Fully 3D Printed Airplane – Part 5: Pit accident, reprint and removable wing

Well “Wolf #2” fell prey to another pilot’s RC airplane that got away from its owner and chewed the tail off of my Wolf. 

So I immediately started planning for Wolf #3!

A couple things I learned from Wolf #2.

  1. One bit of fine print I had never noticed in my builds of Wolf 1 and 2 was the recommendation for differential aileron.  Rudder is often used to make up for adverse yaw but often the best solution (short of a different airfoil) is to implement differential aileron.    This lead me to the discovery that once implemented I no longer had the need for rudder to get turns absent the adverse yaw I had experienced in previous flights.  
  2. After flying with a 2200 3s and a 1350 3s, I soon realized the 1350 provided for better performance with more than adequate flight times.  I finally tested an even smaller battery pushed forward to maintain proper balance led to even better glide characteristics and less need to maintain speed.  I settled on an 850mah for adequate flight time combined with just enough weight to get a proper balance.

So with all that in mind, I decided I could afford to drop the rudder modifications.  Along with the lighter battery this meant I saved enough weight that I could make modifications to allow for a removable wing without worrying about making her to heavy.  I had found having the wing permanently attached made the Wolf unnecessarily difficult to transport and more easily damaged than necessary so I planned to remedy that.

In order to accomplish this I had to create some new strut attachment brackets and provide for some reinforcemment, both in the wing and where it mates to the top of the fuselage.to make me comfortable that the wing would stay attached., to be sure the wing would stay attached!  For the struts it was just a matter of creating some small blocks to attach to the body and wing with an inset to capture a nut.  That looks something like this.

Wing end

And fuselage end

Then I used the Cura Slicer program to add a support blocker to the part during the slicing process.  By doing this,  I could then add an ioption to modify the settings for the overlap that allows for adjusting the infill as well as the number of walls.  By doing this I was able to create areas in the wing and on the top several millimeters of the wing saddle area that are much more dense/strong.  This accomodates the threaded insert installation (melting those into the saddle area) as well as increased support for the bolt head and washer to hold the wing securely.

You can see the denser area as a darker triangle in the wing…

and on the top of the fuselage

The result of this is something a bit easier to transport

The sharp eyed may have noticed some color variations in the new version of the Wolf.  This was another option I went for when I had to reprint.  I am not a big fan of painting/sanding etc… so to make the airplane highly visible and keep from having to do any painting I printed with pause commands inserted at carefully calculated layer levels to allow me to change filament color and create the banding effect you see.

I have only had 3 or 4 flights on the latest iteration of this aircraft but so far it seems to be structurally sound and flies pretty well.  With it getting cold here in the mid-west part of the US, this one will be going on the shelf for a while but I’m looking forward to more time with it in the air this spring.

 

1.2M P47… The latest addition

E-Flite has been updating a number of their existing warbirds in this size class to include the latest round of upgraded electronics, including 3 and 4S capable power systems, upgraded digital servos and often a livery change and/or some tweeks in response to past user feedback.

It was inevitable that they would eventually get around to one that I could not resist and of course the the P47 is the one for me.  I consider it the ultimate WWII aircraft.  Showcasing all that allowed America to come out on top in that epic struggle, it was powerful, fast, tough and reliable, heavily armed and armored and we made a bunch of them!  (15,000+ I believe)  Many were assisted down the assembly line by my Grandfather in Evansville, Indiana!  How can I not love the Thunderbolt?

P-47 Razorback 1.2m BNF Basic with AS3X & SAFE Select

So, as soon as they started rolling out the newest version, I put one on order with my local hobby store.

After about 10 flights with mine.  Here is my list of what I really like and dislike about the new bird.

Good:

The new electronics are great.

Upgrading to a 4 cell power setup gives the bird the power it needs to perform like a warbird

The new SMART ESC and AS3X receiver allows for plenty of data to keep an eye on battery usage, temperature, etc… to insure she continues to fly well. 

The servo upgrades seem to work with precision and the plane just overall flys nicely as a result.

Weight.

The plane is actually pretty light, especially considering the available power, even when you load all the armarments on board.  It keeps the airplane relatively light on the wing which results in easier takeoffs and landings.

Livery.

I’m sure there are some who were hoping for somethin different but the Kansas Tornado is a reasonably easy to see and, at least to my eye, attractive scheme.

Prop.

It seems to be almost imposssible to fit a large enough 4 blade prop on a model P47 to look really scale but at least we got a 4 blade with a somewhat appropriate shape!

Bad:

Retracts.

I do not understand why E-Flite wouldn’t have put a few dollars into the retracts to give them working Oleo struts.  As light as the bird is, they would not have had to take much abuse but it sure would be nice to have something to take a little of the shock in the case of a poor landing.

Tires.

Combine the lack of functional struts with these rock hard tires and you have zero shock absorption in the landing gear.  Are decent foam tires with “any” give whatsoever so hard to source?  Add to that the pressed in diamond pattern on the tread which looks just silly…  OK, maybe I’m being overly dramatic, but it seems so easy to have done it right!

Prop.

While I like the general idea of a 4 blade and I get that properly sizing one for scale looks is difficult, I don’t trust any airplane where they claim you can run 3 or 4 cells without a prop change.  I mess with prop changes frequently on my aircraft to get the performance I want so I’m very aware that adding 33% more input voltage to the same prop means you have made huge sacrifices somewhere.  Likely its just a compromise that is mediocre for either.  It would have been nice to get 2 props with the aircraft… each actually matched to a 3S or 4S setup.  My observation so far is the prop is probably overloading the 4S setup a touch and pulling more current than it needs to and likely underloading the 3S setup and therefore not getting as much power out of the system as would be possible with a correctly sized unit.

Fuel Tank.

I like the removable rockets and bombs, but why is the centerline fuel tank fixed?  I took care of that issue, but my solution is a bit more permanent… involving some side cuts.  The plane flys even better without any of the extra drag and that is how I fly it most often.

Overall I am enjoying the P-47 very much and I am already keeping an eye out for some replacement struts and/or tires… even if I have to turn to my 3D printer to solve the latter.  She flys very nicely and with the AS3X in the background, is especially stable even with some adverse meteorological conditions.

I have been flying more and more on my 4S 2800 LiHV packs and with proper throttle management, nice 6 minute flights are the norm.  I’m just getting comfortable enough to be working on nice scale takeoff and landings as well as experimenting with making the manuevers more scale like as well.  She can certainly fly like a sport plane if desired so making scale manuevers is something you have to be intentional about.

As I get more flights on it and make any modifications, I’ll be back to report but overall I expect this bird will remain in my fleet for some time to come.

Fully 3D Printed Airplane – Part 4: Flying, Crashing and Rebirth

Well after a short 4 flights, the original 3D printed Wolf is no more….

RIP

For reasons unexplained (I have theories but no real proof of what caused it) the plane crashed and is no more.  Luckily most all of the non-printed parts are fine and ready to grace Wolf 2.

So flights 3 and 4 were both very nice until the fatal dive that ended flight 4.  The wolf has plenty of power with my current setup using my 3S 1300 batteries, was balanced nicely with proper battery placement, and tracked super.  Gliding was very limited, but I figured out that I didn’t have the speed controller set to brake, thus the folding prop didn’t and caused a lot of drag when the motor was shut down.  So problem fixed for Wolf 2!  Flaperons worked but more testing will be done on those and a rudder needs to be fitted.

After experimentation a bit with materials and printer settings I settled on constructing Wolf 2 with the following materials and modifications.

For the body I’m using Poly Light LW pre-foamed PLA in orange.  It is ~35% lighter than standard PLA but still heavier than the eSun foaming LW that my first Wolf was printed from.  It is easy to print as it uses settings akin to standard PLA but a bit stronger than the LW if both are done correctly.  I’m also using this for the control surface just because I want that same color there to give some contrast to the white that I’ll use for the wings proper.

For the wings, horizontal stabilizer and vertical fin I’m using Colorfab LW PLA.  This is very similar to the eSun I used for the first Wolf but it is much brighter white, which I prefer if I am not going to paint, which is the plan.

All parts that need to have more strength, I’ve used eSun PLA+ in either white or orange, which isn’t a terrible color match to the Poly Light.

Next I needed to do some CAD work to create a workable rudder.  Here are my diagrams to create the rudder versus the standard fixed vertical fin.  I cut apart the existing fin and added some bevels to create each new piece then added a simple control arm on the moveable part.

Fixed Fin

Moveable Rudder

My biggest issue with this was that the structure at the hinge point was, perhaps, going to end up being a little weak.  I think I need to improve these with some hinge pockets and reinforcing in that area but for Wolf 2 all I did was manipulate the vertical fin in the slicer program to do a fairly dense infill on the leading edge of the fixed fin.

I didn’t even do that on the rudder proper, instead opting for some Gorilla Glue that expands a bit as it dries to help the hinges grab to the inside of the rudder.  If I ever build another I’ll probably go steal the aileron hinge pocket design and put a couple of those in the rudder and fin rather than mess with filling that area.  Maybe with a small bit of bracing.

I also had to add a second servo holder in the body… easily done by just printing another servo mount and gluing to the wall under the cockpit area… and add a control rod tube extending back inside the body to the right point.  That took some measuring/CAD manipulation and just good old fashion TLAR (pronounced Teelar… That Looks About Right) to get the rod guide tube in place without causing any binding.

Printed parts soon began to fill the table

And before long I had this

Pretty much ready to fly…

And here’s my rudder… working well.

The next thing I decided is that if the prop folded it could conceivably catch on the square hatch latch that protrudes upward from the hatch cover.  If it did, the motor would not be able to start up again and could cause some issues.  Even if it didn’t catch a direct shot to the side of the latch could cause some problems so I designed this hatch latch cover and prop deflector.

Here it is glued to the latch.

If you do something like this make sure you only glue it to the latch and not the hatch or your hatch may no longer be removable!

After all this the aircraft seems to only weigh about 2 ounces heavier than Wolf 1 and I can now report that after 2 additional flights, Wolf flys really well.  With the folding prop working correctly and the use of rudder to make slow flat turns, glide capacity seems to be increased and with a few more flights and possibly trying some smaller batteries I’m hoping to catch enough of a thermal along the way to do more than just “slow the fall”!

I’ve thought about making a removable wing version of this but I don’t want to add the weight I think that would require with all the reinforcement and mounting hardware etc…  For now, as long as she behaves and I don’t do anything stupid I expect this one will transition from 3D printer experiment to just another member of the flying model fleet.  What more could you really want after all?

I’ve got a couple ideas for the next model I will print and a couple other ideas for smaller 3D printed RC aircraft related projects to get started on as well so hopefully more on this type of thing will show up here soon.

New Freewing JAS-39 Gripen… Good, but not my cup of tea.

I recently aquired a Freewing JAS-39 Gripen. 

Up until recently, I have never been particularly interested in flying EDF aircraft but with the latest updates in battery technology allowing for more and more energy per ounce of battery and the shift toward more and more of these type of aircraft being available in ARF or RTF foam bodied airplanes I have begun to consider having one or two in the fleet.  I did some research into available A10s and didn’t find one that really met my personal requirements.  Same for a couple other models.  In the end it came down to an impulse buy from another club member at a nearby swap meet.  He had an airplane that had always interested me and it was essentially new and at a good price.  Not least of all, there is going to be an EDF only event at the field this summer so I wanted to have something nice for the event!

As with most warbirds that I purchase, I did some research on both the real airplane and the model.  First, about the real airplane.

The Gripen is a swedish multi-role fighter that is largely considered to be one of the top two most capable fighters in the world (the late model F-16 is the other and they stack up very well against each other) if you exclude stealth aircraft.  By most accounts it is one of the best gen 4 jets ever built and it continues to be upgraded.  Its distinctive canard design and power to weight ratio make it a very capable dog fighter and the advanced electronics packages and flexibility of weapons payloads make it an extremely dangerous opponent in BVM (Beyond Visual Range) combat.  The F16 is also a very nimble and highly powered platform with similar capabilities… it just gets there by having more thrust to offset its heavier and larger chassis.

As far as the model goes, research says this airplane has a lot of capability depending on how you set it up and fly it.  There seem to be three common complaints from those who own the airplane.

  1.  It is rather large as compared to other aircraft running a similar power system which leads to complaints that this results in it being a bit heavy for this system and therefore not as high a thrust to weight ratio as some would like.
  2. Using the recommended battery size and capacity results in an aircraft that is nose heavy compared to the recommended, which results in an inability to perform certain manuevers.  A select few who seem to be well respected say even the recommended balance point leaves the plane significantly nose heavy.
  3. Using the recommended battery also results in short flight times… perhaps even compared to most EDFs which are somewhat notorious for short flight times to start with.

I’m not as concerned about the first issue as I haven’t done much EDF flying and am not all that fond of high speed so while I wouldn’t mind to have some extra punch available to me, I’m not looking for a lot more speed than is necessary to make the airplane fly well… and it seems to be capable enough by that measure.

Items 2 and 3 are somewhat of a concern and are of course intertwined.  In most electric aircraft, you have the option to add a bit of battery capacity if want to extend flight time, but with this airplane, adding a larger capacity and therefore heavier battery will just exacerbate the nose heavy condition as the battery is in front of the balance point and can not practically be moved rearward to compensate.  I don’t like extremely short flight times and I would like to explore some high alpha flight which requires a proper balance point to perform.  In addition, since the airplane is already a bit on the heavy end of things, I don’t really want to add dead weight to the tail to force the balance rearward.  There was no apparent solution…  Welcome to the world of EDFs and aircraft design I guess… Everything is a compromise.

Further research along with some fortuitous timing led me to what I hoped would be some improvements.  I won’t go into a lot of long winded discussion… maybe another post… but the answer seemed to be to use a battery that housed a bit more energy with minimal weight penalty.  The best thing available looked to be the SMC LiHv packs so I ordered a couple 6S 5300s.  They are no heavier than many other 4500-5000mah packs and pack a bit more punch than standard LiPos due to the HV cells.  Best I can tell, they are the bomb!

I flew the Gripen for just 2 flights.  It took off beautifully from our Geotex runway and tracked nicely in the air as long as you kept a good amount of power on it.  You could slow down pretty well and the plane would continue to fly but it starts doing a bit of rocking which indicates you are approaching stall.  That is a good thing compared to many jets who (as I understand it) just drop a wingtip and stall with less warning.  Credit to the aerodynamics of that big delta wing I suppose.  Visibility leaves a lot to be desired between the gray and the arrowhead body shape, there isn’t much to keep me oriented aside from keeping it close.  I added some extra markings between flights 1 and 2 which helped but to get much better I’d really have to do some thing drastic.

And then I had to land it.  I probably carried more speed than I had to but again the big delta wing makes itself known during the flare as you can really get into a fairly nose high attitude as you land which results in smooth landings with little load on the gear.  Both flights the landings were really pretty.

I didn’t really get a chance to do much trimming or playing with rates and mixes as the flights were by necessity short as the power system is typical from what I understand… which is to say inefficient and power hungry!  The good news is it apparently needed little to no trim so I didn’t need much trim time!  By the time I got a bit comfortable with it I was on approach.

I flew the first time for 3.5 minutes before landing with a decent battery margin and the second time with a bit more crosswind and holding a bit more speed during the flight for only 3 minutes.  The first time I had a decent margin of capacity left but not a ton and the second it was a bit lower than where I normally like to land.  This is just far to short for me.  I couldn’t get the plane up and comfortable with enough time to actually explore much of the flight envelope and I also didn’t like how fast it has to fly in order to fly well.  That also left me no time to try out different mixes, play with high alpha manuevers etc…

Maybe I could adjust to it eventually… but I don’t think I’d ever be really happy with flying it.  Having a fast flight regime is great, but I also want to be able to fly slow and gentle.  I have planes that can do both but I don’t this is ever going to get there.  I’m also concerned that if I try to push it to do what I want it to do I’ll find the hard edge of control one to many times and crash the plane.  There are just to many other planes I would rather fly and/or want to own to hold on to this one.  This one flys to much like its scale counterpart… fast, powerful and heavy.  I don’t think EDF fighters are for me.  For those who like these type of airplanes, I suspect there will be some folks who will love it.  Just not me.

Maybe an A10 or L39 someday…  In the meantime, anyone interested in a low mileage fighter?

Radian EDF “Frankenplane”

I have recently spent some time actually starting and finishing (a new concept for me sometimes) a few projects that I had started or at least planned on starting for a while.  One of them was to build something out of the various Radian parts I had aquired over the course of the last couple years.  I have had a replacement body for the Radian (just the foam) for a couple years and a pair of wings from my original Radian as well as having aquired a horizontal stab, and rudder.  What I didn’t have was a motor, nose cone and prop.  Nor did I have replacement servos, push rods etc…  Well not the exact original equipment anyway.

What spurred me to make use of all I had accumulated was actually the crash of a UMX A10 that I owned.  I know that may sound strange but hold that judgement just a bit longer, please.  Here’s the story…

I was recently flying at a local indoor event and wanted to at least get a test flight on my UMX A10 which had some minor damage I had recently repaired.  When the opportunity arose I taxid out and started my takeoff roll when suddenly a small Cessna materialized just a few feet in front of my airplane.  (Finally proof that Star Trek transporter technology does exist!!)  My perhaps ill timed reaction was to stay in the throttle and pull full back on the elevator.  This resulted in the A10 clearing the other airplane but left it nose straight up and quickly approaching the ceiling.  Not familiar with the flight regime of the A10 I quickly cut throttle and pushed the nose down to get control.  Unfortunately this was extremely effective in arresting my altitude gain but soon found the nose of my A10 impacting the gym floor with the entire weight and speed of the airplane behind it…  there was not much left forward of the wing.

As a friend and I started sorting through the wreckage back in my shop later that day a particular part of the dimunitive A10 caught my eye and I started wondering what airplane I could mount the dual ducted fans on?? 

I went through several options in my mind before I remembered the pile of glider parts I had in the corner.  Thus began the new project.

I first started assessing what all I would need to make my fevered dream a reality.  I have enough small servos laying about.  A small receiver wasn’t a problem either and I have enough odd hardware laying around that control rods, horns and all the rest of the miscellaneous hardware shouldn’t be a big issue either.  That only really left a canopy and some sort of nose cone plus a way to mount the EDF pod onto the glider.

I first tackled the nose cone.  Because the original motor on the radian is tilted both right and down, the front of the Radian is not at all straight so just putting an empty spinner (for instance) was not going to look very good.  To fix that issue I simply eyeballed a line more perpendicular to the thrust line of the craft and sliced a small portion off the nose to give me a better starting point. 

I then did some measurements and jumped on Tinkercad to design a new nose for the Radian.  I had to make it a bit oblong as the nose is a bit taller than it is wide but I managed to create something that looked workable.  

I integrated a base plate with an opening in case I needed weight or perhaps a good antenna location (?) and then glued it onto the front. 

I had to add a small shim at the top to lend some strength to the forward part of the foam where the canopy attaches via magnet and it at least looks now like it should work.  At least now I have something aerodynamic to lead the way.

Next I did all the normal stuff you’d have to do to assemble one of the less complete ARFs you might have worked on… mounted the servos, built linkage, attached the rudder elevator and generally assembled the airplane.  After that I had everything ready except attaching the wings and the aforementioned EDF power pod donated by my UMX A10.  I decided to attach the wings and consider exactly where to add the “power pod” when I realized a problem.  The wings I had were from an original Radian but the body was from a Radian Pro… The issue there is that the Pro used a completely different wing attachment method.  While the radian used a wing tube and interlocking tabs on the wing roots, the pro used a plastic insert with tabs that projected out from the body, inset into the wing bottom surface and bolts into the wings to hold them in place.  Time to do some more modification!

First I took a straight edge and marked a line at a right angle to the trailing edge, just far enough outboard to eliminate the slightly enlarged wing root area and interlocking tabs that were no longer needed. 

Then it was time to get out the razor knife and eliminate the problem.   I also had to carve a slot in the bottom surface of the wing to clear the projecting tabs.  This actually seemed to work out even better than expected.

Next I went back to Tinkercad nad created an insert I could put in the wing so that I’d have something for a bolt to thread into to keep the wings in place for those blistering high speed passes (not).  I incorporated a hex inset into the piece so a nut could be captured in the piece and also so that my bolt would not have to be very long.  I also included a small taper to help the bolt insert easily but line up with the nut so that a cross thread is unlikely.  My dimensions proved to be a bit tighter than anticipated so I had to drill out the hole just a tad to allow clearance for the bolt to go through.  On the hex end this actually worked to my advantage as the nut was such a snug fit it would be very difficult to remove once inserted.  Here’s the design.

After cutting an appropriate sized hole and then gluing in the insert this seems to work pretty well.  One other minor issue was since I had shortened the wings a bit I had to also trim the carbon wing tube a similar amount to allow the wings to seat properly.

The next item on the list was to actually mount the EDF pod onto the now mutant Radian.  I realized that having eliminated the normally nose mounted motor and prop, the airplane was likely to be tail heavy.  I also considered that I would have to run wiring back to the motors if I put them back on the tail area ala the A10 or DC-9 type aircraft so I quickly abandoned that idea and decided that having the motors up near the balance point and placed for easy pass through of the wiring straight down into the aft compartment beneath the wing made more sense.

The engine pod has a tab and a matching hole where a tab was inserted into it when it was connected to the A10.  At first I thought about just cutting a matching hole for the tab into the top of the Radian and mounting the pod directly but that created a couple issues.  The pod would be tilted fairly drastically downward at the rear of the nacelles which would impart a fair amount of up or down thrust depending on how that thrust affected the airplane… its beyond me to figure out which.  And it would also likely bring the nacelle into contact with the wing.  So to hopefully eliminated these issues I needed to align the pod with the thrustline of the Radian.  I also wanted to make use of the tabs and the maxium surface area available to mount the pod onto the convex shape of the top of the glider to be sure it stayed put.  So back to Tinkercad I went, to create an adapter plate to mount the pod effectively.  As you can see from the image below, I had to capture something close to the curve of the top of the glider whilst generating a slope to offset the tapering of the body so that the pod would end up (hopefully) only providing motive power and not pushing the glider nose up or down.

It took a couple tries to get the curve to (almost) fit the top of the glider and to come up with the slope I wanted to get the thrust line I was trying to reach but eventually I called it close enough and did a final print.

I later realized I needed a pass through hole for the wiring as well but a dremel bit took care of that quickly!   I created a similar pass through from the top of the aircraft down to the electronics bay so I could route the engine wires down to the speed controllers below.

Here’s the finished piece in place on the top of the Radian body and then with the pod attached.

At this point I started hunting around for a canopy replacement which apparently are made of “unobtainium” as there are no spares available anymore.  Luckily a nearby RCer that is friends with one of my flying buddies came up with one off of a Night Radian and it seems to fit just fine… It might be just a bit loose so I’ll probably just wrap a rubber band around it for the first flight or two while the shakedown gets done and find a way to improve the hold on that once I decide if the plane is going to even fly reliably or repeatedly!

At this point it was just a matter of installing and connecting all the electronics, servos and linkages, etc…  and we should have something flyable.  I won’t bother with much detail for this part of the build as it was all pretty standard.  I ordered a couple of inexpensive speed controllers (I’ve pulled red wire from one of the plugs to the receiver from 1 speed controller so I power the flight systems off the BEC circuit from only one of the ESCs) and used a 6 channel DSMx capable Spektrum receiver that had 1 remote so I could get some antenna diversity but that was about the only things of any note.

Next I checked balance to see what Of course it was way tail heavy so I kept increasing the battery size I used.  I ended up with a pair of 2c 2200mah batteries as far forward as I can get and the balance is about right.  That is only 4400/800 = 5.5 times the capacity of what was in the A10.  Considering this is a glider and will fly with power off at least 50% of the time (I hope) and I’m estimating I can fly for approximately “all day” with these batteries!!

I’ll post an update after I get a flight or two on this Frankenstein monster with parts from:

  1. Original 2M Radian (Wings)
  2. Radian Pro (Body)
  3. Night Radian (Canopy)
  4. UMX A10 (Motors/Nacelles)
  5. 1.2M T28 (Servos)

Plus a pair of new speed controllers, custom designed and 3D printed parts, and a selection of rods/linkages etc… from stock I had in the shop.  After some additional nomenclature added, she looks like this:

I’ve christened her the Radian EDF and I’m really looking forward to flying her at the upcoming EDF event at my local club field.  Pretty certain no one else will have one there!

Full 3D Printed Airplane – Chapter 3 (Flying)

In part 1, I discussed my road to my first 3D printed RC airplane… The Wolf from Eclipson.  It’s their “free download” which, I’m sure, is meant to lead to a good experience and influence a future purchase.  The printing part of the project went well, but I still had to get through the assembly and flying part before I would call this a success.  Part 2 will cover some of the assembly process and part 3 the flying and results of that part of the adventure… so onto part 3!??

Ok, so I’m skipping over the gathering of supplies, painting, assembly, etc… Thus why I titled this Chapter 3 when I haven’t posted a chapter 2, but I just have to get to the flying part so here we go!

Spring has been cold, wet, and breezy with only a couple of days of warmer weather with anything like a reasonable wind speed… so I just finally decided to fly it anyway!  It was a stiff crosswind but the temperature was at least reasonable so after a long journey of learning and more than a little trepidation, I had my friend Steve give it a toss for me.

So first, I’ll comment on the actual flying characteristics.  In a word, excellent!  The Wolf seemed to have plenty of power and only required some elevator trim to have it fly hands off.  It flew really nice with maybe 1/3rd to 1/2 throttle and was capable of a wider flight envelope than I had expected even to the point of seemingly doing well as a power glider.  I forgot to do a lot of real test flying as the airplane was just fun to fly!  I did regret that the designer had opted not to include a rudder and I’m already thinking I might try my hand at some design work to add that feature but otherwise its hard to complain about how nicely it tracks and soars.

On the more technical side of things… while it flew great, it had a few issues.  For reasons I’m still figuring out, the skin of the airplane seems a bit on the fragile side.  My launch catapult (also my flying buddy), Steve, cracked a layer line just by gripping the airplane. 

For reasons unexplainable by mortal man, my elevator linkage had come off the control arm by the time I went to make the maiden flight and I had to steal a wheel collar from the axle to make a field repair.  This caused my first landing to be “wheel-less” and on the skid which caused a chunk out of the skin to crack and break loose on what I thought was a fairly smooth landing in the grass.

On the second flight the prop collet exited the airplane and I had to make an unpowered landing, I managed to bust the Wolf at/or near the glue joint… so maybe that was just a bad glue joint or are the layer lines just a bit weak??  I’m still figuring that out.  The collet issue is also being addressed in order to stay with the folding prop, which I think was a great choice.  It seems to be sized appropriately for great performance and allows for some true gliding without the drag a fixed prop would cause.

Those issues aside, everything worked well and I’m looking forward to some more flights in the future.

 

Full 3D Printed Airplane – Chapter 1 (Printing)

I’ve had a 3D printer now for a couple years and printing some add on accessories for my RC aircraft was the main reason I purchased it.  Cockpit details, air scoops, replacement plastic parts for broken scale details like antennas and the like have all been projects I have tackled successfully using my 3D printer.

My particular printer is an Ender 3 with the only functional modifications being a v4.2.7 motherboard, a glass build plate and some updated build plate springs.  The base unit can be bought several places and I recommend it as a beginner hobbyist platform.  From what I have seen, it is widely accepted as a great device in this role.  Here is my link to purchasing the current version of this printer from the Creality Store via Amazon.

At the time I purchased it, I was not particularly interested in or really aware there were very many options for printing a full RC airplane.  What I had seen were overweight, ugly airplanes that seemed to just barely fly.  After a time I heard about a new material that made it more feasible to print something that might actually approach a reasonable level of functionality… something called Light Weight PLA.  Here is a link to what I purchased.  There are other brands out there but eSun seems to be a well accepted as a quality product and I don’t have enough experience to accept the challenge of sorting out more factors than I needed to when I was embarking on a new adventure so I went with what seems to be a premium material.  Here’s a link to that:


So of course I purchased a roll of filament and quickly decided it was going to be to complicated to set up my printer to work with it.  Also my printer had such a small print surface that I surely couldn’t print anything of any size… so the filament went up on shelf to gather dust.  The reality was somewhat different, but I wasn’t wrong that with my level of knowledge at the time, I probably wouldn’t have had good results.  

Fast forward a year (or maybe 2??) and I happened on a YouTube video showing a really nice looking airplane that was 3D printed!  This got me thinking, maybe it was time to revisit the idea.  I had learned a bit more about 3D printing and felt I was ready to take the plunge.

So for a week or so, most of my recreational video watching was of 3D printed airplanes and fair amount of web research turned up some interesting information.  There were quite a few sites that espoused particular parameters and setups to get successful prints for LW-PLA and there were a number of free designs around.  What finally made me open the box was when I came across a free download from Eclipson

The 3D printed aircraft designs on their site are exceptionally nice looking… rivalying the available ARFs on the market from even the top tier companies using more traditional techniques.  They do charge for these files, but the prices seem very reasonable for the level of quality they appear to represent.  Their website is very well built and presents their product very nicely with lots of pictures and available information. 

Time out for a rant… feel free to skip to the next paragraph.  The only thing I wish for, and I may be completely alone here, is a nice manual to help me build.  They do a one page sheet that has a lot of information packed into it that is very helpful, and there is a good build video but for me personally, I hate build videos.  Especially videos with no narration or discussion like this one.  This one is as good as any I’ve seen, but I would much prefer a well illustrated and written step by step assembly book.  I’d even pay for one in addition to what is available if it was well done.  I find it hard to keep stopping  and starting a video… finding a way to backup and find that one part I’m looking for… stopping at just the right point to see what I want to see… Its all just a PITA for me.  I know some folks would rather have the video… I’m NOT one of those.  OK, rant ended.

Best of all, by all reports, the Eclipson aircraft fly very well.  What really got me out of the starting blocks was that they even provided ready made Gcode for their models, preset to work on my exact printer!  Its like just feeding in the files and hit print and out pops an airplane!  Ok, well maybe not quite that easy but it does get you around having to learn all the parameters necessary to print good quality aircraft parts using this material.  Certainly tweeking their settings a bit could make the parts even a bit better, but what I found was using their exact settings produced parts good enough to actually function.  Or at least it appears so to me.  I don’t mind learning about all the parameters and figuring out how to dial in my printer to produce my own good LW-PLA parts, but I like it even better if I can do that while another perfecty usable part is being produced!  Icing on the cake, they have one airplane you can get the files for simply by signing up!  This airplane is the Wolf.  This RC design is based on a german glider design first produced in 1935 and motorized for RC use.  So I signed up and downloaded the files.

I began printing parts from the supplied Gcode and occaisionally I’d tinker with my profile and try printing my own part just so I’d have that ability in the future and because in one or two cases I realized I could print the part just a bit better if I tuned the settings for my particular printer and material.  For instance, my eSun White PLA (that I used to print a few parts that needed more strength… per the instructions) happens to print better at 5 or 10c higher temp than the supplied Gcode is setup for.  So I pulled up the STL file provided and used my profiles I generally use for PLA+ and printed out those few parts with my own Gcode.  I suprised myself with how well those parts printed out.

Here’s some obligatory “parts being printed” photos..  All of these are using the eSun LW-PLA+.

First section of the port side aileron getting underway…

Here’s another section of the aileron

And this is obviously the vertical fin.  An exceptionally nice print if I do say so myself.

Up to this point, I had only printed some of the smaller parts of the airplane.  But if I want to have an airplane I have to tackle the big parts next and in my experience, big parts take a lot of time to 3D print.

I’m not typically impatient when building an airplane.  I don’t mind if a project is sitting on my bench for a while waiting for some necessary parts to ship in or whatever.  I can always find another project or a different aspect of this project to keep me busy.  I will admit however that I was a bit troubled by the thought of how long it was going to take to print all these parts.  I have done some moderatly large parts on my printer before that took 14 hours or more!  Looking at the airplane I was afraid weeks of printing overnight would be involved.  Luckily, once I tried it, nothing could be further from the truth.  I quickly realized that because of the way you print these, there is very little or no supports needed/desired and not much infill either.  This results in parts printing much faster that I expected.  I printed the first dozen or so small parts over a weekend and I think I got all of the LW-PLA pieces (by far the largest part of the airplane) done during a single week of just part time printing while working on other things.  Honestly think I could print all the parts in 3 days now if I really tried.

The final piece or two I needed to print, was the tire and hinges.  These pieces need to be printed  from something a bit more flexible and in the 3D hobbyist world that means TPU.  TPU is about the closest thing to rubber that we can print on a 3D printer and it demands yet another totally different set of printer settings.  After reading a bit on the proper settings, different brands and types of TPU available, etc… I decided to give it a try.  I had gained a little confidence through the process of printing the LW-PLA so I made the leap.  Another order to Amazon and the very next day I had a fresh role of eSun TPU95A in gloss black.

With my very first try, aided by the suggested settings from eSun and a small tweak or two based on articles and videos on line, I had my very first TPU print… a test piece based on a video from a youtuber named CHEP.  It looked great and did point out one small wall adhesion issue so I tweaked one more setting and tried printing my tire.  It worked well enough on the very first try.

As I went through and “post processed” the prints, removing some skirt material and sanding a couple of spots, etc… I did manage to damage a part or two and had to reprint a couple as a result.  The parts aren’t perfect and I have some ideas about what I might try to do differently if I do another airplane down the road, but I think it might actually fly some day! 

After assembling the needed RC gear and a few other necessary supplies (more on that in a follow on article) I had this pile of parts sitting on my bench… time for assembly!

3D printing add-ons for the Freewing JAS-39 Gripen

I recently acquired a Freewing JAS-39 Gripen (Griffin for us English speakers).  I’ve never had much interest in EDFs but why I have it and what possessed me to buy it is a topic for another post.  For my purposes here, it is enough to say I have one and I wanted to make it look a bit more formidable by adding some weaponry, help out with balance with a little added weight to the aft of the balance point and just add some scale touches at least for display purposes.

Luckily, there are some readily available STL files.  STL files are the output of a CAD program and are what you need to input to the slicer software which produces the G-code files.  The slicer software parses through the STL file to decide what instructions to send to the 3D printer to create the shape and creates a list of those commands which is your G-code file.  So, having the STL files means the hardest part of 3D printing what I want (the actual CAD design work) is done for me!

I printed a couple of Iris-T missiles first using some white eSun brand PLA+ filament.  The Iris-T is the European equivalent to the US Sidewinder missiles.  Both are extremely smart, relatively short range heat seeking air to air missiles.  The Gripen can carry either but I decided to start with the more “native” weaponry.   These are almost always carried on the wingtip hard points on the Gripen and since the wing tip hard points are already in place on the model, it made sense to start with something for those stations.  They came out pretty well with only a little bit of stringing and just one or two very slight imperfections.  I was pretty happy.   There are keyhole slots in the end of the rails on the wingtips of the Gripen and there are mounting rail STLs available so I printed a few of those as well.  The missiles have a flat spot designed in where you can easily glue these to the missile.  Once that was done, with only a little sanding/carving/cleanup I was able to slide the missiles onto the wingtips.  Here is a pic of the IRIS-T on the wingtip of the plane pretty much fresh off the printer with just some minor gluing and sanding.  These are 1/9th scale just like the airplane.

There are a couple of nice things about having these on the plane.  First, they add some needed tail weight.  The Gripen has a very swept back Delta wing so the wingtips are far back from the desired CG so while not the ideal place for extra weight, its not a terrible spot either. Second, they cover up the sort of ugly wingtip “rails” with some nice eye candy.  And third, I’m thinking there may be some wingtip strikes with the landing gear being fairly narrow as they are on many jets, so they can act as wing tip protection to some extent.  I can print another missile or fin or whatever, but the wingtips of the airplane would be much harder to reproduce and replace if they get beat up or broken.

Next I tackled some Meteor missiles.  These are long range, radar guided air to air missiles.  In real life these things are around 13 feet long, so scale they are around 16″ long.  These are massive and carry a big warhead.  Imagine a telephone pole coming at you with a big bomb on the front… at multi-mach speeds!  Used properly they are on par with the best such weaponry out there.  With the right launch parameters and guidance these can be fired from 100+ miles away!

These are generally carried on under wing pylons on the Gripen but the model doesn’t have any built in hard points for those so I had to print out the keyholes/hardpoints and the pylons themselves and get those mounted on the plane.  It took some carving in the wing, careful alignment and slowly digging a bit deeper until I had what I wanted then glued the hardpoints in.  With those in place I could slide the pylons on and lock them in place then slide the missiles in place under the pylons and lock them in and bingo, we are in business.  Below are some snapshots of that process and the results.

 

 

 

 

 

 

 

This is the outline of the mounting socket as I’m starting to remove just the skin/paint in preparation to route out maybe an 1/8 inch or so of foam so I can glue it in..

This is the socket in place.

 

 

 

 

 

 

 

 

 

 

 

 

The tape attached to the pylon is adding some pressure after the glue is in place and just starting to setup nicely.  It looked a little off so needed some pressure to get it to sit level in the wing.

Here’s the whole thing after I hung a meteor on it… starting to look pretty good! 

After I got this far I was down to needing sanding and painting so I started doing a bit of research and found a variety of paint schemes available and went to work.  The meteors especially varied a lot, so I took a bit more license with those and stayed with the white scheme but the IRIS-T is almost uniformly and almost completely gray so I decided to reprint those so I wouldn’t have to do so much painting (I hate to paint!).  Then I took advantage of where some of the color bands are to cover up some of the glue joints with pin stripe or color bands on both missiles.

Meteors (on left) and Iris-Ts (on right)

I’m sure for the true scale guys these are nothing special but I think they add a lot to the look of the airplane and the effort was not huge.  For me, having the 3D printer (and the efforts of the guys who first did the design) made it possible to really upgrade the look of the airplane with minimal effort.  And no one has anything that looks like these!

Of course, it doesn’t end here.  I have engine inlet and outlet covers printed as well and I’m eyeing some fuel tank designs I’ve seen…

So if you are wondering if you need a 3D printer to add a little extra something to your hobby… the answer is of course, NO.  But I recommend it.  There’s a lot you an do that will add that little something extra to your favorite bird.  I expect to do a bunch more of this in the future.

Couple of new “to me” motor vendors… specs

Electric motor specs available

I recently was involved in a conversation that started out bemoaning the fact that Horizon hobby often doesn’t supply much in the way of specifications on many of their electric motors, when someone referenced a couple of sites that provided a plethora of information about that particular electric motor vendor products.

I have used ecalc to help me predict power system performance for years but that doesn’t get you around a lack of decent information and for those who for whatever reason don’t have access to that tool or have trouble understanding how to use it correctly, information from the vendor like those below has a very high value.

I haven’t tried out these motors for myself but I applaud the disclosure of specifications along with predicted (maybe tested) test results with a variety of propellers.  This really allows you to pick a setup that does what you want to do without a lot of trial and error as well as allowing us to get the most out of the motor, again without a lot of trial and error.

So here are the links to these manufacturers sites.  With this sort of available information I may have to give them a try.

Leopard Motor Data Chart

Badass Motor Data Chart

 

 

Aces High P47 Retract issues and repair

I’ve really just gotten started flying my Aces High P-47, with maybe 6 or 8 flights as I figure out the ideal balance, throws and flight envelope for this airplane.  However all of that got a bit sidetracked a few days ago when my port side retract refused to retract after a landing.  I had to cycle it 3 times to get it to extend during that last flight and after the landing it was just totally unresponsive.

So back on the bench, I started trying to troubleshoot the issue.  First off, you have to understand how everything goes together.  The retracts in the P-47 are simple units that require a separate controller unit that looks like this:

The retracts each only have 2 wires, a positive and a negative.   Each retract unit plugs into one of the back wheel  connections on the controller.  The controller has one servo lead for power and signal input to the controller.  This plugs directly into your receiver on whichever channel you chose to control the retractable landing gear. 

In my case, in order to simplify wiring to each wing, I have a wiring harness that allows for a single multipin connector to go to each wing rather than separate servo wires.  Since the harness consists of multiple wires and crimped on pins, etc… I first decided to eliminate the wiring harness in order to eliminate any possibility that a bad wire or crimp connection in the harness was the culprit.  That accomplished and no change in operation I tried swapping the port and starboard connections.  The failure still appeared to be in the port side unit.

At this point I got in contact with Extreme Flight to see what my options were.   I provided my troubleshooting results and awaited a response.  Although the response took several days I did eventually get an email back from a support person who questioned if I was certain the retract unit was failing and not the controller.  At this point I arranged a call with the support person and walked them through the steps I had taken and they agreed that I needed a new retract… which is unfortunately on back order… with no predicted ship date!!

They did agree that the retract set should be replaced under warranty and sent me confirmation of the order… but of course I was not hanging this plane up for the season without a fight!

So moving into some real testing I removed the offending retract from the port wing and the controller from the body and fished out a spare A123 flight pack and my trusty servo tester.   (Note: when I pulled the retract I was sure to use the retract wire to pull a string from the wing root out to the retract area so that replacement would be simple. ) 

First using the starboard wing to check my test bed, I confirmed I could cycle the working retract without an issue.  During this test I noticed that the controller has LEDs that cycle from green to red depending on which way the controller is trying to drive the gear.  The LED goes off once the retract hits its limits and (I presume) the controller senses an end point has been reached.  I’m guessing it senses the spike in current as the motor stalls and automatically shuts down.

I also measured the voltage being supplied by the controller and verified that the controller simply flips the polarity to the motor in order to reverse the direction when the servo signal goes from one end to the other.  Following up on that I started trying to establish whether the continuity of the wire was good all the way to the retract motor.  I stuck a couple of very fine pins into the wire up near the motor and tested for continuity from the connecot to that point.  This established both wires were good to that point so it was down to either the motor being bad/burned up/open or just a bad connection to the motor.  I measured the resistance of the complete working retract in the other wing and established a baseline of about 4.5 ohms was a normal working unit.  Testing the bad unit showed infinite resistance/an open circuit.  After I did this, I quickly realized the red wire had indeed broken loose inside the “can” that surrounds the motor and I was able to easily pull the wire out of the entry point to the can/motor housing.  The problem now was that the motor sits inside this can and has no screws, set screws or other obvious way to get it open!

Deciding that I had nothing to lose I started disassembling the retract mechanism.  

Once the screws on one side were removed it was simple to separate the motor assembly/screw/trunnion pin from the remainder of the servo.  Note that there are  ball bearings in the sides of the assembly so while mine easily stayed in place, I’d be gentle and try not to dislodge those if you ever have reason to dig this deep!

Once the motor can was loose in my hand I realized that if it were going to be possible to get inside the can and get to the solder connection point on the motor it had to be some sort of split/friction fit or two parts had to twist apart somehow.  I first took a razor knife and tried to split it along either of two lines around around the enclosure… neither yielded to my efforts.  Finally I grabbed the center of the can with a pair of pliers and tried twisting either end.  Finally the end nearest the trunnion pin rotated a bit and I was able to unscrew that part and slide the motor out from inside the rest of the assembly.

At this point it was possible (if difficult to manipulate due to just the small size of the solder tabs on the motor and gauge of wire) to re-solder the wire and test the operation.  Hooking the controller back up to my servo tester and operating the retract motor was again attempted and all went well.  Keep in mind the motor will just run continuously as there is nothing stopping the motor so no current surge to tell it to stop.  This is normal/expected operation in this state.  Also note that there is a spacer in the end of the can where the shaft extends out to the trunnion and the shaft of the motor is keyed into the threaded shaft so be careful when reassembling not to lose of those parts and to align the motor carefully so its keyed shaft fits correctly to the threaded rod end as you put things back together.  I was concerned that the wires might touch the can and short out the controller output as there is no obvious protection from this happening but it didn’t so I’m assuming the inside of the can on that end has some sort of clear insulator or other mechanism to prevent it even though I never figured out exactly what it is.

Once I completely re-assembled I took some steps to protect against another failure due to motion of that wire or strain on the wires.  First I coated the entry point with liquid electrical tape and let it set up.  

As you can see by the scars on the can, I marred it up just a bit with my pliers during the process but now that you know that the end cap nearest the pivot point is the one that unscrews, you could probably avoid this with some care and perhaps a wrap of tape around the can in strategic locations when disassembling.

Once that was accomplished (on both retracts) I mounted the retract back in the wing, used the pull string to get the wire properly routed.  At this point I pressed the wire up against the balsa sidewalls of the wheel well and applied a bit of glue to make sure no further physical strain could be applied to the wire at the entry point to the can.  As shipped that is just an entry hole with no grommet or strain relief of any type so I’m being doubly certain to protect it moving forward.

How will it hold up?  Is this the end of the retract issues on this bird??  Well we shall see, assuming I manage not to do anything stupid during my flights.  Let’s hope for the best.

I’m only now realizing that I have no idea what keeps the motor from spinning around in the can… I didn’t see an alignment pin or flat inside the back of the can etc… but it would seem there must be something there besides the wires that can’t rotate… I’m guessing there is something in the front area that accomplishes this.  Well that’s an investigation for another day and probably only if/when I get the new set or have to work on these again so lets hope that remain a mystery!

If you have this airplane or the Aces High FW-190 from Extreme Flight that looks to use similar retracts, I’d definitely address some sort of strain relief on your retracts to avoid similar issues.  Blue Skies.