Solution near of navigation problems at Willemstad Harbour

Fig. 1 Studying the navigation [or the harbour of Willemstad in Curaçao in the open-ocr taooratoru "De VOQ1'st"subdivision of the Hyd?'a,ulic

LaboTatO?'yat Delft

Solution near of navigation

problems at Willemstad Harbour

In the open-air laboratory "De Voorst" , sub-division of the

Hydraulic Laboratory at Delft, a study of the navigation problems for the harbour of Willemstad in Curaçao has been completed. In St.Anna Bay, especially large ships sometimes meet with hindrance from a strong current along the entrance, which have repeatedly caused damage. Delft engineers and their co-operators are engaged inengineering projects which should clear this nuisance to navigation. The cost of these engineering works naturally cannot be estimated before they are definitely projected.

Natural

harbour

lished at this ideal fairway, and

con-ducts alively traffic withtankers sail-ing under the flags of all nations, These,and numerous other ships, ap -proach fromtheCaribbean Sea through the St.Anna Bay,a natural channel betweenthe outer water andtheinner lake, called the Schottegat, at which the refinery of theC,P.I.M.is situated,

On both sides of this channel is the Theharbour of Curaçaoisoneof the

pleasantest and safest natural har-boursin the world,For several ce ntu-ries shipsofmany types andsizehave berthed there and, in consequence, brought prosperity totheisland. Since 1915the N.V. Curaçao Petroleum In-dustrie Maatschappij has been e

town of Willemstad, connected on the seaward side by apontoon bridge. This bridge may readily be called Willem -stad's Achilles tendon, because were it damaged by navigation, then the tra f-fic between both parts of the town,

Punda and Otrabanda, would beblock -ed and no other route is available than that round the Schottegat (20 km). Plans for a fixed bridge over St. Anna Bay have been discussed, but the high cost and other problems weigh too heavily for the present.

Difiiculties fOl·tankers

The st. Anna Bay is a magnificient navigation water and a safe harbour, but nature onsome dayshas in store an unannounced and disagreeable sur -prise. A fewtimes every year, at the entrance of theharbour,a current runs along the coast, from East to West, causing especially to large, modern tankers, difficulties. It may happen that the stem of a tanker having a l-ready reached tranquil water still has its stern exposed to thepressure of the stream, sometimesrunning ashigh as two knots with the resulting difficulty of foreseeing and correcting the cha n-ges ofdirection that can occur. Already many casesof damagehave occurred, sothe parties concernedwith this pro-ble-mare nowtaking measuresto con-trol the danger: besides the Govern -ment the parties are the shipowners, ofwhomwecan mentionthe N.V. Cu-racaosche Scheepvaart Maatschappij (Curacao Shipping Co.Ltd.) and the Koninklijke Nederlandsche Stoomboot Maatschappij (Royal Netherlands Steamship Co).

The Netherlands, the country where hydraulic engineering plays an impo r-tant role, is able to study such que s-tions in its laboratories, oneof which is situated in the Noordoostpolder op-posite the point of Vollenhave, "De Voorst,"afterwhichit hasbeen named. It formsa part of the laboratory esta -blished at Delft.

St. Anna Bay in miniature

For studying the problemsof St. An-na Bay, amodel oftheharbour mouth was set out on a length of 1 : 64 III a contour of chally sand stone and concrete. The coast line and side of the water have been very accurately maintained, also the depths in the channelas wellasinthe seahavebeen executed in the right proportion.A set of sluice gate'valves in the inlet and outlet ditchesenablesthe height of the water andthe speedof thetreacherous 292

stream to be regulated. As "guinea -pig" a woodenmodel of a 28,000ton "Velutina" classtanker isused, which is being electrically propelled. By means of a switch box connected by cable to the model,the motor can be rotated with the required speed and the rudder operated. Should the cable be allowed to betowed by the model, then this burden would probablymake navigation impossible and would cer -tainly make the results quite wor th-less. An aide therefore walks over small bridges in the sailing direction of the tanker and bears the current cable ona strong fishing rod, without influencingany movementsof the mo -del.Of course,itwouldalso bepossible to use radio steering, but preference was given to this simple method. It would be expected that the speed of the sea streaming andthat ofthe ship modelwould be identical to those e x-perienced in reality. However, it a p-peared that a fixed proportion exists between thereduction ofthemodeland the acceleration of time. What occurs with the originalwithinan hour takes place in about71;2 minutes in a model of scale 1 :64,sothat a model tanker requiring a certain routine from the test engineèrgives thecontrollersta nd-ing on the bridge (behind the switc h-box) bar-elya minute to carry out a function for which his counterpart on a tanker's bridge would have about eight minutes.Howevercaptains, mem-bers ofacommitteeofvisitingexperts, quickly caught the trick and could in this way test their experiences and viewsandexchangeopinions.Onecame tothe conclusionthat thismodelshow -ed clearly whichthings must NOT be done, an apparently negative though valuable conclusion.

Engineering

works

From the set-up of this section of Curacao will be planned the eventual layout of the engineeringworks needed to improvethesituation: abreakwater, a channelandthe like.Bythe simplest means the required conditions can be brought into or taken out of use, and bythe manipulation ofslidevalvesthe speed ofstreaming can bealtered. By spilling a red colouringmatter the pro-gress of the stream can easily be ob-served.

Theconclusionsof thesetests onthe suggested improvements have been reported. Itappeared that this model is a worthwhile expedientto improve the sometimesmostinconvenient s itu-ation at the entrance ofthe St.Anna Bay.