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Old Aug 03, 2006, 11:02 AM
Chuck 'Em and Chase 'Em
Fly2High's Avatar
United States, NY, Plainview
Joined Aug 2005
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Clinic given by Mark Drela at L.I. Hand Launch Classic

Guys,

Through the kindness of his heart Mark has helped me out tremendously already with the preparations for the Long Island Hand Launch Classic contest (Aug 5 - 6). thank you Mark. I can not thank you enough already.

Now I owe him more than I could ever. He has agreed to give a HLG clinic on Saturday after the contest. These are the topics he will be covering. Come whether you are flying or just spectating prepared with questions.

LISF HLG Clinic


Sailplane gear

Servos – most important features

Ailerons: Centering, resolution, strength(JR241,D-60)
Elevator: Centering, resolution, reliability(D-47,HS-50)
Rudder:Stiffness,gear strength(JR241)

Receiver

Many smallRX’swork well:M5,Quantum,Electron-6,555,Berg?, ...

Batteries

Weight/runtime tradeoff. Easy field recharging(e.g. Sirius200) makes a smaller pack practical.
1/3AAA 140-170 mAh, 17g
1/2AAA 200-230 mAh, 24g
1/3AA 300-350 mAh, 30g

Sailplane build

Pushrods

Key requirements: Absolutely no slop, stiff, light, low friction.


Stainless: 0.018” rudder, 0.014” elevator minimum. Lightest, lowest friction. May buckle if not
fully supported.
Carbon rod: 0.030” typical. Easier to install. More resistant to buckling.
Housings: Etched teflon. Everything else is lame.
Pushrod ends: L-bend with wire-insulation retainer on each end works well.


Z-bend is awful by comparison — will always have some slop.


Antenna options

In boom. If stock antenna is heavy, replace with light wire(26gaugeisOK).Easiest,but heaviest
and most tail-heavy.

In wing. Magnet wire buried in exposed foam at hinge. Light, no effect on balance. Most work.

Stainless rudder push rod is antenna. Lightest solution. Use acid flux to tin pushrod end outside of
fuselage, clean off, then solder on antenna with rosin flux.

Control setup

Aileron differential: NONE.
It produces an unwanted nose-down pitch input with any aileron input.


Camber control (aileron glider): RECOMMENDED.
Put on a 2-position or 3-position switch which is easily accessible. A slider is overkill.


Braking: STRONGLY RECOMMENDED.
Put on throttle stick. Drops flaperons on aileron glider,  35. max deflection. Or drops flap on
r/e glider, 40. -70. max deflection.


Elevator compensation: STRONGLY RECOMMENDED.
Should see no speed change with camber change. For brake deployment, can either keep speed the
same, or slow down a bit.



Aileron ! rudder mix: SMALL AMOUNT IS A GOOD IDEA.
Cancels adverse yaw to make aileron stick a pure roll control. Lots of mix also provides roll control
via rudder when flaps are deployed and aileron action has no effect(or just use left thumb).


Launch presets: STRONGLY RECOMMENDED.
Use enough up-elevator preset to give pull up radius of 30-40 feet. Some rudder preset to the outside
of the circle is also recommended, especially if rudder is smallish, and/or linkage has some slop.


Trimming and Flying

Finding your CG

Use Dive Test to find neutral-stability point(aft CG limit). Fine tune as desired.

Aft-CG pros: Stronger pitch-response indication when flying into lift.
Less elevator trim change required to change airspeed.
Aft-CG cons: More pilot work required to twiddle elevator constantly.
Prone to tuck-in when flying fast.
Fwd-CG pros: More resistant to tuck-in.
Less demanding of constant elevator control.
Fwd-CG cons: Must re-trim elevator significantly to change airspeed.
Slight L/D penalty(a few precent at most).

The most likely situation for tuck-in is during a fast up wind penetration glide. Hence,it is prudent
to put the CG just forward enough so that the glider will just barely pull out of the Dive Test when
trimmed for this speed(typically20-25 mph).

Launch techniques

Timing is at least as important as raw power.
Accelerate all the way to the release – most power is over last 180. of rotation. Always keep arm
fully extended — NEVER try to “pull in” by bending arm at the elbow.


Once technique is good, add power by speeding up everything. Don’t change basic motion.


Always launch into the wind, even if planning to run downwind.


Thermalling basics

Thermals ”suck air”. Change in prevailing wind is towards nearest/strongest thermal.


Most thermals drift with the prevailing wind speed. You must drift with thewind toremaininlift.


Fundamental rule of lift detection: Glider tries to ”get away” from lift.
If lift is to the side: Glider will bank away to other side.
If lift is straight ahead: Glider will pitch up and slow down.
If lift is straight behind: Glider will pitch down and speed up.


The instinctive response should be to overpower any uncommanded roll or pitch upset.



Mark thanks again

Sincerely,

Frank
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Old Aug 03, 2006, 01:16 PM
No slope for richardo
Endless Sloper's Avatar
Seattle, WA
Joined Jun 2005
2,128 Posts
Would be some work, but could someone get a video of this for those of us on the other coast?
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Old Aug 03, 2006, 02:50 PM
Chuck 'Em and Chase 'Em
Fly2High's Avatar
United States, NY, Plainview
Joined Aug 2005
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I have a 'video???' of the discussion he did at CRRC HLG contest. I will see if we can tape this one too and convert both to DVD.

Frank
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Old Aug 03, 2006, 03:06 PM
Intermediate Multi
Trisquire's Avatar
Columbus, OH
Joined Mar 2005
3,259 Posts
Quote:
Originally Posted by Fly2High

Camber control (aileron glider): RECOMMENDED.
Put on a 2-position or 3-position switch which is easily accessible. A slider is overkill.
Frank, In terms of degrees, what are these settings typically, for those of us who can't attend? One reflex, one camber, and one straight?


Tom
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Last edited by Trisquire; Aug 03, 2006 at 03:21 PM.
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Old Aug 03, 2006, 03:41 PM
wishes this caption was longe
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wilson, nc, usa
Joined Dec 2005
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good stuff!
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Old Aug 03, 2006, 03:59 PM
Chuck 'Em and Chase 'Em
Fly2High's Avatar
United States, NY, Plainview
Joined Aug 2005
8,081 Posts
I know that with the SG II he has one reflex and then 2 camber. Look at the first plan sheet for the amounts. On the SG II Mark has the wings such that reflex is when the flaperons are even, not above the trailing edge. the 2 cambers are then down and then down further.

Does this help?

Frank
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Old Aug 03, 2006, 06:28 PM
Intermediate Multi
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Columbus, OH
Joined Mar 2005
3,259 Posts
Great. Thanks Frank.

Regards,
Tom
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Old Aug 03, 2006, 07:42 PM
Looking for lift...
Milford, NJ
Joined Mar 2005
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Thanks Frank & Mark. I guess I better bring my notebook.
Frank when you convert to DVD will that be available for purchase?

Doug
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Old Aug 03, 2006, 08:10 PM
Fiberglass dont bounce???
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Zion, Il.
Joined Sep 2002
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Here is the Super Gee II flaperon settings ...R...
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Old Aug 03, 2006, 08:11 PM
PNF
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Los Gatos, CA
Joined May 2005
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I love the spirit of academic research where findings are shared - not horded. Even that summary was insightful as heck. Thanks, Mark.

-steve
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Old Aug 04, 2006, 07:19 AM
Chuck 'Em and Chase 'Em
Fly2High's Avatar
United States, NY, Plainview
Joined Aug 2005
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I am sure the quality will be poor but I will see if it is even worth selling. I do not have a remote mic but will setup a tripod for this one. I will keep you posted as to how it comes out.

Frank
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Old Aug 04, 2006, 09:27 AM
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Chris Gibbs's Avatar
York, UK
Joined Oct 2005
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Quote:
Fundamental rule of lift detection: Glider tries to ”get away” from lift.
I like that analogy
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Old Aug 04, 2006, 09:33 AM
Gustavo Exel
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Switzerland, GE, Geneva
Joined May 2003
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Quote:
Originally Posted by Fly2High
Fundamental rule of lift detection: Glider tries to ”get away” from lift
Interesting indeed, and gets me thinking what do the free flight guys mean by "trimming to make it enter and hook the thermals"...

That question alone was reason enough to bring me closer to free flight and build some planes, just to try to undestand it. Unfortunately I haven´t had much time to really concentrate on that...
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Old Aug 04, 2006, 09:47 AM
flotation device
Colorado Springs
Joined Jan 2006
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Wing offset, warp, stab tilt, and rudder are all used in conjunction to make a freeflight model turn more tightly in rising air.
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Old Aug 04, 2006, 09:57 AM
Gustavo Exel
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Switzerland, GE, Geneva
Joined May 2003
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Quote:
Originally Posted by doctorgonzo
Wing offset, warp, stab tilt, and rudder are all used in conjunction to make a freeflight model turn more tightly in rising air.
That´s what I hear, but I´d like to understand in practice and in theory how it works! Will have to wait until I find time for that, though...

To start with, how can a plane sense it´s in rising air without using any clue from the ground? That´s been discussed extensively on the threads about planes flying tail high on thermals and my understanding is that the plane can´t sense that.

Well, I think that´s a subject for another thread, on another rcgroups forum...
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