AFT window installation when delaying attaching the tailcone

[Brett H]

One question about fitting the Aft Window.

Page 25A-03, revision # 1 step 1 and 2 describes attaching the Aft Window to the Roll Bar Frames. In particular, that one is drill # 40, followed by final-drill # 36 and then tap 6-32.

Since section 5 says that the plexiglass should not be drilled or the holes enlarged with a twist drill, what are people using to drill and final-drill these holes?

Thanks.

Brett H
Columbus, IN

[DaveWelch]

Hi Brett,
Working from memory here, the Instructions called out a fractional sized Plexiglass bit for the canopy. The plexi bits have a different shape that is less likely to “dive” eagerly into your canopy only to bind up and fracture it (the canopy). Find, order, or borrow the correct sized plexiglass bit if at all possible.
Now, for the drill and final drilling then tapping you mentioned, I think that refers to drilling the roll bar, NOT the canopy. I could be wrong, but recommend you re-read the instructions carefully.
All the best for the new year,
Dave.

[tomkk]

Don't remember the size (#27 seems to ring a bell) but all my drilling in Plexiglas was with a special Plexiglas drill.

[RFSchaller]

I used commercial drill bits and picked one that made a hole that allowed the machine screw to turn freely (no stress on the plex from an interference fit). The biggest thing to prevent plex cracking is make sure it’s warm. I recall drilling a smaller pilot hole before final drill to size.

[Brett H]

Thanks for the responses.

Let me refine my question.

Regarding drilling with a # 40 drill followed by final-drilling with # 36 drill before tapping. I can not find # 40 plastic or diamond drill. The smallest plastic drill that I can find is a # 30.

So, are people just using a twist drill and making sure that the plastic is warm?

For the final-drill of # 36 I can get a reamer.

Thanks.

Brett H
Columbus, IN

[AeroDog]

Looking at 25A-03, it appears that both the plexi and the underlying aluminum structure are being drilled in the same operation. Possibly I'm reading this wrong. Can aluminum be drilled with a plexi bit?

Jerre

[daveyator]

The plexi bit will continue through the roll bar material with no problem. A recommendation here is to drill both the window and the roll bar to the tapping size first. Then the plexiglass can serve as a tapping guide to ensure the holes are nice and square to the roll bar. Disassemble,then do the final drilling of the holes in the window with the larger bit.
You don't really need the precision of a number drill here. A little bit oversized is better. My tool kit came with plexi bits in 1/8 and 5/32. These worked for me.
Cheers,
DaveH. 120485