REFLECTOR: old style elevator trim spring

[Scott Derrick]

Doug I had the same problem.  Though I had the curved question mark
shaped fiberglass spring. 

I made a small wooden block that fit between the spring and the
actuator. This in effect adjusted the spring to more up trim and less
down trim.  More Up trim means the plane flies slower in a more up
attitude.  More Up trim means the elevator  moves more down. 

To add more down trim I would have had to reverse the attach point on
the torque tube and possibly add a block there. I didn't need that so
never worked that out.

I don't know if the geometry of our systems are the same so a reversal
of where the blocks need to be placed to effect up or down adjustment
may be needed.  Just look at the  spring/actuator/torque tube while you
adjust trim to see where adding a block will move the trim in the
direction you want.

I had to shave(adjust) the block to get the trim kind-uv where I needed
it.  I didn't have enough trim authority to have enough trim to do both
flight extremes. 
    1.) hands off approach speed with two people up front(max up trim). 
    2.) Hands off fast cruise speed with one person in front(max down trim).

I settled for hands off approach, since I rarely fly that regime with an
autopilot.  In cruise I usually have the autopilot engaged so it can
hold a bit of down trim to maintain altitude if I'm hot dogging it(in a
hurry).

I thought about stiffening up the spring but  after  trying to fly the
airplane with simulated runaway trim down condition, I wasn't sure I
would be able to handle a stiffer spring.  Somebody posted his
experience of having to land with his trim stuck in full down and said
he barely had the strength using both hands..  A scary proposition.

Scott


Douglas Holub wrote:
> I started loading up the front seat yesterday and found I need more
> elevator trim. I've got the straight fiberglass spring. I remember a
> few years ago one of the flyers said he made his out of stainless
> steel and it was working great. If he's still online, do I make it the
> same size as the fiberglass spring, or narrower?
>  
> Doug Holub
> 8.9 hrs of Phase I to go
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