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Mar 05, 2021, 04:53 PM
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Zohd Drift horizontal stabilizer modification


ZOHD DRIFT HORIZONTAL STABILIZER MODIFICATION
https://www.sciencedirect.com/topics...ring/tailplane
It is convenient in this work to measure incidence, not relative to the chord line as is normal, but to a line parallel to the flow direction which results in zero lift. This line is known as the ‘no-lift line’, and eliminates the no-lift angle from our equations even for cambered aerofoil sections.

HORIZONTAL STABILIZER MODIFICATION ADJUSTMENTS TO SURFACE
AREA, LOCATION, AND INCIDENCE ARE USED TO ACHIEVE NEUTRAL STABILITY.
I DID THIS AT THE FLYING FIELD BY TRIAL AND ERROR TO FIND THE CORRECT HORIZONTAL STABILIZER INCIDENCE, AND CORRECT THE
MODEL'S PITCH CHANGE TENDENCY BETWEEN POWER AND GLIDE.
RESULTS:
TRIM NOW REMAINS VERY CONSTANT IN DIFFERENT FLIGHT MODES. THE THROTTLE IS MORE EFFECTIVELY USED FOR CLIMB, CRUSE, AND GLIDE TO LANDING.
THE MODEL WILL NOW FLY WITH ONE TRIM SETTING.
ADDITIONALLY, AEROBATICS IS IMPROVED AS WELL AS THERMAL
MANEUVERABILITY AND SPOT LANDING.
Last edited by donaldsunland; Mar 31, 2021 at 12:24 PM.
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Mar 06, 2021, 09:43 AM
Launch the drones ...
I have one of those - it would dip and dive on its own, due to the wings being so flexible. I stiffened em with lamination - but it never behaved right in the air for me - tried several COGs too. Now - it's a basement ceiling hangar queen. Glad you got yours tamed.
Mar 14, 2021, 12:04 AM
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Zohd drift horizontal stab fix.


Hey Tim
Your experience with the model is due to the horizontal stab
being too small with incorrect incidence, resulting in pitch instability
at higher angles of attack, and increased bank angles, falling directly
in the wing wash where it quickly becomes ineffective.

When you look at low wing aircraft, you will see the tee tail
utilized to overcome this. Conversely, high wing aircraft the opp.
It is a design flaw, but is easily fixed by resizing, relocating and
adding in a degree or two incidence to the horizontal stabilizer.
Make a new balsa stabilizer shaped like the one I designed.
SHIM THE LEADING EDGE DOWN AS REQUIRED TO GLIDE
WITH A HAND TOSS WITH NEUTRAL ELEVATOR.
Thanks for the interest,
Don, glider pilot since 1974
Mar 14, 2021, 06:24 AM
Launch the drones ...
Quote:
Originally Posted by donaldsunland
Hey Tim
Your experience with the model is due to the horizontal stab
being too small with incorrect incidence, resulting in pitch instability
at higher angles of attack, and increased bank angles, falling directly
in the wing wash where it quickly becomes ineffective.

When you look at low wing aircraft, you will see the tee tail
utilized to overcome this. Conversely, high wing aircraft the opp.
It is a design flaw, but is easily fixed by resizing, relocating and
adding in a degree or two incidence to the horizontal stabilizer.
Make a new balsa stabilizer shaped like the one I designed.
SHIM THE LEADING EDGE DOWN AS REQUIRED TO GLIDE
WITH A HAND TOSS WITH NEUTRAL ELEVATOR.
Thanks for the interest,
Don, glider pilot since 1974
Thx. I may try this.
Mar 14, 2021, 02:45 PM
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Thread OP
In view 2, looking fwd to aft with the model level,
the stock stabilizer is still installed temporarily,
but is completely obscured behind the wing.
you can also see the new corrected incidence
and proper location to the wing chord.

The last view shows the downward negative angle of the
tail boom to level wing chord and is a major design flaw on this model.
The boom should be parallel to the line of flight.

I am not certain if this misalignment is poor quality control, or may have been
done to allow sufficient clearance for the prop.
Never the less, it is the main reason for all this rework.
Last edited by donaldsunland; Mar 31, 2021 at 01:12 AM.
Mar 14, 2021, 02:50 PM
Launch the drones ...
Quote:
Originally Posted by donaldsunland
In view 2, looking fwd to aft with the model level,
the stock stabilizer is still installed temporarily,
but is completely obscured behind the wing.
you can also see the new corrected incidence
and proper location to the wing chord.
Perfect - thx - something to calibrate the changes to now.
Mar 29, 2021, 05:52 PM
Registered User
Thread OP
HI AGAIN
https://rcplanes.online/cg_calc.htm
FOR CG PLUG IN DIMENSIONS HERE DESIGNED INTO ANY MODEL

I FAILED TO MENTION THE EFFECTS OF AFT C.G. AS NOTED ON THE UNDERSIDE WING OF THIS SHORT
COUPLED MODEL, AND IT'S EFFECTS ON ALL FLIGHT CHARACTERISTICS, ESPECIALLY STALL
AND STALL RECOVERY.

As a very general rule of thumb the CG will be about one-quarter to one-third of the wing chord (width) back from the leading edge of the wing. The main spar, if there is one, often lies in this general area.
Aft CG. The relationship between aircraft performance and CG location is simple: by moving the CG forward and aft, you change the amount of tail down force and lift you need for stable flight. If you need more lift, you create more induced drag, and your performance goes down.
What if the CG is too far aft?
If the CG is too far aft, it will be too near the center of lift and the airplane will be unstable, and difficult to recover from a stall. If the unstable airplane should ever enter a spin, the spin could become flat and recovery would be difficult or impossible. A SPIRAL DIVE IS JUST AS BAD.

THANKS FOR THE INTEREST.
DON
A&P AND PRIVATE PILOT SINCE 1974
QUALITY ASSURANCE NORTHROP/GRUMMAN CORP. MILITARY DIV. 33 YRS. RET.
BOEING CORP. COMMERCIAL DIV. 1980-2012
HUGHES HELICOPTERS MILITARY & COMMERCIAL DIV. 1979
A&P WINGS WEST, PIONEER AVIATION 1974- 1979
MODEL FLYING POWER, CONTROL LINE, FREE FLIGHT, GLIDER, HELICOPTERS, 67 YEARS -TODAY .
MY OWN DESIGN JC-16 SLOP RACER VINTAGE 1988,
BASED ON THE JACK CHAMBERS JC-16 AIR FOIL 8.3 % THICKNESS.
Last edited by donaldsunland; Mar 31, 2021 at 12:12 AM. Reason: CORRECT SENTENCE


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