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Living with a Lexan Sunroof by retroman
Started on: 10-19-2013 05:07 PM
Replies: 13 (1136 views)
Last post by: retroman on 05-23-2014 10:40 PM
retroman
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Report this Post10-19-2013 05:07 PM Click Here to See the Profile for retromanClick Here to Email retromanSend a Private Message to retromanEdit/Delete MessageReply w/QuoteDirect Link to This Post
Ok, it's been awhile since I last reported on this, but I did get my sunroof, and now it's time to see how it performs against the OEM glass one. Some of you may remember my last thread I had in the Mall on the subject here: http://www.fiero.nl/forum/Forum4/HTML/066582.html

First off, I should note that there are a few things I have to do to make this a completely fair comparison. My old sunroof weatherstripping is shot so I will be replacing that soon. I also need to finish a 3.4L swap so I won't be able to do a road test right away. That said here's what I do have. Proglass did a really good job with the forming, and the contours were matched perfectly with the glass roof. As mentioned in the other thread, Lexan is flexible so it will be interesting to see if it maintains a weather tight seal with road vibration and chassis flex. It also might droop slightly when in the up position. Now onto the weight aspect. I tried to be as accurate as possible by weighing both sunroofs a minimum of 5 times each, but I was using bathroom scales instead of more precise industrial or commercial scales and I weighed the roofs on the edge so I had to use light finger pressure to keep them stable so I could weigh and still be able to read the scales. Because of that, results may differ slightly if anyone else tries this with more suitable equipment. I also used two different scales as the Lexan roof would not register the digital scale so I hope to re-weigh the glass roof on the mechanical scale to remove the variable of error that comes with using two completely different instruments. Ok, now the results. According to my measurements the glass roof weighs ~ 15.2 lbs (four times it registered that with the fifth showing 15.4 lbs). The Lexan roof weighed in at just 5.25 lbs with a +/- .25 lb margin of error. That's 10 lbs difference!! It might not sound like much, but if I were building an autocross car, I would want to squeeze as much weight out as I could to be the lightest Fiero on the track. It adds up especially if you replace all the other glass with Lexan. Anyway, here are the photos from my experiment:

GLASS ROOF:



LEXAN ROOF:





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Report this Post10-19-2013 05:14 PM Click Here to See the Profile for IMSA GTClick Here to Email IMSA GTSend a Private Message to IMSA GTEdit/Delete MessageReply w/QuoteDirect Link to This Post
I remember your thread on this. My only concern was not the drooping when open but when you latch the sunroof, will there be too much tension from the handle pulling down on the sunroof that the sunroof could be pulled concave or buckle right at the handle?
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retroman
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Report this Post10-19-2013 05:27 PM Click Here to See the Profile for retromanClick Here to Email retromanSend a Private Message to retromanEdit/Delete MessageReply w/QuoteDirect Link to This Post
Sorry about the orientation on some of the pics. Apparently, photobucket didn't save my editing. Anyway, for my next post I hope to post acurrate measurements about the thickness of the roofs since the old thread had showed some concern that the thickness between the Lexan roof and the glass roof would not be the same.

 
quote
Originally posted by IMSA GT:

I remember your thread on this. My only concern was not the drooping when open but when you latch the sunroof, will there be too much tension from the handle pulling down on the sunroof that the sunroof could be pulled concave or buckle right at the handle?


^ That is something that I will be looking for during my experiments. I remember early Shelby Mustangs had a similar problem with their fiberglass hoods. Because Shelby did not change the tension on the hood springs to account for the lighter load, they would warp, but it would take a few years to do so. If the roof does warp from the handle pulling down on it, then I could find another way to keep it latched or ditch the project and save myself and possibly someone else the trouble. Either way, I'd still say it was worth the money to experiment.
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JohnWPB
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Report this Post10-20-2013 06:32 AM Click Here to See the Profile for JohnWPBClick Here to visit JohnWPB's HomePageSend a Private Message to JohnWPBEdit/Delete MessageReply w/QuoteDirect Link to This Post
Just a note... You can weigh the glass sunroof on the digital scale, then add the lexan one. Then just subtract the weight of the glass one to get the lexan weight. This way you are using the same scale, so no variances. Also the digital will probably be more accurate than the analog one.
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Jefrysuko
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Report this Post10-21-2013 12:43 AM Click Here to See the Profile for JefrysukoSend a Private Message to JefrysukoEdit/Delete MessageReply w/QuoteDirect Link to This Post
Glad to see that you got it. Looking forward to seeing how it does for you. What's the clarity like? Looks like it might have a protective film on it right now?
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Report this Post10-21-2013 03:20 AM Click Here to See the Profile for AustralianClick Here to visit Australian's HomePageClick Here to Email AustralianSend a Private Message to AustralianEdit/Delete MessageReply w/QuoteDirect Link to This Post
My rear window is lexan however i don;t recommend replacing it as it took days.
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thesameguy
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Report this Post10-21-2013 03:04 PM Click Here to See the Profile for thesameguyClick Here to Email thesameguySend a Private Message to thesameguyEdit/Delete MessageReply w/QuoteDirect Link to This Post
FWIW, I have an early 7th gen Celica, which has a polymer moonroof. 14 years later, it looks terrible. It's terrifically abraded and I suspect sun damaged. It looks terrible from the outside, and cloudy from the inside. That said, I enjoy the fact it's saving precious pounds on a lightweight car ('00 Celica GT-S weighs less than a Mini Cooper S), but if you're sensitive to aesthetics you may want to apply some sort of poly film to it so it doesn't end up like mine.
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rogergarrison
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Report this Post10-21-2013 05:56 PM Click Here to See the Profile for rogergarrisonClick Here to Email rogergarrisonSend a Private Message to rogergarrisonEdit/Delete MessageReply w/QuoteDirect Link to This Post
The plexiglass likely isnt as rigid as the glass one. Ill expect the sides to bow up slighly when latched so the sides will leak and have wind noise. Airflow may also help pull the sides up. I know my racecar (thunderbird) with lexan windshield would pop up and out (not pushed in like you would think). Thats why we had metal clips bolted thru it to the body. Pretty sure there is also a vacuum over the roof close down too. Maybe your wont.
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AusFiero
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Report this Post10-22-2013 05:01 AM Click Here to See the Profile for AusFieroClick Here to visit AusFiero's HomePageClick Here to Email AusFieroSend a Private Message to AusFieroEdit/Delete MessageReply w/QuoteDirect Link to This Post
I am trying to work out why? If you are worried about weight for an autocross car you would just fit a standard non sunroof roof.
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rogergarrison
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Report this Post10-22-2013 10:52 AM Click Here to See the Profile for rogergarrisonClick Here to Email rogergarrisonSend a Private Message to rogergarrisonEdit/Delete MessageReply w/QuoteDirect Link to This Post
Or easiest yet, just pop out the glass when you autocross...even lighter I dont think theres any rules saying you have to leave it in. I autocrossed my Mercedes SL a few times with no top at all and no rollbars.
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cam-a-lot
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Report this Post10-22-2013 06:52 PM Click Here to See the Profile for cam-a-lotSend a Private Message to cam-a-lotEdit/Delete MessageReply w/QuoteDirect Link to This Post
you can just skip eating the day before..go for a good run... don't drink any water Voila! 10 lbs lighter
Not that it will make an iota of difference on the track
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Report this Post05-04-2014 05:55 PM Click Here to See the Profile for IMSA GTClick Here to Email IMSA GTSend a Private Message to IMSA GTEdit/Delete MessageReply w/QuoteDirect Link to This Post
How did this project work out? Everything OK?
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Report this Post05-05-2014 12:04 PM Click Here to See the Profile for 2.5Send a Private Message to 2.5Edit/Delete MessageReply w/QuoteDirect Link to This Post
Does this mean 'non sunroof' cars are ~9 lbs lighter and thus, faster?
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retroman
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Report this Post05-23-2014 10:40 PM Click Here to See the Profile for retromanClick Here to Email retromanSend a Private Message to retromanEdit/Delete MessageReply w/QuoteDirect Link to This Post
I apologize for the delayed response. Been a lot going on in my life lately. Over the past few months, I have gotten off of active duty in the military, moved twice between Hawaii and my current address, got a new job, purchased a house and my wife and I are preparing for the arrival of our first born. It's easy to say that life comes with changes, but 2014 is shaping up to be a landmark year for me. Anyway, that said, I have not had the opportunity to finish the final stages of engine assembly on the car, much less test my lexan sunroof. I've had the car parked in a hay shed and under covers on my father-in-law's farm. I was hoping to get some work done this past month, but my weekends have been pretty full with other activities and events too. Kinda depressing to see all my friends get their rides out for the summer, and I'm stuck with nothing to drive. Anyway that said, I do have some free weekends coming up. I hope to move the car to my own garage so I don't have to drive a few towns over every time I want to work on it. Once I get it together, I will get some new weather stripping for the sunroof, as it wouldn't be a fair test with the poorly improvised caulk job the PO did. As for the weight, maybe I'm a little crazy for being so excited to cut 10lbs. It is a street car after all and I do like having the typical commuter car amenities, but like they say, a job well done is all in the details. I will certainly post updates as I get them.
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