Tide, Current And Wind sensor needed?.....Maybe Not!

I have done some resarch on racing yachts and came across some info regarding route planning due to wind, tide and current that will make things a bit easier. first i will explain how wind, tide and current are measured.


How tide is measured
Today tide is measured by sending an acoustic signal down a half inch wide sounding tube, which are also protected by a 6 inch wide well , and timing how long it takes the reflected signal to be recieved. These times can used to work out distances which in turn can be used to create a profile of the tide. i.e. its wavelegnth, amplitude etc.

How current is measured
the simplest way to measure current is to have a floating object known as a 'drifter', put it in the water at one end of the ship/ vessel and time how long it takes for it to cover a known distance. this info can then be used to find the speed/ current as im sure you know. Now although mariners today use expensive high tech-buoys as drifters the basic priciple is the same as it was a hundred years ago.
















How Wind is measured
Modern wind vanes (such as the ones created by RM young's pictured right) work as follows, you have a propller that is connected to a magnet that rotates within a transducer. As the wind blows, it causes the magnet to rotate and thus an ac sine wave is created which is then interpreted by a data logger. the data logger then determines the wind speed from the ac frequency.


wind direction is calculated by the use of a poteniometer that via some sensor .i.e strain guage calculates the orientation of the vane.

Disadvantages of having these sensors onboard a yacht
There are two big disadvatantages to having all these sensors onboard a racing yacht:

1. Firstly, Wind, tide and current measurments,are RELATIVE measurements therefore they are dependent on your position and movement. For example, trying to measure the amplitude and frequency of the tide while in something that is influenced by the very thing it is trying to measure, like say a yacht, isn't going to give you a very good measurement of waveheight.

2. Secondly and most importantly, alot of this equipment is quite heavy, and since we are designing a mast for a race yacht it is of primary importance to SAVE WEIGHT.

So how do they do it?

The next question of course is, if yachts only have a few sensors, how do the sailors manage to navigate the sea with such a limited amount of raw data? well the majority of the data such as tide and wind strength, speed direction etc. is collected by tide houses that belong to big organisations such as the Nation Oceanic and Atmospheric Administration (NOAA). these tides houses are very sophisticated and take into account different oceanographic and meteorological parameters. This data is then made available and transmitted to mariners on a consistent basis e.g. every few minutes.

Route planning
So now that we know where the sailor gets access to information the next question is what does he/she do with it? And thats where route planning sofware comes into play. Racing yacht pioneers use software such as deckman v9.1 (pictured to the right), or expedition to analyse the data and plan the safest or quickest route to a given destination. These softwares take into account the gravitational affects of the moon and the sun, wind speed, direction, tide and current and alot of other crazy jibber jabba that sailors don't have time to calculate when they are trying stop a yacht from capsizing in a storm. So now that we have the weather information and the software to process it. all we need is some kind of programable interface that can run the software....hmm now where could we find that....wait a minute...whats this im typing on? ...bingo! Thats right we can use a flippin laptop.

Conclusion

The purpose of this post is not to do away with sensors altogether, im almost certain that a wind sensor or current sensor onboard the yacht will be a valuble additon, however it is important that we don't over engineer. I cant stress this enough. Remember we are developing a sail, NOT THE WHOLE YACHT, so we only need to monitor parameters that are relevent to the sail like wind speed and direction. Tide depth for exapmle has no relevence because if you get stuck in shallow water or on top of a rock, it doesn't matter what angle you point your sail, your stuck. simplicity will be the key to completeing this task.

References
http://www.altendorff.co.uk/archives/1068
http://oceanservice.noaa.gov/education/kits/tides/tides11_newmeasure.html
http://oceanservice.noaa.gov/education/tutorial_currents/06measure1.html
http://www.youngusa.com/products/7/5.html