Re: Sparrow strainer stall

Jay Scheevel

Hi Bruce,


If the tufts are pointing any direction other than straight back, they are caught up in the vortex within the separation bubble. The size of this bubble increases dependent on the airflow conditions. Could be that when you are in cruise the bubble is small and then when you see the “stalled strainer”, the bubble has become large enough to include the sparrow strainer.  I have superimposed some wind tunnel smoke trail snapshots on my canard at three different attack angles, so you can see the size of the bubble (where the smoke trails get jumbled). The tubuelence always there to some extent because of the pressure discontinuity at the trailing edge. The only time it goes away is on a symmetrical airfoil at zero incidence. The square edge on the trailing edge of the LS1 is an attempt to limit the size of that turbulence bubble at low AOA. It does not work very well when the elevator is deflected.




From: <> On Behalf Of Bruce Crain
Sent: Thursday, March 19, 2020 8:32 PM
Subject: Re: [Q-List] Sparrow strainer stall


Say Jay I

think the tufts on the elevator were moving the same direction in normal cruise (from outboard to inboard) regardless of the sparrow strainer stalling or not stalling.  It could be exacerbating where the air flow goes due to the strainers moving up and being blanked by the elevator perhaps.  I except when I pull the stick and lower the strainer back to cruise pitch or lower it still takes stalling the canard to alleviate the sparrow strainer stall.  Maybe my outboard strainer is the difference between my Q and others but then I believe DFly's have outboard maybe.  Charlie can you back me up on that?  Or maybe no one else has actually pulled up and unloaded their Quickie to the extent that I have.


It has bothered me for a few years that the airflow on the elevator move inboard like it does.  To an aerodynamisist it means a big loss in speed doesn't it?  I am sure when the LS1 airfoil came out they had it working well.  Maybe it's just me.

Bruce Crain  

Please note: message attached

From: "Jay Scheevel" <jay@...>
To: <>
Subject: Re: [Q-List] Sparrow strainer stall
Date: Thu, 19 Mar 2020 09:39:12 -0600

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