THE HISTORY OF V.A.R.M.S The Annual Diary 1990 - 2009

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much of the tail's effects are devoted to pitch, and how much to yaw. In general, a low aspect ratio
wing will need a flatter tail angle (Just as a low aspect ratio wing needs less fin in a conventional
tail), and a high aspect ratio wing will need a steeper tail dihedral.
There are a several different approaches to calculating the required tail dihedral, one based
on constant control authority and the other on constant stability, with small differences between the
angles they predict. I find the constant control authority method is a bit simpler, and also seems to
give more reliable results in my experience (and this just happens to be an area where I do have a
LOT of experience). Just divide the area of the equivalent conventional tail's fin + rudder by the
area of its stab + elevator, then find the arctangent of the result. That angle will be the dihedral of
each side of the V-tail, measured from the horizontal.
If you want the included angle between the V-tail panels, just multiply the dihedral angle by
two, then subtract the result from 180 degrees.
(c) A T-tail requires less area as it is NORMALLY out of the slipstream of the wing ??
Commonly believed, but rarely true, as least for models. In the vast majority of model
applications, the stab of a T-tail has to be the same size as the equivalent conventional tail to have
the same stability and control authority. In a few cases where it is different, it is usually a very
minor difference, and not always in favour of the T-tail.
(d) However - a T might be less forgiving in the stall as it is then in the LEE of (i.e. hidden from)
the airstream as a result of its position in relation to the wing at that angle of attack. This is
often true, for both models and full-scale aircraft. There are a number of fatal accidents on record
of T-tailed aircraft in flight tests that refused to recover from a deep-stall, and carried their crews
into an early grave. However, any type of tail can have funny characteristics resulting from quirks
of the overall aircraft design. All can be vulnerable to blanking by the wing. fuselage, or other
parts of the airframe. Short-coupled and low-aspect ration designs seem to be especially sensitive
to this. If your design has unusual proportions, be prepared to deal with some surprises during
development testing.
(e) Is the relevance of the tail (T, V, Conventional) more, less or irrelevant to the plane having
ailerons ??
No, an airplane can be weird, ungainly and/or cantankerous regardless of what type of tail
it used, whether or not it has ailerons and/or flaps, or what sort of wing planform and arrangement
it uses. That's one of the things that makes airplane design so "interesting: (although on occasion
some other, less printable adjectives might come to mind!). Just remember, every time you change
even the smallest detail anywhere in the design, it's likely to have "ripple effects' throughout the rest
of the design.
August 2000 - Australia and VARMS represented at the 2000 Electric World Championships in San
Diego (U.S.A.) by Bill Hamilton, Manni Riederich and David Hobby - won by Urs Leodolder from
Martin Weberschoeck. Bill and Manni placed 2nd & 3rd in Fun Scale at a prior event, the Electric
Festival flying electric ducted-fan A4 Skyhawks.
October 2000 Aspectivity 327 contained the following item which is an excellent way to include a
NON-radio controlled glider:
The Flyaway Chuckie.....
Ever noticed how flyaway models are choosy where they land and are usually smarter than
their owners? After a number of uneventful flights of about 45 - 50 seconds, a large, high
performance free flight chuck glider built by Geoff Pentland cleared off from Brigg's Field on
Saturday 12th August. It had been very still and seemed a low-risk day. Shortly after being hurled
aloft, the tight circling chuckie hit a weak thermal, and in no time had cleared the two big gum trees
north-west of the clubhouse.
Two surprised VARMS observers called out to its pursuers to chase it north-east. Slowly
drifting away at a considerable height now and still climbing, mild consternation then set in with
Geoff and Jenny (spouse) having to take the car. Traffic now becomes a safety factor. Almost 5
minutes to find a break to exit onto High Street Road! Know the feeling? Meanwhile, one cheeky