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post #78 of Old 01-26-2013
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Re: 2013 5th Annual Sailnet Chesapeake Rondevous- June 8, 2013

Originally Posted by Ulladh View Post
Depart Essington Friday June 7th, 12:00 noon at slack before ebb
Enter C&D after 5:30 PM slack before flood
Slack before ebb at Chesapeake City is 10:45 PM but we should be there before 8:30 sunset.

Depart Chesapeake City 4:30 AM slack before flood, in twilight before 5:30 sunrise.
I will get to MYC in early afternoon, you are faster and should be there by noon.
Colin - I should probably PM this you, but since we've gotten praise for sharing our planning process in the open, I'll post it here.

We should compare notes on how we predict currents, because I'm coming up with very different current predictions down near the canal. For the canal I like to use NOAA's current tables instead of trying to infer something from tide levels, because that can get you into trouble in the canal where currents are complicated by the differing water levels in Ches & Del sending "humps" or broad waves of water through the canal.

So for reference, the examples I'll mention here are covered in:

2013 Current predictions near Reedy Point
2013 Current predictions at C&D Canal Entrance
2013 Current predictions at Chesapeake City Bridge

For instance, on June 7 peak ebb near Reedy Point is 1656, followed shortly by low tide at DelCity (1749). Slack before flood at Reedy is 1925. But a mile away at the canal entrance, peak ebb is happening at 1921. So slack at Reedy is the worst time to enter the canal. This makes sense when you realize that low tide on the Delaware end of the canal is causing water to drain out of the canal. It takes several hours into the flood for the Delaware to rise enough to start pushing water back into the canal, and then you can ride the wave through. Unfortunately, slack before flood at the canal entrance is not until 2155.

You mentioned slack before ebb at Chesapeake City at 2030, but my table shows 2140, and remember that ebb at that point is defined as flowing toward the west, so arriving before 2140 means we would be fighting against the current the whole way. Arriving after 2140 means we have the current helping us out.

So that's why I suggested a ~2 hour stopover in Delaware City (hopefully on the city dock if there's enough water there) for dinner or maybe a nap (for the late night transit), and a nightime transit through the canal with the currents. If we do this, we would have to fight the Delaware River flood for 1.5 nm from DelCity down to the canal, unless we instead anchor south of the canal to wait it out.

Obviously the transit would not be in pitch darkness thanks to the sodium floodlights along the canal, but since it's almost new moon that night we'd be pulling into Engineer's Cove in pitch darkness. I'm open to your suggestions about how you feel about that.

Not sure how much danger we'd be in from the go-fast boats on a Friday night, or from large freighters (that I'd have lots of warning for on AIS). What's the experience with that from everyone here?

Another possibility might be to leave Thursday, which makes all the tides and currents about an hour earlier and gives us some slack time in case we're weathered in on the way down. If we arrive Friday in Baltimore, I'd be interested in daysailing around the area on Saturday.

FYI, I have a spreadsheet that calculates the net effect of the current along the whole route (maybe I sent it to you?). It was built around the currents for August 25, 2011, when we had planned to transit the canal but were washed out by Irene. At some point I'll generalize the calculations to work any day of the year. FWIW, absolute shortest time on the water is actually achieved by waiting 6 hours in Delaware City, but obviously that delays arrival significantly. In general, a 3 hour wait in Delaware City results in a 2 hour delay in arriving at Chesapeake City. You recover an hour of the wait time with the push you get from the current.

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Last edited by TakeFive; 01-27-2013 at 12:24 AM.
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