I was suggesting was that the method per manual of drilling the
plastic spacers is prone to enlarge the holes. That causes play, and
with smaller contact area of pin against tubes, high G-loads
concentrate greater stress so as to make them larger - more slop. I
have no experience there, as I didn't to do it their way. Suggest
making the holes (especially second one) by enlarging smaller ones
through trial and error, not drilling through the holes at TP12.
With assured tight fit, the rest I think is academic. The tailplane
is always statically balanced, but I was picturing loads under high-G
acceleration. If you balance a 10' length of 1" PVC pipe in your
hand, and rapidly push upward, what happens at the ends? On the
tailplane, the opposing loads are concentrated at the torque tube,
where the concentric tubes attempt to turn in opposition and bear on
the pins. The only two adverse situations in normal flight I vote for
are hard landings and really bad jolts in turbulence; other loads you
describe I'd guess are on the mild side. Redesigning the mass balance
would help for acro. With the long balance arm, pull high G's on the
stick, and the pins get a real inertial whack when the weight "catches
up" to where you yanked the stick back. Anybody snap rolled one yet?
:-)
Regards,
Fred F.
bizzarro@easynet.co.uk wrote:
>
> Okay, so I am getting a little concerned now. If what I hear is
> correct, the inflight loads on the tail planes is not enough force to
> cause the the elongation of the holes in the TP12. That would make
> sense. So the primary cause is probably the fact the tail planes are
> not balanced with relation to the tube position (hence the large mass
> balance), and as a result, the vibration of running over rough ground
> and engine/prop inbalance causes the tail planes to shake up and down.
> This would cause large forces on the pin hole positions on TP12
> causing elongation.
>
> Would the act if decreasing the weight in the mass balance, and
> inserting lead into the leading edge of the tail planes to retain the
> balance not cure this problem. If the tail plane was more balanced
> within itself, the forces on the pins would surely be decreased. I
> know that this would add overall weight as the moment arm within the
> limits of the tail plane is shorter than the mass balance but
> hopefully it would improve the situation. Perhaps?
>
> Any thoughts
>
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