TIDAL INFLUENCES.

Auckland Star, Volume LXVII, Issue 193, 15 August 1936, Page 23

TIDAL INFLUENCES.

IN HARBOURS AND RIVERS

EFFECTS WHEN RACING. An interesting talk to yachtsmen on the influence of the tides on yachts in a race, and 'how to make the best use of . the current, also their action and effect in the channels of harbours and rivers, was given on Wednesday evening by Mr. T. McKnight in the Akarana Clubhouse.

Mr. T. McKay presided over an attendance of 40. and said .the speaker for the evening needed no Introduction, being well known to those present.

Mr. McKnight said tides were- caused by the influence of the sun and moon on the earth and showed by diagrams the positions of the three bodies which caused high and low water, also spring and neap tides.

The action of the tide, which usually set from east to west, during the ages on the northern coast of New Zealand, had caused deep Water and high land on the northern or starboard side of a harbour entrance and low-lying banks on the southern side with shallower water. The Whangarei entrance and harbour, also the Wade River, were illustrations of this action. The tide setting in from the east met tlie coast, and as there was no outlet to the west, after going into the various inlets and harbours, it returned and went north. This had the effect of forming eddies and slowed down the current on the southern side as the tides met, and sand and mud. from the river w»s deposited on the southern side when the tidal streams slowed down, forming shallows and banks. This action had taken many thousands of years to bring about the conditions- with which we were familiar, but the old adage of water wearing away tlie "stone applied, and the tidal effect had been. to dig out deep channels on tlie side where the stream ran strongest, causing bold headlands with deep water close iii.

Wherever there-was an island or other obstruction to the course-of tlie tide banks were formed out from the obstruction, their leiigth being governed by the length of the island, tlie bank being equal to the face of- the obstruction.

The tiildl effect on the course of a river was also shown on a. . blackboard, the natural tendency being for the ebb tide to run a course as straight as possible from one point .to another. This had tlie effect, Mr. McKnight said,'of making deeper water off the points In a river with shallower Water inside the bends. This was due to the action of the tide scouring out the channel where it ran faster, and dropping deposits' where the stream was slowed down out of the line of tlie current. Again, Whni*arei Harbour and the Wade River entrance were used as examples of this action.

The, effect of the tide on Brown's Island in the mouth of the Tauiakl River was also mentioned, with its shallow water facing the outflow of the - tide, ■ also ' the Srndspit off Devonport. The Tamaki River was used as an illustration of the deeper water keeping in a channel approximately from point to point.

Tidal Effects In a Race. The second part of the lecture dealt with the effects of the tide on a yacht when racing or cruising. Mr. McKnight instanced the strong rip off tlie eastern tide deflector with an ebb tide, and liow it was possible, by keeping close in to the wall when working up ngainst a southwester, to dodge a lot of tidal influence. He instanced a race of the Anniversnry ltegntta two or three years ago, when the keel yachts Prize and Little Jim and the 22-foot centreboarders Valeria and Venus rounded the compass dolphin together. The keel yachts, although faster, stood straight up harbour for the finishing line, but tlie two centreboarders kept close in to the tide deflector wall, and as soon as they could do so they stood inshore clear of the end of the wall, making a board out of the tide before standing up for .the finishing line. The two mullet boats finished ahead of the keelers, one being 4m and the other over 2m ahead. In a race to tlio TtVade Kivor, about 10 years ago. the speaker said that in a light northerly wind and an incoming tide the yachts which worked close in to | Cheltenham Beach, Narrow Neck and all the bays between there and the Waue entrance, got a decided advantage over the boats which stood towards Rangltoto Beacon in the full strength of the tide, and all finished well ahead of the boats out in the tide. ... These effects were also obvious in a race held by the Richmond Club from Ponsonby I wharf, round the Rona buoy off Nortlicote, and from that buoy to Beach Haven, beating against tide and wind. By working close inshore several boats came out ahead, at times getting the ebb tide under their IC< After the lecture a general discussion ensued, and Mr. McKnight answered several questions. The chairman called on Mr W. A. Wilkinson, as .ex-commodore of the club, to propose the Vote of thanks. Wilkinson said his experience bore out all that the lecturer had said about the deeper water being on- the northern side of harbour entrances on the northern coast. There were exceptions, he pointed out. Entering Tauranga Harbour the deep water was on the eastern side, with sand bunks on the west or starboard hand of the entrance at Te Mount. Whitianga (Mercury Bay) and Talrua were the same. Coromandel Harbour had its deeper water on the western side. This might be due to effects reversing the strongest set or the tide. It was well known to all racing shippers that most was to be gained by keeping out of the tide, but the wind was also a big factor, and he instanced a race from North Shore wharf to Kawau about 20 years ago in a light northerly Wind and Hood tide. The lead icand others had secured by working close in along the Lake shore was nullified by a change of wind to the north-west, allowing the boats which had kept further out in the channel to lay right through Wliangaparaoa Passage, and fetch Bon Accord in one long leg. He was sailing "lijstle, Which was well ahead of the Mahaki. to Which she was conceding om, but Mahaki saved lier time easily and won the race, tlifi other leeward boats taking the other Pr Thev were all interested In the subject of the lecture, said Mr. Wilkinson, and he thanked Mr. McKnight for his very clear explanations and diagrame on the subject. Mr R L. Stewart, in seconding the vote of thanks, said that when beating up the harbour against a strong* breeze and ebb tide it was often possible to lay close enough to the wind to bring the tide under the yacht's lee bow. When this was possible he preferred to hold on up harbour Instead of making boards into each bay. The speaker gave several other instances where these tlictics had proved SU In C acknowledging the vote of tianks, Mr. McKnight said that it was usually in light winds that the tide had most effect. Another factor in light weather was the action of the sea. Even against the tide the effect or set of the sea could be noticed. He was sure that it was the effect of the sea from the east that had set^ the leddy so close inshore and had caused her total loss off the end of Kawau. - Mr. Brl '{'S Tambs agreed with this, added Mr. JlcWednesday week the president, Mr. . -Len Heard, will give a talk on Deep Water 'Fishing," illustrated by a series of cinema views of sword-fish catching off Cape Brett and Mercury Island. These views give striking pictures of sword-fish leaping and being landed, and Mr. Heard Is sure of a large audience.

CATCHING CRAYFISH.

A DAY'S SPORT AT KAWAU.

An. Auckland yachtsman, who was spend-1 ing a 'holiday at Kawau, was invited by i Mr VickerstuiT to accompany him 011 a crayfishing trip 011 hoard Skipper Bennie Woodhead's launch Kosa, lying in Vivian s Bay The genial skipper is a hard worker, and makes and mends all his own pots on board the launch. Getting under way early, the launch was headed out through the north passage towards Takatu. The first job was, to get bait for the 2-i pots. The skippers keen eye spotted the birds working a siioal of kahawai about two miles olt towards Canoe Kock, and the launch was soon amongst them. Good hauls of kahawai were got 011 three spinners, and GO fine fish were landed in a short time. The boat was then headed inshore, and after breakfast, to the accompaniment of music from lI'A. for the launch had a good set aboard, bait was cut up, and one after another the pots, which had been put down I the day before; were lifted, emptied, rebaited, and put down in the fresh place. The pots varied from two to 21 crays each, mixed with other visitors, including octopi, conger eels, butterfisli, blue cod, snapper, leather jackets, rock cod, etc. After attending to all the pots, the launch was headed back to Vivian Bay, where the 200 crays were put into five big storage pots, to be kept alive and fresh, ready to be taken to Auckland in time for Friday's market. The visitors were landed, -each with a good bundle of sclinapper and blue cod, after thanking Bennie and his mate for the outing. ANNUAL MEETINGS. August IS —Point Chevalier Sailing Club. August 27 —Victoria Cruising Cluh. September I~>—Ponsonby Mode! Yacht Club. September IC—Akarana Yacht Club.

YACHT HO-HO SAILS. The Norwegian yaclit Ho-Ho, which arrived from Norfolk Island on July 3,#9 have some repairs to her hull, which was damaged when she went • ashore at Ball Bay, on the island last year, left Auckland on Tuesday afternoon on lier return. Her owners, Messrs. T. Osmoen, B. Brylin and T. Scliyberg, were accompanied, by Messrs. Jenkins, Christian and Nobbs, residents of Norfolk Island, who arrived with the yacht. The wind was westerly when the yacht left, and sail was made after -rounding North Head. She made good time past Tiritlri, being reported at dark well to the north. During the night the wind changed to the nortli-east, and the Ho-Ho put into Urquliart's Bay, Whangarei Heads, leaving again when the wind changed on Thursday. Light westerly winds have prevailed in Auckland since then, but vessels coming in report fresher breezes at sea, and the Ho-Ho should make Norfolk Island about Wednesday. They carry pleasant recollections of Auckland with them back to Norway.

DIESEL ENGINES POPULAR. Engines built on the Diesel principle and burning heavy oil fuels, costing Od or -7d per gallon against the current price of petrol of 1/10, less rebate, have proved their reliability without doubt for trading vessels. Matua, the Union Company's new boat for the Island trade, which arrived on Thursday, is one of the best installations south of the line. . ' . , It is estimated by those in the trade that «fully 75 per cent of working. vessels now building are to be fitted with heavy oil-burning engines. While their efficiency and economy has been proved and accepted, in the big jobs, there has always been doubts of their suit; ability for pleasure craft. Some of the earlier engines tried out here were anything but perfect, their odorous and noisy exhaust telling against them, in addition to their excessive weight and cost. • L -

These were factors which experimental engineers in the world's best factories were striving to; overcome, and the present engines can be said gto be without these faults, judging by the;way they are being installed in pleasure craft in' Great Britain and the United States. :

A few have been installed In local pleasure craft, and are giving satisfaction to their owners. Even the operation of starting from .cold is .now reduced to a few minutes. Tlie advent of a. really reliable heavy oil engine will do. much to encourage the sport of motor boating here. GUESSING THE DAILY RUN.

One way to pay your fare; across the Atlantic, and have a handsome margin to spare, is to win the, pool on the day's run' of a. big ocean liner. The Queen Mary's passengers laid heavy wagers on the distance to be covered each.day on her maiden voyage, and some of the pool's daily totals ran into four figures. But it will be hard for even the, Queen- Mary to beat the Berengaria's record of £1700 at the heightof the American boom. At the other end of the scale wliat must surely: have been "an all-time low," as tlie Americans say, was the £20 wagered by the Majestic's passengers one day when, crossing to NeW

York five years ago. That was in the depth of the slump, and there were only a few score aboard the great liner. Passengers may win nice little fortunes in good times:/but the-man who makes a steady income from the pool is the smokeroom steward. He acts as banker, and gets a useful commission for the service. In the "good old days" before the slump the smoke-room steward aboard a big liner generally made several times as much as his captain's salfcTy.