The reluctance of seamen to sail on a Friday reached such epic proportions, that in the 1800s the British Government decided to take strong measures to prove the fallacy of the superstition. They laid the keel of a new vessel on Friday, selected her crew on a Friday, launched her on a Friday and named her HMS Friday. They then placed her in command of one Captain James Friday and sent her to sea for the first time on a Friday. The scheme worked well, and had only one drawback ... neither ship nor crew was ever heard from again.
That may seem extreme, but Snopes seems to agree. Google finds lots of HMS Friday references. Whether true or not, people seem to want it to be true. At least you are certain I posted this on a Friday.
Update: If you are interested, there were 172 Friday the 13ths during the 18th century (the 1700s), another 172 in the 19th century (the 1800s), and another 172 this past century. A web page with a Java script that can provide you a list during any time period is available here. Also, the story above is difficult to verify since several large lists of Royal Navy ship names through the years do not include an HMS Friday.