The "I" is the "hoist" of the headsail.... or the distance from deck to halyard block at mast head. What you want to know is the Luff measurement.. Since the sail in question is from a Hunter 27, it will definitely fit on your 30, but I think the size will disappoint you... and affect boat performance.
The following data was taken from
www.thesailwarehouse.com.
A stock
Hunter 27 standard rig 110% jib dimensions: Luff = 31.50 and L.P. (luff perpendicular) = 12.90
So the area/size of the sail is .5 x L x LP or around
203 sq ft.
The
135 genoa on a Hunter 27 standard rig is Luff 33 and LP 15.10 for
249 sf
For the
Hunter 30 standard rig.... the
110 would be Luff 39.3 L.P. 14,2 for
279 Sf
the 135 would be L 39 and LP 17.25 for 336.3 sf....!!!!
What this tells you is that even if your H27 good deal sail is the 135 genoa at 249 sf....be more like a 100% jib size for your H 30.... But wait.... even though you might find this acceptable.... you must consider the geometry of your rigging.... i.e. jib leads, and tack height. It just may not fit the deck layout.
If the sail does match up to your deck layout and you are happy with a non overlapping headsail... it may work out after all.
