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In
airplanes with tricycle landing gears it’s fairly easy to control the
straightness of take off with the front wheel and rudder. During
takeoff, you guide the airplane with the front wheel down the runway until
the speed gets to about 10-20 mph, and then the rudder takes over and
guides the airplane the rest of the way—hopefully straight down the
runway to a smooth takeoff. Other
factors that affect takeoffs are obviously the pilot, wind direction, and
model dynamics.
Toe-in
is when the front wheels are slightly angled inward.
Typically 1 or 2 of toe-in will do the trick.
Tail-dragger
airplanes are slightly different animals and require a little toe-in in
order to guide the airplane down the runway as straight as possible during
takeoff and landing. Front
wheel toe-in plays a very important
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role, much more so than
in an airplane with tricycle landing gear.
An
airplane with tricycle gear’s center of gravity (CG) is in front of the
main gear. This helps
straighten out an airplane that has developed a yaw angle between where it
is pointed and where it is actually going.
A
tail dragger’s CG is behind the main gear, and a slight yaw angle is not
automatically corrected but is made worse and can result in ground
looping.
Toe-in of the wheels can help both types of
airplane. A model rolling
straight ahead has equal drag from each of the wheels. When
the airplane takes an unwanted turn to the left, the drag from the left
wheel is reduced to near zero, while the drag at the right wheel
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increases. The
net effect is an unbalanced drag on the wheels. This
exerts a retarding force and tends to turn the airplane back to the
desired direction. This
wouldn’t happen without toe-in.
A slight toe-in on float models also works
well for maintaining a straight takeoff into the wind. The
most important thing I’ve learned about float flying is to keep the
airplane directed straight into the wind during takeoff and landing.
By Ron Scott
Alan Hoff, editor
Simi
Valley
Flyers,
Simi
Valley
CA
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