Windscreen Confusion - 1 Piece vs 4 on Prewar B

[NC26528]

A search has failed to provide a difinitive answer...

My 1940 B currently has an ill fitting 4 piece windshield but pictures of other Prewar models most often show a single piece.

Which is correct? Was the single piece an option? Are they interchangable between airframes? Does changing from one to the other constitute a modification/alteration (requiring a 337)?

Thanks much.

[3Dreaming]

Re: Windscreen Confusion - 1 Piece vs 4 on Prewar B

4 piece was original. The molded plastic was a product of WWII. If you order a 1 piece make sure you order for a pre war, because the post war doesn't fit. I think the 1 piece windshields are a FAA-PMA replacement part for the airplane. I have never heard of or seen a 337 for a replacement windshield,

[NC26528]

Re: Windscreen Confusion - 1 Piece vs 4 on Prewar B

OK, Good to know. Thanks much.

Is there a source for accurate templates for the various panels? Mine can't really be relied upon since they fit so poorly around the wing root.

[3Dreaming]

Re: Windscreen Confusion - 1 Piece vs 4 on Prewar B

I made patterns for the BL I restored out of upholsterers black panel board. You can use anything for the pattern that is stiff enough, but will still bend around a curve. They windshield is not hard to make, but you have to be careful riveting. I used 1/8" for all the panels, but if I was to do it over I would just do the front panel out of 1/8" and the other 3 out of .090. The original rivets were a soft aluminum round head rivet. We modified a rivet set to match the rivets. Mine was an open cowl, so it might be different than yours. I can check with dad to see if we still have the patterns if you would like.

[NC26528]

Re: Windscreen Confusion - 1 Piece vs 4 on Prewar B

Currently, the panels are fastened with screws and nuts. Good to know that they were riveted - that was going to be my next question. Are the rivets available currently? I know that I can find a modern functional equivalent, but was wondering what they were supposed to look like from a "correctness" (restoration) perspective.

Also, understood about making the patterns from scratch. I can handle that.

Thanks

[3Dreaming]

Re: Windscreen Confusion - 1 Piece vs 4 on Prewar B

I'll check with dad to see if we have any rivets left. I know we have sent some out to others who were doing 4 piece windshields.

[Hank Jarrett]

Re: Windscreen Confusion - 1 Piece vs 4 on Prewar B

If you use screws and nuts be very careful to NOT allow the threads to contact the hole IDs. The threads will put stress risers in the bores of the holes that will start cracks. I used small screws and nuts on my 4 piece and put small pieces of Silicone tube around each screw inside the holes to allow the Plexi to "float" and prevent contact with the bores of the holes.

If you use rivets, practice on scrap Plexi because the rivets can also crack the panel and there are a LOT of rivets! You also need a REALLY LONG throat rivet squeezer! Bucking the rivets by hand will require a better touch than anyone I know has. Even the old factory photos show a deep throat rivet squeezer. Also be prepared to make extra side wind screens (windSHIELD is the front piece, the side ones are usually called windSCREENS, never heard the correct term for the top piece). I split 5 or 6 windscreens when I was putting mine in. ANY small nick or scratch in the edges of a windscreen will cause it to crack when bent. You will need to gently heat the Plexi as you GENTLY pull it around. I did it with a tile gun (held fairly far away to keep from getting bubbles in the Plexi) on a high 90s summer day in a VERY HOT hangar. I still came back to broken side windscreens the next morning. The last ones were GENTLY pulled to shape over a couple of days while left in a VERY hot hangar. You will need to apply quite a bit of heat to the top edge where it comes up to the wing LE to get it to seal fairly well. I have a few tiny bubbles there but they are covered by the wing strip.

I would use screws at least until I had all the pieces made and fitted. Bad enough to have to do all those rivets, WORSE to have to drill them out and start over when a windscreen cracks!


Hank