Sika be dammed...and new users be warned

[razamataz]

Hi all

after 2 yrs from replacing our hatches and portholes acrylic glass, it seems all the sika 295UV is debonding forming leaks....arghhh
we did an extensive research as to best materials, procedures, cleaning and prepping to no avail. (Yes we didnt use primer...couldnt get it)
Lastly after reading this thread https://www.cruisersforum.com/forums...-a-294320.html
I also saw one thru hull fitting with gummy wet sika on the inside that never cured - beneath it it did cure but this is after left to cure for several months in the boatyard and additional 2 yrs of cruising

All this led me to believe Sika should be banned from the marine world -waste of time and money

We now have to rebed our hatches\portholes and i seek the wisdom of the forum...from search results is see the following
1. Dow 795/ GE silprof2000 and 3m 4000 silicone (with or without VHB tape)

Our Hatches are 60x60cm 10mm acrylic with I believe alot of thermal expension that destroyed the Sika, but so are the smaller portholes with thier 8mm acrylic
I wonder if my plan of using VHB tape on face of the hatch\portholes that sits flat against the acrylic and then filling the edge gap with the above materials will prove to be a lasting solution?
How will the sun act on the vhb tape?

I am attaching pics of the hatches and portholes - you can see the debonding

Not looking forward to this Job

[razamataz]

Forgot to mention we are in Europe so Dow/GE materials are hard to get...the Europeans like using environmental friendly materials that make you use more money, time, effort and waste for the planet by doing the same job over and over....

[svlindalee]

The OP in the thread didn't follow instructions, and you don't mention what solvent you used. That's critical.

[razamataz]

Originally Posted by svlindalee

The OP in the thread didn't follow instructions, and you don't mention what solvent you used. That's critical.

the frames were cleaned in Acetone and the acrylic in mineral spirits / Iso alcohol

[Franziska]

Sorry about your predicament.


One thing I noticed though, you did not apply an exterior UV protection to your bonding surface.
This protection can either be screen printed or painted with two component polyurethane or be a black UV protection tape


UV goes through the glass and breaks down the bond between glass and Sika adhesive.


See here & attached.
Yellow is the Sika adhesive in the attached screenshot.


https://sommerfeld-thiele.com/file/s...manual-eng.pdf


Still interested to hear if the DOW material doesn't require this.

[svlindalee]

Originally Posted by razamataz

the frames were cleaned in Acetone and the acrylic in mineral spirits / Iso alcohol

Acetone prevents curing of sikaflex

[Tupaia]

SSG4000 Structural Glazing Silicone is readily available in UK and most places will ship to Europe. Installed my 12 wraparound Acrylic windows with it 2011 still good. All my hatches replaced after 20 years have been fitted using AquaMate silicone the stuff glass fishtanks are made using. Still some prep (cleanliness) required but ensure both surfaces are covered before bringing them together. Don't forget to use foam beads on adjoining panes as sealant will only stretch in 2 directions not 3.

[Greatest Lakes]

VHB tape doesn't seem to have issues with light, but I do seal the edges with silicone.

The Newfound metals windows I have done use butyl tape, more like a rope. Around the inner part of the frame, and a quality outdoor silicone on the outer part of the frame. I have found that the silicone designed for homes doesn't shrink quite like much of the marine stuff does. Boatlife seems terrible for this. Sealing anything on a boat, don't be afraid of using too much. Tape the portions you don't want sealant on, and go to town on the rest.

[Franziska]

Originally Posted by Greatest Lakes

VHB tape doesn't seem to have issues with light, but I do seal the edges with silicone.

The Newfound metals windows I have done use butyl tape, more like a rope. Around the inner part of the frame, and a quality outdoor silicone on the outer part of the frame. I have found that the silicone designed for homes doesn't shrink quite like much of the marine stuff does. Boatlife seems terrible for this. Sealing anything on a boat, don't be afraid of using too much. Tape the portions you don't want sealant on, and go to town on the rest.

If you install fittings or anything else on a boat with Silicone, be prepared for thousands of pinholes on your next paint job. A tiny amount of cured silicone on your sanding pad and it will be nicely distributed over your deck & hull causing trouble when painting.

[razamataz]

we didn't shield the sika from uv as we used sika295UV, (Uv resistant) I must admit sika manuals are all over the place and not summarized in one final document.
all hatch manufacturers are not using paint, uv barrier tape to protect the adhesive/sealant....so what are they using?

nothing about acetone and sika...and acetone evaporates quickly

didnt want to use silicone as opinions went against it, but maybe that is the proper material to work with....I dont plant to use it elsewhere on the boat

[thinwater]

Originally Posted by razamataz

Hi all

after 2 yrs from replacing our hatches and portholes acrylic glass, it seems all the sika 295UV is debonding forming leaks....arghhh
we did an extensive research as to best materials, procedures, cleaning and prepping to no avail. (Yes we didnt use primer...couldnt get it)
Lastly after reading this thread https://www.cruisersforum.com/forums...-a-294320.html
I also saw one thru hull fitting with gummy wet sika on the inside that never cured - beneath it it did cure but this is after left to cure for several months in the boatyard and additional 2 yrs of cruising

All this led me to believe Sika should be banned from the marine world -waste of time and money

We now have to rebed our hatches\portholes and i seek the wisdom of the forum...from search results is see the following
1. Dow 795/ GE silprof2000 and 3m 4000 silicone (with or without VHB tape)

Our Hatches are 60x60cm 10mm acrylic with I believe alot of thermal expension that destroyed the Sika, but so are the smaller portholes with thier 8mm acrylic
I wonder if my plan of using VHB tape on face of the hatch\portholes that sits flat against the acrylic and then filling the edge gap with the above materials will prove to be a lasting solution?
How will the sun act on the vhb tape?

I am attaching pics of the hatches and portholes - you can see the debonding

Not looking forward to this Job

Sika (any polyurethane) will fail without primer. The UV attacks the bond from the underside. Yup, tested this on panels. It was not thermal expansion. This does not happen to DOW 795.

[thinwater]

Originally Posted by razamataz

we didn't shield the sika from uv as we used sika295UV, (Uv resistant) I must admit sika manuals are all over the place and not summarized in one final document.
all hatch manufacturers are not using paint, uv barrier tape to protect the adhesive/sealant....so what are they using?

nothing about acetone and sika...and acetone evaporates quickly

didnt want to use silicone as opinions went against it, but maybe that is the proper material to work with....I dont plant to use it elsewhere on the boat

Nearly all US builders use DOW 795.


When you install, mask 2" around the window. Easy. No silicone on the gelcoat. I've repainted boats with silicone seals. No problems. Be neat with the silicone. Don't sand the silicone. If you must remove silicone for painting, use a special silicone-specific remover to break the bond down. No problem. DSR5.

[CarlF]

In the US I believe most people now use Dow 795 for mounting acrylic to fiberglass on boats -- except for warranty repairs if the builder requires the use of Sika. I've never heard of anyone unhappy with 795. It is beyond me why so many European and South African builders cling to Sika given the large number of warranty repairs they have to pay for.

It is carbon neutral with Green building certification.
https://www.dow.com/en-us/pdp.dowsil....html#overview

I've heard that it is harder to get in Europe. I would look at building and glazing suppliers rather than marine suppliers as it is primarily used on buildings.


1. Dow 795 does not require or even recommend a primer on fiberglass to acrylic

2. It is designed to hold large commerical building glazing to frames with no mechanic fasteners. It is wickedly strong, less messy to work with, tools easily, not sensitive to temp or hummidty during application (a big Sika problem).

3. The two major cautions. a) as with Sika the bead must be at last 1/4" thick so it can stretch during the expansion of the acryic in sunlight. Acrylic and fiberglass have different coeficients of expansion. You need to either use 1/4" foam weather stripping tape or little plastic tower to hold the acrylic away from the fiberglass while it cures b) the expiration date printed on the tube is not long. Never use a tube past its expiration date.

[Marathon1150]

Originally Posted by razamataz

didnt want to use silicone as opinions went against it, but maybe that is the proper material to work with....I dont plant to use it elsewhere on the boat

We replaced all of our fixed portlights with thicker Lexan than came with the boat, before heading offshore. I followed advice from several sources to use silicone. The person helping me change the portlights argued against it but I persisted. He redid his boat with Sikaflex (not sure which type). One to two years later all of his portlights were leaking and needed to be redone. We are now nearly 10 years down the road and no leaks.

IMHO there are no perfect sealants. One of several possible disadvantages of silicone is that many other sealants and glues do not stick to it, even silicone. A slight residual film of silicone will prevent other sealants and things like VHB tape from developing a strong bond. We learned this when we installed portlight cowlings that use VHB tape for mounting. Getting the silicone off to a bare surface without sanding is challenging.

[AndyOz]

Originally Posted by svlindalee

Acetone prevents curing of sikaflex

I would have thought acetone would have flashed off seconds after wiping. None left to interfere with Sika.