Toe-in or toe-out?

[Geoff S]

If a model with a tail-dragger configuration swings right on its take-off run weight transfers from the RH leg and onto the LH one. In fact the RH wheel can lift completely from the ground and all the weight is on the LH wheel. If there is toe-in, the LH wheel is already pointing right and will tend to increase the swing rather than correct it. However, if it's pointing out (ie left) it will tend to correct the swing. The same effect in reverse would work if the model swings left, as is more common.

Most people seem to suggest that wheel toe-in is the preferred option which is the reverse of what I reasoned above. Where is the fault in my reasoning?

Geoff

Edited By Geoff Sleath on 01/02/2018 21:45:27

[Chris Walby]

Which way does the wheel deflect when load is applied? Could be a bit like front wheel cars vs rear wheel drive and the difference between toe out and toe in?

PS there was something on RCM & E about this and the benefits of tricycle U/C not self propagating the turning effect.

Only a thought

[Denis Watkins]

From another angle Geoff, in the name of landing and "touch and goes "

I prefer to leave toe in at zero

They do say that toe out cures your problem partially

But then, any touch down may involve resistance that you don't want, ie nose tipping

Progressive throttle usually works for me, applying more power as the model lightens on the u/c

Edited By Denis Watkins on 01/02/2018 22:06:50

[Levanter]

Geoff

​I had the same conundrum not so long ago when I was assembling a model I had just built and I saw that one wheel was point dead straight and the other with a marked toe-in. I came to the same conclusion as you that toe in was undesirable, dead straight was probably OK and toe-in might have some advantages. I wasn't thinking about take-off however but the landing.

​If an aircraft lands on one wheel before the other (most of the time I would think) it will be slightly or maybe very banked. A toe-in wheel touching first would tend to trip the aircraft up and increase the bank angle. A toe-out wheel would try to get the aircraft back under the wings and bring the opposite wheel down sooner. When they are both on the ground - well hey! you've landed.

​I think I remember the article you refer to Chris and I think it was more to do with the position of the centre of gravity in relation to the main wheels. Forward on the trike and aft on the tail dragger so when a swings begins the mass of the aircraft acting behind the wheels compounds the swing sometimes quite viciously.

Levanter

[Stuphedd]

This subject was a Thread on the "other " forum many years ago , The answer is

Real planes have Toe Out , apparently ! It took me by surprise as I always set just a tad of Toe In on my sport cars

I never raced a plane !!

Look it up !

[Stuphedd]

This may help

http://www.modelflying.co.uk/forums/postings.asp?th=133538#2296867

[Martin Harris - Moderator]

I was just looking for this old thread from 2009 while you were posting, Pete - was that what you were referring to? (Your link doesn't work for me).

BEB's posting on page 2 gives a very good explanation.

Edited By Martin Harris on 01/02/2018 22:41:19

[Geoff S]

Posted by Pete Willbourn on 01/02/2018 22:22:56:

This subject was a Thread on the "other " forum many years ago , The answer is

Real planes have Toe Out , apparently ! It took me by surprise as I always set just a tad of Toe In on my sport cars

I never raced a plane !!

Look it up !

Well, yes. I was at one time something of an expert at setting up motor bike and sport sidecars using clothes props as guides! I usually set thesidecar wheel to toe in about an inch when measured at the bike's front wheel compared to the rear and about 1.5" lean out for easy steering. But undercarriages are something different, I think

Perhaps neutral is the one to go for (ie neither toed in nor out) but as that's difficult to achieve perhaps a touch of toe out is preferable.

Geoff

[NormB]

**LINK** gives good reason why toe-out is needed on full-size taildraggers.

Seems convincing to me...

[Paul C.]

I always try for a neutral setting but generally after my first landing things change significantly , never really notice any changes in ground handling even after my forced changes. Perhaps it's because I fly off grass , tarmac may change make toe in out more critical.

Paul.

[Philflyer]

NormB. Many thanks for the link. 3 years ago I built a Mamselle 52 from the RCM&E free plan (June 2003) and, although a beautiful design (see my album), it is a beast on take-off and landing. Ground loops more often than not. I should mention that our club has a tarmac runway only and, in the interests of safety, a model must be steerable and taxi to and from the pilot area, so the Mamselle has a steerable tailwheel built into the sub-fin. Despite this benefit the ground loop is so rapid the steering is ineffective once the power comes on full. Toe out looks like the answer.

Edited By Philflyer on 02/02/2018 08:40:02