REFLECTOR: Sparrow strainer - I'm confused...
Geoff Gerhardt
geoff.gerhardt at gmail.com
Fri Sep 14 11:17:15 CDT 2012
John/Scott,
Thanks. I'm using the Strong Pitch Trim system - I can bias it to give
more down pitch, if needed (but, I suspect that will give me inadequate up
pitch trim).
I'll leave my system as it is now and fly it more before deciding how to
adjust it.
I'm starting to learn that its better to fly more and better characterize
an issue before reacting quickly to a perceived problem by making changes
to the plane.
Still battling high CHT's in #3, but I think I have the problem understood
now and will be making some plenum changes tonight that I hope to try this
weekend.
Geoff
On Fri, Sep 14, 2012 at 11:18 AM, Scott Derrick <scott at tnstaafl.net> wrote:
> 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****
>
> [image: Description: 4103]****
>
> 200 W. Airport Drive****
>
> Sebastian, FL 32958****
>
> www.velocityaircraft.com****
>
> (P): 772-589-1860****
>
> (F): 772-589-1893****
>
> ** **
>
> *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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>
>
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