"Tim Ward" wrote in message
...

"Bill Daniels" bildan@comcast-dot-net wrote in message
. ..
snippage
Let me throw in a slightly controversial idea.

Low L/D, taken in isolation, offers no benefit whatsoever in a trainer.
In
fact, higher L/D is a safety feature that gets an inexperienced pilot
back
to the runway after a bad judgement call. In spite of this, there is an
instinctive reaction among most glider pilots to inversely relate L/D and
safe handling qualities.

In a soaring environment, I think you're right. But that is not the
environment veeduber is proposing.

He's proposing a cheap "hook" to capture the attention of teenagers.
Teenagers who might not have two grand or so to shell out for glider
lessons, but might well have some sweat equity to invest in building
something that actually flies.

For this target group, it has to be something that goes together pretty
quickly. If it takes a thousand hours of construction, it isn't likely
to
get started, let alone completed.

For veeduber's purposes, I think he will have achieved part of his goal if
it gets even half built. Kids will be using their heads and their hands
to
solve problems.

For this environment, it's not performance that counts, but energy. With
a
fairly draggy airframe, you can limit the amount of energy available to
damage the pilot.

Somewhere on Mike Sandlin's site, he remarks on this, limiting the energy
by
how far up the training hill you drag the glider.

snippage

"Primary gliders" were an expedient developed in an environment that
lacked
adequate two-seat trainers. They were abandoned with great relief as
soon
as usable 2-seater trainers became available. Today, there are a great
number of excellent 2-seat trainers and qualified instructors. Only a
fool
would try to learn flying in a "Primary".

I can't entirely disagree, but people learn to fly hang gliders, with
similar performance limitations, every day.
There is some tandem instruction available, and that's good. But in
general, it's not the instruction process that kills people.
A two-place primary under 155 lbs might sneak in under USHGPA's tandem
exemption, here in the U.S. Maybe.


Tim Ward



OK, but don't build one, buy one. There are a few around. Take it out to a
hill or dry lake and try flying it. This is also done on occasion. What
you won't do is fly it two days in a row. One day will convince just about
anybody that primaries are a really bad idea.

Primary gliders are a huge amount of work to fly - expecially if you use the
traditional bungee launch method which is really the only safe way to fly
one. Aero tow or winch launch is terrfying in a primary - although this is
also done on occasion. (But rarely twice in a lifetime by the same pilot.)

To fly one as it was intended, you need a huge grassy slope that is slightly
shallower than the glide ratio of the primary. The bungee launch will get
the glider to just above stall speed a couple of feet above the ground. If
the pilot can hold the exact best L/D airspeed and keep it perfectly
coordinated, he will be rewarded with a glide of a couple of hundred yards -
maybe 30 seconds of airtime. If he deviates in any way from perfection, the
glider will quickly settle into the grass. If you have 15 - 20 knots of
wind up the slope, the instructor can run along side shouting instructions.
Then everybody gets to haul it back up the slope. All this exercise will
achieve about ten flights a day but it WILL get you in shape.
See: http://www.youtube.com/watch?v=B6-EeuEi-KY
See: http://www.youtube.com/watch?v=BgBJ52L-Rao

I have a better idea that fits well with the homebuilder ethic. Build a
winch.
See: http://groups.yahoo.com/group/winchengineer/files/

The really big cost in learning to fly gliders is aero tow. It averages
about $50 for a 15 minute flight. Add instructor and glider rental and it's
not unusual to see $250 and hour. Multi-engine training is cheaper.
Winches can reduce launch costs to $5 and glider training rates to ~$50/hr.
Certified glider trainers aren't expensive if you can keep the utilization
high.

And I GUARANTEE it attracts young people. You can't buy a ride like that at
Disneyland.
See: http://www.youtube.com/watch?v=UOp_EsplxDM

Bill Daniels