Scale Glasfugel Libelle 201 - in Depron!

[quorneng]

The wing is now structurally complete.

There is still quite a bit of work to complete the ailerons and some surface filling before it can be painted.

[pmullen503]

Looking good!

[quorneng]

The connections. Battery under the wing, radio above, ESC loose.

Two nylon wing hold down bolts. The canopy clips under the cockpit coaming at the front and by a tiny magnet at the rear.
The only disadvantage with this arrangement is the ESC as well as the ailerons have to be disconnected from the radio to get the wing off.

Complete and painted showing is 84" span. The first time it has been outside!

It weighs 12.5oz (355g) giving a wing loading of 6.3oz/sqft.

[earthsciteach]

She looks great! Makes me want to get started on that AS-W15.

Can you explain the white emulsion/hair spray that you used for the finish?
Thanks

[quorneng]

earthsciteach
First it is not really possible to get a high gloss finish from Depron, the surface is just too rough, but it is completely waterproof so any paint is purely decorative.

Ordinary matt emulsion has very good covering power for its weight and being water based is completely Depron safe but of course the finish is dead matt and rather soft.

Firm hold hairspray actually softens the surface of the paint slightly but dries to a hard silk type finish.
Overall it gives about the lightest weight decoration I have found.

In addition emulsion 'tester' pots are cheap (so is the hair spray!) and the range of colours available is huge.
Just about right for a foamy.

[earthsciteach]

So, do you paint the depron and then spray with hair spray (or potato gun propellant, as I see it) while the paint is still wet?

[JetPlaneFlyer]

She looks really nice, very elegant.
It will be interesting to hear how that narrow chord wing performs at the slow flying speeds a 6.3ox/sqft wing loading should give, it must result in very low Re number. The slightly rough finish of depron might be helpful at those Re, maybe turbulators would help even more?

[quorneng]

earthsciteach
The paint is fully dry and can be lightly sanded to remove any imperfections. The hairspray seems to actually soften the emulsion until it has dried. I expect it is this that gives the hard wearing finish.

JPF
My experience with small chord (<3") wings is they exhibit a rapid rise in drag as the AoA increases and this occurs well before the actual stall which at very low Re numbers is poorly defined anyway.
The result is that if for any reason the AofA is significantly greater on one wing than the other (a slow tight turn?) then 'auto rotation' (incipient spin) will follow even though technically the wing has not stalled.
This effect is even worse on tapered high aspect ratio wings as any differential drag will be acting a long way out!

I do not expect the Libelle to be a 'nice' plane to fly!

[quorneng]

Well it does fly- just about!
CofG too far back so it needed full forward trim and some down elevator, not easy to do when you are using full aileron control as well!
https://vimeo.com/56806521
Drops a wing very readily but actually glides quite well.

No problem to move the battery forward from its position under the wing.

The ground was terribly wet and soggy so I think I will have to wait for field to dry out a bit before trying again but at least it is still in one piece!

[quorneng]

Field still wet but now frozen so a quick test with the battery forward by 2".
Much better although it probably wants to go forward a bit more.
A rather poor video (I kept it quite high) of some rather more 'enthusiastic' flying to explore it characteristics, so much so it lost the canopy!
Finally the strength of the super skinny wing was tested by doing a loop!
https://vimeo.com/57452719