Refurbishing Lights (Windows) on the 21-Footer

[Spot]

I am looking to either re-seal or replace the lights/ windows in the Southwind 21. I would love to have real operating and screened portlights, but will settle for having glazing that keeps the outside water on the outside...

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Currenty there are (4) units, (2) rounded rectangles and (2) tapered rectangles, approx 10 x 25" each. The glazing is a tad thicker than the hull and clamped by 2 trim rings, one external and one internal, with no evidence of sealant. Glazing appears to be in the 3/16 to 1/4" range (4-6mm).

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I was thinking that perhaps an external pane sealed to the outer hull might work better than current:

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Thoughts? Which glazing material? Which sealant? Do the bolt holes need to be oversized for expansion/contraction?

Thanks for the consideration and input.

[Frank B.]

My original (Columbia 8.7M) was far worse than yours.  It looked really good and performed terribly.  Columbia wrapped the glass into the opening and set the port from the inside, just screwing into the wood frame and cabin trunk core with some sealant between. So it had a nice recessed look but, as might be expected by even the least knowledgeable, the differential expansion from the part that saw the sun and the part that was insulated by the cabin trunk thickness was significant so that glazing material moved constantly and even cracked and crazed.  leaked like a sieve. I did exactly what you are proposing.  Used tinted polycarbonate as the glazing material 1/4" thick. Routed the edges with a round over to cut the sharp edges. Sealed between the trunk surface and the glazing, don't remember what sealant I used.  I used oval head machine screws countersunk to install, nuts and washers on the inside, and made a new teak trim ring piece to hide the fasteners on the interior.  They never leaked again.  I did not leave extra space by oversizing the holes, just normal fastener clearance.  I think the coefficient of expansion was close enough for the sun exposed surfaces that it wasn't necessary.  I had to get used to the fact that the ports looked much larger because of the exterior dimension of the glazing but worth it to get rid of the leaks. Somewhere I have a pic of the finished product, will see if I can find it.

As mentioned I used polycarbonate, but you should look at both that and acrylic as an option.

[Frank B.]

This is the pic, not very clear and I don't have a close up. It was a scan of a photo taken before digital cameras where common.
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[Charles Brennan]

Spot, This is a re-post from the "old" TSBB; hope it helps.

Prior to WWII the government made a deal with the airlines to subsidize them a little, with the understanding that in time of war, their planes and their pilots would be used for the war effort.
This led to the Air Transport Command whose very first task was getting material across the Atlantic, since German U-Boats were wreaking havoc with commercial shipping.
The Aeronautical Engineers figured out how much they could load aboard and how they could figure out how to get stuff across the Atlantic on one hop.  They taught the pilots to use octants  (like a sextant, when altitude above sea level is also a factor) to navigate with.  They struggled to get off the runway and they flew at very slow speeds, just barely above a stall, in order to make the fuel last all the way to the destination in adverse headwinds, which was about 11 or 12 hours of flight time.
The pilots would arrive exhausted with the strain of flying so long while just barely in control.
The pilots knew instinctively that this approach was wrong and said as much, but the Engineers were adamant.
On one flight, the navigator made a mistake and got them off course and everybody on board knew there wasn't enough fuel to make it all the way across, or make it back home.
The pilots decided to heck with it, why delay the inevitable and put the plane up to normal cruise speeds, figuring they might as well be comfortable flying until the fuel ran out and they crashed to their deaths somewhere in the north Atlantic.
To their great surprise, they safely reached their destination and a bunch of angry pilots went to the Engineers and said: "We TOLD you so!" 
The Engineers went back to their slide rules and hemmed and hawed, then said: "Of course! As the weight of the fuel depletes, the aircraft isn't so heavily laden and flies more efficiently!"
So they started flying like the pilots insisted they should have in the first place and started arriving in 8 hours, instead of 12.
They were able to double the amount of material being ferried across, which greatly helped the war effort.

What that taught me is that the learned Engineers aren't always right, no matter what their slide rules tell them. 

In 2021 and 2022, I refurbished my 45 year old sailboat, which included totally rebuilding the 4 fixed ports.
They were typical '70's era aluminum frame and tempered glass ports with a glazing channel, an inside frame gasket and a flange to hold the port against the hull.
And were now old enough that they leaked like a sieve and ended up ruining a BEER Cruise, when I couldn't tell if I was leaking rapidly, or sinking slowly. 
I replaced everything but the glass and frames, all new glazing and gaskets and bedding and did everything by the book a la Casey, et al and figured I was good to go and leak free.
The subsequent BEER Cruise and Columbus Day Cruising Regatta greatly disabused me of that notion. 
One port leaked less, two ports leaked about the same and (of course!)    the port over my bunk leaked worse.
Much worse.

But, by golly! They LOOKED good, didn't they?!? 
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I decided I had had enough of those leaky ports and I was NOT going to try and rebuild them again. 
I was Over It. 
I looked online and quickly discovered no one manufactures new ports as big as mine, any more. 
I ripped them (gently!) out of the hull.
After all, I was going to need them for templates for replacement ports that I intended to build.

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I first consulted that bastion of expertise (YouTube) so see what everybody else was doing.  It involved a lot of sealant and goo and masking and ugly black taped frames around acrylic plastics.
I knew I wasn't cabinet-maker grade enough, like Charlies Jones or Frank B. or Westcoaster, to make my own wooden frames, and besides,  I didn't want to spend a ton of money on teak and wait forever and a year to get it and even more time to fabricate it only to have four more things to varnish periodically..
Have I ever mentioned that I would rather sail on boats, than work on them? 
I had made Plexiglas furnishings in the '70's and I decided I was going to ignore all the experts and Engineers and slam that throttle up to cruising speed and go my own way.

Most all the YouTube videos are using 3/8" plexi (or bigger!) but they are also generally much bigger boats and I didn't want the ports sticking way out from the hull like some transparent cancerous tumor.
I knew from experience that 1/4" was probably strong enough, but only if nothing ever slammed into it and something ALWAYS slams into a boat when you least expect it.
While acrylic doesn't shatter the same way as glass does,  it does shatter (OK, crack)  under the right conditions, so I finally settled on 5/16" UV- treated cast acrylic, since cast is always stronger than extruded acrylics.
Got a quarter-sheet from McMaster Carr, my go-to guys up here in the Boating Wasteland of north central Florida and cut it up.
My wife once told some guests that my hobby is cutting big hunks of stuff, into little hunks of stuff; she's not really wrong. 
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Next, I used those worthless aluminum port frames to make cardboard templates and added a half inch all around, since there wasn't much hull to grab onto, otherwise.
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You can see the lines the old port frames made; it would have been too narrow to reliably hold fasteners.
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I cut out the acrylic to match the templates and rounded over the outside edge with a 1/8" round-over router bit.
Hoping this will avoid chafing on lines, scrapes on people, and chipping on the acrylic.
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Ignoring the conventional sealants and goos that always leave me looking like I'd been mugged by mimes, I decided to get a sheet of white 1/8" rubber.
After all, 1/16" of rubber washer inside a plumbing gate valve can hold back up to 30 psi of water; 1/8" of rubber should be able to hold out rainwater in a driven storm.
I reasoned that all I really needed was a giant port-sized rubber washer.
It would also make things easier to maintain and repair, since I wouldn't be scraping sealant off every time I had to deal with a port.
And a lack of sealant would allow me to visually inspect the rubber gasket under the acrylic any time I wanted and as the rubber got old and compressed, I could simply re-torque the fasteners tighter.
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Drilled the holes on 3" centers, except the ends, which were where I had the most problems with leaks on the old ports and so were closer together.
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I used the port as a template to drill the hull for 10-24 truss head screws.
When I was done with the hull I went back and enlarged all the port holes in the acrylic to allow for the difference in expansion co-efficients between the fiberglass hull and cast acrylics.
Port side main cabin port:
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Port side forward cabin port.
Placed against the hull they rocked side to side slightly, showing me the hull has curves that you don't even suspect and giving me some insight as to why the aluminum frames were so problematic.
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I used the ports as forms to cut out the rubber gaskets.
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Then I clamped the rubber under the port and drilled holes in the rubber smaller than a #10 screw, so the rubber gasket would have to stretch around the screw shaft.
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After that, I placed the gaskets and ports on the hull so I could trace the port dimensions from the inside of the cabin.
After the centers were cut out, I now had a port-shaped O-ring gasket, 1/8" thick.
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They are held on the inside with sealing washers and 10-24 nylock nuts.
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Finished product.
I've never seen ports fabricated in quite this way and time (and rain!) will tell if I was right to go my own way and ignore the experts, or not.
I figure even if it fails horribly, I can simply unscrew the (nearly 100!)    fasteners and go the conventional sealant route.
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After 4 years, they are still holding up, admirably. 
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In summary:
1) Lexan polycarbonate, or Plexi-Glas acrylic is your choice; Lexan expands more and scratches more easily, where Plexi-Glas doesn't expand as much but doesn't  scratch as easily.
2) The only consideration between the two, is whether you increase the hole size one drill size up or two, from the nominal screw size.
3) No matter which material you select, drill the rubber gasket one drill size down, ideally, so the rubber has to stretch slightly around the screw threads.
4) Don't forget the rubber-backed sealing washers, before adding the inside cabin nuts.

Hope this helps,
Charles Brennan

[Spot]

Thanks Guys! I really appreciate the words and pictures.

PS 'mugged by mimes...' LOL I hear you after using black 5200 on a white hull and green keel (tubes were a gift from a 3M rep)

Here are some closer pictures of current:

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