Modified Galloping John (oz13008)

About this Plan

Modified Galloping John. Radio control sport biplane model.

The Galloping John (oz2882) by Bill Northrop was a single channel design, first published in MAN August, 1965. This here is a later modified version from 1975, for 4 channels.

Quote: "Mods To A Galloping John, by Dennis Cain. Well known biplane of early 60s updated for more power, full house operation, increased performance. Back in its wiggly days it still put out, and now with modifications it's even better!

Normally my modeling activity is limited to building from tried and proven plans and an occasional kit that is of special interest. However, once in a while the urge to do something a little different strikes me. I am not talented enough to create my own designs, and perhaps too lazy, so I dig through my stack of plans looking for something to modify. The Galloping John (oz2882) by Bill Northrop (from MAN August, 1965) was my latest victim. The result is the basis for this article.

Having had a preference for biplanes since building the Bristol Bullet (oz12526) by Hale Wallace I now give careful consideration to all biplane plans that happen to be available. This results in my building quite a few of them, which in turn makes my balsa bill rather high - the Duster (oz1943), also by Mr Northrop, is a case in point. I call it 'The Flying Lumber Yard.'

The Galloping John looked to me like an ideal subject for conversion to a full house ship. Areas and moments compared favorably, proportionally, to some of the larger full house biplanes that fly very well. Also the little biplane was so cute it was hard to resist. That, coupled with my desire to reduce balsa expenditures, convinced me to press on.

As the name implies, the Galloping John was designed for galloping ghost radio. The multi and proportional gear available at the time it was designed was too big to fit inside. It was designed to be light, with plenty of inherent stability. While it was desirable to retain the lightness, it was also necessary to beef up the design to accommodate a larger engine and higher flight loads. I felt that some of the inherent stability had to be removed to provide the type of maneuverability I wanted.

This was easily accomplished by removing some of the dihedral in the wings. The top wing was built flat and the bottom wing was built with 1/2 in dihedral at each tip. This still provides adequate stability that can be easily overridden by the controls.

With the exception of increased elevator area, the outside dimensions remain the same. The addition of ailerons provides a fast roll rate, and the end result is the most delightful little airplane I've ever had the pleasure to fly. More on trimming and flying later. Now on with the construction.

CONSTRUCTION: Construction is similar in some respects to that described by Bill Northrop in the original article. I will only elaborate on my changes to the design and provide a few construction hints.

WINGS: The wing design was changed to a two spar configuration with a sheeted trailing edge. This was necessary in order to add the inset ailerons to the lower wing. To simplify things, I built both wings the same way. The ribs were redesigned due to the change in wing construction, but the original airfoil was retained.

Every modeler has a favorite method of making ribs. Mine is by using two aluminum templates. I drill a hole fore and aft at exactly the same location in each template. It is a simple matter then to sandwich pieces of balsa between the templates, drill holes through the balsa, and secure the whole thing toeether with two long 8-32 screws and nuts. Next, carve the excess wood off, almost to the templates, and sand to final form. With a coping saw, cut out the notches for the spars. Remove the templates and presto, instant ribs. Well, almost.

While I agree it is essential to build true wings, I do not believe it necessary to construct elaborate jigs (the exception perhaps being if you were going to mass produce the airplane).

I build the skeleton of the wing first in however many pieces is required. The upper wing, being flat, should be built in two pieces joined in the center. The lower wing. having 1/2 in dihedral at each tip and flat in the middle, must be built in three pieces.

After the skeletons, which consist of the spars, ribs and leading edge are dry, I turn them upside down and apply the leading and trailing edge sheeting to the bottom side. Using scrap blocks of appropriate sizes, align the assemblies as perfectly as possible and allow time for the glue to dry. I recommend Titebond for general construction. After the five subassemblies have dried, turn them over and apply the top leading and trailing edge sheets. This time, however, the assemblies must be pinned to a perfectly flat working surface and blocked in a true position because when the top leading and trailing edge sheeting is applied, the assembly becomes rigid. Any warps built in here are going to be hard to get out. By the same token, if at this point all your wing panels are nice and straight, they will most likely stay that way. Now, add the vertical grain 1/16 webbing between the ribs of the front and rear spars. Leave the center section open where the dihedral braces go.

On the flat working surface, using appropriate size blocks, join the upper wing halves. Epoxy the dihedral braces (or spar splices, if you will) in place and let dry. When dry, install the lower side center and tip sheeting. Turn over and once again secure the wing to the flat working surface. A simple, sure way to do this is to pin the front spar directly to the working surface and place a 1/2 in square stick under the entire length of the trailing edge. Use weights to hold the trailing edge down. This will insure that the wing is true..."

Modified Galloping John, MAN, March 1975.

Direct submission to Outerzone.

Supplementary file notes

Article pages, thanks to RFJ.

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