Symmetric spaceplane keeps rolling to one side

[Stratoroc]

So I made a completely symmetric spaceplane, checked every strut and radial module for their counterparts. From the moment I take off the plane has a slight roll to the left that I usually counter with SAS but it's pretty annoying.

What causes said roll and how to get rid of it?

I am using Ferram, B9, LLL, mechjeb among other mods that I don't use in this specific plane.

[Gus]

Need Photo.

[RoboRay]

Yeah, there's really no way to give specific answers without pictures of the craft.

[MockKnizzle]

It's usually always a landing gear issue. If your gear isn't aligned straight forward you'll often have problems. Try messing around with different configurations.

[Moar Boosters]

It might be a fuel flow issue if you have multiple tanks connected with pipes. Check if they're emptying evenly.

[Syhrus]

I do sometimes get this issue with B9. For some reason one wing will flex more than the other even if I strut them up to buggery. I sometimes find restarting KSP works at fixing it, but I'm guessing you would have tried that.

[mellojoe]

Do you have a single tailfin vertically? Sometimes the tailfin is counted as a wing so it creates sideways-lift. You can counterract this by using pairs of tailfins. The symmetry means their sideways lift is exactly opposite of each other, keeping you straight.

Also, sometimes you can slightly tilt the wings up or down. This adds slight sideways lift in equal amounts, left and right. Sort of like having slight toe-in on an automobile. The slight offset gives better straight-line stability.

[Stratoroc]

so I added struts to the wings and the problem all but went away, probably wing flex as Syhrus said.

The landing gear is straight as far as angle snapping allows, I suspect even snapped it's possible to tilt the landing gear ever so slightly depending on which part of the part mesh it's attached to.

Edit: could the jet engines clipping into the wings be causing odd engine wash effects as the wings flex?

Here are pics of the thing:

Edited August 19, 2013 by Stratoroc