Chapter 9 - Section 1

Main Landing Gear  & Landing Brake

 

What's up?

In this chapter, we will install the main landing gear and the landing brake. This includes all the reinforcements to attach the main gear onto the fuselage, the wheels, disc brakes, brake lines and brake fluid reservoir. The landing brake (i.e. the big door under the belly) will be electric driven and this will be the first moving part for this project. This is a long chapter and is divided into several sections:

 

  LG Bulkhead Reinforcement   Preparing Strut   Attach Tab 

 

  Landing Gear Cover   Axles, Brakes & Brake Lines   Landing Brake  

 

 

Forward Landing Gear Bulkhead Reinforcements

Before installation of the main landing gear, the fuselage has to be strengthened or reinforced. Reinforcement is required at the forward, middle and back of the bulkheads.

 

For the forward bulkhead, 5 layers of BID (2 different sizes) is required. This is one of the more complicated surface profiles for glassing thus far. Anticipating the challenge, I took time to prep the surfaces. That included grounding down the doublers, rounding off the edges and floxing in corners. I also tried various approaches including pre-cut cloth patterns (as suggested by the plan), pre-wet the cloth, used different kinds of plastics - all with little success in reducing the struggle. The wet cloth kept stretching at the wrong places and wormed around instead of staying put . I finally got the hang of it by the time I completed the left side. All the trials and errors took me a good 4 hours.

 

Since all the fancy footwork didn't help much on the left side, I decided to return to the basics... here's what I did on the right side. I marked out the area to be glassed, and prepared the surface as I did on the left side. Then I brushed down the fuselage surface area with pure epoxy - ONLY inside the marked area and AROUND the seat belt anchor (wood base). I cut a piece of 10"x23" BID. I started by lining up the BID against the forward and top edge of the area and worked the cloth towards the back of the fuselage. You'll find excess cloth over the bottom edge at this time - that OK, because they will be trimmed off later. I paid special attention to tugging in the corners and around the edges where the three surfaces meet. The front end of the glass should be tacked in place by the underlying epoxy. I continued to work the glass up the slope along the marked edge until I got all the way to the top. Once accomplished, I wetted out the glass - again ONLY inside the marked area! I repeated this approach for the remaining 2 plies. Don't forget about the 2 plies over the hard points. Now comes the trimming...          

 

It should be clear by now that there's only excess glass at three (3) locations for trimming - along the fuselage floor and up the bulkhead wall; along the slope edge of the bulkhead; and a small area around the wood seat belt anchor. I used my Dritz scissors and trimmed the excess glass - JUST A BIT inside the wetted edge at the fuselage bottom - the excess should still be dry but is held together by that little bit of wetted glass you are trimming off. Trimming along the bulkhead edges and around the wood anchor should be easy as we have done it many times before. Once completed, I brushed down the unsettled edges, peel plied and let cure. I did not pre-cut any pattern or dart for the right side and it took me approximately 1/2 the time to complete. Oh yes, a bit of patience always helps !

 

Reinforcement Between The Bulkheads

Since I still have my fuselage on the rotisserie, I rotated it to its sides for this operation. I did not make a pattern as suggested per plan. I just cut up three triploid shaped BID (per plan dimension) and epoxied them down one at a time the traditional way and peel plied. I trimmed the edges with scissors prior to curing. Once cured, I laid downed the remaining 2 plies of BID per plan. I did not have much problem with these lay ups.

 

 

 

 

Reinforcement Between the Aft Landing Gear and Firewall

I followed the plan method closely for this lay up. I rounded the outside corners of the foam, sanded glassed area dull, vacuumed, microed the foam and radius the inside corners with micro. Due to the tight space, I used a syringe to apply micro onto the inside corners and  smoothed them out with a shortened & trimmed stir stick. I also shortened the brush handle for tugging the BID into the corners.

 

I made two separate patterns - one for each side because they vary just a bit. I wet out the BID on a 4-mil plastic, trace out the pattern and cut to exact shape. I painted the epoxy on the surfaces to be covered and placed the lay up in position. Then I stippled out trapped air bubbles. Since I was a bit ahead of time, I added the last 3 plies at the same time. Then I peel plied all rough edges.

 

Generally the reinforcements were not too bad except the last ones - it'll give you a backache you won't forget...

 

Torque Tube Holes

I did not tackle the torque tube holes until all the reinforcement lay ups were completed and cured. After I marked the hole locations (hole centers) per drawing, I found that they do not quite line up. Depending which two holes I connected up, the third one could be as far as 1/4" off.

 

Clueless, I decided to post a question to the Cozy forum. The next morning, I got 10 great responses, ideas and guidance. You can probably find all those responses in the archives. Most importantly, the recommendations helped me to understand where the torque tubes are coming from (or going to) before deciding the direction of the drill bit. The answer to that required a quantum leap to Chapter 16 page 2, 4, 5 and drawing M8 & M15. Basically, the position of the torque tube is determined by two points - one at the firewall and the other identified by CS118. The position at the fire wall is BL14.25R and WL12.25 (refer to Chapter 16, p.5 and drawing M8). The position for CS118 (torque tube holder) can be found in Chapter 16, p.2 & p.4 and drawing M15. My calculation indicated the center point of the torque tube at CS118 is WL11 (M15), 2 3/16" forward of the back edge of front seat back (M15) and 1 5/8" away from the side fuselage wall (CS118 dimension). The holes in the bulkheads basically are pass through holes for the torque tubes - it will serve its function as long as adequate clearance is provided. 

 

My eventual approach to drilling these holes adheres  to recommendations from the Cozy Girrrls and Wayne Hicks (with minor deviations) as follows:

 

The position at the firewall was straight forward - I marked it with pencil and drilled a 1/16" hole. I chose a smaller hole because I was planning to use a 26 gauge wire instead of a string. The second position was a bit difficult to pin point because it is still a point in space at this stage of my building process. In order to locate it, I cut a 4" strip of aluminum, put a L-bend to it and drilled a 1/16" hole 1 5/8" (CS118 dimension above) from the bend. I then positioned the hole at the predetermined position (above) and hot glued the aluminum tab onto the fuselage wall (picture left). I drilled a 1/8" hole at each of the bulkheads per drawing. Now I should have a total of 4 holes. 

 

 

 

I took a 26 gauge wire (red) and thread it through all 4 holes, with one end tied to the shoulder mount and the other to a weight (i.e. a c-clamp). The weight of the c-clamp pulls the wire taught through the holes. As expected, the wire zigzagged through the bulkhead holes. I marked the wire position (where it touches hole walls). Pulled the wire back out of the hole and drilled a new 1/8" hole at the newly marked location. Make sure you pull the wire out before drilling otherwise the bit will grab the wire and make a siren like squeal followed by a horrendous SNAP - all before you brain can say 'what the....'. .

 

 

 

 

 

By repeating the process above, the wire eventually will be taught, straight and free. Using the final center positions as a guide, I took a long 1/4" drill bit and drilled through the firewall and the bulkheads. I then pulled back the long bit and added the 1" hole saw and put the two holes through the bulkheads.

 

[Hindsight: I received several private E-mail later pointing it out that the hole diameter per plan is 1", but the drawing showed 3/4" and that the correct one should be 3/4" per the drawing (M-10). With the torque tube being 9/16" in diameter, leaving 3/32" tolerance for each side. I am more comfortable with a bit more tolerance because the torque tube coming long way away. So, if I run into obstruction problems, I'll have the room for it. If not, I'll slip a thin 1" OD PVC pipe inside the hole and make it pretty.]        

 

I was tempted to put the 1" hole in the firewall while I was at it, but decided to double check. I am glad I checked, its not a 1" hoIe... I decided to leave it alone for now.  

 

 

 

  LG Bulkhead Reinforcement   Preparing Strut   Attach Tab 

 

  Landing Gear Cover   Axles, Brakes & Brake Lines   Landing Brake