Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 24-03-2010, 11:16   #151
Registered User
 
Randy's Avatar

Join Date: Oct 2008
Location: San Diego
Boat: Searunner 31
Posts: 639
Quote:
Originally Posted by sailorbyfate View Post
This morning, Abby wrote the following:


I thought AIS was line of sight only. How could she pick up a signal a hundred miles away?
AIS operates on vhf frequency and that's why it's thought to be useful at line of sight distances. However as with vhf radio transmission range is often considerably greater than that. Also line of sight is referring to antenna height (freighter's antenna is up to 150' and a sailboat's is 45' up to 80' or more). There have been posts relating that in certain geographical areas vhf is reflected off mountain ranges, weather conditons also affect signal propagation so the signal range is variable.
These web sites that display AIS info are not whats used by shipping or AIS to function.
__________________

__________________
Randy is offline   Reply With Quote
Old 24-03-2010, 11:47   #152
Registered User

Join Date: Jan 2010
Posts: 19
An antenna 150' high "sees" a horizon about 14 nautical miles away. A sailboat with an 80' mast "sees" a horizon about 10 nautical miles away. So spotting a ship 24 nautical miles away would be no surprise. And since VHF waves will bend a little, 40 nautical miles would sometimes be possible. The nearest mountains are hundreds of miles away, below the horizon, so mountain reflections wouldn't be a factor. Until someone can show me what I'm missing, I'll assume Abby was speaking figuratively when she said "a hundred miles."
__________________

__________________
sailorbyfate is offline   Reply With Quote
Old 24-03-2010, 12:07   #153
Registered User
 
SvenG's Avatar

Join Date: Oct 2009
Location: Mexico heading South
Boat: Ericson 39B - Senta II
Posts: 1,169
Quote:
Originally Posted by sailorbyfate View Post
Until someone can show me what I'm missing, I'll assume Abby was speaking figuratively when she said "a hundred miles."
She wasn't.

I asked the same question here a month or so ago and found out that long range reception is quite possible due to atmospheric and other bounces.


-Sven
__________________
Senta II - http://www.Grenander.com/Senta_II/Blog/Blog.html
1977 Ericson 39B -- Hull # 216
SvenG is offline   Reply With Quote
Old 24-03-2010, 12:33   #154
Registered User

Join Date: Jan 2010
Posts: 19
That's interesting! Since AIS broadcasts are so short in duration, I would think that a transitory effect might allow AIS where voice would still be ineffective. Thanks for clearing this up.
__________________
sailorbyfate is offline   Reply With Quote
Old 27-03-2010, 00:28   #155
Registered User

Join Date: Jan 2010
Location: New Zealand
Boat: 44Ft Sloop
Posts: 112
Quote:
Originally Posted by sailorbyfate View Post
That's interesting! Since AIS broadcasts are so short in duration, I would think that a transitory effect might allow AIS where voice would still be ineffective. Thanks for clearing this up.
VHF is stranger than strange. I often pick up clear transmits from hundreds of miles away, yet can't get a local station from behind islands. Go figure.

Anyway. Does anyone know where Abby is at the moment?
__________________
dpex is offline   Reply With Quote
Old 27-03-2010, 05:33   #156
Registered User
 
Artful Dodger's Avatar

Join Date: Apr 2008
Location: Toronto, Ontario
Boat: 42 Passage CC
Posts: 177
Images: 7
Send a message via Skype™ to Artful Dodger
Here is a little update on Abby through one of my friends blogs Where Next? - More Engine Nonsense
__________________
The Artful Dodger
Passage 42 Centre Cockpit
Toronto, Canada
Artful Dodger is offline   Reply With Quote
Old 27-03-2010, 06:35   #157
CF Adviser
Moderator Emeritus
 
TaoJones's Avatar

Cruisers Forum Supporter

Join Date: Dec 2006
Location: Montrose, Colorado
Posts: 9,850
Quote:
Anyway. Does anyone know where Abby is at the moment?
I first saw her Day 63 report last night (Pacific Daylight Time), which hadn't been there earlier yesterday. It reports her 722 miles west of Cape Horn.

See: Abby Sunderland | Abigail Sunderland | Wild Eyes | Solo Circumnavigation | Shoecity.com Sponsor for the map of her locations on each of the daily reports.

TaoJones
__________________
"Your vision becomes clear only when you look into your own heart. Who looks outside, dreams; who looks within, awakens."
Carl Gustav Jung (1875-1961)
TaoJones is offline   Reply With Quote
Old 01-04-2010, 10:16   #158
CF Adviser
Moderator Emeritus
 
TaoJones's Avatar

Cruisers Forum Supporter

Join Date: Dec 2006
Location: Montrose, Colorado
Posts: 9,850
From today's Los Angeles Times, comes word that Abby Sunderland has cleared a big hurdle by putting Cape Horn in her wake.

* * *

Abby Sunderland rounds Cape Horn

The Thousand Oaks teen is cheered by her progress. But more challenges await as she tries to sail solo around the world.

Abby Sunderland prepares her 40-foot sail boat "Wild Eyes" in the harbor at Marina Del Rey on Jan. 12. (Al Seib / Los Angeles Times / January 12, 2010)

By Pete Thomas

March 31, 2010 | 5:14 p.m.

"Rain driven by freezing wind pelted her 40-foot sailboat, but Abby Sunderland was in remarkably good spirits early Wednesday afternoon.

"That's because the 16-year-old from Thousand Oaks, while friends back home were coming off a refreshing spring break, had just rounded Cape Horn between South America and the Antarctic Peninsula.

"She had safely traversed a passage known as the Mt. Everest of the yachting universe, a mariners' graveyard fraught with unpredictable gales and gargantuan waves.

" 'It's the milestone I've been waiting for,' the budding adventurer said, when reached via satellite phone, minutes after she had crossed from the Pacific into the Atlantic."

* * *

To read the rest of the story, go to:

Abby Sunderland rounds Cape Horn - latimes.com

TaoJones
__________________
"Your vision becomes clear only when you look into your own heart. Who looks outside, dreams; who looks within, awakens."
Carl Gustav Jung (1875-1961)
TaoJones is offline   Reply With Quote
Old 02-04-2010, 00:04   #159
Registered User
 
Stillraining's Avatar

Join Date: Oct 2008
Location: Puget Sound
Boat: Irwin 41 CC Ketch
Posts: 2,876
Atta way lass!
__________________
"Go simple, go large!".

Relationships are everything to me...everything else in life is just a tool to enhance them.
Stillraining is offline   Reply With Quote
Old 06-04-2010, 12:55   #160
CF Adviser
Moderator Emeritus
 
TaoJones's Avatar

Cruisers Forum Supporter

Join Date: Dec 2006
Location: Montrose, Colorado
Posts: 9,850
I certainly don't want to seem harsh, but it seems to me that either Abby or her router(s) have been correcting a little navigation boo-boo over the past few days. It appears that she was headed for the wrong end of the Falklands / Malvinas after rounding Cape Horn, then got sorted out to take the islands to port. This appears to have wasted two days.

See:Abby Sunderland | Abigail Sunderland | Wild Eyes | Solo Circumnavigation | Shoecity.com Sponsor

TaoJones
__________________
"Your vision becomes clear only when you look into your own heart. Who looks outside, dreams; who looks within, awakens."
Carl Gustav Jung (1875-1961)
TaoJones is offline   Reply With Quote
Old 06-04-2010, 13:08   #161
Registered User
 
Randy's Avatar

Join Date: Oct 2008
Location: San Diego
Boat: Searunner 31
Posts: 639
Yeah it seemed like they weren't actually looking at the weather forecasts. Often it's a survival or at least prudent thing to head north asap.
__________________
Randy is offline   Reply With Quote
Old 06-04-2010, 17:18   #162
Senior Cruiser
 
osirissail's Avatar

Cruisers Forum Supporter

Join Date: Feb 2009
Location: A real life Zombie from FL
Boat: Gulfstar 53 - Osiris
Posts: 5,416
Images: 2
Actually according to her blog the winds died and she was not able to keep on the northerly planned course, so she switched and went the long way around the south of the islands. Here is her post on it.
Quote:
Had a bit of a slow day today with no more than 4 knots of wind for most of the day. But at least it was warm and sunny! It got all the way up to 63 degrees today!! I had been routed to go west of the Falkland Islands and just get north fast. But with the wind angle I ended up with and my position I wasn't able to. I could have waited for the wind to shift but that wasn't going to be for awhile and then, not for long. So I decided it would be better to head back and go south of them. It's a longer way to get around them but at least I wouldn't be stuck too close to shore. Wild Eyes does not go to weather and being too close to shore can be very dangerous.
__________________
osirissail is offline   Reply With Quote
Old 06-04-2010, 17:51   #163
CF Adviser
Moderator Emeritus
 
TaoJones's Avatar

Cruisers Forum Supporter

Join Date: Dec 2006
Location: Montrose, Colorado
Posts: 9,850
Thanks for clarifying that, osirisail. I hadn't been reading her blog.

I know she has a couple of month's cushion in her quest to take the record from Jessica Watson (Jessica, born May 18, 1993 and Abby, born October 19,1993). She lost three of those five months she "was born with" by leaving on her record attempt some three months later than Jessica. The two months she has in hand are in addition to having a faster vessel, but if something breaks that will cost her time while effecting repairs, the loss of a day or two here and there could add up to a complete loss of her cushion.

If Jessica closes the circle by early May, Abby will need to sail back into Cabo San Lucas by early July to claim the record. This could be close.

__________________
"Your vision becomes clear only when you look into your own heart. Who looks outside, dreams; who looks within, awakens."
Carl Gustav Jung (1875-1961)
TaoJones is offline   Reply With Quote
Old 07-04-2010, 19:54   #164
Registered User

Join Date: Jan 2010
Posts: 19
You're overthinking the math. Abby is 5 months younger than Jessica, so if she finishes less than 5 months after Jessica, she'll have the (unofficial) record. Assuming Jessica finishes by around May 1, Abby could finish as late as Oct 1 and still claim the record. Finishing by Oct 1 is the least of Abby's worries. If she does finish without stopping or getting assistance, it is near certain she'll have the record.
__________________
sailorbyfate is offline   Reply With Quote
Old 07-04-2010, 20:12   #165
Senior Cruiser

Cruisers Forum Supporter

Join Date: Mar 2009
Location: Houston
Posts: 149
Quote:
Originally Posted by TaoJones View Post
I certainly don't want to seem harsh, but it seems to me that either Abby or her router(s) have been correcting a little navigation boo-boo over the past few days.
Quote:
Originally Posted by TaoJones View Post
I hadn't been reading her blog.


An interesting combinations of posts.

~
__________________

__________________
Jim D is offline   Reply With Quote
Reply

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
If Jess Shouldn't Go, then Neither Should Abby Factor Cruising News & Events 2 21-10-2009 09:11
Zac Sunderland arrives @ Mauritius Amgine Cruising News & Events 0 15-11-2008 00:41



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 07:43.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.