7. Top Flite P-47D Build Log – DLE-20 20cc Gasoline Engine Conversion (R.I.P. Updated 6/12/2011)
Scroll down to read the DLE-20 20cc Gasoline Engine Conversion
6/5/2009 – UPS delivered the P-47 today. It’s in a huge 49″ x 17″ x 17″ box. Unpacking didn’t show any damage as I’ve heard that that had been the case for others.
Wingspan: 63 in. (1600 mm.)
Wing Area: 730 in². (46.5 dm².)
Weight: 9.5-10.5 lb. (3970-4540 g)
Wing Loading: 30-33 oz./ft². (91-101 g./dm².)
Length: 56 in (1420 mm.)
6/8/2009 – After inspecting the major components of the kit and not finding any issues, the build starts like any other build, get out the covering iron and go over all seams.
The covering is a mat finish and looks good. All the seams were tight with a little cover wrinkling just on the flaps and ailerons. These were taken care of with the iron.
A nice touch is the factory installation of the wing flying surfaces. The ailerons are pre-attached using CA hinges and the flaps are pre-attached using hinge-point hinges.
The next step calls for servo mounting and I need to wait for mine to be delivered.
The kit is supplied with plastic mechanical retracts. I hope these don’t become a weak-link, but I’ll try them out before replacing them.
6/21/2009 – On page 3 of the instruction manual is the “Decisions You Must Make” section. Here you’ll find the minimum recommendations / requirements for radio channels, servos, servo extensions, Y- harnesses, receiver battery pack capacity and engines.
Top Flite recommendations / requirements are:
- 6-channel radio system with a 6-channel receiver
- 7 – standard servos with a minimum 50 oz.-in. torque for control surfaces. (Note, this is a mistake as only 6 servos are needed for control surfaces)
- 1 – standard servo with a minimum 44 oz.-in. torque for throttle
- 1 – retract servo with a minimum 61 oz.-in. torque
- 2 – 24″ aileron servo extensions
- 3 – 6″ aileron, flap and retract servo extensions
- 2 – aileron and flap servo Y- harnesses
- 1 – 4.8V, 1000mAh receiver battery
- 1 – .60 – .91 cu. in. two-stroke or .90 – 1.20 cu. in. four-stroke engine
My planned requirements are:
- Spektrum AR6200 6-channel receiver – Upgraded to the Spektrum AR7000 7-channel receiver
- 6 – Hitec HS-475HB control surface and flap servos with 76 oz.-in. torque @ 6V
- 1 – Hitec HS-75BB retract servo with 114 oz.-in. torque @ 6V
- 1 – Hitec HS425BB throttle servo with 57 oz.-in. torque @ 6V
- 1 – A123 6.6V 1,100mAh receiver battery
- 1 – Thunder Tiger F-91s four-stroke engine
6/22/2009 – Mounted the flap and aileron servos to their respective cover hatches.
Be sure that the flap servo on the left wing half is positioned with the servo arm towards the wing root and the right wing flap servo arm is positioned towards the wing tip.
This way, when the flap servos are connected to the receiver using a Y-harness, they will both move in the same direction.
6/23/2009 – Engine has been shipped. $183.95 from Precision Aero. Best price on the Internet and Ron’s a good guy . You should check out his offerings.
Displacement 14.97 c.c. / .914 cu.in.
Bore 28.3 mm / 1.114 in.
Stroke 23.8 mm / 0.937 in.
Practical R.P.M. 2,000 ~ 12,000 rpm
Output 1.6 BHP / 11,000 RPM
Weight 742.8 g / 26.20 oz
6/25/2009 – Still awaiting the retract servo but I went ahead and temporarily mounted the landing gear.
The manual calls for you to remove and apply thread locker to the gear wire set screws. Don’t omit this step as I’m sure they have good reason to recommend it.
Even if the set screws stay tight without the thread locker, I did find that the set screws on one of the gears were only finger tight which could have become a problem.
Before drilling the pilot holes, attach the axle to the gear wire so you can properly align the gear on the gear rails to ensure that the axle is positioned dead center in the wheel recess.
6/26/2009 – Joining the wings is such a fun step! I never, ever mix enough epoxy the first time and always make a mess.
Anyway, I affixed the leading edge nylon pins before joining the wing so they could be used as clamping points.
When I dry fit the wing panels I had a bit of a gap so I lightly sanded one of the wing root ribs until I closed the gap. Then I smeared on the 30-minute epoxy giving a good coat to the wing joiner and clamped it to dry.
Engine arrived. Thunder Tiger does an impressive job at packaging their engines. It comes complete with glow plug, a 5 /5.5mm and a 12 /14mm wrench and an assortment of allen wrenches.
I’ll break the engine in using my engine stand and the P-47 fuel tank. I’ve found it reassuring to verify the fuel tank before assembling it into the airplane.
7/8/2009 – Installed the retract servo. The servo tray is in three parts and each piece should be fitted in the wing first, then each piece is glued in place.
I used epoxy to glue in the servo tray pieces then when dried I installed the servo. Attaching the retract push rods was straight forward and the operation was smooth without any binding.
I found that a very handy accessory to use when working with servos is a servo driver. This tool eliminates having to hassle with a receiver and transmitter when installing servos and connecting the push rods.
First I use the driver to verify the servo with the extension operate properly. Then when I’m ready to hook up the push rods I use it to center the servo arm and verify the throw.
I find it to be a real timer saver.
7/9/2009 – With the wing assembly completed (except for the gear doors, guns and belly pan, which I’ll complete a bit later in the assembly so as to not damage them) it’s time to mount the horizontal stabilizer. Pretty straight forward with this part of the build. However, when I went to attach the wing I found that one of the wing hold down pin holes was out of alignment. A simple fix with the Dremel and all is well.
I changed out the supplied nylon wing bolts for Dubro ones. The Dubro bolts have a 3/32 hex head which makes the inserting and removing easier and precludes the screw driver tip from slipping and gouging the wing.
The horizontal stab lays nice and parallel with the wing so no sanding was required. I positioned the stab equally in the fuse and aligned it with the wing, then drew my outline marks where I needed to cut away the covering for gluing.
Make sure that before you glue the stab in place that you insert the elevator joiner wire first.
Slide the stab into the fuse and then liberally apply 30-minute epoxy to the top and bottom. Make sure you do not get epoxy on the trailing edge of the stabilizer as this will cause the elevator joining wire to become affixed to it.
Wipe away the excess glue with rubbing alcohol, double and triple check the stab alignment and make sure the joiner wire moves freely, then let it dry.
Started to add the P-47 model to my transmitter and bind the receiver. The brand new Spektrum AR6200 receiver is defective, it won’t bind. I called Horizon support and I need to send it in for repair. I figure at least a three week turn-around so I’ll have to take one out of another plane.
7/11/2009 – Attached the elevator and rudder. All of the hinge slots needed to be deepened with an X-Atco knife as they were too shallow for the hinges to seat properly.
Apply a small amount of epoxy on the joiner then install the elevator.
Tee pins were used to keep the hinges centered then removed before gluing. Since the elevator leading edge is beveled, there should only be a very small gap between the elevator and stab.
Bend the elevator at a 45 degree angle and apply a small amount of CA directly to the hinges. Turn the plane over and repeat.
Check the joiner for any epoxy that may have come in contact with the stab. Use a paper towel to wipe it away and keep flexing the elevator until the epoxy cures.
The rudder is installed in a similar manner.
After the glue dried, I attached the control horns to complete the tail assembly.
7/12/2009 – Next is the tail wheel assembly and rudder servo installation.
7/16/2009 – Assembled the fuel tank. I use the Dubro E/Z Fill Fueling Valve which only requires two tank lines. One with a clunk that’s used for the fill line and carburetor feed line, the other is the pressure/overflow line. I’ll verify the tank reliability when I use it on the break in stand when I break in the engine.
Temporarily mounted the engine and attached the throttle push rod. I used a push rod with a Z- bend to attach to the carburetor. This is a simple installation and is totally reliable.
Finished installing the servos.
Permanently mounted the engine and began working on the cowl.
I trimmed away the bottom portion of the dummy engine to provide a flow of air to the engine.
Then I made holes in each of the cylinders for the aluminum tubes that simulate push rod covers. I first made a starter hole with an X-Acto blade then used a drill to make a 1/8″ hole then inserted the tubes.
I used the same method to install the red spark plug wires but made a 1/16″ hole.
To complete the assembly, from the inside I used a drop of thick CA on each insertion point to permanently affix everything.
You’ll see that I’m missing one red wire as the provided wire was not long enough to make all nine pieces. I’ll add it latter when I scrounge up a small piece.
7/19/2009 – Mounted the landing gear doors. The doors are made from fiberglass and are very sturdy.
Attached the receiver battery to the battery / receiver tray using a small foam pad and a cable tie. I’ll attach the receiver using another foam pad and a cable tie.
Used small servo screws to install the tray.
7/21/2009 – Installed the receiver batter switch. Since my receiver battery uses a Deans connector I need to replace the standard connector on the switch harness with a male Deans.
Then I mounted the switch on the side of the fuse close to the cowl and on the opposite side from the engine exhaust.
7/24/2009 – Broke in the engine using my Vmar engine break-in stand from Richmond RC, still only $19.99. Ran through three full tanks following the manufacturer’s recommended procedure.
8/2/2009 – Reinstalled the engine and got the cowl mounted. The dummy radial engine made it a bit of a tight fit and I’m not 100% happy with it as the bottom of the cowl sits a little bit lower then the top, but it’s not that bad.
Next is using card board stencil material to locate the cut outs for the exhaust.
My friend finished painting the Aces of Iron pilot and it came out looking great. Now I need to figure out how to mount it in the cockpit.
When asked to comment about the build progress, Max had nothing to say. I guess I need to pick up the pace and get this build done and in the air.
8/6/2009 – Finished cutting the cowl. I used card stock material to make a stencil to locate the exhaust, needle valve and glow plug locations then transferred these cutouts to the cowl and marked accordingly. Then I used a Dremel to cut out the holes.
I was able to use a single piece of card stock to make all three needed holes. On the stencil I identify the plane that it was used on and put it away in a safe place. It’ll come in handy someday if I ever need to replace the cowl or build another kit.
8/14/2009 – Mounted the pilot figure and attached the canopy. I made a balsa shelf that I attached to the pilots seat located so that the pilots head would be near the top of the bullet shield.
I used four #2 button head screws to attached the canopy rather then canopy glue, so that I can dress up the cockpit later or if I need to re-seat the pilot. I’ll touch up the screw heads with a dab of olive drab paint, same with the cowl screws.
All the electronics are now in place. I upgraded to a Spektrum AR7000 receiver. I decided I wanted to take advantage of the data port to verify that I have good connectivity with the transmitter using my Spektrum Flight Log.
8/16/2009 – Installed the DuBro E/Z Fill Fueling Valve on the cowl, added a fuel filter and connected the fuel and vent lines. Before buttoning down the cowl, I adjusted the throttle throws and set my transmitter’s engine cutoff button.
I then set all of the control surface throws as recommended for low and high rate.
The plane balanced, without having to add weight or relocate any of the electronics, exactly at the recommended CG with a little nose down attitude, perfect.
8/26/2009 -All that is left is to apply the decals and fly her. I’m holding off the maiden until our club’s warbird event which is on September 19th.
9/20/2009 – Well I got close to the maiden. The P-47 was ready to go but running the clubs warbird event left me with no time to fly. I’m going to try again next weekend.
9/26/2009 – Flew the maiden! Wow, what a fine looking bird screaming low and fast, just how I’d hoped. The Thunder Tiger F-91S combined with a Master Airscrew 14 x 6 prop absolutely makes this plane rip! Half throttle is just perfect for scale flight and full throttle flybys are stunning. The sound is awesome.
The recommend high rate throws for the ailerons are a bit conservative which make rolls a little too slow. I’ll increase them by a 1/4″.
The plane slows down really well and flaps would only be needed if I was flying on a shorter runway.
No video of today’s flight, but I should have video of tomorrows.
9/27/2009 – Had more great flights today, but sadly no video again. Bummer.
10/22/2009 – I should have video this weekend. I really enjoy flying this plane!
11/03/2009 – Unable to get video again. I’m completing this build log and will post video when I can get it.
04/04/2010 – Finally have video of a flight.
DLE-20 20cc Gasoline Engine Conversion
2/10/2011 – The Extra 260 conversion went so well I ordered up the DLE from Tower and it should arrive on the 11th. Just have to clear the bench of a combat plane or two and then I’ll be ready.
2/12/2011 – Received the DLE-20. If this is your first DLE-20, the first order of business is to download the Hobbico version of the DLE-20 user manual. Much better!
The initial conversion look-over looks to be pretty good. No cutting of the firewall will be needed, engine and muffler look to fit completely inside of the cowl, and the Sullivan gasoline fuel tank conversion stopper is a perfect fit for the original tank.
Used the motor mount template from the Aeroworks conversion kit to mark the mount holes.
Since the template is designed for use with the Aeroworks engine mount, you’ll need to move the new holes up and down to align with the existing holes. The template helps get the width measurement correct as the stock location is to narrow.
The stock motor mount is a Great Planes two-piece connected mount. Hobbico recommends a two-piece engine mount that does not interconnect or overlap at the firewall for the DLE-20.
I assume this has to do with vibration so a simple fix is to just cut the interconnecting tabs off of the stock mount.
Working out the throttle linkage. Rotated the carburetor throttle arm 180 degrees and attached the DLE included phenolic extension.
Throttle linkage worked out pretty well, however the choke will require a push rod support bracket of some kind to run it out towards the front of the cowl.
2/13/2011 – A selection of fasteners on-hand, in easy reach and organized has been a life saver and time saver. Especially when doing conversions as the original fasteners may need to be changed out due to a need for a different size or you simply prefer to not want to use a stressed out blind nut. Grabbing the exact size nut, bolt, or washer can make a huge difference.
A few years back RTL fasteners had a great deal on their Master Build Assortment so I got one, and haven’t regretted the expense yet. The kit comes with plastic organizers but I added the extra convenience of a tackle box organizer which also holds all my basic build tools.
On to the fuel tank assembly. I ordered the Sullivan Gasoline Fuel Tank Conversion Kit along with Dubro Fuel Line Barbs and a large Dubro Clunk. The large (heavy) clunk is recommended as the gasoline fuel tubing becomes stiff after a while and the extra weight of the cluck helps to over come the stiffness to keep it wet.
Note: A heavy clunk is really needed when using the stock fuel tank. Because gas tubing is fairly stiff when new and only gets stiffer, a standard clunk will “hang” in the tank due to the short length of pick-up line. I tried the standard clunk and it didn’t touch the bottom of the tank, just hung about a 1/4″ above it. When I put the heavy clunk on it sat nicely on the bottom.
With gas fuel line, the brass tubes require barbs which help keep the tubing attached as the gas tubing will expand over time and will slip. The barbs only need to be soldered onto the ends of the pick-up line. The vent line does not require barbs, plastic ties will be sufficient.
When soldering on the barbs, make sure they face the correct direction and that you don’t solder on both barbs before inserting the tube into the stopper and stopper mounts. Don’t worry, if you happen to solder both bards before inserting the tube, a little heat will allow you to remove one end.
One item still needed is a “T” for the filler line and that’s on order from Aeroworks.
2/15/2011 – Mounted and cut the cowl. Had to make the opening larger than I had hoped due to the corner of the muffler hitting near the front of the cowl, but it’s still pretty well hidden.
2/16/2011 – Figured out the choke linkage. A slight bend in the push rod, a simple 1″ x 1/2″ Stanley corner brace from Lowe’s and a rubber grommet did the trick. I added an “EZ” type connector on the end for better grip.
I’ll probably replace the steel brace with some aluminum angle cut to size and drilled to save some weight.
Sorting through the ignition mounting and wire placement. There is a perfect place for the ignition on the bottom of the firewall but it’s difficult to run cable ties through it.
I found some 1″ x 1″ adhesive cable tie mounting bases. I used a wood screw and CA on the adhesive to secure it to the firewall.
2/18/2011 – Ran the ignition wires. I used 1/4″ cable clamps to secure the wiring.
Installed the Tech-Aero IBEC ignition on/off indicator light up through the fuse to the cockpit. I CA’d a thin plastic straw with the exposed tip painted olive drab. I inserted the light and used as dab of silicone to hold it in place.
The Ignition Battery Elimination Circuit IBEC is used to manage remote engine kill, ignition switch, ignition voltage regulation, RF filtering, and allow for the use a single battery for the receiver and ignition.
Pretty much have everything installed and buttoned down, except the air retract servo, which I’ll get setup next. I temporarily relocated the 1,100 mAh A123 battery to the middle of the fuse as I expect the balance to be a bit nose heavy. I have a larger 2,300mAh A123 battery I can use if needed for extra weight.
About the air retracts, I had the misfortune of an elevator servo stripping out in flight. The resulting “hard” landing did a number on the mechanical retracts. During the repair I decided to upgrade the system to Robart air retracts.
2/19/2011 – Sorted out the air retracts, all good to go. Just waiting for a few more parts and she’ll be ready for the maiden.
One item I’m waiting for is a prop hub from Tru Turn. With a hub you use a double jam nut adapter which provides more security than just a prop nut.
2/23/2011 – Received the last remaining parts. Mounted a 16 x 8 Xoar prop and the Tru Turn Prop Hub and now I’m ready to balance.
I was hoping to use the factory installation point for the battery which is right behind the fuel tank and nicely secured with a battery tray.
Turned out that I can. I just needed to use a larger (heavier) battery. With the air retracts and DLE-20 the P-47 balances tail heavy using the original 1,100mAh A123 battery. Luckily a 2,300mAh A123 fits in the stock location and balances perfectly at the recommended CG!
I also replaced the steel choke brace with an aluminum one, saved 6 grams or 1/5 of an ounce!. Hey, a grams a gram :)
Ready for the maiden, hope it doesn’t rain this weekend.
2/24/2011 -I had found an issue with the throttle connection using a steel clevis. I found that vibration was enlarging the hole in the carburetor arm due to the metal pin on my Aeroworks Extra DLE-20 conversion. I changed out the clevis for a Sullivan ball link connector.
After the DLE-20conversion, the 2,300mAh battery and with the added air retracts, she weighs in at 10 lbs 12 oz. Not bad at all!
2/26/2011 – Rained out today. Sunday looks good though.
2/27/2011 – Flew the maiden. The DLE ran like a champ. Set the needles at 1 1/2 turns for the both the low and high end and it fired right up. Slight turn in of the low end was all that was needed.
6/11/2011 – The P-47 is flying great. After 50 flights, no problems with the DLE-20. I did have to belly land after one of the new air retracts would not deploy. Luckily no damage. I replaced the air retracts with E-flite electric retracts and couldn’t be happier!
6/12/2011 – Well, flight 51 of the P-47 with the DLE-20 conversion was the last.
Halfway through another fun flight the elevator servo went out in the middle of a turn. It was a dramatic high speed impact with a really nice debris field and wreckage. Not sure why I’ve lost two elevator servos in this plane?
Not much else to say, except I’ll really miss this plane………until I get another one!