Hacker News Reader

Comment by n00b101 | Hacker News Reader

This is a great paper. Almost all sailors I've met still believe the Bernoulli effect misconception, even some sailmakers designing carbon fiber sails costing $100k+.

View on HN

I really enjoyed it too. As a sailor, it's an such an incredibly interesting topic. It only gets more challenging when you consider the twist in the sail (change in angle of attack from top to bottom), varied sail shapes and sizes, and oscillating wind patterns.

I also love how even though a technical knowledge of aerodynamics can help you trim a sail, most sailors can do a pretty good job by feel alone.

I thought the point of the twist was simply to account for the wind higher up going faster.

One of a couple of reasons. It's not likely to be as well developed in a review from 81 but an important part of modern high performance sailing is gust and wave response. That is, when you get hit by a gust or a wave, how does your rig and sail flex in response to help you manage. Generally, having the top of your sail twisting off can help with designing for gust response.

Back in the days of square sails, standard practice was that sails higher up on the masts were trimmed looser , in order to give the helmsman time to react when the wind direction changed in a gust (particularly when sailing close-hauled, of course).

Similar errors are in airplane pilot flight manuals, and believed whole heartedly by pilots.

I think a convincing refutation of the Bernoulli effect as an explanation of flight is the fact that some aircraft have symmetrical airfoils and can fly upside down. This is a less convincing argument to sailors whose boats don't usually sail very well upside down :)

Isn't sailing into the wind the equivalent?

Though I learned in my "Physics of Sailing" course that it would be technically possible to sail with the current instead of the wind by putting the boat upside down in the water.

I had the impression that this was the epitome of the way of thinking thought in a physics degree.

Carbon and kevlar tapes are used in sails to minimize their stretch along their stressed areas and allow for optimized sail shape. I don't think anyone selling or making sails tries to convince of any other reason.

Reply on news.ycombinator.com