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Old Jan 05, 2015, 03:22 PM
Sherman Knight
Kirkland Washington
Joined Feb 2002
1,154 Posts
Originally Posted by tailsld View Post
A friend once said a nose heavy plane flies poorly many times, a tail heavy plane flies poorly only once
The real question is how much better does a sailplane, indicate lift and thermal when the CG is just barely ahead of the center of lift? (ie small static margin) The answer is WAY better.

The second real question is how much better does a sailplane handle in gusting conditions with constantly changing airspeeds that you encounter in a turn with a small static margin. The answer again is WAY better.

If you want a great handling, great preforming Sailplane, a very small static margin is always better.

Sherman Knight
Team Horizon Hobby Sailplane
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Old Jan 07, 2015, 03:58 PM
Registered User
USA, FL, Safety Harbor
Joined Sep 2000
169 Posts
CG in % of wing chord at fuselage and flap angle

I'm helping a friend finish up and trim his Mystique. The picture in the manual indicates CG should have a range of 118 to 122 mm from the leading edge. However the picture looks like this is maybe 70 % aft which does not seem right or maybe its an optical illusion. For the first dozen or so trim flights I would rather start off with around 33% and like others have suggested move the CG aft but with a margin so as not to have tip stall. Like Sherman's qoute....better to fly poorly many times......

Any one have a dimension that is conservative CG to start off with or a percentage I can calculate and start off with.

Second question is the recommended 25 degrees of flaps. I like at least 45 degrees of flaps but getting that angle may be difficult with the recommended pushrod and flap horn design. Has any one achieved 45 degrees of flaps with stock design or does this require a bottom flap horn and exposed flap servo arm design? The pictures show a slot in the flap servo cover but nothing goes thru the slot.
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Old Jan 08, 2015, 09:01 AM
Mulit-Platform Pilot
barracudahockey's Avatar
United States, FL, Jacksonville
Joined Sep 2004
3,697 Posts
I cut slots in the trailing edge, With that I get plenty of flap throw. I'd highly suggest watching the build video on YouTube that John did before you try to install the elevator and flap linkages
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Old Jan 08, 2015, 07:48 PM
Sherman Knight
Kirkland Washington
Joined Feb 2002
1,154 Posts
Originally Posted by VicT View Post
Like Sherman's qoute....better to fly poorly many times......
VivT, Sorry, but not my quote. What I guess I was trying to say is that if you want this sailplane to thermal like a sailplane, show you lift when you fly through it, land slowly when you want, fly slow when you want, and require little elevator input (other than up stick to stay in the turn) when turning in a thermal you want the CG just barely ahead of the center of lift.

Amazingly, if you are a propeller head and you fly a lot with the motor on, the same recommendations apply.

Don't worry about the decalage. It is a full flying stab and will work itself out using a dive test (shallow angle of decent test)

If you hand toss, just don't throw it UP. Throw the nose at the horizon line. It will actually feel like you are throwing it down. If it is nose heavy, it may balloon up rather quickly as it leaves your hand. Ballooning as speed increase is the sign of a nose heavy sailplane.

Shallow angle of descent test (previously known as he dive test)

1. five or 6 mistakes high.
2. set Trailing edge to cruise.
3. Trim elevator to make the sailplane fly as SLOW as possible, then slow it down some more.
4. Push elevator stick forward until the nose is down about 20 degrees. After about 1.5 to 2 seconds let go of the stick. If the plane balloons up, it is nose heavy.
5. Land
6. remove some nose weight and put in a couple of clicks of down trim.
7. Start with number 2 and repeat. Trimming it again until it fly's as slow as possible before the dive is critical.
8. repeat
9. and repeat
10. and repeat until the nose comes up very very slowly.
11. Don't pay attention to the decalage. It is what it is.
12. If using flight modes, change the elevator trim on ALL Flight Modes now to match that used in cruise.
13. If speed mode uses reflex, nose down 20 degrees and input down elevator trim until the nose doesn't come up at all.
14. If launch mode uses the same TE as cruise mode, input down elevator trim in launch mode until the nose no longer comes up under full throttle. Nice stable hands off climb.
15. If you experience tip stalls, put 1/4 ounce nose weight back in and retrim for launch and speed mode. Or add both differential and aileron to rudder mix in cruise mode and see if it goes away. Tip stalls are more a function of how you fly the sticks and or control surface setup and not the physical attributes of the aircraft.

For this test to work, the sailplane must be trimmed to fly as slow as possible before each dive test.
As the CG moves back, you will notice the sailplane will fly slower and slower.
As the CG moves back, the sailplane will bounce around more but at the same time indicate lift much better.
As the CG is moved back, the sailplane will thermal better.
As the CG is moved back, ballooning goes away.

If you like a plane that flies like it is on rails, this may not be for you. Sailplane that fly like they are on rails do not fly like sailplanes. They don't indicate lift very well, it takes much stronger lift to make it go up, it will balloon when ever airspeed goes up (turning into the wind or even a gust can cause balloon)

I don't know how nose heavy this sailplane is. I have seen sailplanes (like the old 2 meter spirit) where removing 2.4 ounces from the stock setup was pretty common.

If you had to add weight to the plane to balance per the plan, start moving the battery forward at the same time you are reducing nose weight. the goal is the lightest sailplane possible. That would be no nose weight and move the battery around to move the CG.

Sherman Knight
Team Horizon Hobby Sailplane
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Old Jan 17, 2015, 12:26 PM
Proud member of LISF and ESL
LI, New York, USA
Joined Mar 2003
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Now that you have this really cool e-glider, why not have some fun with it. Try an ALES, Altitude Limited Electric Soaring contest. We will be holding one in April on Long Island.

You can learn more here:

If you are an accomplished pilot you an fly Expert or Sportsman but if you are new at this you can fly Novice. Novice pilots fly FREE.
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