We had a cameo appearance from John today. It was nice to have him back in the shop. Today started with cleaning up the layups from yesterday. I am pleased to report that these layups went well, and I am happy with the installation of the anchor plates. We installed the pivot anchors and hinge pieces and they all actuated as they were supposed to.
Next was fitting the doors to the hinges. Basically just cutting a slot in the door reinforcement to allow the hinge to lay flat agains the outer skin. Then the doors were 5-minute floxed to the hinges to check actuation. Lo and behold, they actually work now as they were intended to. I can have an overlap of the gear doors on the fuselage, and also get them to fully open without binding.
At this point, with the tire door actuation confirmed, we switched to working on the forward gear door flap. This is the one forward of the nose gear pivot. We decided to go ahead and use the piano hinge on this one since the gap the piano hinge creates is minimal, and I don’t want to go through 3 iterations of this door to get it right.
So we cut a hinge, fit it to the door and fuselage structure, and drilled holes for mounting. The other part that needed to be addressed was getting the spring for the spring loaded feature. So we went to the hardware store, and didn’t find anything better than a mouse trap spring. It still needed to be modified. We had to learn a few things to modify the spring though.
In order to cut the spring to the length that we needed, we had to unwind it. In order to unwind it, we had to anneal it. So we heated the spring up with a torch to a cherry red, and unwrapped the necessary coils and created ends with the excess wire. On one of the ends, we created a hook to engage a stud on the gear door. The other was left straight.
After the spring was modified, it was brittle. We broke the first one. I somewhat expected this, but didn’t know much about heat treating. A quick google, and we learned how to relieve it, and temper it to return the strength and get rid of the brittle. Basically we heated the whole thing to a cherry red, quenched it in a bucket of water, and cleaned it with scotch bright. Then it was slowly heated to a bright blue color and quenched again in water. This returned the spring to a strong, non-brittle state.
We dry assembled the gear door with spring, and tested it. It worked as expected, but the spring tends to take a set with less spring load than planned. Jury is still out on the spring for now. It may be salvageable by slightly changing the angles and re-heat treating. Otherwise we may have to make a new one. But it is nothing that keeps us from proceeding.
The next steps were permenently floxing the hinges to the gear doors, and floxing on some Click Bond studs to the forward bulkhead in order to mount the froward gear door. The floxing of the hinges to the gear doors is self explanatory.
The Click Bond studs were bonded in place using the actual hinge that mounts the forward door. Release tape was put on the hinge, and the base of the studs were prepped by making sight cuts in the bases to give a bit more mechanical tooth to prevent rotation. These studs were then cleaned with acetone and the studs were temporarily mounted to the hinge. A dab of flox on each one, and it is left to cure. Two plies of BID will later be applied over these.
We also installed the tires on the airplane to verify location for the nose down parking bumper. We used a long straight edge to confirm that any place forward of the forward gear door will work for the nose bumper to keep the nose off the ground. That will be one of the next things installed.
Lastly, I added a bit of flocro to the induction scoop to allow me to fix the uneven planform. The shape of the scoop was lopsided, and too much was sanded away on one edge to create a pleasing curve. So I added a bit of flocro back to create a strong, but finish able edge. This will be sanded down to a similar curve to the opposite side.