Archive for the 'A Peek Inside' Category

Jun 17 2009

About Nose Diving

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If you watch the contestants in the Fizz Cup struggle for a place on the stage, you will no doubt have seen some of them capsize or nose dive. At first a nose dive looks quite funny and you think he or she must have made a mistake. But there are not many who know what mistake the sailor actually made and what lies behind this malheur. I will try to explain and illustrate. My apologies for the poor quality of some of the images.
There is a big difference in the forces on a boat when it sails upwind or downwind. Just look at the 2 images of laser sailors. The first is sailing upwind in a gentle wind and the second is reaching in a strong breeze. Notice how the sailors in the first image are sitting towards the front of the boat while in the second image the sailor is hiking backwards.
pic-1If you sail upwind, the forward pressure in the sail is relatively small and there is a wind that blows against the rig, trying to tilt the boat backwards. The speed is relatively slow and therefor the resistance of the hull in the water is not big either. The sailor sits at the front to make the water leave the transom in a smooth way.
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If you sail on a reach, the forward pressure in the sail is big, there is almost no wind drag and the hull is literally dragged through the water with great force. The sailor needs to sit at the back of the boat to prevent the boat from pushing the nose down.
Unfortunately you cannot sit at the front or back of the boat in SL. And therefor a Flying Fizz doesn’t nose dive if you sail it normally on any course. But there are more forces in play….
If a boat heels over to leeward, the sail will try to turn the boat towards the wind. This effect is called weatherhelm.
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In order to sail in a straight line, the sailor needs to steer away from the wind. But the rudder is located at the back of the boat and is not only steering, but also lifting the transom. And if you lift the transom, you automatically push down the bow. A normal boat will still not nose dive if you do this gently though.
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But now add the effect of waves to this all. Imagine you sail on a reach or downwind and you approach the gybe mark. Big pressure in the sail pushing the boat forward, tremendous force on the hull that is dragged through the water, the boat heels over to leeward, you hike full, but it doesnt help much, you are fighting to keep it under control, you steer to compensate, the bow is pushed down further, the boat surfs down a wave going really fast.
The mark is coming towards you at great speed! It’s frightening! You have to gybe now!
But right at that point in time, you have fully surfed down your wave and the bow hits the next one. But still you steer away, because if you dont some one else will sneak between you and the buoy. You compensate the weatherhelm and try to bare away to make the gybe.
BANG! In a blink of a second, the bow pierces the wave, buries itself in it, the boat suddenly stops, the sail pushes further and there is nothing you can do anymore except swim.
Look at the diving cat in the picture. Do you see their course with respect to the wind, the wave they hit and the sail pushing further?
pic-6That’s what makes a Fizz Cup contestant pitch pole. If only we could show the waves a little better, improve the terrifying sounds of sailing at high speed, feel the pressure on the rudder and experience the fear of loosing the control over it.

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May 10 2009

Integrity Checks

Published by under A Peek Inside

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[Ed. Note: We welcome Mothgirl Dibou to the pages of SL Sailing with her new column “A Peek Inside”. For some time now we all have enjoyed watching Mothgirl’s work in pushing the envelope of SL sailing. When I asked her if she might like to do a column on her thoughts and insights she was at first hesitant because she feared the people would think she was just promoting her boats.  On the contrary, I said, people want to know the inside stories about how boat designers go about their work. They would love to know the sense of struggle and successes that designers feel. So here is the first installment of  “A Peek Inside”.]

As a person I think fair play in racing is something that should come from the people themselves. If someone wins by cheating he should ask himself if that victory is really as fantastic as he imagined beforehand. If you loose from someone that cheated I think the victory is double. You were the first on the non-cheaters and you played it fair. If you extend this thought, fair play is a self-regulating system and no one has to worry about it too much.

fizzthumb1_001As a boat builder I think I have an obligation to prevent cheating in any way I can. This seems contradictory to what I just said, but it isn’t. I need to prevent people from tampering with scripts or configuration parameters, because I owe this to race directors that want to ensure a fair race and to contestants that want to be free from any suspicion. Even if no one would ever cheat, I still have to make sure cheating is as impossible as I possibly can.

With the start of the Fizz Cup 2009 this topic is more important than ever. The stakes are high and the organization wants to be absolutely sure that everyone has an equal chance at winning.
People can cheat in many ways of course, but the ones I can do something about at the moment are editing the scripts inside the boat, editing the configuration parameters of the boat, changing the appearance of the boat in a way that it brings an advantage and wearing attachments that bring some advantage. It is up to the race directors to decide what is allowed and what not, but it is up to the builders to inform them on what is altered and what not.

This is what I am working on at the moment. Integrity checks for the Flying Fizz and for the Boat Building Kit. It is not something very spectacular I’m afraid. In fact, if I do my job well and everyone plays fair you will never even notice it.

Don’t get me wrong here. I don’t really mind if people change their boats in any way they like. Any check that is performed should never disable the boat. I think checks should simply inform everyone that something is not original upon entering a race.

To do this, the configuration notecards are now checked to see if they are genuine by reading their contents. And I equipped all scripts with passwords. The scripts are checked by asking them a question and waiting for a reply that can only be generated if the password inside the script is correct.

To eliminate the far fetched possibility that someone would replace all the scripts at once I extended the SLSA protocols. The subscription message that is send from the boat to the WWC Setter now also includes an encrypted checksum (which should be the same for each boat).

fizzthumb1_002Changing the appearance is not checked yet. One could for instance make a transparent sail to have a better view, with big colored telltales or with illustrations of the up/down keys to tell you what to do. One could make the whole boat phantom to easily round marks or make it smaller. I am figuring out a way to check this, but most of these things are clearly visible already.

Next up is checking attachments. That’s a tough one, since they often cannot be seen by anyone else. It is possible to check the number of running scripts inside the sim for this, but for any race other than the Fizz Cup this would be too much to ask. I have a few attachments on my to-do list as well and I intend to extend the SLSA protocols for it. The WWC Setter announces a race and the minute a boat subscribes to the race, each official attachment worn should shout a message revealing its presence. It is up to the RD to decide if the attachment is allowed or not. Of course this only works if all builders of attachments would do this. And even then one could still make their own.

Oh well.. Who knows… in time you might not even be able to ignore a boat coming in on starboard tack anymore. Big Brother is sailing with you. Nah, I should never come that far. Double plus ungood.

3 responses so far

Oct 21 2008

Mothgirl Talks Winds of Change Thursday at NYC

Published by under A Peek Inside,People

This past week, Mothgirl Dibou rolled out her new Wind, Wave and Current System. Moth’s been working on this for some time, and she’s shared many of her ideas and early models with sailors to get their input and feedback. Taku Raymaker’s fleet over at Waypoint were particularly involved recently, helping Mothgirl test out the system and get it bulletproof. Mothgirl, Jane, Francois and WWC

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