Surface of the Bell Mouth

Dear Fellow Basement Scientists,

I am sorry, but of late I have been absent. This is due to what is commonly known as moving. It was a lot of work, but now we are back.

For those concerned, I did move the wind tunnel! It required care and thought of how to pack it, but it is here and in its new location.  With honesty in mind, I must admit that it is no longer in a basement. Hmm, what to do? Should I relocate to a living quarters with a basement? Should I stop investigating because I no longer have a basement to conduct it? No! I shall make do with what I have and continue in the spirit of basement science! Our name shall remain because the spirit endures. Just because our laboratory is now above ground does not change our goals or opportunities. Thanks be to God. Let’s begin again.

Were where we? Oh yes, the bell mouth of our wind tunnel. We constructed the ribs of the bell mouth oh so carefully and may now attach the surfaces. For the surface we have already purchased the aluminum flashing and I also acquired sheet metal screws. This procedure is a little more complicated, so I will do my best to make it digestible.

Here is the procedure overview. We are going to take sheets of the flashing, bend them across the ribs, and screw them in. Each side of the bell mouth will have two sheets of the flashing with the first flush with the tunnel and the second flush with the end of the ribs. We will then use duct tape and caulking to fill in any gaps. Wow, that was super easy!

That was the overview, let me provide of few more details for the interested. Starting with the top side and with the sheet flush with the tunnel, measure how long a sheet is required to exceed the right and left ribs at the longest point. Cut a piece of flashing a little longer than this length. I found the best way to cut flashing is to make a small cut with wire cutters and tear the rest by hand. Hold this piece in place and mark the location of the ribs on the flashing. Then make holes in the flashing for the screws at these locations. I made these holes by pounding a large wood screw into the flashing with a hammer.

Hole making

Put the flashing back in place and make sure the holes line up with the ribs, then drill some tap holes into the ribs and screw it all in place. What fun! I did have quite some trouble getting the holes to all line up. When they didn’t line up it created annoying ripples in the aluminum. Therefore, it’s better to make the holes too big than too small. The aluminum is not going to experience huge amounts of force so they don’t need to be bolted down like a nuclear reactor lid. Do the same process for the second sheet and we have something fun to look at because it is starting to come together.

Now, take anything long and skinny, like a dowel rod, and place it across the side ribs. Pull it along the flashing we just installed while marking with a sharpie where they touch. Cut along this line. The idea here is to figure out where the two sides of the bell mouth would intersect and cut one to get it out of the way.  I used my Dremel to do this which made a lot of painful noise but worked just fine. If you are going to err, cut off too much. This is because any gaps can be filled with caulk and any overlap in flashing will cause more weird ripples in their shape. We now have one side totally done.

Do the same measuring, cutting, hole forming, drilling and screwing for the right and left sides. With their top ends, you don’t need to worry about cutting them to shape because cutting the top side to shape took care of that. However, make your line and cut on the bottom end. Below you can see the top and left side done with the top cut to shape.

Top and Left side installed

Lastly, measure, cut, hole form, drill and screw the bottom in. Ta Da! For me that was a lot of work, doing and often redoing some of these parts. I learned the hard way to cut off more than necessary at the intersections. I started with cutting off to little, resulting in many weird ripples.

To finish, we need to fill in the gaps. I took the cheap and easy route of covering the gap between the two sheets with duct tape. For the adventurous, you could cut a small sheet of flashing to fill this gap, but I was growing impatient with the flashing and duct tape seems to work well enough. Finally, calk the intersections and you are set!

A marvelous use of duct tape

Learning how to caulk



Learn as we go and do our best.
That is how we finish our quest!

Best Regards,
Ben Washington

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