So I completed the RYA course on these more by luck than judgment but I still can't make head nor tail on these
Anyone know how to do them properly lol
I'm using an app from the tidal press website
My mooring dries out at low water in what seems to be no time at all I think it's -3.6m but I don't get a reading far enough up the creek to work it out so only have that figure to go by.
If at low water the reading is 0.6m
That gives me a dry height of 3m ?
At high tide I usually have around 1m under the boat on a 5.6m tide
Anyone know how to do them properly lol
I'm using an app from the tidal press website
My mooring dries out at low water in what seems to be no time at all I think it's -3.6m but I don't get a reading far enough up the creek to work it out so only have that figure to go by.
If at low water the reading is 0.6m
That gives me a dry height of 3m ?
At high tide I usually have around 1m under the boat on a 5.6m tide
In reply to Post #1
Charts are all well and good but In my experience better to go by actuals for your situation.
Find your nearest tidal buoy on UK National Tide Gauge Network https://www.ntslf.org/data/uk-network-real-time and take an actual depth reading under your hull at a certain tide reading on gauge. What ever the difference is, you can adjust the live gauge reading to know the depth in your creak.
For example if the buoy reads 5m and you measure 1m under hull, you will have water under hull provided the buoy reads 4m or higher.
The graphic on the Network, saves you needing to get the calculator out you can do it by eye.
I use this very similar in reverse to work out air draft under a bridge to get out of my harbour. It works well as long as no local environmental factors affect the tide between gauge and mooring.
Charts are all well and good but In my experience better to go by actuals for your situation.
Find your nearest tidal buoy on UK National Tide Gauge Network https://www.ntslf.org/data/uk-network-real-time and take an actual depth reading under your hull at a certain tide reading on gauge. What ever the difference is, you can adjust the live gauge reading to know the depth in your creak.
For example if the buoy reads 5m and you measure 1m under hull, you will have water under hull provided the buoy reads 4m or higher.
The graphic on the Network, saves you needing to get the calculator out you can do it by eye.
I use this very similar in reverse to work out air draft under a bridge to get out of my harbour. It works well as long as no local environmental factors affect the tide between gauge and mooring.
In reply to Post #2
Yup I'm using the bee ness tide
And I know the basics of it with my draft etc,
I don't want to get caught out high and dry when I'm out lol and wait 12 hours to get back
If I read another place slightly down tide of mine it is -4.6m at low tide (what I actually think it is)
It goes out stupid fast where I am I was in 3 foot of water when I started flushing the engine, by the time I had flushed it the mooring was dry.
15/20 minutes tops
Yup I'm using the bee ness tide
And I know the basics of it with my draft etc,
I don't want to get caught out high and dry when I'm out lol and wait 12 hours to get back
If I read another place slightly down tide of mine it is -4.6m at low tide (what I actually think it is)
It goes out stupid fast where I am I was in 3 foot of water when I started flushing the engine, by the time I had flushed it the mooring was dry.
15/20 minutes tops
In reply to Post #3
Sure, what i meant was use a buoy for a live reference against a known water depth on your mooring rather than use tidal height charts, which are a just a prediction.
Unless you know the accurate differential between the mud under your hull and the chart datum point used its always going to be a guess, from what you describe sounds like you need to be as accurate as possible.
I think with creeks, bridges, etc that's the most accurate way as you can monitor tide height with a live reference. Wind direction, tide cycle, and a lot of other factors can effect a paper
Just look up the live tide height at your minimum operating depth and then you know what live tide height you need to be on your mooring. Then you don't need to do the charts or calc the live graph will give you what you need.
For example, regardless of what I calculate use tide predictions, rule of twelves, making allowance for wind direction in the North Sea. If I monitor the lowestoft buoy when I am out I know if the tide is above 2.2m then I need a bridge lift to get back to mooring as I won't have enough Air draft. Never fails, but can be quite a bit earlier or later than I expected based on charts.
Once you know what your minimum working tide height is on the live buoy then you can plan your trip around that just by looking at the tide graph. For me I can just draw a line at 2.2m through the graph, the time above that line is when I need to be at sea, the time under the graph is when I can come in. For you would be the other way around.
The shape of the live graph on that link will also give you an idea of speed of tide and allow you to estimate when you think you need to make a move home.
Hope I have got that across better this time.
Sure, what i meant was use a buoy for a live reference against a known water depth on your mooring rather than use tidal height charts, which are a just a prediction.
Unless you know the accurate differential between the mud under your hull and the chart datum point used its always going to be a guess, from what you describe sounds like you need to be as accurate as possible.
I think with creeks, bridges, etc that's the most accurate way as you can monitor tide height with a live reference. Wind direction, tide cycle, and a lot of other factors can effect a paper
Just look up the live tide height at your minimum operating depth and then you know what live tide height you need to be on your mooring. Then you don't need to do the charts or calc the live graph will give you what you need.
For example, regardless of what I calculate use tide predictions, rule of twelves, making allowance for wind direction in the North Sea. If I monitor the lowestoft buoy when I am out I know if the tide is above 2.2m then I need a bridge lift to get back to mooring as I won't have enough Air draft. Never fails, but can be quite a bit earlier or later than I expected based on charts.
Once you know what your minimum working tide height is on the live buoy then you can plan your trip around that just by looking at the tide graph. For me I can just draw a line at 2.2m through the graph, the time above that line is when I need to be at sea, the time under the graph is when I can come in. For you would be the other way around.
The shape of the live graph on that link will also give you an idea of speed of tide and allow you to estimate when you think you need to make a move home.
Hope I have got that across better this time.
In reply to Post #4
I have made a depth gauge for when I go down there next time spaces 150mm apart
I'm going to sit and watch a complete tide and time it
It's getting moved later in the year or early next year to an all tide mooring hopefully 🤞make
It so much easier..
Luckily I only need 450mm to get the boat out as I can go on a sHallow water setting on the engine if needed don't want to do that too often though
My technical way of testing atm is. Rock the boat if it moves I can go haha
I think minimum tide is around 5.1m/5.2m if I use the “guessed” datum as -4.6
4.97 was just enough to rock the back of the boat but the front wouldn't slip
Wish I measured it or looked at the time on Saturday when I took it out
Cheers for the advise though
I have made a depth gauge for when I go down there next time spaces 150mm apart
I'm going to sit and watch a complete tide and time it
It's getting moved later in the year or early next year to an all tide mooring hopefully 🤞make
It so much easier..
Luckily I only need 450mm to get the boat out as I can go on a sHallow water setting on the engine if needed don't want to do that too often though
My technical way of testing atm is. Rock the boat if it moves I can go haha
I think minimum tide is around 5.1m/5.2m if I use the “guessed” datum as -4.6
4.97 was just enough to rock the back of the boat but the front wouldn't slip
Wish I measured it or looked at the time on Saturday when I took it out
Cheers for the advise though