Wave height vs period

Steve said:

I call that "washing machine chop"
Remember, the only thing worse than being at the dock wishing to be out on the water is to be out on the water wishing to be back at the dock!

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Yep, Gulf Coast Chop. Seen that too many times. My dad used to say that three feet in the Gulf was as bad as six feet in the Atlantic. After being out on both quite a bit now, I think he was right.

I do most of my boating on the Chesapeake where 2 to 3 second periods are typical. I avoid anything over 3 feet in a head sea, and a quartering or following sea at up to 4 feet is tolerable for a while. Been through 5-6 foot standing waves at Smith Point (mouth of the Potomac) a couple times and it's a mess. As I get older, and now retired, I'll don't purposely go out in anything over 3 feet. I'm in a 37 foot planing hull boat and normally run 22 knots.

sawdustdad said:

I do most of my boating on the Chesapeake where 2 to 3 second periods are typical. I avoid anything over 3 feet in a head sea, and a quartering or following sea at up to 4 feet is tolerable for a while. Been through 5-6 foot standing waves at Smith Point (mouth of the Potomac) a couple times and it's a mess. As I get older, and now retired, I'll don't purposely go out in anything over 3 feet. I'm in a 37 foot planing hull boat and normally run 22 knots.

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Chesapeake boater here too. Usual frequency is 2 seconds measured at the buoy outside of the Patapsco. SD hull can take it, but you have to decide how miserable you want to be at 8 knots. My wife and I are fine, but non-boaters don’t enjoy it when the wave action increases.

Islanddreamer said:

Chesapeake boater here too. Usual frequency is 2 seconds measured at the buoy outside of the Patapsco. SD hull can take it, but you have to decide how miserable you want to be at 8 knots. My wife and I are fine, but non-boaters don’t enjoy it when the wave action increases.

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That's one thing many don't realize how those conditions, especially in the Chesapeake, are so much easier and more comfortable with more speed. At higher speed you can often just skim across the tops. (I'm not talking 8 knots when I talk higher speed).

At higher speed you can often just skim across the tops.

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Well, not exactly that unless some sort of hovercraft. More like pitching and yawing get replaced by pounding. As for roll, generally speaking speed counters a lot of it in chop... one reason why the faster the boat, the smaller the stabilizer fins you need.

Ah yes, the Chesapeake. On an otherwise beautiful day all you see out there is these guys, and big, heavy stabilized pleasure boat(s).

Skimming across the tops of waves.... I caught my Albin saying this in her sleep one night.

BandB said:

That's one thing many don't realize how those conditions, especially in the Chesapeake, are so much easier and more comfortable with more speed. At higher speed you can often just skim across the tops. (I'm not talking 8 knots when I talk higher speed).

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caltexflanc said:

Well, not exactly that unless some sort of hovercraft. More like pitching and yawing get replaced by pounding. As for roll, generally speaking speed counters a lot of it in chop... one reason why the faster the boat, the smaller the stabilizer fins you need.

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Caltex, the point that you're missing is size and weight relative to speed. A 60 to 90' boat designed to plane in the 25 plus knot range, cruises without pounding in short period seas as it often is on 2 to 3 waves at the same. Take a ride on a 60' sport fish running 25 knots in 4' seas. You will be amazed how smooth a ride it is as the boat is cutting though the upper part of the waves as opposed to bouncing up and pounding down on them.

Ted

O C Diver said:

Caltex, the point that you're missing is size and weight relative to speed. A 60 to 90' boat designed to plane in the 25 plus knot range, cruises without pounding in short period seas as it often is on 2 to 3 waves at the same. Take a ride on a 60' sport fish running 25 knots in 4' seas. You will be amazed how smooth a ride it is as the boat is cutting though the upper part of the waves as opposed to bouncing up and pounding down on them.

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Yep, my EB47 handles choppier conditions much more smoothly than our 34' express cruiser it has replaced. It's a combination of added waterline length, greater weight and hull construction. It's bridging move waves at once, with more inertial mass. This combines to do more to part the waves and resist their motion. The heavier, thicker hull keeps it from feeling as rough.

Now, I'm not going to hemorrhage money burning fuel trying to reach it's max of 30 kts in those conditions but I can push 16-20 through it quite well. Throttle back to 8 kts and it's semi-planing hull becomes a liability since it lacks the deeper keel of many trawler types. There's potential for a lot more roll. Less than a smaller boat but still more than a motor yacht/trawler of equivalent size.

Here's our current local forecast for the next week. I expect there won't be very many boats out in it.

Wave height between 4 - 12 feet. The wave period is between 8 - 20 seconds, but there would be a lot of wind chop mixing things up as well so we won't be getting any smooth rollers.

I don't expect it to be very pleasant out there.

https://www.seabreeze.com.au/weather/wind-forecast/adelaide

Take a ride on a 60' sport fish running 25 knots in 4' seas. You will be amazed how smooth a ride it is as the boat is cutting though the upper part of the waves as opposed to bouncing up and pounding down on them.

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I've done exactly that, actually. A few times. And also at 14 knots on my 56 Hatteras too. Of course it is smoother than slow trawler, or a smaller, lighter boat but a) it is not "skipping over the waves" and b) it still pounds as it hits steep head seas and blasts through them. Following seas, a different matter.

This is fairly typical for Summer in our area. A big South can bring much larger swells, but they are long period.

Damn. 5’ waves at 14 seconds. Perfect for my old ass to surf on. Except for the cold water. ?

We arrived at the dock on the Washington coast in April 2014 and saw the forecasts and felt like there was no way we'd actually be able to get out and enjoy as anxious as we were do do so. We saw 10' waves and were shocked when told it wasn't bad. We'd never been exposed to the west coast swells and it was all swell at 13 to 14 seconds so out we went the following morning and that was our indoctrination. There was virtually no wind wave.