Aft-shifting C.E. throws reefed sailplan out of whack

Todd Bradshaw, Contributing Editor, Madison, Wisconsin

Here's an interesting brain teaser that cropped up a couple of years ago for a customer's canoe sail. He wanted a standing lugsail, which is a good all-around sail type for a canoe, but which tends to be overshadowed by the more-common lateens and balanced lugs. The standing lug will go up and come down equally fast and like its balanced cousin, it generally has shorter, more easily-stowed spars than a lateen. Compared to the balanced lug, which has its boom and entire luff out forward of the mast, the standing lug's tack corner is back at the mast with just the yard's heel and the upper part of the luff extending out in front of the mast. The luff then sits at a slightly diagonal angle to the mast. The boom usually bears against the back of the mast with boom jaws, and a downhaul line pulling downward on the jaws and cleated on the lower mast provides the luff tension that lugsails need.

In use, the standing lug configuration tends to exhibit more twist to leeward in its upper half than a balanced lug will. As you ease the sheet, the tail of the boom lifts a bit and this eases tension on the leech, allowing the peak end the yard to twist to leeward, taking the upper sail area with it. This twisting tends to spill wind up top, depowering the sail. "Twistability" can also add shock absorption if you happen to be sailing in gusty, puffy wind conditions. By contrast, balanced lugs tend to pivot like a barn door when eased, with far less twist. This is great for maintaining maximum wind-catching sail area all the way up and down the leech, but on the other hand, its not so great if you're getting overpowered or slammed by gusts. In these conditions, being able to let the top spill some wind, or having more shock-absorbing twist available, might greatly reduce heeling force and make your ride less wild.

My customer in this case was doing some canoe-sail camping on rather big water and wanted a reasonably tall standing lugsail for light air, but two sets of reef points for days when the wind and chop picked up. We decided that one moderate reef and one substantial reef would be the way to go. I set to work drawing up a building plan. It soon turned out to be a much more complex proposition than I had anticipated. With a first reef line that roughly paralleled the boom, sail area was reduced and it looked like the reefing process would go fairly smoothly and not require having to re-tie the halyard to a different spot on the yard. I added a parrel line with a handful of wooden parrel beads, tied to the yard and surrounding the mast to keep the yard close to the mast when raising or lowering the sail, or when reefed with the yard raised only partway up the mast, and it looked like we were in good shape.

Trying to add a parallel second reef line, however, messed up everything. The Center of Effort shifted dramatically aft and it looked like the parrel line and halyard would both need to be untied from the yard and re-tied in a different spot in order to get the sail to hang properly when putting in the second reef. The more things you have to fuss with just to put in a reef, the less useful that line of reef points becomes. It's basically there to save your bacon, not to give you practice tying exotic knots or repositioning your leeboard bracket in a wallowing canoe. It was looking like the second reef might be too impractical to even be worth having - but for the conditions that the boat might encounter, we really wanted two reefs.

After a certain amount of stewing and a lot of cutting and pasting on the computer, refiguring sail areas and Centers of Effort, the solution which floated to the top seemed and looked rather unusual, but in the end it worked pretty well. I angled the reef line upward from leech to luff, rather than just adding another line echoing the angle of either the boom or the first reef. The resulting sail area changes into something that tends to look more like a small lateen, hoisted aft of the mast than a lugsail It reefs-out nearly the entire lugsail luff and the head of the sail along the yard essentially becomes the new luff. The good news is that the halyard tie-off point and the position of the parrel can now remain in the same spots on the yard through all three size configurations, with no untying or re-tying needed. The Center of effort will move downward a bit with each reef, reducing the heeling leverage of the sailplan, but its fore-and-aft position stays nearly the same whether at full sail or reefed. This should eliminate the need to be messing with the leeboard bracket as part of the reefing process when you have other, more important things to worry about. The boards will remain right under the C.E. in all three sail size configurations. The boom height and angle also remain reasonably similar throughout the reefing process. As with any reef, you still need to tie the reef tack and clew rings to their respective ends of the boom and bundle and tie-off the excess, unused sailcloth along the boom, but other adjustments are minimal.

The drawings show the three configurations and the last one has them superimposed to show changes in the position of the Center of Effort as the sail is reefed. I don't imagine that this is a unique solution which other lugnuts have somehow failed to figure-out over the centuries, but such an oddly angled reef line it is likely something that many sailors have never seen. In this case though, it's just what the doctor ordered.

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