For Part 1 of this article, click here.

It was the wee hours of the morning before I really made the firm commitment in my mind that the P47 had to make the conversion to Electric.  At the next opportunity I started the process.

First order of business was to pull all the gas accoutrements from the airplane.  First, I pulled the prop and cowl and started stripping out the gas motor mount, ignition and the supporting switch, battery etc…  I knew a guy who was looking for a  DLE-20 so I made him a deal on the engine to help finance the needed items to complete the conversion.  I had the motor but needed a speed controller and maybe some additional lipo packs.

As soon as all that was out of the way it was time to explore the “hidden hatch”.  For reasons that are beyond my comprehension, Top Flite built a hatch into the top of the P47 (and other models in this line of ARF warbirds).  They framed it out in ply, put magnets in place along with pins to hold it in place… and then put a solid balsa sheet skin over the entire nose (including the hatch) and covered it with no markings or indication that it existed.  Nor is it documented in any way in the manual!

With no guidance it became quite the task to figure out how to outline and cut the hatch free.  What I eventually settled on was to take a pair of forceps with an extremely sharp needle locked in it’s jaws and reach down into the wing saddle and force it up between the two plywood plates at each end and side of the hatch until it emerged through the covering.  By doing this repeatedly, working my way around the hatch perimeter I outlined the hatch on the covering.  Then while holding my breath, holding my head at just the right angle and sending up prayers to the modeling gods (a more fickle lot I have yet to meet) I took an Xacto knife and inserted it into one of the pin holes and slid it by feel between the plywood plates.  Working my way around the perimeter of the hatch, I managed to slice my way through the vast majority of the sheeting.  With the judicious use of my razor saw, I got the hatch loose with only one problem… I managed to cut through the pins at the aft most part of the hatch! 

Don’t worry about the wasp decal… I was planning on ordering replacement graphics anyway!

As you can see it wasn’t a perfect cut but it came out well enough!

   

Luckily, I had on hand an appropriate sized dowel and replacement of the pins proved to be a fairly minor task.  I would later go on to add a hatch latch on the leading edge of the hatch… or at least on the new one I had to build after I found out the hard way that those magnets just aren’t strong enough!

Next time I’ll discuss the power system choices I made and how that is working out.

To see the next post on this topic click here.

 

One of the first things I’m always concerned about with an RC airplane is just how easy it is to get flying once I get to the field.  I really don’t want to be fiddling with 15 bolts and nuts that require special tools to attach, nor do I want to have to crawl around on the ground to assemble the airplane, etc…  At least not if I have a choice.

With the H9 Carbon Cub I felt like it was going to just be to “fiddly” to assemble as designed from H9.  The wing attachment method with screws that would have to be put in from the bottom of the wing, up in a hole and then adding in the wing strut bolt attachments, the battery placement and mounting method which was going to have to be done reaching under the wing and into the cockpit area and then a screw inserted to hold it in place??  Did they really think I was going to do that for every flight?  I found it frustrating to do with no windows in place and the cowl off!  I certainly didn’t want to try this reaching in only through the door on the side of the cockpit.

All of this screamed out for some modifications so here is what I went with.  First, I decided that I wanted to reverse the wing mount tabs.  IE. I decided to permanently mount them in the wing and make the body end be the area where any attachment task was done.  To accomplish this I needed to remove the tabs from the body.  This was fairly quick and easy with the proper application of a ball peen hammer.  Here is one still mounted in the fuselage.

They have a shoulder on the inside of the fuselage so you need to push them into the plane body if you want to remove them.   A few raps and they pushed into the body and were easily removed.

A tiny bit of wood came off with them but not enough to cause any concern.  I then used the phenolic tab material as a pattern to make replacement pieces out of similar thickness aluminum.  Since I want them to extend a bit further into the fuselage so I can attach them on that end, each of mine are about 1/2″ longer than the originals and don’t have a tab.  I did drill the hole so I could attach them to the wing (I just intend to only do this once)!

Once all cut out and the hole drilled in each I did some sanding to round the corner and cut some slots into them so I would have a way to pull them together to keep the wings from sliding on the wing tube and opening up a gap between the wing root and the fuselage. 

Even with this mod, I didn’t want to have to reach up into the cockpit through the door and put screws in, rubber bands on or attach a tie wrap or whatever.  Between this and the need to swap out batteries I decided I wanted to have a removable top window.

This meant I needed to build some sort of frame to mount the window in and create a hatch assembly.  This sounds easy until you realize that the top of the cub is a curved surface AND the opening narrows as it goes toward the rear of the airplane!  So first step was to make some custom shaped window frames for each side.  I began by tracing the shape onto some light card stock (sometimes having a greeting card crafter across the shop comes in handy!).  I then proceeded to attach the template to some wood and then cut and sand to shape.

I then used some of my finer TLAR engineering skills (That Looks About Right) to make a rounded cutout in the bottom of these pieces in order to provide clearance around the wing tube.  After that I cut a couple of appropriate length 1/4″ square sticks to use as the front and back.  Each of these is custom of course due the aforementioned narrowing of the opening.

Once that was all completed and some careful fitting done, the frame was assembled (I laid all the pieces in the place in the top of the fuse and used CA to tack glue them together then removed them from the airplane and finished the gluing process). 

After a test fit of the full (one piece) window, I carefully marked and cut off the material for the top window.  Before attaching it, I colored the frame with a black permanent marker and then glued and clamped the window material to the frame with canopy glue.

This was allowed to dry for a few hours and then the clamps came off and I added a bit more glue around the inside edges to make sure it was not coming off anytime soon.  From there I started working on ways to mount the frame to the top of the airplane.  First I made a tab out of a couple pieces of popsicle stick and glued it to the front bottom edge of the frame at an angle so it would catch the front of the fuselage.  This prevents the front from lifting.  You can see this here.

I had to just do a bit of adding a layer of popsicle stick and then sanding a bit off to make it have a close enough fit.  More black marker to cover up the wood grain took care of hiding it.

The final stage involved another stick of wood on the back edge of the frame to add some “meat” to the frame (my original 1/4″ frame I felt was just to small) and allow for the attachment of a “handle/antenna” for easy removal of the top hatch when needed, along with a block of wood to house a magnet to hold down the trailing edge.  Adding some black pin striping around the edges to give it a truly finished look was the final step in building the top window/hatch.

After all this was said and done I decided with this easy access I could use a turnbuckle to hold the wing panels together.  Its very quick and easy to put in place and because of some fitting issues at the wing root of the port wing, I needed something to put a fair amount of pressure on to hold the wings where they belong.

Here are a couple shots showing the final product.  I feel like it came out pretty decent and I wouldn’t have been happy with the original setup.

Next time, I will discuss the bottom air vent I decide to add and a couple of other minor adaptations I made.

 

A couple months ago my flying buddy Gary picked up a Hangar 9 Carbon Cub 15cc ARF that someone else had begun assembly on.  After he had done a bit more work on it he decided it wasn’t for him so I acquired it in turn.  I have always thought it was a beautiful airplane and wanted one so while I’m not sure how good a flying craft it will be, I decided to give it a go.

First, I had to decide what I would power it with.  For me that was an easy decision.  I doubt I will ever have another glow engine… expensive to run and messy.  Other than having good memories that pop up when I smell hot glow fuel, there’s just no good reason I can think of to put one on an airplane these days.  I may do another gas powered RC airplane one day, but not glow.  It doesn’t hurt that I happen to have a slightly used Power 60 and 100A Castle ICE sitting in a drawer.  Decision made, I started going through the manual and deciding what still needed doing to get it flying.

In addition I needed to go over the airplane and see what the previous owners had done that might need some attention.  I also started researching the airplane online and noting what I might want to add or modify.  So far I’m still not quite to full flight status!  Like most of my builds, this one has been interrupted, delayed waiting on some parts or just to give me time to decide how I wanted to do things, and has taken about 10 times as long as the manual suggests!   I’ll start to add some articles soon detailing the changes/issues and challenges I’ve had getting the Cub ready to fly.

 

It seems like the work on the Balsa USA Cub never ends.  Some of it is just that the BUSA kit seems to be more complicated than most and the way the designer/manufacturer chose to do things sometimes makes no sense to me.  Also, since I got this as a partially constructed kit, I’m having to go back over everything to see what parts the previous builder changed, skipped or just didn’t follow directions well!?  Of course the fact that I’m “converting” it to a super cub is not helping the process along either!

One of the things I have spent significant time on concerns the wing attachment methods.  The original plans call for a couple pegs through the wing roots and two bolts as well to hold each panel in place.  In addition the struts are load bearing.  They are bolted to the ply plate that makes up the fuselage floor and screwed into hard points on the wing.  When I first tried to assemble them I quickly found the whole process to be frustrating and overly difficult.  Getting the wings in place and holding them there while installing the bolts was difficult and that was without any windows in place!  I can’t imagine what a PITA this would be once the plane was all covered and the windows all in.  I quickly realized something had to change.  In addition, it seemed entirely possible to cause some damage to the plane while installing the wing struts as the entire weight of the wings at that point is hanging on the wing roots and the structure between doesn’t seem all that strong.  Thus the need for load bearing struts!

So I first added a wing tube to each wing and fashioned some bracing inside the top of the cockpit area to give it some strength.  Now there is something a bit more substantial to hold the wings while the struts are being installed at the flying site.   You can see the aluminum tube in the wing center joint and inside the wing panels below.  There is a carbon fiber tube inside.

The strut attachment method seems a bit ridiculous as well with no concession to ease of installation or transport.  The vertical wires that connect to the wing mid-point don’t seem to be movable or easily removable so transporting the struts looked to be a pretty interesting prospect.  Add to that the directions for attaching the struts to the wing hard points uses wood screws… which to me is just a uniquely bad idea.  How many times reassembling this bird before a screw is over tightened, stripping the wood and weakening this critical attachment point??  I understand these kits are designed to be very scale like and that most builders are going to modify all of this to make it even more so.  Maybe they don’t intend to fly the plane all that often… but for me, if it isn’t reasonably simple to assemble when I get to the field it will likely get little flight time and become a hangar queen.   I’ll take slightly less scale like and more functional and easy to get in the air over scale in this case.  BUSA might as well just say “figure out a method that will handle the stresses and that you find acceptable to assemble” , and leave it at that.  The directions they do provide seem to me to be a poor attempt at best.

After a lot of fits and starts and coming up with several plans and then rejecting them I came across some struts and connecting hardware from a 1/4 scale clipped wing cub at a swap meet.   The struts were far to short but I cut off the ends in hopes of using the attachments.

I don’t know why he had them but the gentleman had 2 or three sets so I picked up a set for myself.  I looked at them twice with great regret that they were for a clipped wing cub but then figured if nothing else I could use much of the hardware.  Once I looked closely at the hardware the wheels started spinning and I realized the hardware alone was more than worth the price.  So I created some Frankenstein struts.

Below is a snapshot of the mid-wing attachment point.  Using the threaded “eyelets” with threads tapped into the hardwood blocks in combination with the hollow aluminum tubes with built in attachment points, a 4-40 bolt and nylon insert nut makes for a secure attachment point.  The tubes and wires were trimmed and epoxied together after adding some grooves to the wire to insure the glue gets a good grip.

On the other end of the wire, I used some nylon landing gear wire straps and #2 screws to create an attachment point that is both strong and allows for an easy pivot point for storage.  This shows them pivoted down against the struts for storage.

 

At the outer attachment point, the main strut connections are bolted to the hard point with 4-40 bolts and blind nuts.  The ends of the wood struts were trimmed to fit inside the aluminum tube ends as well and attached with glue and screws to the wood strut ends.  This took extensive trimming and measuring to get the correct length and support the wings in the correct position.  Each is somewhat custom!  The nice thing is the ends of the struts that I recycled have a threaded rod at each end for fine adjustment.

 

I attached the outer aluminum ends with expanding gorilla glue and some #2 screws to “pin” them in place.  Now I have a nice pivoting attachment point that I don’t intend to disassemble often as the struts can be pivoted down to sit flat on the wing for storage.

Each strut, once adjusted on final assembly, should take only 1 bolt at the attachment point on the bottom of the body and 2 more at the mid-strut attach point in order to easily assemble or disassemble the aircraft and still provide plenty of needed support.

Combined with the wing tubes, which require a single bolt on each side to attach, the entire assembly process shouldn’t take more than about 5-10 minutes and I expect it to be both strong and fairly straight forward to accomplish.

There is still a long list of projects to get this plane ready to fly, some small like hinging of the wing surfaces, and some large like getting the cabin windows, windshield and door assemblies all finished.  More updates soon.

My local hobby shop, Hobby RC, got my replacement body and decal set in quickly and so the process of making this craft flight worthy again could begin!

Immediately upon unpacking a couple of things became obvious.  As you can see here:

The decal set I ordered would not be necessary.  Unfortunately the picture on the web site showed the spare part without the graphics.  I’m happy this is the case but could have saved $15 if I’d known.

Next I noticed the rudder was not attached and I had no idea to this point how it was attached… the original came on my plane… I’m pretty sure…

Turns out the rudder just clips onto the body by the use of built in plastic clips and pins built into the two parts.  You simply push it on and it pops in place…  Couldn’t be much simpler.

After screwing on the two halves the elevator with the 4 black screws.

I pushed the rudder on and started flexing it back and forth when I noticed that it didn’t allow for much throw (I had been thinking it needed a bit more) plus I noticed that it tended to flex the elevator joiner, resulting in some deflection…  that had to change.  So taking advantage of that easy removal, I popped it back off and opened up the pass through slot with a sanding drum on my electric rotary tool.  You can see how tight it is here in the before photo:

Quite a bit of material needs to be removed to get a significant amount of throw AND keep the pressure off the elevator joiner.  Here’s the old and new with the modification.

And here is what it looks like installed.

 This allows for the maximum throw allowed by the factory servo and linkage setup without binding.  Sliding the push rods back in place and installing the servos on the rails was pretty straight forward.  I notice the servos have no rubber grommets on the tabs… though I suppose in a foam body electric, vibration problems are fairly limited so no need.

While I was working on the tail, I flipped the plane over and went to work reinstalling the retractable tail gear.  Only something was missing!

The plastic insert that everything mounts into was not in the new body… time for some surgery on the old body again…  You can see here that it takes a lot of carving to get this thing out.

And here is the piece that comes out.  It takes a little cleanup from here.  You need to get all the foam off of it to easily insert it into the new body.

After getting the plastic insert into the new body, mounting the servo followed by the retract itself was pretty straight forward.

Mounting the servo and retract outside the aircraft is more straight forward than it was taking it out while still inside the tail of the plane.  Route the wires (easier if you have “grabber” like the one you see here) and with a little glue on the contact points with the foam just slide the assembly back in place and we are back in business.  

Reattach the doors and springs (a little bending/adjustment is likely needed) and everything goes back together fairly easily.

Next I reinstalled servos and the control board with it’s associated plywood tray inside the fuselage as well as the connector boards in the wing root.  You’ll want to check your notes or photos on which wires plug into what as the labeling is helpful but not completely obvious.  Once again I ran into a small issue where my notes and pictures were insufficient.

Here is the starboard wing root 

Note the one socket is closest to the trailing edge of the wing.  As you reinstall the matching plate in the body, be conscious of this and note that the port side is opposite…  I just “assumed” that both would be installed similarly and it turns out not to be so.

Most everything else went back in with no issues, though I encourage you to take copious notes and photos if you have to do this for yourself.  It will help immensely to guide you in the rebuild, knowing which screws to use, etc…

As I was assembling for final adjustment of the servo linkages and testing I found one more casualty.  Here are two of the wing screws…

As you can see there was a bit of force exerted when one of the wing tips found the ground.  These bolts are a little bit soft (which worked in my favor in this case!) so I was able to simply use some padding around the bolt in order not to mar the threads and bend it back into shape with pliers.

I made a final “rebuild” step by peeling the custom graphic for my crew chief (my Grandfather) and successfully reapplied it to the the new fuselage.  Welcome home Grandpa! 

While the P-47 was in the shop, a few additions were also made.  With the addition of a telemetry module and associated sensors (GPS, G Force and Voltage sense wire…) I’ll be able to keep a better eye on my battery pack voltage, ground speed and other interesting tidbits.

This last weekend we had a nice event at the club field during which I got in 6 or 7 flights.  After a bit of elevator trim during the first flight, the Bonnie proved she was back in peak form.  Her pilot took another flight or two to get back in the groove…  I did make sure that the battery was securely attached to the battery tray before each flight and I may add additional measures to be sure the whole assemble does not leave the plane prematurely.  For now just being sure the straps on the tray also engage the hook and loop material on the battery seems to be working.