T38 Depron Foam Electric Jet

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T38 Depron Foam Electric Jet

Postby uplink » Tue Jul 17, 2012 9:48 pm

T38 Foam Electric Jet

Built from downloaded plan and 6mm Depron Sheet.......... plans at http://www.rcgroups.com/forums/showthread.php?t=1066708

Jan2012 006LoPixels.jpg

Quite a few pieces to this one.



T38 build 2012 018LoPixels.jpg

View of the rear fusalage showing the all moving tailplane, which pivots on it's carbon fibre spar and I descided to modify things to include thrust vectoring - note the extra servo for this linked to the pivoting ply motor mounting plate.



T38 build 2012 031LoPixels.jpg

And the finished plane.

It's had about 6 flights to date using a 3 cell 1800mAh 20C Lipo from Giant cod - gets about 6 minute flight on one year old battery - Very fast roll rate due to the short wingspan but the long fusalage means loops are large... until you switch in the thrust vectoring and then they tighten considerably.

Despite the long nose, flight is quite stable with no bad tendencies and with 3 cells, it's not slow, but not super fast.
Not a beginer's plane, but not that difficult to fly, so most would probably be ok with one of these as a second plane - following on after you really feel comfortable flying your trainer.

Cost of the Depron and carbon fibre, control horns and glue for the airframe came to under £15 and I should think it took - from downloading the plan and cutting the foam and gluing all together, I took about 5 days - I spent about a day figuring how best to do the thrust vectoring and building that bit - and the all moving tail 'bearings' slow you down a bit because they need to be accurate, free moving, level and square on to the fusalage - and there are a lot of parts to this plane.

It's a foamie, but it's a builder's foamie and most enjoyable to put together.
Now THAT'S a thermal.

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Re: T38 Depron Foam Electric Jet

Postby uplink » Wed Jul 18, 2012 7:13 pm

T38 build 2012 017LoPixels.jpg

A hinge for the thrust vectoring ply motor mount was initially a small commercial brass hinge, but it had too much play in it, so I made one from a short length of approx 3mm diameter piano wire, which was a moveable but snug fit through 3 pieces of brass tube - 2 pieces fasten to a ply tongue in the plane's centre plate and the third one fastened to the motor mount.



- 042LoPixels.jpg

The wing's carbon fibre reinforcing tube taped in place in it's wing-slot - if you fix it like this, then the rod is nice and clean and not covered in epoxy - so you can easily re-use it in your next plane - after all, this carbon tube represents about 20% of the cost of the airframe - just make sure the tape you use really sticks well to the foam.
Also you can see the extra pieces of foam I've added to the wings - the grey pieces - simular pieces added to the top of the wing too. These 4 pieces maintain a symetrical aerofoil section, so it will fly well inverted and not only do they add stiffness to reduce wing twisting but they improve the aerodynamics of the otherwise flat plate wing section.
They are cut to occupy approx the front 40% of the wing cord measurement with the leading edge rounded as per a normal aerofoil section but their rear edge left as an abrupt vertical - the theory is that a long thin rotating sausage shaped votex is generated right behind this abrupt vertical edge and the main air flow then skims over this rather as if the wing had a conventional aerofoil section. The upshot is that the power-off glide angle gets improved - maybe from something like a 1 in 3 descent to I would guess about 1 in 4 - whatever, it is a noticable improvement with them fitted.

This, by the way, is called a KF4 aerofoil and here's a couple of You Tube links saying a bit more about them....
http://www.youtube.com/watch?v=ROHE-YpV4Kk
http://www.youtube.com/watch?v=A4oa-yagPp0



2012-05-xx 002LoPixels.jpg
Now THAT'S a thermal.

User avatar
uplink
Posts: 830
Joined: Fri Nov 16, 2007 9:51 pm
Location: Ravenshead Notts

Re: T38 Depron Foam Electric Jet

Postby uplink » Sun Dec 22, 2013 5:32 pm

T38 i.JPG


T38 ii.JPG


T38 iii.JPG
Now THAT'S a thermal.


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