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Old Nov 28, 2013, 03:23 PM
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Freewing B-17G 1600mm Build thread

Have finally purchased the Freewing B-17G to fly with the B-17 crew at the airfield. It's my first Freewing model and I have to say that the detailing both in the build and the scale detail are amazing.

This thread is meant to complement what looks like the main Freewing B-17G discussion thread which can be found at:
B-17 Freewing general thread “Freewing B17............nice!!!!”
http://www.rcgroups.com/forums/showthread.php?t=1438722

I have put this thread together so that the reader may have all the modifications of one builder together in one spot rather than have to read through the 70+ pages of the main thread. I would prefer responses directed to be only to this build, with general responses better posted in the main thread.

Note: The model described here appears to be a "version 2" model just purchased in Oct 2013 from Motion RC (great store, highly recommend, easier than having to work with BH overseas). After reading the longer Freewing B-17 thread it seems that most of the issues cited previously have been fixed in my model.

Positives:
1. Excellent scale detail.
- Paint job is great, and even includes painting of the control horns in the appropriate color. Most other models have white plastic control horns which look terrible. Still have to repaint the control rods and clevises, though.
- Excellent, water slide decals. These look so much better than the vinyl decals which look like plastic stickers from other manufacturers.
- Window decals actually look quite good, and avoid the issue of looking into a fuselage full of wires for the most part (except cockpit and radio room window on top which are clear)
- Much more scale retracts, seem to work well for me. There is some play in the linkages, however, but it doesn't seem to bother the aircraft for now. NOTE: The left retract suddenly unexpectedly collapsed on me for no reason taxiing out on the second day I owned it shattering the left props. Wing scratched but not badly. Have been working with Motion RC for a fix.

2. Nice attention to build detail. Inlet air ducts at the sides of the nose beautifully hidden under the gunner windows. It did need an outflow air duct, though, which was missing.

Negatives:
1. Terribly ugly chin turret detail and tail gun detail. So ugly in such a prominent location that I almost made the mistake of not purchasing the model. This goes in the "what were they thinking" file after all the great and attentive detail for the rest of the aircraft. instead of the ugly square mount for the machine gun, Freewing easily could have molded grooves for the machine guns and provided sharpened end machine guns similar to the ones for the waist gunners. Same for the tail gunner. Will need to fix.


Specifications of model:
Scale: 1:20 approx.
Wingspan: 1600mm / 63in (Real Aircraft 104' - 32 m)
Length: 1170mm / 46in (Real Aircraft 74' - 23 m)
Flying Weight: 2350g
Power System: Brushless 3130-1350Kv x 4
Speed Control: 30A brushless x 4, BEC, T connector
Propeller / EDF: Four 7x6 3-blade propellers
Servos: 9g×6 17gx1
Landing Gear: Electric servoless retracts with suspension
Required Battery: 11.1V 1800mAh 25C 3 cell LiPo (2 required)
Required Radio: 6 Channels
Lights: No
Hinge Type: Nylon hinges on all control surfaces
Material: EPO Foam
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Old Nov 28, 2013, 03:30 PM
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So here is a brief summary of the build to date. I took the template from to RCG Thread:

B-17 Freewing general thread “Freewing B17............nice!!!!”
http://www.rcgroups.com/forums/showthread.php?t=1438722

Post 471 by Merlin V16 "HK Freewing B-17G 1600MM Build Check List outlines many of the below items, and I have modified with my comments below and added additional notes. Details and images are posted below:

• Remove Cowls (two screws in front) and remove Motor and Loctite the two setscrews to secure Motor to shaft. Re-install everything. – done (on my model, this turns out to have been unnecessary as the screws were all tight already)
• Check every screw and Nut on the landing gear. – done (most were tight)
• When installing the ESC Lead wires on the inboard Nacelles, routed the leads to the side, under the wood plate, away from Landing gear linkages and fixed with hot glue gun.
• Used heat shrink tubing over all motor and ESC wire connections
• Used ZAP epoxy to connect wings and glue on nacelles. Did only one motor at a time to insure a good joint
• Cut out diagonal vent at foam under rear part of large lower fuselage hatch. There are cleverly disguised air intakes in the windows on each side of the nose.
• The elevator control rod guide tubes are glued in at an incorrect angle, causing the pushrods to exit the fuselage too close to the fuselage and too far from the control horns on the elevators. As a result and as reported in the general build thread, the pushrods bind against the guide tubes. The fix requires removal of the pushrod covers from the outside of the fuselage, loosening the pushrod guide tubes from both the outside and the inside. This caused them to angle outward more and fix the problem. I didn’t have to remove them completely.
• tail wheel servo linkages was in good condition. There was even a flat spot on the tail wheel to prevent slippage.
• there are 2 wing wire covers stuck together
• use a CC 10 amp BEC
• There is a 4 lead "Y" and you can just remove the red wire from it to disable the BECS on all 4 ESCs at once. I removed each red wire from each ESC.

Propellers:
- Left standard
- Right reverse
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Old Nov 28, 2013, 03:38 PM
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The forward vent holes are cleverly disguised under the gunner windows. I added an exit vent hole cut diagonally under the elevator servo access hatch. This was painted and the hatch made removable for access with mounting screws and wood mounts.
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Old Nov 28, 2013, 03:49 PM
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Assembly of inboard motor nacelles with retracts. There was no room for the retract wire when the nacelle is glued to the wing. A small foam channel was cut out to allow a good fit. Used ZAP Epoxy to glue in each motor nacelle. Only do one at a time, as you will need the 5 minute bond time to properly fit each piece to the wing without spilling glue and to get a good bond.

Once in place, the ESC wiring was also a bit of an issue. A small channel was cut on the inside foam next to the retract mounting plate for a better wire fit. The wires were the secured in place using glue dripped in from a hot glue gun. Note that I always use heat-shrink tubing over the connections between ESCs and motor wires to prevent an accidental disconnect.

The wing slots had to be cut out slightly to allow for a complete fit of all cables. Note the grey servo lead connector as well to prevent disconnect between the aileron leads. The wing covers were then glued in place.
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Old Nov 28, 2013, 03:55 PM
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Wing is joined with carefully applied ZAP epoxy and clamps
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Old Dec 01, 2013, 10:50 AM
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Maidened the aircraft yesterday. Initial stock CG recommendation 95-105mm from front of wing at fuselage. Mine was set at 100mm, and caused a sharp pitch up on takeoff which was not easy to control. The only adjustment was to move the CG forward to 90mm and everything flew great.

This position corresponded to both 2200 mAh batteries moved all the way forward in the battery compartment with the ESCs on the back white velcro tape.
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Old Dec 01, 2013, 10:53 AM
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Images at the field for the maiden. A beautiful California Thanksgiving weekend. Gun detail etc not complete yet.
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Old Dec 01, 2013, 06:31 PM
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Thanks for posting the great pic`s and the useful info. What kind of settings are you using on your radio for aileron and elevator deflection? I heard some people are using as low as 30 -35 % on them.
Thanks,
Frank
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Old Dec 02, 2013, 12:47 AM
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Transmitter Setup (Spektrum DX18)

- Because Spektrum receivers briefly revert to the settings at which they were bound each time a new flight battery is connected, be sure to bind receiver with gear down, flaps up.

Rather than keep dual rates on individual switches, I link them together on a single, 3-position flight mode switch. Flight mode 0 is good for casual flight, and flight mode 2 is for stunts etc. In flight mode 2 the aircraft is very maneuverable in a non-scale like manner and flies almost like a Parkzone P-47 on 75% dual rates. Stick with mode 0 to maiden and keep the CG forward (see above).

Mode 0 1 2
Ail 70 85 100 25% expo all modes
Elev 55 70 100 25% expo all modes
Rud 100 100 100 0% expo all modes

Aileron Differential 15%

Flaps Flap Elev Flap Deflection (mm)
Pos 0 96 0 0mm
Pos 1 20 5 17mm
Pos 2 -20 10 26mm

Timer 5:00


As I have extra channels, my original intention was to use one channel per ESC/motor. This worked fine per the channel assignments below in parentheses. Then I tried to program a startup sequence between the motors using the DX18 Sequencer, which annoyingly reassigned my motor channels and completely wiped out the X-1 channel output for the model profile in the transmitter. Have temporarily plugged the ESCs back to the stock 4-lead servo wire out of the original throttle channel until I can reprogram. Calling Horizon Hobby they said it was a glitch in the sequencer programming and I would have to reprogram the whole model profile under a new blank profile. So note not to add channels otherwise used in controls (such as throttle) to the sequencer - only use otherwise unused channels in sequencer programming. Note, when messing with the sequencer involving motor channels remove all props from motors. One motor went off and pulled the wing off the couch and destroyed one prop. Fortunately, Freewing included an extra CW and CCW prop so I was OK.


Here are my channel assignments:

Channels:
CH1 Throttle (sound card - all ESCs are mixes to higher channels)
CH2 R Aileron
CH3 Elevator
CH4 Tail wheel
CH5 Flap
AX1 L Aileron
AX2 Gear
AX3 Rudder
AX4 (Motor 1)
AX5 (Motor 2)
AX6 (X+1) (Motor 3)
AX7 (X+2) (Motor 4)

For mixes, I put the tailwheel on the rudder channel and slave the rudder to this channel. This allows the rudder trim on the transmitter to trim the tailwheel rather than the rudder itself, which is helpful for quick adjustments while taxiing. The motor mixes below work and use switch H as a throttle cut for safety.

Mixes
RUD -> AX3 ON Rate 100 100

Each Motor (here AX4 is the example, use a different channel for each motor):
THR-> AX4 Switch H 0 I Rate 100 100 Offset 0
AX4->AX4 Switch H 0 I Rate 0 100 Offset 100

When setting this up, be sure to REMOVE the props and test motor startups to prevent and accidental startup and blender.

Servo travel for rudder (tail wheel) increased to 150% because the original travel was not sufficient to keep the aircraft from being turned sideways on the runway with only a moderate crosswind. I also added length to the rudder servo arm - see later post.
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Old Dec 02, 2013, 12:56 AM
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Be sure to balance the propellers. I use a prop balancer (the mechanical disc one, not the magnetic one in which the shaft is too big for these props) and wrap black electrical tape around the base of the prop blade that is light until balanced.
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Old Dec 02, 2013, 01:12 AM
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For better heat dissipation from the ESCs I carefully cut off the heat shrink tubing from the ESC heat sinks.
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Old Dec 02, 2013, 01:32 AM
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Added hatch magnets. Also added a reverse Y-connector from both Deans to a single EC5 connector to use a single 4400 mAh battery as I have many of these from my jets and few 2200 mAh batteries and didn't want to buy more. This required an additional 1oz nose weight. Staying with 2 2200mAh batteries is certainly easier.
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Old Dec 02, 2013, 10:40 AM
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A few notes on flying.

1. Keep your speed up. This model is more stable flying fast rather than slow. On takeoff, try to get up to full throttle before the wheels lift off.

As mentioned before, this model can fly almost aerobatically like a much smaller warbird. See post #1037 by JLogan on the main B-17 discussion page #70 or look up on YouTube. My model can fly the same way.

http://www.rcgroups.com/forums/showt...438722&page=70

2. Avoid flaps on takeoff or landing for the first few flights.

3. Once comfortable, trims are adjusted and CG is adjusted, then begin using flaps. My flap settings are listed above. This will also allow more stable slow flight.

Happy landings.
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Old Jan 03, 2014, 09:55 PM
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Installed the Mr. RC Sound System and also created a motor startup sequence. Here is the video of the startup sequence.

B-17 Motor Startup Sequence (0 min 32 sec)
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Old Jan 03, 2014, 10:11 PM
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My method for Mr. RC Sound system installation:

1. Cut out rectangle of foam in the front portion of the wing to just admit the speaker
2. Installed carbon rods to support speaker. To do this, I passed a thin, sharpened metal rod through the foam from the front of the wing just underneath the speaker to create a narrow tunnel. Then passed a sharpened carbon rod through these tunnels. Cut carbon rods about 4-5cm longer than the width of the opening to allow 2-2.5 cm of carbon rod to remain in the foam at either side. Passed these rods through the pre-cut tunnels. Marked 2-3cm from the ends for proper length. Placed a dap of Gorilla glue on each hole at the back of the fuselage and passed the rods through to the marks. I used 4 rods, 2 wound likely have sufficed. I didn't mind that the rods weren't completely straight.
3. Press speaker gently down to carbon rods from above and secure with a few dabs of hot glue on the edges.
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