Hello DonaldP
The links to the left are shortcuts to the Ozship site
under shortcuts
click arrivals
you will see the page displayed 'Vessels arriving by year'
schroll down to year 1840
click date range 1840 Nov. 19 to 1841 Mar 17
page will show list of vessels by date, port of arrival & name ship
schroll down 1841 Jan 15th port launceston ship Arab
click name of ship 'Arab' for more details
if you follow the same process above you will find
Arab arrived Launceston 1842 March 31 - 282 passengers
(the passenger names are not listed )
There are many different named ships arriving at Launceston at different times, example between 1842 Mar 14th - 1843 Feb 15th there were around 11.
You could look at each one individually you may get lucky and find your family or first you may want to try Janet666 link
I don't know if this is linked with the national archives, you could contact the person who has put all this info. together there is a contact name under the help section 'asking for help'.
Sorry I can't be of more help
Good luck, if you find anything do let us know