The Baby Libelle

I have decided to start a new thread for this.
To recap it will be a small Depron 50" scale Glasflugel Libelle, but as a powered glider, to replace the bigger one I lost.

The first little bit - the tailplane.

Sheet 2mm Depron with a 1mm balsa spar on the hinge line.
The leading and trailing edges are sanded to a symmetrical section. Where this has left an 'open' Depron structure is has been filled and strengthened with PVA wiped over the surface.
Top hinged with 'Magic' tape, it weighs 1.8g

Lovely! Do you have a pic of the PVA and tape that you've used please?

Monz
The tape is a Staples product called Invisible Tape.

6 x 1/2" wide rolls for a couple of quid.
Its like Sellotape but it has a matt surface so it is hard to see and you can paint it. Magic tape is the name of the Scotch version.
Used to be used to repair engineering drawings as it did not show up when they were printed.

The glue is just Wicks flooring adhesive.

Bought two 500ml bottles for 50p each from their 'bargain' bin!

Me a skin flint?
Never - just economical!

Subscribed. H201 Libelle is a personal favourite.

The wing will pose a particular challenge.
The full size had the benefit of a purpose designed relatively 'thick' low drag Wortmann section to give a reasonable spar depth. The Libelle was one of the first mass produced all glass designs so the stresses were kept down.
At 50" span using the scale wing section would not work at all well as the smaller you go the thinner it has to be, down to almost just a flat plate at the tips.

The first 2mm Depron wing skin with its integrated tapered 2mm thick balsa spar flange.

The next problem to solve will be the aileron servos. The wing will only be a maximum of 5mm thick at the inboard edge of the aileron. I may have place the servo(s) near the root where the wing has sufficient depth.

If the wing section is going to be so thin, would it be worth considering a very thin carbon tube spar?
I know they're not exactly cheap, but they are very rigid & extremely light.

Pol.

Pol
Whilst I agree carbon or rather carbon/epoxy tube is very stiff but this is really the problem. It is so stiff that it takes virtually all load in a Depron structure so overall it ends up no lighter.
Depron will constitute about 95% of the weight of the wing so my thinking is to use as much of its strength as possible rathan transfer the load to something else. This means you have to accept it will bend, the difficult part is controlling the aerodynamics as it does so.
Of course modern 'glass' full size gliders have got this technique down to a fine art!

Also this amazing video

I hope the Baby Libelle wing will not deflect quite that much!

Quorneng wrote: I hope the Baby Libelle wing will not deflect quite that much!

If I were the pilot of that glider & I looked out and saw things bending like that ..... I'd need clean undies !!!!

Pol.

Eric
Apart from the difficulty of installing it I fear 2 sets of long push rods and 90 degree crank would weigh more than a 2.5g servo!

By far the lightest would be to use an external mono filament pull/pull cable system from a single central servo. It also has the advantage that it is not bothered by wing flex.

Another way would be to have the ailerins spring loaded to neutral position and a single pull wire to give up only.
I remember this system being use on a kit (Graupner?) in the past but can't be more specific.

The wings under construction.

The lower skin is 'formed' to the appropriate shape before the shear web and ribs are added. At this stage only the undersides of the ribs are correctly shaped.
There is no shear web or ribs on the outer 1/3 of the wing as the two skins touch over almost the whole so the wing is basically solid.
The root wing section.

Mildly under-cambered more for scale appearance than anything else.
Each aileron is 10" long but only 3/8" wide at its root tapering to 5/16" at the tip. It has a 1mm balsa leading edge to provide some degree of torsional stiffness.
Each wing half weighs 12g

The hardwood dihedral wing braces either side of the top and bottom spars.

The full 50" wing.

It weighs 0.86oz (24.4g)