Replace acrylic portlights

[kbgunn]

I finally decided to address the acrylic windows that were sun damaged, crazed and leaking.

Outside-

Inside-

Several people recommended this resource from sail magazine: https://www.sailmagazine.com/diy/replacing-fixed-portlights
This youtube video seems like a independent validation:

So I dived in with irrational exuberance. After removing screws and running the putty knife around the seal from the inside, the acrylic pops off easy enough.

I dropped the old acrylic off at the local plastics fabrication shop to match the thickness, shape and bevel. I now turn my attention to surface prep while waiting on the new material. Does anyone have a quick and easy way to remove the old silicone based bedding material and get a proper surface for the 3M VHB (very high bond) tape to adhere? Also for the Dow Corning 795 sealant to stick.

I've thought of razor blade scrapers, wire wheel in a drill, 3M scrubber pad, repeated application of mineral spirits, and swearing. All of these seem like grueling work with questionable results. Any suggestions to get it done in an hour's time would be greatly appreciated. Also, any tips for installing the new material efficiently would be welcomed. Wind forecast for Saturday is 10-15 kts and I'd rather be sailing then scraping. B-)
KBG

 

[rpludwig]

from my limited experience you're on the right track...razor blade scraper, swearing works, add a thin putty knife, and a wide thin flat blade screwdriver to the equation...no eze way, but the results are worth the effort...others know better & will chime in....(silicone doesn't belong on a boat imo)...

 

[Bill Roosa]

Goof Off
Stuff is great at getting just about any kind of sealant off.

 

[SVMOONDANCE]

I'm not sure if this link is allowed but these work great! You have to buy the attachment for your drill to use them. https://www.amazon.com/3M-3M-18730-...7840765&sr=8-3&keywords=3m+roloc+bristle+disc

 

[kloudie1]

Whatever you use, be sure to tape a cover over the interior opening so you can control the dust and keep the interior cleaner.

 

[kbgunn]

I'm not sure if this link is allowed but these work great! You have to buy the attachment for your drill to use them. https://www.amazon.com/3M-3M-18730-...7840765&sr=8-3&keywords=3m+roloc+bristle+disc

Order placed for the bristle disc and holder. It will be here tomorrow. Great suggestion.

Why do a job by hand when you can use a power tool? More power!!

 

[kbgunn]

Whatever you use, be sure to tape a cover over the interior opening so you can control the dust and keep the interior cleaner.

Excellent. That's thinking ahead. I would be wasting quality sailing time with the shop vac cleaning silicone debris out every nook and cranny.

 

[SVMOONDANCE]

Use it with a LIGHT touch! They are designed for removing gasket material from metal so be easy with it and don"t push hard, let the tool do the work. As soon as you see the gel coat underneath the caulk showing through move on.

 

[CloudDiver]

I did this job on my C22, it only cost me $100 to buy the plastic and I cut myself. I did use 3M VHB tape but I shot myself in the foot with the process I used; The pro's will paint the inside edge of the window black because usually VHB tape is grey and you would see the grey tape through the plastic. Mine is as dark of a tint as they have available in Lexan but you can still see through it. The black VHB tape Andy uses in the Boatworks Today video is only available in 3/4" or 1 inch, mine was only 3/8 wide and Grey. Anyway, I wasn't sure about what kind of paint to use and I wan't confident the paint would stick to the smooth Lexan. So I though I was smart and I knifed a very thin coat of the Dow 795 to the bonding lip of the window. This seemed like it was going to work great until I discovered that the 3M tape will not fully stick to the cured DOW 795! I had to think fast so I ended up using just a few screws that firmly held the window in place (still using the 3M VHB tape as a gasket to maintain spacing) and I caulked in the 795 around the outside edge and then also on the inside. When it was cured I took the screws out and put just a dot of 795 in to fill the holes, it came out fine and the 795 is doing all the work. Note, my 'bonding edge' or perimeter of surface contact was 1.25 inch all the way around. Kinda overkill, I should have done it only 1 inch, but it still looks good.
Manually scrape off all the old silicone adhesive with a SHARP scraper, then sand. There are no common solvents that will dissolve cured silicone... not Acetone, not MEK, not Toluene, trust me. There is some stuff out there for that that DOW makes but its nasty and expensive plus I have no idea how it will react with gelcoat. A very thorough scraping followed by 80 grit sanding should get plenty clean for the VHB tape to stick very well. Don't worry about the 795, that stuff will stick to anything as long as its clean and dust free.

 

[greg_m]

from my limited experience you're on the right track...razor blade scraper, swearing works, add a thin putty knife, and a wide thin flat blade screwdriver to the equation...no eze way, but the results are worth the effort...others know better & will chime in....(silicone doesn't belong on a boat imo)...

Some loud music + swearing + elbow grease = job done!

 

[greg_m]

I found these items at my local hardware store. Thin brass wire brushes that mounted into the chuck of a rotary drill. Used carefully they make extreme short work of any rubber bonding/sealing compound. Use a variable speed drill to keep the revs low.

Used not so carefully they will remove skin as well! Don't ask...

 

[Gene Neill]

I did this job on my C22 ...

Luke, were you able to maneuver the caulk tube around in the cabin to caulk the inside edges?

The little forward windows on the Vega did not allow this, and I can't find Dow 795 in a small tube. Nor have I found an acceptable "extension tube". They may just remain uncaulked on the inside if I don't find something.

 

[CloudDiver]

Luke, were you able to maneuver the caulk tube around in the cabin to caulk the inside edges?

The little forward windows on the Vega did not allow this, and I can't find Dow 795 in a small tube. Nor have I found an acceptable "extension tube". They may just remain uncaulked on the inside if I don't find something.

I was able to move the gun around inside the C22. In the Vega, you could put the calk on a plastic board and knife it in. I had everything taped up and used a wet finger to smooth the bead. It wasn't the neatest job but it was effective (yet still messy).

 

[Mark Maulden]

I'm going through this now with six windows. I'm finding that Debond dissolves Sika 295 very nicely. They claim it will dissolve 5200 et al..

 

[catalanc]

I'm not sure if this link is allowed but these work great! You have to buy the attachment for your drill to use them. https://www.amazon.com/3M-3M-18730-...7840765&sr=8-3&keywords=3m+roloc+bristle+disc

On a separate thread, I have asked about removing an in hull transducer. One issue will be to remove the residual caulk/epoxy. These sound like they might work pretty well for that as well!

 

[Leeward Rail]

These sound like they might work pretty well for that as well!

We use them when removing gasket material and debris from surfaces when repairing intakes and doing head gaskets on motors (that don't require machining), rubber weather stripping glue, windshield install prep, etc etc.

They work great for any gasket/silicone/rubber material. They are much more gentle that a wire wheel.
They work great with aluminium and give a nice smooth finish if used correctly.
The 3M bristle discs are available in multiple different abrasive grades (50, 80, 120) for different tasks.

I have used them on fibreglass with great success.

FWIW, there a multiple different type of discs that work with a roloc style mandrel.
Sandpaper, bristles, scotchbrite surface prep, wool/polishing, you name it.

You can switch from disc to disc, in 5 seconds without removing the mandrel from the chuck. I rarely, if ever, find a need to use my wire brushes since I've started using the roloc style products.

 

[kbgunn]

What I have learned so far:
It is hubris to think there is a shortcut way to do sailboat maintenance.

I received the 80 grit Roloc bristle dic and mandrel and promptly assembled them.

At the boat, I tried to use the Roloc bristles to remove all of the silicone with no luck. The thick stuff was too stubborn. After trial and much error this is the method that worked best:
1) Use razor scraper to remove the bulk of silicone material.

To this:

2) Use putty knife to scrape the thin stuff left behind:

3) Used the flat blade screwdriver suggestion to get the remaining bits:

4) 80 grit on a palm sander finishes the task

Maybe could have skipped the screwdriver step and went right to sanding, but that might have clogged the sand paper quicker. Each opening took 45 mins so the whole job was 3 hours. Just waiting for the new windows to be finished at the shop.

Gene was asking about applying 795 to the inside joint. I will want to do this too. I haven't worked with 795 so I don't know how thick it is.....could some be placed in a ziploc bag of appropriate thickness and piped into the joint like frosting a cake? Then finish with a light finger touch. Just thinking out loud.

Also, I read somewhere to paint the inside edge of the acrylic with high temperature black spray paint to mask the VHB tape and adhesive that may not fully cover the fiberglass. Has anyone done this? I don't want a poor bond.
Thanks all!
KBG

 

[Hayden Watson]

I would still suggest using a silicone removal solvent such as this. http://www.dowcorning.com/DataFiles/090276fe8018f115.pdf Sanding it will leave particulate residue that will cause the new adhesive to not stick.

 

[Gene Neill]

Also, I read somewhere to paint the inside edge of the acrylic with high temperature black spray paint to mask the VHB tape and adhesive that may not fully cover the fiberglass. Has anyone done this? I don't want a poor bond.

I considered that when I did my Albin Vega's windows: https://forums.sailboatowners.com/index.php?threads/plexiglass-window-thickness.182638/

I elected not to, based on lack of 100% faith in the three different bonds involved. You'd have to absolutely trust the spray paint to bond to the gel coat, and you'd have to equally trust the VHB and DC795 to bond to the spray paint. I personally do not trust any of the three.

As it turned out, you can't see the tape through the 1/4" smoked plexi anyway.

 

[BigEasy]

In the September Practical Sailor, several products were listed as "2017 Editor's Choice products". One of the products is
RE-MOV Silicone & Adhesive Remover. It mentioned that "old silicone can become embedded in the pores of gelcoat and wood, making it impossible for anything to bond--a real problem when replacing lenses on hatches or ports" The article further stated that Re-Mov remover was the most effective overall for removing silicone caulk residue. Two applications were necessary for complete removal.