Thirty Something (oz15961)

About this Plan

Thirty Something. P30 class rubber duration model. Wingspan 30 in.

Quote: "RALPH SPARROW offers a P.30 rubber powered simple contest or fun fly model incorporating an experiment in dethermaliser systems.

In an attempt to stop crop damage in the growing season, the BMFA Northern Area have a few contests for the smaller type of model. These include CO2, E30, Under 24 in span rubber and P30. Human nature being what it is, we all try to fly the models in the best possible air, with the aim of flying the damn things out of the 'drome.

To counteract this, the Contest Director then tries to limit performance by sometimes putting a one and a half minute max on the qualifying flights and then hope that by fly-off time, the thermals will have gone and the models will all land inside the airfield. This usually works well. However, at Church Fenton in '96 I found that my P30 (a heavy rolled sheet fuselage model which had been built very early on in my conversion training period from RC to freeflight), maxed easily and although the tip-up tail dethermaliser was clearly deployed, the model still kept going upwards and downwind.

So, with the model becoming a dot in the distance, I took a hot walk through glorious thriving wheatfield countryside. But, having lost sight of it and after a long visual search (no Tx beacon), I turned back, resolved that beacons were necessary and there must be better ways of D/T'ing light models or at least improve the rate of descent. The tip-up tail is the most common form of D/T system in use, but there are a few models with tip-up wing, some with a falling nose weight attached to a rear mounted line and someone had, I remembered, tried a wing which hinged at the centre, clapped its hands at the top and surrendered gracefully to gravity!

The latter method sounded a bit difficult, but I thought that I would take a look at various combinations of tip-up wing and tail to see how they behave when falling and if possible, find a faster falling system to try on the next P30.

Putting it to the test: Well, how do you try these things? It isn't easy to compare rates of descent of models in the great outdoors, because every flight is different. So, I thought, models of models to compare a variety of D/T systems using a different model for each system. If the idea worked and if they were small enough, I could drop them side by side in the comfort of my workshop or over the stairwell and see which one hit the ground first... "

Thirty Something, from Aviation Modeller International, May 1998.

Direct submission to Outerzone.

Supplementary file notes

Article pages, thanks to RFJ.

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