Why can't I use film for heat and uv control?

[RKsailsolo]

Originally Posted by Sailing Ohm

Guess I really didn’t answer your question at all...
So in follow up your clarification... what bedding compound are you currently using? And what type of material are your window frames? If they are aluminum you have more options but ensure they are not painted black. If they are screw into the cabin wall types like mine then butyl tape might be your best friend.

If you need an adhesive and sealant, lately I’ve been using 3M 4000 for other jobs as it has high UV resistance and unlike a lot of other bedding compounds, it can actually be used with some plastics (which can be an issue with bedding ports).
So far no complaints and best part is it’s actually removable!

I think a lot of factories originally used construction grade silicon around hatches and ports that have addition fasteners.

Hey thanks up front for your input.

1. my window is surface mount. No frame.
2. Dow 795 and 3M 4991 VHB. I'm not confident 3M 4000 has better shear than the Dow 795. And the 4000 polyurethane will outgas and may be a nightmare to remove if it needs to be redone.

[Chotu]

Originally Posted by RKsailsolo

Interesting, your note on old adhesive technology. I'll research that, thanks.


Good luck on fasteners as a perimeter secured plastic window expanded can micro fracture and crack.

I'd rather bet on successful adhesion of the two bonding systems that are both engineered to perform well within plastic substrate thermal cycling.

Fasteners? Lmao.

Who said anything about fasteners?

If you want your windows to pop off again, use Dow 795 and 3M VHB tape.

If you want them to stay on this time, devise a system that allows for huge thermal expansion.

Of course I’m assuming you have large windows like I do. What size windows are we talking about?

Dow 795 and the thickest VHB tapes made can’t hold my windows for a single summer in the tropics. The only way you’ll have a hope of getting that to work is to triple up the VHB tape to make it much more loose and make an enormous bed for 795 to float it in. And it’s still a maybe since the VHB and 795 still let go after lots of tropical cycling in my case. Every single year they fail. Even with Primer 95. They stick to the hull just fine. They release from the polycarbonate.

Also... I didn’t say a WORD about old adhesive technology. The old technology was regarding the people telling you you can’t put window films on acrylic or polycarbonate. That’s old news. They now have films you can use.

[RKsailsolo]

Chotu, if I offended you in some way.. .that's not what I come to this forum to do.

Apparently I must have misinterpreted what you wrote earlier, "...I’m just going with mechanical fastening."

Seems like you have direct experience and I (we) do value learning from that.

My window is small. The bedding application is common. https://www.sailmagazine.com/diy/rep...xed-portlights

[Chotu]

Originally Posted by RKsailsolo

Chotu, if I offended you in some way.. .that's not what I come to this forum to do.

Apparently I must have misinterpreted what you wrote earlier, "...I’m just going with mechanical fastening."

Seems like you have direct experience and I (we) do value learning from that.

Sorry. No offense meant from my end either. May have got a bit more lively than it should have.

It’s a passionate topic because I have way WAY too much experience with 3M VHB and Dow 795 at this point. Experience I wish I didn’t have. Ha ha.

It falls off every single year. I’ve made all the mistakes with it in the past, then did everything according to 3M tech support specs only to find it STILL is failing this year. Peeling away from the polycarbonate.

I’m just trying to save you the headaches.

Turn be told, I’m done with these materials after many years of failures.

I’m devising a hardware based solution to allow the large windows to just expand and contract at will. Holding it captive instead of trying to immobilize it.

No fasteners. Just tracks to hold them in and sealant to make them watertight.

[RKsailsolo]

Chotu, no worries mate.

I misunderstoodbut got it afterwards that your working on alternative to surround and capture the window. Thx for clarification.

I can only imagine how much a big plastic window expands compared to my small window.

[qwert]

I used polycarbonate (lexan) which comes with a marelon laminate for my windows.Wildly extravagant but it was a leftover from a 'no expenses spared' building project. I emailed and spoke to the lexan lab about the adhesives to use and their application. Their recommendation was to lightly sand (500 grit) the area of window to be glued, then wipe said area with alcohol (surgical wipes about $5 a box). Their recommended adhesive was Dow 795.


In order to overcome the expansion problem I cut out with a 3mm centre punch from 3mm thick sheet a lot of small spacers.When I applied the 795 I put a rubber spacer every inch or so. This gave me a gasket 3mm deep all round which had enough flex to cope with the expected expansion differences between poly and cabin side. Note that the 795 takes up to 2 weeks to cure.


Now in its 3rd Australian summer and good as new (window and seal).

I would note that I also used screws around the edge with oversized (to cope with expansion) holes and large washers because I just can't bring myself to trust the structural integrity of a glued window on an ocean going vessel.......(!)

[Chotu]

Originally Posted by RKsailsolo

Chotu, no worries mate.

I misunderstoodbut got it afterwards that your working on alternative to surround and capture the window. Thx for clarification.

I can only imagine how much a big plastic window expands compared to my small window.

Ok, my guess is you’ll be just fine with the thickest VHB tape and thick 795. Those are significantly smaller than what I’m dealing with so the thermal expansion should be minimal. Mine are about 1.25 meters x 1.25 meters.

[er9]

Originally Posted by Chotu

Fasteners? Lmao.

Who said anything about fasteners?

If you want your windows to pop off again, use Dow 795 and 3M VHB tape.

If you want them to stay on this time, devise a system that allows for huge thermal expansion.

Of course I’m assuming you have large windows like I do. What size windows are we talking about?

Dow 795 and the thickest VHB tapes made can’t hold my windows for a single summer in the tropics. The only way you’ll have a hope of getting that to work is to triple up the VHB tape to make it much more loose and make an enormous bed for 795 to float it in. And it’s still a maybe since the VHB and 795 still let go after lots of tropical cycling in my case. Every single year they fail. Even with Primer 95. They stick to the hull just fine. They release from the polycarbonate.

Also... I didn’t say a WORD about old adhesive technology. The old technology was regarding the people telling you you can’t put window films on acrylic or polycarbonate. That’s old news. They now have films you can use.

have you tried sanding the surfaces of the plexi and fiberglass before applying the 795? i usually laser etch or sand with #250 grit the entire area to be bonded. makes a huge difference in adhesion.

[Chotu]

Originally Posted by er9

have you tried sanding the surfaces of the plexi and fiberglass before applying the 795? i usually laser etch or sand with #250 grit the entire area to be bonded. makes a huge difference in adhesion.

3M support recommended using Primer 94, which is what was used. No scuffing things up, unfortunately. I’ve tried literally everything else.

To be honest, I’m over this method. It just isn’t strong enough to corral the polycarbonate sheets into place. Fine for small windows or glass, I’m sure, but I want to do the windows one more time only. Then just re-caulk if they leak in the future.

All the windows are coming off my port side currently. Somehow, the starboard side (shaded from sun) is mostly fine.

I’m replacing the goop with mechanical tracks bonded to the hull to capture the panels in place while allowing them to expand and contract at will . Then filling gaps with something. Probably 795.

I’ll probably still need to replace caulking frequently, but it’s not a big deal if windows stay put.

[er9]

Originally Posted by Chotu

3M support recommended using Primer 94, which is what was used. No scuffing things up, unfortunately. I’ve tried literally everything else.

To be honest, I’m over this method. It just isn’t strong enough to corral the polycarbonate sheets into place. Fine for small windows or glass, I’m sure, but I want to do the windows one more time only. Then just re-caulk if they leak in the future.

All the windows are coming off my port side currently. Somehow, the starboard side (shaded from sun) is mostly fine.

I’m replacing the goop with mechanical tracks bonded to the hull to capture the panels in place while allowing them to expand and contract at will . Then filling gaps with something. Probably 795.

I’ll probably still need to replace caulking frequently, but it’s not a big deal if windows stay put.

priming is a joke, its just a way to sell more product. the sanding (moderately rough grit #220) gives it a tough mechanical bond. you should try one window, you might be pleasantly surprised. if you do, sand as much surface area on the ploycarb as you can get away with. ive taken small windows off that have been sanded and they take the surface gel coat off before releasing from the plexi. laser etching is the ultimate way to go but not practical at a dock.

[Bycrick]

Clean the fiberglass or other surround. Then do it again. Then sand both surfaces, including the edge of the plastic with 220 wet-or-dry. Clean everything with 90+% alcohol. Let it dry. Leave an 1/8” around the window. I used matchsticks but the idea of small rubber disks sounds worthwhile. I used Dow 795 and, so far, it’s stayed leak-free until the plastic got so bad that I replaced it.

[chrisr]

we use uv film on the inside of numerous windows and hatches - and it's super effective.

however i don't think the stuff we use would last on the outside. weather etc would get it off fairly quickly

of course there might be other (more expensive) stuff designed for the outside

incidentally, as a cheaper alternative to the sunbrella hatch covers, in our sleeping cabins we use silver duct tape. reflective so keeps the heat out, and darkens the room nicely.

to further darken the cabin during summer, we're trialing some nicely patterned contact (the stuff used to line shelves or cover books) on the inside of the hatch. so far works / lasts well...

cheers,

[RKsailsolo]

Originally Posted by er9

have you tried sanding the surfaces of the plexi and fiberglass before applying the 795? i usually laser etch or sand with #250 grit the entire area to be bonded. makes a huge difference in adhesion.

Abraded surfaces offer more substrate to adhere to. Abrasion gives the substrate a tooth that adhesives can bite into.

[RKsailsolo]

Originally Posted by chrisr

we use uv film on the inside of numerous windows and hatches - and it's super effective.

however i don't think the stuff we use would last on the outside. weather etc would get it off fairly quickly

of course there might be other (more expensive) stuff designed for the outside

incidentally, as a cheaper alternative to the sunbrella hatch covers, in our sleeping cabins we use silver duct tape. reflective so keeps the heat out, and darkens the room nicely.

to further darken the cabin during summer, we're trialing some nicely patterned contact (the stuff used to line shelves or cover books) on the inside of the hatch. so far works / lasts well...

cheers,

Exactly, blocking plastic surfaces from the outside is what I'm after.

[RKsailsolo]

Originally Posted by Bycrick

Clean the fiberglass or other surround. Then do it again. Then sand both surfaces, including the edge of the plastic with 220 wet-or-dry. Clean everything with 90+% alcohol. Let it dry. Leave an 1/8” around the window. I used matchsticks but the idea of small rubber disks sounds worthwhile. I used Dow 795 and, so far, it’s stayed leak-free until the plastic got so bad that I replaced it.

Excellent. Achievement of a successful bond is all about surface prep and then dwell time, I.e., letting adhesion build over time before letting the bond go back intso service. Surface prep is like application of PropSpeed during bailout. Get it wrong and you can predict failure.