Confessional: admit to boat-related things you've never quite understood...

[nigelmercier]

All the car-type thermostats I have seen, including the one on my Yanmar 1GM10, use expansion and contraction of wax as the driver.

+1

 

[Uricanejack]

As nobody's offered, here's my explanation - and I'm assuming you refer to the tabulated time differences of HW at the Secondary and Standard ports being dependent on whether it’s Springs or Neaps.

At every location, the tidal curve varies with the Spring/Neap cycle, as one clearly sees with the published curves for Standard Ports. But the relationship between the tidal curves for different locations also varies with the Spring/Neap cycle, such that the time differences of HW (for example) between Standard and Secondary Ports vary between Springs and Neaps.

Now that’s not a mechanistic explanation I appreciate. For that, one needs to ask why the relationship varies. The basic answer is that tidal curves are complex functions of the interaction between tidal forcings and local topography, and there is therefore no reason why the tidal curves for the Secondary and Standard Ports should necessarily keep in lockstep through the Spring/Neap cycle.

Ok here is my attempt to confuse the issue.

Each tide cycle is bound to be slightly different from each other cycle. The durations will vary along with the ranges each being a unique curve.
So the printed curve must be an approximation or an average, split into to different averages for the difference in ranges.
If the curves are for a specific port. Other similar ports in the vicinity use the time differences as an approximation. There can‘t be a sudden difference between springs and neaps its just a means of rounding up or down..

Perhaps I should leave it to Kipling’s suggestion 'its just so".

 

[NormanS]

Oh yes, very clear and concise. But when the tide goes out, where does it go?

 

[prv]

Typical thermostats have a flap in the centre that opens as the water temperature rised and closes as it cools down.

This made possible by the use of a bi-metal spring or strip that expands or curves with heat and pushes the flap open allowing more flow as it heats up and less flow as it cools down.

Somehow I don't think Vyv of all people was asking for a primary-school explanation of how a general thermostat works

Pete

 

[john_morris_uk]

Oh yes, very clear and concise. But when the tide goes out, where does it go?

I am never sure whether these questions are serious or not?

If you get a copy of Reeves-Foulkes you get little 'thermometer' style images of where the tide is and what it is doing. As you flick through the pages, you can see the 'wave' of tide rise and fall in different parts of the channel of the UK.

So the answer is that when it is out somewhere, it is in somewhere else.

(Hence the tidal streams as water flows from one are to another…)

Seemples

Actually its a lot more complex than that and you need the Admiralty Manual of Tides to get a sound introduction to the various and multiplicity of harmonics that combine to allow one to calculate what the tide is doing at any one time which is why we all pay for tide tables.

 

[nigelmercier]

But when the tide goes out, where does it go?

The Philippines.

Too soon?

 

[NormanS]

I am never sure whether these questions are serious or not?

The clue is the

 

[john_morris_uk]

The clue is the

Apologies, I was on my phone and the smiley didn't show up very well!

 

[Davegriff]

Can't find where someone asked about 'red port' now, but I was taught as a yungun re bouyage:

'No red port left in the bottle'

as in:
'... red bouy ... on the left when going in to port'

Keen to see answers to question re volvo thermostat. Always surprised how many people on here seem 'know' the answer but obviuosly dont understand the question...

 

[alant]

Can't find where someone asked about 'red port' now, but I was taught as a yungun re bouyage:

'No red port left in the bottle'

as in:
'... red bouy ... on the left when going in to port'

Keen to see answers to question re volvo thermostat. Always surprised how many people on here seem 'know' the answer but obviuosly dont understand the question...

Try not to confuse it with "Red Right Returning"!

 

[JumbleDuck]

Try not to confuse it with "Red Right Returning"!

In fourteen hundred and ninety two
Columbus sailed the ocean blue.

In fourteen hundred and ninety three
Columbus sailed the deep blue sea.

 

[NormanS]

Can't find where someone asked about 'red port' now, but I was taught as a yungun re bouyage:

'No red port left in the bottle'

as in:
'... red bouy ... on the left when going in to port'

I was taught "There is EVEN no RED PORT LEFT in the BARREL", which at that time told you the numbering of the buoys, and even their shape.

 

[dancrane]

Isn't it easier to remember that green, right and starboard are all 5 letters or longer...while red, left and port are all four or fewer?

 

[john_morris_uk]

Isn't it easier to remember that green, right and starboard are all 5 letters or longer...while red, left and port are all four or fewer?

I think its a case of whichever is easier for your.

I was originally taught no red port (wine) left, with the remark that port usually comes in bottles and one day it might come in 'cans'…!

 

[dancrane]

I was originally taught no red port (wine) left, with the remark that port usually comes in bottles and one day it might come in 'cans'…!

Ah. But surely most port is sold in bottles made from green glass?

 

[Hydrozoan]

Each tide cycle is bound to be slightly different from each other cycle. ... Perhaps I should leave it to Kipling’s suggestion 'its just so".

Yeah but, no but ... there must be at least a broad consistency in the differences between the HW times at the Standard and Secondary Ports, both at Springs and at Neaps, for the tables to work at all. As to 'it's just so', I suppose my last sentence ('The basic answer is that tidal curves are complex functions of the interaction between tidal forcings and local topography ...') is almost saying that - for most of us at any rate! No doubt with detailed hydrodynamic modelling of the situation at a pair of Standard and Secondary ports, one could get an understanding of why the HW time differences varied between Springs and Neaps - "The sandbanks at the mouth of Y (Secondary Port) affect the inrush of the tide differently at Springs and at Neaps, an effect absent at X (Standard Port)" sort of thing.

My thanks to NormanS for his compliment on my original answer. As to his follow-up question "... when the tide goes out, where does it go?", I cannot better the accuracy of John Morris's "somewhere else", but will offer the more specific - and thus far more helpful - "Ultimately, to where it came from when it came in".

 

[john_morris_uk]

Ah. But surely most port is sold in bottles made from green glass?

Don't start confusing the issue with facts!





PS. The Port is still RED and it might come in a CAN one day and that's whats stuck in my mind and that's all that counts really…..

 

[john_morris_uk]

My thanks to NormanS for his compliment on my original answer. As to his follow-up question "... when the tide goes out, where does it go?", I cannot better the accuracy of John Morris's "somewhere else", but will offer the more specific - and thus far more helpful - "Ultimately, to where it came from when it came in".

PS If only it was true… but we won't muddy the waters (geddit) with shore drift phenomena...

 

[RobF]

Yeah but, no but ... there must at least a broad consistency in the differences between the HW times at the Standard and Secondary Ports, both at Springs and at Neaps, for the tables to work at all. As to 'it's just so', I suppose my last sentence ('The basic answer is that tidal curves are complex functions of the interaction between tidal forcings and local topography ...') is almost saying that - for most of us at any rate! No doubt with detailed hydrodynamic modelling of the situation at a pair of Standard and Secondary ports, one could get an understanding of why the HW time differences varied between Springs and Neaps - "The sandbanks at the mouth of Y (Secondary Port) affect the inrush of the tide differently at Springs and at Neaps, an effect absent at X (Primary Port)" sort of thing.

My thanks to NormanS for his compliment on my original answer. As to his follow-up question "... when the tide goes out, where does it go?", I cannot better the accuracy of John Morris's "somewhere else", but will offer the more specific - and thus far more helpful - "Ultimately, to where it came from when it came in".

The bit I've put in bold is the best explanation I've heard. Fluid dynamics was never my strong point, so I suspect I'll remain ignorant on the precise rationale.

 

[Hydrozoan]

… but we won't muddy the waters (geddit) with shore drift phenomena...

OK - I geddit :biggrin-new: http://www.youtube.com/watch?v=1gNs-29s-0Q