I use a few different rods for drifting on the shambles for turbot.
When the tides are small you could use a spinning rod, usually I use boat rods of 6 to 12 lb class. Something like a diawa Kenzaki or ugly stik?
Get yourself a Daiwa Kensaki 6-12lb and 12-20lbs class and they will handle all the Turbot you can catch. I have had quite a few big doubles up to 20lbs on the 12-20lbs class rod and the 6-12lbs class is great fun on the smaller Turbot and Plaice. Billy Furnish.
Which port you heading out of? as if its Weymouth I doubt you'll be drifting all day for the turbos, you'll probably be doing some anchoring up, and if you do go after the rays you'll need a 2nd, heavier rod....but if your after turbot all day, then yeah a 12-20lb will be perfect for them