Re: Sparrow strainer stall

Bruce Crain

I don't  have a clue as it has been a looong time ago when I set up the strainers.  They were adjustable at first but the  extra bolt heads sticking out in the wind and also the rough texture of the unfinished stainers made the elevator ride up until I put an upside down flap on both of them to make them ride level in cruise.  When I finally glassed them into place they were more effective without the bolt heads so I sanded off enough of the upside down flap to get back cruise level.  Then I filled and sanded the strainers and again they were more effective so I had to sand off equal amounts of upside down flap on the strainers for cruise pitch.  Then lastly I finished primed and painted them and I ended up sanding all but a very small amount of those upside down flaps.  So I got back to almost plans built for level.  Then the stall showed  up when pushing over to lower the nose.
I probably have the most experience with the strainers in "Quickiedom" but then mine are a bit non standard.
I am almost finished with pulling the number 4 cylinder chasing an oil seep.  I looks like the through bolts can leak through the treads on many engines so I am putting an o ring into the 2 through bolts and remounting the cylinder and will let you all know how this plays out.
Stay tuned for the "Old and the restless quest for Quickie perfection"!
Bruce Crain 

---------- Original Message ----------
From: "One Sky Dog via Groups.Io" <Oneskydog@...>
Subject: Re: [Q-List] Sparrow strainer stall
Date: Fri, 20 Mar 2020 03:55:32 -0700


I found your previous description of stalling the sparrow strainers.
What is the angle between the lower elevator surface and the bottom of the sparrow strainer airfoil?

On Mar 19, 2020, at 7:39 PM, Bruce Crain <jcrain2@...> wrote:

Thanks David, 
For a moment I thought it gave me a bit faster airspeed but the I realized that the air was pretty turbulent and I was having a hard time trimming for straight and level.  I do know that someone said "if you trim the elevator up and compensate level cruise trim with the reflexor you get more airspeed.  I cannot confirm that was the case.  And yes the zig zag did work.  Just made the airplane ride nose high for cruise.

---------- Original Message ----------
From: "David J. Gall" <David@...>
Subject: Re: [Q-List] Sparrow strainer stall
Date: Thu, 19 Mar 2020 12:10:51 -0700


I don’t think the zig-zag tape “created drag” the way you describe it. To me, your description seems like the tape was doing exactly what it was supposed to be doing: keeping the airflow energized and attached. The fact that the now-attached airflow made the elevator “ride up” is exactly what one would expect from an improvement in the air flow over the top of the airfoil; instead of matching the new elevator position with reflexor, you could have accepted the “new normal” and trimmed for it. My bet is that you’ll see similar or identical results with VGs. Was the airplane slower as a result? If so, perhaps that was caused by the nose-high attitude you created when you trimmed the reflexor TE up instead of elevator TE down, and not by “added drag” from the zig-zag tape.
The problem with the sparrow strainer being stalled is that the little beastie is too small and/or too close to the elevator hinge line. This could be fixed in any of several ways, including making it bigger or re-contouring the elevator. 
I wouldn’t count the zig-zag tape as a failure — according to your description, it was eminently successful!
David J. Gall

On Mar 18, 2020, at 6:25 PM, Bruce Crain <jcrain2@...> wrote:

I tried the zig zag tape and did get the stall to go away right up the last test where I finally had all of the zig zag cleaned off.  With the zig zag the stall would not happen on the strainer but it created drag and dragged the strainer up and thus the elevator also.  The elevator would ride up a half inch or so and stay and I would reflex the ailerons up to compensate.
I am going to test actual vortex generators next.  Trying to make them small enough so that they don't  create drag and pull the elevator up.  So the zig zag did work but with less than great results for the trim I am used to seeing.
Before the next tests I am pulling a cylinder to check for a leak around a cylinder base stud or cylinder base o ring perhaps.
Bruce Crain

---------- Original Message ----------
From: "Jon Finley" <jd@...>
Subject: Re: [Q-List] Sparrow strainer stall
Date: Wed, 18 Mar 2020 11:41:07 -0700

Howdy Jay,

I recently heard a woman admit that there are "degrees of yes" - I was stunned. Of course, I was very familiar with this phenomena but had never heard the other gender actually admit to it. Now you are talking about "degrees of stalled" - please confirm your gender!! 


Seriously, I know you are correct. I also saw this in my GU canard tuft testing (moving up/forward on the airfoil). 

Bruce; I don't know what to say on your strainers. I struggled to know how to set them (and eventually gave up on them on my GU, since they weren't needed/per-plans (instead, springs take up the load, as I recall)).  I imagine you have already tried reducing their angle of attack - and noted some change in stick force?? 



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