Picture courtesy of Kevin Seuferer
Now for the front edge of the cover and how to integrate it into the filter bracket in a pleasing way, that still allows for engine movement of the filter bracket without it hitting the cover.
I see a lot people are just bending it into a square box at the front, with
a square hole in it to allow air to come through. But looking at pictures
of Colin Campbell's Bearhawk, I saw something that I really liked. The
front edges of the tunnel curve back toward the filter bracket and leave
a small gap which is filled with a strip of rubber sheet. Here is a picture
of Colin Campbell's air intake:
Picture courtesy of Kevin Seuferer
A piece of 5/8" tubing was clamped in the bench vise to use to shape the
front flanges of the cover. A line was drawn where the curve needed
to be and aligned with the filter bracket. The piece was then bent
around the tube as shown here:
Being careful to make the bend right on the center of the line, the front
flange of the cover was wrapped around the tube. Now you know why I
chose the soft 5052 aluminum for this part of the project. The front of the
cover now looked like this:
Of course the flange is a bit too long at this point and was trimmed to allow
the side cover to fit back in place and still clear the filter bracket.
Here is a picture of the sides of the cover, after making the curved flanges
at the front:
The bottom piece of the cover hasn't been installed yet so the sides are
not in their final position and are tilted in slightly at the bottom. With
the bottom in place, they will square up and align with the filter bracket.
Next the bottom of the cover was made. The front edge will be curled back like the sides. There was a bit of a challenge at the back edge of the bottom cover. It has to integrate with the rounded flange that we installed at the aft end of the cowl.
To accomplish this, the aft end of the cover bottom piece was cut rounded,
to fit the curve of the flange at the aft end of the cowl. Then using
the same set up Mickey used to make the rounded flange, a lip was bent on
the aft end of the bottom cover, at the correct angle as shown here:
Once we had a good fit at the aft end of the cover bottom, the front lip
was bent around the 5/8" tube to form a curved lip, just like the two sides
have. Here is the cover at this point with the bottom piece
installed:
You can see how the cover integrates with the lip at the aft end of the cowl
bottom, leaving about 1" of the lip exposed.
At the front of the cover, the fit between the bottom cover and the sides involved some patience and finessing. Trim a little, check the fit, trim a little, check the fit, repeatedly until the fit was just right.
One hint: To get a good fit on the rounded front curves, start with the side pieces cutting them to 45 degree angles. Then keep adjusting the bottom piece until it fits to the side pieces. Take your time and you will get a nice fit.
The last part of the cover is the top edge of the filter bracket. Colin left
his plain and it looks fine but I wanted to have another piece in there to
detail it out. This piece was a little different and we ended
up making a "Z" shaped bracket with a rounded contour. This took some
trial and error and we ended up making two of them before we got one that
fit correctly.
As you can see, the flange for this top piece comes out in front so we could
attach it to the cowl easier and it creates a nice smooth airflow into the
filter bracket.
Click here to go to Engine Cowl page 6