Window Replacement

[bawlmer]

I few months ago I purchased a set of replacement windows from SBO for my Catalina 270. I checked them for fit yesterday and everything was fine. There is a slight forward to aft curvature in the window opening. Window is flexible enough so no problem there either. When you install the new window you will have to apply pressure to the forward and aft sections of the window to maintain the curve while the cement dries sufficiently to hold the window to the curved side of the boat superstructure.
I am reaching out to the group to see if any one has done this before and if so what did you do to hold the ends of the window in place while the cement cured. The instructions suggested "sandbags' or "tape" but I do not think that will exert enough force to keep the ends of the window attached while the cement is drying. Please share your experiences or success stories.

 

[rgranger]

Fantastic question. I can't wait to hear other's answers. A thought that came to my mind was to park your boat in a garage or near some wall and then use a pole (broom handle) wedged against the wall on one end with the other end on the corners of your window. You could dry test the idea to see if it will work before you commit with the cement.

 

[duality]

i used strips of oak between my fairlead track and grab rails, then i placed wedges between the strips and window to maintain the curve.
mike
catalina 400

 

[bawlmer]

I was playing around with a line yesterday with the goal of having it follow the curve of the window and using blocks placed at the ends but I did not have the right connections on the boat to lay and tighten the line correctly.

 

[dziedzicmj]

I know of some people using the VHB (Very High Bonding?) tape to attach windows. It bonds immediately.

 

[Ralph Johnstone]

Use @dziedzicmj's idea of the VHB tape or use temporary screws as used in Marlow Hunter production fixed port windows from the factory. After the sealant has set for about a month, the screws are removed and filled with black 795, which is almost invisible. When you look at the width the 795 has to set through, you see why a month is required.

If there is a greater amount of curvature, use permanent black SS screws and they are not noticeable from more than a few feet away. Allow for differential thermal expansion in the holes if the screws are to be permanent.

A word of caution on the Catalina instructions, do not use them. I saw a write-up some time ago where a fellow described the instructions as so insane, they had to be a hoax. He had gone off the deep end trying to use boards and sand bags to hold his window in place. Everything had eventually slipped and he had black 795 smeared over his side cabin. On his second attempt using this method, everything held but when he took the restraints off after a few days, the 795 let go and the window started opening up after a week later.

Everything is good until para. g. and h. and then it goes to hell in a hand basket with boards and sand bags sticking out in every direction. All you need is Moe, Larry, and Curly, and you're good to go.

Look up "portlights" in the archives and you will see some good ideas on installing these.

 

[duality]

i used the Catalina instructions and they worked perfectly!!! 5 years later no leaks. and no screw holes, who would want screw holes on a Catalina?

 

[bawlmer]

i used the Catalina instructions and they worked perfectly!!! 5 years later no leaks. and no screw holes, who would want screw holes on a Catalina?

Mike. The reason it worked perfectly is because you used wooden struts to securely hold the windows in place. I need to figure out how to apply that fix to my boat. The instructions are helpful until they get to how to hold the windows in place and that is where they go completely off the rails.
As far as tape goes I cannot believe they make tape strong enough to hold the ends in place without ripping off your gelcoat. Sandbags are straight up insane. Also there is no way I will ever put screws in those windows.

 

[dziedzicmj]

As far as tape goes I cannot believe they make tape strong enough to hold the ends in place without ripping off your gelcoat.

The tape holds on to the same gelcoat as the glue does, so if the glue works, the tape would to.

 

[Ralph Johnstone]

Also there is no way I will ever put screws in those windows.

Aw, c'mon !

Even if the holes are nearly invisible after the screws are removed and the small holes filled with black 795 ?


Even when it looks this good with your nose pressed up against the glass ?

 

[Project_Mayhem]

VHB is pretty awesome. It's being used for things like bonding trailer skins together without rivets. It appears to be pressure sensitive and this article backs that up by stating that 15psi of pressure helps with initial surface contact adhesion. If youre dealing with something that needs a lot of strength the following should be noted:

"At room temperature approximately 50% of ultimate bond strength will be achieved after 20 minutes, 90% after 24 hours and 100% after 72 hours. This flow is faster at higher temperatures and slower at lower temperatures. Ultimate bond strength can be achieved more quickly (and in some cases bond strength can be increased) by exposure of the bond to elevated temperatures (e.g. 150°F [66°C] for 1 hour). This can provide better adhesive wetout onto the substrates. Abrasion of the surfaces or the use of primers/ adhesion promoters can also have the effect of increasing bond strength and achieving ultimate bond strength more quickly."

https://3m.citrination.com/pif/001342?locale=en-US

 

[Ralph Johnstone]

"At room temperature approximately 50% of ultimate bond strength will be achieved after 20 minutes, 90% after 24 hours and 100% after 72 hours.

The one thing that concerns me is "how does the adhesive strength stand up after years of UV radiation exposure coming through the acrylic ?"

It's being used for things like bonding trailer skins together without rivets

This would be a worry free application as there is no UV getting to the VHB.

 

[FastOlson]

Several boats in our moorage have had all of their large/long fixed ports replaced. O'Day 322 and a C&C 34. In each situation the installer used pieces of wood to force them down, and those "struts" were secured to lifelines. After a week or so all of the "clamping " parts were removed. Kind of tedious, but not technically difficult.
I replaced all four of ours a number of years ago, and our design does use ss pan head screws around the perimeter. Further, the screw holes are also slightly over-drilled.
Strong, and a "belt and suspenders" approach. Our boat was designed and built for ocean passages.
Everyone that uses the 700 series adhesive seems to really swear by it, so it much be the right choice -- most boats have some curvature, proceeding down the cabin side, and the flat port lens does not like to bend.
I used a product called "LifeSeal" (black) from the Boatlife company. Still zero leaks after well over two decades.

One of bit of wisdom I received from an experienced boat wright, was to "float" the new lens on a one eighth inch layer of adhesive. This allows the lens to expand and contract without breaking the bond to the cabin side. If you look up the expansion rate for Lexan or Acrylic, you will see why.
Easy way to allow for this is put some tiny plastic 'spacers' into the new sealant when you shoot it. Then when you force the lens down, it will not force out all of the sealant layer. Easier if you have screws -- used some small O rings around each screw before you dry-fit, then place a temporary toothpick in each screw hole, and then shoot the sealant.
Use a lot masking material. A lot. More than you might at first imagine.

And, sand the adhesion area of the gel coat with some 80 grit, and clean it with solvent -- only abrading the actual strip of FRP where the new lens will cover.
Have fun!


ps: the updated use of double-sided tape referenced in the video looks interesting. It would be nice to see it done, in person.

 

[Project_Mayhem]

@Ralph Johnstone
If the tape is only there to keep the window in place while the adhesive is setting then it doesnt really matter. As for trailers, Im guessing that the only part exposed to the elements is the very thin edge. This document states that all VHB has excellent UV resistance: https://www.bindingsource.com/images/Customer-files/HowtoUseVHB.pdf

The article I posted earlier said that heat will accelerate bonding time. Ironically enough, I've used a hair dryer and floss to remove emblems. I guess it increases the viscosity of the adhesive

 

[Ralph Johnstone]

If the tape is only there to keep the window in place while the adhesive is setting then it doesnt really matter.

@Project_Mayhem
Thanks so much for digging up that product spec showing the resistance to UV. Maybe I can now sleep a little better knowing that.

HOWEVER, I have to disagree that the only purpose of the tape is to "keep the window in place while the adhesive is setting". Applying VHB tape behind the acrylic would prohibit the the use of 795 back there. Getting 795 on the VHB would immediately eliminate its adhesive adhesive properties and turn the whole thing into a slippery mess. And everybody goes flying up, down, and sideways from there. If you use the tape, the only 795 would be that which is finally injected into the edge as shown in @billjoye 's video. Therefore, the tape supplies most of the holding power with only a small amount provided by the 795 along the edge.

Any way you cut it, vastly superior to using sand bags, ropes, forms, restraints, trusses, and timbers to hold everything in place until the 795 sets.

 

[Project_Mayhem]

@Ralph Johnstone Do you mean that the two adhesives are chemically incompatible?

The BoatWorksToday video uses VHB on a boat that has a large lip to secure the window to. Perhaps that's the key to success?

 

[rgranger]

I really enjoyed @billjoye 's video that he posted. I also watched a few more on that same youtube channel. If you are contemplating a port replacement, I suggest you watch that video.

 

[Project_Mayhem]

I just discovered this little piece of info:

"Because the 3M™ VHB™ Tapes are sticky all the way through use of a lubricant, such as soap, will make the job easier."

I believe this means that you can apply a layer of soap to allow VHB to be repositioned for a short amount of time. I know this is a common technique in the signage industry when applying vinyl. This might alleviate the problem of "once it's on it's stuck" that is warned about in the BWT videos. I assume that excess soap would need to be cleaned before laying down 795

 

[agprice22]

I like Andy at Boatworks Today. I was cringing when he mentioned silicone. He needs an assistant to do the taping!
I used 795 and screws to hold my fixed lights while they bonded. If I ever remove them again, I will try the VHB.

 

[bawlmer]

"At room temperature approximately 50% of ultimate bond strength will be achieved after 20 minutes, 90% after 24 hours and 100% after 72 hours. This flow is faster at higher temperatures and slower at lower temperatures. Ultimate bond strength can be achieved more quickly (and in some cases bond strength can be increased) by exposure of the bond to elevated temperatures (e.g. 150°F [66°C] for 1 hour). This can provide better adhesive wetout onto the substrates. Abrasion of the surfaces or the use of primers/ adhesion promoters can also have the effect of increasing bond strength and achieving ultimate bond strength more quickly."

Good grief. It seems the VHB tape needs more management than the adhesive itself.