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4 Engine Scratch built Bomber

Posted: Sat Mar 12, 2016 7:07 pm
by Vipertech13
Hi all! I have been kind of out of the loop for a while, Just some life changes making it tough. I thought I would share my 4 engine "bomber" scratch build with you guys and share the maiden test flight. A little back story, this started out with my oldest son wanting to do a multi engine/motor plane before he was married and we gathered the parts and set on the Flitetest P-51 mustang wing as our jump off point for the plane. We made the wing following the basic design but stretched it to 58" and that is where it stopped, he got engaged and busy with his bride to be then married and he left it all set here. So this winter he said do what you want with the stuff. I decided to finish what we started! I designed the fuselage from scratch after looking at bombers and other aircraft for hours.
Here is what I drafted up in windows paint.
bomber side LG.png
bomber side LG.png (40.7 KiB) Viewed 8425 times
horz and tail.png
horz and tail.png (23.37 KiB) Viewed 8425 times
bomber.png
bomber.png (24.2 KiB) Viewed 8425 times
I started to built this monster and all I can say is more motors mean more wire, more weight, more headaches. I mounted the esc's in a vertical rack system to make it easy to connect the motor wires coming from the wing access port.
esc compartment.jpg
esc compartment.jpg (152.12 KiB) Viewed 8425 times
motor wires.jpg
motor wires.jpg (130.23 KiB) Viewed 8425 times
To keep the Rx working I incorporated a UBEC running off a separate 1000mAh LiPo that has an external switch and voltmeter.
electronics side.jpg
electronics side.jpg (118.5 KiB) Viewed 8425 times
The motors are counter rotating of course and run off 2 separate 2200mAh batteries the outboard engines are together and the inboard are together that way if I have a failure of a battery or esc I don't lose all or one side of the plane. From this top view you can see the 2 square holes for the batteries.
full plane.jpg
full plane.jpg (134.86 KiB) Viewed 8425 times
Some of the specs.
58" wingspan, wing cord tapers from 10" to 5" center to tip.
Fuse length 40".
(4) 2822 1100Kv motors swinging 7x5 props,
(4)20 amp esc's with bec circuit disconnected
(6)10 gram servos, 2 aileron, 2 flaps, 1 elevator and 1 rudder.
3 batteries (2) 2200 3s, (1) 1000 3s (1) UBEC 5 volt 3 Amp output
Aluminium landing gear with 2.75" dia. tires Steerable tail wheel
All up weight is 3.48 lbs
The engines are producing 3.0 Lbs of static thrust according to my redneck thrust tester.
thrust test.jpg
thrust test.jpg (99.09 KiB) Viewed 8425 times
Bottom view with yard stick for size reference.
IMG_20160223_000052 (1024x768).jpg
IMG_20160223_000052 (1024x768).jpg (32.74 KiB) Viewed 8425 times
Side view
IMG_20160223_000424 (1024x768).jpg
IMG_20160223_000424 (1024x768).jpg (30.76 KiB) Viewed 8425 times
Well that's quite a lot to take in! I have flow a maiden flight and it was not too good! Major miscalculation on the CG and too much control surface throw and that might have been exaggerated by the tail heavy CG.
http://www.youtube.com/watch?v=0WZfytUbMmw
More work to do so Bomber 2.0 soon

Re: 4 Engine Scratch built Bomber

Posted: Sat Mar 12, 2016 7:11 pm
by Graham Lawrie
Thats well cool:)

Re: 4 Engine Scratch built Bomber

Posted: Sun Mar 13, 2016 3:18 pm
by Lee
Nice job Gerald :)

Re: 4 Engine Scratch built Bomber

Posted: Mon Mar 14, 2016 12:06 am
by Derek
OH WOW! That looks pretty cool, Gerald! I'll be watching for the flight video on this plane!

Re: 4 Engine Scratch built Bomber

Posted: Mon Mar 14, 2016 4:03 am
by pvolcko
That looked like quite a handful!

Re: 4 Engine Scratch built Bomber

Posted: Mon Mar 14, 2016 4:51 am
by cml001
Look'n nice there buddy!

Re: 4 Engine Scratch built Bomber

Posted: Sat Apr 02, 2016 3:16 pm
by Vipertech13
Here's an update!
Repairs have been made and a recalculation of the CG has yielded a location difference of 2" more forward than what I initially flew it with! Yikes!
That was my mistake in the calculation of the CG, lesson learned!
I have opted for the 3 blade props to look more classic bomber style and slightly more ground clearance, trade off being a slight drop in maximum thrust of less than a 1/4 lbs. but draws 5 amps less and the thrust has more of an even curve. Where the 2 blade props would punch 3 lbs static at full throttle the thrust would drop quickly to 2.4 lbs. the 3 blade props punch 2.8 lbs but only drop to 2.6 lbs and hold there for a long time. Again this is my not so scientific static testing using a scale against the wall and the plane's nose up against it.
I have relocated the landing gear to accommodate the more forward CG point to keep from nosing over! We have been there haven't we Derek! LOL
Painting is underway as of now,
front side close
front side close
IMG00002.JPG (789.3 KiB) Viewed 8393 times
bomer front
bomer front
IMG00001.JPG (777.2 KiB) Viewed 8393 times
bomber top
bomber top
IMG00003.JPG (833.86 KiB) Viewed 8393 times
The battery and wire compartment with my esc to motor color connection chart.
bomber hatch
bomber hatch
IMG00007.JPG (764.62 KiB) Viewed 8393 times
wiring diagram
wiring diagram
IMG00006.JPG (685.52 KiB) Viewed 8393 times
And of course my switch and volt meter.
side with vm
side with vm
IMG00012.JPG (783.85 KiB) Viewed 8393 times
Would love to be re-maidening it this weekend but it's raining this morning and wind forecast is 10 to 20 today and tomorrow with 50 mph gust tomorrow.
GROUNDED!

Re: 4 Engine Scratch built Bomber

Posted: Sat Apr 02, 2016 6:13 pm
by Graham Lawrie
Cool:) Soon :) soon:)

Re: 4 Engine Scratch built Bomber

Posted: Sat Apr 02, 2016 7:38 pm
by Derek
Very nice!!!

Re-Maiden of the 4 Engine Bomber

Posted: Thu Apr 14, 2016 2:04 am
by Vipertech13
OK here is the second go around and it went very well! It was a little windy and the audio was bad so I just voiced over the video. Volume is a little low because I am learning how to use new editing software.
https://youtu.be/qUqEM7SUosw

Re: 4 Engine Scratch built Bomber

Posted: Thu Apr 14, 2016 8:05 pm
by Stambo
Much better Gerald, now make it drop something. :)
You can't have a bomber that doesn't drop bombs. :D

Re: 4 Engine Scratch built Bomber

Posted: Tue Apr 19, 2016 8:43 pm
by danhampson
Haha candy drop.
Sweet plane Gerald

Re: 4 Engine Scratch built Bomber

Posted: Tue Oct 18, 2016 7:06 am
by Harper88
Simple but precise build.