Why Catamarans Can’t Sail Into Wind? (Surprising Answer and Full Explanation)


Why Catamarans Can’t Sail Into Wind

Most catamarans can’t sail into wind because they lack a full daggerboard. “Everyone” believed cats didn’t need daggerboards because they were fast. A catamaran with a full daggerboard points better than racing monohulls. But lacking daggerboards means they can’t counterbalance the sail force of the wind. This forces strain on the rudder and relatively poor performance.

Nearly everyone knows that “catamarans can’t sail into wind”. There are many explanations and some theories but few real clear answers. When you ask the question: Why can’t catamarans sail into wind?” You get blinks and stares. I kept searching for the answer. And I found it. And from a surprising source. They can!

Most catamarans can’t sail into wind because they lack full a daggerboard. “Everyone” believed cats didn’t need daggerboards because they were fast. A catamaran with a full daggerboard points better than racing monohulls. But lacking daggerboards means they can’t counterbalance the sail force of the wind. This forces strain on the rudder and relatively poor performance.

Way back in 1997, a young Tim Weston built his catamaran from a kit. He said “catamarans have earned a reputation of being not very good at going to wind. When I first got in the water I was also not impressed. I started taking measurements of speed and wind angle and sat down to study the situation.” He spent months looking over his data.

Why Catamarans Can’t Sail Into Wind?

“I decided that the reason cats don’t go to wind as well as monohulls is that they simply don’t have enough keel area. And not only that, the cord of the daggerboard is too short. The only reason I could think of as to why catamarans have such small daggerboards is because of their reputation. That might hold true when the boat’s moving fast, but as soon as you slow down, you have a problem.” People believed that because cats were faster, you didn’t need as much area to create the same amount of lift. This turned out to be wrong.

Why Catamarans Can't Sail Into Wind 1
Why Catamarans Can’t Sail Into Wind? People believed that because cats were faster, you didn’t need as much area…

“It means you have to move fast all the time, otherwise your board is too small. For a cruising boat or even a racing boat, when you slow down, you lose your grip on the water. When you’re going to wind, most of your sail force, is pushing the boat sideways. When you want to go forwards, you have to counter that force.

“If you look at the forces that’s pushing the boat forwards is directly proportional to the reaction to the sail force. if you can’t create a reaction to the sail force, you just go sideways. you can have the biggest and most expensive rig out there but if you don’t have a daggerboard that counters that force, you’re wasting your money.

People believed you didn’t need as much area

“I also asked myself why I need two boards. a lot of the drag created by a keel is from the tip losses around the end of the keel. by having two boards I had increased that. I also couldn’t imagine that isometric drag would be big enough to create a problem. when I sail with one or the other board down originally, I couldn’t see any difference. also by combining the two boards into one I could create a board that had more cord. which to me was important.

Why Catamarans Can't Sail Into Wind 2
Why Catamarans Can’t Sail Into Wind 2. This foil which was 150 percent bigger than the original two foils combined.

“So I was making a keel the same as on a yacht. I sat down and designed this foil which was 150 percent bigger than the original two foils combined. Five metres long and weighed about 150 kilos.

The Surprising Answer

“It was a big job making it and retrofitting it into the boat, but when I finally run over the water, I couldn’t believe the difference in the boat. I’d created a completely new boat!” That went upwind like a fast tractor. “It pointed like the boat had never pointed before, but even more importantly was the speed that came with it.

“I could slow way down and still go upwind like a tractor. Or accelerate, I could ease off the wind slightly and the speed would just take off. where I noticed the difference immediately was in the steering. Before when I was hard on the wind the steering got really heavy.

“Now, it was like I’d added power steering.” There was no pull on the wheel because the daggerboard was doing its job and stopping the boat from going sideways.

The Full Explanation

Why Catamarans Can't Sail Into Wind 3
Why Catamarans Can’t Sail Into Wind 3. I had overtaken 80% of the fleet by pointing higher and going faster than the racing monohulls.

“There was no side loads on the rudder. All the rudders had to do was to pivot the boat around the center board. This meant, a small autopilot, that I’d originally fitted, that used to struggle when I was going to wind, was operating with no effort whatsoever.

“Having the ability to go to wind at slow speed in a catamaran is extremely important safety wise. this proved itself in the Pacific. I got into some really nasty weather. I was sailing on autopilot, basically as a solo sailor.

“The ability to be able to reef down and slow down and to be able to point and drive upwind at a slow speed is so important when you’ve got huge seas running, and it’s stormy you don’t want to go fast. It’s dangerous to go fast.

The Proof

“I wanted to get my head down and sleep while the boat continued on autopilot, and to be able to move slowly, but point really high with no slip in the water, without losing steering, because they’re under loads meant the ride was not any more comfortable and under control but I actually got to where I was going quicker anyway because I could move in the direction I wanted to go.

“I only raced the boat once. There were a hundred and twenty other boats mostly racing boats. The course was a triangle with two legs hard on the wind. In the first two legs, I had overtaken 80% of the fleet by pointing higher and going faster than the racing monohulls.

“Despite its size, there’s no isometric drag at all with the daggerboard. On top of that, you free up one side of the boat interior completely.”

Conclusions

Personally, I don’t like the appearance of daggerboards, on catamarans, or anywhere. I don’t like them up and I don’t like them reducing the water clearance below the boat. I don’t like the channels – up or down – taking up space on the boat.

People assumed that because cats were already fast, they didn’t need the force in the water to counter balance the effect of the wind. Therefore, they just removed the wing in the water. This trained the only things in the water, the rudders. This could be felt on the wheel and it was affecting the autopilot, too.

However, I clearly understand what Tim was saying. When the wind pushes on the sails, the boat needs something like a keel to counter that force. This is true for catamarans as well as sailboats. He proved his theory when he installed the extra long daggerboard. The wheel felt like it has power steering, the autopilot stopped struggling, and the catamaran was able to point into the wind as never before.

This allowed him to steer more directly where he was going. As a result, he got there earlier than planned. Besides, he was able to slow down his boat for safety and he was able to get some sleep as a result of the autopilot doing it’s job.

I hope this was helpful. If you have questions or want more information, please leave me feedback. I would be happy to do some research for you. I recommend that you watch Tim’s videos on how he made his catamaran and the daggerboard.

Sources:

https://www.youtube.com/watch?v=XN_onRqAc

https://forums.sailinganarchy.com/index.php?/topic/206228-over-the-horizon/

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