Question on Jib Size

[David]

I've got recently acquired 86 c30TR, and I have a question about the size jib that's on it. The Broker says it is a 110%, but it seems a little larger too me. I haven't had a chance to take it off (too busy sailing) to measure. I can tell you that when unfurled, it extends to the stanchion just past the mast near the middle of the coachroof and is extremely low footed (probably 10 inches above the deck all the way back. Would anyone care to take a guess at the size? 110, 120, 135? Also, whoever said the 30 was a slow bathtub was a little off. I personally think that cruising at 6.2 with just the jib in 15knots and seeing surges of 7.1-.3 is pretty respectable for a "bathtub". I know I'll never keep up with a J boat, but try to make margaritas in a J boat!Thanks

 

[Rick]

Figure it out

You can get a close guestimate without dropping your jib all the way. What you want to try and measure is the LP, the distance between the clew and the luff at a point where the luff is perpendicular to the clew. This is easier than it sounds. Open your jib at the dock when the wind is calm, lower it a little bit and put a spare halyard on the jib's tack. Now hoist the tack so that it rises as close to the luff as you can get it until you get a new "foot" that forms a 90 degree angle to the clew. In other words you now have a 90 degree angle between your new "foot" and the luff (which is doubled). That is your perpendicular. Measure that distance and convert it to inches. Divide the result by "J". "J" on a C30TR is 11'6" (138") if you do not have a bowsprit. If you do have a bowsprit your J is 158". For example lets say your perpendicular is 15' or 180". 180/138(no bowsprit)=1.30 or 130%.You could also drop your jib to measure your perpendicular if you have a place to spread it out. Just fold up the luff from the bottom until you have a new foot that makes a 90 degree angle from the luff to the clew and measure that new "foot".

 

[Joe]

LP orientation causes optical illusion

The LP begins a ways up the luff. The luff angles towards the mast. This places the clew to a point well beyond 110% of the foredeck length. Thus the sail appears to be larger than 110% of the fore triangle area.