In my last post, I proudly presented my Excel file that could calculate true wind speed and direction from datas available on board, ie: apparent wind speed, apparent wind angle and boat speed.
I must say I was lately a little ashamed... when I discovered that someone else had had the same idea before me!
Besides, this person had the good idea to produce a very simple website instead of an Excel document.
You can easily visit this page, add it in your favourites or best: record it in your tablet or smartphone navigator, so you can access it even if no connection is available.

So here it is: https://questeria.info/tw/ 
The only difference is that you must input your boat heading too, which I assumed to be zero degrees since I wanted to estimate the true wind angle relative to my boat axis.

Of course, one can happily live and sail without bothering! 

In every harbour, when people intrigued by my junk rig come to inquire about it, which I always enjoy, the inevitable question arises, after merely 2 or 3 minutes of my enthousiast talking: " How does it go upwinds? "

As we were sailing down south from the Morbihan gathering, Kevin Cardiff and I started thinking of a ways to measure our upwind performance, while the only indication we could observe were boat speed, apparent wind angle (composed of the real wind angle plus our own generated wind), and the apparent wind speed (composed of the boat speed, and the real wind speed).

The two latter being read, although very approximately, from our wind indicator.

Back home,I made some web searches, and numerous simulations. This involved trigonometric relations, vectors and ancient theoremes. And several beers.

All this was made in a very empiric trial and error manner, since my knowledge in trigonometry is nearly inexistant.

Here I should mention that when I was 15, the girl sitting next to me in math class was a tall brunette often wearing short skirts, so my attention to the course was somewhat diluted - not that I regret it.

Therefore I must admit I did stupidly assemble some equations from the web, and tweaked them until I came to a reasonable result.

So, here attached is an Excel file for you to test, and suggest corrections (vocabulary, calculations, presentation).

I have tested it on several drawings of triangles as the exemple shown on the Excel file.

You need to enter 3 values:

• Apparent wind angle (what you see on the wind indicator, very approximately)
• Apparent wind speed (what you read on the wind indicator, also approximately)
• Boat speed (read on the loch, but since we don’t have any on Paradox we read on the GPS, obviously neglecting any possible current)

But the general principle is there.

I'm quite satisfied with it, and more at ease to produce some figures instead of inventing the truth, when asked about winward performance of my junk rigged cruiser.

Now the problem is that one can't run an excel file while strugling to sail to winward.

I wish someone could find a way to develop this as an app for smartphone or tablet, android or apple, for example.

Although the tall brunette is probably now a plump grand-mother with a few grand-children, I still can't concentrate enough for this task.