Development of a composite twin boom pusher airframe.

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Tags: airframe, boom, compsite, pusher, twin

Comment by Graham Dyer on September 29, 2012 at 8:46am

Very nice, that planform does fly well, I'm on my second and thinking about a third. FWIW, found I needed about 3 deg positive incidence on the main wing relative to the horizontal stab to prevent "tuck-under"

Comment by Leo Hogg on September 29, 2012 at 8:49am

Interesting. On here the tail-booms are inclined 3 degrees to the horizontal. The wings still require laminating.

Comment by Graham Dyer on September 29, 2012 at 8:58am

What's your main wing relative to horizontal? I settled on 3 deg leading edge up on the main wing OR 3 deg leading edge down on the horizontal stab.

Some info and photos here

Comment by Graham Dyer on September 29, 2012 at 9:06am

oh, and I put in about 5 deg of dihedral, critical for nice flying properties, IMHO

Comment by Leo Hogg on September 29, 2012 at 12:18pm

there will be no dihedral angle for ease of construction. I'll check the other figures.

Comment by M Davis on September 29, 2012 at 9:00pm

Where can i find a kit like this ?

Comment by Ravi on September 30, 2012 at 1:13am

what is the exact type of foam used for the core of the wing. what type of surface covering you have applied on the wing surface. the frame is very interesting because of simplicity of construction. what is the wingspan.

Comment by Leo Hogg on September 30, 2012 at 2:30am

Hi all.
Just a few technical details.
Its a Clark Y section (still hard to beat) set at 3deg for a cruise Cl of about 0.6. I will start off with the tailplane at -2. Span is 2.2 meters, chord 290cm. The Fuselage was made by carving a Styrofoam plug, covering in packing tape, then 1 layer (2 in places) of carbon/Kevlar and vacuum bagging. The foam was then hacked out of the wing join cavity. Being an external layup the finish is a bit wrinkly from the bag and its a pain sanding Kevlar as it gets fluffy (I had forgotten about this). Lesson learned- next time finish with a thin layer of glass.
The wing foam is just a pink/orange version of Styrofoam (made in Italy I think), cuts very nice. I was intending to layup 2 layers of 170g glass but am checking my bank to see if I can use 1 layer of 200g carbon (like the tail bits are), should save about ½ kg. No spar as such, just some 50mm UND carbon tape. Than the usual Mylar(subtitle) and vacuum bag.
Am toying with the idea of making moulds for the Mk2 and would probably go a little smaller (2m of less?).

Comment by Harry on October 1, 2012 at 10:30am

I like pushers of single or twin boom.  As for your lost foam technique, I made lost a foam pod once and forgot the packing tape part.  The pod had a hole for pouring in the acetone and the boom exit was where I let it all drain.  I got one interesting benefit from not using the tape and that was the foam dissolved mostly and left a crusty glue like film on the inside.  This foam crust added a lot of strength and durability.  I still smashed it up in a crash, but it is very repairable and will fly again one day.

Comment by Leo Hogg on October 1, 2012 at 2:09pm

Richard, how strange we ended up with the same size and layout.

Just a few more pics.

One shows the avionics ‘shelf’ with Ardupilot and RX. There is a clear window (no carbon) above the Ardupilot for good GPS reception, also so I can see the LED indicators. The fuselage is cavernous even with a large Lipo which is why I think smaller would be OK, but I did make it big enough for an SLR camera. I laid a Kevlar hinge for the canopy which seems to work well. All the servo wires (except ESC) have to go down the wing so I have joined all five (2 rudder, elev, 2 aileron) in an RS232 style connector.  If I crack on with it I may get the wing glassed tomorrow.


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