Category: My Fleet

A while back, Kelly brought his P40 over to complete final piece of the install for his electric retracts into his Top Flite Giant Scale P-40.  The tail wheel.  We had the main gear already installed in the wing and tested and had just the tail left to complete the job.  We were well into the job and ready for some testing when we realized that we needed to cycle the gear to finish up… but a problem presented itself.  Kelly had not thought to bring the wing for the P-40 and attached to that wing was the control unit!  There is no way to cycle this gear without a control unit, but luckily (not as lucky as I thought at the time) I have a very similar control unit in my Mustang so I just walked across the shop and pulled it out.  That is where the trouble began…  You see, for some reason over the course of the last 6 months, Robart has decided to switch the connector type from a standard servo type plug to a 2 wire… I’m not sure what it is so let’s just call it a “Robart connector”!  They also decided to change from using type 1 and type 2 to using type A and B… but more on that later.

OK, so this connector issue is “no hill for a climber”, right!?  First, cut out the plastic around the opening on my control board and plug in the P-40 tail wheel there, then create a female to female servo lead to hook the control box to the receiver… my lead is tied down in the Mustang… and wallah!!  That taken care of we can now cycle the tail gear.  Yahoo!  With a bit of custom fitting (Dremel tools are great, aren’t they?) the P-40 tail wheel is all good.  That all accomplished, just stick the control board back in the Mustang and reconnect it… careful of polarity… that would be expensive!!  All good and the Mustang can retire back to it’s corner for a few weeks….  All good… I thought.

So a few weeks pass and it’s time for the club picnic.  Great fun, good food, excellent weather… sounds like a good time to show off the Mustang for the members and especially the families that rarely make it out to the field any other time.  Low 110+ MPH, nice slow (for a Mustang) photo passes, big loops and stall turns… and then have the pilot salute the crowd after a perfect main wheels only landing… The perfect recipe for a nice day at the field.  At least that’s the plan…

Upon arriving at the field, we (it takes a village) got the Mustang assembled and did a quick cycle of the landing gear and, yep it all works but… wait a minute.  One of the mains goes up when the other goes down!??  That’s weird.  Power down and back up with the wing opened up… try unplugging and replugging the two main retracts to get them in sync… still no joy.  How strange…  As I’m standing there cycling them one more time (bordering on insanity now… repeating the same actions waiting for something different to happen) and get a whiff of something hot/stinky.  Thinking the engine that someone is running 20 feet down the flightline must be getting hot or maybe something got against the hot engine down there.  Back to my problem and now the tail gear has quit moving… just staying down.  When I decide to check that connection it suddenly becomes obvious… the tail gear is plugged into a main gear slot on the Robart controller!  That must be what’s wrong, the two are reversed.  Swap those two and now the main gear works great.  But wait, the tail gear still isn’t working…

OH CRAP!!!  Now the full impact of what I’ve done hits.  The tail retract is what Robart calls a type 2.  The difference is that a Type 2 takes less voltage than a type 1.  And in case you’re wondering I can attest that plugging a type 2 into a slot that is set for a type 1 will release the smoke that is part of the “smoke and magic” formula that makes these things work.  At least it will after several cycles…  I haven’t even flown yet and I suspect this trip to the field just cost me $50-100.  That burning smell I detected earlier was something getting hot alright… but it was a lot closer than I thought!

If there is a silver lining… that tail gear was fully down and not likely to go anywhere so since I’d already paid the price I went ahead and got some flights in.  The last one for the day was a pretty close approximation to the one I’d dreamed of, complete with a 115 MPH high speed pass and a sweet landing that elicited some envious comments from fellow warbird pilots.  “You know you make us look bad when you do that, right?”  and “Mine doesn’t do that!” were among the shouts from the spectator area.

Once home I sent some email to Robart asking about a replacement and they promptly replied with the appropriate part number and instruction on how to get a unit that would drop in and fit my control board.  When it arrived, one more little detour came up.  The new unit arrived and was marked with a “Type A” tag.  Huh?  I only have Type 1 or Type 2 options on my controller??  OK, so type 1 would be A and 2 is B, right?  Wrong!!  My old unit was a type 2 and Kelly’s tail wheel worked when set to type 2 on my controller… Plus it’s still a lower voltage unit (checked the instructions and confirmed, main gear is Type B and tail is Type A) so not only did the nomenclature change but it didn’t follow what you might think of as the logical choice either!

After reading everything over 2 or 3 times to confirm that things are as I think they are, got the new unit plugged in and tested and it seems to be working fine… no sign of smoke or heat.  Nice smooth cycles up and down.  So, the moral of the story is…. “Quit being nice to your buddies!”   Wait that can’t be right!?  Maybe, “Be a bit more careful when plugging and unplugging all those wires in your complicated and expensive airplanes!”  That one sounds better!  For sure this one applies: “No good deed goes unpunished.”

Myself along with a couple of other flyers at my club have taken to doing a bit of glider flying of late.  A couple of us have Radians while our current president (George) has a true un-powered balsa and monocoat ship.  While the Radians have no trouble getting to altitude with their on-board electric motor, the traditional glider needs some external help.  We don’t have a winch at the field and a high start takes a lot of time and effort to rig and takes up the whole field for a period of time.  In short, we wanted a better way to get a glider to altitude.

We discussed doing a tow but that seemed to require to many modifications and complex release mechanisms… While it looked fun we decided that a “carry” to altitude might be a better solution…. and it so happens I had picked up just such a mechanism at a swap meet a couple years ago.  I pulled it out and got to work to get it in “ready to fly shape”.

Of course life is never that easy and I immediately found a couple issues.  First, the unit had developed some warp over time and it seemed a bit flimsy.  It also doesn’t fit the top shape of my Telemaster’s wing.  That last I’m hoping to hold off for another time.  For now, I hope a bit of foam will help to distribute the load until I can come up with a better solution… if all else gets worked out!

So first things first, I started out by dis-assembling the carriage and doing some sanding to expose the wood so I could bond on some reinforcing.  For this I chose some carbon fiber tape from Dave Brown models that I had picked up on a whim at a hobby shop I recently discovered while on a business trip to Cincinnati.  I had never used this product but the instructions were spot on, recommending tape to bind the ends, etc…  I think you’ll do well if you just follow the included directions.

Here are a few pics showing the process…

Here is the disassembled structure.  Note that one of the bolts that form the pivot twisted off during the dis-assembly process..

This is after sanding.  If you don’t get rid of the paint and open up the grain the epoxy won’t stick and the carbon fiber reinforcing will just peel off.

 

Here is the cutting and fitting process.  The tape is vital to holding the carbon fiber together during cutting.  Remove it just as you lay the CF onto the epoxy.  By cutting all lengths before mixing the epoxy I managed to do one whole side before the epoxy started getting gummy.

 

Here is one side with the CF  laid down and weighted down so it dries straight.  Maybe not as neat as I could be but I think it will serve the purpose.

 

After letting this dry overnight and reassembling I did some tests and things were not working well.  The glider would scoot back on the cradle and the rubber bands would slide up against the front of the carriage.  This caused release to be unreliable.  One side or the other would come off sooner with several seconds before release occurred after the servo released the rotating arms.  Sometimes it would be several more before the other side let go.  That could cause major issues.  I tried polishing up the leading edge of the wood and even waxing it but that proved to be insufficient.

Here is a picture of the hold down system… The bands won’t stay out in the indent area of the release arms.  The bands rub on the wood and release is iffy at best.

 

 

Realizing I needed to get the rubber bands to stay in those indents at the ends of the arms, I realized that the direction they were pulling had to be adjusted.  No amount of sliding the glider forward or careful routing of the bands would make that happen so I decided I needed something to redirect the bands around to reposition them on those release arms.

Here is my fix… A peg (really a bolt held in on both sides with nuts) to redirect the rubber band up and over so that it stays in the indent of the release arms.  Now the release is immediate every time.

 

With this modification I think I am ready to test the carriage with a glider aboard.  I’m guessing on how many rubber bands are needed to hold the carriage in place, how many to hold the glider in place and really about everything else as well.  Planning on a test run or to with the Radian perched atop the carriage tomorrow evening.  Look for another post with some pics soon with the results and reports on how it went.

If all goes well, George’s glider will be next on the list.  Wish me luck!

In the last 2 weeks I’ve had the Mustang up on 6 flights and put it back in “race ready” condition just in time for our annual Tim Mills Derby Days RC Airshow.  This is just a little wrap up of the updates I’ve made and issues I’ve had since building up a new wing and electrifying the Robart retracts.  I will come back and edit this post with a few added photos in the coming days.

Working more or less chronologically, I got the wing built up and the retracts installed along with installing the retractable tail gear in the fuselage.  All seemed to be working pretty well so I went out for the first flight.  It went well, with “Drag Racer 2” going through her paces just I remembered.  She flies heavier than anything else I fly but with no real handling problems or bad habits other than needing a lot of speed to handle well.  Fairly much what you’d expect from a big war bird.  Maybe the ailerons could be dialed up a bit but the rolls are probably pretty close to scale… maybe a second or a bit more to complete a roll??  I’ll have to check that and consider increasing throws on those.

This first flight, I kept the gear down and the landing was fairly uneventful with the exception of  a tendency to turn right as the roll out got slow.  Nothing that the rudder couldn’t correct.  The landing gear took the shock on landing  better than I expected.  A pleasant surprise.

Second flight a half hour later was a bit more exciting…  After the first couple laps I hit the retract switch and all three disappeared into the  bottom of the airplane as planned.  So far so good, except the plane wanted to climb rapidly.  At first I didn’t understand but soon the reality of removing drag and closing the majority of the large pockets in the bottom of the tail and wing set in.  The plane is just getting more lift and experiencing less drag… which equates to the tendency to climb.  That’s generally a good thing so why fight it.  Eventually, a couple flights later, I trimmed it for level flight with the gear up and just got used to pulling a little up when flying with the gear extended.

After a few high speed passes I decided it was time to land and went for the retract switch again.  A quick pass to check gear down and… uh-oh… only 1 main is down!  While having all sorts of awful thoughts about how a Mustang would land on no gear (22 lbs of airplane on the scoop… yikes!) or even worse with only one main gear I tried cycling the gear a couple times.  Eventually I had the two mains down and locked.  The tail gear also managed to jam part way down but I decided to live with that and brought it in smoothly again.  No damage and now it is obvious that the gear door is pivoting on the strut and getting caught on the edge of the wing inset.

Back in the shop to tighten and re-glue the doors and come up with a solution for the tail wheel jam issues. The problem seemed to be that the cables that steer the wheel go slack when retracted.  This allows the tail wheel to pivot around in flight and get caught against the side of the plane when the command comes to move.  After some consideration, I added some rubber bands to the assembly to hold the wheel straight when no servo linkage pressure is being applied.  This keeps the axle and wheel from contacting the insides of the fuse OR the landing gear doors when coming down.

Back at the field a few days later and it was time for flight 3 and 4.  These two flights went well and it was during these that the trim got adjusted to account for the wheels up “slick” condition of the airframe in normal cruising mode.  As I flew, I got more and more comfortable with the airplane and made some “photo” passes in near knife edge and about 20-50 foot altitudes as well as fast low passes, immelmans, loops, split S(s), aileron rolls… Pretty much anything you’d expect a Mustang could do.  Both landings were smooth with comments from a pilot who owns this same ARF (not modified and with the wire gear on) to the effect that I was making him look bad by coming in to land so smoothly.  I love to see a big bird do a nice landing so I spend extra time and effort to make mine look good when I can.

Also during these flights I noticed just how much slicker the plane is with the gear up.  I was expecting 2-3… maybe 5 mph increase in speed.  What I got was 10-12!  In a couple of cases the GPS on board said I had hit 113, almost 114 in a shallow dive toward the field.  Before anyone comments on the inaccuracy of GPS speed, I can tell you I have tested the GPS versus the Pitot tube type instrument and they are very consistently within 1-2 mph of each other.  Engine RPMs hit somewhere around 7500 at their highest which didn’t seem to harm the DA-50 at all.

Those flights went very well and the landings were nice with full flaps and just a click or two of power on landing.  Back in the shop I painted the mounting blocks to match the struts and added the guns to the leading edge.  Two .50 cal in each wing in this B/C model (unlike the 3 per wing in the D).  The guns I did a bit different this time.  I cut circles out of flat black and then circles out of those big enough for the gun barrels.  I then ironed these covering “donuts” onto the leading edge at the appropriate spots and then drilled in the donut hole so the gun barrels could be expoxied in place.  After all was complete, a little flat black paint to cover up the brass tubes from which they are fabricated and all is ready to go.  There seems to be quite a variance in gun installations in different Mustang models so these look good enough and much better than the factory glue on pieces.

About the only thing left for this bird is more flights and some added epoxy on a couple of cowl screw inserts that are walking out.  I’m actually getting past the knee knocker factor of flying this bird and starting to enjoy it for what it is.  Not my favorite or best flying aircraft, but very impressive in the sky with plenty of wow factor for the crowd.

 

Finally finished up getting the wing rebuilt and ran out of excuses to not fly the Redtail.  Perfect weather and the looming airshow at the field where I am expected to fly this bird were the final straws so the Mustang went to the field for the first flight with the new wing.

This time, the retracts were electrified instead of tied down in the extended position, the tail gear doors had been installed and the wing was short a few .50 caliber guns but otherwise just like the last time it flew.  The difference being that last time it flew I was coming off of about 10 successful flights, not the off-field landing that caused the need for a new wing in the first place.  Also that was toward the end of last flying season… it seems like a long time since I flew it last and I was having my doubts.  Not about the plane of course, but the pilot was another matter.

There were lots of questions bouncing around in my head.  Did I remember how to land this bird?  Which switch was the kill and which retracts and which one just made Tim salute??  Here are pictures from the two evening flights.  (All pictures courtesy of Steve Howard)

Tail up and just about to lift:

First pass with wheels still down…

A few passes later… checking to see if the gear retracted as planned.  Looks good and you can even see the green “ignition on” indicator light!

Then, of course, a high speed pass was called for.  After all, it hadn’t ever been this aerodynamically clean before!

And finally, you have to do a photo pass!  You can see the rudder working in this shot.

In all, two very successful flights.  There is a laundry list of issues to address.  First the right gear is rotated a bit outboard, causing a right turn as the plane slows to a moderate speed after landing.  Also, on the second flight the right main gear door got caught so the right main would not immediately come down!  I considered belly landing (ouch… ouch… ouch…) but a few cycles freed it up and landing was fairly uneventful after that.  The tail gear got caught a couple times going up and down.  Going to have to find a way to self center that when the cables that steer it go slack during retraction…  Later, also realized that a couple of cowl screws need some attention.  The inserts seem to be pulling out.  Perhaps from vibration where the exhaust rubs the cowl.  Seemed like with the gear up the plane wanted to climb!?  Just from a cleaner airfoil  or what I’m not certain but may have to mix some down with the gear up position to smooth that out.  A crop of small issues like this always seems to occur after the first flight or two so back to the shop for this bird.  All in all, I’m calling it a win with the retracts performing a bit better on ground handling and shock absorption than I expected them to.

Once all that is cleaned up I can install the guns back in the wings and do some other cosmetic work on the tail gear door hinges (white is not a good color for those).  The landing gear door blocks on the mains are natural wood color at the moment also.  Those will get some paint as well.  I’d really like to get a half dozen more flights before the big show on the 27th.  If the weather cooperates this week I hope to be able to be show ready by then.