thecutofyourjib

We are rapidly running out of sailing season, and I’m starting to get a little twitchy.

Between recent land-based obligations and the stalled remnants of a tropical storm kicking up a gale along the coast this weekend, we haven’t had Fortuitous out in a while. It’s a drag not having Tuesday night racing to fall back on, and it doesn’t help that Jen and I have both had colds. Sailing is more of a lifestyle than an activity though, and sailing operations don’t cease when we’re away from the boat; they just get weird and slow and probably don’t make for awesome boat logs.

New (Old) Sail

Fortuitous came with a hank-on 110 jib that was probably original to the boat. “Hank-on” refers to the way that the sail attaches, in this case with a series of little bronze doodads called hanks (technically piston hanks, I think) that clip the leading edge of the sail to the forestay. We used this sail the first season that we had the boat, but lucked into a roller furler when we had the mast replaced. The roller furler has a plastic track that rides on the forestay and receives a sail with a bead on the leading edge. The whole contraption rotates around the forestay so that we can store the sail there, or roll it in a bit to make it smaller in high winds. The track makes the forestay incompatible with hanks though.

The sail that came with our roller furler is about a 150, which is much larger than the 110. That gives us good power in light winds or when sailing downwind, but it’s often too much, especially this time of year. We can roll it in slightly to make it smaller, but its shape quickly gets distorted and it sits too high on the forestay, making it a less effective airfoil.

Well, I finally took our 110 to a sailmaker and the hanks replaced with luff tape so that we can fly it with our furler. I’m curious to see how it goes. It’s pretty old and probably blown out, but the shop tidied it up a bit and I think it should be an improvement over our reefed 150 in brisk winds. It’s always nice to have options.

Jib Diagram

Jib Overlap Calculator

At the confluence of contemplating a 110 vs. a 150 and being a little stir crazy from having been sick and lying around for a couple days, I accidentally made another foray into JavaScript.

The “110” or “150” when referring to a headsail is the ratio between the size of the sail and the size of the boat. If you were to imagine the triangle that is formed from the mast and the forestay, the base, running along the deck, is called the “J Measurement” or just the J. If you were to make a line from the clew of the jib to the luff, that’s called the “luff perpendicular” or LP. If the LP is the same length (100%) of the J, the jib is a 100. So our 110 has an LP that is 110% of the J, and the 150 is 150%.

I previously calculated the exact size of our big jib in this log entry. Given that I only had the outside measurements of the sail (and not the LP), I used Heron’s Formula to calculate the area and then used the normal “area = ½ base × height” formula to figure out the LP, solving for height.

I wondered how hard it would be to make a web page with a calculator to do all of that math, and it turned out to not be that bad:

/apps/jibcalc.html

It was much easier than the signal flag thing, and I got to reuse the style.

I think I had a Bootstrap breakthrough in the process. Maybe. I feel like the web hates putting things next to other things. It always feels like some outrageous hack to get them to line up properly, and even then it will only work in some limited percentage of browsers and window/screen sizes. I think Bootstrap rolls up the outrageous hacks into one unified, reasonably well-labeled hack. I eagerly await feedback from the developers to tell me if this is correct.

Yeah, so this is what happens when I don’t sail. I hope, for all our sakes, that I get to try out this 110 soon.

 

 

“Prepare to fend off the bridge abutment.”