Yes, you indeed are incorrectly calculating your jib percent size. It is not the foot length / J. In your case the foot length of 8.25m divided by your J of 5m does indeed happen to work out to 165%, but that has absolutely nothing to do with the % size of the jib. You do not have a 165% jib.
The actual calculation for jib percent is LP/J, where LP is the perpendicular distance from the luff to the clew. J is the distance from the headstay-to-deck intersection point back to the front of the mast. The foot length is simply not a measurement used in calculating the genoa %. One can have a 150% genoa (or 135% or whatever) with widely varying foot lengths, depending on how high off the deck the foot is.
On our Amels, if one takes the position of the end of the rigged downwind pole as a fixed point and then measures the perpendicular to the genoa luff, which is LP, and then divides by J, one gets 150%.
Cheers, Craig, SN(G&T)#68, Sangaris
---In amelyachtowners@..., <karkauai@...> wrote :
Sorry Paul, I don't have those specs available right now. If I find a nice light-air day, I'll measure the 135's foot.
Do you know the foot length of your Genoas?
Original Amel foot is 8,25 m giving an area of 67 sqm. With a J of 5,0 meters I get it to 165%, but I might be wrong in how to calculate the %.
with my way to calculate the foot of your Genoas would be 5,5 m and 6,75 m looks small, am I correct?
Would guess a 50 sqm Genoa would be a good alternative for the Caribbean.
Paul on S/Y Kerpa SM#259