Sea Airdromes

Manawatu Times, Volume LIII, Issue 6667, 21 July 1928, Page 5 (Supplement)

Sea Airdromes

ENGINEER PLANS MODEL Anchored by Suction ' \ EDWARD R. ARMSTRONG, a research engineer on the staff of the du Pont de Nemours Company at Wilmington, Del., after fifteen years of experimentation and study, has announced a plan for the erection of a chain of floating airports, 400 miles apart, stretching across the Atlantic Ocean from New York to a point about 400 miles from Cherbourg, Plymouth and Queenstown.

Critics of the project are sceptical over the practicability of anchorages. “Is it economically or mechanically possible to anchor these platforms,” they ask, “where the ocean is miles instead of fathoms deep? And if so, how/are'you going to build cables light enough and strong enough to prevent them from breaking under their own weight plus a little unusual strain? What anchors are you going to put down that will hold in, a two or three-mile depth?” ( “Speaking definitely of my seadrome design,” Mr. Armstrong writes in a letter to'the New York “Times,” “permit me to state that the maximum draft of the structure, on sea duty is 150 feet, which is reached only by the ballast members. The greatest draft of the buoyancy tanks is 60 feet, which is but 20 feet more than that of the Leviathan. There are 32 buoyancy chambers, each with 12 watertight compartments, giving . a total buoyancy In excess of 35,000 tons. Suction Type Anchors

“The stations will be anchored, the anchoring cable reaching to the bottom of the ocean and holding the seadrome by means of a saucer-shaped (suction type) anchor, designed to be held solidly on the bottom of the ocean by tho column of water over it. You can readily appreciate that, at a depth of three miles, where the water pressure is 5,500 pounds a square inch,' the weight of water holding down a 12-foot diameter saucer-like disc in direct contact with the ocean bed /would be approximately 50,000 tons. ■.. ’ ' V

“You may recall that the task of lifting sunken submarines is made almost impossible because of the socalled suction effect which more correctly should be called the pressiire effect; it Is tho weight of the water column above it that is forcing it Into the bed of the ocean, and making it difficult to lift. This pressure is serious at 150 feet, which is about the maximum depth at* which submarine rescue work has been attempted.”

Naval men who have had the unpleasant experience of losing anchors in deep water are sceptical of this anchorage system. . Mr. Armstrong believes that they are unduly pessimistic. , Thousand of soundings, he. says, have been taken along the. projected route, so that the actual depth of the. water where anchorages are to be made is known to within a few feet. Bottom Is Red Clay 1

; "Samples of the bottom have been taken so that it is definitely known that nekrly all of the anchorages 'will be in red clay, a material exactly suited to. the special system devised to insure safe and permanent anchorage." , ... v .

Writing of differences ' between anchoring ships and seadromes the engineer says: “The first difference to

be noted is that seadromes are not subjected to the force of the waves except in a very minor degree, certainly less than 5 per cent, of that experienced' by a ship of similar displacement. Second, there is no heaving or pitching or rolling in waves which would develop the large impact forces, a ship experiences. Third, the anchor cable is not' directly supported by the seadrome as it is by a ship.

“In the seadrome anchoring system, contrary to the ship system, about the only stress on the anchor cable is that of its own weight while hanging in a catenary curve, which Is ample because of the arrangement used.” , ■ • Briefly this attachment consists of attaching the anchor cable itself to a lighted spar buoy, to which the seadrome is attached by a connecting cable, there being no direct connection between seadrome and the anchor cable. j /■; ; ', Route Markers and Stations ' By this spar buoy system of anchorage, according to the inventor, it would be feasible to release the seadrome and relieve the anchoring system of stress should wind and wave pressure go beyond safe operating limits. The inventor does nqt say what a transatlantic air liner 'would do approaching the spot where a seadrome ought to be for a landing only to find that it had slipped its cables and drifted away In a storm. However, with wireless equipment on both planes and Rations, Mr. Armstrong imagines ho great difficulty for planes to: know at all times the location of the seadromes. ,

_ In addition to the landing platforms, the propose system 1 Includes a line of anchored light buoys 50 miles apart so constructed as to serve as tie-up points as well as route markers, so that in the event of forced landings between a definite - t location can he maintained for rescue work.

“Improvements in radio control and the safety possible with multimotored planea may eventually make route buoys unnecessary,” Mr. Armstrong- says, “but their value for several years, covering the period of .preliminary operation and development, will, it is believed, many times offset their cost and maintenance.”

Besides ’ these 60-mile-apart route buoys,; Mjr. Armstrong proposes to erect Intermediate refuge stations half-way between , the seadromes, smaller but sufficiently large for a forced'landing, anchored by the same system but with a displacement of only GQO tonsi • V Mr. Armstrong has taken a leave of absence from his duties with the du Pont de Nemours Company of Wilmington. has formed his own development company, and is now trying to raise capital to construct a model seadrome; several hundred miles out at sea, a ; working, model which, if successful, he plans shall be the first ocean station in the chain.