Turning in a tube with raycast

I have a ball rolling through a curved tube using raycasts, long story why i can use physics. So I have a raycast rotate combo that moves the ball forward, and can role strait, and up and down hills. Unfortunatly much like zoolander, it cannot turn left, or right for that matter. So my plan is to use the balls raycast down, and then get the forward of the triangle its currently hitting. and rotate around the y axis to match it. I believe barycentricCoordinate, may be able to help but there is almost nothing anywhere on how i could possible use it. So does anyone know ow to use it, or have a better solution?