The Death Zone

[IshmaelHatesThatDamnWhale]

Following the Artemis AC72 capsize there has been a lot of talk about the "death zone" by a lot of people who don't seem to have a clue what it's all about. The death zone is the transition during the bear away from going upwind to downwind on an ultra-high performance boat like a beach cat, skiff, or AC72. The reason this is know as the death zone is because when a really fast boat bears away, the apparent wind speed increases a huge amount, putting a large load on the sails and foils as the boat accelerates like a mofo. The sail plan also tries to push the bow down during the bear away, hence the reason why skiffs and multis tend to pitch pole during the bear away. The key to a good bear away is getting through the death zone as quickly as possible, but the driver and trimmers need to be on the same page. It's not like a keel boat or even a dinghy where you just ease the sheets and turn. The death zone is also very hard (nearly impossible) to sail in on a skiff. They do not like to jib reach, plain and simple. You either get to go upwind or downwind, otherwise there is too much apparent windspeed and not enough stability (mostly speaking from Aussie 18s), ending in either a pitch pole or digging a rack and cartwheeling. Long story short, anyone who thinks that a bear away in 25 knots on a high performance boat should be as simple as just turning doesn't have a clue. Here is a quick video from my friends on a 1994 Grand Prix Aussie 18 failing at a bear away. That particular boat is a major PITA to sail because it has massive racks and "rack runners" to support them. You can see the mainsail hitting the runners, which helped seal their fate. With all this said, I'm going to go sail an 18 today in honor of a great sailor who lost his life on the cutting edge of this sport.

 

[Raz'r]

and an I14 going down the mine. Notice how high some of the boats are going around the offset mark. They do it specifically to avoid the "zone"

 

[BalticBandit]

Well its not so much that there is "too much apparent wind" in the "death zone" (ie close reach) on a skiff, it is more that the changes in AWA due to transitioning in and out of puffs at roughly every 2-3 seconds are so great, its almost impossible to trim to. Thus it is very easy to end up overtrimmed (pitchpole) or undertrimmed (teabagged) . Obviously Teabagged is preferrable, so you will see a lot of skiff skippers do exactly that in the bearaway lest they go the other way since a slight teabag can be recovered. But in these monster cats, that's not really an option so you gotta stay ontop of the trim at a rate that is essentially impossible to do

 

[Mark K]

I don't think you can trim a way around it. What might work is spoilers.

 

[Grrr...]

But in these monster cats, that's not really an option so you gotta stay ontop of the trim at a rate that is essentially impossible to do

Really? Impossible?

Funny. You better tell the sailors that, because I'm pretty sure that they've done it on 72's and their smaller cousins hundreds and hundreds of times.

Top Fuel dragsters are inherently unsafe. Wingsuits are inherently unsafe. Base jumping is inherently unsafe. Hell, judging by the serious injuries that have been incurred, Football and Hockey are inherently unsafe too. So is mountain climbing. Yet people continue to perform all those unsafe activites because they love them.

Back to the original post, I agree sailing will never be mainstream. That's no reason not to push as hard as we can to reach the technological pinnacle of the sport. But an uninformed article by someone who is clearly trying to overstate the point using terms he doesn't fully understand is really pretty pointless.

 

[mustang__1]

the other factor is that any leeward heel is going to essentially cause the rudder to create positive lift - effectively lifting the transom and creating downpressure on the bow. i dont know how you deal with that on a multi... the trick to the bear away is that it needs to be right. its not necessarily a matter of doing a bat turn to get downwind quick so much as it is timing the waves and the trim and the acceleration.

 

[rgscpat]

Is it even possible to re-design bows so that they are less likely to dig in and trip the boat without changing their wave-cutting character or slowing the design?

Is it possible to instrument the AC72 hulls to learn more about what stresses they're seeing?

 

[mustang__1]

Is it even possible to re-design bows so that they are less likely to dig in and trip the boat without changing their wave-cutting character or slowing the design?

Is it possible to instrument the AC72 hulls to learn more about what stresses they're seeing?

the best solution would be T-foil rudders. I seem to recall reading that the rule explicitly disallows them, though?

 

[Raz'r]

yep, no movable foils on the rudders

 

[??????????]

Bearing away in a good breeze. Bows dig in. Boat slows. Rig loads up. Catastrophic beam failure (seems like that was how it happened).

Time to de-tune the boats to be able to handle such conditions. Be it smaller wing masts - or maybe back to soft rigs. Increased scantlings, construction specs. Stronger (and heavier) boats as a result. Boats will be slower but less chance of disaster.

Time for the AC guys to do it before the government steps in and somebody who knows nothing about sailing makes the rules - at least for the US.

This is where the "gung-ho" "blood & guts" wankers step in and flame the idea.

 

[Mark K]

Spoilers. Maybe only the upper third of the wing.

 

[billy backstay]

Is it even possible to re-design bows so that they are less likely to dig in and trip the boat without changing their wave-cutting character or slowing the design?

Is it possible to instrument the AC72 hulls to learn more about what stresses they're seeing?

Probably, look at al the sensors on F1 cars. But I don't think you can depower a wing like you can blow the sheet on a fabric mainsail or kite?

 

[Pete M]

"Following the Artemis AC72 capsize there has been a lot of talk about the "death zone" by a lot of people who don't seem to have a clue what it's all about."

thanks Ishmael, I was going to write something myself.

in the days before the Bieker T-foil, the International 14 was nearly impossible to turn downwind in big conditions. we would sail upwind way past the top mark waiting for a lull. One time the Columbia river nearly killed me - we never did get to the bottom mark after a capsize on the downwind.

but I always heard it called "zone of death"

 

[Haligonian Winterr]

I agree that the boats need to be stronger, although I don't necessarily agree that this should be an example. The article states (as much as I hate to say that) that Artemis had already had issues with that beam, and other structural components.

I think the teams are more than capable if testing loads and building to those loads, but everyone makes mistakes and not every second of sailing can be predicted by a load cell.

Do I think we should wait until more sailors die to beef up the boats? Hell no. I think they should beef up the boats so the sailors don't have to worry about breaking a spar while trying to sail the course (or train).

0.02c

HW

Bearing away in a good breeze. Bows dig in. Boat slows. Rig loads up. Catastrophic beam failure (seems like that was how it happened).

Time to de-tune the boats to be able to handle such conditions. Be it smaller wing masts - or maybe back to soft rigs. Increased scantlings, construction specs. Stronger (and heavier) boats as a result. Boats will be slower but less chance of disaster.

Time for the AC guys to do it before the government steps in and somebody who knows nothing about sailing makes the rules - at least for the US.

This is where the "gung-ho" "blood & guts" wankers step in and flame the idea.

 

[??????????]

A successful yacht designer and professor of aeronautics, once told me that in spite of all the ways & means of measuring loads on structures such as aircraft and yachts, there will always come a time when a load previously unexpected will be applied - somewhere. More particularly applies to sailing.

PS. With aircraft there is a safety margin by legislation. Not so with boats where the attitude is still what Ben Lexen stated- "If it doesn't break, it's too heavy. If it does break, it wasn't strong enough"

 

[Countryclub]

With all due respect to Webb Chiles I do not think he has any current sailing exprience that would apply to anything like an AC 72/ 45, I-14 etc so he can STFU any time now. Anyone who wants to know about sensors and datalogging on the big cats and tri's should go review some back issues of Seahorse lots of good information there from the Oracle program last cup series. As for spoilers on a wing rig one of the by-products of spoilers is drag.....it would be interesting to see what the vectors look like in a wing sail vs. aircraft scenario. Speaking with someone who has done some sailing on the AC cats and Tri it was mentioned that one is very cognzent of the load paths and that some places on the boats are safer then others. . . .RIP "Bart".

 

[fastyacht]

Bearing away in a good breeze. Bows dig in. Boat slows. Rig loads up. Catastrophic beam failure (seems like that was how it happened).

Time to de-tune the boats to be able to handle such conditions. Be it smaller wing masts - or maybe back to soft rigs. Increased scantlings, construction specs. Stronger (and heavier) boats as a result. Boats will be slower but less chance of disaster.

Time for the AC guys to do it before the government steps in and somebody who knows nothing about sailing makes the rules - at least for the US.

This is where the "gung-ho" "blood & guts" wankers step in and flame the idea.

When did the govmt step into NASCAR or F1 or Indy? Why would they need )or want!) to step into this?????

 

[Bruno]

As has been pointed out before, these boats are not inherently deadly, other than being quite fast and having powerful platforms. What makes them deadly dangerous are the weight and moveable appendage rules in particular, the rules in general. Now that we have seen a tragedy there may need to be a rethink but that would inherently change the playing field in someone's favor.

Look at the uproar recently over adding legs: conspiracy, dirty trick, as bad as Bertarelli, scoundrels, etc.,. Given that it was M&M and TNZ who have stretched (in what should have been a predictable path) the rules to include fully foiling, which they were designed to prevent AFAIK, then complained about being disadvantaged by any underhanded rules changes, one has to wonder what will be their position as the opinion leader amongst the challengers.

What probably would prevent some of last week's mayhem would have been to have allowed four controllable lfting appendages at all times and required heavier scantlings and rigs. There will never be a safety guarantee but this would change the envelope away from impossibly difficult (perhaps) to race in full on Sf conditions (what if they actually had a dozen contenders fleet racing up cityfont, imagine that for a monment, all thos who decry the lack of participants) to more controllable but still exciting racing.

But that might cause delays, and any change will benefit some more than others. And there is no preventing bad judgement or engineering in a development class like this. But it might reduce some of the uncontrollable moments.

 

[??????????]

Bearing away in a good breeze. Bows dig in. Boat slows. Rig loads up. Catastrophic beam failure (seems like that was how it happened).

Time to de-tune the boats to be able to handle such conditions. Be it smaller wing masts - or maybe back to soft rigs. Increased scantlings, construction specs. Stronger (and heavier) boats as a result. Boats will be slower but less chance of disaster.

Time for the AC guys to do it before the government steps in and somebody who knows nothing about sailing makes the rules - at least for the US.

This is where the "gung-ho" "blood & guts" wankers step in and flame the idea.

When did the govmt step into NASCAR or F1 or Indy? Why would they need )or want!) to step into this?????

AC isn't NASCAR and you don't have F1 over there.

Didn't the CG "step in" after the Low Speed Chase incident?

Of course you can carry on as if nothing happened, but don't whinge if they do get involved.