What kind of boat can sail closest to the wind?

Hi guys,

After this season of sailing, when I had to beat upwind through extremely narrow lake passages, my boat struggling through 100 degrees on each tack, I got curious. It is quite obvious that not all boats can beat upwind at the same TWA (True Wind Angle). Mine does 50 degrees at it's best. What it means is that it can sail higher than that, but the speed drops and the leeway increases too much, so my best VMG (Velocity Made Good) happens to be at around 50°. I think that usual Marconi rigs do 40-45°, some racing boats reach 35°. I recon that IACC (Internation America's Cup Class) used to sail as close as 28° to the wind. The curious thing is that multihulls have a very large TWA, but wonderful VMG, because their insane speed makes up for that large angle.

So it is obvious that the VMG is more important measure of upwind performance than TWA. However, in some cases, it is more important to be able to have a boat that reaches it's best VMG when sailing very closely to the wind, that is, at low TWA. For example, when sailing (or even racing) in narrow passages, docking, maneuvering in tight spaces, or many other cases.

So I wonder, what kind of sailboat can sail closest to the wind? IACC does 28°, which sounds amazing. Is there a boat that does it's best VMG at 25°? 20°, maybe? Is there a record?

I also wonder what kind of hull and rig would be best for sailing so close to the wind. Near-flat, high-aspect rig and a slender hull with a very effective, low-drag board to negate drift seems logical. But then again, catamarans have all these features (if you neglect the windward hull that's lifted out of the water), yet surprisingly, their best VMG is at a very large TWA angle, opposite of what would be needed in, for example, sailing fast in a river. So there must be more factors at play here.

I look forward to your opinions, and the boats that could act as an example. I put a lot of effort into searching any information and discussions on this very specific topic, but found little yet... Time to fill the gap.

 

Perhaps counter intuitively, to point really high you must also go rather slowly, otherwise the apparent wind comes back too far. That's why the really fast boats have quite a wide angle. The IACC ones are going to be well up on the list because they have:
- really efficient rigs above the water
- really efficient foils underwater
- really low drag hulls
- so much lead that they cannot actually sail very fast upwind for their size.

The thing is though, if you are in a very high performance boat that gets its best vmg at quite a wide angle, then you do have the option of slowing it down and pointing at the moon. Its rather handy if you have narrowly misjudged the approach to a racing mark and need to sneak around. The only caveat is that the daggerboards/whatever on high performance craft are relatively small, because they normally have plenty of water flowing past them, so if you point too high and too slow the daggerboard flow may stall out, which leaves you in irons and in an attitude that's rather difficult to quickly recover from.

 

Ice yachts get a pretty tight angle of apparent wind......

 

Interesting point. But then again, pointing ability is one of the most desirable things to consider when getting/designing a boat.

As far as I understand, when the apparent wind comes up, you have to sheet in and flatten the sail to prevent it from stalling. The more it is sheeted in, the lesser the forward (driving) force vector becomes, and the sideways force increases. Logically, the boat that can sail very high up must be able to resist leeway without creating drag that would reduce forward momentum. So either the boat must be still sailing pretty fast for high-aspect board to have enough flow to work with, or the boat must have a low-aspect, wide board that would work better in slower speeds. And still have it's best VMG while doing so.

Ice boats... Curious things. Why are they able to point so high?

 

all of the best pointing boats have highly refined sloop rigs, with really large jibs.

IT seems to me that a single large sails, a cat rig, would be most efficient, but it is necessary to have a jib to get the angle. I think the jib keeps the flow attached at high wind angles over the mainsail.

A very efficient foil shaped keel is a must too.

 

Yes, that's what I noticed too. But then again, I wonder, what are the record-holding sailboats in terms of lowest TWA with their best VMG? Are there any that can point higher than IACC does?

 

As mentioned in order to sail really high to the TWA you really need to slow the boat down to keep the apparent wind from shifting so far forward. But if you are just worried about vmg and not just TWA then there are some characteristics that can be pretty easily defined.

A Uni-Rig like the A-Class Catamarans or M-32
Rotating wing mast (wing masts are better but far more difficult to deal with)
A very efficient hull shape with a long narrow design
High aspect, low drag foils
Square top sail

Basically a bunch of drag reduction stuff combined with a very easily driven hull design. Then you need a lot of ballast to keep the boat flat.

 

Large jib not required

Pointing ability is really important in racing. It is often very detrimental to be sailing low in large fleet.

Etchell 22s have a small jib and have very low tacking angles. They have large keels, tight sheeting angles and low drag both above the water and below water. You never want to be above an Etchell because they point so high and willwind upon your bow really quickly. Watch them on flat water. Put them in slop and light wind and they will not point high but then again no boat will.

12 metre yachts could also sail at very tight angles in flat water. I have a great shot of Australia 2 and Liberty sailing at about 70 degrees apart on oppsite tacks. Large keels, low drag and great sails.

Pointing ability is as much about drag as other factors. If you tow a dinghy upwind or put a three bladed prop on the boat you lose height. This is because drag feeds straight into pointing ability.

 

If you allow parts of the rig to move (in practice, this means a wind turbine), you can sail at zero degrees to the wind, albeit slowly. Several videos on Youtube.

I remember a TV program in the 80s where a catamaran was built, with a turbine, which achieved about 1 knot directly upwind. Even with a turbine, it would be faster to tack (i.e. higher VMG, in yacht parlance).

 

So you're saying with zero angle of incidence, you can still generate lift with a sail plan. I'd recommend you file for patent now, before the word gets out.

 

No, what I mean is that the boat itself is at zero incidence (i.e. directly upwind), but the turbine blades can be at whatever angle you like. The turbine is used to drive a propeller, either mechanically or maybe electrically.

No need to patent -- loads of prior art by other people. Have a look at this design (sadly you can't see it going directly upwind):

https://www.youtube.com/watch?v=IzGCYaJbf0A

The project failed commercially, but it did work.

Also have a look at these dutch land yachts -- you can see several going directly upwind (turbine is facing directly into the wind):

https://www.youtube.com/watch?v=KQu4hUKnoVE

And this, which solved a famously tedious internet argument:

https://www.youtube.com/watch?v=F7PNSyAfCjk

 

I suspect this answer is going to bug a lot of people, but all else being equal, the boat with the lower total drag angle (sum of aero drag angle and hydro-drag angle) will have the potential to sail faster and have its VMG at a higher angle, not lower. The old 12 meter AC boats weren't just high pointing, they were damn fast in 5 knots of wind. So to point higher and go faster, improve the L/D ratio of the entire aero package and/or the entire hydro package.

Of course, the L/D ratios aren't constant. The aero L/D changes with apparent wind angle. The hydro forces have to balance the aero forces. And the hydro L/D depends on those forces and true speed. So often, achieving the last bit of potential at the highest pointing angle is just traded-off for better all-round performance. Smaller foils and a shallower draft are good everywhere except that last couple of degrees of windward ability. And they are cheaper, too.

Oh, and the easiest way to point higher is to leave prop in gear

 

actually the question is a curios one, if you design a boat to point highest it will not likely perform well in other areas.

is your objective to just point at as high and angle as you can, or to make the best time up wind? These will results in different designs. And fastest around a given course may favor a different design again.

For example, the highest pointing boat may not be the fastest one up wind. I know that usually sailing down wind at an angle, and jibing back and forth, usually results in going faster than just going straight down wind.

The fastest sailboat from one point to another is almost never a straight line. Overall one hopes to make both route choices, and boat design choices, to get through a course as fast as possible. Each alternative gives different performance benefits and disadvantages.

 

I think the simplest answer is very tall and very deep.

The boat should have a tall Bermuda Main and maybe no jib at all.

I noticed my Siren 17 pointed higher without the jib than with it. But it had a crappy jib that was supposed fly on its own wire, so it could be 'spool reefed'. It was very hard to get it to set right, and this usually meant sailing a few more degrees off the wind.

When I say deep, I mean it needs a very deep, short keel, probably with a bulb on it, which contains all or most of the ballast. The rudder should resemble the keel in being short and deep too. Both should have proper foil sections.

Because the boat will be moving slower upwind, the keel needs to larger than usual in total area. And this usually means making it even deeper, to get that extra area.

The hull would be heavy, at least for its Beam, so it has the momentum to smash through a chop, or maintain way, if the wind heads up for a short while.

The 19th century way of doing it was to have a massive long keel, that was much deeper than usual, have deep "V" like section in the Hull, have very low free board, and have a very large main sail.

Those boats were built long before the airplane was invented, so their characteristics came about by simple evolution, with little or no understanding of the aerodynamics involved. But they were able to recognize what worked better than the last time, so exaggerated those features.

I think the key lesson here is to have a LOT of lateral area, along with good balance, if nothing else. Then make the sails quite flat.

Doing so may rob them of power, but will give them lift at a tighter angle to the wind.

But really.

All this trouble just gets you ever diminishing returns, while compromising the usefulness of your boat in other points of sail.

I once sailed my Siren 17 up a 40 ft wide channel, dead upwind, even with its crappy jib. People came out of their cottages to watch me and my good friend do it. Our secret was a lot of well executed short tacks, where we knew exactly what the boat was going to do each time. We even had to back the jib to make sure the bow came through the wind. The boat was that much of a pig, due to its Beam, high sides and cabin, as well as its light weight.

 

Already been sorted in New Zealand decades ago apparently...
https://books.google.com.au/books?i...v=onepage&q=windmill boat new zealand&f=false

Jeff.