Foamie Window and Door Rough Openings

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Foamie Window and Door Rough Openings

Postby SrMofo » Tue Feb 06, 2024 8:53 am

Searched but couldn't find anything.

I'm building a Foamie with fiberglass/epoxy skin. I want that protective fiberglass coating wrapped around the opening to prevent water intrusion between the foamie layers if/when the window seal fails.

Did you cut your openings after applying the fiberglass?

If you cut them before, how much fiberglass thickness did you account for for the rough opening?

I know glass doesn't like hard corners, but with tape applied on the bias, a decorative trim ring around the windows to hide the broken strands, and maybe a small radius I think its doable to apply the glass into the opening after the shell is glassed...but what do I know. Just hoping to get some other opinions before moving on.
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Re: Foamie Window and Door Rough Openings

Postby KCStudly » Tue Feb 06, 2024 11:05 am

To get fairly sharp corners on FG I used a method called "flocking". Search my build thread for "flock" to see examples.

Before glass I chamfered the corners about 1/4 inch. Then I used packing tape on scrap strips of 5mm ply to make dams. Attach the dams flat on one side of the corner edge and about 1/16 inch strong (sticking out) past the 90 deg edge. This leaves a wedge shaped void or pocket that you can pack thickened epoxy into. Once cured the dam peels off easily leaving one side nearly perfect with maybe just a couple of low spots that need a little 5min filler to be perfect. The other side of the corner will be a little rougher from squeegee work, but that little extra 1/16 inch is easy to sand back.

I did this on wood frame inserts so that I could glass up to the corner from both sides. Doing it on foam only would be harder to securely attach the dams, and would make sanding much harder because the foam sands too easily compared to the glass filler. But food for thought for you.
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Re: Foamie Window and Door Rough Openings

Postby KCStudly » Tue Feb 06, 2024 11:10 am

This method takes a bit more time and effort than rounding the corner over because you have to glass over one side first, let it cure at least to green, and trim before glassing and trimming the second side; but when you do trim or sand up to the corner you've got that full 1/4 inch of glass fill keeping the corner from splitting open.
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Re: Foamie Window and Door Rough Openings

Postby KCStudly » Tue Feb 06, 2024 12:55 pm

IMO, trying to build a glass and foam camper w/o wood (or other suitable) framing is not advisable. In order for the door and hatch frames to be rigid enough to hold their shape and form good sealing surfaces, you'd have to use plenty of glass and epoxy, which is expensive and adds it's own weight (unless you get extra complicated and start making foam core structural members for these areas).

By using light weight and rot resistant cedar as a framing material and fully encapsulating it, I only needed 2 plys of 6oz glass to develop the shear strength and penetration resistance that I was comfortable with. Yes, straight grain, knot free cedar is expensive, too, but it is a pleasure to work with. Epoxy and glass, meh, not so much.
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Re: Foamie Window and Door Rough Openings

Postby SrMofo » Tue Feb 06, 2024 3:59 pm

KCStudly wrote:IMO, trying to build a glass and foam camper w/o wood (or other suitable) framing is not advisable. In order for the door and hatch frames to be rigid enough to hold their shape and form good sealing surfaces, you'd have to use plenty of glass and epoxy, which is expensive and adds it's own weight (unless you get extra complicated and start making foam core structural members for these areas).

By using light weight and rot resistant cedar as a framing material and fully encapsulating it, I only needed 2 plys of 6oz glass to develop the shear strength and penetration resistance that I was comfortable with. Yes, straight grain, knot free cedar is expensive, too, but it is a pleasure to work with. Epoxy and glass, meh, not so much.


I guess I should have added the doors are framed in wood, The windows I was hoping to avoid the wood frame because its adds no inherent value. The window is pulled tight and held in with a trim ring.

Originally I was going to wrap both sides of the foamie in 1/8" ply but it is a slide in and that will likely add another 100lbs of weight I just don't want and after doing some testing decided it wasn't necessary other than for aesthetics....but I can paint it. I can tell you I much prefer working in wood rather than the foam. Its definitely tough to hold the accuracy in foam that I am used to in wood.
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Re: Foamie Window and Door Rough Openings

Postby swoody126 » Tue Feb 06, 2024 9:40 pm

SrMofo wrote:Searched but couldn't find anything.

I'm building a Foamie with fiberglass/epoxy skin. I want that protective fiberglass coating wrapped around the opening to prevent water intrusion between the foamie layers if/when the window seal fails.

Did you cut your openings after applying the fiberglass?

If you cut them before, how much fiberglass thickness did you account for for the rough opening?

I know glass doesn't like hard corners, but with tape applied on the bias, a decorative trim ring around the windows to hide the broken strands, and maybe a small radius I think its doable to apply the glass into the opening after the shell is glassed...but what do I know. Just hoping to get some other opinions before moving on.


"SrMofo", a coupla points to ponder ...

i might suggest securing THE windows n doors you intend to install FIRST

next step is to determine what size holes after you decide on the weight of glass cloth you intend on using

YES a small 1/4 round over will be in your favor

cut and install the bias tape prior to glassing the sides so the edge of the side covering will be under your flanges so the tape feather edge will not be as much of an issue

i like to cut my bias tape a bit wider than factory tape and feather the edges just a bit more so they do not present you w/ a prominent edge

for my 2nd and 3rd coat of epoxy over the taped edge i mix a light epoxy slurry w/ wood flour to fill the weave and extend the epoxy a bit furthur out so any transition is not as much of an issue
ALL epoxy recoating is done as HOT COATS ... that is that once you begin you HAVE TO stay with the step until the weave is filled plus one coat of unthickened pox as a final coat

after an overnight curing and before the pox sets up hard and wearing a heavy leather glove i drag a piece of Sure-Form file along the edges to knock down any hard edge that may remain

then you will be ready to glass the sides right up to the window n door edges

BON CHANCE

sw
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Re: Foamie Window and Door Rough Openings

Postby saywhatthat » Thu Feb 08, 2024 2:46 pm

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Last edited by saywhatthat on Thu Feb 08, 2024 3:49 pm, edited 2 times in total.
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Re: Foamie Window and Door Rough Openings

Postby RJ Howell » Thu Feb 08, 2024 3:08 pm

SrMofo wrote:
I guess I should have added the doors are framed in wood, The windows I was hoping to avoid the wood frame because its adds no inherent value. The window is pulled tight and held in with a trim ring.


I framed my windows as well.. compression against just foam didn't sit good with me. Remember we're driving down a road and causing a mini earthquake on the camper.
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