Category: My Fleet

I’ve been spending a bit more time working on the replacement wing for my Giant Scale P-51 Red Tail Mustang.  After cutting out the covering appropriately and recovering the tips in red and adding the yellow stripes I started working on linkages.  When I went to attach the control horn to the port side aileron I discovered that there was no hardwood mounting plate on the bottom of the aileron to mount to.  Of course I did so by drilling a hole and then realizing the drill went in far to easily!  Stopping to consider I realized there was an appropriate right and left aileron and I assumed I had picked up the wrong one…  (please imagine appropriate cursing as I realized I had already applied the small red and larger yellow material to the tip of what I imagined was the “wrong” aileron, not to mention the new hole I had just drilled)

I then went to retrieve the other aileron and quickly determined that it was an exact replica of the one I had already worked on…. not good.  As you may have figured out for yourself by now, they should NOT be duplicates.  In particular the port side aileron should have a hardwood plate in the appropriate spot to mount the control horn (close to the inboard end of the surface on the bottom).  The starboard side aileron would have a similar plate but because these surfaces are tapered the two are mirror images, not duplicates.  What happened, it appears is that I have two ailerons that would both work on the starboard side but not the port side.  Here is a picture of the two ailerons side by side (you can see the half-circle hardwood plate through the material if you look closely).

I double checked the flaps and they are fine but the ailerons I have are not.  Either the plate was simply installed on the wrong side or I have two starboard ailerons.

Not caring for the option of calling the hobby shop and/or Top Flite with the inevitable delays that would ensue before they came up with a replacement part, I decided I needed to correct this issue.  Don’t get me wrong; they are all good folks and I feel confident they would do all they could to help resolve the issue but what are the chances they have an extra port side aileron laying around?  It took months to get the replacement wing the first time.  The balsa is certainly not going to be sufficient to hold the control horn screws securely for this big heavy bird so some surgery was in order.  It was time for the “modeling” part of the hobby!

I located a small piece of 3/16″ aircraft ply from another project and cut a nice square out.  I noticed my old wing used square insert and the new one uses the half circles so I figure either works as well and I can cut squares easier than circles!  I then cut away the covering material around the area I had to work on and used the ply square as a template to mark the surface.  Using an X-acto knife I cut around the block and then carved away balsa until I could fit the ply block in place.

Once satisfied with the fit I mixed up some 15 minute epoxy and coated every surface that would have contact with the new block with epoxy.  Once in place I wiped the excess epoxy off with alcohol and set the piece aside to dry.  With some minimal sanding and a bit of patchwork covering I should be able to get back to making some progress tomorrow!  Here’s the repair awaiting some recovering work.

One lesson to take from all this is to keep the ailerons,flaps and whatever other parts of your ARF came partly assembled or packed together… together.  If the ailerons had been correct I still might have picked up the wrong one and run into this same issue.  Marking them might be a good idea if you are going to be disassembling and reassembling things.

I wonder if somewhere out there is someone with two starboard side ailerons on their Giant Scale P-51??

 

After my off field landing I decided to assemble a replacement wing.  I’ve been working the replacement wing a little at a time.  The latest project was to attach the wheel pants/doors to the Robart retracts (electric conversion).  The manual directs the builder to glue these wheel pants on with Epoxy but that seemed like it could be a bit weak.  Maybe I’m just overly cautious, but I thought something a bit more secure might be in order.  I couldn’t help but think if it didn’t pop loose between the attachment blocks and the wheel pants it would surely vibrate off on the other end between the blocks and the struts themselves.  Here is a view of my “improved attachment method”.

I sanded the back of the fiberglass door and the strut then used epoxy as directed but added some wire to hold it tight against the strut.  In order to keep the wire from causing a gap I had to cut a couple of grooves across the top of the blocks as well.  Here’s a view of both blocks in place.

I used one continuous wrap of wire rather than two separate wraps, thus the crossover you can see on the lower end (right).  That seemed like it would, at a minimum, keep the blocks attached to the struts but what about the wheel pant attachment to the blocks?  On that end I decided that a button head screw would add at least a bit of extra hold while also holding things in alignment while the glue hardened.  Below you can see the view with the gear up.  You can clearly see the two button head screws (#2 x 3/8″ I believe).

Hopefully between all of these modifications the wheel pants will stay put.  Lots more work to do but with the gear in and pants in place it feels like I might be closer to finished than just getting started.

After the “off-airport” landing of my Mustang a while back, I decided that it was time to get the retracts working.  I had them in the plane (locked down) for several flights and they did not appreciably change the flying characteristics of the plane and seemed at least as capable as the wire gear in absorbing light to moderately bumpy landings.  I hope I’m beyond hard landings unless a mechanical issue arises so hoping I can avoid any truly hard landings in the future.

Of course, these retracts were bought in 2004 and were built to be run by air but I had pretty much made the decision when I assembled the bird that they were going to have to be converted to electric use.  The area where the air tank would normally go was filled with padding and batteries and pretty well buried anyway so the conversion was a given if retracts were ever to be functional.  The retracts got a little minor repair and have been removed from the wing anyway since a new wing is on order!  The current wing is fixable but a fair amount of crushed wood and cracks in the main spar convinced me it would be easier and maybe smarter to just get a new one.

After taking a little time to replenish the piggy bank, I ordered the complete main and tail wheel conversion kits from Robart via my favorite local hobby shop.  A week or two later I had them in my hands and I sat down at the bench to get started.  This will give you an idea what the kit looks like for the mains.

 

 

Here is what the starboard main looks like before the conversion and then after….

I found the instructions to be above average but the one part that was not spelled out clearly is that there is a difference in the two replacement trunnions.  At least I didn’t notice it being mentioned anywhere.  There is a right and a left and if you use the wrong one you end up with what is pictured above!  Yep, I had a 50/50 chance and I chose unwisely.  Oh, the retract works great… if you want the wheel to thrust upward through the wing instead of dropping down below it!!  Hah!

So I got to take it all apart again and do it a second time.  I was getting pretty good at it by then and hadn’t yet put the thread lock on it since I’ve done a bit of modeling before and pretty much knew that I’d mess it up somehow.  It took another 20 minutes or so but then all seemed good and worked pretty well… mostly.

The next problem I had was that occasionally one of the retracts would slow down to about half speed or just outright stop completely.  Since this system was designed to stop at the end of travel solely by sensing the increase in current draw caused by the increase in physical resistance, I concluded that the controller has no way to know the difference between end of travel and any other major increase in mechanical resistance.  I tried a little lubrication (WD-40) and that certainly helped but one retract would still stop in mid stroke on occasion.  After loosening the screws up a bit and exercising things I re-tightened and apparently the better alignment that resulted has resolved the issue.  I still have not applied thread lock as I’m saving that for the final install once I insure everything is well when they are mounted in the new wing.  Unfortunately, Top-Flite has not been as quick to send out a new wing as Robart was at sending the conversion kits so this last test fitting will have to wait for a while yet.

The tail wheel kit is much simpler.  Here is the kit as it came out of the package.

After the mains, the tail gear presented no challenge at all.  The only gotcha, which IS clearly spelled out is the possibility to set the controller to the wrong “type” for this retract with the possibility of burning out the motor.  Read carefully and follow instructions and you should not have problems.  I didn’t!

One final warning is that the actuator wires that enter near the clevis pin actually interfere with the insertion of the pin.  You can see the issue here.

A bit of judicious wiggling and a bit of push on the wires to help them clear the pin is all that is necessary to avoid the wires and since they are protected with a sleeve of some sort it does not appear that rubbing will be a problem down the road.

That’s about all there is to say beyond what is clearly documented in the instructions that come in the kit(s).  For about $300 you get what seems to be a bit simpler system which should result in some improved reliability.  I have heard that some are unhappy with the ~10 second time for the gear to fully retract or extend but I like the smooth action better than the usual slap and clunk actions I have seen from many air systems.  This time can be somewhat decreased or increased by feeding the system higher or lower voltage.

I plan to feed mine direct from the flight battery/receiver voltage as the system uses little current and I am carrying 2 x 2300mah A123s so battery capacity is not a big issue for me.  I supply the ignition from these same batteries using an Ultra IBEC and even so I’ve been flying 6 or more flights between charges with no issue.  At worst I expect to charge every 4 or 5 flights with the new added load.  I’ll keep an eye on battery capacity and usage for a bit to see how that goes.

 

This is my Wildhare Slick 540.  The basic stats are as follows:

Wing Span 88″

Length  ~82″

Weight ~18 lbs

Powered with a DLE-55 and Pro-Flow Cannister and turning a Falcon 23×9 (or sometimes a Xoar 23×8 laminate).  Here’s what it looks like at the moment.

Here’s a shot of the inside which has a few interesting features as well.  As you can see I’m running one of the water bottle type tanks.  This one is manufactured and pre-assembled by B & E Graphix.  So far it has been a great tank.  It’s significantly lighter than the standard type tank and the (I think felt) clunk does a great job of sucking up every drop available.  Moving back behind the wing tube there are two A123 2300mah 2S packs for extremely stable power.  On top of them at the top of the photo is my ultra IBEC from Tech-Aero and nearer the bottom is my TM1000 Telemetry module.  Hooked to that and velcro’d to the top of the wing tube is the attached GPS sensor (there are other sensors including temp, ignition voltage, and 3 Axis G Force).  Further back is my Spektrum 9110 PowerSafe receiver with all 4 remotes scattered about.  Behind that you can see the pull-pull system for the rudder which is handled with authority by the Hitec 7955TG

This is without question the best flying plane I own or have ever owned.  It’s completely honest with no bad habits and is as close to a “go where you point it” flyer as anything I’ve ever seen.  The combo is reasonably quiet and has plenty of power thanks to the engine, prop and canister combo.  It will climb straight up forever and fly at least sportsman level IMAC on 100 plus degree heat index Indiana summer days…  It may be able to do more but it needs a better pilot for that.  😉

Like every aerobatic airplane I’ve ever seen or heard about, it benefits from a few of the standard mixes to perfect it’s capabilities but unlike some I’ve flown, it can fly quite well without any of them.

Unfortunately Wildhare like others in the market, quit ordering and stocking the big planes due to the slow economy in the past few years.  That downturn appears to be reversing, so hopefully they will get back in the market soon before the market moves on to other folks who are already shipping new competing products.

 

Continued the investigation tonight.  Set the body in my trusty PVC holders on workbench #1 and started examining from the front.  Pulled the cowl and found a couple minor issues… One cowl screw insert coming loose, ignition box moving a bit, but no smoking gun under the cowl.  Even pulled the plug and examined.  It actually looks like I have heard it should.  Sort of uniform dark grey.  Gap looks fine and no carbon buildup obvious.  Top of the piston still nice and shiny as well.  All linkage and tubing plus the telemetry sensors and wiring looked OK.  I then decided to skip an actual ignition spark test for the moment and moved on back into the wing saddle area.  Again nothing obvious so I turned on the plane and started looking to see if (as I thought) the ignition voltage sensing is beyond the kill.  The plane died quickly like that occurred but the telemetry didn’t show the ignition voltage loss.  This all worked as expected but it brought to mind the idea that maybe I had a throttle curve that brought the throttle below idle or some sort of misconfiguration of a mix that would cause that.  Looking at the radio yielded nothing but when I moved the throttle back and forth I saw some odd movement and looking more closely I found the culprit.  Here is the problem:

With this screw backed out this far the adjustable arm can end up extending enough to cause the throttle to bottom out and shut down the engine.  As you can guess, I will be coming up with a different type of connection.  I know, some folks will say this type of connection in a big gasser is just stupid to start with, but with so little force required to move the throttle I was not worried about torque causing slippage or the arm bending or any of that.  What I obviously should have been concerned about was vibration loosening the screw!  I will probably replace this linkage with a standard threaded clevis (once I solder on a threaded coupler) and a standard servo arm… non-adjustable this time…  A drop of something to keep the screw in place might be used as well.  Perhaps nail polish or the like.  I don’t think thread lock works on nylon!

Obviously its hard to be happy about a crash but the good news is the damage seems to be limited to my pride and the wing.  My pride will recover… its a nasty bruise but they heal.  The wing is not that difficult to replace, and not very expensive in the grand scheme of things.  The better news is that I now know what caused the crash and it is easily rectified.  I was hating the thought of fixing all the damage and not being able to figure out a cause.  That would really make me paranoid and give me no confidence to fly the plane again.  Now I’m back to looking forward to it!

 

Pulled the landing gear and servos out of the wing this evening.  Port side gear bay and main spar and ribs took the brunt of the damage.  Cracks and buckling apparent.  Would be difficult to fix.  Would need to re-manufacture at least one rib and remove and re-web the main spar.  I imagine parts of it are cracked or broken as well.  The other side the top sheeting and some of one rib is crushed.  I am fairly sure I will just order a new wing this fall and reconstruct over the winter.

Both retracts had some flexing/bending of the mounting ears.  The starboard side was bent worse as you can see here.

Some hammering against the anvil/vise seems to have straightened those out pretty well.  I don’t expect the retracts are actually hurt at all.  They seem to operate smoothly and the struts compress as before.  Best I can tell everything is pretty straight again now.

I need to carefully inspect the fuselage but on first inspection it looks unhurt.

First look through the telemetry data has nothing significant to help pin down a cause.  Both the pack voltage and ignition voltage stayed in range both before and after the engine quit.  Overlaying the altitude and RPM graphs it is pretty easy to see when the engine plummeted in RPMs over a few seconds, ending at zero!  I will have to carefully examine the wiring beyond the sensor, check the ignition itself as well as the plug, the hall sensor and of course the fuel system to see if I can determine a cause.  The log showed no signs of problems and even if it had gone to failsafe the throttle would have simply gone to idle.  I will confirm that too but don’t believe it would have quit if I took a hit and it doesn’t appear I did anyway.  There was plenty of fuel in the tank when it quit so will be sure to check the plumbing as well.  Still a mystery for today.