Mark
I'm sitting here on an early Monday morning. Not only are we confined in the house because of the virus rules, but it's raining something awful and blowing 30 kts or so. So I thought you would be interested in some thoughts and history of New York City's infamous Hells Gate. First of all it is Hells Gate, not Hell Gate. The name was translated from the Dutch words that basically meant "The place that's so awful that you never want to go there". That isn't a literal word for word translation.
Hells Gate is the narrow section of the East River where it branches off to combine with Long Island Sound and where the Harlem River joins in. The tidal ranges between the Sound and the lower bay are in the neighborhood of 7'. So as the diurnal tides change daily the displacement of water from one to the other is pretty large. Those changes create currents that probably average about 5kts. Those currents are then channelled into a twisty narrow area between Randalls Island (Bronx) and Astoria, (Queens).
In addition to the fast moving currents moving horizontal, in the middle of all this fast moving water there are wellups. Because the bottom contours below the surface are at places radically different, the bottom can go from 160' to 60' abruptly, there are currents created that are called wellups. This is where the horizontally moving water is diverted into a vertically moving current that reaches the surface. As you cruise through the Gate there will be multiple round shaped eddys on the surface. The problem with these eddys is that the vertical moving water prevents the hydrodynamic effects on the rudder of a slow moving (relative to the water) sailboat. Thankfully the size of the eddys is not so great so that the boat will pass out of the eddy before you realize that your rudder isn't working.
Another hazard at Hells Gate is the commercial traffic. This is a major waterway between the City, the Sound and points East. All sorts of ships, tugs and barges are using the Gate all the time. Because it is narrow and there is a big bend in the middle of the channel, you can't always see what is coming and how big it is. Radar and AIS help a lot but not always. You can have calculated the perfect time to transit the Gate with the current helping you through when a full size ship appears coming the other way demanding right of way.
A bit of interesting history about Hells Gate. Over the centuries there have been hundreds of shipwrecks associated with the Gate. Today the depths through the area are deep enough for clear navigation. That wasn't always the case. On the West end of the Gate near Manhattan there was a section of shallow water clustered with large rocks. For many years that area was a severe hazard to shipping. Something needed to be done. In the early 1800's a French engineer took a contract for $12,000 to blow away one particularly large rock. His idea was to drop weighted sticks of dynamite on the rock at slack tide and destroy it. After he used up $12,000 worth of explosives, the rock was still there and he quit. By the 1850's something a bit more organized was deemed necessary. Vertical shafts were dug down from what is now Shearer Park, the location of Gracie Mansion, the home of the NYC Mayor, in Manhattan. The shafts went through the rock to below the river bed. From there they tunneled a spider web of tunnels under the shallow areas of the river. When the network of tunnels were finished and all the debris removed, they packed the tunnels with explosives. Something like 300,000 lbs of explosives. When they blew the explosives, it was recorded as the largest man made blast until the first testing of the Atomic bombs. The river bottom with all its dangerous rocks subsided down into the space of the tunnels and the Gate became much clearer to navigation.
Bonnie and I have navigated Hells Gate many, many time over the years. If heading down (Westbound) the river we plan to arrive at the Throggs Neck Bridge about 45 minutes to 1 hour before the slack before ebb occurs at the Gate. That gives us a fair current thru the Gate, past Manhattan and out to the Varranzano Bridge. To Come back up (Eastbound) we make the Varranzano Bridge 2 hours before the slack before flood current. That takes us all the way back into Long Island sound with current in our favor. This is all based on motoring at 6kts. Sailing through the Gate and up or down the river is not an option although we always have the main up and the jib ready just in case.
One last interesting tidbit. If you you ever pass under or see a photo of the Hells Gate railroad bridge, which crosses the narrowest part of the Gate, you'll probably notice a striking resemblance to the famous Sydney Harbor Bridge in Australia. Both were designed and built by the same designer. The One in NY was built first.
I hope this will be of interest to some. I figure it got me through an hour or so of a rainy morning where we can't go out. Enjoy.
Jim
