cutting into windshield

[tx_swordguy]

I have an A model sonex. At the midwest flyin in Fayetteville I saw one of the sonex with some snap cap vents in the windshield (not the canopy) down in the corner and out of the way. I went ahead and bought some as the installation seems straight forward enough. I have gotten a little concerned about how to cut through the windshield. Directions say use a 2" hole saw and cut slowly from both directions (directions say for either metal or windscreen). I am a bit concerned as I have never cut into lexan of that thickness. My concern is that the windshield is being held in tension. Is there a trick to this other than just go for it but go slowly? I cannot hit all of the windshield at once and at the same depth because of the curve, so I will be cutting certain areas faster/deeper than other areas before cutting all the way through. Also I cannot reach it from the inside. My plan was to put painters tape inside and out and cut through that as a way to help hold the lexan together, then sand the inside smooth prior to installing the vents. Am considering waiting until after OSH to do this although it would be nice to have more air going up there. It would suck to crack the windshield just prior to leaving and that be the reason for not going.

[wlarson861]

I have installed 2 snap vents in each of two windscreens, both were already installed on the plane. I used a 2 inch hole saw and slow speed drill. Because of the glare shield I could only cut from the outside. All four holes came out fine. Just dont have a lot of pressure on the drill as it cuts especially as it cut through to the inside. Be sure to sand the opening to get all the burrs and scratches out.

[WaiexN143NM]

Mark,
Concur with Bill, go slow , could only cut from outside, lay a towel inside to catch shavings. blue tape inside is good too. and yes sand the cut edge smooth. you’ll like the vents!

WaiexN143NM
Michael

[Gordon]

Cutting those holes...….

Mark......I would strongly suggest you take the windscreen out of the airplane...…...lay it flat on the table and use "hole saw". With the windscreen still installed there is a "tension" induced into the Lexan that you want to get rid of...….by laying it out flat on the bench.

I cut the 4 inch "fuel filler" hole in my Onex that way and it was an easy and effective way to do it. Be sure to do a real good job of "edge finishing" that hole afterwards.
And this way you don't have to worry about getting all the chips and dust on the glareshield.

Gordon...…...Hummel 2400......Onex

[DCASonex]

Lexan is no where new as prone to cracking as Plexiglass. However, take care to insure that tools are absolutely clean of any oils or other chemicals as those will make Lexan crack. If really worried about cracking it while drilling in place, consider removing it for drilling. That will allow cleaning up edges of holes before it is again stressed into a curve.

David A.