Wave Height

Wallkerbay · Posted: Sat May 30, 2009 8:19 pm Post subject: Wave Height

How do you tell the wave height. My wife and I took our C-Dory out today.We had to turn around. It was way to rough for us. We crested one wave and as we came down ,all we saw was water.The boat took it fine. We keep our Dory at VININGS Marine Center in Norfolk Virginia. Thumbs Down

JamesTXSD · Posted: Sat May 30, 2009 8:45 pm Post subject:

Hi Neal and welcome aboard,

Wave height is only part of the story... wave period is very important in how comfortable the ride is. If the waves are closely spaced, 3 foot waves can be uncomfortable. If the waves have a longer period, larger waves can be easy.

Seems that most people tend to over-estimate wave height when asked (kinda the way some fishermen... um, nevermind). Besides getting a current NOAA report, I use fixed points on the boat - you know how much freeboard you have, how tall the cabin is, and how far off the water the top of your antenna is? Shocked

We found that our ability to deal with waves increased with more experience on the boat... finding the right throttle use, trim tabs, boat speed, etc.

There are times that you shouldn't go out... it's up to you to determine what combination of waves, wind, period, etc meets your comfort level.

Best wishes,
Jim B

Levity · Posted: Sun May 31, 2009 8:53 am Post subject:

From your location at Vinings you may find the following website useful: http://www.ndbc.noaa.gov/maps/Chesapeake_Bay.shtml . Click on Scripps weather buoy #44099 (yellow dot) for current conditions or use it for historical information.
Mike "Levity"

Pat Anderson · Posted: Sun May 31, 2009 9:14 am Post subject:

Nothing wrong with turning around and coming in. We also turned around and came back to the dock in 2003. It was the first time we got out into some good size waves when we had our CD22. Today I would not fear those same waves in a 22, but this only comes with a bit of experience. You comfort level (and more importantly, spousal unit's comfort level) will increase with more time and experience. Jim's observations are right on. Some times we have been caught out, and learned that even though we are getting our fillings knocked loose in big water (trip from Sequim back to Everett a few years ago comes to mind!), we were actually quite safe. Enjoy the boat!

matt_unique · Posted: Sun May 31, 2009 9:41 am Post subject: Waves

Good advice above.
Sometimes a reference to eye level can be useful as well as reference to other vessels.

For example, a few weeks ago I was exiting the mouth of the Merrimack River in Newburyport MA. Ahead of me were a 30 something foot trawler and a 21' cuddy cabin. The cuddy cabin and both passengers completely disappeared in the troughs (bottom) and would only reappear when coming up the crests (top) of the waves. The entire structure of the Trawler disappeared in the troughs except the very top control station.

When it was my turn to take on the current induced waves hitting the ocean the waves were a little taller then me (I'm 6'). I thus estimated the waves to be 7'. I took more water over the bow of the Tomcat than I ever have before. The period of the waves was very short and the shape was steep.

I heard that an 18' vessel capsized in this spot yesterday ejecting the single occupant. Another vessel supposedly picked up the person and managed to get a line around his vessel.

I have cruised in 10' swells with a long period and no wind. These were fueled by an offshore storm. It was no big deal, like riding up and down a freight elevator. I have also been in 6' cresting seas in measured Gale Force winds. The vessel would literally "fall" off the crest of the waves. That was scary and I got the hell out of there.

It is an example of great seamanship to take action and decide to wait for better seas. Weather rules all machines.

damason · Posted: Sun May 31, 2009 9:47 am Post subject:

Here in the Gulf of Mexico the waves are most of the time manageable. We are in the Northern Gulf near Destin. 1 to 2 feet is fine and 3 to 5 is on the edge of not going out. When the weather report says 3 to 5 feet I have found that means the waves are going down 3 feet from level and going up 5 feet from level - so the end result is 8 foot waves. This may not be really true but it seems like this is the case. When starting out of the Destin pass if we notice waves breaking over the rock jetties we turn around and go back and fish the Choctawhatchee Bay. The waves outside are going to be "PUKE CITY". Crying or Very sad

DaveS · Posted: Sun May 31, 2009 10:33 am Post subject:

thataway · Posted: Sun May 31, 2009 5:28 pm Post subject:

Wave height is measured from bottom of the trough to the top of the peak. As Jim noted, just as important is the peroid or timing of the waves

For a 22 three feet steep waves are a lot, and you will be pounding in 2 foot seas. The 25 will take slightly more. This doesn't mean that you cannot go out in 4 to 5 foot seas, but if the peroid is steep, time between crests is short, then the occupants will suffer . Long peroid waves make little difference to a C Dory. The largest seas we have been in were documeted at 45 feet and breaking, but this was in a 62 foot boat and in mid Atlantic--still something you could not go into, just away from. Same in a C Dory, you can run in beam or following seas which are much greater than what you can buck into.

C-Green · Posted: Sun May 31, 2009 8:35 pm Post subject:

Weather bouys are great for real time data but you need to know NOAA"s methodology. The wave height given (at least for Lake Superior) is the height of which 80 % of the waves are of equal or lesser height. I assume the forecasts of wave height x to y feet may use the same criteria. Well, when I'm out I don't pay attention to those waves; I'm concentrating on and noting the top 20%. So that's why 3 to 5 foot seas seem like 5 to 7 foot seas, because they are. That's my read.

Jay

Jack in Alaska · Posted: Mon Jun 01, 2009 2:06 am Post subject:

When my 1st mate crushes the teak grab handles while hanging on and yells..."why did you bring us out in this?" I then think it is time to start turning around.... Laughing

Doryman · Posted: Mon Jun 01, 2009 8:45 am Post subject:

smittypaddler · Posted: Mon Jun 01, 2009 12:26 pm Post subject: Front vs back of waves?

The NOAA surf reports say, "Surf heights are forecast heights of the face or front of waves." Also, it used to be common knowledge that Hawaiians reported wave heights less than the rest of the world, because they reported the back side. The idea of the front of a wave being of a different size than the back is puzzling. It seems to me what goes up x units must come down x units. Can anyone explain?

Tortuga · Posted: Mon Jun 01, 2009 1:42 pm Post subject:

We have a deal on Tortuga... if anyone barfs, the person driving has to buy the barfee a prize. But to get the prize, you really need to produce something. Don't ask about the inspection process...

Smuttynose · Posted: Mon Jun 01, 2009 2:26 pm Post subject:

Interesting topic regarding wave heights and the implied seamanship skills important in handling a C-Dory. I have a 22 and have taken on some heavy seas, and have a simple, and possibly really stupid question, has one ever 'rolled over' in a breaking crest of a wave?

David
Smuttynose Island, ME

C-Green · Posted: Mon Jun 01, 2009 11:14 pm Post subject:

I stand corrected. Direct from the NOAA bouy site "WVHT - Significant wave height (meters) is calculated as the average of the highest one-third of all of the wave heights during the 20-minute sampling period." So, the average of the top 1/3 would be the 83rd percentile; not much different than the 80th percentile so my logic still stands.

Jay