Thermal right, land left

Speaking of simple warning devices:
How about a simple hookup to a horn which is activated when the
airbrakes are opened while the towhook is engaged (i.e. open spoilers
during tow)?
A microswitch on the airbrake levers would be the no-brainer part.
What about the towhook? Magnetic sensor? where? How? Other ideas?
Uri

(Mark James Boyd) wrote in message news:4054b43e$1@darkstar...
Robertmudd1u wrote:

Some may think this a cheap shot, but what the heck.

Believe it or not some pilots fly gliders with fixed gear. They even fly them
X-C and make land outs. They even stall/spin them.

Too many people in this sport think you need ALL the bells and whistles and a
$100,000+ glider to be a "real" glider pilot. That attitude is hurting us.

Robert Mudd

I certainly would not use the word "need" with respect to a
glider AOA indicator.

And yes, cheap and simple is important. Perhaps the cheapest idea
is simply the ol' harmonica style Cezzna AOA indicators, one
mounted on each wingtip of a 1-26 (easier to install on a metal wing,
and the 1-26 is a glider with more than it's share of stalls
leading to fatalities).

Then, if added complexity is warranted, a small switch on the
spoilers which deactivates the audio vario when the spoilers are out,
so one can now just barely hear the stall horns.

Ideally, it would be nice to have removable wingtips, so
one could experiment without modifying a whole wing...

Perhaps there are other types that would have this feature
to allow inexpensive experimentation. Then maybe try the electric
AOA tabs too...

Speaking of simple warning devices:
How about a simple hookup to a horn which is activated when the
airbrakes are opened while the towhook is engaged

David Noyes had such a system on his Ventus CM. There was a micro switch
mounted so that the trigger blade was moved by the oval Tost ring as it was
inserted into the tow hook.

Robert Mudd

Uri Saovray wrote:
Speaking of simple warning devices:
How about a simple hookup to a horn which is activated when the
airbrakes are opened while the towhook is engaged (i.e. open spoilers
during tow)?
A microswitch on the airbrake levers would be the no-brainer part.
What about the towhook? Magnetic sensor? where? How? Other ideas?
Uri

This would be an easy addition to the typical gear warning system, with
the new switch simply over-riding the gear switch. Fixed gear gliders
would need to add a spoiler switch and warning buzzer.

Pilots concerned about warning proliferation could consider using a
voice chip to speak "Spoilers" and "Gear" for the two alerts, instead of
a buzzer. Voice chips are cheap and simple to use these days.
--
-----
change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA

So if we agree this is a good idea, my main question is the design of
the tow sensor:
1) It must be robust
2) It must not interfere with the hook mechanism (open spoilers AND
can't release???)
3) If it is magnetic - will it interfere with the compass? Does
anybody care?
4) A Large magnet at the end of the tow rope - will it survive the
fall to the ground (either on winch or from the tug
Ideas?

Uri
Eric Greenwell wrote in message ...
Uri Saovray wrote:
Speaking of simple warning devices:
How about a simple hookup to a horn which is activated when the
airbrakes are opened while the towhook is engaged (i.e. open spoilers
during tow)?
A microswitch on the airbrake levers would be the no-brainer part.
What about the towhook? Magnetic sensor? where? How? Other ideas?
Uri

This would be an easy addition to the typical gear warning system, with
the new switch simply over-riding the gear switch. Fixed gear gliders
would need to add a spoiler switch and warning buzzer.

Pilots concerned about warning proliferation could consider using a
voice chip to speak "Spoilers" and "Gear" for the two alerts, instead of
a buzzer. Voice chips are cheap and simple to use these days.

What about the towhook? Magnetic sensor? where? How? Other ideas

Install a strain gauge internal to the fuselage right up against the hook
mount. Get Peter Masak to design a simple circuit that trips an electronic
relay when the strain exceeds a certain amount. Knowing Peter, it should take
him less than an hour.

Jim Vincent
CFIG
N483SZ
illspam

"Jim Vincent" wrote in message
...
What about the towhook? Magnetic sensor? where? How? Other ideas

Install a strain gauge internal to the fuselage right up against the hook
mount. Get Peter Masak to design a simple circuit that trips an
electronic
relay when the strain exceeds a certain amount. Knowing Peter, it should
take
him less than an hour.

Jim, if you go that route, build the strain gauge to display the hook
tension to the pilot for the purposes of flying a winch launch.

Bill Daniels

Jim, if you go that route, build the strain gauge to display the hook
tension to the pilot for the purposes of flying a winch launch.


Good thought Bill, but I think it require at least two strain gauges to
implement this. Since the direction of the load changes during the course of
the winch launch, the load could not be measured by just one strain gauge. Two
are needed to provide the raw data to the instrument. Then, you need to do a
complete calibration of the system to determine the load ratios for various
angles and tensions since these are not readily calculatable. Then you need to
program a CPU accordingly.

Just a simple load / no load determination is far easier.

IMHO, regarding tension values during a winch launch, I've driven hundreds of
winch launches and believe the only value of a tension meter is to tell you if
you're approaching the breaking force of the cable/rope. The feedback from
engine noise, spool speed, glider pitch attitude, etc are far more valuable to
me when winching.

Jim Vincent
CFIG
N483SZ
illspam

"Jim Vincent" wrote in message
...
Jim, if you go that route, build the strain gauge to display the hook
tension to the pilot for the purposes of flying a winch launch.


Good thought Bill, but I think it require at least two strain gauges to
implement this. Since the direction of the load changes during the course
of
the winch launch, the load could not be measured by just one strain gauge.
Two
are needed to provide the raw data to the instrument. Then, you need to
do a
complete calibration of the system to determine the load ratios for
various
angles and tensions since these are not readily calculatable. Then you
need to
program a CPU accordingly.

Just a simple load / no load determination is far easier.

IMHO, regarding tension values during a winch launch, I've driven hundreds
of
winch launches and believe the only value of a tension meter is to tell
you if
you're approaching the breaking force of the cable/rope. The feedback
from
engine noise, spool speed, glider pitch attitude, etc are far more
valuable to
me when winching.

Jim Vincent
CFIG
N483SZ
illspam

I was thinking that the winch driver would see the glider airspeed via
telemetry and thus control it precisely and the pilot would control the
tension with a panel mounted meter. That way the pilot gets the right
airspeed and precisely loads the glider and cable to whatever value he feels
comfortable with up to the breaking strength of the weak link.

Bill Daniels

Install a strain gauge internal to the fuselage right up against the hook
mount. Get Peter Masak to design a simple circuit that trips an electronic
relay when the strain exceeds a certain amount. Knowing Peter, it should take
him less than an hour.

Jim Vincent

I've been thinking about how to measure strain on the
rope during auto-tow, but this time from the auto side, not the
glider side.

I'm planning to tow using a 50# spring scale, and never exceed
40#, and see how long (far) it takes to accelerate to rotation
speed. For 500#, I seem to get calculations near to 1000ft or so.
I'd like to see if a 40# thrust AMT turbine would accelerate
a 500# glider to rotation in a reasonable runway length
(say 2000 ft or less).

As a second issue, I'm wondering if anyone has measurements of
the typical strain on a winch or auto tow rope. I'm
guessing .5 to .9 times the glider weight (probably near the
highest altitude right before release, right?).

Spring-type weight measuring devices for up to around hundreds of
pounds are in the $200 range. In the 500#+ range, though, things
get pricey...



--

------------+
Mark Boyd
Avenal, California, USA

"Mark James Boyd" wrote in message
news:4057718f$1@darkstar...
Install a strain gauge internal to the fuselage right up against the hook
mount. Get Peter Masak to design a simple circuit that trips an
electronic
relay when the strain exceeds a certain amount. Knowing Peter, it should
take
him less than an hour.

Jim Vincent

I've been thinking about how to measure strain on the
rope during auto-tow, but this time from the auto side, not the
glider side.

I'm planning to tow using a 50# spring scale, and never exceed
40#, and see how long (far) it takes to accelerate to rotation
speed. For 500#, I seem to get calculations near to 1000ft or so.
I'd like to see if a 40# thrust AMT turbine would accelerate
a 500# glider to rotation in a reasonable runway length
(say 2000 ft or less).

As a second issue, I'm wondering if anyone has measurements of
the typical strain on a winch or auto tow rope. I'm
guessing .5 to .9 times the glider weight (probably near the
highest altitude right before release, right?).

Spring-type weight measuring devices for up to around hundreds of
pounds are in the $200 range. In the 500#+ range, though, things
get pricey...



--

------------+
Mark Boyd
Avenal, California, USA

Much cheaper is a old-style (no vacuum assist) automobile master cylinder
and a hydraulic pressure gauge - or various junkyard parts to that effect.
Rent a 2000 pound scale to calibrate it.

Best launch winch or auto is a line tension of 1.0 x takeoff weight for the
whole launch. (Assumes the winch/tow-car driver and pilot know what they
are doing.)

Bill Daniels

Bill Daniels