Tide Constants

[Vegable]

Just planning a solo sail from Arisaig to Pwllheli in 2 weeks time and plan on departing from Scotland after overnighting in The Sound of Gigha.
In the sailing directions for the Sound of Gigha it states after N going and S going times:-
"Constant is approximately -0200 Oban (+0500 Dover) at springs, and -0500 Oban (+0300 Dover) at neaps"
And after 28 years of big boat sailing I suddenly realise I haven't a clue what it means. Mr Google has said something about harmonic tides and simple tides and has left me no wiser.
Can any one enlighten me please
Mike

 

[VicS]

Just planning a solo sail from Arisaig to Pwllheli in 2 weeks time and plan on departing from Scotland after overnighting in The Sound of Gigha.
In the sailing directions for the Sound of Gigha it states after N going and S going times:-
"Constant is approximately -0200 Oban (+0500 Dover) at springs, and -0500 Oban (+0300 Dover) at neaps"
And after 28 years of big boat sailing I suddenly realise I haven't a clue what it means. Mr Google has said something about harmonic tides and simple tides and has left me no wiser.
Can any one enlighten me please
Mike

Add ( when positive) subtract (when negative) the figures ) 0200, 0500, etc to/ from the times of HW at the standard ports Oban or Dover to get the times at the secondary port ( or in this case the Sound of Gigha)
Interpolate for tides between springs and neaps.

From the almanac the north going tide begins at HW Oban + 0430 and the south going at HW Oban -0155

 

[Vegable]

Thanks Vic.
As soon as I read your answer it came back to me. A senior moment.
Mike

 

[guernseyman]

An important word is 'approximate'.
Also, the differences will change during the lunar cycle.

 

[BelleSerene]

An important word is 'approximate'.
Also, the differences will change during the lunar cycle.

Indeed so. Pretty silly for the author of those sailing directions to call it a ‘constant’.

 

[Baddox]

I believe that Gigha is near an amphidromic point, so the tide range and rate are likely to be unusually small there.

 

[lw395]

An important word is 'approximate'.
Also, the differences will change during the lunar cycle.

That's why they give a springs figure and a neaps figure.

 

[lw395]

I believe that Gigha is near an amphidromic point, so the tide range and rate are likely to be unusually small there.

Height range is small, doesn't mean there's no stream though.
ISTR nearly 2 knots?