Build Log: Lightweight DLG for Thermalling and Discus Launching
Build Log: Lightweight DLG for Thermalling and Discus Launching
I started this build with a clear aim: a very light discus launched glider that thermals well and is forgiving in small lift, while keeping the airframe stiff enough to hold a clean wing section in climb and launch phases.
My material choices were governed by weight limits and stiffness requirements, so I used a thin foam core with a light glass skin on the wing and a carbon spar sized to give torsional rigidity without excess mass.
The basic build steps followed a familiar sequence and are worth listing for anyone attempting the same trade-offs between lightness and stiffness.
Cut and sand the foam cores accurately to maintain the intended aerofoil and reduce the need for heavy fairing.
Pre-shape and glue in the carbon spar with minimal epoxy to keep the bond strong while avoiding weight creep.
Apply a single layer of lightweight glass cloth over the wing and use vacuum or careful roll-out to eliminate excess resin.
Build a minimal but rigid fuselage pod, installing lightweight servos and a compact receiver to centralise mass.
Balance the completed airframe with small lead strips in the nose as required to reach the intended centre of gravity for thermalling performance.
Tuning for thermalling requires attention to wing stiffness and twist because a floppy wing loses efficiency in weak lift and can induce flutter during launch, so I stiffened the outer panels slightly and set a little washout to keep the tips calm in turns.
Practising discus launch technique was the final part of the log, and it made the biggest difference to climb height and entry into thermals; hold the glider at the tip, rotate smoothly through the hip, and release with the wing high to transfer rotational energy without jerking the model.
During the first few flights I made small trim changes, reducing up-elevator slightly after a big DLG launch to prevent ballooning and adjusting aileron differential to keep the wing from snapping in tight climbs, and you can find notes and parts I used on my site at WatDaFeck.
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