Nordy knocked down to 69°

In addition to Simi's link, the one below gives an idea of what is involved.

For entering, when you get to the first waypoint you head pretty much west across the shallow sand areas until you reach the second waypoint, at which time you turn south-west. This section has plenty of water depth, but is known as 'the mad mile' because of SW or NE tidal current flows that have waves, often breaking, coming onto your port beam. This gives rather confused seas. There are waves breaking onshore on your starboard beam as well, just to keep you focussed on staying on course!

https://noticestomariners.com/2017/10/03/safely-cross-wide-bay-bar/

What caused Dirona to broach was the 30+kn SE winds building big waves before they even reached the first waypoint to turn in.

Thx for the info.... Thought it was on the other side of the world.....

Looks like a challenge!

twistedtree said:

For these duct arrangements, is there no heal angle where they can down flood, for example when the duct is horizontal? I'm having a hard time envisioning an arrangement where no flooding can happen.

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The ducts go from the side exit and run inboard. If you want to be extreme, run them all the way to the other side. They should slope outboard when on an even keel to drain. When you are knocked down, now the ducts on the underwater side have their engine room side up in the middle or on the other (top) side - presumably above the knocked down waterline until you are pretty much sunk.

While you are at it, you can have a circuitous path for fuel vents, which will keep most of the fuel in and water out, even in a 90 degree knockdown.

Insequent said:

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What caused Dirona to broach was the 30+kn SE winds building big waves before they even reached the first waypoint to turn in.

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As mentioned earlier I still can't imagine why you would even leave Moreton bay with conditions getting up if planning a WBB crossing.

Simi
From memory they left Moreton Island dark O-something to get to the bar at high water slack. Which is what I do also. Although there was a SE change forecast, I think they left in good conditions. Going back to their detailed blog would confirm this.

But its a long trip up the coast, and I think the winds strengthened earlier than forecast. It happens from time to time. Conditions deteriorated rapidly, although with a following sea you don't notice it all that much. And there are no easy bailouts - as they discovered (and noted), if you can't cross the bar then you back-track about 5 miles to Double Island Point and roll around all night.

Insequent said:

Simi
From memory they left Moreton Island dark O-something to get to the bar at high water slack. Which is what I do also. Although there was a SE change forecast, I think they left in good conditions. Going back to their detailed blog would confirm this.

But its a long trip up the coast, and I think the winds strengthened earlier than forecast. It happens from time to time. Conditions deteriorated rapidly, although with a following sea you don't notice it all that much. And there are no easy bailouts - as they discovered (and noted), if you can't cross the bar then you back-track about 5 miles to Double Island Point and roll around all night.

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Notes from then

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8/23/2014: Pacific Dawn
The winds were forecast to be 25 knots, worsening to 35+ knots over the next three days. We didn't feel like waiting for the system to pass, so we decided to get the trip up the Sunshine Coast to Fraser Island done in the current conditions. We left at 1:30am to ensure we arrived at the Wide Bay Bar in the afternoon with good light and on a flooding tide. In the picture, we are working out of the well-lit, but shallow, Moreton Bay past the 811-foot cruise ship Pacific Dawn.

8/23/2014: Conditions
We're making great time at 8 kts or more (click image to enlarge), but the weather system arrived earlier than forecast and we're already seeing steady winds over 30kts. The seas are on our stern quarter--not too large, but quite steep--with some rolling the boat as far over as 25 degrees. We were leaned over far enough that the full hydrualic reservoir for the stabilizers briefly signalled low as the fluid tilted away from the sensor.

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That last highlighted bit would have had me turning back for Mooloolabah at least.

I have done that bar crossing about 50 times over the years.
Once I did it on our sailing cat in about 25 knots under sail and got taught a big lesson.
Zero dramas apart from soiled underwear but never again will I go there unless conditions are near perfect.
I'll gladly wait weeks if needs be, but that's me.

OK, winds initially stronger than I had recalled. Although they had read as much as they could find, there is not all that much. Enough, for sure. But the most useful info is word-of-mouth from other boaties. Its not rocket science. Its a bar crossing, with higher than average risk in poor conditions.

I've only crossed WBB a handful of times. I'm very cautious. I like forecast to be 15kn or less as its often 20kn when you get there anyway. And daylight, and high water slack. Low water slack there may not be enough water depth on the bar per se. And at mid-tide, the mad mile is full of lumps and holes without any pattern. Perhaps not dangerous, but downright unpleasant. I only did that once. I always plan ahead for a good window, and I'll happily wait for one as well if need be.

Ski in NC said:

69deg roll data came from a gps direction finder (??? something GPS). I don't doubt it was a harrowing ride, but wonder how accurate that instrument is in a highly transient situation.

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I had the same question. Guess I need to go research how a GPS device calculates heel angles accurately unless it has some gyro sensor augmenting the data.



-Sven

Okay, here I go again. Check out the CE rating...... of the boat. Then consider the amount of additional weight you have added on the upper deck, fuel and fresh water loading.

Google: “mems accelerometer “. You likely have one at arms reach. [emoji16]

Trawler_traveler said:

I had the same question. Guess I need to go research how a GPS device calculates heel angles accurately unless it has some gyro sensor augmenting the data.



-Sven

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All modern heading sensors supply heel angle. If you've got a modern AP it's available on the network.

I do not have a tattle tail on my apparent wind meter nor my roll indicator.

Trawler_traveler said:

I had the same question. Guess I need to go research how a GPS device calculates heel angles accurately unless it has some gyro sensor augmenting the data.



-Sven

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Roll sensors are integral parts of many heading sensors. Even some wind sensors include them. It's a pretty commonly available measurement on a boat. The Hamilton's boat would have one in the sat compass, and another in a backup magnetic heading sensor which I'm pretty sure they have. I've got two on my boat that can be readily displayed on any N2K display. Then at least two more dedicated to particular systems, one in the stabilizer control box, and one in the sonar control box.

OldDan1943 said:

I do not have a tattle tail on my apparent wind meter nor my roll indicator.

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Their reading was displayed on Maretron's N2KView, and it has telltales, plus it graphs the data. They also log all their data to a data base, that only happens at some interval and may or may not have captured the peak roll.