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Chapter 9 Main Gear & Landing Brake

Bulkheads reinforcement

Horror stories about the dreaded landing gear box had me a bit uneasy.   I began with what I considered the easier of the 3 reinforcement schedules: the area between the aft landing gear and firewall.  After radiusing the corners, micro the foam and inside corners, I traced the template outlines and wetted out the fiberglass on HD aluminum foil sheets, used the Dritz scissor to cut out the patterns, and carefully brushed them onto their locations.   This layup wasn't difficult but my back is sure sore!

I next reinforced the foreward landing gear bulkhead areas.  The plan's method of cutting out the fiberglass to size did not work well for me.  Following the suggestion from another builder, I used a sheet of glass large enough to cover the area, and patiently worked it into place using a 2" brush and epoxy.  It took me at least 2 hours to wet out the 5 plies needed per side.

The toughest layup was the area between the landing gear bulkheads.  I made a paper pattern of the area to cut out the fiberglass cloth and did all the layups on the work table before patiently working the wetted out plies on the area.

Landing Gear Torsional Wraps

The landing gear bow was sanded using a random orbital sander with 36 grits paper.  It took about an hour to thoroughly remove all the shine from the Featherlite gear leg.  The gear leg was exactly 96" and required removal of 0.5" per leg.  The 8° cut line was marked and the area was removed.  I found another use for the Fein (really fine) tool, it really expedited cutting the gear legs, whereas the hacksaw was painfully slow.  BTW, it's worthwhile to repeat the plans' suggestion to wear long sleeve shirt and dust mask... the S-glass shards can cause significant discomfort!

The landing gear bow didn't need to have the bumps remove since the width was less than 5.75".  Adjustment will be needed to the jig box to accommodate the gear tabs construction.  Cutting out the 12" wide UNI strips were easy once the initial 30° cut was established.  Bernie Siu did the trigonometry thus simplifying the guesswork in making the first cut.  Using the Dritz scissor, subsequent strips were cut using a length of wax paper which happens to be 12" wide.  I cut a total of 10 strips. The gear bow was placed on elevated nails for the first set of torsional layup.  The layup was done without any difficulties, but it took 4.5 hours including the peel ply application.  After curing for 24 hours, the excess glass trimmed, the leading edge area contoured, and the whole gear sanded with 36-grit.

The brake line conduit was made using 3/8" OD vinyl tubing as suggested by the FAQ.  The tubing was scuffed and 5-min epoxied.  The trailing edge support was provided by using 3 layers of aluminum duct tape.  The 2-ply BID layup over the brake conduit area was completed without much ado.  The entire area prep sanded for the final torsional layup.

Attach Tabs

The jig box was formed per plans after multiple careful measurements.  I used the saber saw for the 45° bevels.  The strut was transfered on the work table.  The 6' straight edge between the two gear ends leveled out at 0.0°, and the plumb bobs off the gear legs were both a couple millimeters aft of F.S 108.25 with 1/16" shims under the forward face of the jig.  Good enough for me!  Gear tab layup to begin...

After a lull, I began work on the gear tabs.  The process was per plan without much ado.  The outer tabs layup took about 3 hours.  The 1/4" tab holes were easy with the air drill motor.  Hole alignment was pretty good since the 12" drill bit easily span the holes and is 3/4" from the strut.  Trimming the tabs is a snap with the Fein tool a palm sander with 36 grit sandpaper.  Notice that I didn't trim the tabs full thickness to 3" wide across the strut, no particular reason except that I didn't want to risk cutting into the gear strut. 

Be careful, the inner tabs layup schedule is exactly opposite from the outer tabs: 20 UNI and 25 BID layers.  This step took a bit more time since I had trouble keeping the layup from sliding under the clamping pressure.  They turned out OK with a few small gaps that I'll fill with flox after trimming.   While waiting for the outer tabs to cure, I decided to work on the landing gear cover.  Since I am concern that the foam stuffed inside the hell hole will shift if removed, I will wait until the the landing gear cover outer surface is glassed before continuing with the landing gear installation.  Meanwhile, I made the MG-1s and MG-2s.  They were easily made with the bandsaw and drill press.

After spending considerable effort and time wrestling with the gear leg, I managed to insert the 1/4" drill bits through the gear tabs and bulkheads.  One of the aft gear bulkhead hole had to be elongated.  The landing gear leading edges were off by almost 1/4", within tolerance, after the smoke settled.  The forward pair of MG-2s were too long for the angled bulkhead section, so I decided to make a shorter set instead of beveling to fit.

Drilling the 5/8" holes is an exercise in patience.  I tried using the counter bore tool, stopping frequently to allow for cooling, was very slow going.  The archives contained plenty accounts of hole saw usage so I gave it a try.  The hole saw does cut faster, but it also gets hot and required frequent stoppage for cooling.  Minor hole adjustments were needed to allow the gear stud to thread between the MG-4 bushings.  A surprise was the 1/16" gaps on each end of the MG-4 sleeve.  I got a few responses to my query confirming that any play in the gear sleeve is unacceptable, the standard AN washer is 1/16" thick and should help eliminate the gaps and gear slop.

Installation of the Matco wheel/brake assembly was straight forward.  The fuselage was leveled longitudinally and laterally, gear strut was installed and checked for levelness.  The axle center was identified and utilizing the axle template obtained from Bernie Siu, I determined the layout on the strut end.  The fine Fein tool was used to rough cut the strut end and final shaping achieved with a palm sander and round sanding stick.  The axle bolt holes and backing plate were drilled using a 1/4" bit.  I followed the plan's method of bore sighting the toe-in alignment.  After determining the aiming spot, I flox the backup plate and the axle (covered with packing tape) to the gear strut. Be sure to wax the bolts before installing lest you want to have a very bad day to follow.  Using the flat end of the axle as the rest for the aiming tube, I adjusted the toe-in by tightening or loosening the bolts.  After allowing a full day for cure, I removed the assembly and had a nice flox pad on the axle side that I'm confident is within the toe-in specification.  This method seems a lot easier than the block clamping method described in the plans.  My thanks to those who had documented this better method of alignment.

Landing Gear Cover

While waiting for the outer tabs to cure, I began work on the landing gear cover.  This is a departure from the plan.  I believe it was during chapter 6 or 7 that I became committed to Wayne Hicks' gear cover method, since I didn't install the aluminum slugs and create the joggles along the landing gear bulkheads.  We'll see if this deviation will cause me grief.  Bernie Siu has also done a marvelous job building his gear cover a la Hicks, so I will shamelessly follow their examples.

Landing brake

The landing brake cutout lost large chunks of foam and the glass side was creased during the removal.  After consulting with a few builders, I decided to remake another landing brake using the damaged one as a template.  The lesson for me is to not go crazy with the 5-minute epoxy blobs when securing anything.

It was a straight forward installation.  A boo-boo occured when I installed the LB-19 in mirror image, luckily I realized my error and removed it before the flox fully cured!  Placement of the actuator was the most fun, requiring a few attempts and email clarification to Ron Springer.  Eventually I was able to locate the brackets and achieved about a 63° deflection, which I'm told is adequate.

Mods: Following the suggestion from a builder, I extended the LB hinge to 16" long from the original 10" per plans.  The added length added rigidity, strength, and a little weight to the structure.  LB-19 was widened 1" laterally per the FAQ, and installation of the Wayne Lanza brake actuator.


Remi's Cozy Mk IV Project: Chapter 9 Main Gear & Landing Brake

created by Remi Khu
last modified: November 27, 2006