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Clean Sweep!


Tim Hooper
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......and wood has actually been cut and glued together!
 
The bottom wing skins have been edge-joined, and marked up with the rib and spar positions.
 
The tailplane has a 1/8 stripwood core, and is veneered top and bottom with 1/16 sheet.
 
 
I thought I'd better check if there's enough room for the motor and cell pack.
 
 
Now I need to visit the model shop to get some nice hard 1/4 sheet for the spars...
 
tim
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Hi Tim. love your practical way of finding the CoG, I like it. One Question I think I have asked before, that is wing incidence. I see from the glider that the wings and tail seem to be at zero incidence. Is this the way to go with OD models, then fly the glider to see if any alterations are needed ? . Or is it far more complicated than that. Cheers FB3

Edited By fly boy3 on 13/05/2011 20:42:51

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Steve,
 
I don't think there'd be any problem with using, say, 3/8 or 1/2 sheet for the wings. I recall that Nige Hawes 54" Tucano (the one that crossed the English Channel) also had a solid wing. Might stand up to the vibration and stresses of a retro glo-motor too!

FB3, you're right about the tail incidence being set at 0°, but the wing on both the chuckie and the full-size model are set at +1°. If there'e no built-in wing incidence, then I've usually found that I've needed to dial in some up trim on the elevator.

Anyway, spars and ribs were added to the wing panels last night and this morning.

 
We had a meeting of the Steering Committee of the Ruling Co-operative this morning (over coffee and biscuits) and decided that, as drawn, the aft end of the fuselage looked a bit tubby and shapeless as it was. So out came the eraser and crayons again...
 
 
Any improvement?
 
tim
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Hi Tim ,
 
Sorry to put the cat among the pigeons but it looked fine as it was .
 
And if we are going for speed , in my experience we need control surface to be large with very small amount of movement to keep the drag down . As opposed to small surfaces with large movement which does cause drag and slows the plane down .
Harder to set-up and no slop allowed .
 
And another tip Wax .
Just like surfers wax there board before surfing to go faster , i find waxing the plane before flights with car polish helps ...........but only if you need the edge .
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Myron! Welcome back to our resident curmudgeon!
 
I hear what you're saying about the fin height - the tailplane possibly being masked at high AoA figures. I think I'll stick with it though and see what happens. To make any noticable difference would mean quite a hike in the height of the fin, I'm guessing.
 
Stephen, we're going all out for speed here. I just something a bit nippier than my usual cartoon scale plodders, that's all.

To accomodate the sweep of the wing, I've made the dihedral braces from 1.2mm aluminium sheet (with a slight bend in the middle), epoxied to the fronts of the spars. There's 20mm of dihedral under each wing tip.


Clamps removed.
 
Then I added the mounts for the aileron servos.

Overall view.

Edited By Tim Hooper on 15/05/2011 09:38:47

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Tim
A beautiful build to your usual high standard.

An interesting dihedral brace.
Personally I am a bit dubious about mixing aluminium and balsa as both their strength and Young's modulus are so different,
 
I am sure your solution will be plenty strong enough but if the balsa spar itself is adequate why not join it with balsa as well, but then that just me being fanatical about weight again!
 

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technically, and theoretically, aluminium does not glue very well to wood. I was informed of this some time back when I had planned to use an aluminium brace on a large ( 72" ) wing centre section joint I had created on a particular model, in order to fit it in the car.
Unfortunately, the model was totalled early in life, and upon recovering the significant wreckage, guess which joint was the only one still intact
I had roughened it up well with a very coarse permagrit plate, and ensured it was spotlessly clean and wiped with Iso pro alchohol before the epoxy was applied.
 
I'm sure Tim's meticulous attention to detail will have been deployed here also.
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HI Gents!
 
Youngs Modulus? I think I had one of their albums back in the 80's......
 
As Timbo suggested, I roughened up the brace with a file before installation. As an aside, my Bristol Freighter features ali braces too, and it's still flying after 6 years service. So we'll see!
 
tim
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Now this looks so 'right' that it should fly perfectly. Not enough forward sweep to cause any aileron reversal problems from flexing.
 
Its very common to epoxy aluminium to wood (especially in microlites) and the alloy is surface etched. If you cant do this then roughen it and degrease with acetone is just about as good - just not certified by the CAA.
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Thanks Wolfie, that's very reassuring!
 
A bit more progress today. Now that the wings are skinned top and bottom, it was time to cut the ailerons free.
 
I've also been hacking at the wing tips....

 
This evening I set to work on the fuselage sides.
 
tim
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Not much speed over the last fews days, Tom. I had a few repairs to make to other models.......

Anyway, some heavy-duty plywood cutting today as F1, 2 and 3 took shape (along with the wing and u/c mounts).

 
F1, 2 and 3. Some things just never change....
 
F2 and 3 get acquainted with the fuselage side.

tim
 
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seems nice and easy to build looks good

Edited By Rusty on 26/05/2011 01:00:47

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