Windshield replacement

[snellbob]

Installing a new Great Lakes Aero windshield. Still going back to “old school” by utilizing original center strip. Both pieces of center strip (in and out) have 1/4” hole size. The 4 screws that go thru the windshield are 3/16”. The holes in the last windshield were 3/16”. Two of the four holes were cracked in the old one. Getting ready to drill the 4 holes thru the new windshield for the center strip with the correct bits for plexi. I cannot find a spec for the hole size but thinking they should be 1/4” so there is room for float. I’ve read thru just about every post related to windshield on the forum and have not found anything related to size.
Does anyone have any data or suggestions for hole size?

[c170b53]

Not sure about drilling the windshield, I think there’s supposed to be felt under the strips and countersunk washers to allow some float like these https://www.aircraftspruce.ca/catalog/h ... kkey=10087 and thus the reason why the outer strip has larger holes.

[c170b53]

I’ll check the inner strip tomorrow at my hanger and verify the hole size as its been more than 15 years since I removed it, know its thicker (B model) and I thought it had acorn nuts on the inside, size escaping me.

[n2582d]

The holes on my inner center strip are 3/16". On the outer strip they have been elongated but appear also to have originally been 3/16". AC 43.13-1B, paragraph 3-27 (f) says, "In installations involving bolts or rivets, make the holes through the plastic oversize by 1/8-inch diameter and center so that the plastic will not bind or crack at the edge of the holes. The use of slotted holes is also recommended." They also suggest using a Unibit to drill through acyrlic. On their website, LP Aero says, "DO drill oversize holes. Acrylic will expand and contract at different rates than the airframe, so oversize fastener holes are required to allow for movement. The general rule is drill a hole at least one and one-third the diameter of the fastener." The other thing that's critical in avoiding cracking is not to over-torque the bolts used to attach the center strip. AC 43-13.1B states, "Tighten each nut to a firm fit, then back the nut off one full turn (until they are snug and can still be rotated with the fingers)."

[johneeb]

Great stuff Gary, thanks for posting

[dstates]

Snellbob,

I just recently removed my window with a center strip. I’ll try to measure the hole size in the removed window.

I also have all new hardware for the center strip listed for sale in the trademart section. I originally planned to put an original window back in but ended up going with an STC that didn’t use the center strip. Let me know if you want the hardware.

Doug

[snellbob]

Thx for the info. Already have all the hardware so I’ll pass but good to know another source.
I’ll most likely upsize center holes.
Bob