Wave Height . . . When Would You Turn Around ?

[atoll]

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.

[Pelagic]

Originally Posted by Laidback

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?

[capnorv]

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

[hummingway]

Originally Posted by capnorv

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.

[SurferShane]

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.

[Mav]

Originally Posted by capnorv

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.

http://www.youtube.com/watch?v=1Bfo3vqFvK0

[Pete7]

Originally Posted by SurferShane

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

[sarafina]

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!

[dpons]

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.

[hummingway]

Originally Posted by Mav

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.

[hummingway]

Originally Posted by dpons

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

[Pelagic]

Originally Posted by dpons

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]

Originally Posted by hummingway

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

[Bash]

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.

[Dockhead]

Originally Posted by Pelagic

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.