Paul Henderson, the outgoing president of the International Sailing Federation (ISAF) says he is partial to catamarans because they do not benefit from kinetics as monohulls do. (Kinetics refers to the crew being able to manipulate their weight fore and aft or in tacking and jibing maneuvers to make the boat go faster.)

When I was sailing monohulls, like Thistles and Lightnings, many years ago, we used to use kinetics to “ooch” the boat forward and help it to get onto a plane or ride a wave better. In today’s dinghies the sailors are trained to do roll tacks and jibes in such a way that the boat comes out of the maneuver with more speed, and there are rules prohibiting this, but the rules are difficult to enforce.

My question is: Can kinetics be used to enhance the speed of catamarans? Most catamaran sailors I have talked to about this seem to think that kinetics CAN be effective with catamarans although to a lesser extent than with monohulls that are capable of planing. (And, of course, some catamaran sailors think that some catamaran designs ARE capable of planing, but let’s just assume we are talking about catamarans as displacement boats, which most of them are.)

So here are my two questions:
1.Can crew weight movement be used effectively to increase speed of the boat in certain circumstances? I know I was moving my weight forward and aft on the downwind legs in the Turks & Caicos to help me catch and hold onto waves. Is this legal or not legal? Does it help or not help?

2. Also, if you have water in your hull, can you use the movement of that water fore and aft to have a kinetic effect that could improve speed in certain circumstances? I know that if you have water in your hull, and if you are going downwind and the boat tilts forward as it is going down a wave, the water rushes forward and increases the potential for a pitchpole. But if that forward rush of the water could be used somehow, in much the same way that monohull sailors use their crew weight to ooch the boat forward, is there a way to make that forward rush of water beneficial? (i.e., increase the speed of the boat but not to the point of pitchpoling?)

Yes it is legal, and yes it helps.

I need to re-read the rules, but you could probably justify a pump of the main and/or Kite to help catch a wave.

Also, I always roll tack my boat (to a much lesser extent than those people that sail 1/2 boats), and it will help a little.

Rocking and the like does not work becasue we use aparent wind so much that shaking the sails is counter productive.

Mary,

I interpreted Paul's 'kinetics' comment geared more toward the fact that monohulls are heavier and have more kinetic energy while in motion. The monohull would be therefore less suceptible to tiny wind and water changes because it has more momentum to carry through waves as well as tacking. Whereas, on the other hand, catamarans are much lighter and do not have the same momentum - hence the sailors must be even more attentive and disciplined to adjust for the lack of mechanical energy. Mistakes are amplified on boats with less kinetic energy.

I know I didn't really answer your questions - but that's because I don't know. I know that ooching your rudders does accelerate the boat (and is illegal) but the only times I'm been in waves big enough that moving my weight might be an advantage, it is usually blowing 15 or better and we're more concerned about keeping the bows high!

Jake,
I see it as the opposite of what you said. The monohulls that kinetics work on are light and have planing hulls. It is boats like the Lasers and the 49ers and the Europe Dinghies where kinetics are a major factor. And even on the Stars there has been controversy.

Frank Bethwaite talks about kinetics as pumping, rocking and sculling (with swept back rudders).

Ref: High performance sailing (warmly reccomended)

Ooching is, of course, an sort of kinetics. Body position and movement is also an sort of kinetics, albeith quite legal within certain limits.

Due to the great stability and speed of catamarans, most of the techniques employed in the dinghys will not work in an significant degree. In very light winds, pumping might help a bit, but the jugdes are murder when they see mainsails 'flicking'.


I agree with Mary, I also think ISAF's president advocates catamarans becouse kinetics are not very efficient there.

I would really like to hear about efficient kinetic techniques usable on cats (besides our partial roll-tack), but I dont know about any..

There are a couple of ideas going on here that should probably be looked at as seperate issues.

-When a mono roll tacks like the do, it uses the roll of the boat from one extreme to the other to force wind and water accross the sails and appendages. That produces the forward thrust. We used to sail J22's w/o an outboard and the three of us would all get up on the deck (w/o sails) and "rock" the boat to the race course (save weight w/o the engine). The keel and rudder would provide enough thrust to move us along.

On cats you can't get the same extreme rocking motion to move the foils enough side to side b/c of our wider beams. However there is a trick in light air...

-Ooching is for and aft instead of side to side. I think it may be legal in a very strick and limited usage to help a boat surf/plane, but not anyothe time. Used like puming the sails to induce surfing.

-Water in hulls... bad at all times. If you have enough water to help pitch the boat forward on a wave, you're already going to be going so slow that it doesn't make a difference.

Having tried that, with an old leaky Tornado, I can safely advice you to sound the klaxon, close all hatches and prepare to dive before you hit the bottom of the wave.

I think you will find that the comments about boats that don't use kinetics also applies to the 49er.

The slow boats at the ollies are (mostly) sailing around where their speed does not generate a great deal of aparent wind and so the rocking/ooching can and does work. The Tornado and 49er are always sailed on aparent wind and so shaking the wind out of the sails is counter productive.

All competitive cat sailors use their body weight positioning to advantage! Whether or not you call it "kinetics" or whether you just call it "trimming" it is all basically the same, with the same or similar results.
When sailing downwind, with a following sea sailors position their weight forward to depress the bows and lift the transoms, this alows the hulls to travel more efficiently through the water with less "transom drag" and it also helps the boat better to "catch" waves. A competitive sailor will always try to move his weight contiually on a cat (whether they are inboard or on trapeze) to attempt to maintain the hull(s) at a stable angle with the minimum of pitch (pitch produces drag) similarly, particularly on trapeze, the weight is constantly shifted in towards the gunwale and out at full body stretch to minimise the heal of the cat with the minimum use of, dropping the mainsheet and pullimg it back on again. These are some of the obvious ways that sailors "use" their body weight in order to "get more" out of their boat. Some may call it just obvious trimming techniques, while others could call it the use of kinetics, which ever, it is apparent to most sailors of cats that the correct use of body weight positioning on a cat has a far greater overall effect upon the different in its performance than it does on any monohull, regardless of what it's called.
Darryl

I guess the problem is how sailing judges define "kinetics" and punish the use of it.

I don't think that proper weight distribution is considered to be kinetics. Moving inboard and outboard, fore and aft to keep the boat balanced is just maintaining proper boat trim.

Lasers are not allowed to do what judges consider to be excessive tacking upwind, because they get an additional thrust of speed out of each tack. This obviously is not the case with catamarans.

However, I do think that catamarans can pick up some speed and distance by jibing downwind -- and I mean jibing more times than is necessary for wind shifts, tactics or getting to the mark.

I don't know about with spinnakers, but main only or main and jib, if coordinated properly, I think you do get an additional forward thrust from a jibe, just from the impact of the main flying across the boat.

Is this kinetics? Or am I just plain wrong about jibing helping speed?

Until I raced a Laser against some Olympic level sailors, I did not realize how powerful kinetics is or how important an issue this is. So let's make sure we are talking about the same thing. Kinetics is where you are using your body's strength (pumping) or movement of your weight to make the boat go faster. Some examples are, a Laser coming out of a tack faster than they went into it or J22 using the keel as a paddle by rocking their boat. You are mostly allowed to use this to initiate something (getting on plane, catching a wave, etc ) but not allowed to use it to continue something (stay on a wave, keep moving in light air, etc).

Let's ignore pumping. It's plainly illegal

Can you use kinetics on a cat? Yes, but it's limited by the stability and overshadowed by the power of the boat. In light air it helps. If you move your weight or pull the sail just right in a gybe or a tack you can accelerate the boat. On a gybe, I think, you are giving the sail one really good pump just as it comes across. Do it just right and it helps the stern across. Do it wrong and you can stop On a tack, I think, you are using the dagger boards and the sails. One good pump and one good rock. I tried a Laser style tack on my 14 (because a friend on a Laser said "you don't have anything to lose"). It helps maintain your speed in a tack and get moving, in light air. I never in any danger of being protested. I was just less slow.

Anouther factor is weight. The lighter the boat, the better it works. The difference between a sudden movement on a 400 lb cat and a 150 lb cat is amazing. One 2 man boats there is the problem of coordination of that weight.

Mary, you started by talking about the Wave. The situation is, you are going dead downwind in light air and the waves are overtaking you. So as the wave moves past the midpoint, instead of letting the boat slow as the wave passes the bow, you move forward at the right time, the boat pivots on the wave, falls down the backside of the wave. It works on a Hobie Wave because it has such buoyant hulls (it floats like a cork) and the tramp is so long. On an A you would have to move 3 ft in front of the mast.

As long as you didn't do it every wave, I would call it "imitating surfing. If you did it on every wave someone might protest. If I were protested, I would counter that most cats don't go dead downwind and do the same thing by heading up a little. I will keep your technique mind for those really sucky days when it pays to go dead downwind.


Just don't be obvious. I once witnessed a Lake Race were only one boat could find any air. As he passed the finish line, he was standing up, urinating off the stern, yelling "rocket power". He was DSQ'ed. Propulsion and unsportsman like conduct.

Whenever a sailor moves their body weight (movable ballast) about a boat "kinetics" are always involved. What we appear to be discussing here is not the principal of "kinetics" but the variations and degrees of kinetics and how it can be applied in different situations on different boats. It would seem that when the use of "kinetics" can be seen to offer an obvious advantage in certain curcumstances, on particular classes of boat, it is then frowned upon and either limited by rule or banned. When it is considered a necessary part of "trimming" the boat it is OK! Can any one else see the hypocracy involved here??
Darryl

Can we agree to use Frank Bethwaites definition of kinetics? If not, what _other_ kinetics sans body movement/placement do you know that makes a cat go faster?

Logically I think you are right Darryl, but do we want to sail or do we want to do 'air-rowing' like the windsurfers? (rethorical question)

To allow some and disallow other forms of the same thing and "drawing the line" at different places for different classes just seems to be a very subjective way of any "rule making"
Besides I really liked the "rocket power".
Darryl

Yeah, but I dont think the "rocket power" is kinetics, more like stored energy, that is also disallowed..

What you all are talking about has nothing to do with kinetics, it's about hydrodynamics: The planning monohulls are flat in the back and v-shaped in the front, if there is enough wind, you move the weight back, so that only the flat part of the hull is in contact with the water. Then you get the boat planning and going much faster, because the HYDRODYNAMICS are optimal. The movement of your weight to acheive that is on the field of statics, not kinetics. Capisci??
Maybe the water inside the hull stuff has to do with kinetic, i didn't understand that, but for sure it's not as exciting as planning.

What about cats? don't know, havn't sailed my new cat yet...
I guess there is no planning, but the cat will go faster anyway, so does it matter? Probably yes, when you get a monohull planning, like a LaserII, it is really FUN..

Sorry Andinista, but this thread is about using the weight of the humans on the boat to increase boatspeed.

When a monohull planes, it goes faster than its theoretical hull speed which is determined by and large by its length and length/width ratio. It transitions from a displacement mode, where it displaces its weight in water, to a planing mode where the hull generates enough lift to overcome the bow wave; wave-making resistance drops off sharply, thereby allowing a quantum increase in speed.

Kinetics can be used to help get a monohull "over the hump" in wave-making resistance and up on a plane.

The vast majority of catamarans don't plane. The only time I've found kinetics to be of any use in catamarans is in surfing downwind (helps to "catch" waves).

Hi Mary,
I sailed one design monohulls for 25 years and won eight US National Championships and I know about this ooching and pumping.
Ooching has to do with accelerating the hull forward on the face of a wave to get the boat up to wave speed so that the boat can be carried along at wave speed as it continuously slides down the face of the wave. Here we go: The boat is sailing downwind at a speed slower than the waves as monohulls usually do. As the wave comes up behind the boat and the tramsom begins to rise, everyone on the boat leans well forward slowly. When the boat reaches its most bow down position on the face of the wave, everyone on the boat leans aft abruptly. This generates an instantaneous small acceleration to the boat hull. Sometimes it is just enough to get the boat up to wave speed and then the boat is carried along at wave speed sliding down the face of the wave. The boat is moving along at wave speed instead of slower than wave speed. The sailors on the boat have accelerated the boat by shifting their weight aft quickly and the boat has reached a speed where it is now carried along by the wave. There has been a momentum exchange between the poeple in the boat and the boat platform. The boat has been successfully "ooched"! It has been accelerated by a force other than the force of the wind in the sails.
Now let's look at pumping. Pumping is causing the sails to generate a forward force by rolling the boat from side to side. Here's how you can tack a Laser in light wind and gain on the competition. As the boat goes into the tack, heel the boat to leeward and let the sail out to a reaching position. As the boat reaches about 30 degrees of turning, heel the boat abruptly to windward and continue turning. This will cause the rig to chop through the air from one side to the other side increasing the relative wind velocity across the sail for a short period of time and generating an instantaneous forward sail thrust. This is pump number 1. Now as the boat completes 80 or so degrees of the tack, the boat is still heeled to leeward on the new tack from pump number 1. At this point the skipper rolls the boat back down to level and sheets the sail in for sailing to windward. This second rolling action again creats an instantaneous increase in relative wind speed across the sail which creats another forward sail thrust. The boat comes out of the tack going faster than when it went into the tack. These two instantaneous increases is sail force were generated by an increase in relative wind speed across the sail due to rocking/rolling the boat under the control of the skipper. This action can be done while tacking upwind or jibbing downwind. This action is sort of like paddling your boat upwind or downwind by using the rig/sails as your paddle.
Boy o boy, isn't Laser racing great; no wonder they put that boat in the Olympics.
Beach cats don't ooch because they sail faster downwind than the speed of the waves anyway. Also beach cats don't pump because they can't rock their boats and cause the rig to swing through the air sideways as the platform rolls. Our platforms are too stable in the roll direction. We can't do the roll thing.
Bill

It's a bit like the man in an out of control falling lift (elevator), just before it crashes into the basement he jumps hard up into the air and simply steps out onto the landing!!
"Kinetics" at its best!!! (or at least a good slap stick movie comedy scene)
Darryl

Hi Billrob,- great input. Thanks.

Then again,- are you the one who can explain to me the theory in why a cat can't go as high to the wind, as a monohull