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Glasflugel H301 Libelle

#1
The Glasflugel Libelle (Dragonfly in German) was an early all glass fibre 15m open class glider.
At the time it had a performance quite a good as any glider around.
Compared to equivalent wooden gliders it was quite a bit lighter and was extremely easy and quick to put together. Most of the controls connected automatically as the wings and tail were put on. It was also 'clever' in engineering terms as the wings were fixed in place by a single pin and the tailplane by a single 5mm bolt!
The Libelle like all high performance gliders has a very high aspect ratio wing which means that at even 76" span the wing chord is only 5" at the root and half that at the tip.
Small-3view.jpg
As the canopy covers the wing it allows the use of a one piece wing so the challenge is a true scale 76" span 'electric' Libelle and just for fun built in Depron! ;)

I have posted this in the wrong place. It is repeated under Gliders and Slope soaring. Perhaps a moderator could delete this?

I have posted this in the wrong place it has been repeated under Gliders and Slope soaring.
Perhaps a moderator could delete this?

The fuselage is built in two halves using a former and plank construction.
FormersA.JPG
Slow and tedious as each plank has to be shaped to fit.
Fuseplank.JPG
but you get there in the end.
RHplnkcmplt.JPG
To be continued!
 
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#2
With the half fuselage complete the formers are added and the inside lining of the cockpit area.
CpitInside.JPG
This lining is important as it provides addition strength & stiffness in the area of the canopy.
The elevator servo is mounted in the tail.
ElevtrServo.JPG
The remaining half of the fuselage can be planked and the tail plane added.
TailAdded.JPG

To take into account the maximum length of Depron sheet the wing is built in 3 sections but permanently joined into a one piece wing.
The short centre section generates the dihedral and also modifies the scale thick Wortman section at the fuselage, necessary for a scale appearance at the fuselage, to a rather thinner section for the rest of the wing.
RootSctn1.JPG
Note the wide spar flush with the wing surface. The balsa spar flange is only 0.8mm thick.
The centre section mounted on the fuselage.
FuseWings.JPG
The radio is mounted in the fuselage above the wing.

So far so good.
 

earthsciteach

Moderator
Moderator
#3
Absolutely stunning! I've seen your progress over on Wattflyer.

Have you done anything to smooth the surface of the plane due to the method of laying multiple strips over the internal structure? From the pic above, it sort of looks like you may have. If so, what is your method?

Love your builds. Keep them coming!
 
#5
Ooops! How embarrassing! I just realised I have duplicated this in the 'glider' topic!

But to answer the question yes the fuselage has been sanded with fresh 80 grade on a block to smooth out the surface between planks. It has to be fresh very sharp sand paper otherwise it clogs and leaves marks on the Depron.
The planks have to be glued on with PVA glue as this dries hard. UHU POR on the other hand always remains slightly 'rubbery' and is almost impossible to sand so it leaves a 'ridge' at each joint.
Sanding Depron removes its skin leaving the relatively coarse underlying cell structure. The Libelle fuselage is given a coat of white emulsion which nicely fills the surface nicely and then a coat of hair spay to give a silk sheen!
A true gloss would add too much weight.