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post #11 of 24 Old 04-21-2012
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Re: rebedding my hatch lexan (if that's what it is)

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I guess one professional couldn't make up his mind.

Safety has nothing to do with it. The sealant or bedding keeps the water out. The fasteners, commonly machine screws, hold the fitting in place. Except for acrylic ports which should never be attached with 5200.

I am grateful that everything above the waterline including the hull/deck join on my 1977 CS was bedded with butyl. Easily removable and very few leaks since new.
I can think of at least 14 vessel that sank, on their way to to catalina Island that the owners claimed went down because of leaks.
I do know one thing. the US Congress wrote the congressiona charge of neglegance to as it stated to proccicute those who
don't know what a knolegable mariner would know.
Let someone do something a knolegable mariner would not let them do.
Not doing something a knolegable mariner would do.
And the one I always say doesn't fit. Doing something a knolegable mariner would have have done. Going to put you in prison for 14 years for something you actually did.
You seem to have a lot of time I would as the former knolegable mariner for the Pardee sea scout base (Training facility for the USN) recomend you start reading Code of Federal regulations title 33 Navigation, cfr 36 on going water works projects, cfr 46 Shipping (Thats not all commercial.)
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post #12 of 24 Old 04-21-2012
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Re: rebedding my hatch lexan (if that's what it is)

These guys are the experts on hatch repair.

Select Plastics, LLC: Marine Hatch Repair
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post #13 of 24 Old 04-21-2012
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Re: rebedding my hatch lexan (if that's what it is)

So are Lewmar, They don't seem to agree either. If I had the time I would point out that currently currently on the west coat we define experts as those how design (Or Bar stool skippers, & a perfessional as the guy who make is work. (and sends the data to the designers so others don't have do deal with it.
May your seas be calm, & your winds be far!
I have work to.
JC Boyce
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Re: rebedding my hatch lexan (if that's what it is)

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I have work to. JC Boyce
Grammar and spelling studies I hope! Those were some of the most incomprehensible postings I've seen.
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I, myself, personally intend to continue being outspoken and opinionated, intolerant of all fanatics, fools and ignoramuses, deeply suspicious of all those who have "found the answer" and on my bad days, downright rude.
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Re: rebedding my hatch lexan (if that's what it is)

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Grammar and spelling studies I hope! Those were some of the most incomprehensible postings I've seen.
Sorry I started reparing boats in 59 at the age of 4, being dissexic I tend to write things backwards, & sometimes crossed. But I'll let you get back to your edicut class or is there a medical reason for your defficanceis.
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Re: rebedding my hatch lexan (if that's what it is)

If you take a look at the 3M reference page here, you'll see that 3M doesn't recommend 5200 for Lexan.

While I'm comfortable accepting his claim that Mr. Boyce has in spent more doing this kind of stuff than I have, I'd still tend to side with the manufacturer and not recommend 5200.

I'll concede the point that 5200 would probably work, and might even work well. But the thing I'd come back to is that it is more or less permanent -- if you make a mistake or simply just don't like how it turned out there's no going back.

For bedding plastic ports (acrylic or polycarb), it's hard to beat silicones. They are flexible enough to handle the expansion/contraction of the plastic sheet as temperatures change. I've had great results with Dow 795. It's not something you can usually find as easily as other caulks, but it's worth taking the time to find.

Whatever you do, DO NOT use a polysulfide sealant -- it will attack the plastic and cause serious crazing problems and significantly weaken the plastic. Along the same vein, do not use cleaners containing alcohol (which would include Windex, among others) -- they too will react badly with the plastic.
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Re: rebedding my hatch lexan (if that's what it is)

gl-
Your best bet? Is to find out what the plastic is. Any local plastics shop can tell you if it is acrylic or polycarbonate. A touch of solvent will show which one it is immediately, also a scraping that is burned should show up differently. No big deal.
If it looks crummy, replace it. If it is something terribly dear like 1/2" thick real Lexan...you can want to just polish it out (or have them buff it up) and keep it.

Can you reinstall it? Well, it shouldn't have just been glued in. Usually a frame is made up around it, or the glazing set into the frame, with a caulking or seal that is designed to flex and expand as the glazing does. If it can't move, it will craze.

Then you've got a small problem, if the caulking you use is not designed to work with the plastic (sometimes a primer is required) it won't stick, and it will leak. Not good.

So the best bet is to find out what plastic you've got, find out what sealant is correct for it and confirm that with the mfr. or label. And then to reset/rebed the glazing the way it was supposed to be seated.

If the hatch comes off, it might pay to just take the whole thing in to a plastics shop and say "takee fixee" but I'd still confirm that they're going to use the right materials. When this stuff is done right, you only need to do it ONCE.

How the kids managed to kick in a hatch, which is supposed to be as strong as the hull...I'm not sure I want to know. Makes you wonder, if the hatch itself should be upgraded, if there's any chance of being caught out in wx.
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post #18 of 24 Old 04-21-2012
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Re: rebedding my hatch lexan (if that's what it is)

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If you take a look at the 3M reference page here, you'll see that 3M doesn't recommend 5200 for Lexan.

While I'm comfortable accepting his claim that Mr. Boyce has in spent more doing this kind of stuff than I have, I'd still tend to side with the manufacturer and not recommend 5200.

I'll concede the point that 5200 would probably work, and might even work well. But the thing I'd come back to is that it is more or less permanent -- if you make a mistake or simply just don't like how it turned out there's no going back.

For bedding plastic ports (acrylic or polycarb), it's hard to beat silicones. They are flexible enough to handle the expansion/contraction of the plastic sheet as temperatures change. I've had great results with Dow 795. It's not something you can usually find as easily as other caulks, but it's worth taking the time to find.

Whatever you do, DO NOT use a polysulfide sealant -- it will attack the plastic and cause serious crazing problems and significantly weaken the plastic. Along the same vein, do not use cleaners containing alcohol (which would include Windex, among others) -- they too will react badly with the plastic.

And more important GE withdrew lexan from the marine feild after about 18 months of service, because it was designed to deflect a built, but starts breaking down in salt water. I didn't have that problem it's jelloy quality was a bigger problem.
All I know is I used lexon because my suplier gavit to me. & mounted it in 5200 because the properties I knew were satasfactory to my used. the required recaulking in 8 years but I replaced the lexon at the same time.
Point being if your going to use a non marine bullet resistant material to stand up to a green wave, the disclamer from the bedding company should be lengthy, if they know their data. does that mean it doesn't work.
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post #19 of 24 Old 04-21-2012
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Re: rebedding my hatch lexan (if that's what it is)

The only product used @ Bennett Bros. Yachts is Sikaflex 295. Bennett Brothers Yachts This is used to secure the this polycarbiate to the hatch not the hatch to the boat. The most inportant steps is to clean all old addhesive of and use the Sikaflex Primer. Primer must be used.


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post #20 of 24 Old 04-21-2012
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Re: rebedding my hatch lexan (if that's what it is)

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Originally Posted by jcboyce View Post
Actually I havn't had to break glass down to dust, &n cut the bedding off with a wood chissel since before the formula changed back in the 80s.
But If your primary concern is how easily a part you are installing will come off, rather then that the vessel will return home safly. we are working to different ends. Mine is saftey.
But back in the 70s the boatworks called together 6 boatworkers including my self to get oppenions on how best to do something. the only thing I remember was 6 professionls came up with 7 oppenions.
Polyurethane sealants, with the exception of Sika 295UV, can leach the plasticizers out of polycarbonate and acrylic and they also bond quite inconsistently to them. This inconsistent bonding is why Sika 295UV requires the special primer for adhesion to polycarb or acrylic. Polysulfides are even worse and can cause acrylic and polycarbone to become prematurely brittle..

This is why 3M adds their little "disclaimer", if one so desires to actually read it:

3M Marine Adhesive/Sealant 5200 is not recommended for the installation of glass, polycarbonate or acrylic windows that are not also mechanically fastened with a system designed by the manufacturer.

Inconsistent adhesion of these unprimed substrates, specific design of the window, and movement due to thermal expansion and flexing, may cause application failure. It is strongly recommended that the customer contact the window/port light/hatch manufacturer for recommendations on proper sealing procedures.

______
-Maine Sail / CS-36T


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Last edited by Maine Sail; 04-21-2012 at 06:40 PM.
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