Taildragger....... Toe-in vs Toe-out and tire wear

[builderflyer]

Back about 11 years ago I took some measurements to determine the "working" toe-in on my taildragger Sonex.......but not in the usual way (i.e. with the aircraft leveled and no weight on the wheels) but rather with weight on the wheels and first with the aircraft leveled and then with the aircraft in the 3 point stance. Because of surface friction, i made it a point to roll the aircraft forward prior to taking each measurement as it will change a bit from the measurement obtained if the aircraft had been just rolled backwards. Obviously, the measurements only apply to operating on a paved surface.

What I found was that with the tail up, the wheels (tires) were in a measurable toe-out situation and with the tail down, the wheels (tires) were in a measurable toe-in situation. So I would deduce that somewhere between the tail being full up and full down, there would be a point that the wheels (tires) would exhibit a zero toe-in situation.

Why do I mention the above........because even on the exact same aircraft and disregarding the obvious, an individual's piloting technique could help determine tire wear patterns. That is to say, disregarding "camber", the typical vertical position of the tail on take-offs and landings can help determine the observed tire wear pattern. Does the pilot always make take-offs from the 3 point stance or does he raise the tail high or somewhere in between? Does he usually make wheel landings or 3 point landings? The typical length (and perhaps speed) of taxiing to and from the runway also could play a significant part in observed tire wear.

My overall point in stating the above is that simply setting the toe-in to 0.7 degrees as shown on the plans for a taildragger Sonex is more complex in actual operation than it may first appear. Has anyone else made the above measurements or can anyone else confirm or deny my observations? Or doesn't anyone else have too much time on their hands?

Art,,,,,,,,,,,,,,,Sonex taildragger #95,,,,,,,,,,,,,,,,,,Jab3300 #261

[kmacht]

I believe that you are overthinking this. Set the toe to plans and you won't have any issues. Tire wear has not been a documented issue with the Sonex airframe. If you do end up wearing a tire out they are only $37 each from the sonex store. You could replace them every year during the condition inspection for that price if you wanted.

To answer your question on takeoffs and landings with a taildragger, almost all of mine have been 3 point. That is what Sonex taught during transition training. There is no reason you can't do a wheel takeoff or landing in a sonex though. I know some people prefer them. In a 3 point takeoff the time between when the tail lifts up and the main gear lifts off is so short I'm not sure it would make any discernible difference in tire wear.

Keith

[airscribe]

Art, your info on checking the variables went right into the building-notes folder for my Waiex....thanks...

And with so very many variables -- the builders the biggest ones -- don't think it hurts much to put a little extra study and thinking into the more complex steps....onward and upward from Sun 'n Fun....plan to visit with our friends from Oshkosh the first chance that comes my way....