It's a Sine
14 January 2019
Look out! I'm back, although as you might have guessed, I've had a bit of writer's block. It may even be PTSD. Post Typing Stress Disorder - acquired after one of my readers said that she liked the blog, as long as I "didn't go on".
All that effort.....
Anyway, today, we're casting our minds back to school days and trigonometry lessons and believe me, that's a seriously long cast. The thing is, in my opinion, getting dead downwind on a cat really needs either a spinnaker which I'm not that fussed about when it's blowing twenty plus knots or poles and goosewinged genoas which I fancy, but don't have. So, we're in the sailing the angles business just like when I was a kid. Whooshing out left, gybe, whoosh back right, gybe and whoosh back again. Meanwhile, the monohulls we're with are heading straight down the track, a bit slower but heading the right direction and at each whoosh, we only seem to cross their wake.
So, the question is, does whooshing at an angle get you there quicker than just sitting back and doddering down the line like we used to? Not that we've really much choice. Anyway, it was a question worth testing the grey matter so we set out to do the math. If we've a direct fifty miles to run and the monohulls are doing seven knots how fast do we have to whoosh to cover the extra miles of our zig-zag course to get there at least at the same time but preferably, hours earlier. And, over and above that, what is the optimum angle for optimum speed?
We mapped it all out on graph paper, measured it all off and, taking a stab, we thought it might be the cosine of the primary angle times the average speed. Or perhaps just a sine or even a tangent? Which is where we seem to be heading right now, albeit at ten knots whooshing at sixteen.