Page updated on: February 27, 2008
March 5, 2008
March 9, 2008
April 6, 2008

Chapter 9 - Main Landing Gear and Landing Brake

Chapter Overview

In this chapter I will install the main landing gear and landing brake. I will start by adding reinforcing layups to the landing gear bulkheads and firewall, trim the main gear strut to length, sand it dull, and then layup 8 plies of UND at 35 degrees over the entire strut for torsional stiffness. I will install a conduit for the brake lines and feather the trailing edge for minimum drag. I will jig the strut into position on the fuselage, make the attachment glass tab layups, and assemble the gear on the fuselage. With the strut installed, the axles are mounted. The landing gear cover is also built at this time.

The main gear strut was especially designed for the Cozy. It is a one piece, 30 lb., airfoil shaped, S-glass molded part, available from Featherlite.

Finally, the landing brake will be cut out from the bottom of the fuselage and installed. Once installed, it will then be fiberglassed. I also plan to install the electric landing brake actuator.

Whew! there is a lot to be done in this chapter. I guess I better get started!

Step 1 - Landing Gear Bulkhead Reinforcements

This was a step I was not looking forward to. It is a series of difficult layups in hard to reach places. The first layup was on the forward landing gear bulkhead to the floor of the fuselage. The second layup was between the two landing gear bulkheads. The third layup was between the aft landing gear bulkhead an the firewall.

Before starting the layup, the "bump" caused by the lower longeron doubler needs to sanded down so the fiberglass will smoothly transition from the longeron to the floor of the fuselage. The "bump" is actually more than a bump. It was a bit confusing to me as to what was meant. Therefore, I have taken several photos showing the before and after shots of the "bump".

View of the "bump".

Close-up of the "bump".

The "bump" has been sanded to shape.

A smooth transition of the longeron to the floor of the fuselage

A side view of the smooth transition of the "bump".

These layups took around 4 or 5 hours each. Before each layup, a template had to be made of the area to be fiberglassed. To make it easier for you, I took pictures of the templates I made. I also measured each template and placed X and Y coordinates for each transition point. This should allow you to duplicate my template and use it on your plane. My hope is that it will save you about 4 or 5 hours by having a starting point for your templates.

The X coordinate is shown in the traditional negative direction, but I have redefined it as a positive direction!!! Although it really shouldn't matter as you'll just get a mirror image of my template if you don't follow my "rule". The reason it doesn't matter is you will use one side of template for one side of the fuselage and then you'll flip it over to use on the other side.

The lines with arrows on each end show the BID orientation of the template. The lines with single arrows on them show the "X & Y" coordinate directions.

I like to make templates from posterboard. It is thicker than normal paper and can be easily moved around on the fiberglass to determine the best layout to minimize the amount of fiberglass used. Once a suitable positioning is found, it is easy to trace out the template using a felt tipped pen. The posterboard may be purchased at WalMart or art supply stores for about 50 cents for each 2 x 3 foot sheet.

Please let me know if you find the templates useful.

BID fiberglass template for the first part of the layup which goes from the forward landing gear bulkhead to the floor of the fuselage.

This template may be used on for both sides of the fuselage, however, each side is an opposite (i.e. use one side of the template for one side of the fuselage and the other side of the template for the other side of the fuselage).

The top of the template goes at the top of the forward landing gear bulkhead and the notch goes into the corner where the forward landing gear bulkhead, the fuselage side and the fuselage bottom all meet. The left side of the template is in the center of the fuselage and the right side goes along the side of the fuselage.

Template for the second part of the first layup.

An overall view of the location for the first layout. The template shown above would be for the left side of this photo (right side of the fuselage).

Close-up view of the first layout.

Template for the first part of the second layup.

The triangular notch in this template is for the corner where the vertical portion of the forward landing gear bulkhead, fuselage side and and the angled portion of the forward landing gear bulkhead all meet. The notch in the lower left side of the photo is for where the NACA scoop meets the aft landing gear bulkhead. The curved part at the bottom of the photo lays along the triangular pieces of plywood on the side at the bottom of the fuselage.

The template, as shown, is for the left hand side of the fuselage. Flip it over for the right hand side.

Template for the second part of the second lay-up.

View of the second layup.

Close-up of the second layup.

Template for the first part of the third layup

This layup goes from the aft landing gear bulkhead along the fuselage side and then wraps onto the firewall.

The left side of the template goes along the aft landing gear bulkhead. The middle of the template goes against the fuselage side. The right side of the template lays against the firewall. The tab at the bottom lays on the plywood on the bottom of the well formed between the landing gear bulkhead and the firewall.

The template as shown is for the right side of the fuselage.

This is the template for the second part of the third layup. It goes down the aft landing gear bulkhead, over the plywood on the bottom and then up the firewall.

Overview of the third layup.

Closeup of the third layup.

Step 2 - Preparing the Landing Gear Strut for Installation

Multiple layups are done to provide additional resistance to twisting.

One concern I had was the amount of twist in the strut. When I received it, it would not lay flat on my workbench. You can see what I mean in the pictures below. I queried the Cozy Builders mailing list about it. Of the many responses I received, all except for one, said it was not a problem. Several builders even said their strut was also twisted. I now feel much more confident to forge ahead.

The leading edge of the strut is in contact with the workbench. A yellow piece of paper board was placed behind the strut to highlight the gap between the table and the strut.

Close-up of gap between the table and one side of the strut.

Close-up of the gap between the table and the other side of the strut.

The leading edge of the strut is the upper surface. Again, a yellow piece of paper board was used to the highlight the gap between the table and the strut.

This side of the strut is in contact with the workbench.

The other side of the strut showing the gap between the table and the strut.

Attaching the McDonald's straws to the trailing edge of the strut.

Left side of the strut with the McDonald's straws.

Right side of the strut with the McDonald straws.

Jeff is attaching the aluminum tape to the trailing edge over the straws.

Close-up of Jeff attaching the aluminum tape to the trailing edge over the straws.

Neil and I have just completed the second, four-ply layup of UND on the strut.

For this picture, the table has been leveled, however, the right side of the strut is above the the table.

Close-up of the right side showing it is about 1.2 inches above the table. The left side is in contact with the table.

Step 3 - Making the Attach Tabs and Installing the Landing Gear Strut

In this step, the attach tabs are added to the gear strut. The attach tabs will have bolts going through them to connect the strut to the fuselage.

Accuracy is very important as the fit is very tight. There is a lot of measuring and jig building to insure a proper fit.

A piece of plywood is attached to the end of the workbench. Many of the measurements are first made on the plywood, then transferred to the jig box to be built on top of the strut or to the workbench where the layups will be made.

It is important the bottom of each leg of the strut be level with each other. Since the floor in my work shop is not level, I had to place a 1/2 inch block under the left leg to make the two legs level with each other.

To check if the two legs are level, straight piece of wood was placed between the two legs.

This is a close up view showing the left level point is 1/2 of the thickness of the strut. You can also see the digital level shows the ends of the two legs are level with each other.

When the legs of the strut are placed 9.25 inches forward of the plywood, the left top edge of the strut is not in contact with the plywood. This is caused by a twist in the strut.

Here is a close-up view of the left side of the gap. The gap is 0.5 inches. The scale appears to show 0.6 inches, but this is due to parallax.

The closest the strut gets to the plywood on the left side is 0.3 inches, even though the scale shows 0.4 inches. Again, it is a parallax problem with the camera.

To correct the problem of the twisted gear, I took the advice of Ron Springer. According to the plans, the legs are to be placed 9.25 inches forward of the plywood. With my gear strut, when I did this, there was a huge gap on the left side between the top of the strut and the plywood. To reduce this, I placed one gear leg in front of the 9.25 inch reference line and the other behind it. The legs were placed an equal distance in front of and behind the line. When I did this, the top of the gear was very close to the plywood on the left side and touching on the right side, as shown in the above photo.