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High-Start technique

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Old 09-01-2005, 05:58 PM
  #1
Test005
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Default High-Start technique

I have the Great Planes Fling glider
Tonight I flew the plane for the first time and also used the included high-start.

There was absolutely no wind tonight, and when I launched the glider it zoomed up high, but the plane lost lots of speed and the parachute dropped about halfway to the peg.
Usually the plane had no airspeed at the top of the launch and wanted to stall a bit before I dived slightly to gain speed.
Mostly it didn't have enough speed to release itself and I flew for a few seconds until the launch line disconnected = No airspeed at end of launch.

My (theorethical) idea of a high-start was:
-Plane goes up
-pops off the hook at 90 degree angle to the ground (precisely over the peg)
-Plane has aquired lots of airspeed from the launch and can use that speed to climb further

Clearly this is no what happens when I launch,,,help!

Should I do something to the high-start line, like lenghtening it or shortening it?
Should I use the elevator when launching and dive a bit or pull back a bit?
Is there something I need to do on days like today with no wind?

/Edit: I stretched the line 30 yards, as recommended by the manual to be the maximum stretch.


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Old 09-01-2005, 08:38 PM
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Default RE: High-Start technique

Your understanding of how the high start should work is correct....

If the glider flies normally once it is off the high start, and the model's CG is in the correct location, I would ensure the hook location is correct... From your description, it sounds like the hook is too far behind the CG, causing the nose to pitch up when it is on the high start.
If the hook is too far forward, the glider won't gain any altitude, if it is too far aft, it will climb too quickly.

On the launch, as the glider reaches the top, you should be able to pitch the nose down to get off the high start.

HTH

Jim
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Old 09-01-2005, 10:01 PM
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BMatthews
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Default RE: High-Start technique

When you hang the model upside down from the twohook it should hang very slighty tail heavy. From slightly below level to maybe 10 degrees tail down. The closer to level the more the model will want to pitch up and slow down. Some folks actually fly with the hook behind the CG but they get used to using some down pressure on the elevator during launch.

If you're releasing the model in too level an aim it'll tend to accelerate far more then it should and pitch up and perhaps over pitch to a stall without a nudge of down. Try THROWING it at an upward angle of about 30 degrees. Don't just let it go, you need to THROW it like it is being tossed without a highstart. It's tough to feel thru the pull of the high start but a good throw is important. Not so much for something light like the Fling but when you start flying that BoT it's critical. A sloppy launch on the larger models where all the pull is downwards off the hook means the wing is stalled as soon as it leaves your hand and a quick snap and crash is the outcome. I've seen it far too often. So nose up and launch it like you MEAN it. For the Fling that means a flick of the wrist. For the BoT it means an Olympic style javelin throw complete with the side stance and major grunt..... just be sure the Tx antenna is out of the way...
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Old 09-02-2005, 04:29 AM
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Default RE: High-Start technique

Ok, balance on the tow hook seem to be OK.
Two things I will correct:

-Throw the plane (so far I've just released it)
-Angle the nose upwards (so far I've released the plane horizontal to the ground)

Can you please give me any input on the wind factor?
wouldn't I get more "power" if I had a slight headwind?
So far, it's been 0 wind and I suspect that the stored power of the bungee cord is used up before the glider hits the top because there's no wind to help the glider fight the pull of the bungee?
That woud mean shorter line for no-wind days.

(This is theoretical ideas, but I do sailing (boats) and know about lateral balance and how a sail works to get powered)



... Perhaps my high-starting technique is good enough because it sure does launch fast and high, but I would like to have some speed when the hook is released.
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Old 09-02-2005, 12:34 PM
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Default RE: High-Start technique

Yes, a bit of a headwind can make a big difference to the launch height. The wind is like getting some free gas...

Either go for a shorter line or do what the rest of us do and just use what you got. I could be wrong but I believe that the height you get now would match the height you get with a shorter line if you match the line such that the highstart is "just" lifted totally off the ground. So there's not really much to be gained. In other words the power in the rubber will get you so high and it doesn't make much difference if that height is with the line straight up and down or if it's longer and at an angle.

Please do practice the proper launch styles. I've seen far too many models broken up just because folks do not understand the forces at work during a lanch. My favourite is " I don't know what happened, there was LOTS of line tension!". That's the problem, line tension is like fake wing loading in this situation. And the higher the "loading" the more important that the model is thrown HARD so that it has enough flying speed to deal with it as it leaves your hand. The Fling and mini start will just need a gentle push but the BoT will need a full armed HEAVE to do it right. I wasn't kidding about looking like a javelin thrower. Legs apart, a full one leg forward and rear leg along the path of the line side arm stance with line across your chest, arm fully back with tail of model just about kissing the ground behind you and then HEAVE it along a 20 to 30 degree upward angle. I've seen photos of guys like Joe Wurts with their feet about a foot off the ground and their body stretched out like a rubber band. I don't know if folks still do it but it was quite common on some contest models to use a patch of medium grit sandpaper along the fuselage to help with a good grip if the fuselage was a bit small in section.
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Old 09-02-2005, 04:25 PM
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Default RE: High-Start technique

LOL, I have sandpaper on my Fling
I put it there as I felt I had no grip when the line was stretched.... (Didn't know people actually did that)

Tonight I've flown the Fling a bit more and now I have great starts.
There was some wind and it felt like it really helped.
I also launch more nose upward and give the plane a good throw... Now I go all the way up on the hi-start and have good forward motion as the plane releases from the line.

This has been good training in preparation for the BoT.

Thanks alot BMatthews & Jimmbbo, appreaciated!!
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Old 09-02-2005, 10:23 PM
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Default RE: High-Start technique

Best of luck with this new intrest of yours and be sure to come back with a picture of your big grin once you catch and trap that first thermal.
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Old 09-07-2005, 04:18 PM
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Default RE: High-Start technique

We usually get a mixed bag of launches on each outing. Once a thermal is just upwind of you, the wind will temporarily be getting sucked into that thermal and will shift 180 degrees and be coming from behind you. You don't want to be moving the pin for every little wind shift, so assume some of your launches will be into the wind, and when a thermal is bearing down on you. you'll be chucking it with the wind and your launch height will suffer.
That ain't all bad, though. If you can just get enough air under the wings to reach that thermal that's up just past the pin, hang on!!
Mostly watch the planes speed. If she's really ripping you can feed in a touch of up elevator, if she's dogging it then give her a little down elevator to get her speed up. On a down wind launch you'll need a lot of down to just keep it moving at all.

It's all good.
Perry
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