What about this? When you make the coil, look on the "Coil Size" tab. Change the Type from Spiral to one of the other ones. I used "Revolution and Height".
You will have to make two cuts. On for the straight part thats parallel to the length. Where this stops make a new sketch there and project the edges to make a new closed profile. Use this profile for the coil.
Im on 2013. So me posting my part wouldnt help you.
Here's my take on it, using a 3D sketch sweep instead of a coil. How you model it may depend on how it's going to be fabricated. I couldn't tell from the picture.