Tidal affect and logistics on Bay Downwind Runs

Hey guys,

Been experimenting in New Jersey with some different Bay Runs that we have on tap most of the winter. They are located right between Staten Island and NJ, i.e. “The Armpit of America”. This first photo gives an overview of the waterways, I’ve been mind-surfing this run but it would be a wing out and deflate downwinder, haven’t done it yet.

Sandy Hook Missile Monument → Popamora Point, Highlands: This is a really fun 3 mile run that I’ve been hitting on an outgoing tide, the tide really rips out from two rivers to the south. NW-N wind

https://www.instagram.com/p/Czz3xnVuGkU/

Keansburg → Sandy Hook: I have only done this run a few times, only on an incoming tide. WSW-WNW wind

https://www.instagram.com/p/CvxrOMcA6CU/

Both of these runs remind of Gorge type conditions, not quite in the Hatchery or Swell City but still incredibly fun and easy. I have been completing them mostly on the Progression 170 and 14.5 tail, or the GoFoil PNL 185. I weigh 215 pounds dry. Currently in a 4/3 booties and gloves :unamused:

Do any of you other bay downwind run enthusiasts have any knowledge on how much the incoming or outgoing tide affects the wind swell? I’m curious if there are any ways to figure out how much water is flowing in or out on a given tide. We have large ranges from +/- 4-6 feet on tidal changes.

Also how much does depth play a role in the bay runs? Are any of you guys riding in something similar to this? I’ve found the 15-25 foot depth to work well until I run into a shallow bar, waist to chest deep and the bumps disappear.

How much wind do you find is enough in a bay run? I haven’t been out in less than 18-low 20s…

Thanks in advance for any help! Hope you guys are all getting out and scoring!

Ed

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Depth: never considered it but I had a bay run where around 15ft for most of it and then the bumps died early, and it may have coincided with shallower bar. I would have thought the opposite but maybe you’re onto something.

Tide: I know the crew around Oban in Scotland time their runs to match tidal flow and it stacks the bumps very effectively. Same in the Solent where they get very strong flow of up to 4 knots. Granted the tides are 20++ feet range.

Around my area it is less pronounced, but you definitely notice when you hit a nice bit of tide as suddenly everything stacks up.

I would guess if there are sailors around you could find a tidal stream atlas like the one below, which shows flows at neaps and springs (16,32 = 1.6kn at neap, 3.2kn at springs)

Wind: I haven’t done many bay runs and only in 30kn.

Wetsuits: hooded winter suits, boots, no gloves yet. Feel you there.

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Awesome, thanks! I found this NOAA Current Predictions - Current Predictions


Looks like the end of the one run can range from 1.5 - 3 knots… good to know!

Not gonna lie, had to google neap and spring tides haha

It has a bunch of different locations with Ebb and Flood, shows peaks with slack… Didn’t know where to look before you commented… thank you!

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Nice looks good. Checking the map I guess the flow is amplified under that bridge because it is draining the estuary, and probably guess your tidal flow would be lower on your SH-Highlands run.

Also worth thinking about the flow as a river, which will have swirls and eddying currents etc.
I love this stuff, and think it will play out in downwind for sure. One of the most famous tidal races in the UK is portland, and it does some interesting things on the various tides:

Also will definitely be strongest in the deeper channels so checking out the bathymetry of the area (Navionics another good one, though it looks pretty uniform in the bay)

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In Tampa Bay near the mouth, the tide movement has a huge effect on the dw conditions. If tide is opposing the wind, it seems doable in less wind, like 12-15mph. If the tide isn’t moving or is going with the wind, it seems like we need 20mph wind to make it work. Here is the short run where tide makes a big difference.

The water depth I think makes a big difference too. In the Sarasota bay or Tampa Bay, the bumps are so much better in the deeper parts(towards the middle).

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I spent a day tow foiling with Spoiled by the Foil in San Diaago. The boat captain said that when the water was less than 10-12 feet the boat could NOT kick up a wake big enough to efficiently foil behind. The bottom was messing with the wave energy.

I figured they had plenty of experience, aka 1,000’s of hours behind a boat with all the high tech gear, depth gauges, wash plates . . .

So we need 10-12 feet or more. This is consistent with what I have experienced on our downwind run Coyote Pt to 3rd Avenue in San Francisco. At the end of the run the bumps disappear. When you get off it’s only 5 feet deep. NO GOOD!

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For sure water depth makes a difference. In the ocean there is a clear difference between less than 50, 50-100, 100-400ft and 400+ feet depth in the size, speed, and arrangement of bumps.
In the gorge, the best line isn’t the most direct or the most exposed to wind, it’s a line that follows a deep channel on the bottom of the river.

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@KDW would be stoked to hear more about the depth as you have the range and conditions to compare. I once read that all the best downwind runs have about 10-20m (30-60ft) of depth, and it seems to be somewhat true on the charts for Maui, Perth and Millers Run

I wonder if true and I wonder why? Is it maybe that wind bumps work best when they don’t interact with the sea floor?

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If this only happens in rivers and tidal flows, it might have to do with the current being slower in the shallows.

The general depth consideration isn’t restricted to tidal, but you are right that faster current makes the bumps stand up more, what is interesting is that at Hood river despite the faster opposing flow, the increase in bumps makes up for it with resulting higher speed over ground.

M2O 2024 might end up looking like a bit of a tech arms race :smiley:

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Some interesting conclusions here.
Shallow water areas, will alway slow down bumps, when touching the wave will raise and loose every; this may be the reason for concluding that shallow areas are worst.
A wave interacting with an opposed current will have a similar effect, and increase its slope.
For those serious about this it may be worth to read some scientific literature.

Regarding what causes the wind over tide effect, it seems to be pretty poorly explained in general, this is a nice visual theory - basically the flow causes waves to converge. Generally all quite interesting - see a discussion here where some theories are thrown around.

What remains unclear is why you can’t hydrofoil bumps in less than 10ft depth?

There was loads of interesting info in the Matt Costa interview for anyone who is interested in a deeper dive into the general phenomenon of what causes waves

Current in opposition of waves effect, was explained to me based in conservation of energy. The wave slows down in speed when the current is found and the energy transforms in height.

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Yeah that seemed to be an acceptable idea. What is cool is that the foil then transforms that height back into speed, which is an increase over the loss of speed due to the current

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