Flight, January 1922
THE MUMMERT "BABY VAMP" SPORTPLANE
IN our issue for July 28 last, brief mention was made of a small machine - which was erroneously referred to as the "Maumert" instead of "Mummert" - tested by Bert Acosta, and we now give illustrations
and some further particulars, for which we are indebted to our American contemporary Aerial Age, of this interesting little machine. It is of interest to note that on the same day as Bert Acosta tested the "Baby," he tried out the Remington-Burnelli 30-passenger 'bus - described in FLIGHT for July 28; and one of the accompanying illustrations showing these two machines together forms an amusing comparison.
On the first test of the "Baby" the pilot held the machine on the ground for an initial run of about 200 ft. before taking off, but as soon as the machine got into the air it was observed to be flying very steadily at a speed even greater than its theoretical performances indicated - 90 m.p.h. - estimated by observers on the ground at about 100 m.p.h. Later Acosta made an "Immelmann," which manoeuvre, as well as many others, the little machine performed in fine style. After fifteen minutes of flying, during which an altitude of 1,500 ft. was reached, the pilot made a perfect landing, and reported very favourably on the machine's behaviour. He stated that it had "absolutely no 'tricks,' and needed very few minor adjustments," but, as to be expected with machines fitted with two-cylinder opposed engines, there was a certain amount of vibration, though this was by no means excessive.
Many new features of design and construction are to be found in various parts of the "Baby," and, apart from its extremely diminutive proportions, perhaps the most striking feature is the extensive use of veneer. This is used for the entire fuselage, and for covering the main planes and tail surfaces. Besides adding to the rigidity of the wing construction, this employment of veneer enables the correct shape of the wing section (R.A.F. 15) to be maintained at all times, thereby allowing the full value of this section to be obtained. The "Clark Truss" is used for the interplane bracing system. The principal characteristic of this truss consists in the elimination of the usual set of bracing cables between upper and lower rear spars and incidence and drift cables. To replace these there is but a pair of stream-line wires running from the fuselage at the lower front spar attachment to the upper rear spar at the point of attachment of the interplane strut. These wires constitute the flying wires, and also act as drift wires. There is but a single landing wire (stream-line) on each side of the fuselage running from the lower end of the front interplane strut to the top of the rear fuselage-strut. The interplane struts are of stream-line steel tube, of N-formation, and two single struts support the top plane at the centre above the fuselage, into which they are built and form a part thereof.
The top plane is built in one continuous panel, with a cutout portion at the trailing edge above the pilot's cockpit. The lower plane is also in one piece, and is mounted below the fuselage. The wings are built up with a total of 9 spars, not including the leading and trailing edges, which are of rectangular section 1/4-in. wide and varying in depth according to their location in the wing. The upper rear main spar and the lower front main spar are of the box type. Mahogany veneer, 1/16-in. thick, tacked to all the spars and edges is employed for the entire wing covering. Ailerons are fitted to the lower plane only, and these extend from wing tip to fuselage, where they are directly connected to the control stick. They are set into the wings on steel tubes, which leave no gap between the surfaces; and as the inner ends are operated by a small lever inside the fuselage, there are no external fittings to offer resistance.
The fuselage is of the monocoque type, built to stream-line shape on a specially constructed form. The veneer is wrapped spirally and reinforced internally by means of light hoops. At the stern the fin - which is in upper and lower sections - is built into the fuselage. The lower part of the fin carries the tail skid. Stick and rudder-bar control of the usual type is fitted, but the rudder is operated by cables enclosed in the fuselage and connected to projections in continuation of the fuselage stream-line; these projections fit into the stem after the fashion of a socket and are "airtight."
A dashboard in front of the pilot carries the usual instruments, and the pilot's seat is of the bucket type, formed from a continuous strip of aluminium. A V-type landing chassis is fitted, the V's being of stream-line dash. The wheels are attached with the usual shock-absorber sprung axle.
The engine is an air-cooled twin cylinder opposed Lawrence, developing 25 h.p. at 1,800 r.p.m. Provision is made for carrying 12 gallons of petrol and two gallons of oil.
Mr. H. C. Mummert, the designer of the "Baby," is associated with the engineering department of the Curtiss Company's Garden City plant.
The principal characteristics of the "Baby" are :-
Span 18 ft.
Chord 2 ft. 7 5/8 ins.
Gap 2 ft. 9 ins.
Area of main planes (total) 90 sq. ft.
Area of tail plane 5 sq. ft.
Area of elevators 4 sq. ft.
Area of rudder 3 sq. ft.
Area of fins. 3 sq. ft.
Weight (empty) 350 lb.
Weight (fully loaded) 590 lb.
Weight/sq. ft 6-5 lb.
Weight/h.p. 23-6 lb.
Speed range (estimated) 43-90 m.p.h.