7.4.3 Transverse Bulkhead Installation

This entry is part 26 of 39 in the series 07 - Landing Gear

After spending the last two weeks on the road, I didn’t get much building done. I did get some building related work done. Malcolm Collier of Hangar 18 fame is a professional builder who works with builders that don’t have much available time to build. His work is some of the finest and he has made some impressive innovations to the Velocity design. So after class was done on Friday, I flew over to Greenville, SC and hung out with Malcolm. I got some good ideas and some great tips. Then I had to spend the next week in New York City.

Once I got back from NYC, I resumed building. One of my tasks was getting the main gear positioned and aligned so I could permanently install the pivot bushings. Now consider that this airplane (when taking off and landing) is going to be moving down a runway at about 70 MPH. So the wheels should be in exactly the right location. Here’s another situation where the manual doesn’t go into a lot of detail.

The gear legs should be symmetrical and a line between the wheels should be perpendicular to the longitudinal axis. But how to determine that?

Here’s what I did. First, I leveled the plane front the rear and side to side. Then using a plumb-bob, I marked the centerline of the plane at the front and rear on the floor and drew a line between the two points. So now there’s a line on the floor from the front to the rear of the fuselage.

The vertical line to the centerline.

2008-05-12 1929 IMG_6897

Next I ran a string from one of the wheel mounting holes on the right gear leg to the corresponding hole on the left gear leg. The I measured the distance between the two gear legs and put a mark on the string at the halfway point.

Then, using the plumb-bob from the mark, I adjusted the gear legs until the mark on the string was in the middle.

2008-05-12 1930 IMG_6898

  I actually put two marks on the string so I could easily see when the plumb-bob string was in the middle.

And here’s the plumb-bob on the floor. Dead-solid-perfect.

 2008-05-12 1930 IMG_6899

Next I had to get the gear legs positioned front to rear. For that, I used a laser. I pointed the laser through one of the wheel mounting holes on the gear leg so that it went through the same hole on the other leg.

From the right side, you can see some of the light from the laser on the bottom left hole.

 2008-05-12 1932 IMG_6901

 Then, I moved the the plumb-bob until it was hit by the laser.

Here’s the laser hitting the plumb-bob line.

 2008-05-12 1932 IMG_6902

I then put a mark on the floor. I did this at a couple locations between the gear legs. Next I drew a line connecting the dots.

 2008-05-12 1933 IMG_6903

Checking the location of the line just to make sure nothing changed.

Finally, I just had to check that the centerline and the line between the gear legs was perpendicular and adjust if necessary.

Now the whole operation start to finish was about an hour but I must have spent half the day figuring out how to do it in the first place.

Next, I had to install and reinforce the transverse bulkhead. This relatively small piece connects the firewall to the main gear bulkhead. The plans call for the piece made to made from foam and covered with two layers of triax. I felt that using some plywood wouldn’t add much weight and would add strength. To determine the correct size, I used cardboard and trimmed it until it fit. Then I transferred the shape to a piece of plywood.

Plywood transverse bulkhead

 2008-05-15 1451 IMG_6915

Then I had to determine the shape of the triax fiberglass that would cover it. I used small pieces of posterboard and taped them together.

 This is the outside triax template.

 2008-05-15 1844 IMG_6917

Here’s the outside view of the transverse bulkhead with the layup in place.

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Inside view on the transverse bulkhead.

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