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Aviation History
1913
1913 - 0476.PDF
(/jJGHT when the machine finally quits the water. Builders of hydro aeroplanes scarcely seem to have paid sufficient attention to this last-named agency or force. There is, nevertheless, one particular form in which this force can be employed in a very efficient manner, both in the water (as was shown by Forlanini, and also by Lieuts. A. Crocco and O. Kicaldoni) and in the air as shown by 1'hilipps. [See FLIGHT, January 25th, 1913, page 98.] With such an apparatus as this Forlanini was able to support a weight of 3-6 lbs. per 1-6 sq. ft. at 45 rn.p.h. AbJ to TABLE Main floats and method of adjustable attach' ment on the Bragg-Smith hydro-aeroplane. Front float—method of adjust able attachment and divided elevator on the Bragg-Smlth hydro-aeroplane. In the case of the Crocco-Ricaldoni experiments, the hull left the water entirely at 15 m.p.h., and a speed of 43 "5 m.p.h. was obtained with a motor of So h.p., the wtight carried being at the rate of 3-i lbs. per 1*6 sq. ft. Much better results than have so far been obtained with flat- bottomed floats, stepped or unstepped. One must not forget that Fleming-Williams used a cigar-shaped body with a rear fin more than 18 months ago, and that this model was the first model to actually leave the surface of the water. further experiments are much needed with the Forlanini and Crocco-Ricaldoni type of float. Fabre we know tried it and gave it up, because he picked up undesirable objects from the French harbours, some of which have plenty of such, but that is no reason for giving up SUCh a type. The hydrovanes would undoubtedly have to be extremely strong, and their angle of incidence in my opinion should be capable of alteration by means of a lever worked from the pilot's seat. I believe myself that it is this type of float, combined with a body or bodies of streamline form, which is likely to be the type which will be found most suitable for waves and rough water. Flotational Stability. One of the most difficult problems is the question of flotational stability, and stability when in actual flight, combined with success ful rising or alighting should the machine be caught by anything in the nature of a side gust. The former requires the setting apart of the floats as far as possible, the latter the nearer the better, more especially in a lateral sense. The better solution that I have to offer is twin floats of the catamaran type, whose flotational (lateral) base is from one-quarter to one-third the total span of the main plane, combined with wing tip balancers (made as light as possible), and clear of the water, to come into play only if the machine rolls; in the case of full-sized machines these could best be constructed of stout canvas or some such material—blown out —i.e., under pressure. I see no reason why during flight these could not be deflated, and therefore their resistance lessened. They should also be so fixed to the planes that they could be raised or lowered at least 3 ft. at the will of the pilot. In the case of models, i.e., light models under, say, a pound in weight, since it is mo>t important to keep the moment of inertia of the machine about its three principal axes as small as possible, especially the one about the longitudinal axis, I think this is a case in which blown-out rubber tubing could be used with advantage. I have here a balancer-float made of veneer wood with cork ends, but I find it far too heavy. The instability of most model hydroaero planes is generally due to the fact that they have too large moments MAY 3, I9i> of inertia ; every endeavour should be made to keep these to a minimum. Catamaran floats should be stepped for several reasons —less friction, i.e., resistance, &c, and because they enable the machine to take its proper attitude when on the point of flying, a matter otherwise difficult of attainment, especially if the machine be a tractor and the floats long, as they must be for rough water. Conditions the Floats Should Fulfil. The conditions which the floats should fulfil are :— (1) A flotational capacity sufficient to safely float the machine on the water when at rest, in rough weather as well as calm. (2) A form or shape to permit of as quick a get-off from the water as possible. (3) Minimum water and air resistance. The former to include the ability or capacity to cut through a wave when necessary. (4) Minimum weight and maximum strength. (5) Absolute watertightness. (6) Support (if possible) at least their own weight in the air, i.e., not to be altogether inefficient in an aerodynamic sense, but the hydrodynamic value to have precedence. (7) A capacity to withstand severe shocks from waves or a collision with the ordinary floating matter of the water on which they may be travelling and if possible an enforced descent on land. (8) No tendency to dive. In the case of mode's, all the above conditions (save the last) have been fulfilled. Landing, This last concerns the " alighting " of the machine on the water after a flight, and is the last item with which I propose to deal. It is at this point or juncture that the model and the full-sized machine that have, practically speaking, so far journeyed with us together hand in hand part company. How should a machine alight on the water ? Evidently in exactly the same manner in which it arose from it, but in the reverse order. Now a model cannot do this because it carries no pilot to " flatten out" at the right moment! It would appear, therefore, better to investigate this part of the problem separately by means of (heavy) models launched first at a fine angle of incidence, gradually increased. With these remarks I now leave the matter to others—to either substantiate or criticise the views I have put forward, or to state other and very possibly much better views of their own. (To be continued.) Rear float and attachment on the Whitworth hydro aeroplane (Olyinpia model). Replies in Brief. A. A. COLLINS ; G. ENGLEFIELD ; P. W. PEEL ; A. B. COOK ; S. T. SMITH ; L. MINOT ; P. H. WILKINSON.—Many thanks for your communications, which we shall be pleased to make use of in due course. LIVERPOOL A.—Thanks very much for the float you sent us, but it is quite out of date here—far too heavy, and not of the best section ; it is also very easily indented and very apt to leak. " K. MORRIS (Australia).—You will find your query fully H. 498 answered in the recent April 5th and 12th issues.
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