Is a Plexi roof a good idea?

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Is a Plexi roof a good idea?

Postby dperry324 » Thu Aug 14, 2014 9:22 am

Hi All!

I'm still designing (in my head) my build. One thing I've decided on is that it is going to be a sleeper, with no galley and no back hatch. One thing that I would really like to have is an open roof to look out at the stars, trees and the moon. So I'm thinking of skinning my roof in plexiglass. Has that been done before? What are the considerations?

One thing that worries me about it is that plexi is somewhat brittle, and might be prone to cracking, especially around bends. But I'm leaning towards a generic benroy, which has a mostly-flat roof line. I know that I would have to have a single-skin roof, or to have a double-skin plexi, ie inside and out. I worry about water condensation and fogging of the glass too. Is this even feasible?

My other thought would be to put pre-made automotive windows in between the roof spars. But that option sounds like it might triple my costs.

Thoughts?
Regards,
Darryl
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Re: Is a Plexi roof a good idea?

Postby aggie79 » Thu Aug 14, 2014 12:41 pm

Check out Bob Henry's lexan roofed teardrop.
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Re: Is a Plexi roof a good idea?

Postby dperry324 » Thu Aug 14, 2014 1:48 pm

aggie79 wrote:Check out Bob Henry's lexan roofed teardrop.

I've been searching, but I can't find it. Any help would be appreciated.
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Darryl
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Re: Is a Plexi roof a good idea?

Postby Juneaudave » Thu Aug 14, 2014 2:43 pm

Do a search on Chubby....that's the name of the lexan roof tear Bob Henry built. :thumbsup:
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Re: Is a Plexi roof a good idea?

Postby kayakdlk » Thu Aug 14, 2014 2:46 pm

here you go
http://tnttt.com/viewtopic.php?f=21&t=47157&start=0

Search for lexan roof and you will find more links

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Re: Is a Plexi roof a good idea?

Postby tony.latham » Thu Aug 14, 2014 11:51 pm

Plexiglass is brittle and cracks easily if you screw it down a bit tight –perhaps you knew that. Lexan isn't. In fact if your firearm is powerful enough to shoot through what ever thickness of Lexan you have, it won't crack. It's what they make bullet proof "glass" from. The downside with it is that any exposure to petroleum products will cause it to craze.

What I'd focus with on Bob's build is how he sealed it and any other issue he's had with. It IS a damn cool build and it'd be great to listen to how it worked out for him.

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Re: Is a Plexi roof a good idea?

Postby lawsonpix » Fri Aug 15, 2014 2:19 pm

Lexan (polycarbonate) is definitely a better choice than plexiglass, but scratching may be an issue.

I found a little bit about cleaning it which should shed some light:
http://www.eplastics.com/Plastic/Plastics_Library/Cleaning-Lexan-Polycarbonate-sheet
here's an interesting tidbit of information:
http://www.coloradoplastics.com/blog-0/bid/42625/Polycarbonate-Lexan-vs-Acrylic-Lucite
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Re: Is a Plexi roof a good idea?

Postby GerryS » Sat Aug 16, 2014 6:14 am

Bob, you ok? I figured you'd have strong feelings either way on this subject :)
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Re: Is a Plexi roof a good idea?

Postby bobhenry » Sun Aug 17, 2014 7:22 am

I'M HERE !

I absolutely love Chubby. As with any selection of material for a build there are pros and cons. The latest camping partner is way claustraphobic and she lover the wide open feeling staring out at the stars. I have camped in at at 95 degrees and it's a sauna, I have camped in it at -18 wind chill (-1 actual temp) and it snowed inside. With a heater running I can keep the inside very comfortable in the cold but the moisture from your breath form a frost on the inside of the uninsulated roof and it will flake off on occasion just like single pane windows in a home. I must say the works of Jack frost are still the same interesting swirls as the ones on any window. I have developed a technique to almost eliminate the frost thing. A small fan suspended near the center of the roof is pointed upward and it washes the heat over the roofing reducing the frosting and also helps to remix the stratified air and wash it back down the sides to where you are sleeping. In teen temps you can literally feel the layers of air at the mattress it might be 30 degrees. Lift your hand a bit and its 40 at the mid point it is 50 and at the roof it's 70+. It seems impossible for frost to form at these temps but it does if the roofing is cold enough. As to the sauna a good pop up placed over the trailer during the hot days helps deflect the sun and I have made accomidations for a 6000 btu window shaker to be added thru the window. I have successfully formed the lexan using a heat gun you have to be careful it can cloud up if it is overheated. Being a benroy style not even trying to bend the ends might be an idea just cover the flat roof area. A careful application of 100% silicone and a second barrier of ice dam tape over the lapped area should eliminate any water problems. Oh yes drill well spaced holes to attach the roofing material. These should be slightly oversized for the screws to allow some movement of the poly carbonate. To eliminate pressure fractures at the screw sites use a plastic rosette under the screw head to disperse the pressure. I bedded each of these holes with a blop of silicone under the rosette washer. To date 7 years later no leaks and it was stored outside in the rain sleet and snow 24-7 for all but the last year of its life so far. I might add it has never required painting :) and has survived a hail storm without dents :) and most probably will never delaminate :D I would do nothing different.
That's my spin on the subject ! :thumbsup:
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Re: Is a Plexi roof a good idea?

Postby absolutsnwbrdr » Sun Aug 17, 2014 11:13 am

lawsonpix wrote:Lexan (polycarbonate) is definitely a better choice than plexiglass, but scratching may be an issue.


I strongly disagree, but the choice of acrylic vs polycarbonate depends on the individual needs of the teardrop owner.

I used 1/4" cell cast acrylic for my large skylights for two reason: UV resistance and clarity. My roof is flat so I didn't need flexibility, although acrylic can be formed. I also wanted something that wouldn't get scratched from tree branches. Polycarbonate will scratch much easier. Also, acrylic will stand up to weather much better. Its UV stability is far superior to poly, which means it won't yellow over time. And while it isnt as impact resistant as poly, it is still a very strong material and will stand up to the elements without issue. I got caught in a hail storm and didn't have a problem.

Since my roof is flat, I didnt need to use any mechanic fasteners. My panels are simply held on with caulk, and arent going anywhere. Solid as a rock.
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Re: Is a Plexi roof a good idea?

Postby bobhenry » Mon Aug 18, 2014 6:54 am

Hell I didn't know I just found a fellow selling "plactic sheet" !

I bought six 3.5 x 7' sheets of "plastic for $50.00

1/4 bronze tinted lexan. They were storm covers for industrial sky lights. He had torn down the building and salvaged 25 or so.

Here is some more info I just found on the pros and cons of the two materials.....

1
Strike the plastic in an inconspicuous spot with a small hammer. Polycarbonate possesses great impact resistance. The hammer blow will not make a dent. That is why it is often used to manufacture bullet proof and storm proof windows. Plexiglass (acrylic) is stronger than glass but not as strong as polycarbonate. It may shatter into large, blunt pieces.
2
Scratch the two plastic (again in an inconspicuous spot). Plexiglass is more scratch resistant than polycarbonate. This is the reason why polycarbonate lenses do better with a scratch resistant coating.

3
Pick the plastic up. Polycarbonate is about a third lighter than plexiglass. It is also a sixth the weight of glass, making it one of the lightest materials to work with.
4
Inspect sheets of the two materials that have weathered the elements for a while. Polycarbonate tends to yellow over time. Plexiglass has better UV light absorbing properties and does not discolor with age.
5
Check the light transmission properties. Light transmission is the amount of light that passes through the lens to reach the eyes. Plexiglass transmits 92 percent of optical light, compared to 89 percent transmitted by polycarbonate.
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Re: Is a Plexi roof a good idea?

Postby dperry324 » Mon Aug 18, 2014 4:27 pm

I've done some research and I believe if I were to skin 50% of the roof of my TD with poly, it would double the total cost of the TD. That stuff is just plain expensive! Plexi is much more friendly to my wallet.

That being said, I also brought this topic up with my wife. Her first thought on having a clear roof was that it would turn the whole thing into a hotbox. Realize that our outings would consist of east texas summer settings, so doing anything to increase the interior heat is not going to fly. So I'm prolly going to pull back and have maybe one or two small panels instead of a full roof.
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Darryl
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Re: Is a Plexi roof a good idea?

Postby kayakdlk » Mon Aug 18, 2014 8:59 pm

There are lots of builds on here with sun roof or moon roof (Whatever you want to call it) I found a 12"x40" fixed windows on Ebay and installed it above so when lying down we could look out at the stars. We also made curtains on boat track curtain rails to shut it and keep some of the heat out during the day, or for privacy at night. We love it and not sure I would build again without one. Some other builds have use car sunroofs (I found them to be more expensive, but they do vent) so I went with a fixed RV window. What ever method you use I am sure you will enjoy the openness.

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Re: Is a Plexi roof a good idea?

Postby bobhenry » Tue Aug 19, 2014 7:07 am

In all honesty the sun/moon roof ruins summer camping. I take Chubby out spring and fall and have my barn for summer and winter gatherings.

Yep it's nice to have backups :DImage
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Re: Is a Plexi roof a good idea?

Postby absolutsnwbrdr » Tue Aug 19, 2014 7:58 am

bobhenry wrote:In all honesty the sun/moon roof ruins summer camping

I was afraid of that when I was designing my new one. I remember reading your thread about the greenhouse effect. :?

Thats why I opted for two large (20x40 each) panels instead of the entire roof. Then had the girlfriend make snap-on, light-blocking "curtains". They work amazingly well to keep the light and heat out!

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You'd need quite a bit more material for the Chubby though!




btw... got my 1/4" cell cast acrylic at http://www.interstateplastics.com. Their site lets you customize the size panels you need, and will give you suggestions to save money. Shipping isnt cheap though, because of the weight.
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