Rebedding Fixed Windows on Hunter 380

[planoron]

Hello All,

First I want to thank everyone for all the info provided to us to get our boat in shape.

I am now going to pull the old fixed windows on the cabintop sides because of leaks and acrylic degrading. I will go ahead and post pics and info on this process for the archives. I was a custom glazier in a past career and the first thing I noticed is that the windows currently have screws holding them. This was my first red flag but since the windows are in bad shape they would be replaced so not an issue with the purchase. A great guy that works with boats was helping me and sure enough, the starboard window cracked at a screw hole. Tomorrow I will go out to pull the cracked one and plastic up while i cut new ones for both sides.

So here is the game plan and would still like to hear any input:

* I will pull the one window and use as template for the new dark smoked gray plexiglass. Cut and sand with a belt sander to get out any edge flakes and provide any bevel required.

* A thorough cleaning of fiberglass and possibly a light sanding where the adhesive will be applied. Fill screw holes and repair any affected coring.

* Dry set the new window and trace a light pencil line around the edge. Considering doing what another suggested and tape some blocking for the setting of the window. This will be a one shot deal.

* Bed the surface with 3m black vhb tape. Peel back the edges of the protective paper on the plexiglass and press in from the center out to the ends.

* Once set I will tape around the window and back fill with black Dow 795. Tool in, strip the tape out, drink cold beer till it cures. (could take awhile)

If anybody sees any glaring issues please let me know. Otherwise, I will try to get pics together with before and after.

Thanks

Ron

 

[Brian S]

You almost have it right.

Here's the article from SAIL mag: http://www.sailmagazine.com/boatworks/replacing-fixed-portlights

Note the article is pretty adamant about the thickness of the VHB so that it accommodates the differences in thermal expansion between plexi and fiberglass. I would definitely paint the plexi where it overlaps the fiberglass. You will see everything through the plexi if you don't, whether you use black VHB or not. Incidentally the VHB I found was grey. There is a Precision 23 in our club that has new windows, and whoever did that repair did not paint the plexi. You can see all the sealant. Looks terrible to me. Also, the plexi was maybe thinner, and it looks wavy gravy where they actually used the fasteners to pull the plexi down, which is a big no-no as far as the plexi cracking later. I dunno, maybe they used Lexan polycarbonate instead of Plexiglass acrylic? Not a big deal for you as you won't be using screws.

Mark your existing window on the fiberglass first before removing. It is exceedingly difficult to line up the new plexi when there's paper on it, and you can't see through it. It's good to have 2 people, one on the outside holding the window firmly in proper position to the cabin side, and one on the inside tracing the opening on the paper. I did I by myself with lots of masking tape.

Blocks stuck to the fiberglass on 2 sides of the window are mandatory, otherwise you won't get it properly in place in both X and Y location. I held mine into blocks on the top and back side of window firmly, then slid inwards to connect to the cabin side. I used hot glue to hold blocks in place, it's not hard to scrape off the hot glue that sticks to gelcoat afterwards.

You MUST sand down the gelcoat where the old adhesive was located. New Dow Corning 795 won't stick where the old silicone sealant contaminated the gelcoat, no matter what form of silicone remover you try. I scraped as much off as I could, then used Goof Off Ultimate aerosol to get it visually clean, then sanded. I sanded with a vacuum held next to the block to suck up old contaminated gelcoat dust as I sanded, and not grind it back in. I stopped and cleared the paper frequently.

The new windows without screws look great! I just hope I squeezed enough 795 in around the edges. Well, maybe I get 3 foot disease before too long, and I never find out how long the new window seals last? I can tell you that the original sealant was in excellent shape and fully adhered after 29 years. It was the spider cracks from the fastener holes that extended past the sealant and allowed water to drip behind the sealant. Just more proof that you ALWAYS countersink any hole drilled through fiberglass...

 

[Ralph Johnstone]

Nice Article ....................

You almost have it right.

Here's the article from SAIL mag: http://www.sailmagazine.com/boatworks/replacing-fixed-portlights

........................... in Sail magazine. However, I see that someone just had to insert one major screwup into the job.

Shown below is their reference to polishing the edges for whatever unknown reason. On my first replacement on a framed portlight, I didn't touch the edges after routering them with a template bit. They had a bit of a shine to them. I noticed a year later that, in one or two places, there was the beginning of a small separation between the 795 and the edge of the plexiglass right at that top 90 deg. angle. I redid the job but this time finished the edge of the plexi with 120 grit paper. No problem to date five years later.

The 795 does a good job of adhering to to flat polished surfaces but is less than perfect on that top point where the 795 and plexi meet on the edge..

 

[planoron]

Good Info.

Brian,

* I really like the idea of using hot glue for the blocks.
* I did notice the VHB tape I ordered was gray and was not sure if it hide under the dark smoke gray. Sounds like it will show through so here is a question for all.

What if I ordered another roll of the 3M VHB Heavy Duty Mounting Tape 5952 Black, 3/4 in x 15 yd 45 mil? This would overlay the 1/2" gray strip while adding very little space to fill. I would probably roll them together on my bench leaving the wax paper on the outside till I cut it in at the boat.


Ralph,

Good info,,,I was going to run the 120 grit over it just to clear the minute chips and flakes from cutting. Now, while I have it on the table it will be nothing to slap a 220 belt in and give it a once over

 

[njlarry]

Just did as you described. Came out great. Used DEI black silicone coating to black out the taped-gelcoated areas. Much easier and nicer thatn drilling!

 

[planoron]

Just did as you described. Came out great. Used DEI black silicone coating to black out the taped-gelcoated areas. Much easier and nicer thatn drilling!

Pics !! Need the Pics

 

[Steve Dion]

The screws are used to hold the acrylic in place while it cures. Once you have a bond, you can remove the screws and fill them with the 795.

Be sure the mask off all surfaces where they "may" come in contact with the 795 (inside and out).

 

[Brian S]

If I recall, the SAIL article was pretty specific about using 90 mil VHB, again to accommodate the different thermal expansion rates of the fiberglass, plexi, and 795.

To me it sounds like you are wasting time futzing about with different tapes, when you could just paint the overlap and be done with it. Mine look great, and I'm amazed I haven't taken any pics yet. Sorry about that.. IMO, the other boat I've seen that didn't paint the plexi looks like a$$...

Good Info.

Brian,

* I really like the idea of using hot glue for the blocks.
* I did notice the VHB tape I ordered was gray and was not sure if it hide under the dark smoke gray. Sounds like it will show through so here is a question for all.

What if I ordered another roll of the 3M VHB Heavy Duty Mounting Tape 5952 Black, 3/4 in x 15 yd 45 mil? This would overlay the 1/2" gray strip while adding very little space to fill. I would probably roll them together on my bench leaving the wax paper on the outside till I cut it in at the boat.


Ralph,

Good info,,,I was going to run the 120 grit over it just to clear the minute chips and flakes from cutting. Now, while I have it on the table it will be nothing to slap a 220 belt in and give it a once over

 

[planoron]

So I pulled the starboard glass today and taped the opening up. It looks like a 3/8" dark smoke gray Plexiglas. What I was surprised to find was a hard bevel across the top. Is this something you guys have found or was it something a PO did so they get a whole lot more caulking in?

 

[planoron]

Just so I am clear,,,What you did was bed the glass in and seal it. Then after it set a bit you taped off around the seal on the fiberglass, and then taped off the fiberglass to the middle side where you could see the mounting tape underneath the glass. Then painted the caulk and fiberglass all the way around and creating a weather barrier to boot?

 

[planoron]

Pic of the cracked glass and removed with just a scraping. Going to be a bear to get all that krap out

 

[Brian S]

No, what I did was remove old plexi. Cleaned up fiberglass and filled old fastener holes. Held new plexi to opening. From inside the cabin, traced the opening onto the paper of the plexi. Trace outside of window on cabin side. Tape off cabin side along window marking. Then, used sharp Xacto knife to cut the paper on the traced line. Peel off paper "rim" outside the cut line, exposing plexi. Painted with DEI black silicone coating, allow to dry. Removed other paper. Now, apply VHB tape along inside of black painted area. Apply bead of Dow Corning 795 structural adhesive to bottom of window, in case you can't fit caulk gun under window. Affix plexi and VHB to cabin side using positioning blocks. Caulk around window so that 795 fills gap between window and cabin, and also adheres window even more than VHB tape. Allow to cure. Pray during first strong rain storm

Just so I am clear,,,What you did was bed the glass in and seal it. Then after it set a bit you taped off around the seal on the fiberglass, and then taped off the fiberglass to the middle side where you could see the mounting tape underneath the glass. Then painted the caulk and fiberglass all the way around and creating a weather barrier to boot?

 

[Brian S]

Keep in mind my windows are surface mount, there is no recess molding in the cabin side. From your Hunter pics, it looks as if the windows are recessed into a bevel in the side of the cabin, potentially making it slightly more difficult to get 795 into the window. I smeared the 795 around the side of the window with a finger to smooth, then carefully pulled off masking tape before it cured and stuck to tape.

 

[twdevore]

We just did the exact process that Brian describes and the results are great. We went without any screws, we can always add if needed, and the new look is amazing. Next time, if there is one, we will go with larger plexiglass which would give more space for caulk as well as make the windows look bigger from the outside. Ours are surface mounted also. The process takes time, cutting, painting, taping...but it's worth the end result. The paint totally hides the tape and caulk as well as a section of fiberglass that we used to see that separates the inside "two" windows. (There are two cutouts but one piece of plexiglass covers both).

Wish I'd thought about hot glueing the blocks...

 

[planoron]

Well I just got a price to have the windows fabricated. $1,200 for the 2 of them. Ouch. $750 to buy the sheet and fab myself.

 

[TerryGufshoz]

I'm getting ready to remove both the front angled windows on my H29.5. The starboard one was replaced by a "pro" last year and whatever sealant he used is coming unbonded.
There's a slight curve in the window, so I assumed that I would need to use temporary screws to hold it in place while curing. I'm confused (not too difficult) about the use of the "blocks". Are the placed like tile spacers?

 

[planoron]

I'm getting ready to remove both the front angled windows on my H29.5. The starboard one was replaced by a "pro" last year and whatever sealant he used is coming unbonded.
There's a slight curve in the window, so I assumed that I would need to use temporary screws to hold it in place while curing. I'm confused (not too difficult) about the use of the "blocks". Are the placed like tile spacers?

You should bed with dow 795. The doublesided tape is unforgiving so you do a dry set with window. Make some small wooden blocks you can hot glue in place during the dry set and have it lined up. Then you can pull the window out to set your tape and the blocks guide it back into the correct position. Once you press the window to the tape, it is set. Then you can tap the blocks off and clean the glue off the frp with acetone. Then just tape and caulk.

 

[Brian S]

The blocks are somewhat like tile spacers.

I used them along the bottom and back side of the window (if space allows between the window and deck.) Blocks were about 2" proud of cabin side. I was able to fit the window into perfect position on the blocks, about 1" away from cabin side, then slide window along blocks into the cabin side where the VHB tape holds them in position.

Only had one chance to get it right, so I took a lot of positioning chance out of the equation with the blocks...

I'm getting ready to remove both the front angled windows on my H29.5. The starboard one was replaced by a "pro" last year and whatever sealant he used is coming unbonded.
There's a slight curve in the window, so I assumed that I would need to use temporary screws to hold it in place while curing. I'm confused (not too difficult) about the use of the "blocks". Are the placed like tile spacers?

 

[TerryGufshoz]

Just so I understand: the VHB tape is applied directly to the plexiglass surface which has been painted with the DEI black silicon coating. I know that it will look nicer, but is the bond of the VHB tape-to-DEI as strong as the VHB tape-to-plexiglass? Sorry to beat this horse anymore, but as everyone says...you only get one chance.

 

[Brian S]

Terry, that's what the Sail mag article said to do, how I did it, and another guy with a Precision did it. Although the Sail mag didn't specify the DEI coating, that's about the only silicone based coating we could find. (I hate it when magazines try to be "impartial." Just tell us the goddamn brand if it's good and proven!)

Also, when I pried my old windows off, the Dow Corning 795 was perfectly adhered after 30 years. So, between the VHB and the 795, I guess the only failure point will be the DEI coating.

No signs of problems after 1 season so far...