Wheelhouse windows

Viking North,

The figures I gave are base numbers from Lloyds Rule and also DNV. It is a guide made on probability studies to support their rule. Should there be a need, there is a computation regarding the relation of window thickness to its position (forward, sides, aft) and its relative height. The higher the window, the less likely it will be hit by a wave, hence the thickness can be reduced.

You talk about "private build" and "used windows" and "Lexan". That's precisely the point. To guide you in choosing. The class rule has tables on substituting Polycarbonate or Lexan against TSG. You can pick a used window but be sure it is the correct thickness.

We follow the rule and it has saved us on one occasion. We were delivering a 12 meter brand new vessel and the weather caught us. A freak wave slammed onto the bow,then buried the front windows. The only casualty was a lost windshield wiper and a VHF antenna. No life lost.

There is no study I have come across sloping windows against wave slamming but it is obvious from the profile that a trochoidal wave with a more or less a 45 degree angle would hit smack on a forward rake front facing window more than a backward sloping window. A backward slope would progressive hit the foot of the wave before the crest. Total pressure would be the mass of the wave x its velocity, roughly.

 

Ok, good stuff, certainly confirms that a forward sloping window or a window with a solid eyebrow is more subject to damage and one should overbuild by a certain factor if either is incorporated in a build especially where it is close to sea level or better yet avoid the forward slope and only make use of breakaway eyebrows where ever there is a real probability of encounter big boarding seas. You have confirmed my concerns with both and one should not only be vigilant of proper window strength but also the physical orientation of the design. Ok my choice, stern sloped windshields, and if equipped with an eyebrow make it hinged , breakaway, or if pratical removeable for heavy weather. Thanks, Geo.

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

 

Wave Spectra

Here is a graph on how the wave develops. I am still searching for the graph with the rouge wave for the proportion.

 

windows

Hello
My first post here. Does anyone have pictures of lexan window installation? A picture is worth a thousand words... so they say.
Alan

 

Alanf, the economical system which i have found works just fine if you have a clean level surface and care is taken on giving ample edge distance(1/2 to 3/4 or even 1 in) when drilling the oversize fastening holes in the lexan and not to overtighten the fasteners. All three important (edge spacing)(oversize holes)(torquing). Read my post #21 and see photo on my post #19 both on page 2 of this thread. Click on photo to enlarge.
Also for a stronger more professional but more costly install however better for blue water work( extra slot for shutters) read PARS's post #22, page 2.
And for the proper thickness of the material to use refer to RXComposite post #26, page 2, on glass but also how to obtain info on alternative materials.
If you want more detail on how i did my install you can e mail direct and i can expand on the info. salr@eastlink.ca, Geo.

 

PAR, while replying to the above post, re read you #22 post and picked up on a missed piece of good info. You mentioned metal rings with an extra slot for storm shutters. Do you have the name of a supplier who will supply just window flanges where one could cut and install one's own glass or lexan or if they are an exclusive supplier to you are they available for resale.This would be more economical than purchasing fully assembled window ports. Tnx. Geo.

 

Greeting,

Two reasons for vertical upright windows.

1. Aft slanted windows allow excessive sunlight to enter interior causing hotspots and glare when viewed through. This alone if considered for helm area would make it unaccceptable.
2. Aft slanted windows are more prone to leaks even if built watertight, UV rays breakdown sealant materials along with possible standing water eventually entering.

 

RXcomposite, The wave dynamics certainly tell the story. Upon inital impact without obstructions(forward cabin edge) causing the wavefront to trip (tilt on an axis point) the inital pressure is primarly horizontal then following in time with vertical pressure as a result of the increasing height of the front. The vectored result would play hell with a forward sloping window. The perfect angular destructive force of nature attacking a poor design of man. Not exactly blue water stuff for sure. If forward cabin structure did cause the wave to trip it could lessen the pressure somewhat but i don't think it would be that much of a reduction,especially for a big bording sea. An eyebrow would feel the same effects with possibly more pressure(on aft sloped windows) due to higher captivation of the water. The eyebrow to window angle being more critical than on a vertical or forward sloped window. All the more important to make the eyebrow breakaway,hinged or removeable.
I have another small question, is the LLoyds specs regarding marine windows on line?
Thanks again for the good info, certainly has enhansed my knowledge of this topic of window orientation and the importance it plays in seaworthyness. I've always been leary of forward slopes and eyebrows but it's good to see it confirmed by info. Not to say it would cause a sinking but planning in a design helps to keep the odds againt it and if an owner of a vessel with such designs it 's good to be aware of the possibilities and prepare easily installed shutters for blue water work, probably not a bad idea in either case. Tnx. Geo

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

 

Goodwilltoal, agree,that combined with the above info is enought to make one(excuse the pun) SHUTTER. ( god another one liner and on the same thread)Geo.

 

Yes, i would certianly expect in those cases the deck and water visibility would far outweigh the increased risk of water ingress, in both cases it's a necessity for the overall safery of crew and rescue operations. Like all in life it's a tradeoff . Thanks to Mike for the info and thanks to you for forwarding. Geo.

 

"I would like to point out that forward rake windows is not a bad design. DNV rules on Patrol boats requires the front and side windows to be reversed angled and most of the tugboats I have surveyed have windows angled forward." - It is bad design and has to be accounted for with heavier glass. It is specifed for improved visability, not for improved ability to take a wave.

 

Just to point out that due better visibility forward raked windows don't need as much area as sloping ones do and that pretty much counter weights possible disadvantage of taking a wave. That too depends how the wheelhouse and it's windows is placed in the superstructure etc...

 

Teddy,you have carefully read all the posts including the wave dynamics and you still conclude forward raked windows are just as safe as reverse raked ??? From your past posts on different threads it's not your pattern to come to that conclusion. Also from all the installations i have seen the forward raked windows are up to 1/3 larger than their counterparts for the same size wheelhouse, it is not the norm to see otherwise as they have to increase the vertical height to get the same view upwards. (any overhang blocks the upward view plane.) Forward superstructure can break up the boarding sea somewhat but there's always that big one and both you and i know sitting at the wheel which slope we'd prefer. Geo.

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

 

Nope! that's not what I said. I said it's not so simple as you suggest and depends of many other factors too..
BR Teddy