Flight, April 23, 1910
THE HERRING-BURGESS BIPLANE.
HERRING, who was formerly associated with Curtiss in the construction of a biplane, has recently been working in conjunction with Messrs. Starling and Burgess in the production of a new type of machine that is mainly interesting for the manner in which it has been sought therein to obtain lateral stability without infringing the Wright system of control. An injunction was obtained by the Wrights against the Herring-Curtiss Co., it will be remembered.
In the Herring-Burgess biplane the principle adopted by Voisin, of using side-panels, has been introduced in modified form. Instead of turning the main-planes into a large box-kite by putting side panels between the struts, the panels are set like fins above the top deck. There are six such fins, each of triangular form, which stand up about three feet above the surface of the plane. The object of these fins is to resist the capsizing tendency by virtue of the air pressure acting on their surfaces when the machine slips sideways.
The Stability Fins.
The principal object of placing the fins above the upper deck has been to secure an ascentric disposition of the centre of pressure and the centre of gravity whereby the restoring couple is in the nature of a pendulum, the fins affording the necessary abutment on the air to enable the centre of gravity to swing back into place. The practical value of these fins remains to be proved, and especially will the effect of their position in respect to the centre of gravity be watched with interest. The necessity of forming a couple of some sort as a means of restoring lateral equilibrium is obvious, but this Herring-Burgess device is certainly rather a singular combination of dynamic and static forces.
On the part of the fins we have a potential force of the dynamic kind, that is to say, the value of the fins as an abutment strictly depends on their lateral motion through the air. Either the machine must slip sideways or the wind must blow upon the fins from the side, and only when this condition obtains can the fins offer the desired abutment that will enable the centre of gravity to swing back into its proper position relatively to the centre of supporting effect. The value of the weight of the machine as a factor in restoring equilibrium is, however, a fixed quantity for regarding the apparatus as a pendulum; in principle, the time of the oscillation is proportional to the square root of the length between the centre of gravity and the point of support. In practice, the point of support represented by the vertical fins has a lateral movement of its own in the same direction as the swing of the pendulum, and it would appear as if the actual time of recovery is likely to be a variable quantity owing to the difference in the actual lateral speed of the fins through the air under the changing conditions of wind and other fundamental factors. The question of oscillation past the normal position would seem to be another serious consideration in this system.
It is claimed that the fins will not offer much resistance to straight flight, and possibly the amount would be of no material importance if the machine always flew strictly in the eye of the relative wind. We cannot believe, however, that any fixed surface on a flying machine can have an actual neutrality to the relative wind for more than a small fraction of the whole duration of flight, and when a surface presents an angle of incidence the question of aerodynamic resistance must be considered, and may quite well become a factor of material importance, not only as a resistance but as a disturbing influence on normal stability.
It would appear, from the arrangement of the fins, that they could be constructed so as to fold up, but nothing of this sort has, so far as we are aware, been attempted, nor do we imagine that there would be much advantage to be gained by the complication.
Another point to which we should like to draw attention in connection with these fins, is the difference in their spacing apart. For constructional reasons they have been situated coincident with the main-spars, but we are rather inclined to think that the two central fins might have been omitted without a very serious loss in the effective value of the surface area. One of the most important series of experiments that has so far been conducted by Dr. T. E. Stanton at the National Physical Laboratory related to the shielding effect of one surface placed in front of another (see "Flight Manual," Note 15). It is, of course, true that the relative wind on the fins of the Herring-Burgess machine will always blow obliquely, owing to the forward velocity of flight on the part of the machine as a whole being compounded on the lateral slip, but for all that the question of interference should not be overlooked.
The general appearance of the machine is shown in the accompanying photograph, and the leading dimensions in the full-page drawing opposite. We have endeavoured to give reliable dimensions on the drawing, but the information is unfortunately not altogether corroborative from different sources. In the photograph, the machine is illustrated on the ice, and the arrangement of skids shown in the drawing is especially designed for work under these conditions.
It will be observed that there are some features of similarity between the Herring-Burgess machine and the Curtiss biplane illustrated in FLIGHT, Vol. I, p. 389, but the similarity hardly extends further than mere appearances. The Herring-Burgess biplane is rather a short span machine, and the aspect ratio of the planes is under 5. The decks are mounted on the frame with a much greater angle of incidence than they had in the Curtiss machine. It may also be observed that the engine is situated further back so as to avoid cutting a notch in the trailing edges to clear the propeller.
The control is effected by two levers and two pedals. The right and left-hand levers operate the steering rudder and the right-hand pedal controls the elevator. The left-hand pedal controls the engine throttle.