Category: Product Commentary

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Re-Programming the AR636a in the E-Flite Timber (Part II)

Part I of this post is here.

When I reconfigured my Spektrum AR636A and reloaded code to make it into (essentially) a standard AR636 receiver and used it as a non-AS3X model by setting all the gains to zero… all was well.  But when I then decided to add back in some AS3X functionality in certain flight modes I overlooked one important plot point.  Luckily while reading some forum posts on the subject of the Timber in general one comment about reversing the servo direction got me thinking.  So I ran up to the shop and checked and guess what?  My elevator and aileron were responding exactly the opposite of what I would want when I tested the AS3X reaction to uncommanded roll and pitch movements!!  This could have been disastrous had I flown in this mode.

Here’s the problem.  When I went back to what I’m calling “standard” receiver mode with no gains so no AS3X functionality at all, I decided to treat this just like every other receiver.  I relied on my transmitter to make all servo adjustments including centering, movement direction and speed, expo etc…. That’s great in standard mode.  The problem comes when I decided to re-institute a switchable AS3X mode.  With the servos all set to standard (not reversed) and the servos reversed as needed (Aileron and Elevator) in the transmitter the stick command work fine.  But, when the AS3X is on and sees an un-commanded pitch change it command the elevator in the opposite direction.  Unfortunately since it does not know the transmitter is acting in reverse it command what it thinks is the opposite direction from the pitch but (the way these servos are connected and linkage attached) is simply more of the same!!  This would result in a sudden increase in whatever uncommanded pitch occurred.  I’m guessing the plane would try to loop… continuously.  For the ailerons a constant roll would likely have occurred and in my case both would have happened and things might have gotten ugly from there.  Of course I could have overridden those command but as soon as I neutralized the sticks it would have just reoccurred and we would have been off to the races again.

Honestly my only shot to control the plane might have been if I could have reached the switch to shut off the AS3X function in time.  Since this likely would have occurred quickly after launch… I imagine there would have been some unscheduled contact with the earth and a lot of cursing and gnashing of teeth!

Lucky for me I have been reading a lot of posts and so this came to mind before an ugly incident forced me to learn the hard way!  So lessons… 

  1.  When working with the AS3X receivers, servo reversing is best done “on board”
  2. Make sure you have a known good working flight mode to use when changing these things.  Take off in that mode and test up high in the air so you have time to switch back to the known good mode if anything seems amiss.
  3. Don’t trust anything you read or are told if the person telling you has not flight tested his tweek/update or whatever!

OK, so quit wasting your time reading on line and go fly!!  ðŸ™‚

 

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Re-Programming the AR636a in the E-Flite Timber

Please read Part II (located here) when finished with this post… it has vital information if you are reprogramming as I did!

After a dozen or so flights on the Timber I started thinking it was time to either replace the receiver with a non-SAFE/AS3X model or find a way to disable the SAFE mode (which I will never use) and be able to at least switch off the AS3X mode.  There is a fair amount of contradictory information out there and apparently there is no reliable way to tell which AR636A can be adjusted and to what extent.  Some, you can adjust the rate gain and priority but not the heading (this seemed to be the case on the Timber) while others apparently are locked down.  It wasn’t clear to me if I could setup the receiver from the Timber to keep the safe switch selectable as well as have multiple AS3X settings or not…  

I did find one place saying you could “upgrade” the code on some of these receivers and basically bring the receiver back to standard AR636 functionality.  Of course there are all sorts of warning that you are on your own if something goes wrong.  Since I’ve got a new receiver sitting on the bench ready for install… I decided to take the shot.

So I went into the Spektrum web site and registered my AR636 so I could download the code.  When the site took the serial number successfully I was heartened that just maybe this would work.  After viewing a few videos about how to program the receiver I decided to just go forward with sending the code and see what happened.  The software recognized the 636 SAFE receiver and allowed me to download the code.  To do this using a PC you will need the USB cable.

Here’s a link in case you decide you need one of these.

I immediately went in and changed a few settings and quickly thereafter the SAFE mode was lost for good!  No big loss for me… would be nice to be able to reactivate that somehow just in case I wanted to sell this plane but it seems unlikely I would do that… it will likely crash or be cannibalized at some future point.  Hopefully thousands of flights from now.

I now have all the settings set to zero gain for all three (switch selectable) modes… as well as taking away a couple servo reversing settings.   So I have effectively converted the the 636a to a dumb standard receiver!  Well actually it seems to be equivalent to a 636 now with expo, channel assignment and reversing and all the “gyro” settings available.  I can see where this would be really nice for someone with an inexpensive radio that didn’t have all the expo, assignment etc… already available.  For now I’ll just use it as a standard receiver and be happy with that.  Looking forward to flying the Timber without the stabilization to see how it goes.  Will be nice to see what the air frame and my skills can do without any help from the receiver.

Eventually I may re-institute some of the stabilization settings on a switch in case I want to do some “poor condition” flying and need a safety net or perhaps if some other folks want to get a flight or two in on a stabilized aircraft.  I kept an export of the original settings so hopefully, I can go back and re-import the original settings if I want to.

Looking forward to getting a flight or two on it soon to test it out.

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E-Flite Timber

While most of my money and efforts have lately gone into a large electric Aerobat, I still love to have some simple, easy and fun to fly aircraft in the hangar as well for those times when time is limited or perhaps the trailer isn’t making the trip… something I can easily throw in car with a hand full of batteries and go fly for just an hour or two that is fun to fly and easy to transport as well as being economical.

After seeing a couple of Timbers showing up at the field and being forced to fly them a couple times I thought it might be time to expand my fleet in this area.  The floats being included and the ability to fly using the most common battery I have (2100-2700 3S lipo) combined with a reasonable price made it even more tempting.  My original T28 is my go to in this area but while it is a great flyer, STOL and rough field handling are not among its virtues.

I initially went looking for the PNP as I’m not typically a big fan of AS3X (or gyros of any sort) in a plane that is already large enough and stable enough to handle most conditions with only modest input from the pilot, but my local shop had a BNF at the price of the PNP and no BNF models in stock so I picked it up.  Here’s a link in case you need one!

My first thought was to simply pull the receiver and drop in a non AS3X model before I even put a battery in the thing, however that plan was foiled when I picked up the wrong receiver at the hobby store so I decided to leave it be for now.  In fact, what I did was to go out on my first flights with a completely stock setup.  Since I have a DX18, I followed the instructions in the manual for the switchable SAFE select mode and the only other option I chose was to NOT install the slats at this point.  With those choices made, my first trip to the field was destined to be purely stock.

Before I get to the flying, let me talk about fit and finish, ease of assembly, etc…  First, the Timber is NOT a scale plane… there is no full scale version of this plane.  It is designed from the start as purely an RC craft so there is no comparison to how it looks versus the “real” plane.  This is as real as it gets!  So best comparisons are to other foamy type airplanes.  So here is the good and the bad for the model I got.

First, the edges of the plane in many places had what I would call “excess foam”.  Ever overfill the waffle iron?  Then you know what I’m talking about.  Glue also appeared in some places beyond where you would want it and I saw a few spots where there didn’t appear to be any that I would have thought would have had it…  On the aircraft itself, there were quite a few dings, dents and scratches.  None very bad, no crushing or gouges that were worth worrying about in my book at least.  Not the prettiest finish, but nothing that would affect flight.  Unfortunately, the floats didn’t fare as well.  One of the floats had a spot where it had been crushed with the tape that was wrapped around the packing that contained it and the whole aft end of the float is warped downward 10-15 degrees from that point back!  It looks like they were maybe wrapped while the foam was still warm and pliable??  That float is back at the hobby shop awaiting replacement.

All of this is disappointing as it just seems to indicate either a lack of concern or effort on the assembly line and a lack of quality control… or perhaps its just not something the Horizon team cares about.  Yes, I know it’s only a ~$250 plane… made of foam… etc… etc… but I’m a believer that you just don’t do things half way or with lower quality when doing it right just isn’t that hard…  I’m not even sure it would really cost much either.  There are other products from E-Flite that exhibit NONE of these issues out of the box.  Why not this one?  Again, I am talking fit and finish here.  Other than the float damage, none of this is worrisome when it comes to flight.

I went through the manual and easily programmed my DX18 with the recommended settings and everything worked as advertised.  All I added was the use of the throttle cut, assigned to my usual switch and that part was all ready.

The one issue I found that did concern me as far as flying and staying together was the way the motor felt and sounded out of the box.  When I turned the prop, it felt and sounded like there was something dragging occasionally or a bearing with a high spot or ????  I took the nose apart, removed the motor, examined it, blew some air through it, etc… Found nothing.  From here on, I’m counting on Horizon’s great service if something untoward occurs.  On to flying…

For a maiden flight, the day was… pretty much crap!  The wind was somewhat across the runway (not down it as we all hope for) and was a solid 10-15 with gusts to 20, maybe 25.  I stalled, did some battery charging etc… and then when the wind appeared to be  dropping a bit, I went out and took her up.

For the first flight I kept the plane in the full SAFE mode and it handled the wind phenomenally well.  I have to say it was fun and I forgot about the fit and finish issues and even that I was in safe mode for a minute or two… until I tried to pull a loop… tried again… Ahh!!!  SAFE mode!  SAFE from fun for me… 🙂

It appeared anything beyond about 60-75 degrees of aileron bank or more than “almost” vertical  in pitch are prohibited by the SAFE system.  That’s not a terrible thing… probably very helpful for a new pilot and much better than some of the settings I’ve seen on previous aircraft that were so limited they seemed almost uncontrollable due to lack of authority on the surfaces!  Some are so limited that they are hard to fly in any wind as they take forever to turn due to lack of available throw.  Not so the Timber.  It was still very controllable and with the added stabilization it handled the wind very well.

I quickly found the SAFE switch and shut that off and was now very able to maneuver the Timber and do all sorts of rolls, loops etc… some wind gusts aided in some new “unnamed” maneuvers… par for the course with this kind of gusty conditions, but recovery was quick and easy… .

I even added SAFE back in for the first landing and it was remarkably smooth considering the breezy conditions.  I’m not a big proponent of using this type of aid on a regular basis but I’m OK with it if it allows a pilot to get in the air and back down again (you can always turn it off when that nasty, hard ground is far enough below) as nothing beats actual stick time to make you a better pilot.  Once you can do good landings with SAFE, I’d encourage switching it off and preceding to do these landings with only AS3X enabled.  Continue the progression and eventually you can do the same things with no aid at all.  Then you are really flying.  It doesn’t hurt to have some level of safety blanket, as long as you don’t allow it to impede your progress.  That’s assuming you want to progress to completely controlling your Timber or controlling other aircraft that may not have these abilities.

Over the next week I was able to get out on two more occasions.  Both times were the last few hours of daylight and both involved quite a bit of wind.  I’m mostly flown with SAFE off but the AS3X still at factory settings.  I must say the little Timber is a very capable STOL aircraft and I have spent most of my time during each flight (usually 5 minutes on a 2200mah and 7 with a 2700) over the course of probably 15 flights, doing lots of touch and go’s, landings and takeoffs with all combination of flap settings and wind conditions.  I have thoroughly enjoyed flying this little plane.  I’ve also managed extended flight while inverted, stall turns, loops, rolls, teardrops, immelmans, split S, etc…

Here she is while still stock right before it got to dark to fly at all… about 9:30PM in mid-June in Indiana.

As you can see, those lights are quite bright and they gave me confidence to fly for 30 minutes or so each evening when I would have never put anything else in the air!  Love the light package… it really adds a dimension to flying the Timber that wasn’t available with my other aircraft.

I noticed after 10 flights or so… hadn’t checked earlier… that my motor has apparently smoothed out.  No grinding or catches when it runs now.  Hope that means I will escape any motor problems.

Next, I intend to see about reprogramming the AR636A so I can fly the Timber without stabilization.  My flying buddy Gary has one with a standard non-AS3X receiver and it seems to fly well so I’m anxious to see how much of what I’ve experienced is basic air frame design and how much is the AS3X system helping out.  In other planes I’ve flown with AS3X, it always seems to me that there is something a little odd about how they fly.  To locked in or a bit “stiff” feeling like the plane is just not quite making the mistakes I normally expect to see when I fly!  So far the Timber hasn’t left that impression but I want to honestly fly the bird and see what it’s like.  There is a bit of contradictory information out there about whether it is possible to reprogram a 636a or not.  If not, it may be time to move to a non-AS3X receiver.  I don’t expect that stabilization is probably necessary for this craft to fly well, so looking forward to that.

Also looking for a way to make the slats a quick install/remove.  I have not used them at all yet, but I’d like to try without a permanent installation.  I have an idea for stiffening and using some magnets…  more to come.

Finally, I will likely soon do some adjustments to the control surface throws, similar to what I’ve done on others like my ParkZone T-28… which is to say maximum available throws without modifying anything and adding expo to keep things smooth.  I especially would like to have more rudder as knife edge flight is pretty sad at this point.

All in all, so far the Timber is a nice flying, if not highest build quality, aircraft.  I’m looking forward to many more fun evenings in the twilight!  Time to try to make a few adjustments and see how it works.

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Extreme Flight Laser 200 – First flights and Telemetry reports from the speed controller

Saturday was my first 2 flights on the new Extreme Flight Laser 200.  It’s not even quite “finished” but I deemed if safe to fly and took it out for the clubs “Electric Only Fly”.

All I can say is WOW!  The plane flew very well with perhaps 2 clicks of aileron trim and nothing else…  I need to experiment with balance as I think I had the batteries a bit to far forward as the nose wanted to fall  during inverted flight or inverted 45 degree up lines… but otherwise the Laser drew a line just like it’s namesake.  It also flew light while still handling a bit of wind without issues. The smooth power from the 35cc Xpwr/Castle 120HV and 12S 4500 45C Pulse battery setup was awesome to behold.  Using a Xoar 20×10 for these first flights and the prop noise is minimal.  I love being able to hear that and the air over the air frame instead of the din of a gas motor.

The 4500mah Pulse batteries seem to be able to give me about 7 minutes of mixed IMAC style flying and time to land with 35% or so of capacity left over… which is sufficient though I might wish for a tad more flight time.  I’m thinking of moving to 5000s as the plane only weighs 11lbs 4oz +/- so I think an extra 4-6oz of battery pack wouldn’t make a big difference.

A new item of note that I am running in this bird is the Castle Creations Telemetry Link for Xbus.  Here’s a link if you have to have one after reading this:

This nifty gadget feeds back information like the current draw, voltage, watts, RPM and FET temperature based on information directly from the speed controller.  Getting all this information from a standard Spektrum telemetry setup required a lot more work and several sensors that cost a lot more than this module.  Based on the information it provided I was able to get pretty graphs like this out of my telemetry viewing program on my PC:

Some interesting information can be had by examining this data closely… for instance at on peak point during the flight, the motor was pulling around 86 Amps!  This was at a point just a minute or two before landing and this caused the battery to sag to about 40.5 Volts.  At this point the prop was turning slightly above 11,300 rpm!  At another point after some sustained mid-throttle flight, the FET on the speed controller reached 145 degrees Fahrenheit.  The reported max power was just over 3600 watts!  For this light an aircraft that is almost insane… which is fine with me!  I’m not in full throttle very often and certainly won’t need to be with this bird.  To quote an old friend “To much power is almost enough.”

The FET temp reading tells me that the 20×10 Xoar is not over stressing the electrical system when flown in this manner though the RPMs seem a bit high so perhaps the 21×10 or 22×8 that I have may be more suitable.  It will be fascinating to run those and get some comparison data.  This kind of data is priceless when you consider it is going to allow me to choose a propeller that maximizes speed or torque or battery life as I see fit and to insure that I’m keeping the power system in a “happy place” while doing so.  Not having to worry about the health of that system is going to keep money in my pocket (not buying more components to replace the burnt out ones!) and give me one less thing to be concerned about.  That makes me happy.

I will update some more and do some comparisons as I try out more/different prop choices.  I’m really hoping the 22×8 works well as I’m thinking that it will give me more low end pull and less speed overall (which is fine with me) while giving me a bit more down line braking effect…  time will tell.

So far, I’m loving the information this little module provides.

I’m also using the arming lockout key from Castle.  This little gadget signals the speed controller to enter the lockout state whenever the key is inserted into the socket.  It’s another layer of security for the very powerful motor and attached prop.  Between this and the throttle cut I have programmed into my transmitter, I feel much more safe plugging in the two 6S packs!  This system is nearing the 5HP level and spinning a 20 inch prop at 11000 plus RPM.  What that can do to unprotected hands, arms, legs, etc… is worth considering.  An extra measure of safety is always welcome.

 

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Extreme Flight 74″ Laser – Build nearly complete

The Extrem Flight Laser has been in the shop now for about a month and I’m finally getting close to flying status!  My final items to complete are to get the speed controller and receiver installed, do the radio setup and then go back through and do final checks on bolt tightening, gluing any joints that need it and seal all the hinge gaps.

Overall, the instructions and included hardware seem to be good quality and short of flying it, I am pretty happy with it so far.  I’m going to get a bit nit picky over the next couple of paragraphs in hopes that this will help anyone else who is working on putting together.  There are a few shortcomings in the instructions worth noting and a couple tips I can pass on as far as what to do (or not) that may prove useful.   So here is my summary of the good, the bad and the ugly of building this ARF.

First off, when installing the control horns you need to remove some covering in order to get a good glue bond.  The instructions for this are pretty good but I would recommend a couple of ways to make this easier.  First, when drawing around the control horn base in order to know where to cut, I suggest a white board marker.  They are easier to wipe off with just some alcohol or window cleaner.  Also when removing the covering I remove only to just inside the line so that the base plate actually slightly covers the edge of the material.  This helps ensure that the material will never peal up around the horn and the result looks very professional.  Secondly, not only here but pretty much anywhere you need to remove covering… I highly recommend use of a soldering iron.  With minimal practice you can move at a rate that doesn’t char the wood underneath but just melts the covering.  It also seals down the edge as you go.  I find this method far superior to use of a razor blade or Xacto knife.  Extreme Flight’s manual mentions this option in one place but then often says to use a blade in many others.  I’d stick with the Soldering iron in pretty much all cases.

While on the subject of control horns, for some reason I got two sets of of rudder horns with no explanation as to why or what I might want them for… still don’t know.  In any case, I would install these dry and mark them once you measure for proper centering.  The “barb” on one side that I thought would end up against one side of the rudder to aid in alignment… does not seem to be any such thing and I don’t know why it is even there…  Just be cautious that you get the centering correct here.

One preference/ nitpick of mine is the tail gear mounting method.  I’m used to having blind nuts embedded but this gear mounts only with wood screws.  I would love to have the blind nuts as I think they result in a stronger mount.  Hopefully this mounting method will be strong enough.

The next note I made while building was regarding the rudder pull-pull mechanism.  First, if you have never put one of these together before you should go find a step by step instruction set that will walk you through everything you need to know ’cause what is in the manual for the Laser is not that!  If you’ve done a couple you probably will have no issue with this one.  One odd note is that they specify to crimp the aluminum tube with side cutters???  If your side cutters are worth a darn and you squeeze firmly you will end up cutting that tube and probably the cables themselves clean through.  A standard pair of pliers works quite well, thank you.  Don’t use side cutters!

Next, I noted that the instructions for installing the wheel pants had a couple of shortcomings.  First, when they have you drill a hole, they do not tell you what size hole… you can figure it out of course but it would be nice if they just told you… sorry I didn’t write it down or I would have provided that here (silly me).  Also when they have you install the blind nuts it required an excessive amount of force to get the little sharp prongs to push into the wood because the back of the wood inside the wheel pant has a fairly heavy coating of fiberglass/resin which necessitated a pair of channel locks to get the prongs to penetrate!  I felt like I was risking a good amount of damage when I did this but that is what it took to get them to embed flat…  and you need it to lay flat to keep it from rubbing against the rim/tire.

One error I ran into as I mounted the motor is the stated distance from the front face of the motor box to drive washer should be 6-3/8″… My ruler says it is actually 5-3/8″!  If you extend it to 6-3/8″ the cowl will not go back far enough to mount.  Luckily, I checked before I got things mounted.

OK, that’s about it.  Everything else seemed straight forward to me and I appreciated the packaging of the parts (individual bags with labels for each set of pieces).

I’m looking forward to getting started flying soon and the real test will be flying characteristics and how well she holds up over time.  Looking forward to messing with setups, props, batteries and telemetry to see what works best.

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Motion RC P-38 first flights… and the resulting damage!

A few days ago, the two P-38s finally got to go visit the field.  The last couple adjustments that were needed seemed to be finished up and there was nothing left but to fly them!  Several club members gathered to watch the inaugural flights.

My green P-38 with the addition of invasion striped on the wings was first to go.  I had 2x3300mah batteries on board pushed all the way back as a best guess center of gravity.  The final run up up of each individual motor/speed controller was accomplished in the pit area just before taxi out for take off.  I must say the wire connections to each wing are somewhat tedious.  There is not much extra wire to make connections and my hands are not very small.  Also the lighting connectors are NOT polarized plugs so you also have to be very cautious of plugging those in with the proper polarity.    Then the tedious stuffing of the wires into the small opening (individually… there isn’t room to do them all at once) while simultaneously sliding the wing panel onto the body.  As I said, tedious.  Of course you have to do this upside down and I was trying to be very careful not to put any pressure on the canopy (removed that) or the props (suspended off the edge of the table).

 

Finally, all assembled and I immediately noticed that it was a bit difficult to turn left on the ground… I suspect the cross wind from the right hitting those two big verticals is responsible for that!  But she lifted off pretty quickly.  I had to do quite a bit of aileron trim to keep it level and some elevator trim to keep the nose up.  I’m betting the aileron trim is a result of the inboard wing edge that is warped downward on the one side.  Finally, all level and flying smoothly I started to pull a loop but decide not to since it appeared that my elevator travel was a bit low and there was not a blazing amount of spare power either.  No big deal, I’d been flying for a few minutes so I might have been getting some sag from the batteries by then, so I just decided to get back on the ground.  First pass I came in without flaps and it was sinking awfully quick while still flying pretty fast so I went around and dropped half flaps and tried again.  My guess for elevator mix must have been about right and I came in a bit slower but still with a pretty fast sink rate…  That made for a moderate “hop” and then too much speed as I ran off our Geotex into the grass at a good clip.  That arrested the speed within another 15 feet or so but as it did so, one of the mains folded up!!  That was very disappointing as I really thought it wasn’t a terrible landing for the first attempt.

Here’s the retract with a bit of foam still attached… but not much.

And here’s the foam socket with (apparently) very little glue.

Further inspection showed that the gear mount had separated from the foam from (in my opinion) a notable lack of glue…  There didn’t seem to be any other damage but I was obviously done for the day.  I try to minimize repairs at the field, generally opting for moving on to another plane if the program is just casual flying so I went back to help Kelly work on his P-38.  Another impression I had after the flight was that the plane flew somewhat “heavy”… i.e. it flew like a warbird.  I was hoping for a bit more of a “foamy” feel to the plane but it was not totally unexpected with the modest wing area compared to the weight of this airplane.  I had read where some folks talked about it flying fairly light on the wing and coming in slow but that was NOT my experience.  Those guys must be hard core warbird flyers who are accustomed to the heavy wing loading of that type of plane.  For me, it seemed heavy but I don’t think I’d want to fly much less battery capacity as flights would get very short I would think.  Based on just this flight, I don’t think my 3300s will get me much more than 6 minutes, but I’ll have to fly a few more to be sure.  I wasn’t paying strict attention to that with all the other maiden flight checks and nerves going on.  Finally, the P-38 does not like to turn with just aileron.  It needs either some rudder mix or at least a pilot with a left thumb that doesn’t fall asleep from lack of use once airborne!  I fly a few other planes that like rudder in a turn (a Carbon-Z Cub, a Telemaster) so I adapted to that fairly quickly, though it will take a bit of flying to get just the right feel for it.

Moving on to Kelly’s P-38 in “Pacific Silver” we went through the same preparations and then he was off the deck.  In short order he was having problems getting the plane to turn and there were a couple times when it looked like he might not be able to control it to get it back down safely.  Finally, he was able to herd it onto the Geotex with a fairly fast but mild landing.  He too ran off into the grass and immediately one of his main retracts folded as well!  This aircraft definitely isn’t built for any but the smoothest runways!

Later inspection showed his retract to have a pitiful amount of glue as well, so apparently I didn’t just get the one built on a Friday!  Between the battle to keep the plane airborne… it seemed to be constantly yawing to one side… and the retract issue, Kelly was very disappointed with this aircraft.  He was running a single 5300mah battery and it certainly appeared that his airplane flew similarly to mine as far as landing speed and overall handling even with the somewhat lighter pack.

I am working to replace the retracts in both planes with a bit more generous portion of Foam-Tac and hoping we can keep those in place.  We are extending the Geotex runway soon at our club field so hopefully we won’t run off quite so easily anyway but it is disappointing that these are so fragile.

I have a theory on why Kelly’s plane seemed to have a serious yaw issue… more on that after some investigation.  So far, neither of us is particularly fond of the P-38s.  Hopefully we can work out the wrinkles and get in some more satisfying flights soon.

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Graupner MZ-24 Radio — What???

My flying buddy Kelly, who I’m pretty sure considers me his personal “RC Aircraft Mechanic and Radio Setup Technician”… decided some time ago that he wanted to get a new radio system for his RC needs.  I know he has had good experiences with his Graupner charger and is a big fan of German engineering in general and so had high hopes when he ordered his new radio system.  He even talked to me first to insure that I was up for learning a new system and I said yes….

I have programmed many RC radio systems over the past 15 years or so. Airtronics RD6000, RD8000, Hitec Prism 7, Futaba 9CAP, Multiplex EVO 9, JR9303 and Spektrum DX8 and DX18 are all transmitters that I’ve spent time programming.  I’ve spent significant time and effort setting up multiple aircraft from trainers to multi-engines and delta wings to 3D aerobats on these radios and now I can add the Graupner MZ-24 to that list… or at least I’m trying!

Some random thoughts on my experience so far.

The MZ-24 is NOT a 24 channel radio.  For EVERY other radio in my list above you could probably correctly guess the number of channels by picking out the number in the radio name… but not the Graupner.  For some reason the number of channels you can control is 12… you can now decode that the MZ-18 is a 9 channel system, maybe?.  Kelly wasn’t fooled… he’s definitely a guy to research his purchases but I was fooled for a minute or two.

What Kelly thought was a German radio was apparently designed and built in South Korea?  Now that’s not a bad thing in my book… I’m pretty sure that more than half of the electronics in my home were designed and built there and I wouldn’t keep buying them if I didn’t think they were great products….but this radio…. maybe not my favorite effort from our friends in South Korea.

Setting up the flap system on this radio has been a multi-week odyssey which has ended in…. success… but only after completely abandoning the built in flap system functionality!  Apparently, setting up the flap system to do a simple 3 position flap setting with elevator mix is completely beyond my ability using this radio if I try to use the built in flap system.  Even after a few exchanges on the phone and via email with Graupner support I could not reliably make the flaps worked as I wished.  Setting the end points of the flap function is apparently impossible, and simple reversing of the function and strange things like changes in speed through the travel of the flaps are a couple of the  challenges I faced when trying to use the flap system.  Take my advice and just leave that function alone.  Just assign the channel, set the endpoints and sub-trim to establish the motion you want.  Slow the servo with the servo speed function and then build your own mix for elevator or whatever else you need.

Programming the telemetry system on this radio is… just odd.  While most other functions are configured in a somewhat intuitive method… when you get into the telemetry system you are confronted with screens of text that look like they are something from a 1970s computer application… i.e. from the days when computers didn’t yet have a mouse attached or a graphical interface.  Gone are all the pretty colors, graphs and symbols.  Absent are any understandable directions… at least for the simple voltage monitor we wanted to use.  Even the list of “alarms” are just labeled with numbers.  What each number represents is cataloged where?  Imagine how easy it could be to program a telemetry system if you a full touch screen color screen with audio prompts available…  Oh, that describes the Graupner radio!!  Unfortunately what we get is text only…  Did the graphical interface team all quit mid-project?

The range of receivers available, reasonable pricing as I recall and apparently solid build quality… even the various ports and options available… All would give the impression of a high quality, easy to use, good value, complete RC system.  To bad that it seems this product never got “finished”… or at least that is how it seems.

We are going to continue to work with this system and just see how it goes… at least until or unless we run into actual RF issues, which I don’t expect.  Here’s hoping Graupner does some more development and sorts out the oddities in the user interface.  The potential is certainly there.

For my part, I think I’ll stick with my Spektrum DX18.  I think both it and the DX9 are great radios that do about anything you’d want and who’s interface is far superior to the Graupner… even without a touch or color screen!

 

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Freewing 80mm Super Scorpion EDF Jet

Recently, My flying buddy Martin has decided to branch out into some ducted fan electric craft and one of his first is the Freewing  80m Super Scorpion from Motion RC.  Martin had the new aircraft shipped to my shop and today he came by and we did most of the assembly.  

The first observation I would make is that we spent about 4 hours today doing assembly and we got to the point where all we need to do is plug in the receiver and set the throws and it will be ready to roll.  Maybe we could have cut it back a bit but don’t believe the place on the website that says assembly time is 30 minutes!  Just scroll on down where it says 3 hours and you are in the ballpark.  The other specs listed on the site seem to be accurate, even down to the ready to fly weight.  Measured with a 4500 6S on board, we measured Martin’s aircraft as just a couple of ounces over 5 lbs just as the web site reports.

Similar to the manual for the P-38s that I recently got from Motion RC, there is a lot of “stuff” in this document that describes assembly that is already done out of the box.  This is distracting and it sometimes makes it hard to figure out what the next “required” step is in the assembly process.  Unlike the P-38 this model however does not have a full assembly video on the web site and luckily it isn’t needed as there just aren’t that many pieces and assembly is not all that complicated.  Just walk through the manual and keep skipping forward when you read the parts that are unneeded and you’ll have little trouble.

There are only a couple of places where I can give you some advice that might not be obvious. 

  • When you put the screws in to attach the wings to the body, be careful to route the wires appropriately then be very careful that the screws are actually going into the holes in the plastic.  The best way to avoid this is to just start each before you fully tighten any.  A simple thing, but easily overlooked.
  • When you attach the vertical fin, insert the front screw first but only a couple turns.  Then do the side screw and tighten both down before installing the screw from the top.  Otherwise it is very difficult to get the top screw to hit the pre-drilled hole in the wood plate that it attaches to.

And a critique or two for the manufacturer and distributor.

  • Somehow there were only 2 of the 2:1 servo connectors and 1 3:1 servo connector included in the kit, even though the manual clearly indicates there should be 3 of the 2:1 connectors.
  • On the website it is implied that you can remove the wings and elevators and the vertical stabs (presumably) in order to carry it to/from the flying field.  “Removable wings and vertical stabilizers for convenient transport”.  Perhaps this could be done a few times in order to ship the aircraft from place to place, but these self tapping screws and plastic and wood into which they are screwed are not what I would expect if this were actually the case.  I would expect most folks are only going to take these screws back out if a repair is needed.  Anyone who needs to take this aircraft apart in order to get it to and from their flying field should look for a better alternative.

Since the high today in our area was 38 degrees (about 20 degrees below my minimum standard for comfortable flying) we don’t yet know how it flies but here are some pictures of how it looks.  Some highlights I would point out are the nice shock absorbing struts, the cockpit detail and the attractive and hopefully easy to see color scheme.  Though the aircraft is not quite as large as Martin had assumed, I think he is still fairly happy with the overall look and build quality of the aircraft.

Here is the nose gear showing the nice shock absorbing strut

 

Here’s a shot of the actual functioning inlet that feeds air to the ducted fan

  

And the finished product.

Looking forward to see how it flies.

 

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Motion RC P-38 – outboard flap issue resolved

So, the silver P-38 sitting on my bench has one flap servo that appears to have the servo arm incorrectly installed.  See my previous post on this topic for details.  Motion RC P-38 – outboard flap issue

I was gathering the necessary tools to slice into the plane as described but decided to do a bit more research and found that others had pulled other servos out of the P-38 and reported that they were glued to the paint, not directly to the foam.  This gave me a bit more confidence that it would come out without tearing up the foam.

My first thought was that I would have glued the servo in directly to the foam…  which would have made this worse… so good thing no one asked me!  So with this new information I went back to the shop and made a careful incision all around the edges of the servo where any glue might be holding it and then with a pair of pliers I just grabbed on and started yanking and wiggling…

As advertised… the paint stuck to the glue and thus to the servo but the foam is largely undamaged.  With this I was easily able to then remove and replace the arm into the correct position and things then lined up nicely!!  Another hurdled cleared.  Glad I didn’t get in a rush about cutting into that wing!

We are now much closer to flight on these two birds and I’m starting to get back closer to the initial excitement to fly them that I had when we placed the order.  Just another session or two at the bench to get all the throws and rates set up and we should finally be in a flight worthy status… just in time to wait on the weather…

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Motion RC P-38 – outboard flap issue

My buddy Kelly decided to put his P-38 on his new Graupner MZ-24 radio.  This gave me the opportunity to play with his new radio which posed some challenges but I’ll save that story for another time.  The issues with programming the MZ-24 were eventually resolved but then another issue with the P-38 was found.

The P-38 has a control board that acts as a 4 to 1 connection for the 4 flap servos.  This means that all movements (including centering and trim) affect all flap servos equally.  Unfortunately, one of the outboard servos is not set for neutral at the same point as the others.  Here is a picture of the two outboard flaps with the servo arm at neutral…

Notice the control rod in the picture above lines up with the edge of the servo case protrusion.  In the picture below, it is entirely inside the case protrusion.  I.E. the servo arm on one is much closer to perpendicular to the wing than on the other.

Because of this, the corresponding position of the control surface is impossible to match up between the four surfaces involved.  I can match up either endpoint on this one flap by adjusting the linkage but the further you move from that position, the more magnified the discrepancy between this surface and the other three becomes.  It’s simply geometry.

Typically, the solution to this is to simply remove the servo arm and rotate it to a matching position to the other 3…. assuming this difference is “one tooth” which I’m hopeful is the case.  In this installation the problem is compounded as the servo is sitting flat in the surface of the wing with the arm retaining screw pointing toward the wingtip.  I understand this orientation is likely a necessity as the wings are not exceedingly thick so orienting the servo this way makes sense but to every design decision there is a trade off and this one results in severely limiting access to that screw.  An additional compounding factor is that the servo is glued in place which makes accessing this screw nearly impossible without some more drastic measures.  I know this is common practice in foam models but it is NOT a practice a can say I’m fond of and this is a perfect example of why.

I tried to pull the servo out, but the glue appears to be underneath the servo and I don’t think I can remove it without risking tearing a hole clear through the wing…  So the only approach I can come up with is to cut a triangular groove into the bottom of the wing so that I can get a screwdriver in there and remove the screw so that I can rotate the arm to the proper position.  I’ve been looking at it for days and have come up with no better ideas so soon I will start the necessary surgery and hope for the best.  If I can make the cut precisely and neatly enough with a sufficiently sharp blade, I’m hopeful it can be replaced with minimal structural or even cosmetic damage.

I guess I need not point out that better quality control could have avoided this issue and perhaps Motion RC would do something to take care of this issue if I called but honestly what could they do?  Sending a new wing is the only option that would do us any good and with the decals already in place that makes a bit more work and I am hoping this will end up being an easy fix.  I hope the hardest part will be stealing myself to cut into my flying buddy’s brand new airplane!  I’ll post further post-op.  Wish me luck.

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