Cruisers Forum
 


Join CruisersForum Today

View Poll Results: Wave Height Decider
+2m Seas if it is a short wave period 5 14.29%
+3m Seas if it is a short wave period 14 40.00%
+4m Seas if it is a short wave period 3 8.57%
+5m Seas if it is a short wave period 2 5.71%
I would hold position at sea anchor or hove to and wait it out 11 31.43%
Voters: 35. You may not vote on this poll

Reply
 
Thread Tools Rate Thread Display Modes
Old 14-01-2011, 15:34   #16
Senior Cruiser
 
atoll's Avatar

Cruisers Forum Supporter

Join Date: Mar 2010
Location: gettin naughty on the beach in cornwall
Boat: 63 custom alloy sloop,macwester26,prout snowgoose 37 elite catamaran!
Posts: 9,310
Images: 75
on another note,in the same vein,weather systems tend to go in 10 day cycles,so given a high or low pressure system producing stronger winds,as the thing passes the winds will back after about three days allowing you to gain any thing you lost by bearing off or hoving to ,allowing you to point higher and recover lost ground.
__________________

__________________
my catamaran building project updates http://www.cruisersforum.com/forums/...36#post2502136
atoll is online now   Reply With Quote
Old 15-01-2011, 18:48   #17
CF Adviser
 
Pelagic's Avatar

Cruisers Forum Supporter

Join Date: Oct 2007
Boat: Van Helleman Schooner 65ft StarGazer
Posts: 6,880
Quote:
Originally Posted by Laidback View Post
Reload this Page Poll: Wave Height . . . When Would You Turn Around ?

Before it is too late to avoid.

Good point Laidback … While it seems like the obvious default answer, I should have added that, but I don’t know how to edit the poll.

I find the problem with these disorganized Lows is that they don’t really grab your attention with tight pressure gradients indicating strong winds but they can make for miserable squally seas that stay in your path for a long time......More a problem for small craft than commercial ships


From experience, (my own and others) we tend to test these fringe conditions hoping that it will pass our “made” position in a reasonable time since 20 to 25 knot winds are not generally a big threat… It is more the Sea State, which really requires actually being there in a mid ocean scenario to find out.

After a couple of days of unchanging conditions and forecasts showing the large disorganized Low still hanging around, in front of us we start to question ourselves as Don suggests

What I am trying to poll is: what height of these short seas, given a slow moving system, would you decide to turn around to take a long delaying loop away from troubled waters?

Alternately, decision to lay to a parachute for perhaps up to a week?
__________________

__________________
Pelagic is online now   Reply With Quote
Old 15-01-2011, 20:57   #18
Registered User
 
capnorv's Avatar

Join Date: Sep 2010
Location: Bainbridge Island Washington on the Salish Sea
Boat: Hardin 45 Voyager Alice B., Gig Harbor 10, Orca 7 1/2 sloop, 16' sea kayak
Posts: 364
Images: 1
I went across the Columbia bar in short fetch 25-30 footers once in a freak, think it was about 1970, won't do that again. The results of that one was a completely gutted cabin on a 20' Chriscraft, 7 boats lost, and a dream to join the CG when the 40' surfed by seeing if we were OK. But then that wasn't after 11 days out, so I guess it doesn't count
__________________
capnorv is offline   Reply With Quote
Old 15-01-2011, 21:40   #19
Moderator Emeritus
 
hummingway's Avatar

Cruisers Forum Supporter

Join Date: Jan 2010
Location: Gabriola Island & Victoria, British Columbia
Boat: Cooper 416 Honeysuckle
Posts: 6,933
Images: 5
Quote:
Originally Posted by capnorv View Post
I went across the Columbia bar in short fetch 25-30 footers once in a freak, think it was about 1970, won't do that again.
Holy crap!!! Your keel must have been just about plowing a furrow in the bottom.
__________________
“We are the universe contemplating itself” - Carl Sagan

hummingway is offline   Reply With Quote
Old 18-01-2011, 04:09   #20
Registered User
 
SurferShane's Avatar

Join Date: Nov 2009
Location: NSW AUSTRALIA
Boat: L. Francis Herreshoff Ketch
Posts: 1,129
Images: 45
Question Swell v Sea?

The “wave” thing is a bit confusing. Instead of using the word “wave” we really need to distinguish between “seas” and “swell”. I don’t want to turn this into some sort of legal statutory interpretation argument, but if I had a nautical text like Bowditch in front of me I am sure I could give a clear definition of either.

Personally it is the seas that worry me. Even a huge swell can be managed. However, add some seas and things can become extremely threatening. Likewise, with hardly any real underlying swell 2 m seas can be sheer miserable. Then it gets even worse when the swells and seas are coming at you from different directions.
__________________
Life is a shipwreck but we must not forget to sing in the lifeboats. - Voltaire
SurferShane is offline   Reply With Quote
Old 18-01-2011, 04:46   #21
Mav
Registered User
 
Mav's Avatar

Join Date: Jan 2011
Location: Alice Springs & Port Stephens in Australia
Boat: Silverton, 360 Express, 38' Name pending
Posts: 75
Quote:
Originally Posted by capnorv View Post
I went across the Columbia bar in short fetch 25-30 footers once in a freak, think it was about 1970, won't do that again. The results of that one was a completely gutted cabin on a 20' Chriscraft, 7 boats lost, and a dream to join the CG when the 40' surfed by seeing if we were OK. But then that wasn't after 11 days out, so I guess it doesn't count
Now this is a co-incidence I was having a discussion about bar crossings with someone on another forum and they drew my attention to the Columbia River bar. OMG! this bar is downright frightening and no place I want to experience ever.

__________________
Mav is offline   Reply With Quote
Old 18-01-2011, 05:01   #22
Moderator
 
Pete7's Avatar

Cruisers Forum Supporter

Join Date: Aug 2009
Location: Solent, England
Boat: Moody 31
Posts: 8,524
Images: 14
Quote:
Originally Posted by SurferShane View Post
The “wave” thing is a bit confusing. Instead of using the word “wave” we really need to distinguish between “seas” and “swell”. I don’t want to turn this into some sort of legal statutory interpretation argument, but if I had a nautical text like Bowditch in front of me I am sure I could give a clear definition of either.

Personally it is the seas that worry me. Even a huge swell can be managed. However, add some seas and things can become extremely threatening. Likewise, with hardly any real underlying swell 2 m seas can be sheer miserable. Then it gets even worse when the swells and seas are coming at you from different directions.
Absolutely, add a tide into the equation and the shape and frequency of the seas on top of a swell can change in an hour both for the better or worse. We have a number of South Coast harbours were the prevailing SW wind doesn't have to build too much before some impressive "Hawaii-5-0" standing waves appear on an ebb tide.

We have retreated a couple of times to lick our wounds and wait for better conditions rather than beat ourselves into a pulp. Thankfully it normally only takes a day for conditions to change.

One thing I have noticed is the yacht is much more stable or comfortable if the speed is slowed from 6 to 4 knots. Although it seems to take an age to go anywhere, the motion can be much more tolerable for moving around on board.

Pete
__________________
Pete7 is offline   Reply With Quote
Old 18-01-2011, 05:09   #23
Moderator... short for Cat Wrangler
 
sarafina's Avatar

Cruisers Forum Supporter

Join Date: Jul 2009
Location: San Francisco
Boat: Cal 28 Flush Deck
Posts: 5,559
Images: 56
Red face

hopefully I am remembering correctly that 4 meter sis around 12 foot...

12 foot swells with a really really close interval about killed me. couldn't go back had to go forward but man what a miserable few hours. Being offshore and unable to find port would so suck...

these days I have my handy scope patch, works a treat in smaller stuff, never had a chance to try it with anything bigger though...

I've seen 25 to 30 foot but was on a 120' boat so that doesn't count. Was hard to walk though!
__________________
Sara

ain't what ya do, it's the way that ya do it...
sarafina is offline   Reply With Quote
Old 18-01-2011, 05:25   #24
Registered User

Join Date: Jan 2010
Location: Montevideo, Uruguay
Posts: 238
I don't get "period equals boat length (40') times 1.5". Period is time, length is distance.

In any case, there are other variables that are, IMHO, more relevant. Such as wind, boat weight and length, and (as poster #5 said) whether the boat goes against the waves or surfing.

Where I sail the waves are always short period (because < 20' depth). Even tough is a lot harder to go to weather, I only get sea sick sometimes stern to the waves. While following waves over 8 feet. I had once a crew getting into a panic attack. She kept looking over the stern and thinking the waves will flood us. Didn't get better until we were moored.
__________________
dpons is offline   Reply With Quote
Old 18-01-2011, 11:02   #25
Moderator Emeritus
 
hummingway's Avatar

Cruisers Forum Supporter

Join Date: Jan 2010
Location: Gabriola Island & Victoria, British Columbia
Boat: Cooper 416 Honeysuckle
Posts: 6,933
Images: 5
Quote:
Originally Posted by Mav View Post
Now this is a co-incidence I was having a discussion about bar crossings with someone on another forum and they drew my attention to the Columbia River bar. OMG! this bar is downright frightening and no place I want to experience ever.

What a tragic story.
__________________
“We are the universe contemplating itself” - Carl Sagan

hummingway is offline   Reply With Quote
Old 18-01-2011, 11:10   #26
Moderator Emeritus
 
hummingway's Avatar

Cruisers Forum Supporter

Join Date: Jan 2010
Location: Gabriola Island & Victoria, British Columbia
Boat: Cooper 416 Honeysuckle
Posts: 6,933
Images: 5
Quote:
Originally Posted by dpons View Post
I don't get "period equals boat length (40') times 1.5". Period is time, length is distance.
There is a relationship between the wavelength and the period of course. This webpage from NZ gives a great deal of information on waves for both deep water and shallow:
Oceanography: waves
__________________
“We are the universe contemplating itself” - Carl Sagan

hummingway is offline   Reply With Quote
Old 18-01-2011, 12:20   #27
CF Adviser
 
Pelagic's Avatar

Cruisers Forum Supporter

Join Date: Oct 2007
Boat: Van Helleman Schooner 65ft StarGazer
Posts: 6,880
Quote:
Originally Posted by dpons View Post
I don't get "period equals boat length (40') times 1.5". Period is time, length is distance.

In any case, there are other variables that are, IMHO, more relevant. Such as wind, boat weight and length, and (as poster #5 said) whether the boat goes against the waves or surfing.

Where I sail the waves are always short period (because < 20' depth). Even tough is a lot harder to go to weather, I only get sea sick sometimes stern to the waves. While following waves over 8 feet. I had once a crew getting into a panic attack. She kept looking over the stern and thinking the waves will flood us. Didn't get better until we were moored.
To clarify dpons

When I have been involved as owner’s representative in tank testing large yacht models “Critical” wave periods (or frequency) have been found to be in the .98 to 1.3 range of ship or boat lengths at any given speed.

Think of it simply as the boat coming down one wave and being hit by the next before having time to recover.

Simply put, it is a dynamic relationship between ship length, ship speed, wave period and wave height which translates into hydrodynamic tests of the design at a given displacement and centre of gravity

In tank testing we measure and observe speed reduction, g-forces and the amount of water the vessel is taking on when we vary the wave frequency angle and pattern

This paper goes into all the issues in some detail:

http://www.shipmotions.nl/DUT/Lectur...nics_Intro.pdf

Shane, in reality all we really care about is comfort and how much water we are taking over the bow, so it doesn’t matter whether it is swell or sea or a combination.

It is all about comfort level at your perceived significant wave observation… and when you would decide to turn around in my given scenario
__________________
Pelagic is online now   Reply With Quote
Old 18-01-2011, 12:23   #28
CF Adviser
 
Pelagic's Avatar

Cruisers Forum Supporter

Join Date: Oct 2007
Boat: Van Helleman Schooner 65ft StarGazer
Posts: 6,880
Quote:
Originally Posted by hummingway View Post
There is a relationship between the wavelength and the period of course. This webpage from NZ gives a great deal of information on waves for both deep water and shallow:
Oceanography: waves
Great web page... Thanks Hummingway
__________________
Pelagic is online now   Reply With Quote
Old 18-01-2011, 13:14   #29
CF Adviser
 
Bash's Avatar

Cruisers Forum Supporter

Join Date: Dec 2008
Location: sausalito
Boat: 14 meter sloop
Posts: 7,260
While I can easily conceive of a stationary low, I'm having a hard time visualizing a stationary system capable of generating five-meter seas. Wouldn't a low with that much energy be moving?

If we're talking about a cutoff low here, which would be isolated from the main flow of winds aloft, these systems will only remain stationary for about three days before they dissipate.

Granted, three days in five-meter seas would be a trial, but it would certainly be manageable in a large boat with storm sails. The trick here, it would seem to me, would be to slow the boat way down.
__________________
cruising is entirely about showing up--in boat shoes.
Bash is offline   Reply With Quote
Old 18-01-2011, 13:22   #30
Moderator
 
Dockhead's Avatar

Cruisers Forum Supporter

Join Date: Mar 2009
Location: Cowes (Winter), Baltic (Summer) (the boat!); somewhere in the air (me!)
Boat: Cutter-Rigged Moody 54
Posts: 19,737
Quote:
Originally Posted by Pelagic View Post
Gee guys and here I thought I was very specific:

Beating into it. (ie…to windward…)

Wave period short 1.5 x your length and your chosen speed

cchesley…Monsoonal Lows can be very disorganized wandering around a given area for over a week, so this is part of the problem where normally you could just anticipate and steer to avoid it or just slow down. This bugger is doggedly in front of you and wobbling all over the place. Showing a frustrating trend to stay just in front of you

As to wind strength… variable with lots of squalls, so you keep having your rest interrupted by manageable but uncomfortable changes that make for confused seas.

It is really the misery factor versus our stubbornness to keep on plodding thru when a viable alternative is to add another week to your passage by backtracking to more comfortable waters.

At what point, in your pleasure boat experience have you said…enough is enough… these (?) waves are just too high, I am turning around ! or….??
My answer: I would turn around a lot sooner than the last time I was in that situation. Life is too short to spend it all in a long uphill bash.
__________________

__________________
Dockhead 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
Kubota - Will Not Turn Over Scare_Rab Engines and Propulsion Systems 39 21-09-2010 08:40
Wave Height Get-a-Life Cruising News & Events 8 19-09-2010 22:36
Maxsea-10 Wave Height GRIB Captain Jaz Navigation 3 11-07-2009 05:34
How to turn off an alternator? jdoe71 Electrical: Batteries, Generators & Solar 7 24-07-2007 18:04
Unfortunate turn! rhonda General Sailing Forum 440 20-02-2007 06:04



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 01:25.


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.