How do you connect the edges of fabric cover to windows?

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Built2Fly

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I am working on rebuilding a Hyperlite SNS8. I am fairly new to this and am wondering how to connect the edges of fabric cover to windows?

For example, this first one seem to have those transitions right around a tube of the fuselage. But how is that transition done? Any detailed pictures or examples? If it is simple enough, that might be my preferred way. I like things simple.
Sorrell_SNS-2_Guppy_N91542.jpg

This next one is even more interesting. There seem to be curved edges not along the tube line. How could this be done? Cover with fabric first and then cut out the transparent section? But then how is the transparent section installed one? Glue, stitches, or other tricks?
2.jpg

Your help is very appreciated.
 

Dana

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I can't speak to the Hiperlite directly having only seen one in person years ago, but most commonly the fabric is wrapped around the edge of a tube and glued there, then any window would attach with screws, usually to welded tabs... though from your pictures it looks like they're just attached to their own frames.

Windows attached directly to the fabric usually have a reinforcement glued to the fabric. Inspection panels (sometimes sheet metal, sometimes clear plastic) typically have a thin plastic ring or other shape glued to the fabric on the inside, then additional reinforcement glued over that, then it's drilled and the cover is attached with tapping screws. The rear windows on my T-Craft had a plywood frame glued to the inside of the fabric, with the windows screwed to that.
 

Pops

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Early Cubs also had the rear side windows installed to the fabric. Friend of mine has a April, 1939 Cub Sport ( 3 piece windshield, tail skid, 65 Hp lyc engine, etc. ) with the windows installed to the fabric.
 

Hot Wings

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Pic of a side window from a Bellanca. A light frame with the fabric glued directly to it.
I've seen* similar with little more than a piece of .020 aluminum of the shape desired glued to the back side of the fabric and then the fabric was cut out. Then the Plexiglass glued/screwed to the aluminum from the inside.

* No endorsement or recommendation offered.
 

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Built2Fly

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Thanks for the ideas, folks.

I think I will make it simple and let all the edges meeting on tubes. If there is no tab on the tube, I will need to drill holes on the fabric covered tube section. I assume that is alright and will not hurt the integrity of the fabric/tube attachment?
 

Mohawk750

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Great project, love the hyperlite!

I assume by your questions that you received the aircraft with the fabric removed? Otherwise you would be ale to see how it was done originally. There are many methods used to finish out windows and openings on the many varied aircraft.

As stated earlier, all seams are glued to to the primary structure and around some light alloy frames and reinforces with a second layer of fabric tape. I highly recommend you get a copy of one of the ceconite/polyfiber/Stewart fabric manuals and/or videos (probably available free on the net) and read through. Its all there and reletively easy once you are familar with the process.

Cheers
 

Built2Fly

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You are right. I got the project without fabric cover. It is a fun project and I am having a good time working on it.

I have watched quite a few video on YouTube abut various covering system. Those video gave me some general ideas, and I am sure there will be a lot of questions when it comes time to actually do it.

The original plan uses factory sewn fabric envelopes that are glued onto the frame. It seems that these factory cover comes with the transparent panels already fabricated on. So the question I am trying to figure out is how to do those transparent sections myself with the other systems you mentioned (polyfiber or Stewart). The idea I am coming up with (from the feedback here) is that I will use fabric cover up to a frame tube at about shoulder height, and then cover the top half of the cabin with acrylic sheets.

By the way, I am now seriously considering the Oratex fabric. I really like it simple and quick. Besides, I like to avoid working with chemicals if I can.
 

Mohawk750

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I've covered one aircraft, my own with Stewart Systems which is water-based and "relatively" non toxic. I found it easy to use and it have provided results that have stood the test of time. Aircraft was completed in 2000 and still looks great today but has always been hangared. I have assisted with a couple other covering jobs all using Stewart Systems.

I am no authority, others here have covered dozens of aircraft I am sure.

Orotex would be an excellent option for a small airframe as your square footage/cast would be reduced. You will still trade money for time but you will have a nice airplane that you can fly sooner.

personally I'm on the opposite side of the equation where I would prefer to trade my time for savings. These small aircraft are great candidates for some of the low cost "homebuilder" covering options and could still be done in a short time with excellent results.

Check out this link. Latex

As for you window issue there are probably several options but you want to keep it simple and light. I don't know if it will work with Orotex but if you could maybe duplicate the window pocket idea by doubling up a couple layers of fabric, cutting out the window shape and glueing in a piece of acrylic on the back side. Then maybe add a layer of fabric on the backside for a finished look?
 

Built2Fly

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Thanks a lot for the ideas, @Mohawk750.

The Steward system looked attractive to me, particularly the water thinner. And I have been looking at the SimplexAero's latex experiment. So what you said hits right on.

My main thinking on Steward/Latex vs Oratex is the time vs cost tradeoff, plus some space constraints I have. Hiperlite is a small airplane. I think I can do it with a bit over $3000 wtih Oratex (thinner fabric, lower cosmetic grade). I plan to do a more accurate estimate soon. With Steward/Latex, it is probably $2000? The price difference is there, but manageable (because the surface need to be covered is not that large).

The tradeoff is probably the extra step of painting and the need to build a paint booth. I am doing this in my small garage, so I guess I will have to do it on my small side yard. This created some extra challenges for me. The material for the booth will cost some extra money (I already have an air compressor). The plus side is that I can spray on any pattern I wanted, which would be cool.

Maybe it makes more sense if the airplane is larger? Building a paint booth is the same amount of work, but the price difference for a larger airplane would be more significant? Anything else I might be missing?
 
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I made flat .032" T6 aluminum frame panels and epoxied them to the tubes surrounding the window openings. The frames are fitted to the fuselage tubes so the edges don't show.

The window shape cut out of the panels allows just enough space to attach the Lexan window material on the inside.

The Oratex fabric goes right over the frames and can be cut flush with the openings after gluing and shrinking, or it can be wrapped through the openings and glued on the inside.

The Lexan can be attached using rivets or Very High Bond tape.

The frames make for a clean, light, simple installation.
 

Built2Fly

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Thanks for the ideas, @SheepdogRD.

When you fit the aluminum panel to the frame tubes, how is it done? And how is it epoxied? I guess that the aluminum panel needs to be a bit larger than the frame so it wraps around to give you enough contact area for epoxing? How much edge did you leave for Oratax glue when you cut out on the aluminum panel?

It would be great if you could post a picture of your setup. That would help tremendously.
 

Mohawk750

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Built2fly,

I don't think you need a spray booth to do latex. Some folks are rolling it on and "tipping" it with a brush with excellent results. You just need an area that you can control air flow and reduce contaminates (dust/bugs) etc. I don't see why it should cost more than a $1000 to cover a small airframe with non-certified fabric, 3M Fastbond adhesive (same as Stewart Ekobond) UV blocker and latex paint. However this may depend on your location and ability to source these products at decent prices with little lost to shipping.

If you buy fabric covering supplies from Wicks, Aircraft Spruce etc. you will pay a premium.
 
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karmarepair

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If you buy fabric covering supplies from Wicks, Aircraft Spruce etc. you will pay a premium.
I have never been able to find a reliable supplier of the 1.7 oz heat shrinkable uncertified Dacron cheaper than Aircraft Spruce, but you're right about the liquids, especially with shipping/hazmat fees. The 3M waterborne contact cement is readily available at every AceHomeLoweMen from Cape Breton to Cabo San Lucas and all points in between, and latex house paint, same/same.
 

Built2Fly

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That's an interesting idea. I do have a roll of fabric that came with the kit. I don't know what kind of fabric it is. It is about 62 inch wide and roll into a big roll. I am guessing that it should be enough for my little airplane. Is it a way to tell what fabric it is from the pictures?

20210107_185929.jpg

20210107_185949.jpg
 

Mohawk750

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Well if there are no stamps or identification printed on it it will be uncertified fabric for sure. If it came with the kit then it's likely dacron/ polyester. You could try and add up the thread count per inch each direction and compare it to the specs on aircraft spruce website. You could cut off a yard and weigh it.
 

Built2Fly

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I am learning on the Stewart System and the latex paint. The more I am reading, the more I like the idea. It has its strength and weakness, but I like it for two things:
  • Now I can understand how the gluing system works. What is attached to what, and what gives its strength. That means tremendous to me so I can really figure out what I need to do at each step and do it right. The Oratex to me is still a mystery. There are a lot of contradicting steps that don't fully make sense to me yet.
  • All the material needed can be easily bought in common stores. 3M 30-NF glue, latex paint., are all available at many hardware stores or online. I like that freedom and choice it offers (and of course the lower cost).
Thanks for bringing up this idea.
 

Mohawk750

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Glad to help, as I said my only real experience has been with Stewart Systems. From what I remember Once all the fabric tapes and patches are glued on you brush a thinned coat of the Ekobond on all the remaining white fabric surfaces to encapsulate the fibers. This looks kinda ugly when viewed from the inside but I don't think there is any reason why you couldn't apply a coat of latex colour coat on the backside of the fabric in exposed areas to improve the look. Only concern would be added weight.

I've enjoyed the links you shared as well and it would seem that a latex finish will last 10 years if cared for. so the recipe is non-certified dacron, glued on with 3M 30-NF a couple coats of latex paint (brush, roll or spray) and may some trim colour or vinyl decals for trim.

I don't think it could be any less expensive and for a sub $10K ultralight seems totally appropriate to me.
 

Built2Fly

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Look is not all that important. I watched some video last night. It seems that Stewart System used thinned Ekobond as the primer before the paint. The WienerDogAero guy instead used some Gribber primer. That may be a better looking option than the green Ekobond.

I also like the cost saving aspect of it. It looks like that I have enough fabric already. So all I needed now is just some 3M 30-NF and a few gallons of latex paint. It looks like I can have the covering done for a grand total of a few hundreds of dollars and some elbow grease. :) Not a bad deal.
 

malte

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I made flat .032" T6 aluminum frame panels and epoxied them to the tubes surrounding the window openings.[...]

The frames make for a clean, light, simple installation.
This is basically what I would suggest. aluminium is fine, or plywood, if you prefer.

You can get paint for Oratex, too.
 
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Thanks for the ideas, @SheepdogRD.

When you fit the aluminum panel to the frame tubes, how is it done? And how is it epoxied? I guess that the aluminum panel needs to be a bit larger than the frame so it wraps around to give you enough contact area for epoxying? How much edge did you leave for Oratex glue when you cut out on the aluminum panel?

It would be great if you could post a picture of your setup. That would help tremendously.
20210109_134218s.jpg

My window frames are fitted just to the center of the fuselage tubes. After surface prep, I put a bead of epoxy all along the edges and clamped them in place with tape. I left a small fillet of epoxy on the inside. After the epoxy cured, I smoothed the edges of the frames so they wouldn't present sharp edges to the fabric. At the bottom of the picture, you can see where the frame meets the side stringer; the junction is covered with fabric and finishing tape.

You could also make frames that overlap the center of the tubes just enough to let you break the edges of the frames in line with the tubes; that would give additional contact area for epoxy. As installed, these are plenty strong.

The fabric stops at the window. Finishing tape wraps about an inch inside the window. If I were doing it again, I'd just wrap the fabric and skip the finishing tape for a cleaner look. I'll seal them with a thin line of black silicone, and I think that will be as effective as the finishing tape.

My windows will be riveted in place, because I'd already drilled the holes in both the frames and the window panels before I discovered Very High Bond tape. If I were doing it again, though, I'd use VHB tape and maybe one rivet in each corner.

Inside finish for the window panels will be .040" Kydex installed with VHB tape.
 
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