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Jul 14, 2019, 07:57 AM
Anti-gravity = Lots of Watts
Gnat666's Avatar
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Bell P-39 Airacobra


Bell P-39 Airacobra
Inspired by the prolific work of Lynxman & more stuff by localfiend & others ... I'm attempting to contribute to the community with my own creation.
I selected the P-39 as its one of those few "long nose" WWII planes (better for balancing 3D Printed planes) ... and of course, its cool!
- Wingspan 885mm
- Airfoil : under-camber for high lift
- Power plant - Unknown just yet
- Likely just a belly-lander, but I will make "holes" for fixed wire or printed undercarriage.
- Bank-n-Yank - No rudder at this point, but it won't be hard to articulate whats already there, later
- Designed to use a round 45mm click-in "power-pod" that will hold the motor & ESC, can be pulled in/out of the plane easily
- Uses a bit of 5mm carbon rod for the first fuselage to wing joints, otherwise just little bits of 4mm wood dowel as joining guides
- Fuselage - 3 bits (nose 180mm (70g) / mid 200mm (100g) / tail 300mm) (yes, sorry, I have a CR10)
- Wing - 2 bits (320mm (70g) / 62mm)
- Est Weight without electronics : 650g

.... WORK IN PROGRESS

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Jul 14, 2019, 05:14 PM
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Dirty Dee's Avatar
Very cool! I was actually considering making a 1100mm P-39 recently.
Jul 14, 2019, 05:39 PM
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Lynxman's Avatar
I've always liked the P-39.
Jul 17, 2019, 03:30 AM
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japim's Avatar
Awesome! I would be very interested in buying the STL files from you. Or parasolid external silhouette so I can re-design it on my own
Jul 17, 2019, 11:09 PM
EDF all the way!
bruff's Avatar
Same here on the files.
Bob
Jul 19, 2019, 04:39 AM
Luis Claudio - Rio - Brazil
Luis_Claudio's Avatar
Amazing!
Jul 21, 2019, 11:23 AM
Anti-gravity = Lots of Watts
Gnat666's Avatar
Thread OP
Thanks guys.

Some more WIP shots.
Rigged the tail surfaces.
Fixed up the canopy which wouldnt print (too much overhang).
Added magnet holes.
Fixed up the wing tips
Added through holes for optional fixed landing gear
Added lots of "bed hold-down tabs" everywhere
etc

Just about ready to design the power-pod .... think I'll be using an NTM 2830 1100kv on 4S
Jul 21, 2019, 04:21 PM
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Lynxman's Avatar
It looks superb.
Jul 21, 2019, 05:38 PM
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japim's Avatar
2830 may be a bit small. 3530 or 3636 seem to be right or at least make sure you can fit all of them with an adapter and no need to redesign whole nose piece.
Jul 28, 2019, 12:07 AM
Anti-gravity = Lots of Watts
Gnat666's Avatar
Thread OP
More test prints and dry fit-out ....
Looks like total "all-plastic" weight will be about 550-600 grams.

Now on to designing the Power-Pod, then just about done with design (well, rev 1 anyway ).

Quote:
Originally Posted by japim
2830 may be a bit small. 3530 or 3636 seem to be right or at least make sure you can fit all of them with an adapter and no need to redesign whole nose piece.
Yeh, think you're right. Plus I guess I prefer to not right being under powered out of the gate.
Happen to have a NTM 3530 1100kv ... looks a winner. Plus it will still fit in my Power-Pod diameter.
Jul 28, 2019, 02:45 PM
EDF all the way!
bruff's Avatar
Very nice!
bob
Aug 17, 2019, 08:39 AM
Anti-gravity = Lots of Watts
Gnat666's Avatar
Thread OP
More progress pics.
Renders, Spinner, Fuselage stuck together, Servo mounting rig & the PowerPod ....
Black canopy outline is just Sharpie on the raised detail, quick & dirty on the prototype print.
Aug 17, 2019, 10:46 AM
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atreis's Avatar
Very nice. I keep looking at the HH one and not pulling the trigger. Might just go this route instead after the files are released.
Aug 17, 2019, 11:19 AM
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japim's Avatar
Sharpie does the job good enough. Aren't you afraid that the double wall design (outer shell and inner straight walled structure) makes the design too heavy? I really like it though, and I was considering similar approach but there was always the extra weight consideration...
Aug 17, 2019, 11:55 AM
Anti-gravity = Lots of Watts
Gnat666's Avatar
Thread OP
Quote:
Originally Posted by japim
.... Aren't you afraid that the double wall design (outer shell and inner straight walled structure) makes the design too heavy? ....
Good question, but no. Considering it looks like it'll be 600-700g printed weight, thats lighter than some but not too dissimilar to many similar sized printed planes.
Considering theres almost nothing inside the hollow body, you can almost consider the inner walls having a similar weight to the MANY ribs and reinforcements found inside some of the other designs.

BTW, the outer-walls aren't so flexible (under fingers for example) as some might think, the "panel" detail I gave it was aimed to strengthen the outer body, and it did.


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