Schutt Tripe-Bipe (oz6549)

About this Plan

Schutt Tripe-Bipe. RC sport model. An interchangeable biplane/triplane design. For .60 - .90 power. Uses foam wings.

Quote: "A 'Modern Scale' Chameleon That Flies Like A Pattern Ship. By Howard Schutt

The WW I Nieuport, Fokker, and Sopwith triplanes were fascinating, unique machines. Highly acrobatic, they required a lot of flying skill and had nasty ground handling traits. Models of these tripes, many at 1/4 scale, are seen often at fly-ins, but are seldom flown. Pictures of model triplanes in magazines frequently included the words 'just before it crashed' in the captions. I wondered if a model triplane could be built,

utilizing up to date design and materials knowledge, that would have excellent flying and ground handling characteristics, so that it could cope with less than ideal conditions. I visualized a ship with simple lines, squared-off wingtips like the Ultimate Bipe, lightweight, relatively easy tq build, but still highly acrobatic.

In response to an urgent plea from our club newsletter editor, I whipped up a bit of instant history. 'The Schutt Triplane - The Best Kept Secret of WWI.' He promptly utilized it to fill up some space. That did it! I had to design, build, and fly an extraordinary triplane model to get off the hook.

The EAA has published a great deal of information on full scale biplane design and models with ± 10% modifications of home-built bipes abound in TOC competition. Why not blend this with the lessons learned from the best R/C pattern ships? Extrapolation of all this to a triplane configuration would involve a lot of calculations and assumptions on my part. Considerable research was done to determine the optimum positions, sizes, and shapes of the wings and tail surfaces, plus the track width and location of the main wheels.

However, I still had some doubts whether any triplane model would be suitable for extensive, everyday flying under adverse runway and wind conditions. So, concurrently, I designed and built components to be able to fly it also in a biplane configuration, using one larger top wing to replace the middle and top wings of the tripe. This required more calculations and layouts aimed at having the centers of lift, weight, and drag the some in both set-ups.

Now I can hear you saying - No way, Jose, I'm not about to build four wings for
one model - fear not, Clyde, and read on; there's a way to construct four lightweight wings from blue foam as easily as two built-up balsa wings for a conventional biplane. Proven features to achieve flight stability and straight-line tracking are incorporated in the design: a long tail moment arm, large tail surfaces, adequate vertical separation and stagger between the wings. These, combined with a wide-track main landing gear located at the ideal fore and aft point, plus a steerable tail wheel, optimize ground handling. A large rudder is employed for sure-fire stall turns and intentional snaps. The 6 in deep fuselage (needed for separation of the been and mid-wings of the tripe), plus plywood cabane and interplane struts, create the ample side area up front so desirable for knife-edge flight. The design includes semi-symmetrical wing airfoils and built-in lightness for both aerobatic capability and non-critical low speed flight, particularly in turns. The wing design is especially light for minimal roll inertia, so that rolls can be started and stopped quickly on command. The tail surface and rear fuselage construction is also very light to reduce the need for nose weight usually required on biplane models.

The goal was to produce an easy to fly, forgiving ship that avoids the problems encountered in flying many scale models, such as high or low speed stalls followed by a rapid snap into the ground. Additional goals were to have no changes needed in the CG the control surface throws or trims between the tripe and the bipe set-ups, plus quick and easy change-overs at the field.

An estimate of the vertical center of drag made it clear that the thrust line should be placed as high as possible. However, priority was given in the layouts to the correct placement of the vertical centerline of the engine carburetor relative to that of the fuel tank, to provide ideal fuel feed conditions without a pump.

The results of all this were better than I had expected. All the design features worked as intended and all the design goals were met! Weight was slightly under 8 lbs. Construction effort was about equal to that on my .60 powered Skybolt bipe (oz7537). Both the tripe and the bipe configurations are much easier to fly than the Skybolt and are about equal in this respect to my Dirty Birdy (oz4915) and very light Mach I (oz5462). Like these two old pattern ships. both the tripe and the bipe arrangements are so stable they will fly hands-off in a straight, level line for a considerable distance. Neither have any bad habits and both track through verticals so straight that my acrobatic maneuvers are much improved. During the first weeks of flying them I kept repeating out loud - I just can't believe they fly that well! More on this in the trimming and flying section at the end of this article. But this is not a model for the beginner. Care must be taken during construction to mount and align the multiple wings correctly. although this is not difficult to do. You should have some prior building experience and be proficient in flying an advanced trainer or a low wing sport ship before starting this one..."

Scanning by Don at EAC, cleanup by theshadow.

Supplementary file notes

Article, thanks to hlsat, JHatton.

Corrections?

Did we get something wrong with these details about this plan (especially the datafile)? That happens sometimes. You can help us fix it.
Add a correction