dimensions, equations and why they are needed.

Firstly here are some dimensions taken from the YSR-10 racing yacht.

Boat
LOA
34,2 ft
LWL
32,8 ft
Width
10,5 ft
Displacement
ex 1400 kg
Draft
9,8 ft
Draft keel lifted
5,9 ft
Sail
Sail Area Main
43 m2
Sail Area Jib
28 m2
Sail Area Code 0
52 m2
Sail Area Genacker
130 m2
Mast Height over DWL
15,50 m

Now that some dimensions are know we can use these to calculate the force on the mast due to the wind.

Force on mast = mass flow rate X time X acceleration due to gravity

Force on mast = ρvAtg

Where:
· Ρ = density of air
· V=velocity of air
· A=area of sail
· T=time
· g=acceleration due to gravity

NB: this equation gives the total amount of force acting on the sail over a period of time, therefore to find the force acting on the mast at a given point in time. Time is negligable.

Next we can calculate the bending moment and deflection using the following formulas:

Bending moment equation = (ρvAtg z^4)/24 assuming that the force on the mast is uniformly distributed.

Therefore the deflection equation

V= (ρvAtgz^4)/24(230x10^9)(9.54x10^-5)

Assuming:
· the mast has an internal diameter of 100mm with a wall thickness of 22% of the internal wall.
· The mast is made from carbon fibre with a young’s modulus of 230Gpa
· The mast has a constant diameter and does not taper.

Reasons for the equations:

1. It is important to know how much force the mast can take before breaking, this can be calculated using the first equation and the elongation percentage of the carbon fibre.

2. The bending moment can be used to find the maximum slope of the mast and thus find the spot on the mast where strain is highest and where the guages should be placed.

3. Deflection equation can be used to calibrate software and strain guages.

Wind Sensors - Powering and Suitibility

Powering

From what I have seen on existing control systems, the above sensors do not require individual powering. The power source required by the sensors is delivered from the CPU, which is about 12/24 V. I’ve seen some highly sophisticated control systems with more sensors set up like this so it should be okay…. I think

Suitability

The sensors highlighted above are in wide use at the moment, and have been tried and tested over a number of times. As these are currently used by the professionals then if it’s good enough for them then it’s good enough for us!

Wind-related Sensors

These are the Sensors which in my opinion are required for our 'racing yacht'. If there are any problems with my selection feel free to comment or email me thanks.

A Wind Transducer on Masthead

Used to measure the true wind speed and the apparent wind speed (wind speed that is ‘felt’ on the boat). Can either be wired or wireless.

Gyro-Stabilised compass (AKA Heading indicator)

Provides Heading information through the 3 axis rate gyros to correct the motion of the yacht. Also provides Heel and Trim data. This compass ‘learns’ the magnetic effects on the yacht and automatically applies the deviation correction.

Gimballed rate sensor (GRC)

Normally a single-axis gyro is fitted in the plane of the boat. This means that when the boat is heeled the single-axis gyro is susceptible to errors when the boat pitches back and forth. A GRC solves this problem by ‘gimballing’ the rate-sensor, ensuring that it is always measuring the true yaw rate, independent of any heel and trim effects. GRC can also integrate with heel and trim sensors.

Inclinometer #1 – heel angle sensor

The addition of a heel sensor to the system provides display of Heel Angle and increases the accuracy of the following functions:

· Apparent Wind Angle

· Apparent Wind Speed

· True Wind Angle

· True Wind Speed

· True Wind Direction

· Dead Reckoning

· Tidal Set and Drift

Inclinometer #2 – Trim angle sensor

Provides display of Trim Angle and increases the accuracy of the following functions:

· Apparent Wind Angle

· Apparent Wind Speed

· True Wind Angle

· True Wind Speed

· True Wind Direction

Mast rotation sensor

Assuming our racing yacht will have a rotating mast (most existing racing yachts have them) then we will need this because otherwise the wind data (measured from the masthead wind transducer) will become inaccurate as the mast rotates away from the centreline. Using this sensor introduces 2 additional functions, ‘wind angle to the mast’ and ‘mast angle’. These new functions can be used to correct the measured wind angle for mast rotation angle.

Scope of project Revised

In relation to the informative post by Jarrett, I will agree that we do not have to redesign the the yacht. However, in relation to the sail alone and its close "working Partners" in this case i mean the mast and riggin, we have have to determine what our inputs are, and that our outputs will be.

So talking of inputs and outputs, we know controlling the sail is the main goal and objective, hence we have to think to ourselves. What factors will make us want to adjust the sail?
It is true that all the wind, tide, current, depth and all the jobber jabber we do not have to analyse but we do have to find a way of linking the control of sail to the feedback of the other variables. Otherwise how do we know when the sail is to be adjusted if the wind direction is against us. (Something to consider).

Back to the issue of inputs and outputs, some of these are listed below. These outputs are what I think should be monitored. However, if you think otherwise, then make a comment or we can talk about it in the meeting.

Inputs

Wind speed
Tide
Depth
Wind direction

Output

Mast height (Up and Down)
Mast orientation ( 360 degree angle rotation)
Sail - (open or fold)

We just need to find a way of linking their information to a particular central processing unit which will will intend affect the output of the mast and sail together.


To conclude below is an extract i found about sailing

Sail trim:  In order to minimize the possibility of tangles and
fouled rigging, running rigging must be kept as simple as
possible with 1:1 sheets and control lines where possible.
Linear actuators, similar to those used for the autopilot tiller
control, will be used to adjust sheets.  Note that the duty cycle
of an actuator used in this way is extremely intermittent, and
their reliability should be far greater than that of the
actuators used for steering.  The mainsail will be controlled by
a single-part sheet and one or two actuators.  The jib will be
most likely be a conventional non-self tacking working jib, with
an actuator controlling each sheet independently.  This
arrangement will probably offer the least possibility of a
tangle, maintain good trim through the widest range of wind
speeds and angles, and work well with roller furling.  A single-
sheet arrangement with a boom or tacking track might still be an
attractive alternative, however.

Reefing:  The jib will be roller-furled around a rigid luff-
support spar.  Although luff-support reefing/furling systems are
subject to reliability problems on larger vessels, the approach
here will be to use a grossly oversize system.  There will be
only two positions for the jib: furled and unfurled.  The furling
spool will be driven by a continuous chain drive from a small
electric motor.

There will be one fairly deep area reef in the mainsail.  A
linear actuator will slack the halyard, tighten the reef clew,
and tighten the reef tack simultaneously.  No lacing lines will
be used.

In order to insure smooth working of the mainsail luff, steel
lugs will be sued at the inboard end of each batten.  A
lubrication system will introduce lubricant into the track.  In
moderate weather, the reef will be exercised about once a day to
prevent salt build-up or freezing of moving parts.

All actuators and servo-motors for trim and reefing will be
located either inside the main boom, or in a special shallow
compartment located just below the main deck, sealed from the
rest of the model's interior.  Because a small amount of water
will enter this compartment through the ports where control lines
penetrate the deck, here must be provision for draining or
pumping this water overboard.

Reference

http://www.well.com/~pk/ZHTAtechprop.html - ( VI Sailing)

Yacht control software (Route Planning)

After reading Jarretts post I did a bit more research into Yacht route planning software. It seems that Deckman v9.1 is a well regarded software but it does have competitiors. One of these competitiors is a software program, again run through a laptop, that offers all the same services as Deckman but also has the ability to integrate a multitude of external components. These components assist with route planning by offering the planning software (Expedition in this case) a more informed version of the full picture.

Here is a list of the components that are fully integratable with the Expedition software; obviuosly the list highlights the versatility of this system:
AIS receivers,
B&G,
Cosworth,
Koden radar,
KVH Quadro,
Navico broadband radar,
Nexus NX2, FDX and NXR,
NKE,
NMEA 0183,
NMEA 2000 (not yet certified),
Ockam,
Racing Bravo,
Tacktick,
Various compasses, lasers and other sensors,
Networking support.

The link below accesses the website:

http://www.tasmanbaynav.co.nz/about.htm

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

There are already existing systems on the market for automaticsteering of yachts. They only provide direction whilst using an engine to power the boat however. There is no mention of any system avialble for operating the sails of a racing yacht.


This link shows a wide range of marine equipemnt aimed at automatically controlling a boat.

http://www.raymarine.com/default.aspx?site=1&SECTion=2&Page=733&Parent=5