[NSRCA-discussion] Rudder

Wed Oct 10 06:54:12 AKDT 2007

Hi Stuart..
    As it can be a very complex and long winded answer I am not going to jump into all the complexities..

    The quick and simple issue is you are standing stationary on terra firma.  The visual picture your brain draws as your model climbs vertical maintaining a true vertical line the model is already corrected for the wind movement at your given flight load. What you see is your model already crabbed into the prevailing and if you try to stall opposite of the crabbed direction you have a much harder workload to perform while airplane is losing all effective control inputs. In this attitude, rudder is last to go with prop blast moving over tail. Elevator will have some effect also but we aren't trying to flop. So to picot the model more than 90º is always harder than pivoting some portion less than 90º. 

Does that help?   Glad to take off list for you if you care to discuss further. 

    Del
  ----- Original Message ----- 
  From: Stuart Chale 
  To: 'NSRCA Mailing List' 
  Sent: Wednesday, October 10, 2007 9:49 AM
  Subject: Re: [NSRCA-discussion] Rudder

  You guys have me a bit confused as well.  I do not think it is as simple as the plane blows with the wind.  Most pattern designs will "weather-vane" .  They will, on there own, establish a crab angle into the wind.  I am sure it varies by design.  The more area behind the CG compared to in front of the CG would make it weather-vane into the wind more (as I see it).  If the plane did not "feel" the wind then why is it easier to stall turn into the wind then with it?  Stalling with the wind (stalling out with a cross wind blowing out) is difficult at best.  When the plane crabs into the wind (on its own) the prop direction (thrust) is now counteracting some of the just getting blown with the wind.  In a perfect design the increased side thrust from the prop would compensate for the opposite movement of being blown by the wind.  I think once you go to knife edge or do rolling maneuvers the added area of the wing getting blown by the cross wind and the fact that  the plane will not "weather-vane" in its pitch axis when on its side causes the plane to "just get blown with the wind" and go along for the ride.

  Stuart

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  From: nsrca-discussion-bounces at lists.nsrca.org [mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of Bob Wilson
  Sent: Wednesday, October 10, 2007 9:20 AM
  To: NSRCA Mailing List
  Subject: Re: [NSRCA-discussion] Rudder

  Wow, and this was just an innocent question about a stall turn!  

  Now, as I pull vertical for the stall turn maneuver, in a cross wind, my mind is going to internally hemorrhage trying to sort out who said what:)

  On 10/10/07, Bob Richards <bob at toprudder.com> wrote: 

  No, it depends on how fast it is coming down. :-) 

  Ken Thompson <mrandmrst at comcast.net> wrote: 

  Wild guess...there is none ;-)

    ----- Original Message ----- 

    From: Kurt Bozarth 

    To: 'NSRCA Mailing List' 

    Sent: Tuesday, October 09, 2007 7:49 PM

    Subject: Re: [NSRCA-discussion] Rudder

    Guess what the wind chill factor is when riding in a hot air balloon?

    Kurt

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    From: nsrca-discussion-bounces at lists.nsrca.org [mailto:nsrca-discussion-bounces at lists.nsrca.org ] On Behalf Of Del K. Rykert
    Sent: Tuesday, October 09, 2007 2:39 PM
    To: NSRCA Mailing List 
    Subject: Re: [NSRCA-discussion] Rudder

    I still find it amazing after all these years it is people with full scale experience that rarely have a problem with the concept Bill just mentioned. 

        Del 

      ----- Original Message ----- 

      From: billglaze 

      To: NSRCA Mailing List 

      Sent: Tuesday, October 09, 2007 3:28 PM 

      Subject: Re: [NSRCA-discussion] Rudder 

      Correct.  The airplane does NOT know the wind is blowing.  If we were moving in the same direction/velocity the wind is moving, (thus matching the airplane direction/velocity), the airplane would have no vector. 

        ----- Original Message ----- 

        From: Terry Beachler 

        To: NSRCA Mailing List 

        Sent: Tuesday, October 09, 2007 2:59 PM 

        Subject: Re: [NSRCA-discussion] Rudder 

        J & B
        Weather vane implies the wind blowing the tail away from and the nose into the wind which would be desirable for (self)correcting for crosswind. This would imply that an airplane on a cross country flight would self correct into a crosswind, no crab necessary. Or the reverse, pilot would have to hold rudder for a couple of hours on a cross country flight. Talk about a way to induce asymmetrical leg muscles...wow! 

        Rudder is used to point the noise into the wind i.e. to induce crab. Full scale pilots make a small coordinated turn into the wind to create crab angle and the desired ground track. I think I read in some pattern stuff that pattern pilots can induce crab and it either presents better to a judge or they can sneak the crab in a way not so easily detected by the judge.  Weathervaning would only happen on the ground with a taildragger, usually the beginning of a ground loop. Or with the airplane on a pylon on the vertical axis, just like a weathervane. 

        Crab angle and track apply here. Crosswind acts upon the whole airplane in flight, not just the tail surface. If we turn this whole situation 90 degrees and fly into a headwind and pull up, the airplane would flop over on its back because of the greater exposed surface of the wing area. The wing would have a greater weathervane effect. But it does not work thataway. 

        Bob and I have been having fun with this one for a while.

        Terry Beachler

        At 13:01 10/9/2007, you wrote:

        weathervane by cause of wind. If you straighten the plane out to look vertical, the track (actual line drawn) will move with the wind and not be vertical and be cause for a downgrade. Someone has a clip from the rule book covering all parts of this. 

        Regards,
        Jason
        www.jasonshulman.com 
        www.shulmanaviation.com
        www.composite-arf.com 

        -----Original Message-----

        From: nsrca-discussion-bounces at lists.nsrca.org [ mailto:nsrca-discussion-bounces at lists.nsrca.org ]On Behalf Of Terry Beachler

        Sent: Tuesday, October 09, 2007 12:53 PM

        To: NSRCA Mailing List

        Subject: Re: [NSRCA-discussion] Rudder

        Do you mean crab (induce by rudder) or weathervane as if the wind is applying a force upon the tail and causing a turn toward the wind about the vertical axis. 

        Terryb

        At 12:10 10/9/2007, you wrote:

        Hi Bob,

        The airplane should weathervane into the wind, as long as the track of the plane is straight (track- actual line/path of the plane). 

        Regards,

        Jason

        www.jasonshulman.com 

        www.shulmanaviation.com 

        www.composite-arf.com 

        -----Original Message----- 

        From: nsrca-discussion-bounces at lists.nsrca.org [ mailto:nsrca-discussion-bounces at lists.nsrca.org]On Behalf Of Bob Wilson 

        Sent: Tuesday, October 09, 2007 8:53 AM 

        To: nsrca-discussion at lists.nsrca.org 

        Subject: [NSRCA-discussion] Rudder

        Some great ideas. 

        I'm going to give the 60-70% rudder expo a shot and see how it works.

        I'd like to do the stall turns on low rate, as Jason reccommends, but when stall turning into the wind my practice airplane will not go vertical (on the downline) unless I have high rates (it weathervanes slightly towards the wind). 

        I also liked John Pavlick's recommendation on the two consecutive rolls.  I'm probably being too anal in coordinating rudder, aileron and elevator because I always seem to run out of room. 

        So much to learn and the damn winter is coming!

        Thanks guys,

        Bob Wilson

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