[I wrote this post ages ago but for some reason didn't post it!!!]
I've now finished the radar. I had several suggestions from others who have built a Tamar but decided to stick with my original plan! It's a little overcall and not 100% accurate but it'll do me.
It tool a few attempts to get right. My first go ended up being too small for the motor, the second too big and the final one is a little tight but does the job. It will come apart to get the motor out but hopefully that won't ever be necessary as I'm not sure the box would stay in one piece...
It's all made with plasticard though I used filler for the front and rear faces of the bottom half. As I needed to use thin plasticard, I hoped that using filler would let me round the edges and it worked though the filler may not survive taking it apart in future. The arm is square plastic tube with half round styrene rod.
So here's the line up of the base parts:
And the finished item.