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

A Depron with Cheap Components Biplane The Pitts Python from PAF-Flugmodelle And The Pichler Models Depron Extra 330



It now seems as we have had indoor “Schockflyers” forever.  But it’s only been ten years since Martin Müller  with the first Shocky (German for the lightweight Depron based indoor electric RC airplanes) rocked the (indoor flying) halls.  Since then they have taken a solid place in the Indoor-Scene,  even if the modern F3P models have hardly anything in common with the originals.  Instead of following the trend to ever lighter models,  Pichler  (a German mail order RC company) has a new offering of this Extra in a solider form,  that should function not only indoors,  but also outdoors.

In the beginning we were happy to get the weight of the brushed motors and nickel based batteries Indoor airplanes under (200) grams,  now days (100-120) grams is the standard,  if you want to fly aerobatics indoors.  And too the airframes have been changed,  lots of spoilers and brakes together with light weight are standard,  moving the speeds ever slower.

Simple and Sturdy
Interestingly Pichler has a range of models,  such as the here tested Extra 330,  that look like proper airplanes,  and have the weight of the originals in the (200-220) gram range.

Partly that is because of the construction,  which is particularly simple.  Instead of lightweight tension/torsion bars and carbon fiber reinforcement,  the airframe is made of (5) mm Depron with a simple 5mm carbon fiber tube used as a spar.  With that the raw framework weighs (72.5) grams.  That may be only (20) grams more,  but it’s also (40)% more then a modern Shocky.

The Right Equipment
If the raw frame is already heavier,  then it needs more output under the hood so that it climbs up as expected.  Pitchler didn’t go at it half hearted,  they delivered the test model with a Pulsar P-10-1450 motor at (36.5) grams along with a Pulsar 20-amp motor controller,  that also weighs (16) grams and a Red Power 2S 860 mAh LiPo,  that weighs in at (48.5) grams.  That promises performance in excess.  In addition three Pichler Master S2112 (9) gram servos,  along with some glue and a light weight receiver that already sums up to (225) grams.

Ready in a Jiffy
The Depron parts were lazer cut,  so they fit together like a jigsaw puzzle.  Including waiting for the glue to dry it’s ready in half an hour.  Since the finish is already printed on,  all we have left to do is mount the equipment.  It might take an inexperienced model builder a little longer,  but with the help of the four page construction manual it should be possible,  I’m sure of that.

The center of gravity is dependent on where the components are secured,  it wound up at the rear of the range,  so about (70) mm behind the leading edge.  For the maximum of flying fun the throw on the control surfaces was set at “as much as possible” and by judgement dulled with exponential.  The throw of the standard rotational servos is at a maximum right when the stick is centered,  just the opposite of what we’d like it to be.  What we want most of the time is that small movements right at the center ought to get small movements at the control surfaces.  When all we had was analog equipment,  there wasn’t much to do about it,  with a computer modifying the signal we can now set the transmitter to adjust the throws so that small movements at the stick only just move the elevator,  ailerons ect,  with progressively larger movements getting increasingly larger throws.  Ever wonder why you had to take algebra?  Don’t worry about how the curves,  just try it.  On myDs6i I use positive exponential,  after activating it.

The first flight of the Extra 330 wasn’t made indoors.  When during November in Germany the sun shines,  you had best use it.  November is the month in Germany,  a thousand miles further north then San Diego,  where the sun lies low on the horizon and for the next four months it’s beyond hope that it will be anything but either cold,  gray,  or both.  The translator is from Coastal Southern California,  too hot,  and too cold,  are when shoes are required.  Even the wind can’t hold it back,  at (225) grams it’s not tissue paper airplane.  At full load there are (13) amps going through the motor windings,  about (100) watts-in.  That should be more then enough to take this thing vertical.

So much for starting and landing on grass with this landing gear.  Germany,  with it’s thirty inches of rain a year would otherwise be completely forested.  Green here is natural,  most RC flying clubs,  and even some full size general aviation airports,  are off of mowed grass.  They don’t even have irrigation here,  no use for it!  Their Depron airplanes wheels are usually fitted with Depron  wheel pants that would hang up on anything other then a gymnasium floor. 
So the asphalted access road to the flying field was used for the runway.  Sadly,  the wind is right at cross to it.  So,  the runway is only three meters long,  and staggeringly wide.  Only a Shocky can perform under these conditions.  Because of the headwind the Extra was airborne in just half a meter.  The trim was right to begin with,  the center of gravity too.  Therefore there was no reason to make any laps to get the trim right and feel it out.  On with it,  control stick in the corner and aerobatics.  That’s what this model is built for.

Thanks to satisfying output everything goes.  Blast off straight up?  No doubt!  Rolls?  Them too of course!  Loops,  turns,  dives and climbs?  Of course!  But,  leveling out at the bottom of a dive too sharp bends the wings.  So,  please no with full amps vertical down dives followed by maximum up elevator as that would likely result in the sound of tearing Depron.  But then other models won’t withstand that either.  The show maneuver is hovering into the wind,  in German called Harrier.  This Extra can be angled into the wind to maintain position if being blown against.  It doesn’t matter if that’s upright or inverted.

In the hall the weight of the model is far more noticeable then outside.  The world is in order for straight and level flight,  climb is almost too fast,  but after a loop you must be careful to catch it in time,  you may have to give amps to get out of it.  Otherwise a loop may turn into an upright nine.  Even with that eventuality happened the landing gear demonstrated a surprisingly high loadability.  It bends so far that should the fuselage touch,  it still doesn’t break.  Since you don’t use as many amps in the hall as outside,  the fuselage doesn’t warp as much.  Although it is possible to fly indoors with (225) grams,  to be honest,  once you’ve flown something lighter,  you won’t want to.

If you are going to be flying your Extra 330 SC mostly indoors you should install a smaller motor.  That would easily save (10-15) grams,  in addition a lighter 10 amp controler and a 2S 350 mAh LiPo.  Added up that’s a (25-30) gram weight savings.  Then the Extra enters flying indoors better at about (180) grams.  Indoors the lesser output would hardly be noticed.  Outside and with wind the heavier version is clearly in the advantage,  accordingly I think you should decide at the time of purchase which components for which conditions you are going to fly the airplane.  Either for outside with the test model components,  or for indoors and destinctly lighter.

At Euro30/$41- the Extra 330 SC from Pichler Models is a fair offering.  With the described components you can fly in a light wind outside for a nominal sum to rather enjoy yourself.  Lighter indoor components would be no more expensive.  In comparison with models optimized for indoor flight the Extra  would still be heavier by (20-30) grams,  but that can be accepted,  especially since by omitting the torsion bars it goes together fast and easily.


Time to translate,  who cares.  After realizing that I have the concentration to function as a translator for about as many hours a day as I can perform CAD drafting,  i.e. about three,  and that my net income for the first year would be zero,  for which the day I resume work in the USA the experience would be worthless,  I quit caring about building a portfolio.

Not wanting to repeat the mistake
of the bought used Borjet airplane,  where the original owner way (more then double) over-weighted it,  and I just kept propagating the error,  I looked it up in the Internet from the name on that nice finish.  It turns out the airplane is still offered for sale by PAF-Flugmodelle under the name Pitts Python as either just the airframe for Euro35/$50-,  or as a complete setup with servos,  motor,  motor controler,  prop and battery for Euro135/$190-.  Although I purchased the complete airplane in nearly new condition,  from the description in the Internet it should weigh (270) grams.  The complete package includes a 2S 850 mAh LiPo.  Wingspan is given as (800) mm.  Since the actual flight weight of the airplane as purchased was in the range of (450) grams,  there is no way to get down to the published weight.

I’m a little confused how the weight could be that low as (270) grams net ready for flight,  as just the airframe,  fitted out with three (8) gram servos but no motor/prop/controler,  battery or receiver,  weights (245) grams.  Even if we take the weight of a 2S 850 mAh battery as plus (50) grams (verses the (80) to (90) grams for 3S 1000 and 1100 LiPos as purchased used),  that’s still at least a net (320) grams even with a 2S LiPo.  There is no weight reduction possible at the servos,  hardly any at the motor or controler or the prop.

The airplane is reasonably assembled,  no excess glue or anything,  hum…  The only question is if the carbon fiber tubes used as spars are an original with the kit feature,  or added.  Something that can’t be determined by the sparse information on the Internet (no specific details as what the additional Euro100/$140- gets other then servos,  battery,  motor ect) or the single picture of the complete airplane taken from the top.  At any rate,  although I suspect that those tubes hanging under the wings screw up the flat plate airfoils as I haven’t seen anything like them elsewhere,  they don’t represent even (15) grams.

Flight Three?  The question mark being the uncertainty of how often the original owner flew it.  Under Igstadt  25 November 2011 (Fr.)  A walking pace wind out of the west.  Five shades of gray.  Dry  Not really cold yet i.e. well above freezing,  but this fall was so warm for so long that I had to fly with thin gloves even after putting on the new jacket with a gringo sweater underneath.

Take off was a roll from the asphalt after just a few feet.  With no wind,  the wheels being angled at 45 degrees from vertical (odd,  never seen that before anywhere else) and the tail skid didn’t matter,  it left the ground straight in about two meters.  Shortly after which I realized that the control surface throws were far more then I was ready for.  A good thing that this slight rise is about a meter and a half above the grassy field,  as there is some vertical room for getting a grip on things.  It’s a little nose heavy,  and just barely powered enough.  Loops from level flight are too tight,  the motor runs out of thrust after a two meter climb.  Aileron rolls are way off balanced,  despite some mechanical differential.  It was interesting using the rudder,  but the extra drag quickly reduced it to below flight speed.  It’s slow in level flight,  and not much climb.  It flies inverted about as well as upright.  Nothing I had to date so abruptly came out of the top of a loop on command to fly upside down.  Due to being under powered,  and over responsive to the controls,  no attempts at anything fancy were made. The glide was poor.  All the more so since even at full amps it’s only flying fast enough to just stay in the air,  and yet too fast for indoor use.

On landing at hardly a walking pace a slight push of wind moved it from the cement farm access road over into the long grass at which it promptly stopped.  The right wheel with pant broke off. Whew,  a difficult first flight was over after what felt like ten minutes. All that was holding it the wheel on was a glop of glue (probably hot melt glue,  never a good choice for RC) over the layered Depron wheel pants.   Without more power I don’t see much future for this airplane.

No wonder the previous owner dumped it.  A bad servo and a junk,  new out of the box,  motor resulting in a hardly flyable airplane.

It was hours of fumbling getting it ready for flight.  No real work,  just learning how to deal with this surfaced Depron and,  for me,  new type of construction.  For the first flights the 4S (12) amp regulator which came with the Borjet will be used on the Spektrum AR600 receiver without the satellite receiver.

This thing is short on thrust,  and if more thrust means more weight,  maybe it needs more lift too.  Lift requires either a thicker wing section,  or more speed.  Although it’s going to be used outdoors,  this should be a sllooowwwww flier.  So,  thinking back on the most recent “Foam (flying) Waffle Gathering” (z. E.  Foamie Meet) in September where another pilot was able to get a Folker DIIV to fly well (verses just struggling to stay airborne) by building the wings out from a flat plates to a Clark Y airfoil,  and the interesting reading in “Foamie” (z. D. Schaumwaffel) magazine about simple adaptations to flat plate airfoils in Depron by layering the forward part of the wing with additional Depron;  I decided to compensate for that tube spar in (3)mm diameter carbon under each of the two wings at the1/3 width by adding (3) mm Depron to the top and bottom of both wings.

Just cut out the 3mm Depron for the width between the spars to the leading edge of the 5mm Coated Depron wings,  glue them on top and bottom with contact cement,  round and tape the leading edges.  Although just a better motor alone was probably all that was required,  I’d been reading about it,  I felt like trying it.  The airframe including the three servos and their linkages,  but no propulsion or receiver,  weight went from (245) grams to (260) grams.

Things are still a little warped though,  despite the (3) mm half round carbon fiber added to the lower wings leading edge.  Since flat stock (3) mm carbon fiber is easily available it could be later added to the back of the top “steps” to straighten things more.  If I follow the theory right,  that abrupt termination causes a desired turbulent boil.  Read all about at xxx.  Alternately,  or additionally,  half round carbon fiber stock could be added to the leading edges,  except that they didn’t come in “clean”.  Heat shrunk on packing tape took care of that.  For now,  at an additional (15) grams and two hours time (probably more then to assemble an original kit,  but that’s the way it goes with aeromodeling),  the wings now have a profile,  it’s time to get some more thrust.

In general,  Germany has better consumer chemicals then the USA,  at a much higher price.  The product Por from the manufacturer UHU was used as contact cement.  It’s great stuff.

Concluding that the originally attached Dymond brand motor was junk,  and reviewing my stash of motors,  I decided to try a well used wound way high (35) gram outrunner on 2S LiPos.  If this airplane turns out to be fun to fly,  a new (60) gram Robbe slow turner on 3S or 4S might be a better choice.  I opted for the lower overall weight and disposability of the (35) gram motor for the next attempt.  The propeller saver was swapped over.

My first look at really light stuff dates to somewhere back in year 2000 at an SESFD club meeting.  Two gentlemen,  now long time members who are still always good for something new and interesting,  both showed up with,  what were for the time,  astoundingly small,  radio controlled airplanes.  The Current Editors comment back then,  “mines smaller”  As I noted in my book,  “So You Want to Fly RC”  radio controlled clubs are nerds at critical mass.  I’ve enjoyed the company of everybody I ever flew with down at Mission Bay.  It’s relaxing to be among my own kind where pretense and the manipulation required for commercial purposes can be aside to just enjoy our hobby and each other.

I first saw flat plate Depron fliers in 2003 while visiting a friend (now my wife) in Germany.  Depron was originally offered as a sound insulating material for between floors.  So not quite a packing crate material,  but close.  Aluminum,  in different grades,  gets used as Bier Cans and airplanes too.

The least expensive way for me to get hold of a new airplane is to buy a complete one used.  It’s kind of a “pick it up and see if it’s any good later” event. What I can get at a swap meet frequently determines what I fly for the next six months.

There it was,  right after dawn,  outside the main indoor hall,  where traditionally anybody can take a spot and sell their stuff,  that second Saturday of October 2011 at the twice a year big RC Flight swap meet in Lampertheim,  Western Germany.  Looking new,  priced Euro25\$35- among the other things by the owner,  all I asked was what battery he used.  I was finally on my way to a flat plate Depron flier.

After getting my second Fun Jet going,  I turned my attention to the sharp looking,  hardly used, yellow/black outdoor Depron biplane.  The wing and horizontal stabilizator top sides and both sides of the fuselage stabilized with a nice printed on finish yellow/black  (Pitts Python  Scandinavian Airshow),  it has just a couple of kinks on the nose to show it had ever been flown.  It came with a (35) gram size Dymond outrunner with a big new 10” prop on a prop saver.  Dymond (no, not the missed dealer on Convoy Street in San Diego who had a great selection of props,  but a big Internet company in Germany,  purveyor of stuff so cheap that it doesn’t always work,  and even then not for long) (18) amp 2S to 4S motor controller,  and three blue no name servos.  Everything required for flight but receiver and battery.

Other then the landing wheels having been assembled at the same (45) degree angle as the X carbon fiber landing gear (the metal axle should have been bent to make the wheels upright,  something that was corrected for flight 5),  and some of the single sided tape hinges pulling off,  it looked well built.  Thanks to that coating on the Depron,  other then some folds on the nose,  there wasn’t a mark on it.

On attaching a battery and receiver the aileron servo chattered a bit,  then settled down to work,  as did everything else.  When I tried again later,  the servo quit.  Since I wanted to remove the Dymond AL 2822 1200 Umin/V, 7-15 Volt,  85 Watt motor for separate inspection,  I pulled the servo too.

On inspection the servo was still actively holding centered,  but refused to move.  That would indicate that it was still getting power,  but no signal for positioning.  After pulling the cover to check for a cold or broken soldering joint or broken gear (about all you can do at home) and moving the servo arm,  it started working again.  It might be a case of the little plate that is the variable potentiometer being corroded,  but as there must be some reason why the original owner,  who from the other airplanes he had for sale must be an experienced builder and pilot,  wrote this thing off.

I can deal with a part that is broken,  and fixed,  but something that sometimes works,  and then for no reason quits,  is ruinous,  Thinking about the friend here that started with cheap (if it’s labeled Zebra,  I won’t use it) and learned the hard way that all it takes is one component failure to trash the whole thing,  I wrote off the Euro4/$6- servo. While I was at it I pulled the elevator servo for the trash too.

Buying a used airplane is always a little mystery,  since at that swap meet every single person there is an enthusiast,  the most common reason for selling an airplane is;  No more room,  followed by,  bored with it.  An indoor slowflier type airplane didn’t fit in with the rest of what he had for sale.  That servo with an intermittent failure was most likely why it was sold cheap.

It’s disappointing,  but being almost,  but not quite,  completely broke after selectively spending Euro200/$275- in Lampertheim (plus the sixty mile drive each way),  all I had for replacements are nearly as cheap,  but fast and long travel,  servos left over from a bought used Borjet airplane.  The Borjet’s original young owner wrote off a Euro (270) investment for Euro (30).  His mistake was trying to use a (62) gram motor and 3S 1300 mAh (1100) gram LiPo where the manufacturer recommended a (25) gram motor and 2S 500 mAh  (35) gram LiPo.  He was trying to fly the resulting Frankenstein at more then twice the recommended wing loading,  no wonder the landing gear folded up and the 12X8 APC prop was broken.  I made seventy flights with that motor at two to three times the rated watts-in before it quit.  The controler has over a hundred flights on it and is still going.  Twelve hours of aeromodeling the airframe and,  trying too cheap motors,  and too heavy,  I never made a worthwhile flight with that airframe.

Slow and medium speed (i.e. anything much slower then a pylon racer) dynamic flight airplanes don’t need all that fast a response from the servos,  these slow butterfly like flat plate airplanes DO.  Unless you are flying a flexible floater (Easy Star for example) all airplanes benefit from servos that repeatable go to the commanded position.  Servos that hunt for position and have double neutrals can make even an inexpensive airplane hard to fly.  I spent three quarters of an hour opening one of the cheap servos to repair a poorly done,  failed,  solder joint.  Rotation on moving the transmitter stick is jerky,  they hunt a little for position,  everything on them is cheap,  even the case is distorting as it ages as is the potentiometer which is evidently corroding since after sitting for a year they hunted for center.  But,  I have three of them,  they fit.  One has done fine service in a Depron/fiberglass Pilatus Porter for (25) flights as the rudder servo.

There is an issue here of reliability.  A $4- servo looks just like a $11- servo,  even if you open up the cover and look inside.  It’s about materials,  manufacturing controllability and durability.  That $4- servo has the cheapest of everything,  to disguise that they even made an apparent copy of decent stuff.  And some of them DO work,  at least at first.  But other then maybe one of two aileron servos being able to fail without ruining an airplane,  do you really want to save $(11-4)X3 =$21- that bad?  I’ve had servos that,  the same as this one look just like HiTeck HS-55s,  that were so cheap that the teeth of the output shaft wore off in two hours.

Things like the outer wings where the reinforcement rods don’t extend to having a slight twist I can easily deal with.  If the airframe is otherwise fun,  there are other motors.  Scorpions or NeuMotors are good choices.  Just don’t waste 20% of it on controllers set for a fixed (5) degree lead.

I haven’t like Dymond products since a bargain Euro25/$37 (80) gram motor that vibrated bad came apart in the air,  to not only crash the airplane,  it ruined a $90- motor controller and ten bucks worth of prop and carrier.  The couple of used motors bought for parts were new junk.  This one,  with minimal run time,  (with inexpensive magnets,  it flips through with no resistance) already has lousy bearings.  Hey,  if the price,  RPM,  and expectations,  are low enough…

Using the supplied new,  no brand name on it,  9X4,7 slow flier prop on 3S it pulls (8) amps at (11) volts for (88) watts-in or maxed out.  After replacing the “O” ring it just flew a Fun Jet Lite a.k.a. Zorg.  Not only was the thrust on the minimal,  that prop at the speed that motor turned it on 3S was too low.  It did a little better on 4S,  it wasn’t run but a couple of flights in a different airplane on (14) volts,  at least at that power level the cheap motor controler worked.  With the bearings already new junk,  why make a p.o.s. even worse…

I’m undecided what to do with the motor controller.  At (18) amps it’s big for this application,  cheap,  but at least it can go to 4S LiPos.  But,  if it has any adjustments for timing,  which is really important for outrunner motors,  that isn’t mentioned in the Dymond ’s specifications although neither are any of the common stick settings.  This is clearly an outdoor airplane,  maybe the few extra grams don’t matter.  I ought to sell the motor to somebody I’m not going to ever meet again.  Since using the acquired motor at all requires 3S LiPos,  and all of my batteries in 3S have Deans connectors,  I pulled the up to (10) amp slow flier connector to be replace it with a Deans.  That couple of grams weight increase is important for a (120) gram indoor slowflier,  but not this one.

Less Propulsion,  the airframe weighs (245) grams,  the motor/prop/controller weighs (71) grams,  the available 3S 1100 mAh batteries (90) grams verses the original 3S 1000 LiPos at,  with the lighter connectors,   probably (80) grams.  Add five or ten grams for the receiver,  total,   ready for flight weight should be about (445) grams.   But,  I had to add some tape at the hinges and half round carbon fiber stock at Euro7/$10- to the lower wing’s leading edge to straighten and strengthen it ya know.

Despite reconfiguring some of the NeuMotors 3S 1100 mAh (90) gram batteries I bought back in February 2011 to 4 and 5S,  I still have three at 3S.  Slightly bigger then the 1000s the plane was fitted with,  clearancing the mounting hole is an act of a couple minutes with a razor knife.  I’m going to guess that the balance was alright the way it was as the servo holes were pre-cut,  the replacements weigh,  at (8) grams,  the same as the originals.

Flights 4 and 5  Under Igstadt the last Friday of January 2012 
Just above freezing,  not much wind,  all by myself.  If flew with the (35) gram Jamara/prop saver/Graupner fixed 6X3 propeller on 2S 500 mAh at 15 amps,  but only barely.

Flight 6  Under Igstadt the last Saturday of January 2012  After just a few seconds of flight,  the prop saver and prop flew off.  Twice for half an hour we searched for it in the muddy field,  no luck.  Igit,  that was a part that came with the airplane I really wanted to reuse!

Flights 7 through 10  Under Igstadt the Last Sunday of January 2012  It just sort of flew,  barely above stall speed,  for two flights.  Martin just did some worthwhile flights with a Multiplex Park Master,  this thing is just barely in flight.  A 3S 1300 mAh battery was attempted.  After a four meter take off roll the motor mount plate tore lose ruining the prop.

Using a collet a Graupner “inexpensive” 6X3 left over from a Rookie was mounted.

Flights 11 and 12  Wiesbaden Waldacker  03 February 2012 (Fr.)
We’ve had clear sunny skies with a slight wind out of the north east for a week now.  But that brought unusually cold air with it (tens Fahrenheit at night,  twenties during the day),  the van wouldn’t start at all.  The first flight with a 2S 500 mAh battery sort of went ok,  for this airplane.  The landing was a flop onto the cut short frozen grass.  A second flight using a 3S 1100 mAh battery went a little different,  the landing was another flop.  The fuselage was torn at the middle of the bottom wing.  In the twenty minutes outside my hands had gotten so cold they hurt.

A paid used Euro2/$3-  “doorbell” motor with a 3mm shaft was mounted.  On 2S 500 mAh with an 8X3.8 slow-flier APC prop in the basement it drew (9.5) peak amps.

On examination the nose had come off to be repaired by the previous owner,  it was repaired again.  Fiberglass with hardwood flooring paint was used all over the nose.

Although it could be repaired,  again,  not a single flight with this thing has been successful.  My friends Park Master and Event 3D fly so well that I see no justification to continue with this Pitts,  it was cut up for parts.