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

[Geoff Gerhardt]

Guys,

Wow, lots of great info in this thread - I am now somewhat less confused.
 Originally, I thought the purpose of the SS was to allow the Velocity to
self-trim (i.e. at higher speeds, elevator up force would be applied to
keep the nose down), but I now understand that it is meant to add pitch
stability (i.e. when a pitch disturbance was induced, it should
re-establish pitch stability within 1.5 oscillations).  The issue I've had
is that at high speed, the SS adds quite a lot of nose-up trim, so much so
that I pretty much run out of trim at ~165kts.  Making it adjustable looks
like the best option.  I think I'll cut mine off and try flying without it.
 If I get poor pitch stability, I'll make it adjustable and put it back on.
 I suspect it'll stay off even if my pitch stability is reduced - I use AP
almost always when cruising, so maintaining rock-solid pitch stability is
not critical for me - let the AP do all the work!

Geoff

These last few posts make me want to take mine off and try it without.  I
have good pitch stability now, tho - I don't want to use that.  On the
other hand, during the 17hrs of testing I've done so far, when I'm just
cruising at altitude, the AP is usually doing all the work, so perfect
pitch stability is maybe not so important.

On Sun, Sep 23, 2012 at 12:20 AM, Darrell & Nora Kufalk <kufalk at wi.rr.com>wrote:

> I have an XL-RG with 270 hours and I installed the trim system per the
> manual.  I built the sparrow strainer but never put it on.  My trim system
> works perfectly without it.  I never come close to running out of trim in
> either direction at any speed at any CG.****
>
> ** **
>
> Darrell****
>
> N207DK****
>
> ** **
>
> ** **
>
> *From:* reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] *On
> Behalf Of *Glenn Babcock
> *Sent:* Saturday, September 22, 2012 10:13 PM
>
> *To:* Velocity Aircraft Owners and Builders list
> *Subject:* Re: REFLECTOR: Sparrow strainer - I'm confused...****
>
> ** **
>
> I have a Standard Elite RG, factory trim and no sparrow strainer, no
> problems at all.  I have flow at both extremes of CG and had enough trim.
> In a high speed decent single pilot I may hit the limit but its right at
> 200 kts. I even decreased the stiffness of the spring to make the trim less
> sensitive.
>
> Regards,****
>
> ** **
>
> Glenn****
>
> N697RG****
>
> ** **
>
>
> On Sep 22, 2012, at 11:02 PM, Tim Rhodenbaugh <timrhod at aol.com> wrote:****
>
> Has anyone tried not using the sparrow strainer?  I have an XLRG with over
> 200 hrs  I never got around to putting mine on.  I have more than enough
> trim in either direction.  Stability is good in all configurations.   Tim
> Rhodenbaugh n370TR.
>
> Sent from my iPad****
>
>
> On Sep 22, 2012, at 9:43 PM, "Paula and John Schoorl" <
> pjschoorl at verizon.net> wrote:****
>
> We installed the factory trim system with no modifications and installed
> the sparrow strainer per the plans (airfoil down) and have never noticed
> running out of trim or had to make adjustments.****
>
>  ****
>
> We have an XL-FG with 750 hours****
>
>  ****
>
> John Schoorl****
>
>  ****
> ------------------------------
>
> *From:* reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org<reflector-bounces at tvbf.org>]
> *On Behalf Of *Scott Derrick
> *Sent:* Friday, September 14, 2012 8:19 AM
> *To:* Velocity Aircraft Owners and Builders list
> *Subject:* Re: REFLECTOR: Sparrow strainer - I'm confused...****
>
>  ****
>
> While agree with John in theory.....
>
> The elevator trim system is like the nose wheel shimmy damper, its barely
> adequate, though the factory will never admit it is anything but fine.
> Yeah, normally if you keep the nose wheel tension within a reasonable
> range, which makes taxiing a bitch, it works.  but let it get a bit out of
> that range or have some other mysterious contributing factor and it will
> bite you and can bite really hard! You will now notice the factory is
> selling a nose trim system designed and initially built by one of our
> members here on the reflector.  It's priced in the range of a certified
> airplane shimmy damper, but it appears to solve the nose gear destroying
> inadequacy of the standard shimmy damper.
>
> The standard elevator trim system is the same,  get it shimmed up and it
> works OK(barely adequate for some, POS for others).  You can get it(shim)
> to trim hands off in a max trim up condition(approach speed, max forward
> cg) but then you aren't even close to  max trim down condition(aft cg, max
> cruise speed), or you can go the other way.  And thats  with the sparrow
> strainer installed in a standard configuration.  Most shim it somewhere in
> the middle, not really good enough for either max up or max down condition.
>
> I've never heard of any "builder" getting the trim to work properly
> without installing the SS upside down, or increasing the stiffness of the
> spring. The problem with increasing the stiffness is having a trim
> malfunction.  With a stiffer spring I question any body's ability except
> maybe a weight lifter, of having the strength to over come a full down trim
> position, fly to a near airport and land the plane.  Somebody on the
> reflector had to do that with a standard spring and as I recall, he said he
> wasn't sure his arm strength was going to last long enough  to get it on
> the ground and I believe the trim malfunction happened in the pattern!
>
> Just try it sometime.  In flight simulate a trim malfunction. Trim full
> down and then fly the pattern and attempt a landing!  Do this at altitude!!!
>
> I'd be glad to hear from any builder that has solved the elevator trim
> problem with the sparrow strained in the normal position and not by
> increasing the spring stiffness?
>
> Scott****
>
> -------- Original Message --------
> Subject: Re: REFLECTOR: Sparrow strainer - I'm confused...
> From: John Abraham <john at velocityaircraft.com> <john at velocityaircraft.com>
> To: geoff.gerhardt at gmail.com, 'Velocity Aircraft Owners and Builders
> list' <reflector at tvbf.org> <reflector at tvbf.org>
> Date: 09/14/2012 08:42 AM****
>
> Geoff,****
>
>  ****
>
> Just the opposite.  The sparrow strainer is there to aid your trim
> system.  Since a trim system is to maintain airspeed you have to trim down
> as you accelerate or the plane will climb.  Installing it upside down will
> work to make the elevator “trim” itself, but will prevent your trim system
> from being stable.  Your pitch should be 1.5 oscillations with a 10kts
> disturbance, which is pretty good compared to other aircraft.  If you run
> out of trim nose down you need to space out your trim spring down on the V
> bracket on the concentric torque tube.  Nose up trim would be at the trim
> motor and spring bracket.  ****
>
>  ****
>
> Other things to consider are the stiffness of your trim spring, if it was
> ever weakened or cut down it won’t hold trim very well at high or low
> speeds due to air loads.  You can replace it with a stiffer spring if you
> want to which will also help out.  I have seen some builders narrow their
> spring due to clearance issues but you looks some stiffness as a result.
> Also, look at the top of the trim spring for stress cracks.  Always try to
> be close to neutral trim when doing your run up and box check so you don’t
> over stress the spring.****
>
>  ****
>
> Safe flying,****
>
>  ****
>
>                       John Abraham****
>
> Chief Pilot, Executive V.P. Sales and Marketing****
>
>          <image001.jpg>****
>
>                   200 W. Airport Drive****
>
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>
>             www.velocityaircraft.com****
>
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>
>  ****
>
> *From:* reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org<reflector-bounces at tvbf.org>]
> *On Behalf Of *Geoff Gerhardt
> *Sent:* Friday, September 14, 2012 10:02 AM
> *To:* Velocity Aircraft Owners and Builders list
> *Subject:* REFLECTOR: Sparrow strainer - I'm confused...****
>
>  ****
>
> 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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