REFLECTOR: Sparrow strainer - I'm confused...

Andrew Ellzey ajlz72756 at yahoo.com
Tue Sep 18 09:21:41 CDT 2012


Geoff,
 
Cutting the Sparrow Strainer off and reattaching it at a different angle seems a bit harsh. I made my SS adjustable by potting a 10X32 nut plate inside each end of the airfoil. So the Airfoil is then held in place on by two 10X32 screws. I am not flying yet, so I don't know if my aircraft even needs an adjustable SS. But from all of the talk of trim problems on the reflector, over the years, I thought that I would be proactive and make my SS adjustable. I will install mine per the manual, but if needed, I can change the angle of attack or even invert my SS airfoil as some have suggested. I also think with a little trial and error, I should be able to adjust the SS depending on my aircraft CG calculations, due to passenger loading. This may be wishful thinking on my part, due to the small size of the Sparrow Strainer. I can send you a photo latter today if you think this option will work for you.


>________________________________
> From: Geoff Gerhardt <geoff.gerhardt at gmail.com>
>To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org> 
>Sent: Saturday, September 15, 2012 7:45 PM
>Subject: Re: REFLECTOR: Sparrow strainer - I'm confused...
>  
>
>Guys,
>
>
>Thanks for all the suggestions.  What I think I may do is cut the arms that join the SS to the elevator and then re-connect them with the SS airfoil at a lower angle of attack to reduce the speed-induced up-trim. 
>
>
>Today, I had a great flight.  I made some changes to my cooling plenums that reduced temps in cylinder #3 (I'll describe these changes in another email), so I was able to do a pretty aggressive climb to 10,000'.  I was going to do flutter testing, but when I dove to gather speed, I found that too much stick pressure was req'd to go above 180kts to properly assess flutter.  I could not trim it so that I could take my hand off to give the stick a whack because I had to keep down pressure to stop from climbing out of the dive.  All control surfaces were fine to 180kias, but I think I'll need to address the aerodynamic trim to go higher.  Or, is it okay to have stick pressure on when doing flutter testing? 
>
>
>Geoff
>
>
>On Sat, Sep 15, 2012 at 11:20 AM, Terrence Miles <terrence_miles at hotmail.com> wrote:
>
>Geoff, 
>>Over the past 10 years or so, the sparrow strainer debates  and opinions (which are always fascinating to me) and the “running out of trim” issue come up on a regular basis.  Geoff, you are hardly the first in the test flight phase to wrestle with this.  I have the RGXL-5 with a LY IO540.  I weigh 150 pounds.  Empty wgt she is 1928 lbs at 136.4   I know other light weight pilots like me that fly with ballast on the floor by the right seat.  I don’t because I have two nose mounted Odyssey batteries.  XC by myself with 70 gal of fuel and the usual crap in the back seat area (125+ lbs) I am at a CG of 130ish.  With a 185 lb copilot it goes to 128.3 or so if anybody out there is considering 2 nose batts be aware of that limit.   Because I am short I have the arm of my seat is 79 inches.  The copilot is at 83 inches. 
>> 
>>I am not suggesting this for others, but with advice like you are seeking right now, and more than several conversations with Malcolm Collier and others, I decided to do this:  The factory trim spring didn’t fit due to insufficient space behind the panel without major changes.   Also the stock elevator trim motor throw was too short.  I have a speed brake trim motor running my elevator trim which is longer by an inch or two.  Yes, I have to watch for fractures in my sawed off, reduced curve spring, but  I don’t run out of trim no matter wgt, CG, or speed.   
>> 
>>Terry 
>> 
>>From:reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On Behalf Of Richard J. Gentil
>>Sent: Friday, September 14, 2012 10:31 PM
>>To: geoff.gerhardt at gmail.com; Velocity Aircraft Owners and Builders list
>>
>>Subject: Re: REFLECTOR: Sparrow strainer - I'm confused...
>> 
>>Geoff,
>> 
>>To help solve the issue I just cut my sparrow strainer in half. 
>> 
>>Richard 
>>
>>Sent from my iPhone 4 Classic
>>
>>On Sep 14, 2012, at 10:01 AM, Geoff Gerhardt <geoff.gerhardt at gmail.com> wrote: 
>>Guys,
>>> 
>>>As I'm flying more, I'm getting a better feel for the plane and discovering little issues.  I noticed yesterday that when I really dangle (i.e. >160kts), I run out of down trim.  I guess I wasn't paying attention before, but as I speed up, I need to keep adding down trim - I thought that's what the sparrow strainer was for.  As speed increases, the canard is generating more lift, so the sparrow strainer trims the nose down so that less trimming is needed for speed changes.  But then, I was looking at the way the sparrow strainer is mounted and it looks like it would do just the opposite.  As speed increases, the sparrow strainer will be pushed down, adding trim up!  I have my aerodynamic trim installed as per factory instructions.  I've heard of some who install it upside down, which to me sounds like how it should be installed.  I have a feeling that if I remove it I'd have to trim less with speed changes.  Unfortunately, I used some pretty
 aggressive silicone glue to put it on and I'm afraid I'll make a mess of it taking it off. 
>>> 
>>>Any thoughts on the effectiveness/correct installation of aerodynamic trim?
>>>  
>>>Here's now I have mine installed:
>>>http://thegerhardts.com/velocity/?p=491 
>>> 
>>>Geoff
>>> 
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> 
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>
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