On 14 Nov 2003 10:07:59 -0800, (Joa) wrote:

OK, I've researched this a fair bit and am still hearing two definite
different views. One one hand you have those that swear you need
toe-out and then on the other you have (among others- these are the
few I'm certain about) Cessna 100 series, Huskies, and Pitt's that all
are set with slight toe-in by the factory. Granted these are set
without weight on the aircraft and the toe-in may change slightly when
under load.

I think it boils down to what wins when you start to go into a turn
with a taildragger- does the toed-in outside wheel "drag" and thus
want to straighten you back out or does the toed-out outside wheel get
weight transferred to it and tend to straighten you out (vs tightening
the turn)?

Anybody with some definite answers based on physics? There's lots of
emperical and experiential opinions out there, anybody with some more
factual answers to the argument?

J oa

this has been done to death with adherents in both camps who may not
have ever flown taildraggers.

I fly a Wittman W8 Tailwind. (about 220 hours now)

my experience is that the geometry of the undercart does not correct
for groundloop tendency. it's influences in the forces at play are
fairly minor, HOWEVER having slight toe out is buckets better than
slight toe in because in the swerve of an impending groundloop the
inertia of the aircraft will lift all the weight off of the inboard
wheel (so it doesnt matter where it points really) and will place all
the weight on the outboard (outer edge of the turn) wheel. in this
condition slight toe out will have the wheel pointing in the direction
of forward travel and so it will not be working against your efforts
with rudder to straighten out the aircraft. toe in would provide just
that little bit more of a tendency to groundloop that you need to
overcome with rudder force.

now the order of toe out on my tailwind is not extreme.
in tail up takeoff position with the full aircraft weight on the
axles, ( the aircraft sitting with the bare axles on pine boards and
the fuselage level, ie without the 5.00x5 wheels on) the axles are
slightly lower at the outer end than the inner (about 5mm) and are
slightly more aft at the outer end than the inner end (again about
5mm).

while that setup works ok with the tailwind and it's taper spring legs
you might want to look closely at other aircraft with similar gear
geometries to what you are interested in before deciding.
I've been told that the RV6 has interesting gear behaviour under
deflection which is different from the tailwind.
Stealth Pilot