Model Forum / General / Rockets / October 2004

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What sort of G engine do you have in mind?

I could post a plan for my "Moonraker" model that was designed to boost on an
F13 or a G12 32mm "R/C" Reload. Put a G40 in it and you might as well have
bought a bunch of fireworks to set off all at once - they'd be more impressive
and what's left would be about as re-useable as that glider would be on a G40.
That model would not hold up to a G25 eithe,r it was designed for boosting on a
G12 but it turned out a bit heavy, and a bit strong, so a few times I flew it
on a G12 clustered with an E16 for a net "G18" (that was nice, but not the time
when the E6 lit but the G12 did not light).

The Moonraker looks like the model shown lifting off in this photo:

http://members.aol.com/GCGassaway/RC/Bigbird_boost.JPG

Or you could look into buying an old Aerotech "Phoenix", which was designed for
aerobatics and is somewhat stronger. I do not recall if it's exactly strong
enough for a G40 though (it would be very hot on boost, requiring extremely
good trim and pilot control. IIRC Bob Parks flew one on a G40 but I don't
recall if he built that one extra-strong or if it was standard assembly). It
would hold up fine on a G25 which would boost it very nicely (Was designed to
boost on the G12, F16, and F23 32mm RC reloads).

There's a photo of a Phoenix plus some other models on this page:

http://members.aol.com/GCGassaway/rcgliders.htm

Anyway, Rocket Boosted Gliders are a lot more sensitive to what engines they
fly on than regular rockets. High performance gliders are built lightly and use
low thrust long burning engines to reduce the stress loads on the wings as well
as the rest of the model. If the model is intended to fly on a higher thrust
engine, the model has to be designed and built strong enough to be able to take
the increased stresses. Aerodynamic loads increase with the square of the
velocity, so a glider that boosts twice as fast will have four times the
stresses on it.

When they are not designed or built right, or just plain have an engine with
too high of a thrust inside of them, they'll do something bad, usually
shredding the wings. Or sometimes other things like shredding the tail or
flexing the fuselage (particularly fiberglass/graphite tailboom types) to the
point that they want to tuck nose-down and full up elevator won't bring them
back under control. Or in rare cases,  boosting so fast that the servos are
overloaded and stall, allowing the model to get out of control on boost (that
crops up when servos are too small/weak for the particular type of model being
flown, given the model's size,  weight,  and likely max boost velocity).

- George Gassaway

A NIRA member built a 150% upscale of John Kallend's Ladyhawk that he flys
on two G motors. I think a 200% version would handle H motors (Chris Taylor
take note) and be WAY cool!

    Bob Kaplow    NAR # 18L    TRA # "Impeach the TRA BoD"
        >>> To reply, remove the TRABoD! <<<
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