Monthly Archives: March 2013

 

Unlike other projects,  this report was issued way before getting fifty flights on it as the author just didn’t feel enthusiastic about the DogFighter,  and a loss of orientation on flight twenty four resulted in writing off the airframe.  Thanks to Elapor’s original use as an impact absorbing packing crate material,  with the exception of the propeller,  motor shaft and battery the components were reusable.  This one and I just never did hit it off right,  I won’t be getting a second one.

 

I haven’t ever flow anything from World War II,  
as close as I’ve come was a ride in a racing T-28 Trojan in exchange for a couple of days TIG welding back about 1990.  Think of hitting two hundred miles an hour at just above retracting the landing gear altitude followed by flying straight up for a couple of thousand feet and then straight back down.  Since I didn’t puke the pilot decided I was ok.  I have seen full size warbirds flown at air shows.  The Germans have a competition,  kind of like the control line combat I flew in my teens,  only with RC,  I haven’t seen it though.  On my Real Flight 5.5 simulator there is nothing quite like the Dog Fighter.  So if the averaged Jak/Spitfire/Messerschmitt like Multiplex,  new for 2011,  foam Dog Fighter airplane is anything like them in the air,  I can’t confirm it.  

 

We had been seeing the advertisements in all the media for months,  
the friend that I fly with here in Wiesbaden had been enjoying having gotten the hang of RC flying and,  after a few brushes with lesser quality stuff,  was enjoying exploring the simple,  durable Multiplex airplanes. For Euro200/$300 he bought the complete,  ready built Multiplex DogFighter as soon as they became available.  That deal,  three Nano-S servos (HiTeck HS-55s like with longer leads and maybe better quality control),  a decent HiMax motor and a adjustable timing with up to 6s controller on an aluminum motor mount and a fixed APC propeller was so good I was considering buying one myself.  I detoured to a Fun Jet Lite instead.

 

We shut the world out for a couple of hours that unreasonably warm sunny fall afternoon,  the two of us were as excited as teenagers as I finished the assembly.  One thing was quickly clear,  the standard issue fixed APC propeller wouldn’t likely survive even the first landing on our grassy farm field,  and didn’t fit either.  I arrived with a suitable Aero-Naut folding propeller,  after some selection we fit it with 9X6.5 blades,  with which the motor drew (37) amps on a 3S 2200 mAh LiPo.  A little too narrow for this airframe,  at (30) degrees it folded enough for the grass plus molehills landing field,  but not flat.  The set screws for the control surfaces were factory installed,  too tight to adjust,  we took advantage of the six channel transmitters ability to correctly zero the ailerons.  Using the differential function the up travel of the ailerons were set at (1.25).

 

A decent shove,  it flew,  half fast and straight,  rolls were axial.  But too much thrill to fly,  it was a nervous little beast.

 

When you read things you lose the calibration of physical reality and the relationship of the pilot to his equipment.  I’ve seen enough equipment in the hands of beginners that I would be very hesitant to diagnose problems without at least photographs.  See my report on The Blizzard,  where due to a simple gluing error and casting flash the tail was angled up enough to ruin the flight characteristics,   for a assembler/pilot that belonged with slow airplanes and modern ARFs.  I followed one text thread where somebody tried to diagnose somebody’s problems with a Multiplex Fun Jet Ultra,  it wasn’t until the fifth exchange where the pilot reported having flown F5B (those now seven horse power rockets) before the other pilot realized that maybe his expectations were off,  after you’ve flown F5B ANYTHING else is sluggish and slow.  

 

But pylon racers are stable airplanes,  the pilot only needs provide guidance.  The DogFighter can withstand our Mission Bay landing conditions,  however the pilot had better have quite a bit of experience,  and the reaction times of a twenty to thirty something year old as they are going to be constantly put the test.  With ordinary equipment The Dog Fighter is affordable.

 

Somewhere around flight twenty,  the original owner realizing that what he enjoyed flying most was his nearly indoor light Depron Event 3D (on no wind days) and the Multiplex Parkmaster and Gemini.  For windy days or when the weather has left us with marginal landing conditions he has a Brushless Twin Star II.  When the radio lost contact with the DogFighter for a few seconds,  he transferred it to me.  On reflection,  his radio may in fact have been fine.

 

There was another one in our flying group,  also fitted with a folding propeller.  The best,  if maybe only application of this airplane is combat as it is neither blazing fast or acrobatic.  One thing that cut speed down,  that blunt front end from propellers that didn’t fair in as planned.  That and running on 3S with only moderately effective motors.  

 

From the national German magazines “Foamie” (z. Deutsch die Schaumwaffel) and FMT,  the now available even hotter motor setup substitutes,  at the same (135) grams weight,  a HiMax 3516-1350 with a simple motor controller is replaced with a same size HiMax 3516-1130,  a bigger (70) amp controller instead of the (54) amp one and,  at APC 9X6,  a smaller diameter propeller.  Unfortunately,  although the author did publicize his in the air logged ampere (peaked at fifty amps with the battery fully charged) and voltage measurements,  he had to estimate the top speed as (170) km/h,  or about one hundred five miles an hour. He also published a flight data log that demonstrated that at an average of (5) amps at (11.4) volts that a so equipped DogFighter can just stay airborne for twenty minutes.  They forgot to mention how nerve wracking flying this airplane can be,  even after software limiting the aileron travel to about (70) % of factory assembly (aileron rods hung on the middle of the three control arm holes) and using (35)% exponential.  Rolls are what ever comes,  it has almost no self righting in that axis,  pitch stability isn’t all that good,  yaw is about average.  It’s very easy to lose the orientation of the DogFighter at distances over fifty meters,  which at fifty to a hundred miles an hour comes very quickly.

 

So,  the DogFighter is bigger and more agile then a Speed 400 pylon racer,  with much more duration and,  if you don’t slam it into the ground,  vastly better durability,  but it’s not much faster and if anything too maneuverable.  Hmm,  what to do?

 

Just this once,
I have an idea what the airplane can do from having watched thirty flights.  We were landing on (then) soft grass,  but winter is already here.

 

The fiberglassing began.  The canopy,  beacuse I suffer from greasy fingers,  it was treated with a coating of (20) grams per square meter fiberglass secured with hardwood flooring paint,  except for a little thicker right at the finger grips and the “tong” which received resin,  the weight gain of (3) grams bringing it to (18) grams.  Although there are spinner cones for folding props as big in diameter as the nose,  they cost Euro40/$52- and weigh a bunch,  the top was initially narrowed to match what I have.  As I started the fuselage,  with one,  from the factory installed Nano-S servo,  weighs (162) grams before the reinforcement began,  it weighed (175) grams afterwards.  

 

The wing has two from the factory installed Nano-S servos,  before working it over it weighed (152) grams. Wing tips take it hard,  the outside (30 cm was treated with fiberglass held with resin,  after taping the leading edge of the wing with heat shrunk on packing tape the wing outside of the servos was treated with (20) gram per square meter fiberglass with paint. Although the scale like panel lines probably make no difference,  I need a surface hardening to the bottom,  the lines were filled with lightweight spachtel.  After which it weighed (157) grams.

 

The nose was rounded to better clear folding propellers.  It’s too large a diameter to really get them to fold without taking a lot of material off.  The underside was treated with fiberglass/resin,  the rest fiberglass/hardwood flooring paint.

 

The vertical stabilizator was painted a bright red as where the underside of both wings,  the top sides of the wings was a bright yellow.  Dull,  as all of my airplanes have the same paint scheme,  but effective.

 

As expected,  the contact area of the latest style control horns is too small,  One tore lose after twenty one flights,  so all three were treated with fiberglass reinforcement from the control horn to the control surface.

 

Those HiMax motors are a good value,  
which isn’t apparent from the first flights as durability and resistance to overheating have to be flown to be realized.  But,  the airplane is only fast,  I wanted to explore what it could do at a lighter weight.

 

The “cowl” was cut back from (3) cm from the front after profiling it to accept a folding propeller a little better,  for (7) cm.  That leaves (3) mm both at the front and back of that long nose.  The “hump” was removed with a knife,  so that the battery may be installed right behind a lighter then stock motor.  Being Elapor everything could be set back the way it was if the modifications don’t work out.

 

The first disappointment was that the hoped for combination of a (45) gram motor with a folding 7.5X4 prop and a 4S 1100 mAh (120) gram battery wouldn’t make balance.  It took a 4S 2200 mAh (220) gram NeuMotors battery.  This combination drew (17) amps at (14) volts at (720) grams.  As expected with an estimated (190) watts-out performance was just ok.  The first flight the prop threw which disappeared in the frozen long grass on that under breezy wind out of Siberia day.  Just the same I slope soared it for a while.  Despite the light armor on the nose,  it took a dent on landing in a frozen field.

 

The (45) gram Graupner was then fitted with an Aero-Naut 6X5.5 fixed propeller,  with which it drew (12.5) amps at (15) volts peaked in the basement at (60) F.  After deducting one and a half amps for just past the peak that works out to (165) watts-in.  Affordable (Euro32/$43-) it has “flip right through magnets” which should put the P-Calk efficiency in the 0.8- range for (130) watts-out.  Although the motor can probably sustain a little higher current,  the diameter of the fixed propeller sets the limit.  Those Aero-Naut propellers are stronger then APCs,  all of them are high pitched.  On grass landings it’s a guess if the pilot can coordinate getting the propeller horizontal of risk landing in the grass with it vertical.  Performance was just sort of ho hum,  if that inexpensive controler can be programmed for a brake isn’t known,  the prop didn’t stop in glide.  But I just didn’t like the Dog Fighter.  The difficulty being that I’m not into ruining my RC airplanes trying to cut other airplanes streamers,  so I don’t have any requirement for something that unstably nimble.  I haven’t had anything like it since a combat flying wing with a too sharp leading edge.

 

The first Lite try was a NeuMotors 1105 with the chancy combination of a folding 6X3 on (3)mm hinges with a 3S (185) gram 220 mAh battery.  Chancy as the NeuMotors revs up way higher then either the hub itself or the 3mm hinge Aero-Naut blades are rated for.  So sort of ok for a couple of flights,  just don’t get complacent and continue using them.  All up weight was (700) grams,  it drew (37) amps on the bench at 10.7 volts.  The combination took the DogFighter straight up.  Interestingly,  that is the same current draw at the heavier ((135) grams verses (70) grams for the motor with the same battery) HiMax combination.  That works out to about (300) watts-out.  Where the NeuMotors combination losses it’s edge here,  despite the better efficiency of a racing motor,  is that it took a much smaller propeller that is probably not as good a match to the airframes requirements.   It flew,  but nervously.  Any comparison to the stock combination was excluded,  I was flying at freezing and have no direct way to quantify speed.  As far as weight goes,  it was slightly lighter,  and so slightly better handling.  A count of ten climb resulted in count of sixty to seventy on the way down,  which isn’t a valid comparison with a battery operating at more effective temperatures.  That and establishing the best angle of glide takes some practice.  Just the same a count of ten climb sent the (300) watts-out DogFighter “way up there” at least twice as high as the height restrictions of Mission Bay.  The noise was a plastic “first generation” motor mount plate (acquired with a Gemini kit,  it saw seventy flights in a Fun Cub including a crash so bad that the output shaft of a smallish motor bent,  despite the folding prop) that had warped so that the motor,  already turning higher then the propeller blades or hub were rated for,  vibrated.  The latest aluminum motor mount plates as well as the issue plastic ones for the HiMax 11XX series (135 gram motors have a bolt circle too large to mount either the 11xx series NeuMotors or 28mm common sport motors.  Subjectively a little easier to handle then the original specification propulsion,  but it wasn’t necessarily fun to fly.

 

Repairs would have meant a complete new nose.  The wing was repairable,  but dinged up.  The motor output shaft was broken,  the rest of the motor with a replacement shaft was ok,  how the bearings were remains to be determined by use.  With these inexpensive motors the bearings aren’t all that good to begin with and quickly get used up.  The receiver and motor controller seem to have no damage.  The 4S battery has at least one cell so dented that it will at a minimum have to be converted to 3S.  Although the fuselage rails were ruined,  the motor mount plate doesn’t look any more warped then before the crash.

 

After thinking it over,  the banged up airframe was cut up and discarded.  I just didn’t have any use for an RC airplane so squirrelly that it had to be flow in still air.  It’s a hundred Euros for just the airframe kit.  Another hundred gets the prop and collet,  a worthwhile motor,  a better then before motor controller,  and three servos,  all installed in a well built straight airplane.  Multiplex threw in the assembly and the parts to fit it out for less then just what the parts cost individually.  That being built straight isn’t automatic,  if you misuse the glue and don’t have a straight line for the fuselage halves they can easily be warped when gluing in the stiffeners.

 

Flight 4/20  Under Igstadt  01 February 2012 (We.)  Cold but clear,  with some wind out of the east.  My diesel van wouldn’t start,  so I drove my car instead.  Some warning about the temperature,  my hands went partly numb before the heater kicked in.  It’s only a little below freezing,  when it comes to cold I’ve become a softie.  If you see me down at Mission Bay in a wet suit I’m not being weird,  I’m just still so under cooled from hunting in the ocean (55 to 57 degrees F on the surface,  colder at lobster depth) on the to take the rubber suite off until I warm back up.
 
The start of the flight went well,  although with it’s nasty tendency to roll in this gusty wind I stayed high.  Lining up for a couple of practice landings it was hard to tell when the rocking was from the gusts,  or nearing a stall,  the nose has to angle down to glide this thing.  It’s six weeks past winter solstice,  at 10 am the sun is only about twenty degrees above the horizon.  Out there about a hundred and fifty meters not far off from the sun,  the wind rocked it,  I couldn’t tell which way as against the sun at a hundred and fifty meters all I could discern is the outline,  after half an hours flight it hit straight in from about twenty meters up.  From “I have a problem” through “oh no” to the impact was about two to three seconds.

 

That’s three propellers lost (equipment broke) and three crashes in the last two weeks (two repairable,  none due to equipment failure) after flying the last two years with no significant losses.  Thinking back on it I have lost a couple of airplanes to getting bored and flying them too hard,  lost a couple of Easy Stars when the wings separated in the air and a few more airplanes to equipment failure.  This is the first time I’ve trashed an RC airplane because it was too hot for me.

 

Flight 3/20  Across from Sonnenburger Turm  31 January 2012 (Tu.)  With the 11.1 volt (45) gram Graupner motor and 7.5X4 Graupner 3mm pivots folding prop.  Kind of breezy,  the prop flew off after just a couple of climbs.  That was disappointing as it was slope soaring ok.  That prop is the latest to get lost.

 

The vibration was mostly due to the motor not sitting square against the warped motor mount plate.  That plastic is hard stuff,  it took twenty minutes and a thousand strokes to sand the motor side back to flat.

 

Flight 2/20    Sonnenberger Turm  Last Monday of January 2012
Way too noisy,  indications that the motor wasn’t harmonizing right,  it was landed early.  After finding no apparent reason for the vibration the battery was changed,  an aileron connector had torn lose despite the perfect landing on half long frozen grass.  No second flight was made

 

The ailerons were balanced neutral with sub-trim
The aileron throws were cut back to 70%.
Exponential of 30% was added to the ailerons.
UHU Poor was used to lock the motor mount screws.

 

Flight 1/20    Under Igstadt  The last Monday of January 2012 with a NeuMotors 1105 on 3S and a 6X3 folding prop,  best available Aero-Naut blades that still aren’t rated for that high an rpm.
Noisy and half fast,  climb can be vertical,  but very nervous to fly.  First flights are always nerve wracking,  but this doesn’t seem like it’s going to lead to a fun to fly RC airplane.  After ten minutes as the sound indicated motor mount screws working lose it was landed early.