Half Model for Deep Dive Tender - Canadian Navy Project

The Canadian Navy was looking for a ship to provide service for submersibles and deep diving in the early 1970's. This model was produced in the design department and indicates shape, thickness and layout of the plating for the ship.

This model was to serve as part of the design of the ship but when the machinery was added there were stability problems. This meant that an alternative solution was researched and an Italian fishing trawler, ASPS Quarto, built in 1965, became part the Canadian fleet when purchased in 1975. The ship was then brought to the Davie Shipbuilding Company, Quebec, in December 1977 for a rebuild as a deep dive tender. She was commissioned in November 1978 as HMCS Cormorant.

The pictorial record of her conversion and rebuild can be found at HMCS Cormorant photo albums

This half model is currently on display in the main gallery, on the ground floor of The Victory.

Some notes associated with this half model

The story behind the half-hull ship structure model (the Canadian Navy fleet diving support ship project)

Pisces SDL-1 : In late 1960, International Hydrodynamics Co. (HYCO) Ltd. of North Vancouver, B.C. was coming to the forefront of ocean technology with deep-submergence mini-submarines. In an effort to aid this company, the Canadian Government agreed to purchase one of HYCO’s new Submersible Diver Lock-out mini-subs without specifying an end user. The SDL-1 was turned over to the Navy for use. It immediately became apparent that a service tender was required to handle the odd-looking craft.

In Search Of A Diving Tender : The Naval Architecture section in the Department of National Defence (DND) started to consider different design options for a mother-ship to support the SDL-1. In the early 1970’s, at least eight design versions were considered but rejected. The ninth design seemed to satisfy the requirement and was sent to the Naval Design Office, an office set up in the Canadian Vickers Yard in Montreal. Somehow the project was allowed to progress to the detail design stage with hundreds of detail construction drawings produced and would be part of the contract bidding package.

The Half-Hull Ship Structure Model : In the days before the 3-D computer ship design programs, as part of the detail structural design package for a new ships, a large scale half-hull model will be constructed with the steel plating edges marked at the correct locations. This may be used to assist the order and nesting of the steel plates. It can also be used to estimate the weights and centers of gravity of the hull structures.

The End Of The Ninth Design : The Design Office had no weight reporting or controlling program. This seemed to be a common situation in many Canadian design offices and shipyards at that time. There were no estimated weights and centres collected in the Preliminary Design stage and thus no stability studies were performed. At last a weights and centres estimation was done based on the final design package and the following stability study showed that the ship as designed was highly unstable in many conditions and it would not be an easy fix. The project was cancelled and all drawings destroyed, except the half-hull ship structure model that was used as a book shelf in my office for many years.

HMCS Cormorant (ASXL-20) : The Diving Tender Project restarted in 1975 by searching for a ship suitable for conversion to support the SDL-1. An Italian stern trawler, ASPA Quarto, was purchased and extensive conversion performed at Davie Shipbuilding, Lauzon, PQ. The converted ship was commissioned as HMCS Cormorant (ASXL-20) on November 10, 1978. I joined DND to be the Project Naval Architect during the design and conversion of the Cormorant, I was then the Project Manager during the acceptance and warranty phase of the project.

These notes were prepared by Edwin Chan, the DND Project Manager, who coninued his career with DND, retiring as Senior Naval Architect.