According to the RWYC, 'The Slack' in the Swellies can be expected between L.pool -2.15 and L.pool - 1.45,Menai Straits Tides at a Glance which as we have seen depends upon a permutation of six primary variables :- the interval bewteen HW at Menai Bridge and Port Dinorwic, variations in the Liverpool Tidal Constant, Atmospheric Pressure, the height of the tide, the strength and direction of the wind, and the extent of Residual activity. It would therefor be naive in the extreme for us to believe it in any way possible to determine in advance the time when 'The Slack' will begin and end on any given day, yet page 1 of the Investigating Sub-Committee Report is almost entirely devoted to describing the compilation of a detailed timetable solely to ensure that the ship entered the Swellies at the precise time that evidently it was firmly believed that a ten minute slack would begin. No account whatsoever was taken of the possible effect of wind and weather on the tide, which was quite extraordinary for an establishment whose sole raison d'etre was to teach seamanship and navigation to others. The Report concludes this section with: " It would seem therefor, that the timing of the passage as planned was correct." But notice that the word "timing" in the Report is underlined, which is the only word in the whole Report which is underlined. (After all, we are dealing with natural forces, and Nature is a notoriously bad timekeeper.)
High Water Liverpool that morning was 11.18 a.m. (height 10.01M against today's revised Datum)Admiralty Tide Tables We have seen how the outward move was made by strict adherence to a predetermined timetable. Speaking of the final full meeting before the tow departed Capt Durrant states: "At this meeting the exact timing of each point of the move was finally fixed and agreed upon. It was stressed that the critical point of the timetable was the time of passing under the Britannia (railway) Tubular Bridge which was to be at 9.20 a.m."Durrant P_2.line 7 I'm unable to say whether the pilot, as he made his way to the ship, was aware of the worsening weather conditions in the Irish Sea or not. But certainly he would have been immediately aware of anything unusual about the tide in the Strait, which amounts to the same thing. However upon boarding he expressed the view that he thought the ship 'a bit late'. (verbally - Emrys Jones - Caernarvon Pilot) Nevertheless he showed no reluctance to proceed with the tow, and the ship duly slipped her mooring at 0815. However, when about 0850 Captain Hewitt had the ship brought up at Pwllfanog the pilot objected strongly: "Oh no Captain, we must keep her going." To which Captain Hewitt replied very firmly: "The ship goes under the bridge at 0920 hours and not one moment before." (verbally - Emrys Jones)
We've seen why in the Menai Strait the higher the tide the shorter is the period of ' Slack',(page 3.) and that a wind in the Irish Sea with a northerly component will further curtail its duration, (page 5 - The Wind) so that on the day in question with the highest tide of the year and a force 6/7 (gusting up to 10) northwest wind we cannot be at all surprised by Capt Durrant's observed: "The anticipated 10 minute slack water period did not materialise. The south going Ebb Tide set in immediately (the flood ended) at 9.20 a.m."(Durrant p_4 line 3) (Captain Durrant was not a local, and not familiar with the oddities of the Menai Strait tides, so we do have to excuse him for believing that slack water was synonymous with high water. This leaves me with having to point out that in attempt to clarify what he says, in this instance only I have paraphrased his statement.)
At 0940, after the head tug had struggled for 20 minutes with diminishing speed as 'The Ebb' relentlessly gathered momentum, Capt Durrant (now on the Suspension Bridge) describes the ship as still three or four hundred yards short of the bridge and making no further progress(see also Note 13) when, by carefully timing Kelp weed borne on the tide he estimated that in that 20 minutes the tide (which he describes as already having the character of a race) had already reached a rate of 8 or 10 knots. Blue Funnel Pilot James Miller described it as: "not a true tide, but a confused mass of swiftly running water". The Menai Strait Pilot stated that conditions had become abnormal. 2nd Officer GAB King said the stern tug found it almost impossible to come astern against the tide sufficiently to slack the towing springs so the slip-hook might be knocked out. (It took 20 minutes before the tug finally freed herself from the ship. (loss - page 10) Lt. Commander Brooke-Smith stated: "The tide suddenly came down like a mill race". Stern tug skipper Cooper said that after letting go from Conway's stern, his tug was "going every ounce she could go (10 knots) but was still going astern. The tide was most severe." Observers on the shore spoke of: 'something like a Tidal Bore'.
However, elsewhere on the Web an inexperienced young man has dismissed the opinions of all these highly experienced observers as "An unnecessary exaggeration", and instead he bases his ' Five minutes earlier theory ' on the standalone measurements he took on a single solitary tide in the totally opposite conditions of a southerly wind. He bases his figures on an 'assumed' "4 knot towing speed" (on the passage from the Mersey