Allegro-List Digest Archive

Wed 06/25/08


Total Messages Posted: 2



Today's Message Index:
----------------------
 
     1. 06:43 AM - Allegro vortex generators on vertical stabilizer (TIM MOSES)
     2. 08:50 AM - Re: Vortex generators update (Hugh)
 
 
 


Message 1


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    Time: 06:43:34 AM PST US
    From: "TIM MOSES" <tcmoses@earthlink.net>
    Subject: Allegro vortex generators on vertical stabilizer
    Has anyone tried VG's on the vertical stabilizer to enhance the rudder stability and thus yaw stability of the plane with feet off the pedals?


    Message 2


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    Time: 08:50:55 AM PST US
    From: "Hugh" <hgmckay@bellsouth.net>
    Subject: Vortex generators update
    Paul: I have tried to reach Stolspeed at their email address with a few questions. I keep getting my message returned. Can you give me the proper email address to use to reach them? Also from your dissertation on the use of the Feathers VGs, am I correct that with the VGs on the outboard of the wings only, the landing attitude of the plane is steeper than without the VGs? The landing attitude of the plane at touchdown under normal conditions is still fairly steep (in my opinion). Your statement that with the VGs on the wings only, one could easily drag the tail on takeoff or landing disturbs me. I certainly don't want to begin to do this. Please explain this further to me. I am certainly not going to put something on my plane that causes me to risk dragging the tail! Hugh -----Original Message----- From: owner-allegro-list-server@matronics.com [mailto:owner-allegro-list-server@matronics.com] On Behalf Of aerosiam Sent: Tuesday, June 24, 2008 1:21 AM Subject: Allegro-List: Vortex generators update To answer Hugh's question in his post titled 'Vortex Generators' Stolspeed say the VGs can be placed at 8-12% of the chord. I wanted to place them quite far forward (7%)for the following reasons The Allegro has a fairly sharp leading egde Air velocity is probably highest around 7% chord at the stall The tapered sections are quite narrow (and the most vulnerable to a stall) and the vortices need time to propagate. I discussed this with the VG designer and he agreed. Fitting is simple and the Stolsped instructions are very good. The tapered section takes a little head-scratching but is actually easy. You only need to mark 3 points on the wing. On the constant chord section mark 2 points 2.14 inches back from the leading edge. The first point (A) is at the wing root, the second (B) exactly where the chord changes from constant to tapered. Ping a chalk line. Place the front tips of the VGs touching the chalk line. This puts the tallest part of the 'fin' at 7% Now measure the chord at the wingtip fairing join (ignore the fairing itself) and mark point C at 7% minus 0.8 in (the distance from the front tip to the fin of the VG.) Ping a chalk line from point B to C (start of tapered section to the wingtip - ignoring the fiberglass fairing) The back of the template must be 90 degrees to the airflow. Mark a series of lines parallel to the main spar. It's probably easier in removable felt pen rather than chalk to avoid the dust for adhesion. Use the lines as a reference for the back of the template. A couple of notes... Suggest you try only the tapered section first then full span if you want. If you are going to do stall tests with and without VGs, are you current and familiar with stall recovery? I flew with a chief instructor which was a comfortable feeling! Did you get your stall warning working? Talked to the Italian dealer who said the Allegro will recover from a spin normally and immediately with full opposite rudder. After 3 turns autorotation speed increases. See http://www.mcp.com.au/allegro/flight-test/flight-test.html about sharp stall and wing drop power on See http://www.aero-siam.com/page143.html for VG flight report and pictures of VGs Suggest you fit the horiz stab VGs and test fly before fitting the wing VGs Aircraft will take off sooner and land and float a little later. Touchdown 31 kts CAS in ground effect. Easier to bump the tail (and take off too soon) because the nose angle is higher for a given stick input. I have a dynon pitot set several degrees below incidence. The factory pitot does not seem to suffer position error. I will check measurements when I am next at the field. Regards Paul Read this topic online here: http://forums.matronics.com/viewtopic.php?p=189510#189510




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