P-38 Pusher MJ - Another variant of twin boom - RC Groups
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Feb 28, 2018, 11:09 AM
a.k.a MJ
azamkl's Avatar
Build Log

P-38 Pusher MJ - Another variant of twin boom


I'm always in passion for warbird and never get tired of it. However, I'm not that good in piloting my RC Airplane and on average, I'll crashed it within less a week. I guess the speed of the warbirds need to be tame to my eye sight and yet still maintaining it's characteristic It doesn't have to be fully glider tho.

I need something that closet to the actual model of warbird and yet easy to be build in the nick of time if I crashed one. For that reason, I choose P-38 to be my next project. Instead of using a dual motor at front nose, I my self prefer it to be a pusher with single motor setup..more on the economy side and I'm not intend it to go fast.

What do you guys think? Any taker on this build log? I'll update it as I'm progressing on it.

Any comments and ideas are welcome.
Last edited by azamkl; Mar 28, 2018 at 04:34 AM.
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Feb 28, 2018, 02:00 PM
An itch?. Scratch build.
eflightray's Avatar
Speed is controlled by the throttle, and by keeping the weight down, (wing loading).

Bigger models usually appear to fly slower, (easier to see what's happening), plus the greater wing area helps with keeping the wing loading down, so don't go too small.

Your design looks Ok, though hand launching pushers do need some care, if you want to keep your fingers.

Controls ?, throttle, ailerons, elevator ?, (rudder isn't really necessary).

Choose a recommended KFm section, (sorry I can't recommend one), keep that weight down, but keep the wing strength suitable for the maneuvers you want.

I have a profile Mosquito, great flier, but the wings do bend a bit pulling out of loops.

.
Feb 28, 2018, 09:20 PM
a.k.a MJ
azamkl's Avatar
Thanks for the chips in eflightray.

Wing loading are one of the criteria that I was tinkering back and forth. Currently, the wing span that had in my mind is 42inch. Since I planned on using a single motor, equipped with let say Turnigy 2200mAh 3S 25C Lipo Pack, should be light enough and for it to fly slow. Furthermore, instead of KFm, I'm planning to have an airfoil shape to what generally Flite Test team are doing.

The controls mainly involve a throttle, elevator, and aileron. Rudder will be static as it is. This one, landing gear should be part of the design build due the prop that does not have enough ground clearance with out landing gear.
Mar 12, 2018, 08:24 AM
a.k.a MJ
azamkl's Avatar
Plan will follow soon. Need to maiden it first.
Last edited by azamkl; Mar 19, 2018 at 09:09 AM.
Mar 28, 2018, 04:28 AM
a.k.a MJ
azamkl's Avatar
Considering the main challenge of designing this airplane, tracing from the original blueprint of it and convert it into a 'pusher' type aircraft will be a bit tricky. This is due to shifting the COG of the original plan. Logically, you will have a tail heavy plane when the motor is being place at the back of the fuselage instead in the front.

I have thought of that and that's why there will be a slightly different from the original plan onto what I have in mind. I have made the nose area inside the fuselage area suit enough to have the battery move back and forth to compensate the COG with different batteries of choice.

Power Plant Setup
For this build, I choose the motor that available from the scratch plane I have laying around. And since it is a single pusher, I have the suitable candidate for it.
Motor: Turnigy 1450kv
Prop: 9x6 (recommended 8x6)
Lipo: 1800mah 3C
ESC: 30A
Servo: Micro 9g servo x 3. (Aieleron x 2, Elevator x 1)



Maiden Video

The maiden pretty much a breeze with light wind blowing, the aircraft flew straight up with less twitchy or banking left and right.
P-38 Pusher MJ (8 min 27 sec)
Last edited by azamkl; Apr 08, 2018 at 11:34 AM. Reason: Updated the plans
Mar 28, 2018, 11:34 PM
Registered User
Looks great! I love when someone starts from scratch and builds something new.
Mar 29, 2018, 07:05 AM
a.k.a MJ
azamkl's Avatar
Quote:
Originally Posted by Rick M
Looks great! I love when someone starts from scratch and builds something new.
Thanks Rick. I really love to explore the possibility to have every aircraft being converted into pusher type
Mar 29, 2018, 09:55 AM
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Lawn Dart Flyer's Avatar
I love it, even looking at it thru a cell phone i like what I see. i will take a closer look when I get home.
Mar 29, 2018, 08:00 PM
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Lawn Dart Flyer's Avatar
I sent the plans to my local reprographics shop, hopefully they will deliver in the morning. I'm not sure when the build will start but i will keep you informed when it does. I already plan on a few mods such as elevator servo, i'll figure out somehow to relocate it inside the wing or at least on the side of the boom. Same as aileron servos, going to move them inside the wing.
Mar 29, 2018, 10:25 PM
a.k.a MJ
azamkl's Avatar
Quote:
Originally Posted by Lawn Dart Flyer
I sent the plans to my local reprographics shop, hopefully they will deliver in the morning. I'm not sure when the build will start but i will keep you informed when it does. I already plan on a few mods such as elevator servo, i'll figure out somehow to relocate it inside the wing or at least on the side of the boom. Same as aileron servos, going to move them inside the wing.
Can't hardly wait for you to start the project. It's really a simple build and based on the design, I tend to kept it as simple as possible and yet give it some details looks as close as I can get. If you can see from my build log pictures, I haven't got the time to tidy things up as I was rushing to take it to maiden Any mod that you can think of are most welcome.

Btw, does landing gear included in your mod? Would like to have that too
Mar 29, 2018, 11:07 PM
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Lawn Dart Flyer's Avatar
Yes I can do landing gear, not sure I want to though as this adds weight and drag.
Mar 31, 2018, 09:31 PM
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Lawn Dart Flyer's Avatar
I have started the build. It's all cut out, the fuse is built, the pods are joined. I have run into an issue withe the wings, 2 of them actually. Once wings are scored, beveled etc the bottom covers the aileron, easy fix there when the time comes, just need to cut the bottom piece.
Second issue is i don't think the cut out for the wings thru the pods is correct size, they are to small. Keep in mind I am using true Dollar Tree foam board that is 4.5mm thick.
Mar 31, 2018, 11:45 PM
a.k.a MJ
azamkl's Avatar
The bottom part of the wing should be less in length compare to the top cover. It it exceed up to the aileron, some trimming needed. I would suggest you to increase the aileron depth to get more authority on those ailerons. From that measurement, you will figure out how much trimming needed for the bottom cover.

Yeah, I knew the wings dimension won't be a snug fit to the fuselage and tail boom opening. Also need some trimming for that part
Apr 01, 2018, 09:47 PM
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Lawn Dart Flyer's Avatar
I have mine done, adding pics of aluminum spar i added in the wing, this will be needed if i add landing gear later. Flying weight with a 2200 3s is 540g, i needed my largest 3 cell all the way in to balance it. No maiden yet.
Last edited by Lawn Dart Flyer; Apr 01, 2018 at 09:58 PM.
Apr 02, 2018, 02:57 AM
a.k.a MJ
azamkl's Avatar
Mine end up with AUW 620g. For the lipo, I tucked it all way forward and in some old newspaper to cushioned it up during flight

Seeing from your image, I like it how you nicely arrange the servo. Nice and tidy. Looking forward for your maiden video and flight report.


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