Why is everyone stuck on Dow 795 When Cars use this?

[Island Time O25]

Most famous adhesive fail.

"There were problems with the innovative use of blue reflective glass in a steel tower: entire 4′ × 11′, 500-lb (1.2 × 3.4 m, 227 kg) windowpanes detached from the building and crashed to the sidewalk hundreds of feet below. Police closed off surrounding streets whenever winds reached 45 mph (72 km/h). Under the direction of Frank H. Durgin of MIT's Wright Brothers Wind Tunnel a scale model of the entire Back Bay and an aeroelastic model of the John Hancock Tower were built and tested in the wind tunnel to identify the problem. The research raised questions about the structural integrity of the entire building (due to unanticipated twisting of the structure), but did not account for the loss of the glass panels. An independent laboratory eventually confirmed that the failure of the glass was due to oscillations and repeated thermal stresses caused by the expansion and contraction of the air between the inner and outer glass panels which formed each window; the resilient bonding between the inner glass, reflective material, and outer glass was so stiff that it was transmitting the force to the outer glass (instead of absorbing it), thus causing the glass to fail.(c)

[coopec43]

Four of the cabin side windows on the yacht I am building are toughened glass and stuck on with Fixtech. The product was recommended by a crowd selling marine windows but I note the product is used elsewhere as well.

https://www.fixtech.com.au/

https://www.fixtech.com.au/distribut...ed-states.html

https://www.youtube.com/watch?v=ZuXGBqNsiZU

[tamicatana]

My SUCCESSFUL application of Dow 795, since 2016 and counting. Sub 30N latitudes. Applied @1/2 inch thickness, as per Dow instructions. QED, MF



Oops, almost forgot: successful application, since 2013 and counting:

[Palarran]

I have two hatches that are leaking. The original sealant was Sika. Dow 795 black appears to be nearly impossible to get right now. Any other options?

[boatpoker]

Originally Posted by Palarran

I have two hatches that are leaking. The original sealant was Sika. Dow 795 black appears to be nearly impossible to get right now. Any other options?

See post #26

[Palarran]

Originally Posted by boatpoker

See post #26

I don't see it available in black.

Anyone use the 3M 4000 sealant?
https://www.westmarine.com/buy/3m--4...76?recordNum=2

Also, because I have around 20 hatches sealed with this Sika, has anyone ever used a tool like this to get the old chalk out?
https://www.jamestowndistributors.co...ct-detail/3332

[SVTatia]

Originally Posted by boatpoker

See post #26

Boatpoker, how was the workability of this product for this application? Things like viscosity, cleanup, etc. and did you buy it in Canada?

[BenBowSirocco]

Originally Posted by Palarran

I have two hatches that are leaking. The original sealant was Sika. Dow 795 black appears to be nearly impossible to get right now. Any other options?

Mcmaster Carr. Bought some a couple weeks back anyway.



I have been working at boat shops for over a decade. Two of the manufacturers that I have worked for use the Sika system of primer+goo. The 3M stuff we were given by their application engineers for testing also required primer+goo and was generally speaking very similar to Sika in application and finish quality. Both had spectacular holds based on pull tests and pressure washer tests.

I understand the OP is having some frustrations with his application, but based on the post I saw with pictures of his windows, I am not sure that is a fair shake for the product. Those windows were huge and we dont really have the ability to know how he assured proper flex free fit of the acrylic, or what his spacers and resulting product thickness was- especially as it pertains to the installations uniformity of thickness. Other have pointed out that he did not follow installation instructions, but I would agree with him that that any window install can be a challenging project and any window install of that size- especially alone- would be nearly impossible.
On a humid/hot day you may begin to get skin glazing of the goop before you could even apply it evenly all the way around!

Sika and DOW are both RTV moisture activated products. In a dusty boat shop, we spray these products with soapy water immediately, for ease of smoothing, but also because it will skin almost immediately as a result and subsequently will not pick up the white dust.

I do not think it fair to completely bash a product that didnt work in your specific application using your chosen installation methods that has worked so well for so many others.

Keep us up to date on how your project turns out though!



Most manufacturers today that are using acrylic windshields on the center console hard top frames have all moved to VHB and VHB only.
The process that I have used with success on multiple projects, one going back 5 years is a combination of VHB and Dow. The VHB is stacked to the DOW recommended thickness (2 layers were enough to make 1/16", which is all that was required for windows of this size) and then Dow was applied on both cabin house and acrylic. Stick the window down, VHB makes the hold, follow up with a beauty seal around the edges and your done forever.

[BenBowSirocco]

Originally Posted by Palarran

I don't see it available in black.

Anyone use the 3M 4000 sealant?
https://www.westmarine.com/buy/3m--4...76?recordNum=2

Also, because I have around 20 hatches sealed with this Sika, has anyone ever used a tool like this to get the old chalk out?
https://www.jamestowndistributors.co...ct-detail/3332

My tool of choice is an oscillator, but with a carbide cutting tip. Its VERY easy to destroy things if you slip. So protect surrounding areas and work slow.

[tamicatana]

DeBond Marine Formula is awesome stuff. Use sparingly. x-acto #18 is my go-to for mechanical removal.

[Palarran]

Originally Posted by BenBowSirocco

Mcmaster Carr. Bought some a couple weeks back anyway.

Just finished ordering two tubes. Thanks.


Keep us up to date on how your project turns out though!

Absolutely. I won't get a chance to seal them for a few weeks. I've got a funny feeling that the two out of twenty leaking are just a harbinger of things to come.

Most manufacturers today that are using acrylic windshields on the center console hard top frames have all moved to VHB and VHB only.
The process that I have used with success on multiple projects, one going back 5 years is a combination of VHB and Dow. The VHB is stacked to the DOW recommended thickness (2 layers were enough to make 1/16", which is all that was required for windows of this size) and then Dow was applied on both cabin house and acrylic. Stick the window down, VHB makes the hold, follow up with a beauty seal around the edges and your done forever.

I sealed our large eyebrow window last year with VHB tape and chalked as you describe. The results are still new but I'm pretty confident it will last quite a long time. You know what is funny? I had a "professional" quote me $8000 to remove the window and re-bed it. I kid you NOT!! It did take us about two men two days to do the work but very happy with it. Now I'm preparing to do the other side when time allows.

Thank you for the info.

[argonauta1]

All I ever used was 3 M 5200. Worked fine

[sailortype]

here we go again....!

[clockwork orange]

My son and his girlfriend will be installing their new glass windows in their 42ft Simpson cat soon and they will be using the automobile windshield stuff. I am not impressed with Dow 795, I have done a lot of windows over the last 50 years and have had zero issues using GE Silpruf.

[sailortype]

I wish them good luck with that black muck; I hope they have some experience using it. They may wish they hadn't if they get it all over the place and end up with permanent staining.
Silpruf is a silicone sealant and should not be used on fiberglass surfaces.