Well, here's another one...

Early Spring a year ago, I purchased a 40-46 sized Chipmunk ARF at a good price off eBAY.
The model was from a Chinese company, the name now escapes me. However, the quality of the airplane was self-evident or so I thought.

After mounting a new SK-50 2-stroker in the nose, balancing and fueling up, I took it to our local field for initial taxi trials. While the engine was broken in gently, the airframe suffered the consequence. After 1 hour of off and on running, the plane began to wobble so I shut everything down and re-examined the landing gear. Here is where the story begins.

I discovered that the 5/32” gear legs were flopping forward and aft in the bearing blocks. I stripped away just enough balsa skin to reveal them and was greeted with hardwood. So far, so good. The Chipmunk has a rather thin airfoil so I was not surprised when I shone a light into the upright bearing to see the underside of the top sheeting staring me in the face. Evidently, the bearing block to secure the upright portion of the wire leg was less than ½”.

Disgusted with the thing, I took it home and hung it up without even wiping it down and draining the fuel tank.
Fast forward to this week, over a year later….

My Dad expressed interest in returning to flying so I took the Chipmunk down, dusted it off and commenced to re-examine everything. This has always been his favorite RC model. I considered several different approaches to attacking the problem of the bearing blocks but finally settled on chopping my way into the wing panels to reveal exactly what was underneath. I removed top and bottom, wing skins from the main spar to the leading edge stock. I sanded all the skins away from the ribs and the ¼” square balsa leading stringer. Not much in there, no sir-ree.

What I found was a spruce,(or equivalent) block, ¼” x 4” supported by 3 ribs, 1/16” lite-ply and nothing else. Reinforcement was provided by 4, 1/4” soft balsa triangles set crooked on the block and not even engaging the ribs themselves. Had I not peeled the skinning away, even the softest of landings would have pushed the blocks right up through the top of the wing. So much for value.
I have several Balsa USA grooved maple landing gear stock pieces on hand and these will provide for the replacement bearings. Pre-grooved for 5/32”, they only need be cut to length and installed. The upright bearing pieces will be drilled, 5/8” diameter dowels from hardwood. The diameter of the drilled holes to be slightly less than 5/32” to insure a snug fit with no slop. I plan on sanding a flat on the dowels to provide maximum surface area for epoxying to the ribs. However before that step, new rib pieces cut from 5-ply birch aircraft grade plywood will be inserted along with 2 additional false ribs to support the load. These all will be 1/8” thickness. Spruce wood triangle stock will be epoxied on the reverse sides to hold everything rigid. A re-skin of 3/32” balsa will dress it all up followed by a complete recover of the wing with Ultracote white.

Anyone buying Oriental ARF’s should seriously consider a close scrutiny of the critical parts of their models. Firewalls, landing gear plates, etc., all appear to be areas that these manufacturers are skimping on.

PM