Mo-Bipe (oz15388)


Mo-Bipe (oz15388) by Harry Higley 1973 - plan thumbnail

About this Plan

Mo-Bipe. Control line Profile Navy Carrier model.

Quote: "Requirements for Profile Carrier allow non-scale designs. A biplane can offer several advantages such as reduced weight and frontal area. Mo-Bipe, by Don Gerber and Harry Higley.

During the 1920s Martin made the MO-1 monoplane which was used as the subject for both a Class I and Class II Navy Carrier ship. The Class I version Martin MO-1 (oz9283) appeared in the August 1969 issue of American Aircraft Modeler. The subject of this article was designed for the Profile Navy Carrier event, and its name was not chosen because Martin made a biplane variant of the MO-1, they didn't. It was chosen because the Bipe retains many of the construction features and the same general appearance of the MO-1.

In an era when the Scale Navy Carrier events were dominated by Guardians, the MO-I was a most unlikely but highly successful choice for the event. The real airplane was to be a battleship based observation plane in the early 1920s. Only two ever saw Carrier service; an old letter reveals they were not regarded as fit for this service by the Navy. The MO-Bipe may appear an unlikely choice for Profile Carrier, but for a different reason. Most fliers do not normally think of a biplane for a Speed event.

Due to the nature of the rules, the biplane configuration, however unlikely it may seem, offers the very decided advantage of reduced weight and frontal area. A monoplane with a 36-in span would require about an 8.5 in chord to achieve the 300 sq in required by the rules. A few airfoil sketches will show that the minimum thickness that will maintain the structural integrity of a built-up wing is about .75 in. This gives a frontal area of about 27 sq in. A wing this large does not lend itself well to solid construction.

The MO-Bipe used two solid, easy to shape wings with a 28 in span, 5.7 in chord and .25 in thickness. These give a total frontal area of about 27 sq in, or only slightly more than half that of the monoplane. The Bipe will also have a shorter fuselage because of the reduced wing chord. This 15 to 25 percent overall reduction in fuselage dimensions will provide a substantial weight reduction.

One last advantage for the biplane is the capability of using full span strip ailerons on the lower wing which eliminates the need for tip weight, thus saving another ounce. Strip ailerons are easier to install than conventionally placed ailerons, as there is no need for long torque rods or clumsy pushrods. The importance of the working ailerons and rudder cannot be over-emphasized. This plane was designed from the ground up for Profile Carrier, but the full potential of the design cannot be realized unless the moveable ailerons and rudder are used.

Unusual construction features shared by the MO-1 and MO-Bipe include solid wings and easy to install semi-enclosed controls. Another common feature is variable sweep line leadouts. The less the lines sweep back, the faster the plane will go. However, the plane will be more likely to come in. By trying different holes in the tip guide, the most favorable line sweep may be found. Full credit for the design belongs to Don Gerber. Don and I correspond regularly and this spring he sent some photos of the MO-Bipe and asked if 1 would be interested in a joint article, as he did not want to devote the large block of time that assembling an article such as this requires.

Construction: The construction procedure was planned to avoid two problems, First, a completely assembled biplane is difficult to finish due to the limited space between the two wings. Second, painting after the controls are installed at best will look bad because of partially painted rods and other components; worse yet, the paint may foul the whole system. The strategy employed is to assemble the plane minus the upper wing and struts. The controls are then temporarily installed, checked, adjusted and then removed prior to finishing. The main frame, control surfaces, struts and upper wing are finished separately, and then the whole model is permanently assembled.

To begin with, cut all plywood parts. These include the bellcrank, hook and tail skid mounts, the struts and the plywood fuselage doublers. The doublers should be cut a little oversize as they may not end up in exactly the position they should. The resulting slight overhang is easily trimmed and sanded flush with the fuselage. Drill the required holes in the bellcrank mount, inboard strut, and tail skid mount.

Now is as good a time as any to bend the landing gear, tail skid and hook. Attach the wheels with soldered washers. Attach the tail skid to its mount with No.6 x 3/8 sheet metal screws. This will facilitate easy removal of the skid for painting and replacement, though the latter will probably never be necessary.

The bellcrank on the J Roberts unit must be shortened. Notice on this control unit that there are, in addition to the holes provided for the leadouts, two dents indicating alternate leadout positions. Drill at these points, then trim the excess from the bellcrank. Attach the leadout wires..."

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Mo-Bipe (oz15388) by Harry Higley 1973 - model pic

  • (oz15388)
    by Harry Higley
    from American Aircraft Modeler
    January 1973 
    28in span
    IC C/L Biplane
    clean :)
    all formers complete :)
    got article :)
  • Submitted: 15/06/2024
    Filesize: 536KB
    Format: • PDFbitmap
    Credit*: theshadow
    Downloads: 121

Mo-Bipe (oz15388) by Harry Higley 1973 - pic 003.jpg

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