Emotionally, I can’t take this anymore. (Windows)

[s/v Jedi]

Originally Posted by Chotu

Polycarbonate doesn’t craze at all (that’s acrylic) and is 100% UV protected so...

Not going to throw it all out and waste more time if capturing it with additional tracks works.

You have experts telling you how it is, you fail miserably in your futile attempts but yet you still know better than them

You put a full 4x8 sheet against framing that also runs down the middle of the sheet?! If you would cut it instead, you reduce expansion by 50% !

[Chotu]

Originally Posted by mitiempo

Polycarbonate does craze. That is why the military changes it out in 3 year intervals - it has benefits but long life isn't one of them.

Acrylic is used be every hatch manufacturer because among other benefits it doesn't craze for many years. I have a neighbor with the original acrylic ports in a 1960's boat and they still look good.

It’s exactly the opposite. You have that completely backwards.

Acrylic is used on every deck hatch in existence on all the 1980s boats you see out there on the used market and in most of the fixed ports. It’s ALL crazed as can be. Literally not a hatch out there without crazing.

Polycarbonate is soft. It doesn’t craze at all. It yellows if not UV protected, it scratches, it has plenty of drawbacks, but crazing isn’t one of them.

My other windows are like 6 years old now. No hint of crazing. Nothing. It never will.

[noelex 77]

It is reassuring that the front windows are 1/2 inch thick rather than 1/4 inch. That sounds much more appropriate.

I think you are underestimating the difficulty in maintaining a seal or even of keeping the pane in place with a material that is so flexible.

Mechanical fastenings are not are a great option on polycarbonate. The flexing with a wave strike causes a peel force on the sealant and it is difficult to create a long term bond that is strong enough, especially with different rates of thermal expansion etc.

It is the difficulty of attaching the glazing reliably and securely that necessitates normally using thicker than 1/4” on large polycarbonate boat windows. The glazing is strong enough, but there is not a practical way of retaining the glazing in place. It does not need to be pushed in to be lost.

Acrylic is less strong than polycarbonate, but is also less flexible. Polycarbonate boat window thickness is primarily determined by selecting a thickness that is rigid enough. If it is rigid enough, it will be easily strong enough. Acrylic window thickness is primarily determined by selecting a material that strong enough. If it strong enough it will be easily rigid enough. In practice these two different requirements mean that for marine windows a suitable thickness will be similar for both acrylic and polycarbonate.

As polycarbonate is considerably stronger than acrylic it is easy to incorrectly assume thinner polycarbonate can be used interchangeably with thicker acrylic (as you have suggested in a previous post), but for marine glazing this is generally incorrect. This is part of the reason why most marine hatches, even low profile designs, are acrylic rather than polycarbonate. Hatch thickness cannot be reduced switching to polycarbonate so most manufacturers opt for the greater scratch resistance of acrylic as the better choice.

[Chotu]

Originally Posted by s/v Jedi

You have experts telling you how it is, you fail miserably in your futile attempts but yet you still know better than them

You put a full 4x8 sheet against framing that also runs down the middle of the sheet?! If you would cut it instead, you reduce expansion by 50% !

Kind of like you with your electrical system huh?

If you don’t like me, shut up and block me.

Tired of you piping in with your holier than though attitude and personal attacks. You’re no god of boat building. Don’t read my threads if you can’t handle reading a give and take discussion about a range of topics.

The day you build a boat is the day you can come in and toss about your personal insults. Until then, block me.

[Chotu]

Makes total sense.

Thanks for the clarification that you were talking about rigidity and practicality.

I had thought you were just talking about wave impact there for a bit.

So when I revisit this problem if today’s mechanical track fix doesn’t work, I’ll start delving I to a change of material.

I’ll report the outcome for sure.

Originally Posted by noelex 77

It is reassuring that the front windows are 1/2 inch thick rather than 1/4 inch. That sounds much more appropriate.

I think you are underestimating the difficulty in maintaining a seal or even of keeping the pane in place with a material that is so flexible.

Mechanical fastenings are not are a great option on polycarbonate. The flexing with a wave strike causes a peel force on the sealant and it is difficult to create a long term bond that is strong enough, especially with different rates of thermal expansion etc.

It is the difficulty of attaching the glazing reliably and securely that necessitates normally using thicker than 1/4” on large polycarbonate boat windows. The glazing is strong enough, but there is not a practical way of retaining the glazing in place. It does not need to be pushed in to be lost.

Acrylic is less strong than polycarbonate, but is also less flexible. Polycarbonate boat window thickness is primarily determined by selecting a thickness that is rigid enough. If it is rigid enough, it will be easily strong enough. Acrylic window thickness is primarily determined by selecting a material that strong enough. If it strong enough it will be easily rigid enough. In practice these two different requirements mean that for marine windows a suitable thickness will be similar for both acrylic and polycarbonate.

As polycarbonate is considerably stronger than acrylic it is easy to incorrectly assume thinner polycarbonate can be used interchangeably with thicker acrylic (as you have suggested in a previous post), but for marine glazing this is generally incorrect. This is part of the reason why most marine hatches, even low profile designs, are acrylic rather than polycarbonate. Hatch thickness cannot be reduced switching to polycarbonate so most manufacturers opt for the greater scratch resistance of acrylic as the better choice.

[Copacabana]

An option might be through-bolting the windows and using butyl tape for the seal, but it's going to change the clean look of those windows. You have to drill the holes in the plexiglass a little larger than the bolts to allow for expansion, but you'll have strong, leak-proof windows.

[mitiempo]

Originally Posted by Copacabana

An option might be through-bolting the windows and using butyl tape for the seal, but it's going to change the clean look of those windows. You have to drill the holes in the plexiglass a little larger than the bolts to allow for expansion, but you'll have strong, leak-proof windows.

On windows that size the holes would have to be very oversize to allow for thermal expansion.

Holes in acrylic or polycarbonate are best avoided in any case.

[mitiempo]

Expert advice from Tony at Select Plastics:

"Acrylic vs. Polycarbonate
I spend inordinate amounts of time discussing the pros and cons of acrylic and polycarbonate. In so much as I would like to bring some clarity to this issue. Please consider the following:

All major hatch, portlight, and window manufacturers use Acrylic in offshore / bluewater marine products.
Acrylic is more scratch resistant than standard (9034) polycarbonate.
Acrylic is significantly more durable when exposed to Ultra Violet radiation (sunlight).
Acrylic is less expensive than Polycarbonate.
Don’t misunderstand my preference for acrylic. I buy, use and sell a significant amount of both products and each has its application. In my humble opinion Acrylic is more durable, versatile and cost effective in the hands of a skilled craftsman than polycarbonate.

Additional considerations may include polycarbonate with UV and scratch resistant coatings. While these products are heavily promoted by several manufacturers and carry 5, 10 even 15 year warranties the following information has been reported in “real life” applications:

Polycarbonate is impact resistant. When it’s new it is almost impossible to break.
Small quantities (less than a 4 by 8) in gauges over 1/8th inch are difficult to find in the UV- scratch resistant grades.
Colors are limited. Only two standards (gray and bronze). Try and find anything thicker than 1/4 in UV/ scratch resistant!
Polycarbonate foreshortens when subject to static or dynamic loads. What this means is if you replace your hatch lens with polycarb, seal it and then step on it the ductile material will deflect (bow) in the center. One of two things may happen. 1st you will surely break the watertight seal, 2nd you may end up with a leg in your salon.
As for the warranty: The original owner is warranted against failure subject to the material being submitted to the distributor for evaluation with the original invoice subject to actual replacement cost at the time of purchase. I guess this means they sell you a new square of material and apply the old payment to the new cost. How about the labor to fabricate the part, install it and sealant? Why take the chance?
Polycarbonate is a great material; The US Air force uses it for fighter canopies! I sell Polycarb to the USCG and US Navy. Remember they don’t mind using it because we are paying to replace it every three years.
Both Acrylic and Polycarbonate have specific uses and installation requirements.

Cast Acrylic (of a specific thickness) is in accordance with CE and ABYC guidelines, and installed on virtually all of the big blue- water sail boats produced on both sides of the pond. Polycarbonate is commonly used as a replacement due to its ease of fabrication and incredible initial strength. The USCG and USN require Polycarbonate on their vessels but they also have a preventative maintenance cycle of 36 to 42 months for change out. My Tax dollars at work…

Due to its ductility Polycarbonate it is more challenging to install. I have seen Sika Flex 295UV with primer and Dow 795 both mentioned. I use and recommend both. Dont go over 4 ft continuous length with a fixed portlight. Remember the coefficient of thermal expansion for Acrylic and Polycarbonate is in the neighborhood of .000039 per inch per degree F. That means an 8ft plastic port will expand and contract up to 1/2 of an inch from the coldest day in Feb to the hottest day in summer. WOW!! Compartmentalize the job. It will be easier to install and less prone to leaks.

Never ever bolt a plastic portlight in place. Screws are fine to hold a lens till the adhesive cures. Take them out asap and fill the holes with the aforementioned products. Both of these products are rated at 700 + percent elongation before tear. Strong flexible and UV resistant.

Been to a boat show lately? Seen any screws? Glass is good so long as your boat does not twist or torque. Show me a fiberglass boat that does not twist and I will show you a cocktail barge tied to the dock”.

Very good advice.

[Manateeman]

When I finish ripping out my four Bomar Ocean 24x24 hatches I’ll put them up for sale cheap...real cheap. I’ve really enjoyed fixing them and the leaks keep my plants nicely watered.
Bomar. Never again.
Chotu, if you put in laminated glass, make sure the installer has experience with this type because the film can start frosting at the edges if exposed to solvents.
The edges look like a window in winter. I had “professionals” do my 10 pilot house windows but they just didn’t understand how to install them in aluminum.
I also cracked a Bomar Ocean hatch by stepping on it. It cracked at where the hole was drilled and went clean across. 1/2” plastic.
OK. I’m a tad heavy but I’m not manatee weight.
I’m confident my bank glass pilot house windows will take a wave. We have storm shutters ( stainless) for hurricanes ...Sand and flying junk, but it’s only to avoid scratches or cracks. I think glass is the only option that works long term.
I’m done with plastic. But each to his own...that’s boatbuilding. Good luck.
Happy trails to you
Mark and his plexus crazy manatees.

[noelex 77]

Originally Posted by Manateeman

Chotu, if you put in laminated glass, make sure the installer has experience with this type because the film can start frosting at the edges if exposed to solvents.
The edges look like a window in winter. I had “professionals” do my 10 pilot house windows but they just didn’t understand how to install them in aluminum.

This is quite a common problem on marine laminated windows. I as understand it, the problem it is due to moisture finding its way between the central plastic film and the glass. There are some new plastic films (3M make one) that can be used during construction of the glass that reduces the chance of windows developing this affliction. As it always starts at the outside and progresses towards the centre, the other option to reduce or at least delay the problem is to design the window so the edge is hidden for a considerable distance.

The alternative is use tempered glass which is just as strong as laminated glass and cannot suffer this problem. However, if tempered glass is broken it can leave a large hole. The broken fragments are blunt and reasonably safe (unlike ordinary glass) but some provision for sealing the hole in the unlikely event of breakage needs to be considered.

[Chotu]

Well, they are already watertight. LOL. I guess that’s a good thing. We had some kind of fog and rain type stuff last night. It came in with the 795/VHb tape window, but the new one I put on no drips.

I also found that on the side that my girlfriend did, there wasn’t enough gap for thermal expansion. My fault for not mentioning it to her. So, I do have to shave down a little bit. I’m going to slide it out shave it down, and continue with the mechanical capturing technique. Just doing that in my spare time and observing it growing and shrinking over the next few days. If that doesn’t pan out, then I will move onto the next steps which is getting different material. For now, I will move on to other projects. At least the urgency of water dripping in is abated.

[Chotu]

Mitiempo: That’s a good quote you put in there. Makes perfect sense to me. And thank you nolex for continuing to reply.

I will revisit this thread in a little bit once I see what happens with this mechanical capturing technique. So far, it’s totally waterproof at least. But I haven’t had 40 knot rain driven from the bow. LOL. I don’t think it would be waterproof in that case. Not until I get this next piece on to capture it in a fore and aft sense.

So everyone that said there was not enough room for it and it was expanding and bowing itself out because it didn’t have enough room, you were correct.

I didn’t notice the far side was out of whack.

[s/v Jedi]

Originally Posted by Chotu

Kind of like you with your electrical system huh?

If you don’t like me, shut up and block me.

Tired of you piping in with your holier than though attitude and personal attacks. You’re no god of boat building. Don’t read my threads if you can’t handle reading a give and take discussion about a range of topics.

The day you build a boat is the day you can come in and toss about your personal insults. Until then, block me.

You’re not getting hugs from me but I had figured that is not why you’re here. My comments can be hard to swallow but are very true nonetheless. I only do “true”, not “hugs”.

Another reply just above here from an expert says exactly the same about acrylic vs polycarbonate, just without the facepalms but you simply ignore it. You have attempted the install seven times (!!) and still refuse to come to peace with the facts that it is the installation done wrong, not the brand of polycarbonate they sold you, not coronavirus, not the Florida heat, not me telling you harshly etc.

What do you know about me and my knowledge of polycarbonate vs acrylic? I have 20 years of extensive experience with it and helped dozens of people here on the forum and irl with their windows problems. Have you tried a search? Even with polycarbonate my recommendations have stood the test of time.

It is nothing like me with my electrical system because electrics and electronics are my primary area of knowledge at university level, so it can be considered to be designed at expert level. It is clear that your knowledge of marine glazing isn’t anywhere near those levels because in all seven attempts you made beginner mistakes (and that is not a personal insult nor attack, it’s just fact)

Holier than thou is BS as well: I made all those mistakes as well and am not ashamed to admit it. It’s just a very long time ago... like 20 years. And over that time span I have adapted as I learned and I’m sure a professional installer can still teach me something new about it.

Last time you were sure that I was wrong you went on-line and researched it and found that I was right.... and you simply acknowledged that (the epoxy paint). Never have you read anything from me addressed to you that was wrong. Telling you that you did it wrong is not a personal attack at all, where did you get that idea?

What people have been trying to tell you in a nice way is the same I’m telling you in more blunt terms: you’re using the wrong material (it is you who has it the wrong way around, not us: acrylic is more UV resistant and much stiffer), you’re using material that is not thick enough, you can not install an 8’ long sheet over two window openings: it should be cut down to multiple pieces to reduce thermal expansion drastically, the bead of 795 -must- be a minimum thickness and shape as explained in the manuals and so must be the VHB tape and the bead must be behind the window, not between butted panels like obsolete window putty. Last but not least you can not use mechanical fasteners that go through the window. When you “bolt it down” like you propose, it will either break or your whole house will be ripped apart by it: thermal expansion is a force of nature that you can not tame.

One more thing that is not brought forward clearly enough: you state that it is strong enough and will pay anyone $1,000 who can break it with a baseball bat. This is not what people mean when they tell you it is not strong enough. What they mean is that the whole 4x8 sheet can be pushed through a single 4x4’ opening without breaking it and at 1/4” thickness that does not require much. That is the mode of failure for this flawed application.

You must change to cast acrylic, to 1/2” thickness, to maximum 4’ dimensions, to correct VHB + 795 application, using window foam tape to close the gap on the inside and just a bead behind the window on the outside. The cut edge should be painted black to not allow UV in through it. You may not like this at all but it is the only way to a successful install. You may not like me for being blunt but I’m not letting you do stupid things like bolting it down either

[Chotu]

For later.

This is the exact Lexan I have for the other windows. The replacement was garbage Lexan in comparison. Covid.

[DougM]

Chotu - sorry i gave you my ultraconservative numbers for shear movement in a previous post (life safety and survival of company on line thus i use those numbers). realizing that i may have added to your stress, so i did you up a spreadsheet and looked up Dow corning's numbers for silicone. Hope it helps , please ignore if no longer relevant


Assume installed at 30 degrees C, stress free.

max delta T to the positive 50 degrees C
sheet is 4x8, call it 100 inches
fiberglass cte 10 X 10-6 per degree C
polycarb CTE 70

expansion FRP 0.05
expansion polycarb 0.35
Difference 0.3 inches

divide by two as movement is taken up on 0.15 inches THIS IS WORST CASE MOVEMENT
either side

You now need to select a joint thickness to keep acceptable shear strain to allowable limits.
what is allowable? 6 or 7 times the movement typically daily movement would make something increbly durable.
but the number was intended as a maximum. 4 x, or 25% shear would be acceptable as a bulletproof system.


But I just looked up dow corning’s view of shear movement of silicone joints. They say 100%! Damn I’ve been way conservative (life safety involved).

https://www.dow.com/documents/en-us/...df?iframe=true
Pg 58 for shear movement

Conclusion – you should be OK with a 0.3” thick joint, I'd try

reality check – I had a gemini (sold two weeks ago) with a 6 ft wide window bonded to unerlying frp with vhb and silicone, 1/4 spacing i believe. It was durable.