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Old Aug 25, 2012, 01:00 AM
Trex 700, Gaui X5, 450DFC
SoarWest's Avatar
United States, AZ, Queen Creek
Joined Apr 2010
326 Posts
FYI my Specter is ready to fly. I was able to completely build, trim and program this glider up in just 2 evenings. A very quick build!

I'll see how the weather is tomorrow and see if I can get some flights on. My build is right about 795-800 grams (counting the 1600 mAh battery). The scale doesn't quite stop moving but it's right there.

I had to put a 1600mAh battery up front to get the balance to be 67-68mm from the leading wing edge. That seems like a safe place to start. If I put in the 1300mAh battery it's 70+mm from the leading edge and that might be good to try in a few flights. I'll put back the 10x6 prop and start with that. I have everything programmed in now, with a little aileron differential as the plans show and the throws all set as called for. +/- 10mm for the elevator, and +12/-8 for the ailerons.

Now if I can just get some sleep haha.
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Old Aug 25, 2012, 05:28 AM
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StarHopper44's Avatar
United States, NC, Richlands
Joined Jun 2011
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Quote:
Originally Posted by peterlngh View Post
Some guy no one had ever seen showed up at the field with a Graupner glider (I can't recall the name) and went off away from the crowd. Before anyone had a chance to even approach him he gave it a mighty heave, stalled, and broke the fuse behind the wing. He tossed the whole thing in the trash can and drove away, never to return. One of my buddies got a fantastic glider for the price of a little glass tape and epoxy and the Airtronics radio went into a series of club trainers.
Prolly one of those guys with absolutely no experience or training who got lured in by the ad's "beginners-to-intermediates" ratings.

What's more surprising to me was how he ever got off the ground to start with. We've got plenty of signage out at our club about Members & Guests ONLY, & 'MUST BE AMA' yada yada. How'd he even get time to prep the plane to fly?? Nobody carries assembled gliders in a car - unless maybe he pulled up in a semi!


& SoarWest...
Good luck on the maiden -- lookin' forward to some great video! *hint hint*
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Old Aug 25, 2012, 12:26 PM
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I'm looking forward to the report, SW. It sounds like the Specter is, indeed, a little heavier than the Passer-X. I would love to compare the two side by side to see if I can figure out the difference. I do know that I was surprised by the overall thickness of the fuse. Perhaps they use a little extra glass? It wouldn't take much to account for the difference.

One last hint. I found the elevator to be a little over sensitive at the recommended throw. Some expo, say 20-30%, would be a good idea. And don't be afraid to give it a pretty good heave with a little nose up for the first launch. Good luck and have fun!
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Old Aug 25, 2012, 12:39 PM
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What's more surprising to me was how he ever got off the ground to start with.
This was an informal flying spot, just a piece of mowed grass along the side of a corn field in the middle of nowhere, where everything is pretty much on the honor system except for a frequency board. There were only a few guys there and they were engrossed in flying and such and figured that he would make his introductions before attempting a launch. He just slid his wings on, no ailerons back in those days, and broke his plane before anyone could really react. We speculated that he had been chased off the closest club field which doesn't allow gliders of any kind to this day.
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Old Aug 25, 2012, 12:45 PM
Trex 700, Gaui X5, 450DFC
SoarWest's Avatar
United States, AZ, Queen Creek
Joined Apr 2010
326 Posts
It's really a sad story, I hate to see anyone have a bad RC experience. Especially years ago when it took a month or more to really build up a glider before you got to fly. Having personally spent those months building, I loved and enjoyed it all but have to say that my flying skills are much better now that I spend more time flying and less time building!

Maiden report on it's way, Word hung as I was writing it and now the better half needs me for a bit... sorry.
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Old Aug 25, 2012, 01:17 PM
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Quote:
It's really a sad story, I hate to see anyone have a bad RC experience.
I couldn't agree more. If he had just been a little more patient, or perhaps less shy, he might have ended up with a lifetime hobby. We always figured that he had purchased the glider already built. It was very well done and nicely covered. I wish I could remember what it was called. I'm almost certain it was a Graupner. 100" wing with polyhedral, glass fuse, and a V-tail long before electronic mixing. It looked very much like a slightly reduced Grand Esprit. It also had spoilers built in but the guy who ended up with it had to recover part of the wing to install the cords. It was a little heavier than the Aquila I was flying at the time but what it gave up in pure floating ability it made up in speedy flight while searching for the next thermal. I lost track of the owner after I moved some years ago but he was still flying it.
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Old Aug 25, 2012, 03:13 PM
Trex 700, Gaui X5, 450DFC
SoarWest's Avatar
United States, AZ, Queen Creek
Joined Apr 2010
326 Posts
Specter Maiden flight report.

The good news is that my glider remains unharmed after a couple of flights! Yipee.

I started in a soccer field with about half throttle and gave a decent toss. It was banking left just a touch so I corrected with stick and started to trim things up, adding power to climb and get away from obstacles so I could really trim things out.

I had to add some right trim, I don’t think I got my tail feathers perfectly aligned but it’s not much of a problem. It should still perform well but a Jig would have been better to assure perfect alignment. I also had to add a bunch of up clicks, if wanted to fly fast as I had it setup.

I couldn’t really get a good feel of the soaring potential because I need to add braking to the ESC. Anytime I would turn off the motor to glide I could see it was still spinning and hear it as I would fly by. I believe this was adding much unnecessary drag and effected the soaring.

I felt my initial trim and feel was pretty close. I might add a little weight and fly with the CG around 66 from Leading Edge to see if it feels more stable. I couldn’t get the ship to really slow down and glide but again I believe it was due to the prop spinning.

Under full power I could go nearly vertical, at least 60 degrees. No problem with the climbs, other than holding so much down elevator to keep it from looping or possibly stalling in a hammerhead type stall.

My first flight was 1 minute of run time and a 5 minute flight. My second flight was 2 minutes of run time and a 10 minute flight. My battery was at 51% when landing with 15 minutes of airtime. I think the prop spinning was increasing the loading? Unsure and will need to test once I have the brake set.

Things to do:
Add down elevator compensation to Throttle mix. I don’t like the nose pulling up quite as much as it does.

Double check to make sure I have my aileron differential correct. Is it less up throw or down throw? The docs say less on the down but I want to check.

Setup the ESC for a soft brake, to make sure the prop stops spinning! Check engine temps and run times after doing this.

It's up over 100f here today already so I might not get another flight in until late and that's when the winds pick up so we'll see!

I downloaded the altitude log from the flight just to see how it went. I flew up to just over 400ft AGL on power, and my climb rate was about 800-840 fpm vertical. For glide I was seeing about 300 fpm descending but as I mentioned that is likely very poor due to the motor not stopping. I won't upload the image from this flight as I'm sure it's such a poor example, I'll wait until I have it setup properly.
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Old Aug 25, 2012, 03:45 PM
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Huzza for SW! The prop brake is the big one. I sometimes use just enough throttle to kick the blades out as an air brake. It will not soar with a windmilling prop. Period.

I needed a bit of up from my original setup, I very nearly tossed a lawn dart on my very first test glide, but, as I've played around with the CG and trim, I use less with the CG moved back a bit. Moving the CG back also made the pitch up with power easier to control. It can also be controlled by easing off the throttle a tiny bit. I actually kinda like it to point towards the sky under throttle and have not found it difficult to control. My guess is that, with a few more flights, you will find yourself just correcting automatically. As I have it trimmed right now it will glide fairly fast and a little nose down hands off. The maximum L/D is fairly fast with this airfoil. I then just pull a little back stick when I'm actually in lift to slow it down. It has a much wider speed range and better slow flying characteristics than my foam ASW-28.

CG and trim are very subjective and personal among pilots. Plus, minor variations in airframes can dictate different settings. It sounds like you're close and should have it dialed in fairly soon. I have also found that getting the rudder trim right cuts way back on the amount of aileron trim needed. I usually set rudder trim by trimming for a straight vertical climb whether it's with a powered glider or a powered stunter.

Re: Aileron differential. Yes, you want a little more up travel than down but one doesn't need much. I set mine up by just rotating the servo arms forward one tooth on the servo arm. I prefer the differential set up at the linkage, instead of the programming, because I want it no matter how I change the throws and trim. Plus, my transmitter won't allow differential programming when using the flaperon mix. I think the picture is pretty obvious.

Have fun! I am off for the weekend's debauchery but I'll be pulling for you.
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Old Aug 25, 2012, 10:03 PM
Trex 700, Gaui X5, 450DFC
SoarWest's Avatar
United States, AZ, Queen Creek
Joined Apr 2010
326 Posts
I got in a sunset flight to check how it would be different w/ESC brake set. It soars much better, I was able to take out much of the up elevator I had to add in. Really the only problem now is landing! I fly out of a smaller field surrounded by trees, so I have to come in barely clearning and it barely sets down by the other end! I'm going to have to add spoilerons to get it to drop into this field, and there aren't many other options with grass around here (Phoeniz area).

In flight it's nearly neutrally balanced, if I point the nose down it goes faster, doesn't really balloon up which I would like a little of so it flies more hands off higher up where it's harder to see! I might stick a 2200mAh battery in there to increase the nose weight. That would also give me nearly an hour of flight time!

This time I was able to balance the power better on climb, I tried adding a programmed down elevator to power mix but added to much down so I turned it off. I'll adjust that for next time ;-)

Got in about 20 minutes of flying with my 1600 mAh battery at 56%, I used 2:30 engine time.
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Old Aug 25, 2012, 11:01 PM
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Cool!

I have a little positive stability in a dive test. The faster I go the more it wants to pitch up whether I'm in a power off dive or a power on climb. I think you will be amazed at how moving the CG just a couple millimeters at a time can change the trim and performance at the edges of the flight envelope.

I consider spoilerons to be essential. I used every bit of throw available on my servo and aileron horns so that I get enough spoiler travel. I could only get more if I carved a notch in my wing to clear the pushrod. I just use the transmitter to turn down the aileron throw. I have a little down elevator mixed in because it pitches up when they pop up but, again, it's manageable. Once the zoom is over, or one just corrects until the speed bleeds off, one can pull the nose up and land it like a parachute if there's any wind at all. Diving with the ailerons up builds up airspeed in a hurry but it bleeds off just as fast when you pull the nose up. I do also use the prop as an additional airbrake as well. Just trying to dive it at a small field is, shall we say, counter productive? If it has any momentum at all when it gets into ground effect it will go a surprisingly long distance but some combination of spoilerons and windmilling does the trick.

G'night!
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Old Aug 26, 2012, 06:24 AM
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StarHopper44's Avatar
United States, NC, Richlands
Joined Jun 2011
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Have you guys ever tried a sideslip landing? Apparently not from the sound of your efforts there. Can be effective in bleeding off speed for "short notice" landings.
Me either, yet, btw, but it's something I fully intend to learn as soon as I get the chance to work on it.

There was an incident that got kinda famous in aviation circles where, thru an almost freakily connected chain of freaky events, system failures & even metric vs imperial misuse, a commercial airliner ran out of fuel mid-flight in the Great White North, with no jetport facilities within reach. Happy ending tho, basically because the pilot just happened to be an experienced glider pilot! I can't remember the name of 'The Incident' so's you can read about it (someone maybe does & can help??) but in the meanwhile I'll try to find & post it. Despite gettin' kinda complex in all the things that happened - each 'neccessary' to reach the end it did - it's an interesting read. One thing it did tho is show me the value of learning that kinda handling - even without a shipload of passengers' lives to save! And honestly, I've already encountered a couple of situations where I could'a used it!
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Old Aug 26, 2012, 06:38 AM
Earthbound Skyhound
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Well hark! - that didn't take long! Just googled "glider pilot airlines sideslip landing incident" and one of the first hits took me to Wiki's 'Slip (aerodynamic)' entry, which seemed familiar, so checked, & BINGO!

Darn convenient in that it not only well describes the technique, it also addresses the very need you guys are faced with, to wit:
"...excess speed can cause the aircraft to fly in ground effect for an extended period, perhaps running out of runway. In a slip much more drag is created, allowing the pilot to dissipate altitude without increasing airspeed, increasing the angle of descent (glide slope). "


AND it references the very incident I indicated. As you're reading, note the 'link phrase' down the page a ways: "Gimli Glider" under 'Notable employment of the slip' -- told'ja it got some ink! Click & read, dear brothers, click & read!!

Happy sailing!
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Old Aug 26, 2012, 11:12 AM
Trex 700, Gaui X5, 450DFC
SoarWest's Avatar
United States, AZ, Queen Creek
Joined Apr 2010
326 Posts
It just so happens that I'm a full size glider pilot too with several hundred hours and yes I commonly slip in a real glider... just not sure I could manage it in a model, as I know the feel and how it shakes and tells me what's going on. Without the immediate feedback it would be very interesting to do. I'll have to try that. I wonder if the rudder on the Specter is larger enough as you primarily cross control the rudder and ailerons to force the slip. Pushing the nose down is key to maintaining a safe speed, it's really freaky how nose down you get!

It should be noted that every full scale glider I've flown have wonderful spoilers too, very large and they cut your glide ratio to about a quarter. With full spoilers and a slip you can drop down like crazy. Mainly I use slips to keep me lined up with the runway on landing in a cross wind. Unlike our RC models where any grassy field will do, landing on a long narrow runway is a much different experience with a 50' wingspan.
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Old Aug 26, 2012, 03:03 PM
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I have side slipped with Cubs and high wing trainers and sport planes but gliders, with their high aspect ratio and propensity to tip stall with crossed controls, would make it a little hairy I think. I'll stick with various methods of braking/glide slope control without crossing said controls, thank you. I do, however, use a lot of yaw input no matter what I'm flying or what part of the flight envelope I'm in. When I want to stay in a smallish thermal, for instance, I essentially just establish bank and angle of attack with the ailerons and elevator but really control the turn with rudder.

There are an awful lot of guys who don't use the left stick between the second they are airborne, especially with a powered plane, and chopping the throttle for landing. In fact, I have found that training RC pilots to use the left stick is somewhere between difficult and impossible. It's one of those cases where it seems someone either has the knack for it or not.
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Old Aug 26, 2012, 06:21 PM
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V-tail fairing.

Hi, guys.

I've never been quite happy with the appearance of the tail mount and I can afford a gram or two in the tail so, since the field wasn't available today, I made a little fairing out of foam and Gorilla Glue. I still have a little shaping and smoothing left and I might paint it orange to match the center section of my wing but It dressed it up quite well.
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