REFLECTOR: Elevator Trim Spring

Thu Feb 2 01:23:09 CST 2006

Don't forget Scott that the sparrow trim also has to fight the trim 
spring...  So, I use a light trim spring and have a very soft elevator 
control force up to my top speed of about 170 knots...  My elevator is 
pointing up (down elevator) about 5/8 of an inch at 170 knots...

Best... Steve

----Original Message Follows----
From: Scott Derrick <scott at tnstaafl.net>
Reply-To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
Subject: Re: REFLECTOR: Elevator Trim Spring
Date: Wed, 01 Feb 2006 11:27:14 -0700

Steve,

I have the strainer installed.  I've flown with and with out.

The strainer seems to reduce the frequency of trim change needed as you 
change airspeed.

On my plane it certainly doesn't "take care" of trim in cruise.

Its installed per the plans, but that doesn't mean its set right.

My take on the matter is the faster the plane, or in other words, the 
greater the range of speed between top end cruise and stall, the greater the 
range of trim required.

With my last engine I stalled around 65 KIAS, and cruised at 175 KIAS(sea 
level).   So, maybe the folks that are having a hard time getting enough up 
and down trim are the faster planes?  Or lighter pilots?

Scott

steve korney wrote:
>
>Guys.....
>
>The sparrow strainer takes care of the trim in cruise and top speed...  If 
>it's set right...
>
>
>Best... Steve
>
>
>
>----Original Message Follows----
>From: Scott Derrick <scott at tnstaafl.net>
>Reply-To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
>To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
>Subject: Re: REFLECTOR: Elevator Trim Spring
>Date: Wed, 01 Feb 2006 08:08:24 -0700
>
>I can see how he might need more travel.
>
>As my trim is set up, I have just enough down trim to cruise at 65% power 
>with just me in the front. If its bumpy I don't have enough, I have to 
>constantly give it a shove forward  or use George. If have two in the front 
>I don't have enough up trim for a hands off 90 knot approach, just me its 
>fine.    If I fix it so I can fly a 90 knot approach hands off with two, 
>I'd loose my  hands off cruise trim setting.
>
>So as Scott B. said, I could possibly stiffen up the spring, I don't like 
>this option because  I think it would be hard enough trying to fly it with 
>an inoperative trim system as it is, any stiffer and I'd be out of muscle 
>pretty fast.   Or I could use a trim actuator with more travel. I had not 
>considered that  and will have to think about it.
>
>However I do like the design of the Strong Pitch Trim system and would 
>welcome the added space behind the panel if I removed the fiberglass spring 
>trim system.  Strong now has a PWM controller for his trim system for fine 
>pitch adjustments at fast speeds. A problem I partially solved on the 
>original system with a electric brake.
>
>Scott
>
>
>
>Ron Brown wrote:
>>John,
>>
>>I don't think you will need more travel if you use the unmodified factory 
>>? shaped spring installed per the manual
>>
>>You'll just need to adjust its location to get the amount of up and down 
>>trim needed for your plane.
>>
>>Ronnie
>>
>>
>>
>>----- Original Message ----- From: "John Dibble" <aminetech at bluefrog.com>
>>To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
>>Sent: Tuesday, January 31, 2006 6:56 PM
>>Subject: Re: REFLECTOR: Elevator Trim Spring
>>
>>
>>>Where can I get an actuator with more travel?
>>>
>>>John
>>>
>>>Scott Baker wrote:
>>>
>>>>While its interesting to think about the benefits of variable geometric
>>>>wings, canards, and winglets - lets remember the practical elements of
>>>>system design as it applies to weight, complexity of design and 
>>>>maintenance,
>>>>and of course cost.  The Beech Starship had a base list price of $3.9M 
>>>>when
>>>>it was introduced in 1989.  There are lots of cool things that would be 
>>>>fun
>>>>to try - given relief from $$ constraints.  The subject of pitch-trim 
>>>>has
>>>>been discussed on the Reflector off and on in the past.  The basic 
>>>>linear
>>>>actuator/fiberglass spring system works well to my liking.  I happen to
>>>>think it is one of the finer flying attributes of the Velocity.  If an
>>>>aircraft does not have enough pitch trim (in cruise or in slow flight) 
>>>>the
>>>>answer in most instances is to re-mount (adjust the location) of the 
>>>>linear
>>>>actuator so that it gives the needed travel.  Sometimes the fiberglass
>>>>spring needs stiffening - this can be done by adding a few plies of 
>>>>glass -
>>>>or replacing the spring with a new one from the factory.  A few builders
>>>>have installed linear actuators with an additional inch of travel (in 
>>>>order
>>>>to get enough up _and_ down trim).
>>>>Scott Baker
>>>>
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>>
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