BC12-D Windshield Replacement

[bladd]

My A&P says that my old 1946 BC12-D windshield needs to be replaced. I ordered a new one from Univair that was made by L.P. Aero Plastics in PA. The new one came without air vent holes like my old one had on the sides of the windshield. When I quieried Aero Plastics about it they said the origional windshields did not have air vents and to have them added would require a 337. Are these statements true? The air vents are nice but if they are a hassle in paperwork or if they are not origional I could do something else.

If anyone has replaced their windshield I would appreciate knowing what the tricks are and the tools needed to install one properly before I launch into this project. Does the windshield require drilling for attachment and do I need special acrylic drill bits like L.P. Aero Plastics recommends? How have you fitted and trimmed the excess plastic from the new windshield? Any help or advice would be appreciated. Thanks. Bob Ladd

[jgerard]

I would put the vents in the side windows or the boot cowl. The side windows are the least expensive to replace if you end up cracking the plastic while cutting it.

Jason
N43643

[Robert Lees]

Bob:

Your A&P is correct, the vents are not original.

Fitting a new windscreen requires patience (you have to fit and re-fit it many times, each time trimming a bit off to fit around the cowl, the side pillars and the top). Trimming is best done with a Dremel or VERY fine saw blade, with the final edges of all sawn and drilled holes heat-sealed with a little flame from one of those gas soldering guns. And the holes do need to be slightly oversize.

And make sure it is all kept warm; if you do the job in the winter, the cold will cause cracking.

Yes, you do need to drill holes, but you can modify some standard drill bite yourself, I will dig out the info, else you can indeed buy the "proper" bits from the supplier.

Use your old one as a rough pattern.

Hope this helps, I will try to dig out the drill bit info tomorrow.

Rob

[paulnuss]

It has been said, but I'd like to stress, at the risk of repeating, do NOT use standard twist drill bits, warm weather or cold! They are cut to pull themselves into the drilled hole, and can and will crack the plexiglass. I used to grind away the undercut of the drill tip's flutes, so that it only was "scraping" its way through, not cutting into the material; this is no problem, as the plexiglass heats up with the friction (good), and it easily soon scrapes through. The rest of the advice is good, that is to use the old windshield as a guide to make a template, and a Dremel-type tool works well for cutting to size. Cut oversize, and slowly work towards final dimension, cutting and fitting as you go.

P.S.: I have made all of the mistakes at one point or another, and so can speak from sad experience.

[bladd]

Thank you for the advice. I will abandon the idea of windshield/screen vents and just install it as the original was. I'll do a bit more research and assemble the tools I need but, what is a Dremel? I farm so I am reasonably familiar with tools but that one is new to me.

Behind the windshield are little red rubber bumpers that support the windshield from tabs welded to the front cabin supports. The rubber is old, cracked, and probably needs to be replaced too. Do you have suggestions for what to use for these rubber supports? The farm store has clear plastic hose that looks to be about the right diameter but I'm sure that was not original issue and might not be appropriate. Thanks, Bob

[CraigH]

Originally posted by bladd
. . . what is a Dremel? I farm so I am reasonably familiar with tools but that one is new to me.

Read all about it: http://www.dremel.com/html/home_fr.html

[Robert Lees]

Page 1 of plexiglass bumph...

[Robert Lees]

...and page 2.

Or go to www.taylorcraft.org.uk/plexiglass5.jpg (131 Kbytes) for a single-view version of the same.

[Robert Lees]

Here's what the drill bits look like. The changes to the cutting edge profile causes the bit to scrape the plexiglass away, rather than cutting into it. Test on a scrap piece first.

Rob

[CraigH]

Dremmel tool works great for trimming your dog's toenails as well.