6.3.7 Install Aft Keel Section

This entry is part 31 of 42 in the series 06 - Fuselage

This is going to require some explanation. The center keel runs down the center of the fuselage on the floor. It’s about 18 inches high at the front and drops to about 6 inches tall where it stops around 6 inches forward of the gear bulkhead. At the rear, it extends left and right to the sides of the fuselage. Inside of the keel is the aileron torque tube. Moving the stick left and right rotate this tube which causes the airplane to bank left and right. The only way to install the keel in a fastbuild kit is to cut it about 75% of the way back. Here’s a picture from February 2008 where Rick was preparing to make the cut. You can barely see the red “cut” line.

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Front part of the keel after the cut.

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This part of the keel got installed when I was down in Florida. The smaller rear part is called the “Whale Tail” (you’ll see why later). So now I need to install this part of the keel. When I fitted it in position, it didn’t line up with the front part. Two possible reasons; 1) the mold used to make the keel has… warped and doesn’t conform with the floor of the fuselage anymore. Or 2), The mold to make the floor of the fuselage has warped with the same result. Or it could be a combination of the two. In order to get everything aligned, I had to remove some of the material along the bottom rear of the whale tail. The farther back, the more material I had to remove. As I moved forward, less had to be removed.

Here’s the whale tail in position (see why it’s called a whale tail?). In the bottom left corner of the picture you can just see the seam with the forward part of the keel. Where the keel meets the floor is a flange that lays on the floor. But in the back you can see where I had to remove the flange so it would sit correctly.
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The seam where the rear keel section attaches to the front.
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Where there’s a flange that contacts the floor, structural adhesive is used to bond the keel to the floor. Where I removed the flange, BID layups will be used to strength.

Here’s the left side of the whale tail where it contacts the wiring duct. You can see a bit of the gray structural adhesive used.

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Next I created a fillet of epoxy/micro and then covered the flangeless areas with 2 layers of BID front and back. Here’s the same location with the BID layups applied.

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Chicken strips
On the rear portion of the keel where I didn’t have to remove the flange and the entire front portion of the keel it’s attached to the floor with only structural adhesive.

Here’s the right side of the keel about half-way back.

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Close-up of the same area.

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Normally, in this type of joint you would reinforce it with two layers of BID. The manual doesn’t call for this, but I’m going to do it anyway. So I beveled the edge a bit, mixed up some epoxy/micro and then layed down two layers of BID. This will make it much stronger.

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