Rib under round surface

Hello.

I am having some difficulties with creating Ribs under the model that I have created, pictures are attached,

Basically it is like a round half pipe that requires ribs to go across for more support, this is going to be an injection mold part. I have managed to create the ribs by using a Boss extrude and repeating the pattern. it looks good and just the way we want it except there are gaps between the part and the extrude, so what I have done is not really a rib, just looks that way.

Thank you in advance.

SolidworksSurfacing