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     

 

The MKII tail is a little different.  Push rod forces are zero for all trimmed conditions.

 

Chris Zavatson   

N91CZ   

360std

www.N91CZ.com

 

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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