Damaged landing gear caused by landing off-field is probably the single most common repair needed during an RC model’s lifespan. While flying a 30cc Ultimate biplane from Aeroworks, an engine out on the downwind gave us a bad case of landing gear down.
Test Pilot and MAN contributor Aaron Ham was doing an inverted pass when the plane went dead stick heading downwind and too low for a safe 180 turn. So he settled the plane into the tall grass at the end of the runway with a broken prop and badly tweaked landing gear for his trouble.
Here are some tips to make this all too common repair, it can be done on various other ARF models with bolt on landing gear.
The Damage isn’t terrible but to do a proper repair you have to first examine the plane and remove all the damaged parts.
Unbolt the gear and use a tray or pan to keep all the hardware and screws together so you don’t lose anything or have it get under your plane to cause hangar rash!
I always like to use a foam work stand like the ones from Robart Mfg.
Of course since the propeller is also busted, remove the cowling and check the engine, firewall and engine mount.
Once the gear and engine cowling is removed, you have to remove the covering. Use a Covering Heat Gun set on high to heat the covering. It will over heat quickly and begin to lift up from the wood. Peal it away and when you get to the undamaged parts of the sides, use a sharp hobby knife to make clean cuts in the covering so you can make straight repair seals.
If you have any fuel dots or drain/vent fittings, simply remove the fuel lines and remove them and the surrounding sheeting.
Clean off any glue and you can reuse the fittings
Remove all the damaged sheeting with a sharp hobby knife.
As you remove the damaged wood, be sure to inspect the internal structure and make sure that there are no other damaged parts deeper in the fuselage and that all the glue joints are sound. Here you see the aluminum support angle that ties the landing gear to the internal structure.
Remove the rest of the damaged sheeting from the repair area. I find a razor plane works great for removing cracked and split sections of wood from the underlying structure.
Remove the broken landing gear attachment plate and set aside.
Finish cleaning up the underlying structures and sand the edges smooth with a sanding bar. This will allow the new balsa sheeting to make a strong bond.
To maintain the proper bolt spacing, bolt the damaged parts of the landing gear plate back into place and glue them together. This gives you an accurate template for making the replacement plate. After the glue dries, remove the old plate.
Place the old plate over some 1/8 inch Aircraft grade plywood and trace its outline. Accurately transfer the outer bolt hole locations as well.
Cut the new plate out with a band saw then use a belt sander to smooth out the cuts to the pencil guidelines.
Sand the ends to the proper length and angle to match the fuselage sides and then drill out the bolt holes on either end of the new plywood plate.
Test fit the new plate and lightly bolt it into place to make sure the bolts align with the threaded parts of the underlying metal angle supports. If there is a light misalignment, you can drill a slightly larger hole fto provide clearance.
Bolt the landing gear in place as show above and use a straightedge stick to make sure the gear are straight and square to the fuselage centerline. Once they are properly aligned, tighten the two outer bolts and then drill out the inner bolt holes. Then trace the base of the gear.
Here’s the final bolt holes and gear guide lines.
Now use the new plate and trace out a lite ply spacer to form the recesses the landing gear will fit into after the repair is complete. You also have to add a little extra length to the spacer piece so it overlaps the fuselage sides.
Cut away the center section the gear will fit into and use a sanding stick to clean up the cutouts to fit the gear.
Carefully glue the spacer on top of the plywood plate aligning the openings with the guidelines you previously drew on the plate. Red Baron Adhesives Medium CA and accelerator is being used here. Make sure not to get any glue inside the recess area.
Use the cutaway part of the lite ply spacer and glue to the underside of the plate centered on the inner attachment bolts holes. Drill out the holes and then install blind nuts for the inner landing gear bolts. For this plane the bolts are 6-32 cap-head machine screws so 6-32 blind nuts from the hobby shop are being used. I used a plastic face dead-blow hammer to set the blind nuts into place, and then I use medium CA to secure the wings of the blind nuts. be sure not to get any glue in the inner threads.
Using the outer bolts secure the new gear plate to the fuselage, applying adhesive to all the mating surfaces. Red Baron Adhesives’ CA make excellent bonds to metal and wood, but use only a small amount so it does not get into the threaded areas. Properly glued into place, the top of the lite ply spacer should be flush with the top of the surrounding structures.
Cut the new balsa sheeting to size (I used 3/32 inch sheeting), and glue it into place, Leave a small space between the edges of the landing gear bases and the edge of the sheeting. A good way to make neat gue joints is to apply the glue to the model and then spray the accelerator to the underside of the sheeting. Then place the sheeting into place and hold for several seconds until the adhesives cures. After the large sections are glued in place, cut the center sheeting piece to size and glue it in place between the landing gear bases to form the finished recessed areas.
Remove the landing gear and this is what you are left with. Scrap balsa sheeting will be used to fill the gaps.
Cut the scrap to length and glue into place with thin CA glue.
Sand the scrap flush with the fuselage side and then sand the corners round with a sanding block. Use 100 grit sandpaper then finish sand with 220 grit until everything is nice and smooth.
Apply some model filler ( I like Hobbylite filler from Hobbico,) and fill any gaps or defects in the glue seams and let dry.
Use some 220 grit sandpaper and smooth out the filler. The model’s repair area is now ready to be recovered.
Before reinstalling the landing gear, now is a good time to clean them up and to check for any damage or loose screws needing to be taken care of. It is eaier now than when they are reattached to the model.
Clean off any sawdust and clean the fuselage covering with some solvent to properly degrease the surface then iron on some new covering material that matches the model’s finish. Start from the center of the repair area and work outward pulling out the wrinkles as you go. Take your time and make all your seams straight and neat. Now bolt the landing gear back into place. If your hardware is bent or damaged, replace with new bolts and washers.
A neat and quick way to make the holes for the fueling fitting and drain/vent, is to use a sharpened piece of brass tube. Bevel the inner edge with a sharp hobby blade and sharpen the outer edge with fine sandpaper. Press the tube cutter against the model and push firmly with a twisting motion to cut the hole. Side the tube cutter diameter to match your fittings.
Reattach the fuel lines to the fittings and use thin CA glue to secure the fittings within the new holes.
Add a little lock-tite thread locking compound to the landing gear attachment bolts and tighten them securely into place. That’s it! Reinstall your engine cowling, stick a new, properly balanced prop back on your model, reinstall the spinner and you’re ready for your next takeoff!