wet quilts should NOT be hung on a clothes line- the weight of the wet fabric/batting can stretch the quilt out of shape- and even break threads. they should be tumble dried- (whether hot dryer or low-heat would depend on the quilt) or in you want to dry it outside in the fresh air the way it is done is to lay a clean sheet out on the ground- lay the wet quilt out on the sheet, then cover it with a second sheet (to protect it from bird droppings)
at some point flip it over- it takes a long time to dry them this way unless conditions are perfect with warm sunshine and just enough breeze- but they come in smelling like they were on the line.
my mom has a large double set of clothes lines with i think 10 lines total- she does drape hers across the top of all the lines to dry it- the weight is distributed with only a little hanging over the sides- she does still put a sheet over it again 'cause of the birds.