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#161
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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 |
#162
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"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 |
#163
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Probably my explanation was not good enough. The airbrake microswitch and
the switch of the pressure transducer are in series. However with no pressure (glider on the ground) the switch of the pressure transducer is closed and opens reluctantly when pressure comes on (glider rolling for take off). So this system gives a warning for airbrakes unlocked (or open) prior to take off; it does not give an alert when flying with normal speed and airbrakes open. See my figure 5 of http://home.wxs.nl/~kpt9/gear.htm Karel, NL "Eric Greenwell" schreef in bericht ... Todd Pattist wrote: "K.P. Termaat" wrote: The solution for a warning on air brakes unlocked prior to take off is quite easy. Use a micro switch on the air brake handle and a pressure transducer from a washing machine in series. I'm confused as to why you need a pressure transducer. Just put a microswitch on the Tost that detects the presence of the towring, and wire that in series with the existing sensor on the airbrakes. The airbrake sensor provides power to both the gear sensor switch and the Tost sensor switch. They both send power to the buzzer. If the brakes are opened with the gear up or the ring inserted, your buzzer goes off. Conversely, if the brakes are open and the ring is inserted for the tow the buzzer sounds. Why wait until you are rolling or in the air to sound the buzzer? Todd Pattist - "WH" Ventus C (Remove DONTSPAMME from address to email reply.) The pressure sensor would be great for a self-launching sailplane. It would also avoid alerting when the pilot had the spoilers open purposely at the start of the launch, as some pilots do to avoid wing drop or running over the towrope. An alert in those situations might not be a bad thing, as it would test the system, and the pilot would be fully aware that he was causing it. -- ----- change "netto" to "net" to email me directly Eric Greenwell Washington State USA |
#164
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Eric Greenwell wrote:
Jon Meyer wrote: I'm saying it must be smaller to be cheaper. Bigger costs money. Here was an important goal: "substantially lower costs than then-current new gliders". It's the first one on the list in the history section of the World Class Soaring Association (www.wcsa.org/history.htm). A big part of this was to achieve "cheap". Fixed undercarriage, no waterballast, even the requirement for no flaps, are in my opinion all unnecessary requirements for a world class glider, If you want cheap, you have to leave off the things that make it costly. Having seen three used PW-5's/Russias in the past year for half the price of an LS-4, cost is an issue... I'd also have to classify myself not as a soaring performance enthusiast, but as a soaring consumer. Sort of like I'd have a boombox instead of a six-speaker Bose, a 32" TV instead of HDTV, etc. As a soaring consumer, I fit what Carl Herold has profiled: doing X-C in 1-2 years in the sport, having soaring as a hobby, etc. As a consumer, I'm thrilled about the NON-performance aspects of soaring that the PW-5, Russia, and Sparrowhawk provide. Namely, lower cost, lighter weight, simpler features, modern technology (which does not necessarily mean better performance). Having lighter wings to assemble, a smaller trailer, shorter wings, no flaps/gear/water ballast certainly are not things that help performance, they only appeal to me as a consumer/hobbyist. I can completely understand why the soaring enthusiasts would be baffled at anyone who wants a new glider which performs worse than the top 50% of gliders in the world. From their perspective, which is perfectly understandable, this is absurd. But if you eliminate the word "performance," every single aspect now goes the other way. This is what I as a soaring "consumer" look for in value. Model aircraft builders have a similar quandry. The motor airplane builders enjoy much more performance, but the electric models are much easier to start, cleaner, and less expensive. Electric model aircraft are gaining a lot of popularity with "consumers." I don't expect a Yugo to be appreciated by Ferrari drivers... But you can drive a Yugo by the Ferrari shop AND the gas station every day... I don't think the World Class will ever draw pilots out of their retract gliders in any numbers. The fixed gear and low cost (read short wings) simply can never challenge span and reduced drag. The World Class is a consumer class, and I don't expect the enthusiasts to accept reduced performance... On another note, I would like to see the World Class develop in 2009. One change perhaps is the "homebuild" option. This may have discouraged some entries, and I'm not sure added any benefit (another poster said this too). I would also like to see a 36:1 or better glide as a minimum. I think the Sparrowhawk Russia, Apis and Silent all have the potential to compete with only minor modifications (different wings, changes to eliminate flaps, different landing gear designs, etc.). And a lot of improvement can happen given five years... Will any of this now attract soaring "enthusiasts" to trade in their LS-4s? I don't think so. But hey, I'm comfortable with that... -- ------------+ Mark Boyd Avenal, California, USA |
#165
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Dave Martin wrote:
We now seem to be advocating warnings and buzzers for every eventuality. This is a list of the sounds a pilot is expected to cope with if everyones idea are translated into reality, it may not be complete.......... Under carriage Flaps Stall alert (2 one for each wing tip) Tail dolly Low battery Canopy Main Pin G Meter Spoiler alert Aircraft Proximity alarm (only good if everyone has one fitted) Tyre pressure alert Brake pad wear alert Add to this one essential noise Vario And a few helpful ones Radio GPS alerts Turn point alerts Approaching airspace alerts on nav aides Nope. I'm only interested in the buzzer that warns against the problem that caused 50% of the glider fatalities in the last 10 years. Only one line on your list does that... You can keep the rest... true to form I've not even had an audio Vario in the past year -- ------------+ Mark Boyd Avenal, California, USA |
#166
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In article ,
Ben Flewett wrote: We have a problem in that we have committed to the PW5 until 2009 but perhaps there is something that can be done here - some suggestions have already been made as a result of this discussion. Now THAT is a completely true statement. I must say I'm remarkably pleased there was as much discussion as I've seen. This can ONLY improve the participation and decision in 2009. And that isn't too far off, so get your opinions to the IGC soon, and start designing and building your World Class entry... -- ------------+ Mark Boyd Avenal, California, USA |
#167
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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, Actually, I did this last year. I took an old radio control transmitter, mounted it in a small box, and put one control potentiometer on a thumb wheel mounted to a hand grip. In the winch, I have the receiver with a servo mounted to the window in front of me. The servo has a long orange stick attached. If the pilot wants to go faster, he thumbs forward, which moves the servo and flag up. If slower, then down. If good, then horizontal. Haven't tried it yet, but it was a fun project! Jim Vincent CFIG N483SZ illspam |
#168
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#169
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The stall 'horn' in the Katana DA20-C1 is nothing more
than a hole in the leading edge that at the right angle 'whistles'. Quite effective I might add too! Ready to get the drill out for your leading edges;') Or use the string AOA idea. I'd like to see this work. I'm not so keen on having something else the pilot has to LOOK at (vs. hearing). But who knows, and it's a fun experiment... -- ------------+ Mark Boyd Avenal, California, USA |
#170
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Owain Walters wrote in message ...
Which brings us kind of full circle. The argument is not against the World Class just against the requirements and in turn against the PW5. Or in other words, against the original concepts of the class. Even though you have no interest in flying it, or letting those that do fly it do so without a lot of unneeded derision. As a former 1-26 owner, why am I not surprised? Soaring is going to die a well deserved death, killed from within, not from outside influence. |
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