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LOCKHEED P-38J “LIGHTNING”. A giant 1/4 scale scratch built model

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LOCKHEED P-38J “LIGHTNING”. A giant 1/4 scale scratch built model

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Old 10-06-2018, 07:08 AM
  #51  
fbielsa
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On the lateral surface of each fuselage, the interior walls of each radiator are formed in a 2 mm balsa sandwich and fiber.glass

These walls will serve to fit the parts of said fairings and glue them permanently.

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Old 10-06-2018, 04:34 PM
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Great progress, looking good!
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Old 10-18-2018, 08:01 AM
  #53  
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About the canopy, I opted for an anchoring technique similar to the one I used in my Stuka (
- maiden flight) (
- flying and dropped bomb). It is completely removable and without fixing screws.


Made in a single piece of fiberglass from mold on a carved wooden plug, it is attached to a frame that fits by bayonets in the seat of the nacelle



Assembly of wooden samba parts




Plug carved and sanded



Plug ready to be used

It has two front dowells and a hidden rear bolt that is operated with the handle that maneuvers the ladder of the real plane



Canopy and mold to be made. Note the alu dowells at the front



Frame that fits with four wooden bayonets

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Old 10-24-2018, 09:50 AM
  #54  
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A pic with the fairings already presented, before continuing with the different scale details
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Old 10-24-2018, 10:03 AM
  #55  
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Now it is time to empty the space where the turbochargers are located, in the upper central part of both fuselages, which have been manufactured with pieces of carved balsa wood, plywood and fiberglass. Said emptying is already foreseen in the semi-formers that make up these upper casings, so that only the balsa sheeting has to be removed from the corresponding part.



Supercharger and its fairings


They are bolted on said removable housings of both fuselages, which are fixed with a retractable front lockshield under the fuel filler trap door in the model and two rear neodymium magnets; another bolt ensures here the assembly, which is accessible by the lower part of the fuselage through the open doors of the main landing gear deployed.

I do not show photos for now, that I reserve for when I show you the painted model.

The machine guns and nose cannon have been worked on 0.6 mm PVC wall tube. The elevator counterweights are reinforced balsa and plywood. The glazing of the side and landing lights on the wing and the fairing of the rear-view mirror of the cabin are vacuum ther****rmed under. Finally, the four bays of expulsion of the machine guns in the gondola, the two "pylons" under the wing and other details of the model are practiced.

And we have ready the model to think about the electronic equipment that I will describe immediately.
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Old 10-24-2018, 10:13 AM
  #56  
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Looking very good!
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Old 10-26-2018, 05:01 AM
  #57  
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WWII enthusiastic here for warbirds. That is an awesome piece of work on the P-38!!!. I also have a large scale P-38 that I am restoring that I bought from a fellow that had a crash.

Builders are becoming scarce with that type of skill set like you. I commonly find myself repairing aircraft for people in my local area when they fly into fences and/or planting in the ground.

Just wanted to say, what you built is highly appreciated by me. It's heart, soul, and hands on all the way through. Not an easy project by any means however, well done!

Cheers,
William

Last edited by wgmg2185; 10-26-2018 at 05:11 AM.
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Old 10-26-2018, 09:33 AM
  #58  
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Originally Posted by SHANEC View Post
Looking very good!
Thanks a lot for your words. It is always stimulating for the soul
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Old 10-26-2018, 09:43 AM
  #59  
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Originally Posted by wgmg2185 View Post
WWII enthusiastic here for warbirds. That is an awesome piece of work on the P-38!!!. I also have a large scale P-38 that I am restoring that I bought from a fellow that had a crash.

Builders are becoming scarce with that type of skill set like you. I commonly find myself repairing aircraft for people in my local area when they fly into fences and/or planting in the ground.

Just wanted to say, what you built is highly appreciated by me. It's heart, soul, and hands on all the way through. Not an easy project by any means however, well done!

Cheers,
William
Thanks for your words, William. I'm glad you like the project.

Spain is not a country as populated as yours, but something similar happens with builders. Every time we are less, I would say that we are "rara avis", even though the aeromodelling is an art that is hardly conserved if building is not practiced. I do not conceive our hobby if it is not designing a plan or building on it.

Good flights and best regards
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Old 11-02-2018, 09:01 AM
  #60  
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Onboard equipment

The aspect that has contributed the most to the bad fame of the P-38 is, without a doubt, the ease to go into an "spiral of death" when an engine stops for any reason. It is an aircraft with a large distance between engines, so any problem in one of them results in an uncontrolled yaw and the almost certain loss of the device.

The real was easily controlled by the pilot, who had immediate information in case of emergency and could quickly compensate the control surfaces. In the case of the model airplane, depending how fare from us is she, it can be difficult to appreciate the engine affected on time, so that when we want to react, it will be too late.

We must mention that with a single engine running, at least 50% power is lost in flight provided that we maintain the maximum acceleration, but this traction is precisely what causes the lifting of the wing of that side and uncontrolled stall towards the other; lifting the nose in that situation, precipitate the disaster. Who has never seen a precious twin engine to "lose" an engine in flight and immediately, to everyone's surprise, perform the so-called "spiral of death"?

Therefore, if this happens, gas must be reduced to a long idle, immediately adopt a descent attitude in order not to slow down and land by right. If something of gas control must be done, so as not to fall short, it should be done slowly without passing 50% of gas, and, above all, perform open turns, mixing with rudder towards the side of the running engine. It must be in mind that, since it can not exceed 50% of gas, the plane will only offer a 25% of real maximum power, so there is no other option but to pose, without delay, the forced landing.

Faced with this uninspiring scenario, it seems crucial to adopt measures aimed at minimizing the mentioned risk, especially in a model with gas engine and, above all, so laborious. Therefore, I was inclined from the beginning to provide this device with special electronic flight assistance systems, although this implies greater complexity of the equipment, difficulty in its programming and the possibility of other electronic failures.
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Old 11-03-2018, 06:58 AM
  #61  
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This is exactly what happened on my VQ P38. While running at about 3/4 throttle she rolled to inverted when I lost one engine. I chopped the throttle,rolled it over,dropped the gear and lucky me I was in perfect position to land. It turns out one of the headers, on my OS91 4 strokes , broke off flush with the head, causing the engine to quit.Vibration seems to have been the problem.
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Old 11-06-2018, 04:50 AM
  #62  
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Originally Posted by SWORDSN View Post
This is exactly what happened on my VQ P38. While running at about 3/4 throttle she rolled to inverted when I lost one engine. I chopped the throttle,rolled it over,dropped the gear and lucky me I was in perfect position to land. It turns out one of the headers, on my OS91 4 strokes , broke off flush with the head, causing the engine to quit.Vibration seems to have been the problem.
,
Hi Swordsn. You were really lucky and skilled to react so fast. In other occasions, the lack of speed and height can be very dangerous and has not time to control the plane.
The failure that you explain is very frequent in this type of engines. That is why it is very important to check all the joints and screws in four-stroke engines often. Greetings.
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Old 11-08-2018, 09:38 AM
  #63  
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1. Electronics and pneumatic system

I have chosen to install a gyroscope (PowerBox i-Gyro SRS®) with GPS, to control, at least, the two most critical axes (aileron and rudder) in the event of an emergency caused by engine failure, and contribute to the stability of the model at any speed; I have also programmed it to manage the elevator. It is permanently connected in flight and can be controlled by a switch from the transmitter.

The advantage of this device goes beyond damping the influences of wind gusts when maneuvering, because it also acts when we do not touch the stick controls, making the model follow the last trajectory or position defined in the transmitter when releasing the sticks. The pilots of jets and 3D acrobatics know very well this type of piloting. In addition, this gyroscope allows automatic regulation of the gain depending on the speed of the model, according to the data provided by the accessory GPS device, so that it is still equally effective in landings.

I facilitate the direct link to the product on the website of the manufacturer for more information

https://www.powerbox-systems.com/pro.../igyrosrs.html

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Old 11-12-2018, 08:48 AM
  #64  
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My P-38 is also equipped with an electronic synchronization device for both motors (TwinSync®) from D@L



This system not only provides a perfect synchrony of the rpm at any speed, which could be replaced by a good carburetion and perfect geometry in the throttle control, but also offers a safety bonus by immediately slowing down the opposite engine, at a pre-set position, when it detects the failure of one of them.

This last aspect is the most interesting to avoid the increase in drag of the affected wing and its immediate stall. In this way, we will only have to focus on "stick forwards", not to lose speed, and prepare the landing. Discretionally, the remaining engine control can be recovered by moving the gas stick to the minimum and progressively accelerating again so as not to lose all traction.

I know that neither the i-Gyro nor the TwinSync guarantee full safety in flight, but all precautions are few when it comes to a P-38 of this size. However, it is desirable to delay in checking the actual effectiveness of these devices in a compromised situation.

Last edited by fbielsa; 11-12-2018 at 08:51 AM.
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Old 11-18-2018, 11:52 AM
  #65  
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Absolutely stunning and very impressed !
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Old 11-24-2018, 12:28 AM
  #66  
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Glad for it Pittscrazy

I have used a 14-channel PowerBox Competition SRS® backer and two redundant Futaba R7006SB® receivers.

Four channels of the backer have been programmed for a total of 8 servos from the device (2 for ailerons, 2 for outer flap, 2 for inner ones and 2 for elevator), leaving the rest of the settings to the transmitter. It is switched from the outside by means of a PowerBox MagSensor® magnetic switch hidden behind the wall of the nacelle.

Except the two analogue throttle servos 58 oz-in (MPX Profi 3BB), the rest are digital coreless Savox®, with titanium gears: 166 oz-in (SC1258TG) the two in the elevator, the two of rudders, both of ailerons and that of the door of the nose landing gear; of 277 oz-in (SC1256TG) the four flap, the one of the steering wheel and the two of the doors of the main landing gear.

This makes a total of 16 servos, although they could be more if we use them for the choke of the engines or for mechanical valves of the pneumatic circuit, for example.
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Old 11-30-2018, 04:31 AM
  #67  
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I opted for simplicity in the management of the chokes: a rod commands them manually, under the same trap door that centralizes the fuel filling and control of the electronic ignition of each engine, in the front of the turbochargers.

In addition, following the advice of my friend Jesús Bagüés, for the activation of the landing gear and its five gates I installed an electronic sequencer with pneumatic FailSafe (Airpower EVSD-SQ-PRO®) rescued from the spare parts drawer, which modulates the Evojet PRO-HV Dual Action® valve for the landing gear and each of the three door servos with a single transmitter channel.





Another PRO-HV Brake® valve, also modulated by the sequencer, controls the pneumatic brake of the wheels when the elevator control is activated.

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Old 12-06-2018, 07:06 AM
  #68  
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I am speechless. What an incredible build and display of craftsmanship. Just simply in awe. Will continue to the end to follow this build. Chic
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Old 12-12-2018, 09:01 AM
  #69  
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Originally Posted by redtail View Post
I am speechless. What an incredible build and display of craftsmanship. Just simply in awe. Will continue to the end to follow this build. Chic
Thanks for your words, Redtail. Really a lot of work but worth it.
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Old 12-12-2018, 09:07 AM
  #70  
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The transmitter used is a Futaba FX-32® with 18 channels, but only 10 have been used due to the mentioned electronic approach. However, if we want some light equipment on board, chokes, folding ladder, functional recovery flaps or dropping fuel tanks under the wing, for example, the number of channels can increase at your own. In my case, I have dispensed with all “extra” functions with the sole purpose of saving weight.

The avionics sits comfortably in the space behind the pilot, under the simulated radio equipment of the real P-38, having used about 66 ft of twisted triple cable 22 AWG for wiring the model and two batteries for its power supply (5 Ah each) located in the front of the nacelle. It is necessary to take your time for making a neat installation, given the huge amount of tubes and cables that converge in this place.



Avionics ready to be in place



Wiring and tubing to be made up. What a madness



At last, everything is in place
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