Daily Archives: October 24, 2011

Sailing Epicurus

A few days ago I posted a ‘first-look‘ about the new Trudeau Epicurus. It’s a nifty cat-boat that combines the simplicity of a single sail with the beauty and accuracy of Trudeau design.

I’m still looking at how the boat handles; there are lots of fun features to test out. That could take a while, so I thought I’d post a few basic Epicurus performance numbers and impressions so far… hopefully, there’s more to come. πŸ™‚

Control Cat

In case there are new sailors in the audience, let me restate a few basic features this boat shares with prior Trudeau releases. πŸ™‚

1. Epicurus can be sailed any way you want. You can use an onscreen HUD, chat gestures, or keyboard keys. Oh, and all your crew can help you sail too. πŸ™‚
2. Darn, you can even sail it by proxy. πŸ™‚ There’s a skipper notecard that lets you add your 1,000 closest friends who can borrow the boat. Just… well… don’t blame me when you login and find it beached someplace in Zindra. πŸ™‚
3. Speaking of notecards, there’s one for Settings. It lets you adjust everything from camera angle, to tiller style, to wind display and avatar position. You get to sail your way, and the boat remembers it after you crash.
4. Even the HUD has multiple control options that display the stuff you need to know, the way you want to see it.

Polar Cat

The above list is pretty standard for a Trudeau release, so let’s talk Epicurus- specific performance!

I usually baseline- test boats using a fixed, 5.0 m/s breeze. That setting reduces the influence of heel, hiking, or ‘reefing’ and makes it easier to get a baseline performance curve a sailor can compare with other boats. It also establishes a useful, no-frills reference to evaluate boat-specific performance features.

With that intro, let me show you the ‘boat speed vs wind angle’ curve for Epicurus, using a constant true wind (boat wind) of 5.0 m/s.

The figure below plots boat speed as a function of the real wind angle (RWA) in Red. As sailors know however, the apparent wind force is what actually impels a moving sailboat, so the chart below displays a second curve shown in blue. The blue curve plots Epicurus’ boat speed as a function of apparent wind angle (AWA), and it’s appropriately shifted windward from the RWA results.

The chart’s dual display reveals a few things about the new boat:

First, Epicurus’ sail begins to fill and generate thrust at roughly 40Β° AWA. When the boat is moving that corresponds to a fixed heading of roughly 52Β° RWA.
Second, the fastest point of sail is a beam reach of 50Β°-80Β° AWA (70Β°-100Β° RWA). If you own or sail a Trudeau boat, these numbers probably seem pretty familiar. πŸ™‚
Third, Epicurus has a maximum speed over ground (SOG) of roughly 40% RWS, and the shape of the response curve is fairly flat and forgiving; that makes Epicurus a serious and stable cruiser. Such a sail engine calibration is a tribute to the venerable cat boats of yore. They were designed and built to be simple, efficient work boats along the New England Coast.

GRIN. Of course, that never stopped anyone from racing them. πŸ™‚

Heeling, Reefing and Hiking

No surprise, Epicurus is full of realistic features that modulate performance; they should keep any sailor pretty fascinated. πŸ™‚

For example, look at the picture I posted at the top of this note. It shows my boat heeled way over, and it looks like I’m flying upwind on close haul. Actually, take a closer look, as detailed below.

On a windward heading in a stiff breeze, Epicurus will heel. When that happens, the sail becomes less efficient. A stronger breeze won’t necessarily get you going faster; you’ll need to also get skipper and crew to hike windward in order to bring the boat into better balance.

If you boat heels too far though, the rail goes under the water and yoiks, the boat grinds to a near-halt. πŸ™‚ It swamps as water fills the cockpit! The picture above shows Epicurus sailing into a 12.1 m/s wind with AWA 76Β°… It should be roaring ahead, but it’s actually going no-place! The boat speed is only 0.7 m/s. Although the sails are set optimally, the boat is on extreme heel and the rail is underwater. The reason it is barely moving is pretty obvious; the boat is full of water, it’s swamped!

You can fix this by hiking windward to level the boat. However, often that maneuver proves insufficient, even when you have several crew-members aboard to help you out by sitting on the windward rail.

At that point, when the wind is stronger than you are, you have to shorten sail; That’s when you need to Reef. OK, I know I’ve previously talked a lot about reefing in Trudeau boats, but live with it, here I go again. πŸ™‚ I like this feature!

In the Trudeau Twenty generation of TCY releases (Back when Bush was President), under high wind conditions and strong heel a sailor could reef and T20 would accelerate. Getting to a reef point was a racing mitzvah; the boat would suddenly take off, supercharged.

Well, Reefing in RL isn’t that simple. Reefing doesn’t actually speed up a boat. The maneuver just shortens sail and rights the boat; it keeps it from swamping or capsizing. However, no surprise, in real life that’s pretty important. It tends to keep the crew aboard alive, and allows them to forge ahead despite foul, heavy weather conditions.

Anyway, let me emphasize this point with the graphic above. In the left image, you see my boat heading windward against a strong breeze. It’s near the tipping point, heeling way over, and it’s about to fill with water. When that happens my boat will fill with water and stop dead,until the cockpit drains and I get going again. πŸ™‚ I’m skippering solo and I’m already hiked windward, so what can I do?

Well, the answer is obvious, and shown in the right-side image above: I can shorten sail. If you look at the numbers, reefing Epicurus won’t make you go faster; it shouldn’t. However, it will keep you upright in strong wind, and it prevents you from swamping your boat.

I admit it, I love this effect; it’s pretty subtle, but deliciously realistic.

It’s one of the things that makes Second Life Sailing worth Second Life Living. πŸ™‚

Anyway, I’ll post the rest of the numbers once I’m done having fun sailing this boat! πŸ™‚