A Graphical Method for Interpolation of Specific Flying Boats from Collapsed Results of General Tests of Flying-boat-hull Models
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Locke, F W S↗
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The Calculated Effect of Various Hydrodynamic and Aerodynamic Factors on the Take-Off of a Large Flying Boat
Present designs for large flying boats are characterized by high wing loading, high aspect ratio, and low parasite drag. The high wing loading results in the universal use of flaps for reducing the takeoff and landing speeds. These factors have an effect on takeoff performance and influence to a certain extent the design of the hull. An investigation was made of the influence of various factors and design parameters on the takeoff performance of a hypothetical large flying boat by means of takeoff calculations. The parameters varied in the calculations were size of hull (load coefficient), wing setting, trim, deflection of flap, wing loading, aspect ratio, and parasite drag. The takeoff times and distances were calculated to the stalling speeds and the performance above these speeds was studied separately to determine piloting technique for optimum takeoff. The advantage of quick deflection of the flap at high water speeds is shown.
Olson, R.E.↗
Hydrodynamic Properties of Planing Surfaces and Flying Boats
The study of the hydrodynamic properties of planing bottom of flying boats and seaplane floats is at the present time based exclusively on the curves of towing tests conducted in tanks. In order to provide a rational basis for the test procedure in tanks and practical design data, a theoretical study must be made of the flow at the step and relations derived that show not only qualitatively but quantitatively the inter-relations of the various factors involved. The general solution of the problem of the development of hydrodynamic forces during the motion of the seaplane float or flying boat is very difficult for it is necessary to give a three-dimensional solution, which does not always permit reducing the analysis to the form of workable computation formulas. On the other had, the problem is complicated by the fact that the object of the analysis is concerned with two fluid mediums, namely, air and water, which have a surface of density discontinuity between them. The theoretical and experimental investigations on the hydrodynamics of a ship cannot be completely carried over to the design of floats and flying-boat hulls, because of the difference in the shape of the contour lines of the bodies, and, because of the entirely different flow conditions from the hydrodynamic viewpoint.
Sokolov, N. A.↗
Tank Investigation of a Powered Dynamic Model of a Large Long-Range Flying Boat
Principles for designing the optimum hull for a large long-range flying boat to meet the requirements of seaworthiness, minimum drag, and ability to take off and land at all operational gross loads were incorporated in a 1/12-size powered dynamic model of a four-engine transport flying boat having a design gross load of 165,000 pounds. These design principles included the selection of a moderate beam loading, ample forebody length, sufficient depth of step, and close adherence to the form of a streamline body. The aerodynamic and hydrodynamic characteristics of the model were investigated in Langley tank no. 1. Tests were made to determine the minimum allowable depth of step for adequate landing stability, the suitability of the fore-and-aft location of the step, the take-off performance, the spray characteristics, and the effects of simple spray-control devices. The application of the design criterions used and test results should be useful in the preliminary design of similar large flying boats.
Parkinson, John B↗
Landing Characteristics in Waves of Three Dynamic Models of Flying Boats
Powered models of three different flying boats were landed in oncoming wave of various heights and lengths. The resulting motions and acceleration were recorded to survey the effects of varying the trim at landing, the deceleration after landing, and the size of the waves. One of the models had an unusually long afterbody. The data for landing with normal rates of deceleration indicated that the most severe motions and accelerations were likely to occur at some period of the landing run subsequent to the initial impact. Landings made at abnormally low trims led to unusually severe bounces during the runout. The least severe landing occurred after a small lending when the model was rapidly decelerated at about 0.4 g in a simulation of the proposed use of braking devices. The severity of the landings increased with wave height and was at a maximum when the wave length was of the order of from one and one-half to twice the over-all length of the model. The models with afterbodies of moderate length frequently bounced clear of the water into a stalled attitude at speeds below flying speed. The model with the long afterbody had less tendency to bounce from the waves and consequently showed less severe accelerations during the landing run than the models with moderate lengths of afterbody.
Benson, James M.↗
Landing characteristics in waves of three dynamic models of flying boats
Powered models of three different flying boats were landed in oncoming waves of various heights and lengths. The effects of varying the trim at landing, the deceleration after landing, and the size of the waves were determined. Data are presented on the motions and accelerations obtained during landings in rough water.
LOADS, LANDING - IMPACT, WATER↗
Correlation of the Trim Limits of Stability Obtained for a PB2Y-3 Flying Boat and a 1/8-Size Powered Dynamic Model
Tests of a PB2Y-3 flying boat were made at the U.S> Naval Air Station, Patuxent River, Md., to determine its hydrodynamic trim limits of stability. Corresponding tests were also made of a 1/8-size powered dynamic model of the same flying boat in Langley tank no. 1. During the tank tests, the full-size testing procedure was reproduced as closely as possible in order to obtain data for a direct correlation of the results. As a nominal gross load of 66,000 pounds, the lower trim limits of the full-size and model were in good agreement above a speed of 80 feet per second. As the speed decreased below 80 feet per second, the difference between the model trim limits and full-scale trim limits gradually became larger. The upper trim limit of the model with flaps deflected 0 deg was higher than that of the full-size, but the difference was small over the speed range compared. At flap deflections greater than 0 deg, it was not possible to trim either the model of the airplane to the upper limit with the center of gravity at 28 percent of the mean aerodynamic chord. The decrease in the lower trim limits with increase in flap deflection showed good agreement for the airplane and model. The lower trim limits obtained at different gross loads for the full-size airplane were reduced to approximately a single curve by plotting trim against the square root of C(sub delta (sub o)) divided by C(sub V).
Garrison, Charlie C.↗
Tank tests of a model of a flying-boat hull with a fluted bottom
A 1/5-scale model of a flying-boat hull having flutes in the bottom both forward and aft of the step (NACA model 19) was tested to determine its water performance. The model was also tested after the successive removal of the flutes on the afterbody and forebody. The results from these tests are compared with those from tests of a model of the hull of the Navy PN-8 flying boat and it is concluded that the fluted-bottom model and its modifications are inferior to the model of the PN-8.
Dawson, John R↗
Complete tank tests of two flying-boat hulls with pointed steps - N.A.C.A. Models 22-A and 35
This note presents the results of complete tank test of N.A.C.A. Models 22-A and 35, two flying-boat hulls of the deep pointed-step type with low dead rise. Model 22-A is a form derived by modification of Model 22, the test results of which are given in N.A.C.A. Technical Note No. 488. Model 35 is a form of the same type but has a higher length-beam ratio than either Model 22 or 22-A. Take-off examples are worked out using data from these tests and a previous test of a conventional model applied to an arbitrary set of design specifications for a 15,000-pound flying boat. The comparison of these examples shows both pointed-step models to be superior to the conventional form, and Model 35 to be the better of the two. Model 35 is applied to a hypothetical 100,000-pound flying boat of the twin-hull type and performance calculations are made both for take-off and range. The results indicate that the high performance of this type of hull will enable the designer to use higher wing and power loadings than are found in current practice, with a resulting increase in range and pay load.
Shoemaker, James M↗
Hydrodynamic Tests in the N.A.C.A. Tank of a Model of the Hull of the Short Calcutta Flying Boat
The hydrodynamic characteristics of a model of the hull of the Short Calcutta (N.A.C.A. Model 47) are presented in non-dimensional form. This model represents one of a series of hulls of successful foreign and domestic flying boats the characteristics of which are being obtained under similar test conditions in the N.A.C.A. tank. The take-off distance and time for a flying boat having the hull of the Calcutta are compared at two values of the gross load with the corresponding distances and times for the same flying boat having hulls of two representative American types, the Sikorsky S-40 and the N.A.C.A. 11-A. This comparison indicates that for hulls of the widely different forms compared, the differences in take-off time and distance are negligible.
Ward, Kenneth E↗
Methods Used in the NACA Tank for the Investigation of the Longitudinal-Stability Characteristics of Models of Flying Boats
Report presents the results of tests of longitudinal stability characteristics of models of several flying boats conducted in the NACA Tank No. 1. These investigations were made for the purpose of (1) determining suitable methods for evaluating the stability characteristics of models of flying boats, and (2) determining the design parameters which have an important effect on the porpoising. This report is mainly concerned with the construction of suitable models, the apparatus, and methods used in the tests. The effect of changes in some design parameters is discussed.
Olson, Roland E↗
A collection of the collapsed results of general tank tests of miscellaneous flying-boat-hull models
Presented here are the summary charts of the collapsed results of general tank tests of about 100 flying boat hull models. These summary charts are intended to be used as an engineering tool to enable a flying boat designer to grasp more quickly the significance of various hull form parameters as they influence his particular airplane. The form in which the charts are prepared is discussed in some detail in order to make them clearer to the designer. This is a data report, and no attempt has been made to produce conclusions or correlations of the usual sort. However, some generalizations are put forward on the various methods in which summary charts may be used.
Locke, F W S , Jr↗
A discussion of certain problems connected with the design of hulls of flying boats and the use of general test data
Report presents the results of a survey of problems encountered in applying general test data to the design of flying-boat hulls. It is shown how basic design features may be readily determined from special plots of test data. A study of the effect of the size of a flying boat on the probable limits to be covered by the general test data is included and recommendations for special tests and new methods of presenting test data for direct use in design are given.
Diehl, Walter S↗
The design of the optimum hull for a large long-range flying boat
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FLYING BOATS, GIANT↗
Tank Tests of NACA Model 40 Series of Hulls for Small Flying Boats and Amphibians
The NACA model 40 series of flying-boat hull models consists of 2 forebodies and 3 afterbodies combined to provide several forms suitable for use in small marine aircraft. One forebody is the usual form with hollow bow sections and the other has a bottom surface that is completely developable from bow to step. The afterbodies include a short pointed afterbody with an extension for the tail surfaces, a long afterbody similar to that of a seaplane float but long enough to carry the tail surfaces, and a third obtained by fitting a second step in the latter afterbody. The various combinations were tested in the NACA Tank by the general method over a suitable range of loadings. Fixed-trim tests were made for all speeds likely to be used and free-to-trim tests were made at low speeds to slightly beyond the hump speed. The characteristics of the hulls at best trim angles have been deduced from the data of the tests at fixed trim angles and are given in the form of nondimensional coefficients applicable to any size hull.
Parkinson, John B↗
A Complete Tank Test of a Model of Flying-boat Hull - N.A.C.A. Model 16
A model of a 2-step flying-boat hull, of the type generally used in England, was tested according to the complete method described in the N.A.C.A. Technical Note No. 464. The lines of this model were taken from offsets given by Mr. William Munro in Flight, May 29, 1931. The data cover the range of loads, speeds, and trim angles that may be of use in applying the hull form to the design of any seaplane. The results are reduced to nondimensional form to aid application to design problems and facilitate comparison with the performance of other hulls. The water characteristics of Model 16 are compared with those of Model 11-A, which is representative of current American practice. The results show that when the two forms are applied to a given seaplane design under optimum conditions for each, the performance of Model 16 will be somewhat inferior to that of Model 11-A.
Shoemaker, James H↗
A Comparison of the Results from General Tank Tests of 1/6- and 1/12-full-size Models of the British Singapore IIC Flying Boat
A 1/6-full-size model of the hull of the British Singapore IIC flying boat was tested in the NACA tank. The results are given in the form of charts and are compared with the results of previous tests made in the NACA tank of a 1/12-full-size model, published in NACA T.N. No. 580, and with the results of tests made in the British R.A.E. tank of another 1/6-full-size model of the same hull. When the data from the tests of the 1/6- and 1/12-full-size models were compared on the basis of Froude's law of comparison, differences were found. This fact supported the belief that the small scale of the model and the use of a model that was too small to suit the equipment of the NACA tank had caused the results of the tests of the 1/12-full-size model to be less reliable than the results of the tests of the 1/6-full-size model. The results of the tests of the two models agreed sufficiently well to show that test of a small model, if made meticulously and with suitable equipment, may give useable results, but that a larger model should be used whenever feasible. The results of the NACA tests of the 1/6-full-size model were found to be in good agreement with the R.A.E. tests of a model of the same size.
Truscott, Starr↗
The estimation of maximum load capacity of seaplanes and flying boats
This reports presents a method of calculating time and gross load for take-off of seaplanes and flying boats.
Diehl, Walter S↗