When I am launching the Spectre 120 - with the recommended control surface travel and cg as in the instructions - I
am getting little or no response to v-tail control inputs to keep the plane on
a straight launch path I have to use the right stick/aileron control to turn the plane!
The plane does respond to left-stick controls in cruise and landing
modes, and the tail surfaces do make the complete movements in launch mode on
the ground (I presume they are also moving in flight). What could be causing
this?
From : Don Stackhouse
You didn't mention which servos you're using for the ruddervators. I'm
guessing either wimpy servos (and in our experience there can be
significant variations in that from one servo to the next, even with the
top-dollar ones), or you don't have the pushrod guide tubes tied down well
enough, allowing some flex in the linkage. Another possibility is having
too sharp of a bend in the guide tubes (the section under the wing is a
prime candidate for this problem), causing binding that steals too much of
the available servo power. The loads on the ruddervators during launch are
HUGE, so a problem in any of the above will usually show up there, but
might not be as much of an issue in the other modes of flight.
Otherwise, the plane flies beautifully, although I intend to install
an alignment pin between the wings, as the plane is very sensitive to even a
slight incidence misalignment (caused if the rear wing mount bolts are not
tightened absolutely equally).
That can certainly be a problem, and an alignment pin is an easy fix. The
other thing that affects this is the fit between the underside of the wing
and the saddle on the fuselage. Bedding the wing into the saddle with RTV
silicone may also help. Smooth a piece of plastic wrap over the underside
of the wing center section, put masking tape on the sides of the fuselage
just below the edge of the wing saddle, and at the leading and trailing
edges. Lay a bead of RTV along the edges of the wing saddle at the leading
edge, trailing edges and along both sides. Bolt the wing onto the fuselage
with the bolts snug but not quite as tight as you normally do for flying,
wipe off the excess RTV that squeezes out, then pull off the masking tape
while the RTV is still wet. Let cure for several days, then remove the
wing, peel off the plastic wrap and trim off any remaining stray lumps of
RTV. This will seal the wing/fuselage juncture, and also give the wing a
more consistent bed to sit on.
I did install McCann nose skid and fuselage
skeg, more to keep the flaps clear when landing than for landing control
otherwisw the model is completely to your plans.
The nose skid is definitely a plus for competition. The big skeg keeps the
flaps off the ground and also shifts the contact force forward during the
landing slide, but the nose skid is what provides most of the stopping
power. Joe Hahn proved that at the Nats this summer. All through the first
day of open class he was within a handful of points of the leader Daryl
Perkins, pretty remarkable considering that Joe still regards himself as
relatively inexperienced in open class competition. Then, in the last round
of that day, he slid just the TINIEST fraction of an inch too far (they had
to call an official over to make the determination), putting the tip of the
nose just barely over the safety line in the end of the zone. What would
have been a 100 point landing that would have put Joe in first place
suddenly became zero points, putting him out of the running. With a nose
skid, the final standings at the 2006 Nats could have been significantly
different.
Don Stackhouse
DJ Aerotech
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