How Safe Are These?

Discussion in 'Boat Design' started by CatBuilder, Dec 25, 2011.

  1. CatBuilder

    CatBuilder Previous Member

    Interesting. What about the way these polycarbonate panels are fastened to the hull and different rates of flex between the hull and window? Any idea how this is overcome?
  2. Boston

    Boston Previous Member

    a floating gasket would work OK, Poly has a huge flex so through fasteners are a big mistake. Stuff is very strong though, also 3M has a shatter proof film that really adds to strength, but it scratches pretty easily so only use it on the inside.
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  3. michael pierzga
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    michael pierzga Senior Member

    The windows will be bedded into "goo ". Locally we use a sika flex or Bostik product plus a primer for bedding windows. Always a problem is UV passing thru the window and burning the compound. Also consider that a window will be a hard spot in a flexible hull. Dark painted hulls seem to have more window issues than white hulls.

    This goo joint takes abuse. Insure that you have plenty of surface frame area for bonding. Fastener thru the window dont work...point loading.... and leaks

    If you are contemplating a window contact the specialists...the window supplier and the goo supplier for " best practice" fitting advise.

    I am rebedding a glass pilothouse window this week...very much work.
  4. PAR
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    PAR Yacht Designer/Builder

    I also agree with Whitepointer. The problem isn't the lights, so much as the intention of the design. What most are having issue with isn't the light, but it's location and size. Personally, I don't put lights in certain portions of the hull on off shore craft. I stove one in many years ago, on a hard slosh in a storm and barely made it to port.

    Most designers, will not jeopardize a particular design with questionable light scantlings, sizes and locations, but then the marketing team gets a hold of it, in the production yacht world of thinking and you just can't tell what they'll do. Custom designs typically don't suffer these indignities, unless they're specifically intended to be harbor queens, of which the great vast majority of production craft are.

    As to lights in hull shells, well this is okay, if sized and placed according to their expected station in life. No one would question a houseboat with square meter lights down it's flanks, simply because everyone knows full well, it'll never see conditions that might stove one in, except in an accident, of which all can't have an eventually planned for. On the other hand, anything that's capable of venturing into conditions, that might stuff a light onto the settee shelf, should be located, sized and spec'd appropriately.
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  5. viking north
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    viking north VINLAND

    Ask yourself one simple question and the logic will flow. Would you install roof windows(skylights) in a new home build in an area prone to golf sized hail stones. In addition to the tons of per square units of storm water pressure the sea also has it's variety in shapes and sizes of impacting hail stones. Nope don't do it, if it's light you require take a lesson from the old guys install hatches or deck prisms---

    A yacht is not defined by the vessel but by the care and love of her owner---
  6. troy2000
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    troy2000 Senior Member

    Hey... it's a bedroom. If you're asleep, you don't need light. And if you're awake and need light to figure out what you're playing with, you have bigger issues.:D
  7. Boston

    Boston Previous Member

    another interesting thread folks, I'd have thought you guys would be discussing the various light types available these days and how you might get away with using them in certain areas. Who'd have guessed you were all such purists ;-)

    Kinda makes me want to go bust out the eraser on a couple of these sketches,

  8. aranda1984
    Joined: Jan 2010
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    aranda1984 aranda1984

    Polycarbonate windows

    Two layers of 1/2" polycarbonate panels will stop a 44 magnum bullet.

    It is the window mounting for the large area that we have to worry about.
  9. Boston

    Boston Previous Member

    not twice they won't, I've schlepped glass for a long time and you gotta use 3M's blast resistant film if you want to escape multiple shots. Otherwise large shards just fall out leaving a big fat whole in the light. Laminated polly its ok but its nothing like if you use the shatter proof film.

    Polly also is damn sharp and can cause serious injury if not encapsulated with shatter proof film
  10. CatBuilder

    CatBuilder Previous Member

    Hmmm.. good points about polycarbonate. That stuff is pretty strong. I would think it's as strong as epoxy, since it's made of the same Bisphenol-A, just reacted with a different "hardener." (Phosgene instead of amines)

    Very similar composition though.

    The attachment point (as shown in Richard's picture way back) would seem to be the part prone to failure.
  11. PAR
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    PAR Yacht Designer/Builder

    I disagree George, you engineer for the tasks and demands involved, not the fears of the owner. A sky light over a bedroom in a hail stone/storm prone area needs to be a tougher sky light then one rated for life in a desert.

    It's dangerous to cross rivers with a bridge, so maybe we should just swim, because boats can sink . . .
  12. eyschulman
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    eyschulman Senior Member

    It is no mater how strong the individual parts of the hull lights, its how strong the whole. What good is an intact window laying on a berth three feet inside the original position. Has anyone tested these large windows and compared to the hull without same? probably not. from the size and position of the units now becoming common I doubt any kind of strong sea cover could be fitted.I have had the oportunity to observe first hand and close up the immense power of cresting 60ft waves dont under estimate hydraulic force.
  13. viking north
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    viking north VINLAND

    PAR-- Just my old school brain --"why take the chance" . As you well know,Every hatch, port,thru hull, thru deck fasteners, are potentials for leaks and problems, why add to the headaches by cutting away half the hull structure and install picture windows. Here I am tearing my hair out on how far to push the size limit on my wheelhouse windshield /side windows and out there in interior decorator land they' re installing panoramic see thru TV screens in the sides of hulls. Oh well different strokes for different folks.
    Don't like roof windows either,but have 3 in my house entrance way, their R3 to R5 factor is nothing but a total fkn waste of energy. Funny story--friend of mine had one busted by a sea gull dropping a big mussel shell on it. A change in texture from their usual droppings. :D
  14. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Personal preferences have little bearing on the actual engineering and safety margins employed in the various systems of debate, be they ports, lights hatches, etc. The prudent course is minimalizing everything, which is much safer, but you're sailing in a dungeon. Large ports or lights don't belong on off shore yachts, but lights, ports and hatches can enjoy the benefits of modern materials, engineering and building techniques.

    I personally have 3M ballistic film on the 29 windows of my home. I was forced into this by the one that must be obeyed, when she learned of it's effectiveness. I don't think it's necessary, but it makes her feel better and hell, I didn't have anything better to do with the $3,800 bucks it cost to have it done.

    I think if you can make it fall within reasonable safety guidelines, then go for it. The extreme majority of owners will never see conditions that will stove one in, though JimBob and his half brother/uncle JoeLarry might back it into a bad situation, of which you just can't predict, from an engineering stand point. On the other hand, a singlehanded, offshore record setter should consider no lights, maybe just prisms and bubble dome, but the average yacht owner isn't going to remotely consider this as a potential harbor queen for his new, half his age trophy wife to sun bath on.

    This brings us to the real point of the debate, which is 95% of these yachts will spend 98% of their lives, tied to a slip without anyone aboard. On the rare occasions they are used, it'll be in 10 to 20 MPH winds, near shore with drunken friends aboard, who are all amazed at the sailing skill of the owner. The lights will will dance magically across his fat sister's belly, making her surprisingly more attractive then usual and possably she get some this year, rather then be the frustrated shop and eatoholic she normally is. This is the whole point of living my friends. Braving adventures through near hurricane force storms, isn't what most seek or desire, nor should they need or desire a yacht (or it bits) that can tolerate this. This is the line that the design team at all production builders must tread. It's a difficult thing to do and not develop a floating tank. Hatches should tolerate a 200 pound man falling on one, but what happens if your brother Clem, the thyroid issue 425 pounder, falls on one? When do you say enough is enough, so that the harbor queen can be reasonably affordable, considering it's eventual station in life.

    In my way of thinking, anyone considering major passages, need to look at passage makers, which typically will be more robust in nature, across the board. For everyone else, a dainty lights harbor queen is just fine and baring JimBob backing down on you in the middle of the night, you'll probably be just fine. You can walk around with a hard hat on the rest of your life, just in case a small anvil falls from the sky or you can just take your chances.

    Lastly, everyone knows that Nova Scotia Sea Gulls are a lot more anal then the rest of the east coast gulls George, so get some ballistic film up there.

  15. whitepointer23

    whitepointer23 Previous Member

    i have been reading a few magazine boat reviews this week and they back up everything in your post par. the boats i read about were french and one from china, while they put in the usual facts about handling and mechanicals there seemed to be a lot more emphasis on dockside comfort . these people could save a fortune if they left the engines out and just have a boat shaped water front apartment.
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