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Old Oct 10, 2010, 10:16 AM
Out of helis, sanity returning
Tallahassee, FL
Joined Feb 2009
1,948 Posts
Question
Remedial DLG 101- what am I doing wrong?

My TopSky launches nicely, flies well in trim with hands off and indicates lift well. The problem is that when I fly into lift, the nose goes up, speed drops off, and I enter a gentle stall. If I try to circle in lift, the plane porpoises nose up, stall, nose up, etc.

In the notorious dive test, it seems to be completely neutral and would drill into the ground without recovering or tucking if I let it.

As far as I can tell, CG is withing design parameters- 78-84 mm. I recently moved it from about 81 to 78 out of curiosity, but not much changed.

What am I doing wrong?

Rick
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Old Oct 10, 2010, 10:25 AM
Where is the lift?
cptsnoopy's Avatar
USA, AZ, Phoenix
Joined Nov 2005
6,311 Posts
Sounds like you are trying to fly it too slow. Also, you do need to fly it, you cannot just initiate a turn with the rudder/ailerons and expect it to handle pitch all on its own. Perhaps, your down aileron is traveling further than your up aileron? When you do the dive test are you in the same camber setting as when you try to thermal?

Charlie
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Old Oct 10, 2010, 11:16 AM
Launch high. Fly low.
United States, CA, Lake Elsinore
Joined Aug 2003
4,102 Posts
+1
Flying too slow with too much elevator are habits that I've been trying to get rid of for the longest time.

Jun C.


Quote:
Originally Posted by cptsnoopy View Post
Sounds like you are trying to fly it too slow. Also, you do need to fly it, you cannot just initiate a turn with the rudder/ailerons and expect it to handle pitch all on its own. Perhaps, your down aileron is traveling further than your up aileron? When you do the dive test are you in the same camber setting as when you try to thermal?

Charlie
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Old Oct 10, 2010, 11:29 AM
Nothing Special
grouch's Avatar
Middletown, CT
Joined Dec 2003
272 Posts
When my nose goes up, I am in sink. The tail goes up, I am in lift. It sounds to me like you are trying to climb in sink and stalling as a result. Apart from the nose, what other indications are you getting to indicate you are in lift?
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Old Oct 10, 2010, 01:35 PM
Out of helis, sanity returning
Tallahassee, FL
Joined Feb 2009
1,948 Posts
Plane is rising before it stalls

Actually I've gotten fairly adept at recognizing lift from flying the big ones at altitude with a motor glider. I also have a Gambler that thermals nicely when I can throw it high enough to catch a thermal (rarely).

I had some encouragement from a friend who said he found good lift in the neighborhood yesterday (I thought it was over for the year), so I went to fly today. For the first time, I tried using the thermal camber setting in lift, and lo, I was thermalling. Don't laugh- I'm just learning this art.

Anyway, I think what Jun and Charlie said might be the case- flying too slow with too much elevator. Also, I didn't realize that the dive test needed to be done with the wing cambered for thermals. I'll have to try that next time I'm out.

Still open to advice though!

Rick

Quote:
Originally Posted by grouch View Post
When my nose goes up, I am in sink. The tail goes up, I am in lift. It sounds to me like you are trying to climb in sink and stalling as a result. Apart from the nose, what other indications are you getting to indicate you are in lift?
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Old Oct 10, 2010, 01:42 PM
Out of helis, sanity returning
Tallahassee, FL
Joined Feb 2009
1,948 Posts
Charlie-

When you say "down" and "up" aileron, do you mean the direction the aileron actually moves, or the way the wing moves when the aileron is deflected (opposite of the aileron direction).

I know you're speaking of differential aileron here; what is a good setting for that?

Rick


Quote:
Originally Posted by cptsnoopy View Post
Sounds like you are trying to fly it too slow. Also, you do need to fly it, you cannot just initiate a turn with the rudder/ailerons and expect it to handle pitch all on its own. Perhaps, your down aileron is traveling further than your up aileron? When you do the dive test are you in the same camber setting as when you try to thermal?

Charlie
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Old Oct 10, 2010, 01:46 PM
Now fortified with carbon
DLGjunkyard's Avatar
Canada, ON, Puslinch
Joined Apr 2010
2,677 Posts
LMAO..You are trying to fly a blade wing like a gas bag. Just kidding but it sounds like the glider is twitchy as it is with a rearward C/G and you are just flying to slow
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Old Oct 10, 2010, 01:53 PM
Now fortified with carbon
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Canada, ON, Puslinch
Joined Apr 2010
2,677 Posts
Quote:
Originally Posted by 2400RDR View Post
Charlie-

When you say "down" and "up" aileron, do you mean the direction the aileron actually moves, or the way the wing moves when the aileron is deflected (opposite of the aileron direction).

I know you're speaking of differential aileron here; what is a good setting for that?

Rick
A good place to start is 50 percent SOOOO half as much down is up!
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Old Oct 10, 2010, 02:30 PM
Registered User
Congress, AZ
Joined Sep 2001
4,714 Posts
But then Mark Drela recommends no differential.

Gary
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Old Oct 10, 2010, 02:50 PM
usaf3kteam
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Joined Sep 2005
5,607 Posts
When any part of my plane goes up for me it is lift.
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Old Oct 10, 2010, 05:43 PM
Kyle Clayton
Wave Glider's Avatar
United States, VA, Dinwiddie
Joined Feb 2008
2,315 Posts
You could also have too much camber dialed in for your thermal camber setting which is slowing you down too much.
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Old Oct 10, 2010, 11:12 PM
ground penetration specialist
Nathan Schmoekel's Avatar
USA, MI, Grand Rapids
Joined Apr 2007
1,818 Posts
I'm just getting my Preditor two fine tuned and was having the same issue. I finally discovered that while pulling and holding the elevator for the thermal turn that my thumb was also creeping and adding in aileron. I dialed up the exponential setting on the ailerons to 20% so that when my thumb moved side to side slightly the ailerons would not move so much. That little trick really let the wing foil stay cleaner and I can thermal without falling out now.

I have also found that I like the ~~50% down travel aileron differential set-up. In thermal mode when the wing is cambered I use even more differental (probably around 75% less down travel) to avoid the flap like drag of down traveling aileron.

Gave up on rudder to aileron mixes too, because the ratio is seldom perfect, getting rid of the mix also helped keep me from down circling. I basically tune like I'm flying a rudderless ship, except for the fact that I actually have a functioning rudder. I find the rudder is a must for steering with the flaps fully deployed, which is about 60 degrees down for me. In landing mode my aileron differential is set for zero down movement, 100% up; with 125% rudder mixed to the ailerons.
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Old Oct 10, 2010, 11:46 PM
Aurora Builder
United States, MD, Lusby
Joined Nov 2003
3,407 Posts
I personally noticed a large increase in thermalling performance simply by adding aileron differential. It helps keep the wing flatter in the turns for better performance.

Too much camber is also a possibility. My plane is on the heavy side (11.1oz, AG series foils) and really likes to keep the speed up. If I get too slow it stalls, more camber can make the stall sharper and thus make the problem worse. Lately I have been using cruise mode for thermaling (even in the light stuff) and been having better luck. Its also a matter of time with the plane. An hour a day for a week makes a HUGE difference. If you have any desire to compete, you need to practice, practice, and practice some more. On those days where there is no lift, there really is lift and you can get 3+ minute flights out, its just much harder.
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Old Oct 11, 2010, 12:22 AM
Mike M.
like.2.fly's Avatar
United States, UT, Eden
Joined Jan 2010
4,944 Posts
Quote:
Originally Posted by samc99us View Post
I personally noticed a large increase in thermalling performance simply by adding aileron differential. It helps keep the wing flatter in the turns for better performance...
My limited understanding of aerodynamics is not letting me grasp the concept of how aileron differential helps with making flatter turns. Please expound. When I want flatter turns I just tell my thumbs to use less aileron and more rudder.
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Old Oct 11, 2010, 01:37 AM
Where is the lift?
cptsnoopy's Avatar
USA, AZ, Phoenix
Joined Nov 2005
6,311 Posts
Quote:
Originally Posted by 2400RDR View Post
Charlie-

When you say "down" and "up" aileron, do you mean the direction the aileron actually moves, or the way the wing moves when the aileron is deflected (opposite of the aileron direction).

I know you're speaking of differential aileron here; what is a good setting for that?

Rick
Hi Rick,

I am talking about the aileron movement itself. If you give left aileron command at the tx, the right aileron goes down and as it does the left one goes up. If the right aileron goes down more degrees than the left one goes up the overall effect is the same as adding some positive camber (flaps). This will likely also cause the nose to climb as you roll into your turn. If you use equal up and down deflection hopefully you will not have this effect but then you will need to add up elevator as your bank angle increases to prevent the nose from dropping too far.

charlie
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