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Lewmar Super hatch update and question

MitchK

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Sep 22, 2017
100
Capital Yachts Newport 28 Burbank, WA
Well, I finished installing the new lens in the Lewmar Super hatch on our N28. I replaced the hatch to frame seal too. I ended up using 1/2" thick cell cast acrylic to make the new lens. The original used a thin seal of butyl between the lens and frame, then the gap between the inside edge of the lens and frame was filled with some sort of sealant. All of which had failed.
The original lens was 10mm thick. I could not get a piece of 10mm, so I went with 1/2" cell cast acrylic.
Instead of the thin butyl between the lens and frame, I used Dow 995 structural adhesive, and filled the edge gap with Dow 795. Both are designed to attach and seal window glazings to the frames. I also sanded the area of the lens that sits in the frame for better adhesion. Its not perfect, but all in all it turned out fine. Hopefully the Dow products will keep it all sealed up.

I am getting ready to re-install the new lens/frame back onto the boat. I have one more question to resolve before I do. The hinges that attach the hatch to the lower frame is made of two aluminum flat arms. These arms bolt to the new acrylic lens. When I removed mine, there was no seal of any sort between the lens and the hinge arms. For those of you that have rebuilt their hatches, what type of seal did you use between the hinges and the lens? I am considering making a couple of flat gaskets out of either neoprene or EDPM rubber to fit between the hinge arms and the acrylic. I will probably used some butyl around the screw threads to seal the screws to the T nuts. That should make a nice long lasting water tight seal. Any comments on your experiences would be greatly appreciated.
 

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Aug 1, 2011
3,558
Catalina 270 Wabamun - on the orange ball
Order up a roll of Maine Sail butyl. To say that you will not be disappointed is quite possibly a serious understatement.
 

MitchK

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Sep 22, 2017
100
Capital Yachts Newport 28 Burbank, WA
Meriachee,
I have a roll of Mainsails Butyl. I have chosen not to use it for the primary seal between the acrylic and hinges. I do plan on using it around the screws that attach the hinges to the acrylic. I am trying to figure out what to use between the hinge and the acrylic to cushion and protect the acrylic during use, and expansion/contraction due to heating/cooling. Acrylic expands quite a bit due to temperature. At this point, I am going to use a piece of EDPM between the hinge and acrylic, and butyl around the screws to seal them. Hopefully someone who had done this job will weigh in and let me know what they did, and how it turned out.
 

MitchK

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Sep 22, 2017
100
Capital Yachts Newport 28 Burbank, WA
Ok, I finally finished the install of the new lens. I ended up machining a new set of T nuts patterned after the original out of some bronze round stock I had. They are not perfect, but will do the job. I ended up using the same metric (6 x 1.0) screws as was originally used. I made the barrel a little longer since I used 1/2 acrylic instead of the original 10mm. Also, the stainless screws I found are a socket head. Not my first choice, but I was running out of time, and wanted to get the hatch re-installed. I used a piece of EDPM rubber between the hinges and acrylic with a ring of butyl around the screw so that it filled in the gap between the hinge and the T nut. All in all, it went well. It also looks great!. Nice to be able to open the hatch and get a little extra ventilation. The original hing rubber still holds the hatch in the open position. Next big project is the rebuild of the sliding hatch.
 

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May 6, 2010
410
1984 Oday 39 79 Milwaukee
I have recently re-done three of my Superhatches. Oddly, the smallest of my hatches had thicker acrylic than the large hatches. The acrylic I got is just slightly thinner than the acrylic in the large hatches, .354mm where the originals were 3/8". I bedded them in black butyl tape, and sealed around the perimeter with Dow 795, replacing the rubber seals in the process. For the hinges, I just created a small bevel in the acrylic and used a butyl ring only around the fasteners. I also replaced the o-rings on the handles. I used the old acrylic to trace a pattern on the new, then cut it out just outside the lines using a jigsaw with a blade for plastics. I then clamped the two together and used a router with a pattern bit to get them exact. I ground a couple of drill bits to a much steeper angle and drilled some test holes in some scrap pieces to make sure they didn't grab. Cleaning the old sealant and butyl off the frames was the worst part of the job. My larger hatches are in need of new keepers, but they are pretty spendy from Hatchmasters.
 

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Apr 8, 2010
1,184
Ericson Yachts Olson 34 Portland OR
A number of years ago I had to replace both of our hatches, a size 70 and a 20.
The larger hatch had a bent frame, courtesy of the PO. It was just as well to start over.... those old "roll stop" hinge assemblies were a poor design. Whoever designed them should be shot. Out of a cannon. Into the sun.
:)
Your workmanship looks really good, and no way could I do as well.