Re: Sparrow strainer stall

Jay Scheevel
 

Hi Bruce,

 

A few years ago, Reg Clarke sent me some video of his tufted canard in flight. He was trying to resolve some elevator vibration he had over certain airspeed ranges and he did videos to figure that out. Here (https://q-list.groups.io/g/main/files/Reg_Clarke_tufted_canard_snapshots.pdf) is a sequence of snaps that I put together from his video at different airspeeds from cruise to pattern to touchdown.

 

I have posted a dashed red line that represents my interpreted forward limit of the separation bubble on  the canard. The tuft behavior on the sparrow strainer will look familiar to you, but you can also see that the separation climbs up the elevator and canard so there is no clean stall break, it stalls gradually, which is a characteristic of a laminar flow airfoil.

 

John Roncz created a canard for the Long-EZ to replace the GU canard which incorporated a slot core that had no bottom on the slot, so when the elevator was deflected down, some of the airflow went up through the slot and over the top of the elevator to help keep the flow connected to the elevator’s upper surface. I am not sure how effective this was, since I am not an EZ guy.

 

Cheers,

Jay

 

From: main@Q-List.groups.io <main@Q-List.groups.io> On Behalf Of Bruce Crain
Sent: Wednesday, March 18, 2020 9:02 AM
To: main@Q-List.groups.io
Subject: Re: [Q-List] Sparrow strainer stall

 

Hi Jon!

No the canard isn't stalled but it looks like the elevator is stalled.  The tufts are gyrating in circular motion on the elevator right in front of the sparrow strainer and also in the outboard end of the elevator.  It would be interesting to see if every Quickie had the same scenario with respect to the elevator.  I had suspicion-ed that in the past when I flew through the rain.  The dust mixed with the rain and made trails from out board to inboard.

 

We could be loosing lift in this area but how to correct it?  The elevator slot core is pretty tight so I am not sure a seal is possible.  Also, perhaps an air dam on the outboard end of the elevator could be possible.  If lift is re-attached to the top of the elevator would the sparrow strainer need to be augmented to keep it level in flight?  There would be a lot more up lift in the elevator if re attachment were possible.

 

Could we be loosing airspeed!!!  OMGosh!  Somebody fix it!!  Any aerodynamicists in the room?!!

 

Bruce Crain


---------- Original Message ----------
From: "Jon Finley" <jd@...>
To: main@Q-List.groups.io
Subject: Re: [Q-List] Sparrow strainer stall
Date: Tue, 17 Mar 2020 13:00:41 -0700

Sorry Bruce... I just saw this.

It's hard to see from the photo - are the tufts on the canard also stalled??

Jon

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