The only crappie I have caught at Chatfield were by chance, the biggest 15-16 inches and the other one about 10. I got both of them in the spring in the Kingfisher area along the west shore, where there is some flooded brush and further north where the water meets the trees. The big one on a minnow abut 5 feet from shore, the other on tube jig from my canoe.
Crappie are pretty scarce there. At least I have not been able to find them consistently.
If Chatfield is anything like CherryCreek Id go thru the boat docks @ the marina. We would catch over 50 in a night in there. Best if you have a boat or even better with a float tube. I wouldnt sneek in over the gate(thats what we used to do)