Jeffcreber wrote:"Stargazer" Window ConstructionSince posting our build, I’ve received a few inquires regarding the installation of our Lexan polycarbonate “stargazer” window. I figured I would do a proper set of instructions for anyone who would like to try this method with their build.
The windows was one of the most challenging aspects of our build however it has also been one of the most rewarding features. I was not able to find much information regarding custom window installation during my research stage so I pretty much had to wing it. This caused me some anxiety as I would be nearing the end of my build before I’d know if the window would work at all. Lucky for me, the method I used seems to have worked and I’ve had no leaks on multiple camping trips. The trailer has been driven through rain storms on the highway and it has held up just fine! Knock on wood... My wife and I are taking the trailer on a four month trip this summer so the window will receive plenty of road testing. I will post updates on how the window holds up and if we run into any problems.
BEFORE USING THIS METHOD: Please note that using polycarbonate as a window might not be allowed with RV's in some areas as it does not shatter upon impact. My trailer was already completed when I received this informations so it was a lesson learned too late. You may want to do a little research before using it with your own project. I wouldn’t want anyone to receive fines or worse because it doesn’t meet code. Use this information at your own risk.
Also note that my diagrams will show the window construction as flat. The construction is obviously curved in real life. You may also notice that the framing in my diagrams differs slightly from my actual construction pictures. My diagrams represent how I would do the framing on my next trailer having the knowledge that I have now. The modifications have been made to make the construction easier. Keep in mind that you are not restricted to the dimensions I have used in my example. This method can be applied to different shapes and sizes of trailers and window openings. Adjust your framing accordingly and remember to make sure your window edges line up with your spars for your screws. Also make sure the side framing of your window will be wide enough to maintain the shape of your window once it is installed. My Google Sketchup file is attached to this thread.
Now that all the blabbing is out of the way, lets begin!
Materials:-5/8" x 1-1/8" Wooden Spars For Framing - (Use whatever type framing works for your design)
-1/8" Thick Lauan Plywood
-1/8" Thick UV Resistant Lexan Polycarbonate Sheet - (UV resistant to avoid future clouding)
-Aluminum Angle - (Interior Trim)
-Aluminum Flat Moulding - (To hold the exterior aluminum skin in place)
-Good Quality Countersink Drill Bit - (Good enough for aluminum)
-Stainless Steel Countersunk Head Screws
-Weather Sealant For Plywood
-RV Putty Tape
-ProFlex Flexible RV Sealant - (Use whatever clear sealant you have researched that works for you)
-Rubbing Alcohol & Disposable Cloths - (For the removal of clear sealant)
-Painters Tape
-Tuck Tape
The spars surrounding the window are doubled up. I did this because it makes it easier to fasten down the window with screws later on in the process. The two sections to the left and right of the window were made so the polycarbonate will hold it's shape once fastened down. It's hard to notice from this diagram however all of the framing where the window will sit has 1/8" shaved off on the exterior side. This will allow the window to sit flush with the rest of the trailer. This 1/8" depth difference will be apparent in upcoming diagrams. The spars on the interior of the trailer are all flush with each other.
Framing
Insulation
Insulation
Make note of the 1/8" depth difference for the window.
Skinned the framing & insulation with 1/8" lauan plywood. Treated the lauan with a few coats of water sealant to prevent rot in case any water manages to sneak in.
Make note that the 1/8th depth difference has been maintained after the luan plywood has been installed.
I installed the inner aluminum angle trim before installing the window. I did this so I could use clamps while the adhesive dried.
Interior aluminum angle trim.
I placed my aluminum skin over the window opening on the exterior of the trailer. I then traced out the window opening from the inside of the trailer prior to installing the window.
Putty tape was applied around the perimeter of the window opening prior to installing the window. This creates a proper internal seal.
Lexan window installed over the putty tape seal.
The Lexan window sits flush with the lauan plywood.
The top and the bottom of the Lexan window are screwed down into the wooden spars below. I put a screw in every 2 inches along the top and the bottom of the window. I did not use many screws on the sides of the window as I did not want to interfere with the screws that are used for the final exterior edge trim. The screws from the final exterior edge trim will be more than enough to hold down the sides of the window.
Make sure to pre-drill and countersink the screw holes in the Lexan before screwing it down. This way the screw heads will sit flush with he window. Before installing your screws, inject a little sealant in the screw holes. Do not get any sealant or chemicals on the visible portion of the window as it will cause damage.
For added protection, I tuck taped over any seam that would not be visible once the aluminum skin would be installed. I also did this over the screws at he top and bottom of the Lexan as it would also not be visible.
Measure out and cut 4 pieces of flat aluminum moulding that will be used to hold down the aluminum skin surrounding the perimeter of your window. Use a file to smooth the cut edges of the aluminum. Pre drill and countersink holes on your flat aluminum bars. Do a test run on a spare piece of aluminum first for practice. Place a screw in your countersunk hole to see if you are getting the right depth. I did my best to have my screw heads flush with the moulding. My holes are spaced approximately 2 inches apart.
Aluminum skin
Place some painters tape around the perimeter of your window for protection. Attach your aluminum skin at the top so it lines up exactly with your window. I temporarily attached each piece of moulding with a screw on each end and then predrilled and inserted screws in the remaining holes. Once you completed this process, remove the screws and moulding. Ensure that you label which piece of moulding was used for which quadrant of the window.
Clean off any metal shavings and debris. I used a vacuum to remove debris from the drilled holes.
Peel back the protective layer on the aluminum skin around the perimeter of the window opening. You are now prepped and ready re-install the moulding with sealant.
I ran a small bead of sealant along the bottom of my moulding before installing. I also injected sealant into each screw hole before screwing the moulding down. This creates a seal and prevents galvanic corrosion.
Aluminum moulding & skin
Now that your aluminum moulding is installed, clean off any excess sealant with disposable cloths and rubbing alcohol. This was recommended to me by an airplane mechanic. Worked wonders for me! Remove your painters tape and you should be good to go.
Some putty tape was squished out around the perimeter of the window. I cut away some excess putty however I left enough to keep a proper seal. I simply used my finger to pack it neatly against the moulding.
Enjoy your window!
Do some research before using any chemicals to clean your window. Using chemicals on Lexan will cause it to cloud. As far as I know, there is nothing you can do to fix it. I've yet to do proper research regarding cleaning techniques so I simply use a cloth and water for now. User "JaggedEdges" also mentioned to keep DEET bug spray away from the window. Don't spray it anywhere near the window as it will also cause damage. Feel free to post a reply if you have any valuable information regarding the cleaning and maintenance of Lexan Polycarbonate.
-Jeff
by Johnysteam » Fri Mar 10, 2017 5:01 am 
