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The push rod forces are definitely there.
The trim system that keeps those forces from
showing up at the control stick.
. . . . unless you're using servo tabs . . .
.
Yes, I want to map the drag bucket for various flap
conditions.
NASA tech paper 1865 shows it's effect. I want to
expand that on the 300 series.
I believe it can add some efficiency points if
utilized.
Wolfgang
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Uh, the push rod forces should be zero when trimmed. If one
cannot reach a trimmed configuration, then force will be required to reach
sustained level flight. One can only wonder about the position of
the trimming device (there are so many different methods) when one then
calculates forces necessary for level flight at different
airspeeds/configurations.
Wolfgang is seeking the "drag bucket" for different flight
regimes. The purpose is unknown. Each configuration change
affects either lift (induced drag) or parasitic drag or both.
Faster = less induced drag, more parasitic drag. Slower = more
induced drag, less parasitic. Parasites are everywhere.
http://www.charlesriverrc.org/articles/asfwpp/lelke_airfoilperf.htm clarifies
the "drag bucket" concept. Good (an extra "o" converts God to good)
Is only of concern at cruise configurations. Why? Because
anything else is confounded by other variables - density altitude, wind,
efficiency, etc. The designer defined the cruise range as the best
conditions (altitude, power, etc) where the longeron was level.
Other things can affect drag, engine cooling, laminar flow because of
smooth surfaces, weight (lift-induced drag), wax (parasitic drag), etc.
etc. etc.
Who cares at other speeds less than cruise - we know that max
efficiency can be reached when parasitic drag and induced drag cross at
some minima. Uh, the old max range vs max endurance question.
Frequently, best efficiency occurs at best glide speed (like 107 KIAS in a
half loaded 320). So what? Do I care if I can reach
Austin, TX in 8 hours using only 20 gallons or 4.3 hours using 30
gallons or 4.8 hours at best power requiring a fuel stop to maintain
minimums (43 gal tank). Of course. But I don't need anything
more than ROP/LOP fuel burns and associated TAS - fortunately for my
very slick bird, there is only a loss of 6 or 7 knots for a drop of 2 gph
from ROP to LOP at some useful altitude. So, I get >1 hour
more endurance at LOP and I can see if that 28 NM difference (4
hours) is worth the 1 hour refueling stop. Uh, Austin is a flip
of the coin at 820 NM (wind and weather depending).
Scott Krueger
LNC2 320
In a message dated 8/8/2010 6:46:31 P.M. Central Daylight Time,
chris_zavatson@yahoo.com writes:
The MKII tail is a little different. Push rod forces are
zero for all trimmed conditions.
Chris Zavatson
N91CZ
360std
From: Wolfgang
<Wolfgang@MiCom.net>
To:
lml@lancaironline.net
Sent: Fri, August 6, 2010
10:06:44 PM
Subject: [LML] Re: flap
coupling
I have taken elevator pushrod force
measurements and was surprised.
Elevator pushrod forces to stick forces are
about 6.5 to 1
The trim system, when dialed in, provides
these forces.
At 190 imph and -7º flaps, there is a
60lb forward force.
At 80 imph and 10º flaps, there is about
zero force.
At 80 imph and 20º flaps, there is a slight
(-1lb) rearward force.
These numbers are with the horizontal
stabilizer built at -1.2º
- - - plans range is -0.5º to
-1.0º
An input from the flap bellcrank of
about 20-40 lb at -7º would be good,
tapering down to zero lbs at 10º
flaps
A horizontal stabilizer built at -0.5º
would, of course, change these numbers.
Comments ?
Wolfgang
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