Wireless Internet Cantenna

Step 5 Lengthy Layout For A Thumb-Hole

Still using that same calculator, now I have a better measurement of the inside diameter: 3.16 inches approximately.

This gives an upper and lower frequency range that looks good. The full wave length is 11.07 inches, 3/4 wave is 8.3. I decided to leave the length alone

The 1/4 wave measure of 2.77 inches, is where I want to position the thumb-fi, and I reasoned that this is probably the center of the thumb-fi

First, another standard layout trick. Using any nice length of angle stock will allow a method to draw lines perfectly along the length of tube or pipe. In this case, I'm using that funny ruler. Laying it along the length of the extinguisher, near the rear end, it fit's automatically and I use that to draw a starting line. Doesn't matter too much where as long as it goes through the likely placement of the hole, but it will help if the line ends right at the bottom of the extinguisher, because I'm going to eyeball the next lines position based on the first one

To find where to put the second line, I rested the thumb-fi on the bottom of the extinguisher so that it lined up with the line I had drawn. Then I placed the ruler so it lined up on the other side of the thumb-fi. Carefully holding the ruler so it wouldn't budge, I just let the thumb-fi fall onto the work bench and proceeded to draw the second line along the length of the extinguisher

These two lines give two sides of the hole that will be cut. The quarter wave dimension will now be used to find the other two sides. I fudged this step, I made a reasonable guess where the bottom of the inside of the extinguisher would be. So, with the ruler laid along the length of the extinguisher, I slid it down to the bottom and lined up the zero with where I thought the inside bottom might be, then made a mark at 2.77 inches up. This is going to be between the last two sides I will be marking out, now I need to know how thick the thumb-fi is

Another bit of eye-balling here, as I just placed the thumb-fi on the ruler and slid it down untill one edge looked lined up with zero, then looked down the other edge to find it's approximate width. Slightly over 1/2 inch

Now, placing the ruler back on the extinguisher, and putting one edge of the ruler on that 2.77 inch mark, I slid the ruler along that mark untill the number one mark on the ruler lined up with the 2.77 mark on the extinguisher. Now I just go a 1/4 inch to either side and there's my last two sides, almost. One last time with that paper wrapped around the extinguisher, lined up with each of those last two marks. Now the last of the sides are drawn. I expect to have to use some filing to finish the hole, and I was right as we'll see next....