KC's interpretation is spot on about my rather simple Masthead Fly and I just sent him a photograph of it to post later.
Yarn lasts significantly longer than cassette tape and is readily available around my house from my wife and daughter's craft projects over the years.
Sometimes its the simple things that'll win a race as Dave Keran keeps a 12-15" long section of PVC Pipe with a removable end in his Day Sailer to store incense and a lighter to be used in drifters to detect the direction of whatever little wind there might be.
From time to time Dave will have the wood tail of the incense stick between his teeth and lips like a really skinny cigarette while tacking or gybing before sliding it back into a hole in the top of his cuddy cabin where it usally resides when in use.
While I really dislike drifters, over time I've come to realize that its the only condition while racing sailboats that you can be going several times faster than your competitors.