Windows

Any see-through bits
mySerenity
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Post by mySerenity » Tue Mar 11, 2008 9:23 am

We start installing tomorrow and tried to have a look for some Forum info...and there's none. So here's the start. I'll attach a Poll too:



Have chosen Silpruf for the bonding agent with SS screws through oversize holes on at least a 2mm bed. Any other suggestions? Any thoughts from current owners who have problems and would do it a little different next time.



Glass has been deliberately left out of the Poll as many use a glass and another type combination. I am going Polycarbante and Glass.
James
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Bruce
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Post by Bruce » Tue Mar 11, 2008 5:06 pm

Can't remember where I got the following from, but I thought it was a pretty thorough explanation with some good tips:-



By Bob Norson

When we were rebuilding “WhiteBird” some years ago, I was told that new boats were being made with windows/ports held in with two sided tape and silicone. I was replacing the old glass with polycarbonate but there was no way I was going to use wimpy shit like two sided tape to hold her together. In fact, there wasn't even enough screws left from the glass bezels to satisfy so I went to work with drill and tap and bought boxes of 5 mil screws…. about 500 all up!

When finished it was a work of art and admired by all, zillions of shiny screw heads holding the dark tinted plastic against the neatly trimmed Black Sika Flex on sparkling white painted sole and combing. The only thing worse would have been a bunch of varnished teak!!

I got away with it for a long time because I am always careful on boat work and fussy of finish but something I've found about working on boats is this… PERFECTION IS ONLY 90% EFFECTIVE!

Besides Sika Flex not being up to the challenge (not the best anyway) of sealing plastic with the expansion tendency of “Lexan” or polycarbonate all those screws were an invitation to trouble. Some were bound to leak over time and they did. On a plastic boat that means you have a tiny leak. On a steel boat a tiny leak means you have a big problem eventually. As the water penetrates the sealant around the screw and begins to corrode the steel behind the plastic, the expanding rust scale wrecks the sealant against the plastic itself and … well you get the vicious circle idea.

I had three things to do; first was to repair the paint system, which on a steel boat deserves a couple pages of it's own. (I will be adding this info soon) Second was to find the right sealant which wasn't as easy as you might think. Lastly to mount the windows without screws and still make it look sexy….. the dreaded two sided tape

The window tape needs a relatively even surface to hold the plastic on. If there is more than gentle curves involved use Wattyl brand fairing compound between the primer and top coats somewhere to even things out. Unless you let it go too long the stuff sands fast and leaves a great surface. Besides the mechanical issue it will look better when done. The fairing doesn’t need to extend beyond the area where the tape will be. If the sealant is a few mill thicker in one spot than another, no big deal. The sealant hides the difference well. All the paints and the fairing compound mentioned are products I have experience with and believe are the best for the job. All of these products are available from Whitsunday Ocean Services in Airlie Beach, phone (07) 4948 1366. If you are doing your thing in Tasmania it will probably still be cheaper to order from them and pay shipping than buying local.

All the plastic boat people can stop laughing now. Since we all now have well painted even surfaces for our windows this is where you guys get to work as well.

READY STEADY GO!!

Cut your plastic to size leaving a 40mm (1 ½”) overlap (some say less but I work on the “safe” side) for your tape and sealant. I used a metal cutting blade on a jig saw running at moderate speed with good result. A less than perfect cut can be straightened out with a belt sander or file or whatever but don't polish the edge as you want silicone to stick to it later. Leave any plastic film in place on the plastic and note that Lexan has an “in and out” side. After cutting out you need to paint the area that will be the overlap facing in. Either use the plastic film that came with it or mask off with tape. I used a medical scalpel for shaping the film for masking. Xacto brand knives should work as well. You can get primers for plastic then coat with poly-U 400 but I found automotive exhaust paint to be very tough and grippy on the shiny plastic. (This was an insider trick I got from a lexan disributor!) Painting on the underside edges reduces UV that could get to the tape to degrade it but more importantly, hides all the stuff so it doesn't look shithouse. (Lexan brand polycarb is claimed to be UV proof anyway.) Black was the colour appropriate for my application.

Next…. The very important task of masking off the sealant can be done now or later. I chose early because I wanted to apply the window with some sealant goohed on the boat already. Some say that extra sealant isn't needed, they squirt it in after the window is fastened with the tape but because I was worried about lack of sealant and working time later, I put masking tape on the boat then held up the window and used a divider to mark off a line about 5mm over the size of the window. Once marked I carefully (so as not to penetrate the paint surface) cut a line with my scalpel and lifted off the excess tape. Now strip off all the plastic film or masking tape you applied for the painting of the window and apply a mask to the edge of the outside of the new window to protect it from the sealant. I just laid it down quick and sloppy, then ran my blade around the edge and viola.. done.



Next… 3M brand tape is known to be very good. It comes in one inch and ½ inch widths. I used two strips of ½ inch to make the recommended 1 inch total. The best holding 3M stuff has a red cover. There are others but I used the 3M that I found in Mackay. Apply the tape to the boat toward the inside of the 40mm overlap area.

Next……Now strip off the cover on the two-sided tape and optionally, squirt on a thin line of silicone under where the edge of the window will be but not to close to the exposed tape surface. When the window is applied you don't want the silicone to invade the tape. Raise up your prepared window and carefully…..oh so carefully put the window in place. You only have one shot at this. If it's wrong you are screwed, blued, stuffed and tattooed. Don't think you can move and slide, you can't. It's either right or get out the hammer and chisel. Assuming its right, use your palm to push hard to really set the tape to plastic.

Now that you are considering that stress, lets talk silicone! The right stuff is hard to find. You need a silicone of the correct colour (black in my case) with a neutral cure. If using Perspex you may get away with only a 20% + or- joint movement capability. With lexan or polycarbonate you need more because it's rate of expansion is greater. I found the right stuff at “Lincoln Sentry” in Mackay. It is Dow Corning brand, silicone # 791 with a whopping movement rate of 50%!. Schionning Marine also carries the right stuff. 3M also has a sealant intended for use with Lexan, consult your local dealer.

Next…. If you haven't already, mask off the outside now. (about 5-6mm from the edge of the plastic on a flat surface or to the edge of a rebated surface) Squirt a line of the silicone all the way around the outside edge. With a rubber glove covered finger, work the silicone into and under the edge of the plastic and finally smooth off the whole way round. Don't leave any holes or rough spots. Now carefully pull off the tape. Don't wait till it starts to set. Get it now. Rubber gloves are cheap at the supermarket so use plenty of em. Keep a bottle of methylated spirits and paper towels handy to wipe up the stray accidents.

DONE!I thanks to:

Brad of Blue line Boat Builders, Mackay. Brad got me started and even loaned some supplies. Thanks Brad.

Ian Cambell of “Vega 1” for tips on masking.

Brett of “Imagine” for general info and advice on when to remove masking.

Graeme of “Katani II” for the methylated spirit trick.







Masking off the window and aperture. I also used the scalpel for trimming the tape around the aperture but I have extensive experience with the tool. If you cut through the paint system accidentaly, you may create future problems. Another way to do it is to trace the window outline around the aperature and manually apply the tape about 5mm or 1/4" outside of the line. This can be tricky business on the curves and a narrower width of tape would help. Take time to do this step as neatly as you can because it is the one that makes the difference in appearance when finished.





Apply tape and strip off cover.





Apply sealent under where the edge will be and get ready for the stressful part!





Apply a bead of sealent all around, work it under and smooth off.





Carefully remove mask immediately.







Done!

In retrospect and additional notes;

This was done a year and a half ago and the windows have been perfect so far. Not one drop of water has leaked but I would do a couple things differently nonetheless. I think I would use only 1/2" (12mm) width of 3M tape this time instead of the double width that I did. I was concerned about the strength of the bond but I think the bond of the sealant is probably as good so I would increase the area of sealant. Because of the fairing I did around the aperatures, I wound up with a good thick bed of the sealant outside of the faired area and under the edges. The thickness of the bed is important. With the proper silicone I think a bed thickness of 2.5 to 4mm (1/8" + or -) for windows in the 300mm (1 foot) square size is more than adequate. The larger the window, the more the expansion, the thicker the bed required for success over time. Consult your supplier for recomended thickness of plastic. I used 3/16" (4.4mm) for the project shown.

For those wanting to do the ultimate job.... keep the two sided tape a little away from the aperature and prepare a mask for the inside of the window as well and apply sealant there to. Mechanically, I think this may be overkill but in some situations may be better looking and would keep contaminants off the inside edge of the tape.

If you think you can handle this project, expect to save thousands of $$$$ over the cost of a pro to do it, if you can find one that will do it properly. This is the favoured method of some of the premier production boat builders in Australia and world wide. But don't tell anyone........



There are a number of pics within the article, but I thought it a bit tedious to go through the pic upload process .

If anyone would like a copy of the original, just email me & I'll send it.

northerncat
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Post by northerncat » Tue Mar 11, 2008 7:22 pm

having used various brands of roofing and gutter silicone i can testify to the usage of the silpruf silicone for windows it has an amazing open time allowing you to take the much needed time to do a careful job knowing that the silicone isnt spoiled due to rapid curing

sean

mySerenity
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Post by mySerenity » Tue Mar 11, 2008 7:41 pm

Cheers Bruce

Sounds like Cruising Helmsman. A very similar article appeared in there a few issues ago.



Appreciate that Sean

An issue a friend had with Silpruf is the 'use-by-date'. He bought a box (20) to find that it was a few days after the expiry of the use-by-date and threw 50% of them out. For him, it would have been cheaper to buy a new box.



The use-by-dates are imprinted on the base and in the case of Silpruf, it has a twelve month shelf-life. Printed something like 09J******. The 09 is the date of manufacture and the J being the month of manufacture (J - 10th letter of the alphabet - October).
James
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jess

Windows

Post by jess » Wed Mar 12, 2008 6:02 am

I'm in the process of redoing my windows after 9 years of service. I used the method similar to that outlined by bruce, but using uv stabilized tinted acrylic and sikaflex products including the sikaflex uv black primer paint.



The windows loked great for the first three years until the bond between the acrylic and the sikaflex uv primer paint started to break down in the sun. I suspect the acrylic was doing the breaking down ,as witnessed on ones expensive deck hatches after a few years of exposure to the sun.



Anyway I kept the leaks at bay with the sikaflex gun for the last 5 years as I found it just about impossible to get the windows off in one piece to reuse ,as the bits that were still stuck were stuck well.



Ive been the silicone and bolt route on another cat ,and that sucks! for the reasons given in other posts ,so are keen to keep the same no bolt system.



Ive seen others try and keep the uv off the bond line using black signage nylon, and paint, but am unsure whats best. Any experence with these problems anybody



Regards Perspexed.

mySerenity
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Post by mySerenity » Wed Mar 12, 2008 8:06 pm

Jess
The windows looked great for the first three years until the bond between the acrylic and the sikaflex uv primer paint started to break down in the sun. I suspect the acrylic was doing the breaking down ,as witnessed on ones expensive deck hatches after a few years of exposure to the sun.
Great to hear from you again. There is a Cat in Scarborough Marina (Brisbane) at the moment who is complaining about this almost word-for-word, he used 10mm acrylic throughout and is screwed on. His leaks are coming from between the screwed areas and he too is pointing the finger at UV/Sikaflex breakdown. He also used black uv stabilised paint internally around the frame and this is all peeling away after five years, I suspect the latter being from heat though.



It is a pickle.
James
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Jim
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Post by Jim » Wed Mar 12, 2008 8:11 pm

Hi James, I haven't made my mind up as to the material I will be using for my windows, so I am not ignoring your poll.

Jim.

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Post by Smooth Cruiser » Thu Mar 13, 2008 3:52 am

I'm not sure what my windows are :oops: maybe Jim or Sean who have seen them and know what the various alterntaives look like might be able to say. What I do know is that after 7 years I have no leakage issues around the windows. The acrylic (?) is very weathered looking though with a permanent scuffed and faded look. Not terrible, but certainly starting to show it's age a bit. Also the sealant that was used (black) seems to be leaching out and leaving a slight staining below the window. This is not enough to be immediately obvious but on inspection of the white paint below all of the windows you can see a slight black staining that doesn't come off with boat cleaner.



As I say - I don't really know what products were used - but can offer these observations, hence this post may or not actually help people!!

mySerenity
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Post by mySerenity » Sun Mar 23, 2008 8:55 am

Well

They are almost all on, just awaiting the 316 hinges for the front windows. Paintwork appears to have turned out OK too. :D

James
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mySerenity
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Post by mySerenity » Sun Mar 23, 2008 9:05 pm

I'm not sure what my windows are maybe Jim or Sean who have seen them and know what the various alternatives look like might be able to say. What I do know is that after 7 years I have no leakage issues around the windows. The acrylic (?) is very weathered looking though with a permanent scuffed and faded look. Not terrible, but certainly starting to show it's age a bit. Also the sealant that was used (black) seems to be leaching out and leaving a slight staining below the window.
Smooth Cruiser

I am told by 'one-who-worked on your boat' that he thought they were acrylic and that Silpruf was the sealant. If it is acrylic, I am told that they can be polished back if scratched. Not sure if this helps.
James
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