Hi,
Try Greenwich Naval Museum, there is a place there where every ship info. is logged. I must go there myself one day.
But first, nationalarchives at kew, not sure of the web address, do a search and it will tell you if they have the info on line.
I have just typed in tugboat st Fagan..........and there is quite a lot about it.
trying to think of a site.......ah yes........crewlists
Try that it may be a help.
Good luck
Maggsie