I'm an x boy scout and avid knotsman but for the love of me cannot get the halyard to stay in place, sure my knots hold up but why the slipping maybe electrical tape? what are you doing? clove hitch? timber hitch?
Never tie a clove hitch on a trailer hitch ball!... like ol' Clint said as Dirty Harry, "A GOOD MAN ALWAYS KNOWS HIS LIMITATIONS!"
P.S. This doesn't really apply to a Minifish or Sunfish, but a clove hitch works great aboard larger craft for securing fenders to stanchions... the hitch allows for quick & easy adjustment in placing the fender at just the right height for hull protection. For those sailors who've ever found themselves cursing while adjusting other knots used for this purpose, try a clove hitch, it'll make your life easier, LOL.