John Marquette 1/3 Scale Aeronca Champ
I received the John Marquette 1/3 scale Champ plans some time ago to quote a build for a customer. He decided not to build but those plans just kept staring back at me until I finally gave in and started building one for myself. This will be a pet project for myself over the next few years to work on when customer jobs are slow. For someone who likes to build (as I do) this is the perfect aircraft design. The model is a good reproduction of the full size in every aspect. The wing ribs are all built-up truss construction as in the full size. There are also details on the plans that will allow you to copy the landing gear/suspension of the full size. The plans are very well done yet I wouldn’t recommend this project for the novice builder. If you have any scratch building experience at all you should have no problems with this plane though. Because this is such a nice project, I will be including some descriptions along with the pictures in case anyone would like to follow along with the construction. If you have any questions or comments, or would like a more detailed picture of any areas, please feel free to email me and let me know what you would like.
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Cover of November 1991 issue of RCModeler magazine featuring the 1/3 scale Aeronca Champ designed by John Marquette. The Champ has a wingspan of 141" and a fuselage length of 85". It is designed to use a 40-50cc engine.
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Page 52 of November 1991 issue of RCModeler showing the 1/3 scale model alongside its full-size counterpart.
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The beginning of a long haul! Picture showing 2 W-15 ribs and 1 W-2 rib. All ribs W-2 through W-15 are built up truss type using 1/8"x1/4" spruce and 1/32" plywood gussets. Most of the ribs are similar enough to be jigged so I tried several different ways of jigging them. After not coming up with a good jig, I ended up building each rib seperately over the plan using one rib as a template to ensure they were all the same.
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Close up of one Rib W-15 with a ruler for size comparison. Medium CA was used for all glue joints including the gussets.
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Almost 40 hours later all 18 full ribs are ready to go. Only the 10 ribs in front of the ailerons left to build yet. You can also see the main wing spars in this picture.
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Closeup picture of the main spar layouts. The drawings called for a 1/4" balsa spar wrapped with 1/32" plywood but I didnt like the idea of having splices in a 6' long spar. After making some calls, Joel (fellow club member) remembered his work had a "scrap" pile of poplar material from crating. Next evening Joel brought some material home and we cut the spars to size in his shop.
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Framing of left wing panel. Due to the odd shape of the bottom chord of the ribs, and because of the rigidity of the design itself, it is not necessary to build the wing panels over top of the plans. All that is necessary is to have the spars laid out properly and to make sure each rib is square to the spars. All rib/spar glue joints made with thin CA followed up with a fillet of medium CA.
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Another view of the left wing panel framing.
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Picture showing front main strut mount. Strut mounts are cut from 1/16" sheet steel and mounted to main spars with (2) 4-40 bolts with nylon locknuts.
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Leading edge ribs glued to front spar with medium CA. All LE ribs are cut from 1/4" balsa sheet.
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Another view of the left wing panel framing including the LE ribs and LE. LE is built up from layers of 1/4" balsa and sanded to airfoil shape.
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Beginning of 1/8" balsa LE sheeting. Sheeting applied to ribs with medium CA. The butt-joints are staggered on different ribs from top to bottom to add strength.
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View of bottom LE sheeting showing a strut mount protruding through.
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Another view of LE sheeting. The sheeting stops where the wingtip bow will start.
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Image of the wing root from the rear. Wing tubes are simply 1/2" aluminum tube bolted to each spar with (2) 4-40 bolts and nylon locknuts. I also added a fillet of epoxy/milled fiberglass for a little extra security. Wing tubes will then be bolted inside the fuselage in a similar manner. Wing struts on this model are obviously structural.
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Another view of the wing root tubes from the front.
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Left aileron framing. Standard construction with a main spar and aileron ribs. The trailing edge is made from 1/4" hardwood dowel.
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View of outer aileron hinge. Hinge is made up from 1/16" sheet steel and bolted to wing frame with (2) 4-40 bolts and nylon locknuts.
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View of inner aileron hinge.
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Another view of outer aileron hinge including the aileron framing.
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View of outer aileron hinge after TE sheeting is applied.
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View of inner aileron hinge after TE sheeting is applied.
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Picture showing the left wing inner belcrank. Left aileron servo will be cut-in and mounted to the plywood plate. There will be no need for long servo extentions.
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View of left wing outer belcrank. Belcranks are cut from 1/16" sheet steel with small inner nyrod bushings for the cables. Im really not happy with the slop in the z-bend configuration and plan to change this setup to use ball links.
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View of left wing control cables. There is a pull-pull setup from the inner belcrank to the outer belcrank. Pushrod from outer belcrank to aileron hinge.
Update March 2012: The Champ has been sitting here collecting dust for several years and I just don’t know when I will have time to get back on it. I received an offer from a viewer who wanted to purchase what I had completed and continue the build so the Champ has found a new home.
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