SLOPING OFF...
...the Newsletter of Christchurch and District Model Flying Club for...June 2024
MATTER HAS MASS - DOES IT MATTER?
Here’s my part complete 64” span DH91 Albatross (what a labour-intensive process strining the fuselage was!) and in this form, with all the hardware installed including the retracts but minus props and spinners, covering and nacelles, it weighs 1lb 10oz, so with a 2s2200 and fully RTF I hope to get it under 2lb 10oz, or less than 14oz/sq ft. The only other model plan I can find comes from that master of design, Laddie Mikulasco. His was much the same size as mine, powered by four Speed 400s and weighed 5lbs ready to fly. It must have been quick!
Now here is the XFly DHC Twin Otter featured in this month’s RCM&E. According to the Datafile with the article, span is nearly 6ft, large for a foamie, and its flying weight is 8lbs 13oz. It needs a 6s 5000 - 6000 battery.
Compare this with a balsa home-built from the Ivan Pettigrew plan and flown by BIMBO Scott Wallis, which is about the same size and at 3lbs 8os weighs much less than half the X-Fly version. Power? a 3s 2200. The foamie on floats costs £500, thebuilt-up version...Scott was a student when he built it, so lets say £200. Ivan does a larger version at 84” span which weighed 6lbs with nine NiCads.
I do believe in building light because it has many advantages (and some disadvantages, of course)
In the right conditions - wind less than 10-12 kts - light models fly at a much more realistic scale speed: they don’t need much grass to take off, land much more slowly and at these speeds are far less likely to tip stall on approach or in base leg turns.
If they do have an arrival the structure is more likely to survive or be repairable because they have lower inertia.
The flight batteries can be lower voltage, motors can be smaller, servos less powerful and hardware overall lighter and cheaper than a heavier alternative.
Disadvantages:
In stronger winds a heavier model will look more realistic in flight because it won’t be thrown around so much.
It can have much more scale detail - compare the Ivan model to the X-Fly version.