Yeah, it's 8' and if by 2.4 metre you mean overall length (and not waterline length) that's really short.
I'm building a double ended boat that size of my own design for my 3 year old nephew, but it would be difficult to use for any but the smallest adult. It isn't finished yet, and I've never been in a boat this small before.
To get carrying capacity for an average sized adult or even several, you might find the odd pointed dinghy but are more likely looking at a pram, and some of them can be pretty boxy. Also, it seems to me that a tiny boat like that would have some serious limitations in seaworthiness and sailing performance.
If the overall length can be more than 2.4 metres but each individual part needs to stay below that size there may be some nesting boats that fit the bill.
Some small boats are designed for sail, with the instructions for the sails and rigging included. Others aren't specifically designed for sail but it might be worth checking with the designer if they can be adapted.
Here are some free plans: http://www.pdracer.com/free-plans/camp_sailboat.pdf https://s3.amazonaws.com/plansmichalak/catbox.pdf
And a whole list of boats (called "rowboats" but some of them sail also) includes links to sites with free plans, plans for purchase, kit boats and also whole boats available for purchase. Click on each link to find out which is which and which ones may have info for sailing included: http://www.tacking-outrigger.com/rowboat3.html
And more plans not on the list: http://stanleysmallcraft.co.uk/stitc...esigns-3-w.asp
(available as kits also in the UK) http://www.windandwet.com/boat/pram/plan.php
These are some of the nicer ones: http://www.woodenboatstore.com/produ..._Nutshell_Pram http://nisboats.com/oughtred/mainpages/prams.html
(available as kit in UK http://jordanboats.co.uk/JB/iain_oughtred.htm
(available as kits also in the UK)
A US kit (they have kits for the sails and rigging also): http://www.clcboats.com/shop/boats/w...iling-kit.html
If you google "8' pram plans" or "8' sailboat plans" and flick through the images you might find something else that you like.
Try also the WoodenBoat forum, where some of the little plywood boats have been discussed and there is no shortage of people offering advice to someone looking for a design.