Flex Innovations Cessna 170 Landing Gear Repair/Upgrade

Story: I bought a Flex Cessna off of an older gentleman who gave it a few hard landings. The bottom gear fuselage piece was beat away in the corners, and the retaining insert was broken and fiberglassed back together.

To get her in the air I quickly jammed a wood shim into the slot to tighten the gear up. I knew a long term solution was needed but wanted to fly this beast. Turns out this is my by far favorite plane out of a hanger of 10!

So, back to engineering. Replacing the fuselage piece seemed like mission impossible even for myself. So instead I mixed up some epoxy and 3M glass micro-bubble to fill in the corners. Once cured I sanded it down to the original shape. To further strengthen it I glued the bottom of the channel which was broken in front due to hard landings. This fixed the fuselage, but what about the insert?

Being the Mechanical/Aerospace Engineering student I am, I quickly made a CAD model of the insert. Then 3D printed a couple prototypes to make sure I had the geometry perfect. Once I was satisfied, I then made the plan to make the entire insert out of carbon fiber. The outer part (let’s call it the top plate) and the inner rib would be two separate pieces. The top plate was made by printing a mold for it, then laying up the carbon 6 layers deep. 3 0/90 ply and 3 +-45 ply. Vacuum bagging this resulted in a lightweight part.

The inner rib was made by 3D printing a honeycomb shape to the correct thickness, accounting for the plies of carbon that would go outside. Then I laid up a flat 2 ply plate, cutting the desired shape out of that (2 of them) and sandwiched the 3D printed part within it.

Final assembly consisted of cutting one of the sandwich plates oversize, as to act as a spacer for the landing gear wire. This worked well and would also help reinforce the forward part of the fuselage channel. Once both top plate and rib were cutout and to the desired shape, I glued them together on the plane with some 30min epoxy (being sure not to glue the whole thing to the plane!) I’ll get more pictures of the end result as well as the prototypes because they look cool 😁

Finishing the project, I coated the outer layer of the top plate in epoxy, sanded smooth and applied a shiny coat of lacquer to give it that pretty shiny we all love.

The end result seems to be very strong, I hope to get some flight testing (with video) soon!

I may end up producing these if people are interested.

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