Ok, the mast of most boats is always a bit longer than the boat, never twice as long, say around 1& 1/2 the length so 40 foot height by 23 long squared is around 1000 squared foot of sail, trim of the edges say 25% 750 squares, and convert to metric 250 squared metres, then cut the figure in half cause the sails are a triangle = 125 Metres Done, easy see lol

750bonnieboy said..
Have just aquired a hood 23 with no sails.

'Acquired' hey, you didn't steal it did you?

I take it you'd like to pick up some second hand sails, as new sails would most likely cost more than the boat. Your local sailmaker could assist with new ones, or re-cutting second hand sails.

If it were me I'd check the buy and sell online (gum tree/boat sales/boat point etc.) and look for hood 23's for sale then contact the owners and ask if they have spare sail\s you could buy. If that fails try other similar sized boats. You can measure the mast and boom easily also, tape measure for boom and measure the mast using main halyard.

This boat in NSW/Sydney is $750 with 3 sets of sales, I think they'd be happy to take some of your coin and sell it with 2 sets! http://www.gumtree.com.au/s-ad/balgowlah-heights/sail-boats/hood-23-project-or-mooring-minder/1135901164

Info on stock setup below: