Schooner Nina - MERGED 3 THREADS

[Astrid]

Actually a Quantas flt heard ELT but not our boat and Air Canada a couple of weeks ago located a bare boat. But they are extremely lucky.

If I recall, the Air Canada flight was asked to descend to about 1500m to have a look in the area where the beacon signal was picked up. From the normal cruise altitude 30,000-37,000 feet, passengers and crew of a commercial flight would probably not be able to see a yacht even if they knew where to look for it.

[Captain Bill]

Originally Posted by psneeld

I would be surprised if someone out there didn't have reasonable, real time data that could predict drift better than pilot charts.

The problem with drift data is that it is much like the weather. It is basically chaotic in nature, so small errors get magnified over time. It's why weather forecasts get worse the farther into the future you go. If they had started within a few days of when they disappeared and knew their position when they started drifting then drift models would have been fairly accurate, but now that two months have passed using the general models is probably as good. Since we don't know their exact position when they became disabled(if in fact they are) or took to the raft, there is just too much chaos in the currents and eddys out there to use them to make any sort of accurate prediction. The general models say the prevailing winds re from the W and SW, which would push them east and north east. Actual weather records for the last two months would be useful to the extent that they tell us if the winds were westerly than average or more southwesterly than average which would tell the searchers to look more northeast or more east. Either way after this much time the likely search area is huge.

[Friend of Nina]

Astrid you are correct! They did need to descend to locate.

Boatguy30... I think Fossetts wife used the news and wreckage wasn't there??

Cherie

[transmitterdan]

Originally Posted by Friend of Nina

Astrid you are correct! They did need to descend to locate.

Boatguy30... I think Fossetts wife used the news and wreckage wasn't there??

Cherie

Fosset's plane wreckage was found long after he was declared dead I believe.

[psneeld]

Originally Posted by Captain Bill

The problem with drift data is that it is much like the weather. It is basically chaotic in nature, so small errors get magnified over time. It's why weather forecasts get worse the farther into the future you go. If they had started within a few days of when they disappeared and knew their position when they started drifting then drift models would have been fairly accurate, but now that two months have passed using the general models is probably as good. Since we don't know their exact position when they became disabled(if in fact they are) or took to the raft, there is just too much chaos in the currents and eddys out there to use them to make any sort of accurate prediction. The general models say the prevailing winds re from the W and SW, which would push them east and north east. Actual weather records for the last two months would be useful to the extent that they tell us if the winds were westerly than average or more southwesterly than average which would tell the searchers to look more northeast or more east. Either way after this much time the likely search area is huge.

it all depends on the data...I'm not sure what and where is being measured and stored...that was really my point

[Captain Bill]

Originally Posted by psneeld

it all depends on the data...I'm not sure what and where is being measured and stored...that was really my point

Actually it doesn't. The fact is that there is no way to know where they are at this point with any sort off accuracy. It has simply been too long and too many variables have exerted themselves. You would have to know the exact position and velocity vector of every molecule of water that impinged on them. It simply can't be done. If you dropped two corked bottles in the water next to each other next to each other In a few minutes they would be separated by a significant distance. In a few days they might be a couple of miles or even tens of miles apart. In two months they might be more than a thousand miles apart. There is simply no way to tell. If I dropped these two theoretical bottles in the gulf stream off on Miami it is entirely conceivable that one might be in Bermuda and the other in Iceland after two months. There is simply no way to know. In general you could say they were likely to be north and east of where you dropped them. What is very likely is that they will be far apart. Long range weeather forecasts are the same way. The weather service can tell you that three months from now there is a 60% chance it will be warmer or colder than normal and that there is a greater or lesser chance that it will be dryer or wetter than normal. What they can't tell you is what the actual weather will be at any given point on a given day 3 months from now. It simply can't be done. The same is true for drift models. The futher out you go the more general it gets.

[boatman61]

Another thing that makes a search difficult is that we don't know if they're in a life raft or still on the boat... the boat will be driven by current to a greater extent than the winds... whereas the life raft is gonna be blown every which way and current models won't be much use...
0.000000000000001centimes

[Pelorus32]

Originally Posted by boatman61

Another thing that makes a search difficult is that we don't know if they're in a life raft or still on the boat... the boat will be driven by current to a greater extent than the winds... whereas the life raft is gonna be blown every which way and current models won't be much use...
0.000000000000001centimes

The work I've seen on life raft drift shows that both wind and current play a substantial role.

On the subject of commercial flights keeping an eye out, a number of things come to mind. I crossed the Tasman in both directions last weekend on a QF flight. Aus to NZ we were basically over a low stratus the whole way and saw nothing.

On the way back there were large sections of clear sky followed by a mid-Tasman trough and then a bit later the front that was following it. So about 50% clear skies for the trip. I watched the whole way that it was clear...and did not see a single vessel of any sort. However I did think about what I would do if I saw a sailing vessel. Call the cabin crew...explain to them...encourage them to talk to the pilot...they go and talk to the pilot...on and on. Easily 5 minutes has passed and we are travelling at 8 or 9 nm per minute so we are 40 or 50nm away. I still don't know just what it is that I saw from FL390...what is the pilot going to do?

On another path entirely. There's quite a lot of air traffic from Auckland to South America. They don't fly true GC routes. The rules require a vertex at 60S so that is the limiting latitude. They follow the GC course down to 60S or so, run along that latitude and then rejoin the GC at the other end and head north. It's the same travelling to South Africa from Australia. However that's still a long way south of where you would expect any drifting vessel to be.

[boatman61]

Originally Posted by Pelorus32

The work I've seen on life raft drift shows that both wind and current play a substantial role.
.

Where have you seen this 'work'...?
I think a large heavy sailboat with around 6+ft draft is going to follow the current more readily than the wind... less on top than down below... the winds got to work real hard to get her moving in a different direction.
However a life raft is more on top and less below with a flat bottom... just the hanging bags that are supposed to stabilize the thing and have a depth of around 2ft... it will also drift faster than the boat in wind being a damn sight lighter as well.
That's why you don't untie it till all are aboard else your standing on deck waving 'Bye Bye' as it heads for the horizon..
3 Commercial Ocean Survival courses lead me to my conclusions... the main function of the drogue is to stabilize the raft in seas.
But... I've been wrong before...

[Captain Bill]

[QUOTE=Pelorus32;1304176]The work I've seen on life raft drift shows that both wind and current play a substantial role.


I would expct that it depends on the design of the raft. Most open ocean life rafts have large stability bags that would tend ti increase the effect of current. Smaller coastal rafts without stability bag would be mostly at the mercy of the wind. I would think that Nina would have had a raft designed for the open ocean, but I don't know that for sure.

[la vida nueva]

Since we don't know their exact position when they became disabled(if in fact they are) or took to the raft, there is just too much chaos in the currents and eddys out there to use them to make any sort of accurate prediction. The general models say the prevailing winds re from the W and SW, which would push them east and north east. Actual weather records for the last two months would be useful to the extent that they tell us if the winds were westerly than average or more southwesterly than average which would tell the searchers to look more northeast or more east. Either way after this much time the likely search area is huge.[/QUOTE]

Seems like some great points. Thanks.

[David_Old_Jersey]

No expert on tidal drift or that region, but I would start by working out where Nina could not be (given both tidal drift and time) and then work my way in........will still be left with bloody large areas, but at least will be able to alert folks passing through those areas - needle in haystack though it is.........at best.

[Pelorus32]

Originally Posted by boatman61

Where have you seen this 'work'...?
[snip]

Some of the stuff is below. A quick search will reveal a plethora of other material.

http://www.ifremer.fr/sar-drift/en/p...res-leeway.pdf

[la vida nueva]

I really appreciate this information. Thanks, guys. I want to be one of the first people to shake the hand of each of these sailors when they are found.

Tim

[la vida nueva]

[QUOTE=Pelorus32;1304176] "I watched the whole way that it was clear...and did not see a single vessel of any sort. However I did think about what I would do if I saw a sailing vessel. Call the cabin crew...explain to them...encourage them to talk to the pilot...they go and talk to the pilot...on and on. Easily 5 minutes has passed and we are travelling at 8 or 9 nm per minute so we are 40 or 50nm away. I still don't know just what it is that I saw from FL390...what is the pilot going to do?"

One thing you could do is report it to the people who are searching. They would then evaluate whether it was good enough information to send a flight to check it out.