From: stefan@helios.physics.utoronto.ca (Stefan Mochnacki)
Subject: Re: Dynaflight Bird of Time (and Spirit of 76)
Organization: University of Toronto Physics/Astronomy/CITA
Date: Fri, 16 Oct 1992 18:21:20 GMT


Stan Husch asks:

>   I've been thinking about getting the Dynaflight Bird of Time for
> my next project. Has anyone built and flown this kit?

I haven't (I had a Paragon instead), but I saw LOTS of these when
I was flying out of Pasadena a dozen years ago or more. One flyer got
to the US FB3 team with it, I think it  won the trials
and maybe even the Nats (it's a long time ago). But that was just
as the Kevlar weapons from Austria and Canada arrived on the scene.
The BOT I observed most closely (by competing against it) was flown
by Keith Kindrick (sp?), who I think later became a national
champion. There were BOT's several in my club (the Rose Bowl Flyers).
It sort came out of the California floater school of
thought, but not as extreme as the Mirage.
  
> For those of you that don't know what this plane looks like here
> it is:  118" Span, rudder, elevator, 1070 sq in. 5-6 oz. wing loading.

That's VERY light!

> The wing planform is most unusual in that the root chord is smaller
> than the chord at mid wing. From mid wing to the tip it tapers to an
> elliptical tip. 

And THAT in my view is its glaring weakness. The ones I flew against
had a quite vicious tip stall when on the tow, either histart
or winch. This would cause sudden veering, dangerous if occurring
at low altitude. Didn't seem to worry their owners too much, though.

>   I would also like to modify this planform with the addition of
> spoilers or preferably flaps. Has anyone tried this?

Why not? However, it was designed as a lightweight ship, so adding
paraphernalia adds weight and defeats the minimalist approach.
The best flyers I remember did not use anything other than rudder
and elevator.


Bill Gingras adds:

> I saw someone else fly a mini once, and it fluttered quite severely when
> he tried to winch it up.  

That may be due more to insufficiently tight Monokote, but could
also be caused by the narrow tips I mentioned above.

> One more thing, when I was first getting into gliders, I asked a "pro"
> (my instructor) what he thought of the B.O.T.  He said it's a neat
> looking plane, but it uses "old technology" (airfoil, I guess), and the
> wing is a bitch to build.

I'd agree, since the design goes back to about 1978 or earlier. It 
certainly is pretty, borrowing from those pre-WWII German and British 
gliders, and with the exception of towing it flies pretty
well. (Elliptical tips went out of fashion in contest gliders back
in the late '60's). I guess that if you are aware of its possible
bad behaviour, you could do well with it. It certainly is much less of
a truck than a Paragon, but don't forget that modern gliders have
MUCH stronger wings (the zoom launch was invented in 1980 or so
by the crazy Canadians in Victoria, B.C.; they terrorized the
1981 Worlds in California so badly that the rules were changed
as a result... but the zoom launch seems to have remained). So
unless you beef up the original wings, forget about zooming up 
at great speed; this is a pre-Kevlar bird.

An aside: Ron asks:

> I anybody know anything about the Spirit of 76 Sail Plane?  This plane is
> suppose to be all foam and retailing for $19.00 (Hobby Shack).

> Can this plane really fly?  

Where do these old turkeys keep coming from ? Must be an unsold
garage-full of them somewhere ... The ones I've seen could not be 
described as flying. The name says it: they were mass-produced in 1976.
They are indeed all foam. Throw-away airplanes. But I'm sure
some ingenious soul knows how to make a purse out of a sow's ear ...

					- Stefan Mochnacki
					(somewhat lapsed flyer ..)

-- 
Stefan W. Mochnacki          INTERNET - stefan@centaur.astro.utoronto.ca
Astronomy, U. of Toronto     UUCP - {uunet,pyramid}!utai!helios.physics!stefan
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