Big windows - dangerous in an ocean-going yacht ?

There's Lexan and there's Lexan, and then there's people who ruin their Lexan by using the wrong cleaners on it.

First, you don't just want to go down the the plastics house and buy a sheet of Lexan. You want Lexan with what is called the "Margard or Lexgard" coating. It comes in one or two sided versions (get the two sided stuff). The Margard or Lexgard is a ceramic coating that greatly improves the scratch resistance of Lexan. This is what is used in transportation applications and is why somebody earlier was saying they had good results getting used sheets from older buses.

Polycarbonate sheets, properly installed are much stronger than plexiglas since they bend and don't break. The thickness has to be consistent with the size of the window, and obviously the bigger the window the stronger the framing has to be to support the sheet. Lexan isn't as stiff as plexiglass so you can't gorilla torque it in, if you do it will crack or split on the edges, and it should have a bit more distance outside of the bolt locations than plexiglas. Still, polycarbonate is amazing stuff, and done properly is a whole world better than plexiglass.

Finally most of the damage to Lexan is a result of improper cleaning. You need to be careful what you use to clean uncoated Lexan. If you use Windex it will ruin it in short order and fog it up like crazy. Margard or Leagard sheets can be cleaned with Windex or other alkali cleaners, but if you don't know what you have, you shouldn't use Windex or an alkali cleaner on it.

 

Boo2,

So, what do you think about big windows now?

Again, why do you ask?

Tom

 

There is no problem - - - - except if it is open, broken, or it is where someone is peering through at you and his wife hehehehe....

 

Ive seen cats with what looks like a normal hatch like a lewmar just above the water line.

This is crazy, ---I know its supposed be an escape hatch but if that pops out your safety hatch will be the reason for your death.

A hole of that size suddenly appearing in the hull will fill that hull with water so quick.

 

Though I have been aboard vessels that got their windows knocked out, I was too young to now be qualified to talk about causes. I thought it was cool (And I didn't have to pay for the damage)!
Where I can contribute a bit is on design of small craft. I have fully dipped the front of my boat perhaps half a dozen times and my aft raked forward windows didn't take much of a hit (one time even with a four inch dia., two foot long log in the wave). In like seas, I have witnessed many west-coast style (that's what we call forward raked here) get wasted or popped out. Also, poorly framed or poorly fitted glass in rubber frames is at fault for flooded cabin in this circumstance almost every time. Rubber fitted windows should be...fitted. Not tight/not sloppy. Laminated safety glass (like in school busses) of, I believe 5/16" is good, tho I am personally going to install thicker to better withstand a whack from a lead weight (I have never broken a fixed 5/16" laminated window in rubber frame). Sliders break easily on the unsupported edge.
Also, using ur head helps. Today we had a pretty good blow without much fetch which led to perhaps five foot coamers in areas. Some boats, impatient to get through a rippy area charged through - one shipped several waves, I waited twenty minutes for the tide to change and went through in maybe three footers, feet on dash, coffee in hand. As I recall, the thread was about ocean going but though ocean stuff tends to be farther apart, thinking still applies.
Larger windows need to also be thicker.

 

Frosty, That just shows the potential stupidity in trying to regulate safety, Those "escape hatches" are required for boats that race.... Mine will have them, but if enough water gets inside, with the "escape hatches" open, the water should drain out to the lower lip, then is easily bucketed of pumped... The hatches are under the bridge-deck and convenient places for ablutions or fishing.... I think mono's may be required to fit them, - escape hatches, - (if not already), as there have been more of those arse-up of recent times than multi's...

 

A lewmar hatch is bonded in like any other is.

At 4 in the morning in a howling gail I don't want to be thinking about those things being sucked out then you got 2 foot hole in your boat.

Under the bridge deck isnt too bad. But its those that are 6 inches above the water line.

 

The trouble is , "the regulation is the regulation", and must be implemented if one desires to race, even if only occasionally......

 

A friend tried to sail around the Pacific with marguard. He left from BC, and by the time he got to San Francisco, the marguard had fallen off like old varnish, and he spent he rest of his Pacific circumnavigation looking thu totally fogged up windows. Others I've met have had the same experience. He has since switched to plexi, and has had many trouble free years with his plexi windows.
Walk down the docks in any marina, and you can recognise the lexan windows from a long way off. Any over three years old are totally fogged up.
Having recently tried, unsuccessfully, to get a 6 inch by half inch thick plexi window out of a port with a sledgehammer, without even breaking it, I don't worry anymore about the strength of half inch plexi.
I had a dome once. Wrong shape. Too much glare to see much out of it, even when new. I'd prefer to make a stainless frame up, with four glass windows and a glass top sika flexed in. These you can change one at a time for a fraction the cost of a dome ,and do it anywhere. Better at keeping the burglers out too. A dome is an invitation to thieves.
Brent

 

Brent I suspect if your 1/2" plexi port was 24" square, and you smacked it with a sledge, it would offer up a different result then the little port you tried to break. This is precisely the issue with larger ports, you just can't make the frames big enough, once you get past a certain amount of free span.

 

True, but the sledge hamer on the little port still said a lot about the strength of plexi, given it didn't even crack.
Brent

 

The tests I did on perspex had the same effect, you really had to put yourself out to break it. 3mm breaked quite easily, 6mm became tough, then 8mm and thicker was something else. Glass wouldn't have come close.

Let's face it, large windows are nice to have. So what requirements would still allow them, stiffer structure, bigger frames, what else ?

 

Lets just say a strong steel framework every 18 inches to support the rigid window frame? - just a ridiculous thought.... - Oh by the way Fanie, "redback" have not replied to me either.... either I am too unknown or my reputation precedes me?

I think I might be better at sticking to economics, as there I can blame it on consulting the wrong witch...

 

a few years back a full sized ship, german was hit by a massive wave which broke 100 ft up , , it stove in the bridge window, and the mains stopped, she lay broadsides on, the engineers managed to start the mains and head her upwind again; the master said, one more wave would have capsized her
no craft is strong enough in the window department IF the seas are big enough, I guess that says it all
this was in high lats South
i read lots of stuff on the forum from folk who have never crossed oceans, believe me it can get like this, see under
some

Encounters

* On 10 October 1903, RMS Etruria was only four hours out of New York when, at 2:30 p.m., the ship was struck by a freak wave. The wave was reported to be at least 50 feet (15 m) high and she struck the ship on the port side. The wave carried away part of the fore bridge and smashed the guardrail stanchions. There were a number of first-class passengers sitting in deck chairs close to the bridge and they caught the full force of the water. One passenger was fatally injured and several other passengers were hurt.
* In 1933 in the North Pacific, the U.S. Navy oiler USS Ramapo encountered a huge wave. The crew triangulated its height at 112 feet (34 m).[13]
* In 1942 while carrying 15,000 American troops 700 miles from Scotland during a gale, RMS Queen Mary was broadsided by a 28-meter wave (92 ft) and nearly capsized. Queen Mary listed briefly about 52 degrees before the ship slowly righted itself.
* In 1966, the Italian liner Michelangelo was steaming toward New York City when a giant wave tore a hole in its superstructure, smashed heavy glass 80 feet (24 m) above the waterline, and killed a crewman and two passengers.[13] The matter is related by Daniel Allen Butler in his book The Age of Cunard and by Walter Ford Carter in No Greater Sacrifice, No Greater Love.
* The Wilstar, a Norwegian tanker, suffered structural damage from a rogue wave in 1974.[13]
* SS Edmund Fitzgerald was a lake freighter that sank suddenly during a gale storm on November 10, 1975, while on Lake Superior, on the Canada–United States border. The ship went down without a distress signal in Canadian waters about 17 miles (15 nm; 27 km) from the entrance to Whitefish Bay (at 46°59.9′N, 85°6.6′W). At the location of the wreck the water is 530 feet (162 m) deep. All 29 members of the crew perished. A coast guard report blamed water entry to the hatches, which gradually filled the hold, or alternatively errors in navigation or charting causing damage from running onto shoals. However, another nearby ship, the Anderson, was hit at a similar time by two rogue waves, and this appeared to coincide with the sinking around ten minutes later — or at least contributed to the sinking if the Edmund Fitzgerald was already in trouble as suggested. A Discovery Channel reconstruction pointed a finger towards freak waves as the cause.
* In October 1977, the tanker Stolt Surf ran into a rogue wave on a voyage across the Pacific from Singapore to Portland, and the engineer took photos of a wave higher than the 22-meter bridge deck.[14]
* The six-year-old, 37,134-ton barge carrier MS München was lost at sea in 1978. At 3 a.m. on 12 December 1978 she sent out a garbled mayday message from the mid-Atlantic, but rescuers found only "a few bits of wreckage." This included an unlaunched lifeboat, stowed 20 metres above the water line, which had one of its attachment pins "twisted as though hit by an extreme force." The Maritime Court concluded that "bad weather had caused an unusual event." It is thought that a large wave knocked out the ship's controls (the bridge was sited forward), causing the ship to shift side-on to heavy seas, which eventually overwhelmed it. Although more than one wave was probably involved, this remains the most likely sinking due to a freak wave.[7]
* 1982, Ocean Ranger, an offshore dilling rig capsized. Blamed on a rogue wave reported by a nearby rig.
* Draupner wave (North Sea, 1995): first confirmed scientific evidence
* RMS Queen Elizabeth 2 (North Atlantic, 1995), 29 meters, during bad weather in the North

 

Although I can attest that rogues do, indeed, exist, the vast majority of these happenings are exaggerated to make a better story. I saw a special on rogues on TV. In it, I believe, a Swedish guy used a tank and wave makers to try and get differing wave patterns to combine to form out-of-proportion waves. He suceeded.
I have seen waves of perhaps 250% the mean in a given set - Shocking, yes, but even on the East side of Africa with the freaking HUGE waves born of the monsoons, it is arguable that a guy should time his trip better. What the heck was the cruise ship doing broadside to potential seas and what were passengers doing on deck? Why did the Edmond leave hatches open?
I have spent months at a time without landfall in the Pacific (never in a typhoon - I wasn't that stupid or at war), put perhaps 70,000 miles along the Aleutians and avoided passes when currents opposed big seas, F'ing fished for crab in 40 footers in the Bearing Sea in winter, escorted tankers to Cape Hintchenbrook, Prince William Sound, in 30 footers and estimated 140 kts. of wind (The anemometer slammed so hard at 90 that it bounced to zero then stayed at 90 for over 15 minutes, both RADARs, rated for 120 kts, failed at once - then the whine and clatter turned into a deafening groan. I have no way of knowing how hard it was actually blowing but the seas quite flattened out in the short fetch and visibility was such that we nearly collided with another escort tug, 140' long and safety orange colored - we didn't see it until it was just a couple hundred meters out. Since 1989, the maximum wind for tanker transit is 45 kts. and seas to 15 feet), came close to dying twice near the Trinity Islands (southern end of Kodiak) in breaking 25 footers, sandblasted windows to be rendered nearly useless while trying to hide from a blow in a cove, and turned around upon facing 60 foot hell on the Columbia Bar.
I believe that I am qualified to say, in my world, weather can, and should, simply be avoided. I understand that the timing might be wrong while at sea, but drive smart and you'll get by fine. Most bad weather is associated with shore, shoals, and associated currents. Plastic? For real?