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Optic armor question

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Fabman

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I also drilled/rolled some aluminum Tee Bar to keep the windows contour consistent at speed. The contour of the factory glass was rounder than the plastic so this definitely made for a better fit. Maybe it's overkill, but what the hay.

42142873_10156697826743535_1656294721124827136_n.jpg
 

Fabman

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How did you brace the front?


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I didn't. I was assured by the folks at Optic Armor that unless I planned on prolonged speeds over 150 mph no bracing was needed on a 1/4" windshield.
Last year my top speed was only 145 and just at the end of the straight so unless the car gets way faster or the tracks get way longer I doubt that it will be an issue in my case.
At least that's what I'm going with until something changes...stay tuned.
 
I didn't. I was assured by the folks at Optic Armor that unless I planned on prolonged speeds over 150 mph no bracing was needed on a 1/4" windshield.
Last year I my top speed was only 145 and just at the end of the straight so unless the car gets way faster or the tracks get way longer I doubt that it will be an issue in my case.
At least that's what I'm going with until something changes...stay tuned.

Same here. Did not brace the front as I don’t hit anywhere close to 150.


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Fabman, with the way you have your rear window braced, do you expect it to bow in or out at speed?

And, are those pop rivets going through the T-bar and through the window?
 
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Fabman

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Fabman, with the way you have your rear window braced, do you expect it to bow in or out at speed?

And, are those pop rivets going through the T-bar and through the window?

SCCA mandates hold down straps on lexan rear windows, and if I was going to do it, why not do it with a little flare? Nascar has been using similar straps with a vertical on them forever, it adds strength and also helps channel air over the roof and down to the spoiler.
If you look at a cup car close, you'll notice that little fence runs all the way down the roof as well.
(at least they did when I was active, not sure what's legal these days)

So being an old Nascar guy I just kept doing what I always have. Came real close to going down the roof as well but decided against it. The holes in it are a tip of the hat to @blacksheep-1 and @Albino500 (Rob and Kevin) who are constantly reminding me to keep things light. I'm sure those 3 ounces I saved are going to make all the difference. Thanks guys. ;)

They are bolted on, not riveted. The holes are clearance drilled so there's no stress on the plastic beyond the clamping force so cracks are way less likely to form. I used 10-32 stainless steel hardware with nylock nuts so they don't need to be tightened so much to keep from coming loose. There is also a backer so they won't pull through and bolted through the window frame at top and bottom for positive retention. Don't need the window flying out at speed and taking the straps with it, that would be a bit awkward I think.
I was going to paint them black but it looked so blingy I decided to give them a nice satin aluminum finish and leave them as is. Besides, it will give Kevin something to look at as I'm pulling away. :p
 

Fabman

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Wait...I meant it will give Kevin something to look at as he's passing me....
Yeah, that's it .;)
 

Fabman

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See those black end fences on the roof leading down to the spoiler?
This car has them at the edges of the roof but back in the day we would run them closer to the center and tie them in with the window straps.

maxresdefault.jpg

A lot has changed since I was active in the 80's and 90's and the excessive compulsive part of me needed them to line up with the stripes....so, there's that.

41844777_10156689670168535_6568104700485304320_n.jpg
 

Fabman

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I thought those brackets on the roof was for the luggage[emoji3]


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Yeah, I just hook my bungie's through the holes....it really quite convenient.
 
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Fabman, nice job on the window supports, but here are a few points to ponder:

1. Rear flexible windows bow inward (into the cabin) under speed, not outward. In fact, they can bow inward up to 2" without support.
2. Rear window supports might better be placed on the inside than the outside. This way they can be smaller in cross section, reducing viewing obstruction and the outside is easier to clean.
3. With supports placed on the inside, the window will be in compression against the support rather than in tension. No hardware necessary. Easier to remove window.
4. Placed on the inside, holes do not need to be drilled through the window, reducing possible future cracking.
 

Fabman

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The reason
Fabman, nice job on the window supports, but here are a few points to ponder:

1. Rear flexible windows bow inward (into the cabin) under speed, not outward. In fact, they can bow inward up to 2" without support.
2. Rear window supports might better be placed on the inside than the outside. This way they can be smaller in cross section, reducing viewing obstruction and the outside is easier to clean.
3. With supports placed on the inside, the window will be in compression against the support rather than in tension. No hardware necessary. Easier to remove window.
4. Placed on the inside, holes do not need to be drilled through the window, reducing possible future cracking.
The reason rear window straps are mandated is to keep the window from blowing out, not in. Inside supports are often added for the very reason you stated, to keep the window from bowing in. 2 similar effects handled different ways and for different reasons.
If this was a super speedway car I would have made a big deal out of some curved flanged and dimple die'd sheet metal supports inside the car. It would have been beautiful, but at the speeds this car is likely to see and for the time I was willing to invest at the end of this project, the T bar on the outside was plenty good enough.
I ran 150 MPH in Stock cars with this exact same setup and only 1/8" flat rear windows with a fiberglass body and no problems. This all steel car with a factory molded 3/16th window is more than sufficient. And the best part is, I own the fab shop. If for some reason I decide it needs to be different, I can make it so, but for now, this is going to have to be good enough. Do a google search on rear window straps and you'll see that 90% of the images that come up are 1/8" x 1" aluminum straps on the outside of the window, often riveted right through the lexan.

https://www.google.com/search?q=rac...TQIHXz9Ct0Q9C96BAgBEBs&biw=1360&bih=626&dpr=1
 
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Fabman

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stang.PNGrvcamaroprotorear.jpg1969-porsche-911trear-window.jpg
 

Fabman

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3DLexanRearWindow.jpg
blow out straps.PNG
StormField-MGBGTV8-BK.jpgDSC003851288990958.jpg
 

Fabman

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Some more of the end fence concept...
These are speedway cars so they are braced from the inside.

nascar-cup-daytona-january-test-2014-rear-spoiler-detail.jpg
nascar-cup-watkins-glen-2004-tony-stewart-rear-window.jpg
 
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This site would not let me PM or Start Conversation (a little bit frustrating) with a member privately, so I'll drop this here:

1. Rear window straps are not mandated by SCCA for racing if window is securely bolted to the frame.
2. In some SCCA classes, like Improved Touring, polycarbonate or Lexan front windshields are not allowed.
3. ITE may have different rules than the other IT classes.

Hope this helps in prep for the upcoming season.
 

Fabman

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This site would not let me PM or Start Conversation (a little bit frustrating) with a member privately, so I'll drop this here:

1. Rear window straps are not mandated by SCCA for racing if window is securely bolted to the frame.
2. In some SCCA classes, like Improved Touring, polycarbonate or Lexan front windshields are not allowed.
3. ITE may have different rules than the other IT classes.

Hope this helps in prep for the upcoming season.

I opted not to bolt the windows to the frame. I had my glass guy flush mount them with Polyurethane. It was either 50 holes around the edges or a handful down the center so I chose the latter, hence the straps were mandatory for my application.

ITE only has 3 rules:
Stock tub cars
DOT tires
Must meet safety inspection.
That's it.
Its a real "run whatcha brung" class.

There have been some extremely fast cars in this class over the years, though we didn't see any of them last year. It will be interesting to see who shows up.
Darrel Anderson ran his carbon fiber monster Mustang to a track record of 1:29 @ Laguna Seca some years ago. No-one has come close to that since.
 
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Thanks for the reply, info, and your informative posts.
Your spectacular fabrication projects are always well thought out and don't look too bad either.
From the looks of the design of your rear window straps it seems that they can only help in the aero department.
Might be interesting to see what some attached yarn does in the slip stream coming down the straight and in the corners.
 

Fabman

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Thanks for the reply, info, and your informative posts.
Your spectacular fabrication projects are always well thought out and don't look too bad either.
From the looks of the design of your rear window straps it seems that they can only help in the aero department.
Might be interesting to see what some attached yarn does in the slip stream coming down the straight and in the corners.

Maybe I should tie wool tufts to all those holes....lol. Thanks for the compliment. :D


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