Tides and Tidal Currents
A portion of last night’s Seamanship class dealt with the effect of tides (the vertical movement of water caused by the effect of the moon and the sun on the earth) on water levels in certain cruising areas. Although tide is not a factor here it will be once we get to the east coast or further south. There are a variety of ways of estimating the height of the water once you know the high and low water levels from your tide tables. The way that we learned in our Fast Track to Cruising course was surprisingly not mentioned in the Seamaship class. What we were familiar with is called the Rule of Twelfths, described on this page.
We also discussed tidal currents which is the horizontal movement of water caused by the tide change. On the practice chart we were using, which shows areas around Vancouver Island, the currents are sometimes 7 knots or higher. We definitely don’t want to try to navigate through those channels when the current is at its peak!
During a break in studying for my HAM radio license yesterday I contacted Pride Marine, our local chandlery, to order some braided polyester line for our new Seabrake drogue. When I told them that I wanted close to 200′ of 9/16″ line I think he thought that I was a little crazy as that is fairly big line. Who am I to second guess the manufacturer though as that is what their specs call for. I was adding up all the line (rope) that we will be carrying on board Katana and there is a LOT! A lot meaning a lot of space required to store it and a lot of weight. I guess it’s all necessary though.
When I spoke with Clive at Pride I told them that I would be needing some eye spices on the line. Rather than just paying them to do it for me I asked if they would teach me how to do it. Although I know they are busy, and will only be getting busier as the season progresses, they agreed. Splicing polyester braided line is significantly different than splicing three-strand rope. While I can do the latter, thanks in part to my friend Peter’s instruction, I think with a bit of help from the guys at Pride I will be able to figure out the other technique too. There are some downloadable instructions here on this page but nothing beats hands-on instruction from a good teacher.
Tides are always interesting,especially in Maine,where they get in the 9-12ft range Midcoast,and higher Down East.
I anchored off McGlathery Is. near Stonington ME,one afternoon,tucked in out of the wind. We set an anchor at high tide,and set a stern anchor to hold us off a ledge when the wind shifted. Next morning,at low tide,our anchor is set on the beach,higher than the deck of the boat.I dinghied over to pull the anchor,and retrieve it.
When you anchor in close quarters,with tides,you have to allow for the boat to swing with the tide change,and adjust the rode to allow for the extra lenghth,as the tide ebbs or floods.
A great tool to have is http://www.landfallnavigation.com/-bp002.html
the Eldridges Tide and pilot book.
Great… more stuff to learn! 🙂
Thanks for the tip on the book, and Landfall Navigation. I think I have ordered from them in the past.
That’s always a danger with a catamaran; we’re so used to sneaking onto shallow water that we forget the tide completely. I’ve done it twice, I admit.
Patience is the cure. The water comes back!
But do be careful if there are any waves at all. You can find yourself packing up in a hurry (only did that once)!
Scary stuff for us newbies!
Depends on how you look at it. Learn from it.
The first time I anchored too shallow, Jessica and I were anchored behind Cedar Island, VA on our second trip around the Delmarva. About 3 in the morning I heard the scraping and decided we had to move; we were in a Stiletto with very thin hulls and were rubbing on shells. It was pitch black, no moon, the deck light had died, and the nearest street light was about 10 miles west. There was a strong tide running, about 3 knots.
I started sorting out anchor lines for some reason – I think it was because the bottom was terrible holding and I wanted a second hook down, but had tangled the ropes int he dark – and somehow I disconnected the anchor from the rode… and threw the anchor over with no rope. Clearly, I thought it was connected, but it was the OTHER anchor I had just finished attaching. Given the current, that we were in 20 feet of water, and the disorientation of darkness, there was no hope of recovering it. We had another anchor and made do.
The “fun” part is that my daughter came home and wrote it up for Latitudes and Attitudes Magazine and got the story published! So much for “what happens on the boat stays on the boat.”
I’m collecting blackmail material for her first date….
lol. Great story. 🙂
I just ordered ,and rec’d my Exuma and Near Bahamas charts and guides from Landfall Navigation,and they did a great job,at a fair price.
Explorer Charts? We purchased all three of the Bahamas ones.
As for splicing, just don’t try old double braid; it’s miserable. Practice with new scraps….
Which is why I prefer knots, mostly. I can’t fix a splice, I can only replace it with a knot.
Splicing 3-strand is relaxing. You feel like an old salt and it’s hard to screw up, really. Except fitting thimbles. Generally, if I really need one (anchor line perhaps) I just thread a piece of tubular webbing on the rope and the required spot. Lasts as long as the rope.
Cheers!
I also find splicing 3 strand, and tying knots, relaxing. I drive Rebecca crazy because I sit here with a piece of cord in my hand, tying knots constantly, while watching movies. Once she gives me the evil eye I typically put the cord down!
I am interested to see how hard splicing the braided line is. It is obviously a totally different process (at least that is what I gather from the images I have seen).