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Dave and Anke
triloboats swirl gmail daughter com

Saturday, January 14, 2012

A Window on Our World

Don't need X-ray vision to see Paradise!
Windows on sailboats run small, for the most part, at least those on the hull proper.

This has excellent historical reasons. Water weighs roughly a ton per cubic meter, about the equivalent of a good sized car. And it's moving, sometimes fast. And you're moving, sometimes fast. At sea, collisions with waves are a dime a dozen. While there are special varieties of glass that, in larger sizes, can stand up to this, they're expensive. A compromise was reached... small port or deadlights (portlights open, deadlights don't).

Shoal boat designers struggle with height. There's not much boat in the water, so we have to work harder than others to keep the hull low. Pilothouses are often built on top of the hull to provide an all-round view via larger windows, but this adds height, raising the center of gravity and windage. If we could improve our view from lower, in the hull itself, it reduces the need for superstructure.

Fortunately, we're living in the Age of Miracle and Wonder (thanx, Paul Simon). Polycarbonate (poly) - the stuff of bullet-proof windows for Popes, Presidents, armored cars, bathyspheres and ROVs - is available at DIY prices. My glasses, snow goggles and shop glasses are all made from the stuff.

LUNA's windows were already bigger than is usual... we often got comments on how light the interior was, and how much view we had. But the 1/4 inch polycarbonate scratched quickly. Pledge (TM) is optically clear, and fills small scratches, but couldn't keep up. After a decade, our clear views were noticeably dimming.

But coatings have come a long way. For a moderate price, sheets with a scratch resistant finish are now available. Still have to treat them gently, but three years into it, we've only got the one or two scratches from bigger blunders... not the thousand micro-scratches from mere cleaning.

We helped Andy Stoner build his MARY ELIZABETH (T32x12). Big windows for a 360deg view. It was an epiphanal moment when the tarp came up, opening out the view, even onto limited glory (driveway, urban neighborhood, small highway). Anke and I flashed on the fact that, relatively speaking, we'd been living in a hole!

Still... SLACKTIDE is a low hull, even as 26 footers go... would 8' x almost 2' side windows, barely a foot above the waterline work?

LUNA rarely saw sea-water that high... the leeboard guards help by acting as splash guards. But the hulls are so light and buoyant, they're lifting over all but the very tip of green water reaching that high. Only one way to find out!

SLACKTIDES side panels, before and after window cut-outs.

SLACKTIDE's hull (along the cabin) is ply-foam-ply composite, totaling 2 1/8 inches. We fastened 1/4 inch polycarbonate outside, using SS screws and finish washers bedded in DAP Alex Plus. DAP AP is 'siloconized acrylic' latex window caulk... cheap, easy to work, water clean-up. It's only lightly adhesive... can be removed and rebedded... we use it for most bedding jobs.

The trick is to spread it under where the windows will land (we use 1 1/2 inch overlap), then run a thicker bead down the center of that. Be gentle, and apply gradual pressure as you fasten. Once full contact is made (you can see it), stop (don't tighten too much and drive the bedding out). As it dries (may take quite a while) you may have to snug down the screws, here and there, as water evaporates. Once the edges are well and truly dry, paint to protect (raw DAP mildews, and may rehydrate and wash out if it's not fully cured). If thermal cracking around the edges occurs, touch up with DAP before maintenance painting.

Alternatives might be silicone, butyl and, possibly, neoprene tape (gasketed, but not bedded).

Square boats and those from non-tortured plywood are easy... the poly can be fastened directly to the hull. Might have to frame out a bit on complex-curve hulls, as sheet poly won't take the bend.

Inside the hull, we applied adhesive weather-strip around the window cut-outs, and fastened panes of 1/8 inch acrylic. This is much cheaper material; brittle and far less flexible, it nevertheless stays clear and is considerably less prone to scratching (no coatings necessary). We used no bedding so, if moisture fogged the windows from between, we can open and air them out. Hasn't been a problem.

The purpose of this inner layer is to create an insulative dead air space. Despite it's low tech (no vacuum or exotic gasses) it totally eliminates condensation and retains a whopping portion of heat.

As far as strength goes, my thinking is that the outer layer, bearing as it does against the hull, should be proportioned to handle all foreseen external loads. The inner layer, is both weaker, brittle, and unsupported by hull (fastener grip is the only holdfast). If the outer layer gave, I wouldn't count on the inner one. Poly comes incredibly thick, but I've never seen more than 1/2 inch (and often 3/8 inch) on large, offshore fishing vessels, many of whom have taken green water at bridge level. Their windows (even lower in the hull) are typically far larger in area than cruisers would need, and installed with H-rubber lockstrip (not directly backed by hull). Conclusion is, strength should be adequate with this simple installation.

So. Sailing SLACKTIDE over three years, now, we have very occasionally run green water over the lower edge of the window (time to reef, as we're dragging guards, anyway). Our windows have gotten splashed, but never immersed by a wave, even in short, steep seas. No indication that it would be a problem if we had.

We toyed with the idea of opening windows. That would have been SO sweet! Decided against, for our first go, but I think they're in reach. Framed with 2x2 stock and double paned, one can create a very rigid girder. In ply-foam-ply, it's easy to cut the inner layer openings smaller, creating a strong, integral lip. Good hinges, gaskets and dogs necessary, of course, and maybe a failsafe splash trough on the inside. Next boat.

Meanwhile, the payoff is handsome. LOTS of light in the interior. And the view! THE VIEW!! Everything we always envied in motorboats' (or some motor sailors') large houses with their huge windows. We no longer have to press our faces to small openings - perhaps taking turns for the one with the right angle - to catch glimpses of events in the world around us.

Now, any small movement catches the eye. We have but to turn our heads to watch a herd of deer making their silent way across adjacent flats, the swoop of an owl on some hapless vole, a tumble of fighting marten or a slide of otter. Or bear in their many routines of exploration, play and predation.

Sea-lions spy-hop to see what we're up to, whales swim so close we can look down through the windows to watch their passage, watched seals clowning and cavorting a boat-length away.

Once a pair of otter in the water alongside spent an hour in passionate (and somewhat rough) love making, triggering... well...

Time to draw the curtains!

PS. Here are some more  looks out the windows while underway.

Wish we had a panoramic camera!

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