I left my trainer in the basement for about half a year and it appears the rudder has leaned slightly. It is between an eighth and a sixteenth of an inch off center at the top. Will this affect flight characteristics?

You can straighten it out by hand, and re-shrink the covering to fix it. The covering will hold it in place.

Being a trainer I don't know how much you'd notice it though.

No.

There are few intermediate pilots that would notice it.

I agree, you won't notice that, especially on a trainer.

I'm glad it won't be a problem. Thanks all for the quick replies.

However as gaRCfield said, it's really easy to fix!

Place the plane on a surface so that the rudder is on a flat surface and perpendicular to the fuselage.

Prepare something heavy to place over the rudder to hold it flat.

Using an RC iron heat the side that is bowed out. This will loosen the covering. Keep applying the iron over as wide of an area as possible then quickly place the heavy object, ( e.g. book, etc. ) on it to flatten it. I use an old 12 battery...

Let cool for 3-5 minutes.

Flip it over and heat the other side. Do as before.

If your covering shrinks when it hits a specific temperature, heat the bowed out side to "pull" the rudder flat again.

You may have to play with this a bit, but learning how to do all of this will help you in the long run... as this problem is quite common.