None? Huh. Is it all the same single piece of yarn? I've never had much luck with the change from ring to looping without knot if it's bigger than a ring pad 
Yarn is made from roving or some other form of processed wool(or some other fiber, say silk or alpaca or hemp or flax. Cotton has short fibers and would be harder to spin on a drop spindle).
String has already been spun, which is what makes it string.
Here's some carded wool, for example:View attachment 807
Knitpicks.com actually has some pretty decent roving on sale for <$2/oz
Aw, heck, why don't I just come to Maine to give you a lesson?
While on vacation in Nova Scotia in September, I tripped over this pamphlet for the Nova Scotia Fibre Arts Festival and it made me think of you...