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

The Mini Mag Revisited Pt.1


The build up/economic analysis includes representative equipment ranging from just good enough,  through the best,  including mentioning stuff too cheap to trust.  It is expected that if you are contemplating a Mini Mag that you will be reading about them on the Internet,  this rounds it up,  way up.

This is Part one,  getting started and the wing with a basic discussion of power.  Part Two is the upgraded Power and Armor section,  making use of an Internet virtual-dyno will be detailed.

This is a private club article,  not a commercial publication subject to support by advertising.  While researching for building up other airplanes I realized that,  The Journey of flying Radio Control was missing from what I was reading.  This isn’t about just putting together a single,  do all better then ever airplane,  that could be specified on a single page.  It’s also about the search,  the choices and the experience.  Burned up equipment,  backtracking because things didn’t work as expected and crashes included,  life wouldn’t be complete without them,  or the people I flew with.

I enjoyed the company of every single person I ever flew with down at Mission Bay,  as part of this story about our journey together I included characters from the SEFSD,  and our in-club manufacturers and RC equipment dealers.  Part of my personal journey includes being lamed by brain damage from 1997 through 2000,  I was glad to find a group I could hang out with.  But,  if I misspelled anybody’s name,  assault the editor for not correcting it before publication.  At least he can walk over and ask you personally,  I won’t be back in town until February.

The Pilot is Still a Big Part of the Equation
As for why my seemingly ordinary looking Mini Mag should get so much attention;  It reminded  me of an exchange between Brian Buaas and Jerry Bridgeman “Just because you are the world champion doesn’t mean that right here,  right now,  with these airplanes,  that I can’t out fly you”.  Bridgeman was then the reigning F5B world champion and Team USA member to Steve Neu.  Wayne Walker from then is still a pylon racing team manager.  We were slope soaring the first EPP airplanes available in Costa Mesa,  CA,  year 1995,  when I heard that.  Buaas reminded Bridgeman that he had (17) years of RC competition.

I was just getting the hang of RC back then.  What a relief to get something more durable then balsa and iron on covering.  But today,  even if we were flying with identical equipment,  all three of them still would,  in a competition,  knock my socks off.  But,  when it comes to dancing a simple,  inexpensive,  durable airplane around in the wind,  around obstacles where only a fool would fly requiring precision landing skills,  we might come up nearly even.

One of my jokes is to fly a Mini Mag fitted with a (8to10) inch prop at head height in a twenty yard wide circle at just above walking speed (and if the motor quits right then below stall speed,  I can hang it on the prop in level flight) for few laps,  turn a few inverted,  then transition to vertical loops.  Of the requisite equation for flight,  Altitude,  Speed or Power,  that is the power portion.  After ten or twenty rounds I climb out to the legal maximum height,  straight up.  The joke is that an airplane based around a $78- foam airframe shouldn’t be able to do that!  The people who are really good at anything always make it look easy.  Right next to you with the SEFSD are a whole bunch of very proficient pilots and builders.  A Warning;  Just because we can fly that way,  doesn’t mean you should,  or can.

Fly a Mini Mag if all You Can Afford is One Good Airplane
When fitted out with a brushed motor and nickel batteries,  a Mini Mag is just a slow trainer.  With modern propulsion components Mini Mags can be the most versatile,  carefree airplane I have ever seen flown.  At just over a three feet wingspan and less then two pounds of weight,  it’s a comfortable size to transport in a car and go enjoying life.

Flying a Reinforced Mini Mag isn’t about competition precision,  it’s about the joy of an all purpose fly it anywhere airplane.  They are as close to care free as anything that ever took to the air with the motor in front is.  Although there are,  on the average,  better trainers,  Mini Mags,  because of their gentle,  predictable handling and,  important for middle aged learners,   scale sort of Cessna 185 looks,  can be good airplanes for beginners too.

No single part of the flight envelope of what a Mini Mag can do is exceptional,  just the opposite actually.  Except that that single airplane can so some of everything,  all in one flight,  for so long,  for so little.  Although personal ability to fiddle with things,  or some help getting started (most of us needed both) are requisite,  a Mini Mag can be assembled with a minimum of RC building experience.  Of that which you can purchase,  most of what makes my airplane such a great flier is component selection,  my airframe modifications are mostly for durability that is hardly required at Mission Bay,  or to accept some power combinations that are as effective as they are unusual.

Give it a gentle push or amp it from the landing gear,  turn circles at head height at twice walking speed for as long as you want,  blast up a thousand feet in seconds and take minutes to glide down,  enter loops from that slow glide speed level flight by just pushing the power level forwards,  start the loops small and make them bigger,  or start big and go smaller,  just keep playing for twenty minutes to half an hour with even the economical setups.  Land at Mission Bay on the landing gear,  or with a folding prop a taped belly,  land on almost anything if you add a bash plane and fiberglass armor.

A Mini Mag is Economical
Lucky that my wife and I are still in love,  I have a roof over my head and a car to get around town with,  what my spouse can give me for pocket money amounts to what I used to net out for a couple of days work.  The least expensive way I know of to acquire a new project is to buy a complete airplane,  used,  in good shape. At the twice a year big RC swap meet in Lampertheim,  Germany,  that Mini Mag was fully fitted out including floats,  there wasn’t a dent on it.  So,  at the end of the event when prices drop,  I bought it.  In October 2010 for Euro100/$150-  I began again flying again,  what I had set aside as a dull airplane two years before,  a Mini Mag.

They Left a Lot Out
Waiting out the recession in Western Germany,   this weather has been magnificent this October 2011,  before winter sets in,  with my yearly visit back to San Diego to look for work still months away.  I usually fly either alone or with a couple of friends out in farm fields with asphalted access roads. While researching the Internet for clues about building their airplanes I realized that most of what you can find includes some big (deliberate) omissions,  and that I am using combinations nobody else has written up.  Commercial magazine articles not only censor a lot out,  they restrict themselves to flying with the recommended equipment.  How mundane!

A few times a year I attend a club event,  for the same reasons I enjoyed our Mid Winter Electrics.  This year included two “Foam Gatherings”.  From the experimentalists to RTF,  from just starting to semi-professional,  Electric,  Reciprocation or Jet (yes,  a $3000- kerosene burning turbine mounted on a Multiplex Elapor foam airframe,  it was great),  all were welcome.  If there was ever a bunch that regards foam airplanes cast in molds as just a starting place,  they are it.  If you ever wondered what nerds at critical mass would be like,  visit the MWE,  or similar.

Even though  the sponsored,  paid to be there and show off pilots (including the many times world indoor aerobatics champion) demonstrating Multiplex and Robbe products weren’t doing they’re best,  there were at least two other amateurs among the hundreds of pilots there that came up at least nearly equal.  I knew my airplane flew well and that I’m a proficient pilot,  but when they all come over to find out “What to you have in that thing!?”,  I realized that maybe I did have something out of the ordinary.

The Journey Begins
I bought my first Mini Mag from Sureflite on Convoy Street in San Diego back in 2005 when the affable owner had just become a member of the SESFD,  his Shurflite store on Convoy in San Diego was new.  If dealing RC stuff was a crime (contributing to the delinquency of an adult?) he would be guilty as that airplane now has (350) flights on it.  I paid $55- for the third Mini Mag kit he sold,  it made it’s first (147) flights with NiMh batteries and brushed motors before I set it aside.  As I noted in my book ‘So,  You Want to Fly RC’  lets just forget about that old stuff.

Just for nostalgia,  I kept one Batteries4you ‘Torque Monster’ Speed 550 sold to me about 1999 by a dealer in a Chevy van down at Mission Bay.  He is currently the Editor of this newsletter.  When he realized that I was going to spend the afternoon dozing in my camper van he loaned me the book  ‘How to take a Shaving Cream in the Woods’.  I enjoyed reading it,  what goes around comes around,  as editor he asked for some model reviews.

Picking Up the Trail Again
Buying an airplane used is like a little mystery.  Since at that swap meet every single person there is an RC enthusiast,  the most common reason is not enough room.  In this case,  sadly,  the owner’s reflexes had declined as he neared the end of the journey.  It made me think of our former SEFSD carrier pilot (recently a previous SEFSD newsletter editor),  and that all of us have a time limit,  somehow,  go out and do something worthwhile every day.  Even if you are almost,  but not quite,  completely broke.

Even the Extra Stuff gets Used
That used Mini Mag must have been originally fitted with a sticks out the side brushes like Astro-Flights motors were,  as the motor area was clearanced for them.  And,  it had been crashed at least once as the motor mount was fitted warped.  Uncovering the servos revealed four HiTeck HS-55s,  always a good choice for this airframe.  What I thought at first was an older Multiplex pre-LiPo (12) amp motor controler turned out to be the early,  superceded,  version of a (37) amp one.  That Speed 400 optimized for (40) watts-out black prop had no business on the,  now discontinued,  but a decent performer,  Multiplex 400/8D (250) watts-in (75) gram brushless motor.  With that minimal prop I was surprised to discover such a good motor behind it.  And the floats.  Depending on how you figure it,  I had just secured,  used,  about Euro (250) in equipment with an estimated thirty flights on the airframe.  Your experience may vary.

The (28) mm diameter motor was glued into a Multiplex Easy Star,  where it is providing spirited performance on 3S LiPos at twenty amps.  A (75) gram inrunner with a kV of (2500),  it would go just as well  in a Mini Mag,  provided the pilot can make use of the impressive thrust (and a larger diameter prop) of (150) watts-out.  If there is a down side to an inrunner in a Mini Mag it’s at very slow speeds when the weight,  of not only the motor,  but the battery and controler that can provide (25) amps,  pushes the minimum flying speed up a little.  For maximum output on 3S with fixed lead controllers a suitable inrunner takes a (7) inch prop,  which doesn’t get as good a bite as a (10) incher prop at just above walking speed when used with a (80) gram (18) amp outrunner setup on (20) degrees lead with a 4S LiPo.  That,  and that it’s not a conventional solution.

The floats were fitted to a new friends Mini Mag,  his first successful RC flying experience after trashing four other airplanes trying to learn by himself.  With which it provided some worthwhile diversion flying off snow on some otherwise dreary winter days.  Unexpectedly,  for many middle aged beginner pilots flying an airplane that looks like something at a commercial airport is important to their recognition of the attitude of a RC airplane. He would have given up RC except for bicycling past me slope soaring a (150) watts-out Reinforced Mini Mag in between trees on an otherwise fertilizer day in gusty wind with snow on the rocky ground lacking any apparent place to land.

The,  rated at up to (16)  NiMh cells volts Motor Controler (from research in the Internet it had a nasty,  airplane ruining,  habit of shutting down in flight if run too close to it’s maximum capacity and then operated at partial amps,  that was fixed on the Mark II version which also had LiPo voltage cutoff ability),  was fitted with a Castle Creations BEC and mounted in a very durable Depron/Fiberglass Ugly Stick like airplane a.k.a. Thor.  I thought I had lucked out and found a high voltage motor controller if used with a separate BEC.  On that airframes flight (110),  running on 4S LiPos,   the  motor controller’s BEC disconnected using my only Castle Creations BEC to power the radio,  the controler burst into flames burning up the airplane before I could land it.  I smoked motors,  controllers and batteries along they way,  but never before a whole airplane.

The Speed 400 propeller has,  like all my Speed 400 (50) watts-out stuff including folding propellers with (3) mm hubs,  been removed from service.  We now have power levels that can do serious,  even fatal injuries.  Brian mentioned being present when a (then about three horse power) F5B pylon racer threw a propeller blade between a pilots ribs,  killing him right then and there.  Although the under (300) watts-in of the  propulsion in a Mini Mag can likely only mangle fingers,  or wreck an eye,  don’t push your luck.  Even though at (700to800) grams a Mini Mag itself is unlikely to cause a fatality,  the shock of it hitting somebody,  or a car,  can cause a disastrous secondary accident.

Since it’s Molded Into the Airframe,  a History Lesson
When the Mini Mag came out the only economical propulsion was a (7) or (8) cell NiMh battery powering a Speed 400 on direct drive.  There were only a handful of ready to fly ARFs,  all of them had some fatal weakness that had to be improved.  With the then brushed NiMh propulsion a Mini Mag just barely flew,  even with the under cambered wing to maximize lift at minimal flying speeds.  Oh you could have fitted the motor with a transmission to turn a bigger prop,  and there were more powerful brushed motors available,  but gentle describes the available thrust,  heavy the available batteries.  Rudder and elevator were standard (they still fly fine that way),  cutouts were included in the wing to install ailerons and servos,  two of them,  so you didn’t have linkage hanging out where it gets tangled up on all sorts of things during transport and creating unnecessary air drag.  Just that (40) watts-out on seven cells motor weighed (100) grams.  The motor mount is still configured for exactly that (28) mm size,  and fortunately,  weight.  That Speed 400, prop,  and controler cost about $50-.

Using a Speed 400 in a Mini Mag we had thrust for about four to eight minutes.  Aerobatics were done by climbing,  then diving to get up speed.  At that thrust to weight level flying upside down was nearly impossible.  You had to climb up there and roll it on it’s back,  even at maximum watts-out from a fully charged battery it took the additional speed from diving to maintain control inverted.  It also took the skill to remember,  while wrestling an airplane that wanted to be upright,  to either roll it back to normal or complete the loop,  before impacting the ground.  I have been a bad example for some time now,  but then I learned from the best of them.  Equipped with modern propulsion components a Mini Mag may be easily flown inverted for as long as the battery charge lasts,  but it’s far from elegant.  The next step up,  a brushless motor setup,  cost four times that.  I saw exactly one Speed 400 sized brushless motor from 1995 through 2002.

Somewhere in the early 2000s,  brushed motors in the (28) mm diameter size,  along with their controllers became readily and affordably available.  My first one,  at (50) grams turned a Graupner 6,6X3 prop on (8) AAA size NiMh cells in a Mini Mag for a dramatic improvement in power and duration.

Back in the late 90s,  Steve Neu was featured in a Japanese RC magazine,  in which they proudly pictured three of his brushless motors,  they were that exclusive back then.  Dr. Jet,  the other advocate of brushless power,  thought they were giving the false impression that all Americans just had them laying around.  Even though there were brushless in the (28) mm diameter,  it seemed ridiculous to be using them,  at that kind of money get a bigger one and put it in a real airplane was the consensus.

Let’s Assemble a Mini Mag for You
Even if Bill Knoll,  a.k.a. Dr. Jet ,  former SEFSD president,  was open and notoriously,  even obnoxiously adamant (too much talk radio?) about being exclusively heterosexual (he was even married to a woman,  once),  he has gone missing for a while now,  the other civil engineer in the club,  the intelligence behind The Stink Bug Works,   he may have coined the term assembling,  instead of building.  For a Mini Mag that a majority of you will be flying,  it is correct.

Part II goes into the Reinforced Mini Mag,  that you have to build a little.

If you had built a Mini Mag lately,  do nothing extra,  everything works perfectly out of the box,  you omit the decals,  the radio requires no programming,  none of those little bitty linkage parts reminds you how essential it is by rolling off the bench to hide ect.  it would be possible to assemble a stock Mini Mag in about three to four hours.

Let’s split it into three parts:
Airframe        The wing will be covered in this Part I.
Propulsion        touched on in Part I,  it will be elaborated in Part II
Armor        Toughening up the fuselage,  it will be in Part II

Airframe,  the Wing
See my book for beginners about assembling the Easy Star,  most of it applies here too.  One change,  don’t use Goop glue any more.  I’ll update the book this winter.

Although my personal Mini Mags have been refitted with different noses,  that comes up in the armor section,  let’s start with what an average pilot/bilder with a stock fuselage might to do.

You could just go and glue it together according the directions.  I would agree with that.  It results in a fine flying sport RC airplane well suited for Mission Bay.  If you aren’t expecting the airframe to last for years of flying,  you land at Mission Bay and are ok with propulsion in the (28) diameter it is fine just as specified by Multiplex.  Of all modifications I make taping the front of the wing with clear packaging tape heat shrunk on is the most important.

If you are not competent as a builder,  buy the Radio Ready version,  and have it checked before flying it.  Other then not being able to substitute a lighter wing spar and being restricted to using the,  entirely suitable (best choice actually),  from Multiplex servos,  the modifications can go on just as well as if you assembled it yourself from the pieces.  Fact is,  if you are starting out with nothing,  your best economical choice is to get the whole package from Multiplex including the brushless power.  They are well matched,  durable setups that provide many hours of enjoyment at the minimal net cost.

Although he has moved on employment wise,  the previous to this year,  HiMax Multiplex systems were selected by a fellow SEFSD member.  When we finally met,  he enjoyed the recognition that even a somebody who had had at least thirty different power systems in a Mini Mag thought that his was the best average place to start.

However,  you are going to be carrying those relatively heavy (23) gram fiberglass wing spars every single flight.  Replacing them with (9) gram carbon fiber tubes costs about five bucks.  Do it.

Get some top quality packing tape to reinforce both sides of all of the hinges.  That thin hinge section of these airplanes isn’t strictly reliable,  the tape adds about an hour to building and eliminates failure there for the life of the airplane.  The first unreinforced hinge to give out is usually the elevator,  right in the middle,  at around (75) flights.  The hinge tape might add as much weight as (10) grams.  The top quality spray paint I use sticks to it just fine.  At (10) grams on up,  the paint can easily add more weight then the tape.  The control surfaces have to stay on,  you have to see the airplane’s orientation in the air.

Use the same tape and cover the leading edge of the wing for abrasion and transportation resistance.  Even with loads of taping experience I remove,  discard and try again about one piece of tape in five.  Use of a covering iron lets you form around curves just like iron on covering.  The heat also activates the glue for a much better bond.  The same for the horizontal stabilizator.  This adds about (4-6) grams and takes about an hour.  That tape reinforcement of the leading edges isn’t strictly required for Mission Bay IF you always land on the runway.

I know it doesn’t matter,  but those quarter sized casting indentions bug me.  I may not be into spiffy looking airplanes,  but they need to fly right and a smooth airframe looks better anyway.  Lightweight spachtel fills them in fine,  use a very fine grit (220) or higher and sand slowly to avoid scratching up the elapor.  Water-base spachtel shrinks on drying,  it takes a couple of layers.  The spachtel lasts as long as the airplane if you either cover it with tape or paint.  This adds about fifteen minutes,  it might add a couple of grams.

Although modern computer radios can make all kinds of adjustments,  the closer you are with the mechanical settings the better off you are.  Get as good a match on the aileron servos pair as you can,  the neutral angle of the control arms of even affordable,  reliable Hiteck HS-55s and Multiplex Nanos don’t always match as a pair. The half again more expensive HS-65 servos not only provide far better positioning,  they pair well.  Glue them in them so that they angle one notch forward of straight down to create differential,  about (20-30) degrees is right.  Even with the outmost hole on the control horns when used with the outermost hole on the servo arm provides about twice the usable travel.  A Mini Mag will fly with equal up and down travel on the ailerons,  but it’s a lot more balanced if the up aileron travel is about half again more up then down.

If you are interested in trying better servos and only want to pay for just one,  put it in the elevator.  The next step up is three,  elevator and ailerons.  Unless you have plenty of cash,  the rudder isn’t used much and it probably isn’t justified as being improved over HS-55s.  I used to advocate leaving out the rudder servo,  I don’t anymore.  The power available from current setups outweighs any weight advantage of just (8) grams by omitting the rudder servo.

If you want a “traditional” flying experience with a Mini Mag omit the wing servos and fly with just rudder and elevator.  The aileron servos may be easily added at any time.  Fitted with a (45) gram 3S “basic” power combination a Mini Mag can bring back old memories,  without the week it took to build the old balsa stuff and the endless repairs.  Since I gave up on nitro,  methanol and caster oil I’m a lot happier flying.

Although no doubt that trough down the bottom of the wing at the spar has minimal effect on drag at the original minimal air speed,  I cover mine with heat shrunk on packing tape.  Tape is easier lighter and more effective then spachtel,  if you know how to use a covering iron.

With replacement wings easily available for twenty five bucks,  fiberglassing the outboard portion may not be a best solution for many of you.  But it’s why my German Mini Mag’s wing tips are still on after (250) flights including some horrific landings.  We aren’t talking that nice smooth sandpaper runway down by the boat ramp in San Diego,  more like where ever I happen to be.  Like Point Loma,  where I have never seen any other RC airplane with propulsion flown.

Fiberglass over foam can be a big improvement,  but if you aren’t ready to try it yet,  that’s ok.  You might try learning how with water based hardwood flooring paint.  Start with the (9) ounce per square yard fiberglass.

For a friends latest Mini Mag,  named The Johnny Cash,  after the country western song about a Cadillac factory worker that got it one piece at time,  because he tried ordering pieces out of the Internet;  Assembling the wing took up about three and a half hours.  If you want a Mini Mag,  just buy the whole kit at one time!

Sanding took an hour.  The most important,  cleaning up the casting flash at the leading edge,  took five minutes.  Taking off the casting flash at the trailing edge counts too.  If you are wondering why my Mini Mag flies better then yours…
Taping took up half an hour.  Getting the servos just right takes about fifteen minutes to half an hour.  I run my control arms at 30% to forward,  some trimming of the foam to clear the pushrod and servo arm is required.
Gluing in the spars and horns fifteen minutes.
Fiberglassing the outboard tips took half an hour  ´
Paint,  a very simple scheme with spray cans,  took fifteen minutes.  Cutting out and applying the first rate from Multiplex decals would take just a little longer.  If you iron them on they go over the curves better and will out last the airframe.

If all that seems like a lot,  that near retirement age enthusiast clerk at the hobby store where I was pondering building my first foam coar wing (a Ninja slope soarer,  still available,  a good sport slope glider) went straight to the conclusion “after you build your first foam coar wing you will never build another wing out of pieces again”.  That was 1994,  he was right.  You can’t build a wing as good as the Mini Mag ’s yourself.

The irritating flexibility of the Mini Mag ‘s wing,  which,  along with the dihedral (that built in shallow V) along with high wing (only the tips drag on landing) may preclude precision,  the under camber means you can hang it on the prop but not go all that fast,  but,  they provide stability.  A Mini Mag wing will withstand an incredible amount of bone headedness.  It is a vital part of what makes this take anywhere,  do some of anything RC airplane such a wonder.

Just in Case You don’t get Part II,  Some Motor Combinations

Let’s start with Multiplex specs out.
For now (they may be selling the last of them off as they are converting to all outrunners) it’s an inrunner.

HiMax 2815-2000
86 grams  (Speed 400s were a little heavier)
28 mm diameter by 38 mm long  (just about the same as a Speed 400)
2000 kV  (about as low as an inrunner that size was ever wound for)
Maximum sustainable watts-in 275
5.5X4.5 APC propeller

Multiplex put a simplified version of a virtual-dyno on their web site.  If we input their motor,  3S LiPos and a 5.5X4.5 APC prop i.e their setup it calculates:
15 amps
125 watts-out
28 ounce of thrust
If there were no slip at the prop (as if the propeller were turning in a solid material at it’s rated pitch) it would fly at 83 miles (with the power of a full charge,  it drops off as the battery runs down) an hour for eight minutes.

This looks like the same virtual-dyno that our Editor made available from his Fly DMA website (now closed),  where it based on NeuMotors batteries,  just with a lot less information in the output and only the motors Multiplex USA offers.

It was no surprise that when NeuMotors offered what apparently is the same virtual-dyno they continued to use their batteries,  in addition to offering a second wide open,  you put in every coefficient,  version.  If you are planing on world beating performance,  you had better re-check that equation because if you are already running a NeuMotors,  something else is the unknown.

Why Multiplex didn’t substitute their own line of batteries in their presentation of a virtual dyno is curious.  There’re right around the corner in Poway,  somebody ask them please.  Tell them a fan thanks them for letting their airplanes be modeled on simulators,  we have this awful yearly event in Germany called winter.

Conclusion;  Multiplex is running this motor at well under what it can deliver as in reality about (150) watts-out is about all that can be enjoyed in a Mini Mag.  This is a “happy”,  durable,  fun,  if slightly heavy combination that will be lacking in low speed thrust in favor of mid range speed.  That small diameter fixed APC propeller has a better chance of lasting a while as the larger diameters take it harder on a nose over and tip onto the side event,  and,  it doesn’t torque the airplane over on abrupt application of full watts.

If we divide 275 watts-in by 11.1 volts this motor should be able to run continuously at (20to25) amps,  not the (15) it’s drawing with that 5.5X4.5 propeller.   From the Multiplex specification motors I’ve used their (2500) kV (70) gram motor rated at (250) watts-in can withstand (20) amps,  this one is at (86) grams a little bigger,  so that seems about right.  I’ve flown Mini Mags at (275) watts-in.  That high an output of (200) watts-out it isn’t necessarily fun,  it’s only for a few pilots that can use it.  The prop is pulling the airframe faster then it flies comfortable at,  even if the net efficiency isn’t all th