Secondary ports .. what do you use to calculate?

[Nostrodamus]

Secondary ports have always been a pain when It comes to working out the exact times and heights you need, well that was until I discovered “total tide”.

Life has now got so much easier and the sailing so much more relaxed and enjoyable.

If I need to do it the old way I use a mathematical way rather than the graphs as it is quicker and more accurate.

What do you do?

Suck it and see, have an educated guess, work it out or use a computer program.

 

[Deleted member 36384]

Most of the time I just use the graph. I once had a bet on when we would float at a secondary port (Loch Aline Pier). The test was to push against the wall at your chosen time and move the boat sideways. Everyone rocked the boat at their calculated time. I counted down to the time calculated from the graph, shoved against the wall and she floated free; luck I say.

One should always remember that it is only an estimate anyway, whatever way it is calculated.

Is total tide the "Admiralty TotalTide" available from the Hydrographic office? http://www.ukho.gov.uk/PRODUCTSANDSERVICES/DIGITALPUBLICATIONS/Pages/ATT.aspx

 

[Nostrodamus]

One should always remember that it is only an estimate anyway, whatever way it is calculated.

Is total tide the "Admiralty TotalTide" available from the Hydrographic office? http://www.ukho.gov.uk/PRODUCTSANDSERVICES/DIGITALPUBLICATIONS/Pages/ATT.aspx

I agree about the estimate as there are other factors as well.
Yes, it is the "Admiralty total tide".. really excellent. Found it invaluable around Britany and Normandy for sills and getting in. Before leaving I woul estimate an arrival time and write down height of tides a couple of hours either side. It was usually pretty acurate and allowed us to know the best time for an entrance. Never let us down.

 

[dt4134]

Very rarely find any difficulty with them. I use a mathematical method as doing it the RYA way with graphs is pretty slow.

I also knocked up a reasonably useful spreadsheet but don't actually use it that often in practice.

As well as being only a prediction you also have to realise that the relationship between primary and secondary port is not going to be a triangular waveform. Still, for want of anything better...

 

[Nostrodamus]

To me a triangular waveform is something in the percussion section of a band!

 

[NUTMEG]

Navionics...

...and an iPhone.

 

[Blue5]

Secondary ports have always been a pain when It comes to working out the exact times and heights you need, well that was until I discovered “total tide”.

Life has now got so much easier and the sailing so much more relaxed and enjoyable.

If I need to do it the old way I use a mathematical way rather than the graphs as it is quicker and more accurate.

What do you do?

Suck it and see, have an educated guess, work it out or use a computer program.

Usually an educated guess using mental arithmetic unless it is going to be critical at which time the graph paper and pencil come out.

Have to agree Total Tide is very useful.

It amazes me the differences in tide times between almanacs and local tide tables.

 

[Phoenix of Hamble]

Usually an educated guess using mental arithmetic unless it is going to be critical at which time the graph paper and pencil come out.

Have to agree Total Tide is very useful.

It amazes me the differences in tide times between almanacs and local tide tables.

Pretty much what i do too... I can usually get within a few centimetres, and IMHO, thats close enough.

 

[DAKA]

I use Belfield tide plotter on my laptop £11 for a year but not only has secondary tides but also includes tide flow diamonds , its so easy to look at a basic chart and change each hour of a planned passage to see where/when the tide flow swings with arrows (size shows large/small flow) click on an arrow for accurate data speed and direction, also includes a basic distance plotter tool.

http://www.chartsandtides.co.uk/tideplotter

 

[Twister_Ken]

iPhone + Marine Tides Planner app from Tucabo

I can do it the RYA way, but why bother?

 

[capnsensible]

mins/hour change, can do in yer head.

Dont have an i phone.

 

[jimi]

mental arithmetic, its close enough for me considering the effect atmospheric pressure and wind strength & direction can have.

 

[prv]

iPhone + Marine Tides Planner app from Tucabo

Me too as of two weeks ago. Used to use a different (cheaper) iPhone app, but that would only do predictions a week ahead (UKHO license requirement). Tides Planner will do a couple of years in advance.

Before such technology, I didn't used to bother doing the secondary ports business. Never used to cut things fine enough to need such precision. Maybe a quick glance to see if it's "a bit earlier" or "a bit lower".

I'm aware this means I'm out of practice - although I understand the principle it might take me a while to figure out the detail. So I have a worksheet on board with boxes to write numbers in, step by step instructions, and a worked example. To guide a possibly tired brain if the electrickery has packed up.

Pete

 

[Elessar]

Secondary ports have always been a pain when It comes to working out the exact times and heights you need, well that was until I discovered “total tide”.

Life has now got so much easier and the sailing so much more relaxed and enjoyable.

If I need to do it the old way I use a mathematical way rather than the graphs as it is quicker and more accurate.

What do you do?

Suck it and see, have an educated guess, work it out or use a computer program.

I use the chartplotter if on the boat. Surprised no one else said that. Nice graphs and everything.
Or day tides on the iPhone.

Or the traditional way if looking ahead and I'm not on the boat, I'm too mean to pay for look ahead programs.

I don't have difficulty calculating it from the almanac data, I don't see what the fuss is about that. But it is, of course, slower than just looking it up on the plotter (if you don't have to drive to the boat to do so!)

 

[webcraft]

mental arithmetic, its close enough for me considering the effect atmospheric pressure and wind strength & direction can have.

Ditto. Roughly, a change in pressure of one millibar will change the tide height by one cm. Tide tables assume a standard pressure of 1013 millibars. This means that a pressure of 1040 mb, pretty high but not abnormally so, could give a sea level lower by nearly 30 cms than expected, while the difference between 1030mb and 970mb is about two feet.

Here in Balvicar Bay it is not unusual to get a three hour stand with up to an extra metre of tide in a SW gale with low pressure.

I teach secondary ports as it is part of the RYA syllabus and it is good to know how to do it, but unless you are a busy person with a sill you need to get over regularly I suggest to candidates working things out painstakingly to the nearest cm is likely to eventually result in some kind of disappointment.

- W

 

[Poignard]

What do you do?

Mental arithmetic, ie guesstimate.

 

[Conachair]

What do you do?

Suck it and see, have an educated guess, work it out or use a computer program.

I use secondary port calcs for weather forecasting. If you have to calculate such things then you are obviously far too far north and it's probably raining. Or just about to. Get south!

 

[Duffer]

I use Belfield tide plotter on my laptop £11 for a year but not only has secondary tides but also includes tide flow diamonds , its so easy to look at a basic chart and change each hour of a planned passage to see where/when the tide flow swings with arrows (size shows large/small flow) click on an arrow for accurate data speed and direction, also includes a basic distance plotter tool.

http://www.chartsandtides.co.uk/tideplotter

Yes I find that one very useful esp away from the boat plus my C screen on the boat.

 

[peterb]

For those interested in mental arithmetic, try working out the current high and low water times for Port Ellen, on Islay.

 

[Ex-SolentBoy]

iPhone + Marine Tides Planner app from Tucabo

I can do it the RYA way, but why bother?

Snap.