How can I use BodyVelocity to move an object in the direction it is pointing?

this contains no code as it is a simple question. how do i move the part forwards in the direction the part is pointing?

lets say a part (with gliders) is pointing forwards (+x) and there are rails turning beside it. the problem is it doesnt follow these rails. it decides to stop a quarter down the turn, fly up, and run further away in the +x axis. how can i make this turn? does it have to turn using a script that changes the direction of the force (changing bodyvelocity.maxforce and bodyvelocity.velocity to the z axis if the orientation falls under a certain defined number zone?) or can i use a different body mover? Please help me.