Sold the P-47

I sold my P-47 on craigslist today.  I liked it, but for whatever reason, it wasn’t my favorite to fly and I’ve got my eye on something else … but I need to free up some space first … !  I really enjoy flying my PBY though … I need to set up a category and post a few pictures of that soon!

More wing related repairs

I encountered two more issues that I needed to address:

  1. The cheap retract servo stripped out.
  2. The rear wing hold down threads stripped out.

I replaced the retract servo with a much higher quality hi-tech metal gear servo and spent about 10 minutes fiddling with end point adjustments and linkage lengths to try to get non-binding operation and minimize the servo buzz.

The stripped rear wing hold down threads was a bigger problem.  I tried to glue a nut to the back to replace the cheap plastic threaded plate, but just made a mess of things, got glue on the threads, etc.  Just a big mess that was hard to deal with due to it’s location and inaccessibility when things are lined up and put together.  So I went old-school — found a “blind” or “t” nut (like you use when kit building to anchor firewall mounts, wing mounts, etc.) and found a matching non-metric screw (my hardware store doesn’t sell metric t-nuts.)

So that’s it — no pictures, but the repairs are complete and the bird is airworthy again — at least until the next cheap part strips or breaks. 🙂

P-47 Wing Repair

The Hobby-Lobby “Hun Hunter” P-47 seems to have a small design flaw.  Because of the size of the wheel well required for retracting the gear, there is not a lot of foam material along the leading edge of the wing in this area.  At the thinest point, it’s pretty thin. The wing is subject to cracking in this area — starting at the leading edge and proceeding through the middle of the wheel well.  There is a carbon spar in the wing so the wing isn’t in any danger (I don’t think) of coming off in flight, but it does create greater flexing and makes me nervous.

It seems that any landing that is less than perfect has potential to crack the wings.  I can grease in a sweet landing now and then, but once in a while everyone bangs in a little harder than they intended.

In an attempt to repair this problem “permanently” I cut two small pieces of glass cloth, about 5/8″ wide by 1 – 1/2″ long.  I then used a mixture of slightly thinned 12 minute epoxy to glass in this cloth.  The picture below shows the outline of the tape along with the rough location of the crack (in green.)

The tape blends in pretty well once the epoxy saturates it, although the epoxy will cure a bit yellowish.  This takes away from the perfect scale appearance of the aircraft I’m sure, but what are you going to do?  I want to be absolutely rock solid safe in flight.

Hobby Lobby P-47

Introduction

Hobby Lobby recently introduced a neat P-47 warbird model.  It has a 40″ wing span, 4-channel flight control, retractable landing gear, and comes receiver ready.  It includes servos, motor, speed control, and even a suitable battery.  All you have to do is some basic assembly, install your receiver, and you are pretty much ready to go.

Construction

Here are the tail surfaces as they come out of the box.  Everything is pre-hinged.

Here is the fuselage as it comes.  The motor and speed controller are already installed.  Servos and linkages are installed.  Even the cowl comes pre-installed:

Here is the wing.  As you can see, the two halves are already attached.  The landing gear and retract system is already installed.  The servos and linkages are also installed and the control surfaces are hinged and attached.  The wing flaps are not operable by default, but I noticed there are servo mounts molded into the wing and it would be a 30 second job to cut the wing flaps loose and hinge them.  So if anyone really wanted to add flaps for additional realism, it should be a straightforward mod.  The aircraft definitely doesn’t need them though … it slows way up if you want it to and flies very stably at slow speeds.

Here is a close up of the machine guns on one side.  There are tons of little details built into this aircraft!

The prop was a neat surprise.  It’s an operational, scale, 4 bladed prop.  The prop tips are painted yellow and it really looks neat when it is stopped and when it is spinning.  It includes a scale prop hub and the final result looks really sharp!  I’m sure the prop is not the most efficent choice, but it looks great, and works great so I’ll run with it.

After hardly any effort or time, I ran out of things to do and the aircraft was done.  It’s midnight though so I took it out in my driveway for a pre-maiden photo shoot.  She really looks sweet.

Here is a good view of the business end.  You can see the scale prop and the retract system.  Very nice!

… time passes …

The next day after I finished the airplane we got a giant snow storm here in Minnesota.  Blast!  I figured it was still late fall, wait a few days and this first snow fall of the season would melt.  But unfortunately, mother nature had other plans for us.  The temperatures dropped, more snow came, and more, and more.  The RC club field was buried for the winter. 🙁

Fast forward to April.  The snow has finally mostly melted and the road to the field has dried out enough to be passable with normal street vehicles.

The Maiden Flight

I snuck out to the flying field for an early lunch break.  The winds were relatively light @ 5-10 mph.  But they were at a 45 degree cross wind though which was the only minor complication.

Here are some pictures before the first flight.  I also have a battle tested Hobby Lobby MiG-15 that uses pretty much the same battery so I brought it out as my “backup” airplane in case I found a problem with the P-47 and couldn’t fly it.  I hate wasted trips to the flying field!

She’s just as pretty in the grass in the morning as in my driveway at midnight. 🙂

Maidening a new airplane can get the butterflies going, so I always try to tell myself that these things are designed to fly.  They want to fly!  It will fly great!  And that’s the truth.  I had to dial in several clicks of right aileron and a couple clicks of up elevator and I was grooving around the sky.  The scale prop doesn’t offer blazing top end speed, but it’s solid and gives good power.  There is plenty of HP to climb very agressively.

Retracts!

I’m especially excited about this P-47 because it is my very first RC model airplane with retractable landing gear.  A WW-II warbird really needs retractable gear.  It just doesn’t look right flying around with the gear down, and if you build it with no gear at all, then you have to hand launch and belly it it.  The retracts worked great with two lessons learned:

  • I mentioned earlier I had quite a significant cross wind.  On my very first landing I mismanaged my rudder and my slip and touched down with quite a bit of side load.  This collapse the upwind gear leg and I skidded to a stop.  Dohhh!!!  That left a couple scratches on the bottom of the aircraft, but didn’t seem to damage the gear (it just popped right back out when I picked up the airplane) and the big scale prop was safe too.
  • On the second hop, the retracts suddenly stopped working.  Fortunately they were stuck down.  I landed, this time being much more careful with my cross wind technique and inspected the gear.  In my lap, the retracts worked perfectly.  I took off and still couldn’t get them to retract in the air.  Then I took a quick cheat peek at my hands and realized I was trying to toggle the wrong switch.  Dohh!!!  That’s what I get for buying a 7 channel transmitter with about 20 levers and knobs and switches on it.  Once I found the right switch the gear worked perfectly again. 🙂

Nose Overs

I read online that this design has a tendency to nose over and guys were busting up their scale props (and then complaining because they were out of stock.)  So in my test flights I was very careful to hold up elevator at the start of the take off run and touch down with a heavy dose of elevator dialed in.  By the way, this P-47 has awesome slow flight characteristics.  If you are careful to bleed off your speed and flair at the right time, this thing totally slows down to a walk and drops in for a nice 3-point landing.  I need more practice, but on a nice light wind day, I think there’s potential for some really really sweet landings.

Wing Crack

After my first battery was expired, I picked up the aircraft to walk back to the pits.  I noticed a crack developing in the wing foam on the bottom side of the wing, close to the wing root between the leading edge and the wheel well on the right side.  The spar was solid, but there was more flex there than I liked to see.  Bummer, done after one battery, but still happy with how things went.  I’ll file this under “shaking out the bugs”.  Hopefully a little glue will secure the foam and I won’t have any more problems.  It’s something to watch though. Update: the crack was a little more extensive than I first thought … it appears to be from landing, but I don’t recall banging it in real hard. Oh well, I glued it together and hopefully it will hold.