scratchbuilt 2m span airframe for 200g+ payload

331i17a.pngHere's a brief wee build log of a plane i promised myself I would make. I'll make the simple plans available for anyone and everyone.

Any suggestions are very welcome !

 

It's mission is to carry a nikon L4 to take some aerial photos, with an efficient wing optimised for a cruise at about 35 km/h.  It must be stable and fairly easy to fly,have a pusher prop configuration and be easily constructed for those with little experience (me :D) : hot-wire cut wings and tail, a wood fuselage, and a GF tube tail boom.

 

Since i'm on a budget, it's to be powered by a 3s 3300mah Lipo, a cheapo 2212 outrunner and 9x6 prop; just what I had lying around. However I have left space for a bigger battery and a 10" prop.  A nikon L4 is about 8.5 x 5.5 x 2.3 and some 180g.

 

I started off by designing the wing, learning to use xflr at the same time. heres what it looks like 'on paper'

Just a simple 2412 airfoil, with -2.5 degrees twist for better lift distribution and hopefully to make stalls controllable.

Wingspan is 2m exactly, with an 18cm root going to a 10 cm tip, with an offset of 2 cm back.

Theres no dihedral here, because i'm not 100% sure about the construction yet.  If i decide it will be easy enough, it will have at most 2 or 3 degrees of dihedral.

 

I moved on to the fuselage next, making LOADS of sketches on paper, settling for what i thought is the best layout (obviously).  It's easier to understand a picture of the fuselage halfway through construction than it is to understand my drawings:

6j34nq.jpgthe aluminium bar represents the wing and don´t worry, that tail is just a couple of offcuts taped on for visualtisation.

The construction is all from a board of liteply, or at least thats what I think it was, its from a DIY store.  It's 4.5mm thick ply and simply glued together, with the boom tight-fitted into a hardwood block also glued into the fuselage.

 

the 'cargo bay' is at the front and is 7.5 x 10 x 5.5 (5.5 at the lowest point, at the front), it could easily have a shelf put in the middle if it is to have APM xbee gps imu tnt ymca and whatever else packed into it.

If at this point you´re thinking 'mate, don't even bother making plans this thing is a flying brick' then i totally agree with you.  But don't worry, it's going to get some pretty foam fairings outside to smoothen that square shape up!

 

heres another pic showing the servo tray at the back

30bmcz7.jpgthe shelve at the back is the servo tray with LOADS of room for the Rx and ESC, the lump of wires is a dud 3s 3300 for illustration, and theres still alot of room for whatever you may be wanting to carry. like some delicate modelling tools :P

 

I then set about making the tail surfaces. It took alot of practice to figure out how to cut nice cores as you can see from the pink mountain, and i'm hoping the thick wing will be easier than cutting the wafer thin tail

s1kdao.jpgJust a piece of steel wire strung between bits of wood, an a transformer from an ex-amplifier regulated by a dimmer switch.  At 9v it draws about 13 amps and produces the best temperature for cutting the pink foam I have.

The big coil of wire on the board is a makeshift resistor otherwise the small wire used for the tail was too hard to regulate, its resistance is very small and merely brushing the dimmer made too much of a temperature difference.

 

UPDATE

 

okay the wings have been cut out, I recommend slow and cold for cutting foam! it took alot to get it right.  Since I ran out of foam i put balsa leading and trailing edges, and a black spongy foam nose for the impending impacts it's gonna have :D

 

23safk2.jpg

finished fuselage (minus hatch), wing (glue drying), and one awesome foam cutter as long as you have 4 hands available :D  Thats a 10" prop on it.

 

BUT between seeing people and doing nothing over the holidays, I ran out of time for this project, ending at just needing to attatch the ailerons and go fly!  the wind didn't permit this, so now it's waiting in my parents garage for me to come back and give it it's maiden in easter  -.-'  I'll tell anyone watching how that goes . .. .

 

Hamish

 

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Comments

  • well sadly it died on the maiden . . .no aileron control.

     

    before ( have no shots of it on its own )

    3692202889?profile=original

     

    after3692202990?profile=original

    Broken nose and wing, rudder came clean out.

     

    at 950g all up weight w/o camera, it flew pretty well for the first millisecond of the flight but soon i realised there was no aileron control !!  It was windy so it came down hard . .. It nosedived into the gravel track and lost the nose and half a wing broke, so i'm glad i made the fuse out of 6mm plywood!

     

    So what did i learn?  IF you make long skinny wings out of foam, you must skin them!!

    My wings were too weak and were twisting in flight when the ailerons deflected, balancing the aileron effect hence not turning.  Pas good.

     

    Other than that it had plently of lift and tail authority and i still have faith in the rest of the design, but don't expect to ever make it again.

     

     

    And just for a cheap lol...With all this talk of the turnigy 9x, i still have a chuckle everytime I fly with this:

    3692203061?profile=original

    Old enough to tell us it's digital !    wooow. Wrapped around it is the trainer lead I had to solder in, no trainer ports back then.

     

  • Hey Hirmish

     

    I see I'm not the only one with a foam cutter that is basically some block of wood, a power supply and some toaster wire. Does the job just fine. The aircraft is looking good. hope to see the finished product soon....

  • Yes I absolutely agree that all ply is an overkill and too heavy, but I don't have time really to make pretty cut outs, plus the landing is going to be on rocks and dry bushes if nobody is around to catch it!

    as for the motor, i was a little concerned about the pitch too . . . I actually considered twin booms to put the prop in the middle. But then again, planes generally pitch up when the throttle is opened so a little down moment shouldn't harm :D
  • The all ply body seems like a bit over kill.  Additionally placing the motor above the wing may detract from your stability, although you still have your other heavy bits below the wing.  I think with this set up you may find a noticeable change in pitch with adjustments of the throttle.
  • Heh, the wing's going to be much wider than that too !  It's got to be finished before the 8th so expect a finished photo soon!
  • Distributor
    Hi Hamish, great to see this project taking shape. I thought the aluminium bar was some very interesting profile till I read the text. Can't wait to see the finished air frame.

    Regards

    Martin
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