Wheelhouse windows

Mark, agree on the forward rake windows, they were designed for one purpose only and that is to give a better view of the deck below and not seaworthyness. The V shape created between the forward sloped glass and a cabin top or even a vertical cabin wall lessens the immediate escape route of green water effectively greatly increasing immediate impact pressure and i wouldn't be shy to say maybe up to 3 times the amount(maybe more)(there should be specs. on this in marine engineering teck books) when compared to a stern sloped windshield where the water is not trapped but is directed skyward releasing pressure. Never underestimate the heights reached by green water especially that not too uncommon rouge wave. I was on a big ferry boat some 30yrs, ago and we got hit by a rogue wave that took out a forward facing cafiteria window badly injuring a man and his wife. This window was 50feet above the waterline. The other item i am very leary of is what we call an eyebrow over the windshield, this is another trap for green water. One of two results "CAN" occur from the pressure of trapped water here, either the aft, sloped windshield implodes or the eyebrow is pealed back damaging the integrity of the cabin structure. When i see these it gives me an uneasy feeling, i don't know why it is not manitory to design them as a removeable or breakaway unit. Geo.

A yacht is not defined by the vessel but by the care and love of her owner

 

A well arranged eyebrow will either be set on hinges or lightly built as to break away clean. I like eyebrows on power craft and all of my eye brow designs have been either of the above mentioned types. Both styles can be designed to not threaten the ship, but release when forced.

 

Electric glass anyone?

 

PAR, like most threads on this forum one never knows how the simplest statement or concern is shared by people who actually build into their designs safety features as you have done on the eyebrow. I am a great admirer of the eyebrow, I think it just adds class to the look of a wheelhouse but at the same time was always leary of the damage it could cause. Most i have seen were on expensive yachts and i can assure they were not meant to breakaway. Maybe it's just being over cautious and i've never heard of a boat sinking as a result, but the potential is there. Included is a 21 ft lifeboat to a little pocket motorsailer conversion myself, the owner, and his good friend built and it is just crying for an eyebrow but not being a designer i thought fellow boating people would scoff at a breakaway unit but after your reply it will be installed this spring. A nice rounded smoked lexan unit. William Hann look out there's a new kid on the block I'm a big fan of his, Waterwitch being my favourite. Thanks, Geo.

A yacht is not defined by the vessel but by the care and love of her owner

 

Yep, not seen on production craft, but custom offshore stuff, it's not as uncommon as you'd think. You already have a solid cabin, so half the work is done.

 

Neglicted to mention this in my last post, For economy and super strength, it's not necessary to use glass, On this and a few previous builds I simply used a two sided foam tape on the outside of the opening and attached a window made of lexan. I use 1/2 lexan, round the corners and 1/4 route all the edges leaving a 1/4 flat edge shelf to serve as a convenient adhesive surface for a circumfrencial bead of 3m5200 after it is installed. The lexan is cut approx. 1 in. larger than the opening with the fastening holes drilled slightly oversize to prevent stress cracks due to heat expansion and minute flexing of the superstructure. The stainless robinson head(square head) or torque head screws shafts are 5200 coated and their heads are fitted with a sealing washer and are just snugged in enought to create a good seal. The whole install looks quite nautical when completed. Lexan has good and bad features, it is extremely strong and can be easily cut, shaped with standard woodworking tools and can be cut to almost any shaped opening. It can be heated to conform to compound bends but be prepared to experiment. The downside is while resistant to scratching it is subject to and care has to be taken. For cleaning i use the popular, fighter jet canopy and motorcycle windshield polishing cleaners. The other problem is it has a poor resistance to windshield wiper abrasion, especially if accidently run dry. It will eventually become less clear due to very fine abrasion but is simple to replace. I've easily gotten 5 yrs. plus life before changing and it's usually the windshield first. A note here, do not use plexi, it will physically fog(turn cloudy). Lexan a good temp. alternative to a long wait in line delivery or for the cash strapped back yard builder to get out on the water with a while not perfect but an extremely strong alternative. Geo.

A yacht is not defined by the vessel but by the care and love of her owner

 

I try not to use Lexan for windshields. It's just not the right material for the reasons you mention and considering it's cost, better well last more then half a decade. I also dislike drilling holes in Lexan for mounting. I prefer a metal, 'glass or wooden ring, that captures and trims out the port glass, also containing the fasteners to hold it down. I have slightly notched the edges of the port glass to let the fasteners live as close to the edge as possible, for a smaller retaining ring foot print, but holes in the port glass are just a crack or leak waiting to happen. It's also wise for deep water work to make this trim ring with an exterior flange that can receive a cover, possibly another piece of port glazing or maybe plywood, what ever to use as the storm shutter.

 

For sure on the trim rings but very hard to find or make with the corner radii, in rural or low marine manufacturing areas (back yard boys on tight budgets) we did make a tight fitting exterior plastic ring for this one to add compression strength to the outside edge of the lexan fastening screw run and it seemed to work ok thus far,(4 yrs). It also adds to the looks matching the ports. Geo.

 

With the advent of HDPE, UHMWPE and casting highly reinforced 'glass port rings aren't as difficult to make as they once were. You can mill them fairly easily from the hard plastics. Casting one is time consuming, though not especially difficult. Even machining one from a dense hardwood is something the back yard builder can do. Deep water parts, by the nature of the job they must preform must be tough, which usually means costly. This is true about nearly every aspect of a real ocean capable yacht. In other words, and as I'm sure you well understand, if you desire heavy weather survival and some redundancy, it's a bit more then the crap seen on a harbor queen.

 

Exactly,(god got to do a one liner finally) Cheers Geo.

 

TSG (Toughened Safety Glass) is the preferred choice for windows. Where materials other than toughned glass is to be used, it has to be increased in thickness. The following is a guide for the thicknesses of TSG in front windows where the aspect ratio is not greater than 1.8.
Area m2 Thickness, mm.
Up to 0.46 6
0.47-0.80 8
0.81- 1.00 9
1.00- 1.25 10
1.26 and above 12

Where the thickness correction factor for aspect ratio greater than 1.8 is to be 1.144.

Minimum thickness for front windows is 6 mm but can be reduced for side and aft windows. Aft windows is the the thinnest among the group as it is not subjected to wave slamming.

There is also a minimum radius on corners, 80 mm. if memory serves me.

Glass must be supported by rubber or elastomeric compound to account for difference in thermal expansion and for weatherproofing.

Raked windows are to eliminate glare and water drips as PAR has mentioned. If raked windows are not preferred, Eyebrows, Storm shutter, awnings are to be of sufficient strength so it does not break when a wave slams into it.

Consider also curtains in the interior to cut down on heat buid up, vents on the pilothouse and opening/sliding windows.

 

It has occurred to me on several occasions that raked windows are often accompanied by a Portuguese deck, which could easily transform into a protection for windows in foul seas. I've never seen it, but the concept should be intuitively obvious.

 

What say you to Dashew's vertical windows on his Fast Boat series?

 

Fair seas?

 

Rxcomposite, good specs and from a private build point of view where funding is always tight and where we are luckey enought to find used marine windows we can certainly make use of the numbers. However in most cases that is not the case we use altenatives and lexan fits the bill. While lexan is not cheap it is less than standard or customized sizings by about 1/4 when following the impact strength requirements.That brings up the other topic, Your quote i assume from an engineering text. "that eyebrows must be strong enought so as not to break when a wave slams into it" is very vague on one of my pet peaves regarding this feature on wheelhouses. Is there to your knowledge any studys done on the increased pressure on vertical or aft sloped forward facing windows as a result of green water being trapped from immediate escape between the eyebrow and the window. If the eyebrow is engineered not to break away then the strength of the window glass,it's frame and fastening system must have to be increased by a majour factor to compensate to prevent implosion. I.E. as compared to a window sans eyebrow. Logic would require that one couldn't use the same specs for a (forward sloped) verses a (straight) verses an (aft slope with fixed eyebrow) verses an (aft sloped with a engineered breakaway or hinged eyebrow) verses just an (aft sloped with no eyebrow). The latter of course properly installed and to specs. being the most seaworthy. This also beggs the question when these specs were obtained what was the orientation of the window in the lab, i would assume vertical. While these queries are getting into details maybe not forseen by the thread, i think before anyone can recomment wheelhouse windows we have to get into the details of size, orientation,add on factors, before strength can be recommended after all it was a window failure that played the majour factor in sinking of the oil rig Ocean Ranger i suspect has caused the sinking or near sinking of a great many more vessels big or small. It's a subject that i'm very interested in being a great fan of the motorsailer style and it's ample window area. Is there anyone out there that can supply detail info on what should be used for window strength verses the scenerios i have bracketed above, Please not just vague statements but engineered specs or factors of strength using the vertical orientation specs as the base reference. Tnx. Geo

A yach is not defined by the vessel but by the care and love of her owner.