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You'll learn elec- tricity, including Radio, by DOING. No books to read. No tedious lectures. You stay with each step until you KNOW it. When you graduate, I guarantee that you'll know electricity. YOU are the sole judge of your fitness for a BIG JOB. Your tuition will be refunded if, upon graduation YOU are not satisfied. But ACT NOW. Big lUustrated 1?01?V7 Book Sent K MMltMLJ Take your first step to big pay TODAY. Mail the coupon for my big illustrated book on ELECTRICITY. Get my Free Railroad and New Low Tuition offers NOW. McSWEENY ELECTRICAL SCHOOL Dept. Cleveland, Ohio. H. McSwpenv, I*rcR. ■ I MrSwecnv Elrrtrif^at School, • I Drpt. R-6-12, Clrvrlaofl, Ohio. | I Dear Mac: Without obligation, nvntl mv your I t big, inlcrcBtlng book on KKKCTKICITY. AI»o | I Railroad Fare and Low Tuition OiT<erf>: and de> | tails ol Emplovmcnt Service. • I I I Name | 1 j I AddreM I I I Town SWIe ! I , 1 WHY SEAPLANES ARE SPEEDY (Continued from page ijy) We tried again and again. It had risen before with the same load, but now it wouldn't get out of the water. In the harbor, I was sitting dejectedly on a wing-stub with my hand dangling in the warm water when a hard little lump on the side of the hull came off in my fingers. I looked at it and the mystery was solved. The whole bottom of the hull was covered with barnacles and small mussels that had attached themselves during the month's delay. The increased water resistance of the rough hull, rather than the weight of the shellfish, prevented the take-off. When a diver cleaned off the bottom of the boat, the Dornier lifted easily from the water. In developing air-and- water craft, designers were dealing with two elements. Sometimes they would produce machines that flew like birds in the air, but on w'ater were tricky and dangerous. At other times the opposite would be true. I remember one treacherous machine the pilots nicknamed "The U-Boat." Every time it would near flying speed, the nose of the boat would be sucked down into the water and only by cutting the gun could the pilot avoid a "crash dive" to the bottom. Nobody knew what was wrong. The ship was one of the most beautiful I ever saw, its hull having smooth, curving lines. In the end, it was found that these lines caused all the trouble. The curve extended too far back. The bot- tom of the boat was like the top of an air- plane w-ing. As speed increased, the water produced a down-suction just as the partial vacuum above a wing increases its upward lift. AVOTHER design difficulty in early water . planes concerned the necessity for put- ting the propeller high up to avoid the spray. When a pilot opened the throttle on these machines, the nose of the plane pointed down, and when he shut off the motor, it pointed up. This meant that if the engine cut out unex- pectedly in the air, the ship was likely to pull up into a danccrous stall unless the man at the slick did some hair-trigger piloting. Being high above the center of weight, the push of the propeller tended to drive the top of the plane ahead before the bottom, thus nosing the ship down. . d when the propeller's push was suddenly removed, the nose naturally came up. On the latest boats the motor is mounted so it slants downward to the rear. This sends the slipstream, or wake, of the propeller down on the tail surfaces, holding the tail down and the nose up when the motor is runnine, and letting the tail rise and the nose go down when the blast from the propeller ceases. Another recent improvement for seaplanes has been announced by the makers of Edo floats. Water rudders, that help in guidinc a ship on the water, have been designed for attaching to the rear of the pontoons. The danger of slewing violently at high speed when landing with the rudders turned to one side has been eliminated in an ingenious man- ner. The steering surfaces are hinged so the pressure of the water at speeds over twenty- five miles an hour flips them up out of the way. THE latest innovation in flying boat con- struction is reported by the Savoia- Marchctti factory at Port Washington, N. Y. A ship with a hull and framework made entirely of spot-welded stainless steel is near- ing completion. It is expected to be both lighter and stronger than the usual wood or duralumin construction. Under ordinary conditions, landing a water craft is far easier than bringing down a land plane. But on days when a light haze hangs over a river or lake it is almost impossible to tell where the air ends and the water begins. A few weeks ago, I was flying down the Hudson River in a Loening amphibian. Near Peekskill, where I was to land, an early morning mist lay over the river. The beginner pilot who was with me wanted to make the landing for practice. So I let him go ahead. He throttled down the engine and w'ent into his glide. He had just begun to level off when — crash I we struck the water. Even an old-timer often misjudges the position of the water when coming down in a light haze. The best plan is to glide to within forty feet of where you think the water is and then switch on the motor. Keeping the plane running just above stalling speed, you can fly it onto the water in a long gradual descent that avoids the risk of '•pancaking" or bouncing. SOOX after flying boats appeared, an inventor produced a device to warn pilots when they approached the water. A weighted wire hung over the bow of the boat. When it struck the water, a light on the instrument panel flashed on. The apparatus worked suc- cessfully, but it was needed so infrequently that there was little demand for it. When the water is perfectly flat, without a ripple, it is also difficult to judge your height above the surface. I carry torn-up bits of paper in my pocket for such emergencies. By tossing them overboard, I can see them floating on the water and can judge where to level off. Once, on a still morning over Lake Constance, Germany, I used leaves drifting on the dead flat water as a guide in coming down. On another occasion, I landed a big flying boat at the mouth of the Loire River, France, by moonlight late at night. Ripples on the water reflecting the moonbeams showed me clearly where the surface lay. Of course, flying seaplanes in a calm is one thing, and piloting them from rough water is another. The latter Ls the real test of a flyer's skill. Rough water is of two kinds, swells and waves. The worst of all combinations is waves on top of swells. Off the coast of Spain, in the Bay of Biscay, I once had to take off from a sea in which the .sw-ells were like a series of parallel moun- tains. The danger is that the ship will reach the crest of a swell with almost flying speed. Then it will hop off like a glider and sail down, crashing into the side of the nert advancing wall of water. HOVV'EV'ER, a seaplane pilot does not have to take off and land facing the wind as does a flyer at an airport. Usually, in heavy swells, the boat pilot takes off cross wind, running parallel to the waves, and lands the same way. In rough weather, a pilot is likely to be too anxious to get his plane into the air. If he stalls the ship off the water, it will nose down and begin "porpoising" along in jumps, crashing onto the water at the end of each hop. The instant a ship begins to porpoise, I cut the gun. The chances of crashing are too great. After my transatlantic attempt ended in a thrilling midnight landing with a flaming engine, 600 miles from shore (P.S3I., Nov. '31, p. 36), nearly a hundred inventors from all over the world wrote me letters. They had devi.sed flying boats with wings that could be dropped off in a forced landing at sea so the hull could cruise off like a motor- boat. This illustrates one of the common miscon- ceptions about (Continued on paze i.^o) POPULAR SCIENCE MONTHLY
