Jim and All:
I appreciate and concur with the comments that you made
regarding the challenges for 2M designers.
The Hand Launch Glider community has had this issue for over 10
years. With the development of the Discus Launch by Dick Barker,
a whole new set of design requirements came into play.
However, the 1.5 meter wingspan rule is the same.
For 2 Meters planes, there has been considerable development since
the original 2 Meter World Cup contests of the 70's-80's.
Having considered designing a 2M plane, there is one overriding
comment I must interject here, that is the launch system.
I flew my Flapped Photon DLG in Open Class in Sacramento for
the Spring Fling a couple of years ago. While I used their 6 volt
winch and retriever, I popped off on nearly every launch.
Additionally, I could only get a few hundred feet on the launch.
There were problems.
After a great suggestion by Jim Thomas, I walked the retriever slip
swivel/ring 3/4 of the way down the winch line toward the turn
around. This took about 5 minutes, but since no on else used the
winch, I could do this prior to each flight. All launches after
that used the swivel positon on the line as the focal point of the
winch system, as if it were the turn around.
The basic problems as you can see are 3-fold:
1) The lighter, smaller, 2M meters have to be strong enough to
use the SAME winches and retrievers as the 3.7 meters ships.
2) The same 2 Meters have to haul up ALL the weight of the
winch line. The line is especially heavy considering the big
ships need stronger winch lines and the retrievers need stronger lines
just to return the higher drag lines over the ground.
3) The 2Meters have to be over-designed to take the
stresses.
In effect, you are not designing for aerodynamic performance, rather
you are designing for the winch. Some may say this is the same,
but it is not. Over the years, having been involved with the high
launch/zoom controversies, it really does no matter whether the design
is aerodynamically good, all that matters is that the plane can survive
the zoom and haul up the line and still fly average. Oh how
reminencent of the Old F3B and 2 Meter World cup days. Obviously,
a 2 Meter can be accelerated to a higher speed because of it's size and
weight, this translates to 600-700 ft launches. With a sink rate
of 1.3 ft/sec (which is alot compared to a DLG which is well below 1
ft/sec), a pilot should be able to stay up in normal conditions over 8
minutes, well above most duration contests. You might think this
simplistic, but round numbers appear within the range.
When they provide a winch system that removes the handicap, perhaps
more 2 Meter designers may emerge. Right now, the heavier
composites have to be left to the manufacturers.
This is also reminds me of the woody classes at Visalia, same things
are in effect. So forget the 2 meter, go to the bigger
ships.
When there is just a 2 meter contest of note, akind to the
IHLGF/ECHLGF/Polecat challenge, 2 M development might florish.
Thermals,
Chris Adams
LSF 348 Lvl 5 (#8)
-------- Original Message --------
Subject: [RCSE] Still more two meter thoughts
From: "Jim Deck" <[EMAIL PROTECTED]>
Date: Mon, July 31, 2006 1:22 pm
To: "RCSE" <[email protected]>
OK, so two R/C sailplane designers sit down to create the next world
beater, one a two meter, the other an unlimited. At some point in time, the
unlimited designer can simply say, "I'll increase the span." (Perhaps DP did
this with his "Insanity") while the two meter designer does not have this
luxury. Thus the two meter class sailplane is a challenge at every stage:
design, construction, and flying. These challenges continue, IMHO, to make
two meter a viable class.
Jim Deck
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