No 1 This is normally the largest white sail. The foot of the sail is longer than the J measurement <font color=red>distance between forestay and front of mast</font color=red> In some cases this can be up to 160% of the 'J' measurement but depends on the boat.
A working jib is a smaller sail with the foot length near to the 'J' measurement.
A No 1 is a more powerful sail but takes a bit more handling especially when tacking.
The working jib can be used in stronger winds. It is often the prefered sail when sailing overnight especially with restricted crew.
For example my No 1 has a foot of 21' 5" and an area of 460 sq feet.
My working jib (blade) has a foot of 14' 10" and an area of 275 sq feet
J measurement is 13' 10"
Iain
<P ID="edit"><FONT SIZE=-1>Edited by iainsimpson on 09/03/2003 14:13 (server time).</FONT></P>
Generally about 75-100% of the fore-triangle area, though going by the book it is supposed to be 100%.
I use mine on the roller furling for windward work in >F6, rolling it down to smaller than storm-jib size.
It's cut as a yankee, sets on a strop and the clew is just aft of the mast
The solent, or blade jib, represents 105% of the foretriangle, being a deck-hugger totally filling the foretriangle and cannot be used with the roller furling.
It is definitely the most powerful windward sail I have.
My roller genoa id 150% of the foretriangle, which is about as large as you can feasibly go. It's good for medium condition reaching and light-weather beating.
For really light weather reaching I use an assymmetric, genniker, set on cord leech and a bowsprit.