Re: Need a Sparrow Strainer alternative
Sam,
Your analysis is correct as I recall. Didn’t Gene used to race the QAC Q-200 without sparrow strainers? I thought he removed them for exactly the reason you stated – they are draggy.
I would expect higher stick forces without the strainers. I have no clue if it would induce a flutter situation. As long as the controls are balanced, I would assume not. But it is certainly something that would have to be flight tested.
Having to constantly hold back pressure would indeed put additional strain on the elevator attach mechanisms (including the torque tube to the inside of the elevator). I would think you would want to verify each connection would handle the additional strain because without the strainers that pressure would be constant plus any additional loads as you hit turbulence, etc.
As long as you are asking aerodynamic questions, is the LS-1 airfoil still the best option? I thought John Roncz came up with a new airfoil for the LongEZ canard to address the same issues the LS-1 was trying to address. Of course for all I know, they are the same airfoil!! ;-) I suppose it depends on how much “design” work you want to do and how fast you want to get back into the air!
- Paul
Sent: Wednesday, September 18, 2013 4:15 PM
To: Quickie List
Subject: [Q-LIST] Need a Sparrow Strainer alternative
The Sparrow Strainers are draggy and slow our planes down. There must be an alternative. Every time a speed specialist looks at the the sparrow strainers they go "WTF"?
So, let's start at the beginning. Why are there in the first place?
As I understand it, they are an aerodynamic trim designed to counteract the high pressure on the bottom of the canard elevator. Air wants to push the TE of the elevator up, causing the plane to dive, so the sparrow strainers help by pushing it back down.
Is this logic correct?
So, what would be a drag-free alternative? Well, I suppose one could increase the spring tension already used for the control stick. Why didn't QAC do something like that? Maybe it would increase the stick forces. Just guessing but when they first flew flew the new LS-1 airfoil, they probably found they needed an extraordinary amount of nose up trim. Followed by going with the cheapest fix - add sparrow strainers.
Another issue with using internal trim, is you are applying a constant torque to the joint there the elevator bellcrank slips into the elevator torque tube. Maybe it's not a big deal, bit it's there.
This is all supposition. Is anyone privy to the real story?
So, all of you aerodynamic tinkerers, what could be a viable way to eliminate the sparrow strainers?
Thanks for reading.
Sam