Chapter 9 - Landing Gear & Landing Brake

Start:  02/06/06
Finish: 04/26/06
Total Time: 95 Hours

The first part of this chapter involves a number of reinforcing layups done at the landing gear bulkheads and firewall.  At first, it seemed as though these reinforcements would be extremely difficult as they have multiple compound corners to them.  This combined with the need for these layups to be perfect, had me concerned.  I would soon find my worrying without merit, however, as they really weren't very difficult.  I was very cautious to ensure there were no air bubbles in these layups, and was very happy with the results.

After the reinforcing layups, it's time to prep the main gear strut.  The first part of this preparation is to sand the entire strut smooth and dull.  After trimming the strut to the correct length, we move on to the torsional reinforcing layup.  This is a 4 ply UND wrap, covering the entire strut.  Next we build the trailing edge of the strut, complete with a soda straw conduit for concealing the brake line.  I don't think I would have believed it if someone had told me McDonald's would end up being a supplier of one of my aircraft parts.  :)  After the trailing edge is built, there is another 4 ply UND torsional layup.  I was very lazy about taking pictures of these steps.  Most of work on this chapter has been in small chunks.  I haven't done a very good job of managing the tasks so far in this chapter.  There a fair number of little tasks that require cure time between them.  In the past I've been good about managing what tasks to accomplish on weekdays when I have more cure time than build time, and which to complete on the weekend, where the opposite is true.

After the final torsional layup has cured, we move on to building the attach tabs.  The FAQ on the Cozy Builders Site calls this task an exercise is geometric futility.  I completely agree.  I was ready to stab myself with a protractor by the time I started laying up glass for the tabs.  First everything is canted, squared and jigged in precisely the locations it would be if sitting in the fuselage.  Then we move our jig and strut upside on top of our work table, rechecking to ensure that everything lines up where it should.  This is where I had troubles.  Essentially the top of jig box was not completely level and flat, thus when flipping my assembly upside down on my work table my gear legs did sit at the proper angle.  This meant I had to shim the jig box to get the gear legs correct, and re-measure my location points for the attach tab holes.  Hopefully it will all work out when it gets into the fuselage.

Doing the first 45 ply layups for the attach tabs went fairly quickly.  Approximately 3 hours of wetting out glass, cutting into strips, and applying to the strut, was all it took.  From here things went a little awry.  The next step is to fabricate a drill guide from a block of 2x4 by squaring it on all 6 sides, then drilling a 1/4" hole perfectly perpendicular to the 4" wide axis.  You then use this guide to align your 1/4" drill bit with the pilot hole markings that were earlier made on the attach tab jig box.  Drilling through the guide and the first part of the tab.  I made one slight mistake however.  Instead of simply resting the guide block on my leveled work bench, I clamped the guide to the face of the cured attaching tab.  There is no guarantee that this face is perfectly 90 degrees from level, thus making the guide block tilt slightly when I clamped it to the tab.  My resulting holes started at the correct position, but were drilled at a slight angle, such that they did not line up with the hole directly across from it.  This caused me great concern, but I finally resolved to forego worrying about the pilot holes at this point and instead mark and drill them once I had the gear jigged correctly into the fuselage.  More on that later.  So I filled my original pilot holes with flox, and proceeded with the remaining 45 plies of fiberglass for the attaching tabs.

I wanted to wait with jigging the landing gear into the fuselage until I had the hardware needed to bolt it all together.  This hardware was on backorder, so I decided to proceed with other steps of chapter 9, the landing brake and landing gear cover.  I started with the landing brake.  I have opted to use the electric landing brake actuator instead of the manual mechanism called for in the original plans.  After slotting the bottom of the fuselage accordingly, and adding a couple of plywood hardpoints in my seatback brace I proceeded to glass the landing brake recess as well as the inside of the landing brake flap itself.  Once this was done I bolted the actuator in place and proceeded to test my very first moving part.  It seems so simple, yet I was so excited to see the landing brake deploy and retract automatically.  Click here to see the landing brake in action. :)

The landing gear cover was also built during this time, though we're waiting until the gear is situated correctly in the fuselage with all the correct hardware before doing the final trim of the cover, so as to create the best fit possible.

And just as we ran out of tasks for chapter 9...the hardware for the landing gear arrived.  What great timing.  The first step however, was to jig the landing gear strut into place in the fuselage so I could mark the precise location of the 1/4" pilot holes in the attaching tabs.  After it was jigged into place I used my laser level to project a locating dot through the forward landing gear bulkhead, onto the forward face of the landing gear strut attaching tab.  After drilling the hole on the forward face of the attach tab I re-projected the locating dot through the forward bulkhead and the forward half of the tab to now locate the hole on the aft half of the tab.  Drilling the hole if the aft half of the tab now created the straight set of pilot holes through the bulkheads and landing gear strut tabs.

I purchased the spot facing tools from ACS to bore the pilot holes to the correct 5/8" and 3/4" size.  Following the recommendation if others, I set the speed of the drill pretty slow to avoid wearing out the spot facers.  The 3/4" bit survived just fine, but I could definitely tell the 5/8" bit was getting dull towards the end of the drilling.  After verifying the proper location of the gear legs the mounting hardware was floxed into place.  Time to mount the axles and wheels.

The axles need to be mounted with a 1/4 degree of toe-in, which the plans have you set using a couple of plumb bobs and a 1/4" piece of tubing to site it in.  I decided I could be more accurate using the laser level to again project a straight beam.  After marking the centerline of the fuselage onto the wall, we use a little math to determine the location of a target to aim for to get our 1/4 degree of toe-in.  After marking the location on the wall we clamp the laser level to the wheel, make a pad of flox on the back of the axle and adjust the mounting bolts to bring the laser directly on top of the target.  We repeat for the other wheel/axle, and move on to final fitment of the landing gear cover closing in the landing gear bulkheads.