mini windows/air vents

[Sam Rutherford]

I (and I suppose everyone) has the little circular air vents in their windows.

They are USD60 from Maule, and I have ordered a couple to install in the rear window of my airplane. I figure one near the knees of my rear portside passenger 'scooping' air in, and a second right at the back (and high) 'drawing' air out will really get a nice airflow through the cabin.

My tech, though, has the heebie-jeebies (sp?!) about trying to put a large hole, and a screw hole, in that big piece of perspex.

Has anyone tried installing these, any advice or is the best advice to leave well alone?!

Thanks, Sam.

[aero101]

When drilling use plastic - lexan - plexiglass drill bits which have a different cutting tip then regular drill bit and back up with a peice of wood. Bits can be purchased here - http://www.eplastics.com/Plastic/Plastic_Drill_Bits
or at any well equipped glass / plastics store. For cutting large hole, I usually drill a small hole first, take a small pin router to bring to near final size, and finish with a small 1"-1 1/2" drum sander in a high speed motor... If the window is real old it will be somewhat brittle and easy to crack, biggest thing is take your time and don't force any of the tooling to cut quicker then it wants to? Another way to drill the initial hole is to grind a sharp point on the shank end of drill bit of size you want hole, heat the bit with a propane torch till hot enough to melt the glass, and melt thru as required. I would also suggest that you want the hole just a little larger then the screw to allow for expansion / contraction to keep from cracking later...

[aussieaviator]

If you can't obtain the correct drill bits for drilling acrylic sheet (Perspex) you can learn how to sharpen ordinary drill bits here http://www.plasticsmag.com/features.asp ... Sep/Oct-01