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A replacement discus launch fuselage for very little money

There are now more than a few dlg's in the Peterborough club. By their nature they are built light to launch high and do not suffer hard arrivals without damage. Consequently, some of our number have had to rebuild , order or rework broken fuselages. Due to supply and demand, the supplier is not always in a position to support spares. These notes suggest a design method for a dlg fuselage to get you to quickly and cheaply back in the air.

Vladimir's Elf, Blaster, Snipe fuselage design has much to commend it, basically a CF boom with the nose section halved and filled with epoxy/micro balloons. Avionics installation is simple and easy to get at, modify and service. This design fostered my version of this design using 12mm x 0,5 mm CF rectangle spaced with soft balsa and with a cut down CF boom. See the attached sketch below. This variation saves having to mill/dremel/file the front of the boom to get a 'half' and avoids filling it with (heavy) epoxy/micrballoons.

The first version of this design weighed 25 gms bare for a 25% enlarged OD Elf. With fin, rudder and stab weight was 30.5gms.

The 'pylon' on the wing mount posts is a push fit and is hollow to accept ballast.
You do have to remove the wing to fit it, alas.

This was not a complete success, I used a Skyshark 2PT (E36) boom and it was just too flexible for discus launch. The fuselage was remade with a cut down F1B boom , again for a 125% Elf clone, shown below. Weight bare was 31gms.

A spare Blaster (5gm) sheath was pressed into service and locates on the 3/8" sq balsa peg mounted on the top of a pair of cheap Gening digital servos. Gear layout is unremarkable and needs no explanation. Surfaces are torsion bar/pull string driven with the pull string external but could easily be internal to the boom.

So there you have it, a dlg fuselage which is light, stiff and costs no more than £20. Gear is easy to instal and I made this one in a day. I would have no reservation in building a full size 1.5m dlg fuselage in this way but taking care with boom selection to minimise launch perturbations. Can you suggest any improvements?

Added September 2013
Alas, some weeks into the testing, the glue joint at the fuselage /wing mount gave way on launch and the model was totalled. The wing mount design needs some modification. I am working on this and will advise when I have a solution.

Ian Middlemiss   Aug 2014   contact@peterboroughmfc.org