| Chapter 9 |
| Landing Gear & Landing Brake |
Main Gear
Well the gear from Featherlite arrived after a long 5 month wait. Unlike some other lucky people, mine came complete with flashing, bumps and other stuff that would have to be fixed. It took about an hour working alone with the belt sander to get all the bumps and flashing off the gear and to remove the 'buldges' at the trailing edge. Then another two hours were spent hand sanding the entire strut to prep it for glassing. WEAR LONG SLEEVES!! I did not and I paid the price with very itchy hands and arms for a couple of days. There is also a requirement of cutting the strut at 8 degrees. My first attempt at this failed to yeild the correct angle (more like 4 degrees) so being ever so determined, I printed an 8 degree angle on paper (using turbocad), lined it up on the strut and cut the proper angle. I would say that doing this is the easiest way to go (especially if your power tools hate you the day that you try to cut at 8 degrees). After all this fun it was time to do the torsional layups. These look easy enough. I mounted my strut to the bench on three nails per plans cut the cloth and started. No sooner than I started the first layup, the entire strut popped off the nails. Aeropoxy was curing so I really didn't have time to fix anything, so I lifted it back up onto the nails and started working again. By some miracle the strut maintained it's balance on the nails for the duration (whew!). After cure, I spent another hour or so, fairing in the leading edge.
After the first torsional layup I installed my soda straw conduit (hint: You will need six straws from MCD's, not the 20 that I took.), and then install a 2 bid layup on an aluminum tape backing. No matter what I tried, I could not get this straight as I wanted it, and in the end had a few little wrinkles that will have to be fixed during finishing. Another problem that I ran into was my aluminum tape was too sticky and didn't want to release, and when it did it left a residue. I cleaned the residue with a tape remover solvent (which worked quite well). If I were doing it again, I would stick a piece of peel ply on the tape that extends above the straws. This would prevent the sticky problem, and leave the surface ready for the next layup.
For the next torsional layup, I made darn sure that the strut was thoroughly in place on the nails! The plans didn't mention how to cut the glass, so I followed the procedure for the previous layup. This ended up with the glass sometimes being about 1/2 inch too short on one side (mostly because of slight variances in my cutting). If I were doing it again, I would allow an extra inch of cloth on the second torsional layup. This would meet my philosphy of having too much is better than being a little short. This layup went well and even though the plans didn't mention it I added peel ply at the attach points and at the center where the layers butt together. After cure another hour or so of sanding to fair in the trailing edge.
Building the jig box for the tabs. This section was a royal pain!! If you read other chapters, you will see that I often manage to mis-read my tape measure, (so I have to triple check measurements all the time) this will not come in handy for this part of the chapter. The first thing that you do is to create a backboard between the conduit lines and align it vertically. Placing the 'feet' of the strut 9.25 inches in front of the board the strut is then supposed to rest trailing edge on the board flush with the tab area. Mine was out about 1/16 inch on one side, which isn't surprising after reading all the archives, actually it seems to be the norm. The plans then say to make markings all over the back board starting with the center line, then 13 inches from either side of the centerline. You are now supposed to measure and mark a line 3/4" above the highest point at the 13 inch mark NOT THE HIGHEST POINT OF THE STRUT!!! However, my first attempt used the centerline. Since I double and triple check measurements, I found that I couldn't get the 4.25 inch reference dimension before I built the box. Confused by this, I started reading the archives, and found that I am not the only one who misinterpreted these instructions. So I go out and mark my line this time at the correct point (forget to measure 3/4 inches up) and make my other lines. After building the box and measuring everything again, I was confused as why the attachpoints were so close to the strut, almost as if the drill would go through the strut. Then in an awakening of sorts, I realized that I hadn't moved the point up 3/4". After doing so all seemed well again (although my reference dimension was only 3.5" so I septuple checked all my measurements again. Done! The box was ready for tabs.
Making the Tabs
The tabs looked much more difficult than they turned out to be. Following the plans I traced onto my strut and jig box where the glass would lay and then made the layup as directed. Once it was cured I was very careful to remeasure the "reference dimension" and create a jig block to drill the holes. After all four holes I broke apart my jig (which took a lot of banging, cursing, and sanding), and did the inside tabs. I made the mistake of making the inside layups almost touch. This just created a lot of grinding later when installing the MGMA's. It would be best to follow the profile drawings and keep most of the glass off the high part of the strut.
Mounting the Gear
I thought that this would go easy, but I should have realized when Nat says that you will most likely find out that you will have to do something (say like opening the 1/4" holes), you will indeed need to do it. At first my gear was about 1/16" from being down far enough to get the rod in. After a little investigation I found that the gear was resting on those little plywood triangles that were installed way back in Chapter 7. I asked Nat, and he said that this was intentional and that I could cut away as much of the triangles that I needed to get the gear installed and still maintain at least 3/16" clearance. So I cut a couple of 1/4" swipes out of the foward triangle and then smaller cuts out of the aft. Now my biggest problem was that the holes needed to go up in order to get the strut level. This created a problem since the strut weighs about 30lbs and gravity still works. After filing away to get the holes at the correct position I used blocks of 2x4's to support the weight of the strut from the tab to the LG box. I could then verify the position of the strut and get the rods to slip in and out quite easily. Which then allowed me to get the MG-1's installed with some bondo and then the MG-2's. This process took me quite some time as I wanted the alignment to be perfect, which meant I wanted to lift the strut on and off the plane at least 30 or more times. I opened the 1/4" holes using my trusty hole saw to 5/8", which worked great! After completing this I checked my MGMA's for fit between the MG-2's. Yep, found another problem. While the one on the left fit near perfect, the one on the right would not fit with the bushings in place, actually it fit snug with just the tube. I measured the tubes and found that Ken Brock's Mfg had made them both 1/16" longer than what they should be. I contacted Nat about this and the solution that he gave was to file the face (flange) of all four bushings until it would fit together snugly. I imagine that more error was also thrown in from tolerance build up between the fix for my joggles and perhaps my 8" spacer used to mount the bulkheads was slightly off. Anyway, after quite a bit of filing I got everything to fit nicely and floxed the bushings in place, although I don't believe much flox stayed on the bushings, as most of it seemed to get scraped off as the bushing went into the bulkhead. This also seemed to be the case when installing the tubes into the tabs. Getting the strut into the fuselage with the studs was an exercise that took an entire night. I believe that the left aft bushing was out of alignment by maybe .002" which meant that it was very difficult to get the stud to "slide" in. As a matter of fact it was darn right unpleasant. But after jiggling and tapping lightly with a hammer (the strut and the stud) it finally "slid" into place. I just never want to have to take it out. Now there is zero play in the gear.
