I actually am using an alpha with the surface modifier. The stretching is, as you said, due to the fact that it hasn't been unwrapped yet. Thanks for the feedback.
New one, a barrel. Just working on getting something rendered correctly -.- Working with Lattice and Array Modifier. Testing around with varius Modifieres :D
ok totally forgotten to check and that's the solution max gnaaaaaaaaaaaaaaa display ts-bug using 3points quality normal modifier totally fixed it cheers!!
It's the case of a bad triangulation either done by you for not caring enough about the triangulation of the mesh or by max at triangle creation (or can happen with symmetry modifier):