Please select your home edition
Edition
Henr-Lloyd BLU LEADERBOARD

How DOES a sailboat go faster than the wind?

by Des Ryan on 2 Mar 2009
18ft Skiff - faster than the wind Frank Quealey /Australian 18 Footers League http://www.18footers.com.au
One of the intriguing aspects of sailing is that a sailing boat can actually sail faster than the wind, given the right conditions. While even a novice sailor soons learns that this is possible, many a very experienced sailor can't really explain the physics of it.

If this applies to you, then read on:

Sailing ABC's:
The fundamental principle of sailing is quite simple: the sails catch part of the wind, send that energy down to the hull, and this drives the vessel forward. But in practice, it’s far more complex a process. Effective sailing is all about how well the sailor balances three basic forces that act on a sailboat as it moves forward. First there is the driving force, caused by the wind flowing across the sail; constant trimming of the sails is required to maintain the small angle to the wind and make the best use of this force. Working against the driving force are the sideways force and the heeling force. The key is to find the ideal trim for the sails to maximize the driving force while minimizing the sideways and heeling forces. The best way to do this is to let the sail out so it flaps in the wind, then pull it back in until it only just stops to flap and generate the perfect drive.

Forces Face Off:
The sideways force results because the wind pressing into the sail doesn’t just spread in the forward direction, but also off to the side; the faster the boat is moving, the smaller the sideways force. The same force that the wind presses into the sale also gives rise to the heeling force, acting upon the hull to heel the boat. The boat’s keel and the weight of the load serve to counter the heeling force and prevent the boat from capsizing, especially during challenging upwind manoeuvres.

Outracing the Wind:
Lots of boats can sail faster than the wind -especially 18-foot skiffs. Ask a skiff sailor how, and he'll say that these boats are so fast that they make their own wind. This is true.

But ask a physicist, and she'll say that it's just a question of vectors and relative velocities. Downwind is easy. If the wind is 10 knots, and the boat makes 6 knots in the same direction, then the crew feels a wind of 4 knots coming over the stern of the boat. The true wind equals the speed of the boat plus the relative wind. As the boat speed approaches the wind speed, the relative wind drops towards zero and so there is no force on the sail. So you can't go faster than the wind.

When the wind is at an angle, we have to add vectors representing these velocities. The faster that the boat goes, the greater the relative wind, the more force there is on the sails, so the greater the force dragging the boat forwards. So the boat accelerates until the drag from the water balances the forward component of the force from the sails.
X-Yachts AUS X4 - FOOTER - 3Rooster 2020 - Impact BA - AUS FOOTERGet My Boat 2021 FOOTER

Related Articles

Mixing it up
A few sailing events which are a bit 'out of the norm' As we head towards the end of September, I've been thinking about which events, and days out sailing, have been the most fun this year. There are a few to choose from, and overall it's been a good year for time on the water.
Posted on 21 Sep
An exciting 52nd edition of La Solitaire du Figaro
Now heading for 2022! 'Where legends are born!' is the strapline of La Solitaire du Figaro. One reason that legendary sailors are made and crowned on the La Solitaire du Figaro is the magnitude of the challenge.
Posted on 21 Sep
The Vendée Arctic - Les Sables d'Olonne 2022
The first qualifying stage for the Vendée Globe 2024 The SAEM Vendée, the organisers of the Vendée Globe, will also organize the "Vendée Arctic - Les Sables-d'Olonne" which will be the first qualifying stage for the Vendée Globe 2024. The "Arctic Vendée Les Sables-d'Olonne" will leave from Port Olona
Posted on 21 Sep
Figaro Beneteau 3 – Quintessentially French
Can the Figaro Beneteau 3 be summed up in a headline or just one or two sentences? Maybe... She's quite happy to slap you back and forth across your face, or go off and sulk at a corner table with an espresso martini and deliver you scorchingly deathly stares.
Posted on 21 Sep
2021 Hempel Mixed Two Person Offshore Worlds Leg 2
Team ESP have taken an early lead in the Adriatic Sea Team ESP have taken an early lead in Leg 2 of the 2021 Hempel Mixed Two Person Offshore World Championship in Italy. The 10 boat fleet of Figaro 3 keelboats started out from Bari at 0800 hours this morning on a 300-mile leg through the Adriatic Sea.
Posted on 20 Sep
11th Hour Racing Team at Le Défi Azimut
The team experiences highs and lows at the event Victory in the Speed Runs and the runner's-up spot in the double-handed 48-Hour Race were the highlights for the US-based 11th Hour Racing Team, as it competed with two boats in the Défi Azimut regatta in Lorient on the French Brittany coast.
Posted on 20 Sep
Italia Sailing Team enters The Ocean Race 2022-23
The goal is to give Italian tourism a further boost and enhance the Made in Italy brand During a press conference organised by the Yacht Club Italiano on Sunday evening, the Italian Minister of Tourism, Massimo Garavaglia, gave his full support for an Italian entry in the next edition of The Ocean Race, scheduled to start in late 2022.
Posted on 20 Sep
49er, 49erFX and Nacra 17 Europeans overall
Staniul & Sztorch narrowly win 49er Euros in a first for Poland Mikolaj Staniul with Kuba Sztorch (POL) won a tit for tat battle with Tim Fischer with Fabian Graf that played out over two 49er gold races on the final day in Thessaloniki.
Posted on 20 Sep
Gladwell's Line: Irish caned over Cup indecision
Irish media cane Ministry of Sport bureaucrats over "indecision" on AC37 hosting The Irish editions of the weekend and Sunday newspapers have taken the Ministry of Sport bureaucrats to task over their "indecision" on the America's Cup hosting bid for Cork.
Posted on 20 Sep
Défi Azimut - A proper contest and a worthy winner
You could hardly hope for a more dramatic race You could hardly hope for a more dramatic race packed into less than two days at sea than we saw in the Défi Azimut-Lorient Agglomération 48-Hours classic, a contest that tested crews and produced another stellar performance at the front by APIVIA.
Posted on 20 Sep