Skylights!

[jackhartjr]

Hi folks, getting ready to replace the skylights on our Scenicruiser.
Would you go with 1/4 inch or 3/8 inch lexan?  (They are 37X24 with rounded corners.)
The front one in it now is 3/8's, however as strong as Lexan is I wonder if that is overkill and the 1/4 inch might be better.  It it easier to get the mouling for the 1/4 inch too!
Thanks in advance!
Jack

[platinum mci]

I would think 1/4inch would be plenty strong to hold up to almost anything hitting it.

[gus]

Jack,

Please note that any plastic has a very large expansion/contraction movement. You cannot install plastic tightly into a window like glass.

I've replaced a few airplane windshields and side windows. They all have to be installed loosely and if bolted in the bolt holes have to be quite a bit larger than the bolts. In effect, the plastic floats inside the frame.

In addition, unless it has changed, Lexan is not satisfactory for direct sunlight installations. Check this out as it may have changed. I started to use on aircraft side windows a few years ago and didn't because of this. I wanted to use it because it is so tough.

[jackhartjr]

Hi Gus, I am reading that they make a 'Lexan XL' that has great UV protection and is indeed very good skylight material.  Apparently this is a fairly new product.
I appreciate the tip on the expansion, I will keep that in mind.
Thanks!
Jack

[HighTechRedneck]

The side windows on most RTS buses (including mine) are Lexan.  They are very thick.  I haven't measured but would guess them to be 3/8".  I have read that they are bullet resistant up to .38 caliber.  Hopefully I'll never need to test that.

That said, unless you are likely to get strafed by some .38 packing pigeons, I would think 1/4" would be fine.   

[JohnEd]

Strafed?  Where do you live and how big are those pigeons?

John

[kyle4501]

I've seen a glass sunroof taken out in a hail storm while at a traffic light.

You can use what ever you like, but I'm gonna use 3/8" & not worry about it.

I also plan on cutting it ~3" larger than the opening & using that black rope stuff (they used on car windshields) to seal it to the body. (Possibly a bolt at each corner to help with the curvature.)

[Chaz]

Could the curvature be put in with a little heat from a heat gun and some care?

Just curious as my skylight is also cracked and there is just a small curve to it. Also, I'd like to do the Vista wondows with plexi or the new lexan also.

  Chaz

[Dallas]

Chaz,

I've used a propane torch and also a heat gun to curve the different types of clear plastics. It isn't hard to do, but if you use a torch be very careful not to get one spot too hot ... it gets big air bubbles in it.

DF

Could the curvature be put in with a little heat from a heat gun and some care?

Just curious as my skylight is also cracked and there is just a small curve to it. Also, I'd like to do the Vista wondows with plexi or the new lexan also.

  Chaz

[kyle4501]

Chaz, The heat could work, but I'm sure to have 'issues' if I tried that 

That's part of the reason I'd use bolts in the corners.   
Might eliminate the air bubbles . . . 

[Blacksheep]

Using 3/16" and thicker lexan back when I was manufacturing 1/4 scale race car parts, I was able to bend and shape it by making a jig in which I mounted water bed heater strips on both sides. It heats it evenly from both sides and doesn't distort it in any way unless of course you forget it's there. Don't ask me how I know that part! I can tell you this, that if you try to heat it with a torch or even a heat gun, you won't get satisfactory results! The part you heat will cool before another part. In other words, if your heating say a 12 inch piece and moving your heat source from one end to the other, by the time you get to the other end, the first end will already have cooled causing the whole piece to NOT be heated evenly! Using a heat gun or torch on the edges is fine to achieve a glossy finish but to use them to bend or shape, is questionable IMHO!

Ace

[kyle4501]

That's a cool neat idea. How much heat (watts per sq inch of lexan) is needed & for how long? What temp is needed to form the lexan?


 You never know, I might actually bend some Lexan one day.    

[luvrbus]

Jack, isn't the Mylar a better product for what you are going to use it for,I saw a fab shop bending the stuff in a sheetmeatal brake after heating in a tub of hot water for a hot rod door windows and was told it doesn't scrstch as easy as Lexan    good luck

[Blacksheep]

Kyle, I'm not sure on the wattage but I mounted 2 old water bed heater strips on 2 pieces of much thicker lexan which were mounted on 2 pieces of board. On one of the those boards I mounted a metal handle which would be designated the UPPER. Each assembled piece is about 18 inches long. Each one plugs into an outlet separately. Plug them both up until hot. lay one piece of lexan on bottom assembly on your pre determined line and lay the upper assembly on top directly over the same line. Let them sandwich the lexan for about 15-20 seconds and quickly remove your lexan. Place the lexan in the jig or even a small brake and bend away! If you get it too hot or you let it sandwich for too long, you can use compressed air to cool it off a touch! Just a quick blast would do it! It cools quickly!

You can also place your jig or brake with lexan in the home oven but then EVERYTHING gets hot!

Ace

[Chaz]

Thanx Blacksheep!! Neat idea. I may try that idea............. after Kyle tells me how his worked out. 
  The hot water and even the oven trick sounds like a possibility also. The skylight in my 4108 isn't all that big and doesn't have much of a radius in it. I would think that much curve could be created without too much trouble.
But in the case of the Vista's...............'nother story. 

  Thanx again man,
      Chaz