Sailor Question: Puffy Conditions

Alex D. followed up our Sailing in Transitions article with these questions:

"Thanks for the write-up. In the case of puffy winds, or puffy + windy, do you worry about closing the slot? Is the middle trimming the jib or setting to 11.5"?  

Also there is some debate in our fleet about vang-sheeting vs just sheeting out. Better to depower or dump some wind? Thanks! -Alex D."

Mike and I discussed these questions at the Orange Peel this weekend and the following is what Mike believes:

Jib Trim in Puffy Conditions

You absolutely should worry about closing the slot too much.  In very puffy/windy conditions the jib should be trimmed a little out (about an inch to 1.5") from its normal 11.5" position because it's very difficult to adjust jib trim as quickly as the main.  When lots of adjustments to main trim are needed, the middle just can't keep up, so the jib is kept eased a bit more so the slot isn't closed off when the main is eased for a puff.

The more manageable the puffs are, the closer to regular trim you should be on the jib and the more active you are at easing during puffs with the main and trimming the jib back in with the main as the boat flattens out.

When possible you want to trim the sails in harmony, but it is often difficult in practice when you are overpowered, so err on the side of easing the jib in those conditions.

Vang Sheeting vs. Just Easing Main

Regardless of sail cut (Fisher, Proctor, or another sailmaker) the vang is necessary when easing the main in overpowered conditions.

The vang helps bend the mast, which in turn flattens out your sail and de-powers it.  Without the vang on, when the main is eased the mast will straighten out, which adds power to the main.  So while you lose power from the ease, you also add power back in because the sail becomes more full in the luff.

The answer is that you want the vang on to keep the sail shape flat when the mainsheet is eased.  With the vang on you de-power the sail in two ways while easing, making sailing in overpowered conditions much more manageable.