. I’ll get some of that back by using a lighter motor for reduced additional weight at the tail. The first time you knock a chunk out of the leading edge (or more likely abrasion eats away performance) or look at that accordion of the fuselage at the transition between the thin foam and hard plastic motor mount of yours my why(s) will become clear.


Creating a similar airframe from an old style kit, even using supplied cut parts from sticks, glues, iron on coverings and such would have taken about forty to sixty hours with additional repairs after most flying sessions, and have cost more cash. To make sure you understand that; A Solius or Heron airframe costs less and flies better then what we could build out of component wood, glue and covering ourselves, even if you had my building skills. If we hit the ground hard, with the Solius and Heron, it’s just money. The best of the new stuff all built in moulds nowadays.


A motivation for putting my notes down in a report format is that the adventure of really using what we can get is missing from a vast majority of what you can read as preparation for your own RC flight adventure. As in just getting the (first) motor to bolted in took an hour. The wires sticking out the side of the front of the motor make aligning the holes an exercise in patience and finding the right length of screws too.   Or getting the servo centers of the wing servos to really match. And getting the best real match, after all the fooling around on the virtual dyno and bench measurements, of the propeller at the two near sea level flight locations for our mostly not much wind flying conditions.


First, A History lesson, the Downside(s) of Balsa and Fiberglass


Let’s start with why, despite the “EPP was good, let’s move on” of the Harbor Soaring Society in the mid nineties, many of us now fly reinforced, impact absorbing form airframes. Twelve years ago in Rhein-Main, on close out, I bought a partly framed up six foot wingspan motor-thermal RC airplane from a German manufacturer (Robbe, after decades of supplying quality, as a company just left the field bankrupt, unlike Graupner who reorganized, Robber is gone forever) new as a semi-kit for seventy five bucks. That was less than half what the retail should have been as it was the end of era for that type of semi-ARF.


The model, if you will (this is a radio controlled airplane with no pretense of visually matching anything man carrying although they insist on putting a canopy on it) is now about two decades old. So old that the rudder and elevator, which today would have servos in the (18) gram class (twelve or even eight grams are sufficient), are actuated with “standard” servos in the (45) gram class. That molded plastic fuselage may seem hokey, and it’s heavy, but it was a great improvement over having to build (and constantly repair) your own. The aileron wings were balsa over foam sheeted (factory done) with final assembly into a wing to be performed by the owner, you had to assemble the tail out of sticks to cover and hinge the whole thing yourself. Building skills were still the rule in RC and we were glad to need less of them with this type. That pre-sheeting meant that somebody with below average building skills and not necessarily a place to sheet wings had an excellent chance of producing a good wing as did the self assembly of the fuselage.


Power, as supplied, was a direct drive Speed 550 brushed motor (2.3mm output shaft, about sixty watts-out at fifty percent efficiency for the twenty to fifty or so flights between the brushes wore in and wearing out, if the shaft didn’t bend first, figure about a pound of thrust for a seven pound airplane), it came with a suitable 6X3.5 folding propeller (3mm hinges) which would have just carried the assembly up on a suitable six or seven cell nickel-cadmium battery of the RC car size common to then. The purchaser to supply the electronics (back then a servo accuated mechanical on/off switch) to control the motor. Once in the air it would no doubt have flown fine although I was already tired of the limitations of flat bottom airfoils.


I’d flown a slope soarer Ninga glider a decade previously. Pondering purchase of the Ninja kit, I can still remember the hobiest behind the counter answer to my hesitation about foam core assemblies. He cut straight to: Build one foam core wing and you will never build one from sticks again. That was 1996, he was right. Any “conventional” airframes after that I since acquired as used or as ARFs and I haven’t had one since 1998. Although seemingly heavier, sheet over foam made up for it with a better airfoil, none of the thermal champions of then used stick and iron covering.


That Cox Grasshopper I flew at Mission Bay and around SoCal after the Ninja was light and so flew acceptably when the then available electric propulsion. However it required major repairs about every twenty four flights over two hundred and forty flights. Typical thrust duration was thrust for two or three minutes, the in the air time was five to twelve minutes. I could by then estimate the repair time required by the sound of the impact. My last motor-thermaler, factory built up out of sticks as in “conventional” by standards of then, I’d got the hang of it, gearing the brushed can motor marked for RC cars made for a vast improvement in motor durability, it went three hundred and fifty flights with no major repairs before I gave it to a friend who laughed so hard chasing a buzzard that he hit a tree twenty foot up on his first and only flight with it. It hit so hard he couldn’t find the motor/gearbox/propeller. They were found hanging in the branches, with the electronic on/off switch a year later. The motor and gearbox were still usable!


I’d switched to packing crate foam with internal spars flying wings (I had the first one in the SEFSD at Mission Bay, a Razor from Zaggi) and the Multiplex Easy Star about three years before. It was about when brushless motors were just available (over my affordable limit back then in the hall effect era at a week’s take home pay) and LiPos were up to (8)C capacity (not really enough) but what held me up completing the BIT after a dozen hours of building was a switch to a foam Twin Star II, an aversion to constantly bent motor shafts and the repairs of balsa, so I just didn’t get around to buying the flat servos for the wings or the conversion to modern propulsion. With the Twin Star II and Easy Star (1) I determined that thermals where I lived in Rhein-Main wasn’t what I was into, there was no place to slope soar anything and I rather enjoyed the freedom of landing on farm fields without incessant breakage instead of the confinement of a decent RC runway.


Compared with the twenty to forty five minutes of today on modern brushless and LiPos, flights were much shorter and a lot less trilling with brushed speed 400s and NiMh batteries. What a relief, I sometimes made a hundred flights (albeit back then not a third of today’s duration) with no repairs until around flight four hundred the basic material, despite some select reinforcement I added, of the foam gave out. Twenty years ago I was doing good to slope soar for three hours at a time with repairs required about second to fourth session. That Ninja wing had outlasted three fuselages when I gave it away repaired, despite hitting an oak tree after slope soaring at Point Loma in sight of the Los Angeles California harbor.


Keep in mind I flew a decent slope in Costa Mesa’s SoCal for a decade. Just a hundred yards back from the slope (now history, the trees in the park below ruined the lift) which is first rate for thermals (five past or present world thermal champions flew there then, at mid morning sometimes it seems the whole atmosphere is expanding as you can’t help but catch lift, plenty of room and runway) but just never did get into standing there on a flat plain delectably balancing on an invisible cone of rising air. And I’ve never had the least interest in thermals anywhere else in SoCal either. Oh if I’m chasing weak slope lift, I’ll use a thermal, but…


Bump the ground with a Robbe BIT and you have to repair it. Maybe at Torry Pines you could slope soar and land it without breakage being routine.  A couple of years later the Multiplex Easy Glider motor-thermaler came available. With its (then) geared speed 480 brushed can motor on (7) nickel-metal hydride cells, they just weren’t what I felt like. Despite being impact resisting foam the nose proved to be fragile, performance with the original propulsion was just barely acceptable. Despite modernization since then (plenty of power on 3S LiPos and durable too) the Easy Glider still has just one speed, variations on slow. The Easy Glider then and now the Easy Glider Pro is about useless for slope soaring and not much better for thermals with the same although different proportions applying to the Easy Star II. At least with the BIT if you put the nose down the speed picks up enough to reach the next thermal before having to use the motor again. You can land a modern Easy Glider on a farm field. Any flat bottom wing just can’t do much maneuvering. Eight years ago I finished out what was once the standard RC motor airplane with a flat bottom Clark Y airfoil. I started getting bored during the first flight, that delayed the BIT too.


A Gift from a Stranger

This year 2016 my wife discovered two similar motor sail airplanes of the same era from the same company as my five hours from completion motor-thermal, complete with everything but the battery, put out for the garbage. My motto is pick it up first and see if it is any good later, they looked like they might be worth freshening up and putting modern components in. Something to do on an otherwise, almost, but not quite, completely financially broke end of January year 2016 rainy, gray day.


The horizontal stabilizer is a chronic break location of rigid airframes as are the motor mount/nose and wing mount. The ARF of it’s era, on peeling back the tape holding the stabilizer in it, it was solid (soft) balsa with shrink on covering, which had been broken and glued back together at least twice. Well you have to start somewhere, the repair using clear paint (dries fast, use a hair dryer) and four layers in the middle tapering to a single at the ends of (2) ounce per square yard fiberglass (each side) took an hour. After which I started using fiberglass and two component resin to repair the nose.


Waiting the six hours for the estimated first of five times working over the nose for the epoxy to harden I started on the wing (six foot, two piece, this is a ruder and elevator flyer, no ailerons or spoilers) balsa over internal ribs and spar, it was beat up, the repairs weren’t all that well done. The pictures tell the story of why I haven’t fooled with balsa in years.


That speed (700) “can” brushed motor rated at (8.4) volt would likely have needed eight to ten NiCad cells to go with the 8X4.5 folding propeller. With it’s (3.0) mm output shaft and (3) mm hinges the decades old blades are useless, why bother with the rest. A modern combination weights a third as much and runs three times longer on a charge.


Times move on, this laptop I’m using to write this so out performs my old ones that even though they still functioned, they went the same way as my VCR, brushed dc flight motors, NiCad and Nimh motor batteries and any analoge FM frequency flight radio equipment. R.I.P. (aus dem Amerikanishem Rest in Peace, in Frieden ruhen) If I feel a need to visit the old stuff a couple of hours drive away on the east side of the German state of Hessen, where man carrying flight with gliders began, the Wasserkuppe has a nice RC flight museum. And it’s a fine place to fly RC too. Just have to watch the weather, one of his trips over there my friend went past a car sitting on it’s roof. Skidded on a thin layer of ice… In San Diego the Flight Museum at Balboa Park has a room in the basement where the SEFSD sometimes holds club meetings for the American version or RC flight.


I liked EPP starting with my first Carinosarus in 1995 and still do. I’ve taken a like to carefree RC flying. I put the two “gift” used motor-thermalers from a bygone era back where they were found. To consolidate the above dissertation, if you find a used airplane and want to fly, leave it there and get a new Solius or Heron. The cost per flight will be less no matter if you figure it in dollars per flight or hours expended.


Let’s Start a Solius Experience


Add to the Single Thickness

For stuff that was affordable, be it the molded fuselage of the BIT or balsa, it was difficult to add strength where needed without making them too heavy. Unlike layered stuff when they molded from plastic the thickness was nearly the same throughout. Fine for the tail, but week from the rear wing mount to the front motor. Building out of balsa we often doubled the sides up but that was about it. We used to hear the term “Build it to fly, not to crash” a lot back then. Even twenty years ago I added fiberglass to the tail where the horizontal stabilization and fuselage went to together and from the rear wing mount all the way to the front of the fuselage.


With foam the restriction is the thickness of the foam plus how much reinforcement they can insert and keep the price acceptable. With modern materials we can make some adjustments nowadays, take it from me, the nose of the Solius and Heron can use some help. I like what they molded in for a shape, layering over fiberglass is a cost effective means of adding select strength.


See the pictures for a twenty year old balsa/plastic ARF and the progression of propulsion. Something I’m stuck with in that old fuselage, its configured for motors with the wires stuck out back with no room for them exiting the case at the front and the configuration of attachment. A solution is lay enough layers of fiberglass over the front, use the thinnest even though it’s finicky to work with, and you can redo things with simple hand tools. As it turns out, that same applies to the Solius and Heron.


Matching the Airframe, Motor and Propeller

The next step up from brushed motors were “inline” brushless. Which need to turn up way higher than the requirements between the airframe and propeller. They are fine for speed racers, but for these “low geared” motor-thermalers we need a better match. That fifteen year old inline brushless with a 4.4:1 pales in terms of a lighter outrunner, but I had it and it fits in there. It’s (185) grams is limited to (350) watts-in, a modern sport class outrunner as from Hacker or Scorpion at (135) watts-in are rated to convert up to (600) watts-in at slightly less efficiency. Depending on windings all of them can swing a Solius or Heron suitable one foot diameter folding propeller, or not. Purchased new for this Solius project a (35) mm diameter Hacker in a “shallow” configuration, so it only weights (80) grams (verses “square at (135) grams and long at (200)) so it can swing a ten inch propeller on a 3S LiPo. Way more torque as the (28) mm diameter (60) gram motors on 4S as initial evaluations in a Multiplex Gemini and Acromaster demonstrated. As testing demonstrated, it takes a (135) gram outrunner with a kV of around (600) to swing the stock 12X6 folding propeller on 3S.


As part of my justification for spending more quality control comes up. Something which is a constant issue in manufacturing (with which fewer and fewer Americans involved with) that represents a major expense. The last dozen motors I’ve been alternating brands between Scorpion and Hacker. Hackers come with more of the bits and pieces such as really good propeller mounting hardware and screws with durable surface treatment, which partly justifies the higher price. More important though, quality control just hasn’t been an issue. I’ve stopped buying Scorpions. Although in proportion the seemingly one fifth higher (initial) purchase price wouldn’t be justified going off just the specifications, simple things, like both of my (60) gram Scorpions throwing their oddball (3.0) mm propeller (fixed) carriers (including loss of the attached propeller, overspeeding the motor and ending a flying session) was twice an issue and never with Hackers. Hacker always used wire which was not only flexible from the start (so you could easily mount the thing in confined space of a Solius or Heron nose), it stayed that way. I’ve had Scorpions where the indications are that one of the bearings was sitting at an angle, likely from the color plating just a little too thick. The difference is hidden in materials and quality control. Hacker’s advertisements start with “because quality flies better”, for them it’s not just a slogan. Even their seemingly expensive sport motor-controllers function better.


Want a laughing grimace from our Editor; Ask about his experience with suppliers substituting cheap stuff on him back when he produced kits. Buy a NeuMotors and it will function exactly as specified, that isn’t easy, or inexpensive.


We want to bolt up and not spend too much, all out would be a geared NeuMotors. Geared inline motors have an additional advantage in that the old fixed (5) degree timing motor-controllers is correct for them. To get the most out of an outrunner you must have more lead (determined by the motor-controller) as in twenty to twenty five degrees. Lately we’ve been leaving our motor-controllers set on automatic, going to try that on our geared inliners now too. There’s this issue of leverage, in this case when you hit the ground with the propeller spinner. OEM to the Solius and Heron is an folding propeller assembly for (5) mm shafts. Quality transmissions (NeuMotors or in Germany Reisenauer) installed on inline motors suitable for them have (6) mm output shafts and a smaller bolt circle for mounting  There is a standard question in every speed shop; Speed costs money, how fast do you want to go?


In the case of using a (6) mm output shaft on a small bolt circle I’m going to have to do some research and likely areo model the nose as Aero-Naut seemingly doesn’t have an assembly for the folding propeller assembly. An additional hidden benefit, those transmissions are more impact resistant than the motors.


Although several levels of watts-in/watts-out ratios higher then this inexpensive Solius, when you are already at the going for the win in world and national class contests, it appears that geared inline motors verses their equally tuned outrunners have a five percent more watts-out for five percent less weight advantages. Even at the F3A level, where that motor and controller run eight hundred dollars it’s not clear which is better.


And there’s an issue of duty cycle. Now although some airframes, such as the Twin Star II, you ought to stay within the manufacturers maximum continuous load, with motor-thermalers you can go ahead and use all the thirty second limit. A prospective combination is the NeuMotors 1105 and 1107 series. With their respective (200/400) watts-in and (300/600) watts-in ratings. The target is (80)% of maximum which works out to (320) watts-in and (480) watts-in. NeuMotors has two different virtual dynos on their web site. Use the simpler one for making estimates. And don’t forget, the program expects near standard conditions (i.e. Mission Bay) of shirt sleeve temperatures and near sea level air pressure.


Regardless of motor selected, in this we can easily get more power than ever before era, is rather than use the thirty second limit, is to select a combination being run at the motor’s best efficiency of typically (0.80) of maximum watts-in. With modern components if you aren’t in it to win that’s not much of a weight penalty, the percentage of the amount of power in the battery converted to moving the airplanes improves, the motors bearings last longer and if there’s any tendency to overheat that backs off a bit. Let’s be airplane designers here, start with the best match of propeller to airframe (the OEM 12X6) and stay near that. Work backwards from there to select the motor/voltage/transmission ratio from there. I’ll have weeded out the ridiculous combinations although, sometimes it’s fun to stick something in just to see if it functions.


And there is the issue of at higher voltages the whole system is more effective. Given the restriction of easily available sport equipment for this project 3S and 4S LiPos seem reasonable. We are dealing with burst and glide, there are outrunner killer inline motors and geared inline ones that way beat inexpensive outrunners, at a higher initial price.


Buy a Radio Ready (RR) Solius or Heron and the engineering/fiddling has been completed, but that OEM motor is on the low performance side.

And some of us just can’t leave well enough alone…


Different Expectations

For the Solius and Heron we are going to have to make some expectation changes

in regards to durability as we want the flight efficiency of long and thin, at the expense of being more fragile, plus the bigger flies better, but crashes harder aspects of their seven foot wingspans. These aren’t going to be bounce off of things, pick it up and keep flying typical of the stuff I reported on in the past.


If you can afford the transmitter required the Heron is the better still air flyer, with it’s slightly higher wing loading the Solius has an edge in the wind.  


Even before more than first flights I am not expecting the hundreds of flights of my three foot wingspan (Mini Mag, Easy Star, Twin Star II, Gemini usw.) stuff to date. More like fifty to a hundred flights. We even had to learn to carry these seven foot wingspan RC airplanes differently. But that’s for Part 3 after we have flown them enough.



There is considerable confusion that cheap, inexpensive and really good sport flying components are all the same brought on by a vast majority of published RC airplane reports only trying a single combination and then only for a brief duration without any impacts, wear or tear. Most of the time they list the price of the airframe, and nothing else. T