January, 1951, Canadian Aviation
The 140-ton Saunders-Roe Princess flying boat may be airborne about the middle of this year. Involving, as it does, unique problems in aircraft construction, this project is of universal interest. The following are notes supplied by the Saunders-Roe works superintendent, E. Goodenough, giving some of his Princess impressions.
Following the production of small amphibious aircraft, the thought of manufacturing the Princess seemed a prodigious task.
Standing on the floor of the erection shop one tried to visualize the Princess in position – the bow almost touching the main doors, the stern extending three quarters of the length of the shop, the inner wings alone nearly reaching the side galleries and the fin tip way up in the roof trusses. It was hard to realize that one aircraft would practically fill this shop.
When the first drawings were received we learned that there would be many problems to solve. Firstly, the cabin portion of the hull was to be airtight and would be operated at a pressure of 8-lb to the square inch. Having produced watertight hulls for many years, we decided that with extra care and attention to fairing of frames and stringers, pitching of rivets, extreme cleanliness when making joints, and close bolting when assembling the plating, we could satisfactorily obtain the desired result.
A smooth external finish was required – most aircraft manufacturers are able to achieve this finish by ‘shaving’ off the standing rivet heads or by using a filler on underflush rivets. However, we were unable to adopt either of these methods because (a) rivets heads were to be anodized and (b) the aircraft was not to be externally painted.
Bearing in mind the required pressure tightness, it was agreed that underflush rivets would not be satisfactory and it was therefore necessary to design a controlled depth countersink. On airfoil surfaces fine limits are used, thus reducing the maximum protuberance to .0015 in.
The assembly of the engine mountings needed much care owing to shrinkage of the tubes after welding and here it was found necessary to lay down a strict procedure for the sequence in which the welds were to be carried out – the amount of shrinkage allowance was decided after extensive tests.
The first step toward erection was the moving of the hull to the centre of the shop and the pull required to achieve this was approximately three tons. The next step was assembling the tail portion to the hull. The plans for this were very carefully checked several times because at this stage the tail had to be turned into its vertical position. The slinging points were from the tail plane attachment holes and as it was lifted it had to be calculated that it would pass over the top dead centre and lay at an angle of 10 degrees. Fortunately, these calculations were quite correct.
After this, the erection of the inner wings seemed a comparatively simple job, particularly as the surface gauges had served their purpose efficiently and after lifting the wing we were able to bolt the two together immediately. Mention should also be made of the considerable amount of staging that has been required in the construction and assembly of the Princess. This is obvious when one realizes that from the ground to the top of the hull is over 25 feet, while to get to the tailplane tip one has to ascend 38 feet from ground level.
For those who are interested in statistics, up to two and three quarters acres of light alloy plate, ten miles of extrusion and forty miles of electric cable and millions of ruddy rivets have been used in each aircraft.
This article originally appeared in the January, 1951 edition of Canadian Aviation.