Flush mounting tinted acrylic windows

[Smier]

I posted this in another forum, but it doesn't have the traffic that we get on this board, nor the expert technical advice we have all come to know and love so much...  This is about my Starwind 22, but the info is generalized for fiberglass boats.  I'll be curious what you guys think:






I have been doing a lot of research into replacing the windows on my boat. Leaking is a big factor in my decision making, followed by the cost of either rebuilding or replacing all 7 windows/ports on my boat. After weeks of searching and reading the positives and negatives, and weighing all the different options, I have decided that I am not going to rebuild my existing windows. They leak, the exterior frames have cracked, several of the acrylic lens have cracked, and there really isn't much left that is salvageable...

I am going to have my local glass company cut new windows out of 3/8" or 1/4" dark tinted acrylic using templates that I will will create from my original broken window frames, and have them bevel the edges for a factory look. Then I plan to mount them using only an adhesive like Dow's 795. That's right, NO SCREWS OR BOLTS!!!! It sounded crazy to me at first also, but the more I've researched, the more I like the idea!

Dow 795 Info:

http://www.dowcorning.com/applications/search/default.aspx?r=264en

Here's a few links if you are interested in such craziness:

http://sailquest.com/ottawa/windows2.htm

http://www.thecoastalpassage.com/windows.html

http://www.cncphotoalbum.com/doityourself/portlight_replace/page01.htm

http://svmomo.blogspot.com/2009/12/replacing-boat-windows-polycarbonate-ie.html?m=1

And a video of a guy using an overpriced kit($1500), to do exactly what I am talking about:

http://youtu.be/xo43sWYo5oY

I will be getting an estimate of what it will cost to have the windows made, and if it is too high, I will just make them myself! The acrylic sheet is fairly easy to cut and bevel, and It looks like with shipping and tax, all the materials would be under $150. I think it will really update the look of the boat! The more I have researched, the more I like the idea of this. There is only one possible place for it to leak, and the reviews of the Dow 795 in this application are fairly impressive.

[brackish]

That's interesting need a report on how it comes out.  I did similarly on my Columbia 8.7 which had frameless ports mounted on the INSIDE.  What was that designer thinking???  The hot sun on the ports expanded the material differentially, the portion exposed hotter than the portion that overlapped the inside of the hole, consequently the material worked cyclically and leaked constantly.  Surface mounting new polycarbonate on the outside solved the problem.  However, I was not brave enough to go with just adhesive, used machine screws with washers and nuts hidden by the inside trim. 

Here is what they looked like after the job.  I did make them myself, bought a sheet of the material, it works easily with common woodworking tools, used a table saw, band saw, jointer and router to do the job.  very easy, also reglazed my forward hatch at the same time.  I ran into the current owner about twelve years later, and my work was still leak free.

[wes]

Brackish - I've seen that photo on your previous posts and every time it takes my breath away. Just an amazingly beautiful paint job.

[Craig]

You might want to read Don Casey's (the "Dean"of boat maintenance) article on sealants in the current issue of Boat US magazine prior to embarking on your project. I am skeptical of relying on an adhesive alone to secure your port lights. Not saying it couldn't  work, just that that you are asking a lot of the adhesive/sealant. 3m 5200 for example is an extremely strong adhesive but not a great sealant(according to Casey)because it has a relatively low elongation factor and will leak before the bond fails.Just a thought and worth what you paid for it!

[Smier]

Yes, from what I have read trying to use something like 5200 for this job may actually cause the acrylic to crack as the panels  shrink and expand at different rate than than fiberglass.   The more I read up on this the more I believe it will work, especially considering this is exactly the way many new production boats are done. 

[NateD]

Sometime production builders choose materials and construction methods on cost and ease, not on quality, longevity, and good foresight.

Personally, I would put some screws in, but I've never created fixed lights before. I image the larger the light, the more potential expansion and contraction, so from that perspective, maybe it will be fine on a Starwind 22. Then again, deck fittings bedded in 5200 don't move much either, but over time they end up leaking. I'm still thinking that mechanical fasteners and a good sealant is going to be better than just an adhesive/sealant combination.

[brackish]

Wes, thanks, I did it with Dupont Imron mixed to a Hatteras white color.  Has about three times the longevity of gel coat without the maintenance.  Fairly easy to spray, need good protective equipment for cat poly.  The hull has been finished in this picture, but the topside was just primed, then done later. 

On topic, the forward hatch was sent to a metal stripper, then primed with zinc chromate, then satin black finish.  With a new polycarbonate panel, it looked brand new. Bomar sent me a couple of hardware items gratis.   A good thing to do while you are redoing ports.

I will say the polycarbonate did tend to fade and lose it's visual clarity after quite a few years as mentioned in one of the discussions, however, I was after strength and leak free.  It did achieve that, and the material in sheet form was cheap enough to redo every five years or so if clarity was desired.

On the subject of adhesive only, some time ago I was remodeling my kitchen, and taking my first stab at fabricating solid surface.  After finishing the counter fab, I was going to install an undermount stainless steel double sink.  This is done by gluing studs with perforated flanged heads to the bottom of the counter top so that clamps can be installed to hold the sink flange.  Silicone adhesive sealant is used between the sink and the bottom of the countertop.  I was concerned about the spacing of the studs so I asked a pro licensed solid surface installer I knew about it.  He gave me the spacing he used, but said don't worry about it, just make sure you pull the sink up evenly and get an even distribution of the sealant.  After the sealant is cured, you can actually take the clamps off if you needed to, it will hold just fine.  I said " you mean with both sinks full of water and a load of pots and pans it would hold"?  Forever and ever he said it would take about twenty times that weight to break that seal, I've actually tested it.

[Smier]

   I just ordered all my materials, I decided to just make them myself since I have most of the equipment already.  $93 shipped for a 24"x48"x.250" sheet in Dark Tint, and $37 shipped for 3 tubes of the Dow Corning 795 adhesive.  I may order a sheet in 3/8" thickness after I experiment with the 1/4".  My concern with using the 3/8" right away was making sure I can conform the acrylic to the shape of the deck.  My windows are actually quite small, so I'm not as concerned about the thickness like I would be if I were dealing with a larger opening.  Even if I end up going with the 3/8" sheet, I'm still at roughly the cost of buying ONE window assembly.  Does this qualify as a low buck project?

   I'm looking forward to checking out that article, others have mentioned that some boat manufacturers are using an adhesive tape in conjunction with a sealant such as the Dow 795.  From what I can determine, they are only doing this because the tape provides a uniform mounting thickness between the hull and the acrylic lens for the adhesive to be applied evenly.  I really don't like this idea, and feel it is really only an aid to mass producing boats on a production line.  I enjoy working on things, this is a hobby of mine so my time is free and the only rush is to stop water from doing any more damage to my boat.  Instead I will use some type of small spacer(still to be determined) on the inside of the boat, that I will remove before the adhesive fully cures.

  I will use mounting screws if I have to, but I'm going to try really hard to avoid it if I can.  Once the adhesive has set, the screws really aren't doing anything, and I view every screw hole as another potential leak or a potential cracking point for the acrylic lens.  Believe me, until the other day I thought this was a completely crazy idea!

Brackish, do you have any links to a write up on your boat?  I'd love to know more about it...

[Allure2sail]

Sometime production builders choose materials and construction methods on cost and ease, not on quality, longevity, and good foresight.

Personally, I would put some screws in, but I've never created fixed lights before. I image the larger the light, the more potential expansion and contraction, so from that perspective, maybe it will be fine on a Starwind 22. Then again, deck fittings bedded in 5200 don't move much either, but over time they end up leaking. I'm still thinking that mechanical fasteners and a good sealant is going to be better than just an adhesive/sealant combination.

Hi Guys...
Interesting remark about the expansion and contract of the acrylic. When I replaced all the glass in my ports the gentleman who sold me the materials told me not to make them a tight fit in the frame due to expansion in the summer heat. He said that if it did not have the clearance it needed that it would distort instead. The acrylic was bedded in the frame with some stuff that is black and used in car windshield and comes in strips. It never gets rock hard and allows for the expansion and contract but keeps its seal. Never have had a leak but the last window I put in and sealed with the black stuff was a tighter fit than the others and guess what, on a hot day it gets a little bit of distortion in it. It is only noticeable if you look at something with horizontal or vertical edges in it, other than that it is not noticeable. The acrylic inserts were cut to shape using the internal retainer flanges as a template and then the edges were filed by hand for the needed clearance...time consuming. Job came out great and the tint gives me some privacy.  Good luck with your project. I will go measure what thickness I used on some left over pieces and let you know what it was.
Bruce
S/V Allure

[EclipseGuy]

I had a hunter 326 a few years back and it had a leaky window. I ended up having to re-seat the window and after doing a lot of research I decided to use Dow's 795. I bought the Dow product from a local building manufacturing company.

The windows on the Hunter were not bolted into place, but were just held into place by adhesive (to allow for expansion), so I followed the same idea and just used the Dow 795  and I did not use any bolts or screws. It seemed to hold up as it should.

- John

[brackish]

Brackish, do you have any links to a write up on your boat?  I'd love to know more about it...

No, not on that specific boat.  It is a 77 model, I owned it from 1980 to 1996. It was designed by Alan Payne, wonderfully done (except for the recessed ports).  It was the first of the wide body boats that became the design constant by the mid eighties.  The picture I posted was when about 3/4 through a complete refit, inside and out.  It was one of the last series of boats Columbia made before they went out of business.

Lots of info on the owners site about the series:

http://www.columbia-yachts.com/

[crazycarl]

I replaced the windows in our Starwind 19 with tinted plexiglass.
I did however, screw them in using the original screw holes and backed them up with a wood trim ring on the inside.
As much as I hate silicone, I did use black silicone to seal the windows as most caulks react to acrylic plexiglass.

[Smier]

On a temperature range of 0*F to 100*F, 0*F being the coldest day of the winter here and 100*F being the hottest day of the summer, an 8' piece of fiberglass will only expand approximately 1/64" while going from 0* to 100*F.  Acrylic on the other hand, will expand approximately 1/2" over the same temperature range, which is a huge difference!  I found several write ups that stated to avoid making a window out of acrylic larger than 4' because a 4' section would expand/contract 1/4".  My windows are only going to be approximately 24" in length so I should be looking at 1/8" in expansion/contraction from the coldest day to the hottest.

   The Dow 795 is designed to allow for this expansion and contraction of different materials, so I am actually not very concerned about the expansion issue myself, but you will have to keep this in mind if you screw or bolt the Acrylic to the hull.  You need to oversize the holes to allow for the expansion, and countersinking the bolt/screw heads is not a good idea.  My original acrylic windows cracked right at where the screws clamp them thru the frames, you can even see one of the cracks in the pictures of my original post!
 
   I'm pretty excited to get started on this, I'm going to pull the windows and make my templates this weekend.  I'm going to add 1" all the way around if possible, and hopefully my sheet of Acrylic will arrive at my work sometime next week.  I had it shipped to my work because I remembered that we have an industrial bandsaw down in our shop!  The only issue i see now is doing a nice job beveling the edges... I'm starting to get a precise plan in my head, and I'll be sure to document this with lots of pics...  I know how much we all love sailboat porn!!!

  Speaking of...  Crazycarl, that Starwind 19 is gorgeous, I really like the dark hull color!

[Smier]

I finally got started on making my windows!  First, I pulled the interior trim to make a template:



Then transferred it to some cheap plexiglass I picked up cheap at Home Depot:





I cut everything on my new toy:



Using the scroll saw is an art in itself, especially when cutting on an angle to bevel the edges.  It has a variable speed for the blade.  Turn the speed up too fast and the acrylic melts back together as the blade passes thru...  I'm starting to get the hang of it...

I'm over sizing the new windows to allow for a proper contact area for the adhesive to bond to the hull with substantial strength.  The bottom picture is a shot to show the old window size versus the new for comparison:





I have some rough spots to clean up on the first window, but it came out pretty nice.  The nice part is, I'm getting the hang of it quickly.  The thicker the material, the harder it was to cut on the scroll saw with a professional edge.  I'm using a blade specifically for cutting plastic with a high number of teeth per inch of the blade.  I'm pretty excited to finally get going on this again.  More to follow, hopefully soon!

[MacGyver]

If I remember right 120 to 220 make a nice clean looking edge if it is exposed.
Wear a pair of gloves as the heat burns trough to your hand quick if you are sanding fast.

Plexi is fun to work with........I have made some very nice things over the years. Really enjoy working with it

Mac