Sperry Messenger (oz7745)


Sperry Messenger (oz7745) by R Jess Krieser 1968 - plan thumbnail

About this Plan

Sperry Messenger. Radio control scale model biplane. Super Tigre 46 R/C engine shown.

Sperry Messenger by Jess Krieser, March 1968 AAM.

Quote: "THIS interesting little biplane is ideally suited for home-building. It's small, with a wingspan of only 20 ft. It had only 56.5 hp. And it featured simple, mostly wood construction that probably would not require special skills or special tools to complete. It was fully aerobatic, and was stressed to a load factor of six.

The fuselage was a simple box, made with square, wood longerons and up-rights, with a few semi-circular formers on the turtledeck, and around the nose. The entire structure was covered with 1/8 plywood. Tail surfaces were simple, wood frames, with steel tubing edges. Wing construction was mostly wood, with bandsawed ribs fitted with wide, slotted capstrips. Spars were wood, routed out for lightness. Tips were square, and the wire trailing edge pulled in to give a scalloped appearance when the dope tightened the fabric.

Aileron cables were in the lower wing. Ailerons on the upper wing were actu-ated by the lower ones through inter-connecting struts. We've followed this set-up somewhat in our model, as the aileron servo is in the bottom wing for convenience, and wire pushrods connect the lower ailerons to the upper ones, with Kwik-Links to provide final trim adjustments.

Although it bears the name of Lawrence Sperry, the Sperry Messenger was actually designed by Alfred Verville, of the US Army Air Service Eng Div, Dayton, Ohio. Its origin dates back to the three-year period following World War I. It was through the successful bidding of Lawrence Sperry that the
Messenger acquired his name, as the initial contract to build the Messengers was granted to the Lawrence Sperry Aircraft Co, of Farmingdale, Long Island, in April of 1920.

It was in a Messenger that Lawrence Sperry made his famous landing on the plaza in front of the Capitol Building in Washington, D.C., and climbed part way up the Capitol steps as his tail skid didn't bite into the concrete to arrest the ship on roll-out, and he had no wheel brakes.

A novel three-cylinder engine powered the Messenger. Of air-cooled radial design, and equipped with dual battery ignition, it turned out 56.5 hp at 1,600 rpm, and 64 hp at 1,880 rpm. This gave the diminutive biplane a top speed of 96.7 mph at sea level, with a minimum speed of 45 mph. With only 150 square feet of wing area, and a wing loading of only 5.7 lb per square foot, it climbed 700 feet per minute on this small amount of power.

When Verville first designed the Messenger, there was no official system for designating Army airplanes, so it simply was called the 'Messenger,' and given Sperry's name to designate the manufacturer. This label stuck. When the Army designating system was revised in May, 1924, it continued to be called the "Sperry Messenger." However, the official designation after that date was M-1 for the first 22 built, and M-1A for the re-maining 20 ships.

The ship was doped in the then-standard color of khaki-brown all over; with red, white, and blue stars on the wing; and red, white, and blue vertical bars on the rudder. For those wanting more details and background on this aircraft, an excellent two-part article by Pete Bowers appeared in American Modeler in May and June, 1962.

There have been absolutely no departures from scale except for our choice of a semi-symmetrical airfoil, to improve performance, and omission of the scallops on the trailing edge of the wings. Even the landing gear is to scale, with working rubber shock cords. However, the Williams wheels are slightly out of scale on their diameter, and your wheels will either be slightly larger, or slightly smaller - depending on which of the two sizes you use.

Flying the Messenger will be a real ball; you can make this ship perform like a flying scale or like a hot competition multi, depending on the power you use. The original, shown in the photos, was built by Evan Roberts, and was powered by the new Enya .45. This engine is quite powerful for its size, and with a 11 x 6 Tornado nylon prop, and Idle-X fuel, it turned up 11,400 rpm right out of the box, with no break-in, which results in the Messenger rolling the entire distance of 7 to 8 ft on take-off, after which it climbs out at 45 to 50 degrees at full power. With the Enya continuing at full throttle, it flies like a jet. Rolls, with ailerons on both wings working, are like corkscrews. But with Enya throttled back to about half power, it tames down into a relatively easy-flying airplane with more scale-like speeds. At half-power, it still does beautiful rolls. Actually, any good .35 would be very adequate power for this ship, and the OS Max S-35 would be an ideal choice.

Wings: Rib-spacing is scale. In order to preserve the scale appearance of the fabric covered wings, I have kept sheeting on the wings to a minimum consistent with ruggedness. I felt that this called for spruce spars.

Start the wings by building both front and rear spars for both wings, joining the separate pieces at the proper dihedral angles with the spruce doublers, and ce-menting them with either white glue or epoxy. While these are drying, you can make a building jig for the wings out of a few pieces of Celotex, Homasote, or similar material. Cut a piece to the proper width for the center section, and tack this down to a building board. You can attach pieces to either side of this, angling them upward..."

Update 27/05/2016: article pages, text & pics added, thanks to RFJ.

Supplementary file notes

Article pages, text & pics.


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Sperry Messenger (oz7745) by R Jess Krieser 1968 - model pic


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