Monday, November 5, 2012

Port Essington to Darwin

Port Essington to Darwin

Thursday - 01/11/2012

There was no rush to leave Seven Spirit Bay this morning as the plan was to sail out on the last hour of the ebb tide this would assist us out of the port and by the time we cleared the headland the flood tide flowing west would assist us on our way to Cape Don.

So we sailed out at 1030 hours and I am pleased to say we sailed we had the winds with us but I don't know how long. Our plan was to anchor near Cape Don in Alcaro Bay being a short run of around 30NMS which we should get there quite early in the afternoon.

In leaving Port Essington it is best to clear the headland by about 3.5NMS as there are some rough patches closer to the coast and some shoals. As we left the port there was another Sealink Barge heading our way and an Army barge heading towards Darwin that passed us. Soon after we changed course we lost most of the driving wind and eventually had to motor sail. As we passed Lingi Point you could feel the boat pick up speed with the tide flow into Dundas Strait, we changed course to enter Alcaro Bay soon after. We entered Alcaro Bay and dropped the anchor and was pleased with the day our calculations worked well with the tides working for us.

This anchorage is good holding and would be good in the trades, at the moment we have northerlies and the anchorage sets up a little roll but not uncomfortable.

It is early to bed we have to sail at 0300 hours in the morning to catch the flood tide. Leaving hear 4 hours before Darwin high tide should see us go right through with the different tidal flows through Dundas Strait, Clarence Strait, Howard Channel, Beagle Gulf and Port of Darwin to do this we need to average around 7 knots.

There is a cruising guide the NT Coast by John M Knight that has some good information and tide tables showing charts of the tidal flows. I have tried to simplify this on the charts attached. The key factor in sailing from Cape Don to Darwin is to leave the Cape Don area 4 hours before Darwin's high tide time, take the suggested route shown on the charts which saves around 4NMS  from the suggested track on charts and chart plotters. I have listed four waypoints on the charts for this short cut after those just follow the recommended rout through Howard Channel.
(Chart showing track we took to save time waypoints below. Arrows show the tidal flow through the times of 4 hours through to 1 hour before Darwin High Tide, plan to enter Dundas Strait 4 hours before Darwin's High Tide)
(Chart showing the track through Howards Channel and Beagle Gulf with the 4th waypoint, this shows the tidal flow at 4 to 6 hours after Darwin's High Tide you need to be close to waypoint D4 around 4 hours before Darwin high tide time)
(D1 - 11 23.783 S 13141.241 E)
(D2 - 11 32.482 S 13132.629 E)
(D3 - 11 49.951 S 13123.372 E)
(D4 - 12 04.503 S 13111.526 E)
( Follow the recommended track after waypoint D4)
(Chart showing tidal flows in Beagle Gulf at 4 to 6 hours after Darwin's High Tide time and Darwin harbour 6 to 2 hours Before Darwins High Tide times)
(Chart showing tidal flows in Dundas Strait for 6 & 5 hours before Darwin's High Tide time and 5 & 6 hours after Darwin's High Tide times)
I was surprised at the run we had and the distance covered, when leaving Cape Don area we had one engine going and the sails up, the seas were flat and the only wind was the apparent wind that we made the tidal flow was strong and we were travelling at 8.2 knots across the ground this slowed to 6 knots after around one hour. The concern is if we lost too much speed we would miss the tidal flow further south so the idea was to keep an eye on the time matched with the tide charts and where we needed to be.  We needed to be passing Cape Hotham at 4 hours after Darwin's high tide to pick up the tidal flow through Howard's Channel, to do this I had to start another engine to pick up a bit of time being that we had no wind. We passed Cape Hotham 30 minutes late but it did not matter as we entered Howard's Passage we picked up speed through some turbulent water reaching speeds of 12.4 knots across the ground at this point we shut one engine down and had some apparent wind in the sails, after getting through that channel we changed course for Darwin via Beagle Gulf and the tidal flow was still with us and we continued at a speed of around 6 knots, we then reached the Port of Darwin and headed for Fanny Bay and anchored near the sailing club. We had travelled 108 nautical miles in 12 hours and 10 minutes this gave us an average speed of 9 knots for the whole distance.

This whole passage probably would not worry power boats like it does yachts because they have the power to get through the water against the tidal flows where yachts top speeds are around the 7 to 8 knots. However, if we had a power boat I would make sure I had the tidal flow with me at Howards Channel. The best thing a yacht can do if you miss the tidal flow is go and anchor and wait for the right time.

After anchoring and getting the covers on we enjoyed a well deserved coldie. We made contact with Alison and Rob who we know through Bluewater Sailing FB website that live here in Darwin and they are going to assist us in the morning to go into the marina through the lock which will be interesting the only lock I have been in is the Panama Canal and that is a lot wider than this lock.


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