Using a Surface to Create a New part

Hello,

I have an imported model that I want to use a surface to create a base for a new part.

Picture a car fender (the imported model) , I would like to create a part that will fit over the fender, using the fender geometry as a base.

I have tried to use the cavity tool with little success and tried the foil technique with a surface model.

Anyone have any suggestion or tutorials that might help me learn how to do this.

Thanks in advance for reading.

EDITED BY MODERATOR: Moved to Parts and Features space. Please post to the appropriate space when one exists.

SolidworksParts And Features