MV Catapult Windows

Any see-through bits
groper
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MV Catapult Windows

Post by groper » Sun Jan 13, 2013 1:37 pm

Ok im starting the make the panels with the windows in them... so the front and side windows of the "soon to be" saloon...

Any advice on how to go about it?

So far im just thinking of cutting the foam core to shape and glassing one side. Then flip it over and rout a channel in the foam to insert a glass rope edge around the window openings. Then glass over this to complete the 2nd side laminate.

Any better ideas?

And whats the go with acrylic, the marine surveyor i spoke with reckons its not shatter proof and therefore will not be compliant with the standards - therefore potentially leaving an open door for insurance companies to not pay if something goes wrong... yet i see so many boat with acrylic windows so is everyone running the gauntlet or does this surveyor have his wires crossed?

44c
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Re: MV catapult

Post by 44c » Mon Jan 14, 2013 7:41 am

Not shatterproof? So what, exactly, is? Glass will break, in fact while it's harder to break, toughened glass will just about disintegrate if you do break it. What does he suggest, make your windows from steel?

There are hundreds, thousands of boats with perspex (acrylic) windows. I'd be surprised if the vast majority of production boats weren't using perspex. The windows on 747's and A 380's are perspex. Guess they're uninsured too? :?

groper
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Re: MV catapult

Post by groper » Mon Jan 14, 2013 5:58 pm

Well yes that was my thinking aswell... according to the surveyor, it needs to be toughened glass or polycarbonate - not acrylic.

Ill copy and paste the following excerpt from the AS1799 "general requirements for powerboats"

3.8 WINDSHIELD AND WINDOWS
The windshield and windows shall comply with the following requirements:
(a) The windshield and windows shall be of safety glass or laminated safety glass
complying with AS/NZS 2080, or a material having at least equivalent safety
characteristics on fracture to those specified in AS/NZS 2080.

(b) Windows or ports that face forwards or to the side shall be watertight.

(c) Watertight and weathertight windows and ports shall be constructed and installed so
as to be at least equal in strength to the parts of the boat in which they are installed.

(d) Windshields and side windows that cannot be seen over and are located from forward
to 22.5° abaft the beam on either side of the steering position shall not be colour
tinted and shall have a light transmission of not less than 70%.
NOTE: Typically, grey tints are the most suitable tints to fulfil this criterion.

(e) Every windshield or forward window at a steering position shall be so fitted that in
heavy rain it can be seen over, opened, or part opened so that visibility can be
maintained. Alternatively, windscreen wipers or clear view screens shall be provided.


Now the problem is i dont have access to AS 2080 which is referred to above. If acrylic can pass the same tests in the AS2080 test, then it should be no problem as its mechanical properties can then be shown to meet the standard.

Im really beyond caring at the moment, i think ill just do whatever i want as i dont think anyone will bother to check based upon the millions of other people already using acrylic...

rexd666
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Re: MV catapult

Post by rexd666 » Tue Jan 15, 2013 12:33 pm

I think the standard reference is talking about what happens to the window when it breaks and preventing damage to people from large shards of glass. Both Safety glass and Lam are methods for preventing large shards. Toughened is also stronger under impact than float due to external skin of glass being under stress, except for point loads when it fails with a bang.

I have access to the standard if you want me to look anything up.

Not sure if the tint films like 44C applied adhere to the plastic well enough to simulate laminated glass like behaviour, but I know when applied to toughened side windows of a car it seems to hold the broken window together pretty well.

The question to the acrylic supplied would be does the product meet standards to be used in windows that normally require toughened or Laminate in a building, they are more likely to have run across that.

Steve

mySerenity
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Re: MV catapult

Post by mySerenity » Tue Jan 15, 2013 1:53 pm

Groper
There is some really good meat in this and appreciate you going to the trouble of posting, thank you.

Thanks to you too Steve, just wondering if we should/could relocate this part of the discussion to our 'windows' section, thats if Groper doesn't mind.
James
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https://www.youtube.com/user/puremajek
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groper
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Re: MV catapult

Post by groper » Wed Jan 16, 2013 9:02 pm

No mate i dont mind at all... thing is, the australian standard for yachts is a different standard to that of AS1799 (powerboats). Most of the people involved in this forum are building sailing cats so it may not apply.

Although, i have seen a general tendancy towards this same end - ie. all forward facing glass needs to meet the laminated safety glass standard regardless of the vehicle type - so aircarft, boats, cars, tractors, you get the idea...

Ive chosed to use the toughened glass in my build for the front windows only. Its extra weight i didnt want, but i think the benefits are worth it such as increased scratch resistance, no crazing, better optical clarity and easy to clean etc... the side windows are another story... the surveyor is telling me i need to use polycarbonate, but its double the price...

And id also like to hear more about the window frames and what other people have done here. I would like to make some of the windows opening, so the frames will need reinforcement, extra fibreglass etc would like to hear what others have done.
Also, the cabin of a catamaran sees considerable twisting loads. The cabin forms an intergral part of the crossdeck structure and greatly influences the over stiffness of the boat. If global deflections are not kept low, you can expect to need repairing things like cracks forming in critical high stress areas, such as the junction between the hull and bridgedeck etc. Would be great to discuss more issues like this and work on solutions for better lasting catamarans.

mySerenity
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Re: MV Catapult Windows

Post by mySerenity » Thu Jan 17, 2013 7:58 pm

Thank you Steve

Before we start a frenzy of concern here, 'The standard' is not a requirement for the amateur builder. And the standards vary from country to country.

But its nice to have and see how the Pro's/Survey have to do it. A big example here is the 'floor emergency hatch' on catamarans. Pro's have to provide emergency access in the event a catamaran is overturned, so somewhere in the floor or stair area is an emergency escape hatch.

Having said this, we personally tried to veer towards the standard and in many cases, well exceeded the requirements, but don't have an 'emergency hatch'.

But for those concerned about this standard (that has all of a sudden popped up on the Forum), there is no requirement to comply. Some insurance companies require certain standards to be met and this is where your Designer is the key and they build these into their plans. Their reputations are on the line so they won't do the wrong thing by you.

On the issue of windows, we have 'survey' windows aft and the are SO HEAVY. I now actually regret going that way. The rest are poly-carbonate, which we love.
James
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https://www.youtube.com/user/puremajek
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groper
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Re: MV Catapult Windows

Post by groper » Thu Jan 17, 2013 8:48 pm

No we dont HAVE to build to the standard, but the surveyor said that it would be possible that an insurance company could void insurance on this issue. it would totally depend on whats written in your individual policy

If a boat is not built to an australian standard, then the risk to an insurance company is deemed to be higher. Therefore, you would expect to pay higher premiums.

As my boat was not designed by a "competent person" because i designed it myself and im not a naval architect or shipwright or marine surveyor, I need to get a builders plate affixed before i can get it registered with the transport department. This is where the marine surveyor comes in, he can provide the builders plate as he is deemed "competent" to provide a builders plate after conducting the relevant testing to determine the specs that show on the plate such as max engine HP, max POB and all that crap etc. Its a bunch of pretty stupid on water tests and measurements, stability heel angles, etc etc - very relevant to the safety of trailer boats, but will not challenge the design of any decent +35ft catamaran in the slightest. The same guy also does insurance survey reports. So he provides a detailed general report to the insurance company when i need insurance, and they give me a quote according to whats in his report. If everything is built to an Australian standard, i can expect very little trouble through all of this and a small insurance premium at the end of it... apparently, according to him, acrylic windows dont pass the standard, polycarbonate does. I havnt been able to verify if this is correct or not, but i know of many commercial boats that have acrylic windows in them. i can only figure, that they are either paying higher premiums or their insurance companies dont know about it. Another possibility is that this is a relatively new update to the standards, the window standard was revised in 2005 as far as i can tell, perhaps older boats built before this are not affected by it?

Anyways back to the problem, whats the best way to build a bridgedeck catamaran cabin including the windows and frames etc??? :mrgreen:

44c
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Re: MV Catapult Windows

Post by 44c » Fri Jan 18, 2013 7:49 am

AFAIK, you can get a blank Australian builder's plate by just applying for one. At least that's how it was when I launched, I was all set to get one when I found sailboats don't require them. You just get the relevant details engraved on it.

If you installed acrylic instead of polycarbonate windows, once they are installed how would a surveyor know the difference?

Insurance companies will usually require an out-of-water survey. Best to do this before launch, obviously. My surveyor didn't even look at the windows.

groper
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Location: cairns

Re: MV Catapult Windows

Post by groper » Fri Jan 18, 2013 9:20 am

Another issue id like to discuss, is the radiant heat from very raked back or sloping windows that do not have shading above them. How much of a heat problem in the cabin does this generate? How can we mitigate this problem whilst maintaining a sleek profile and low windage? Theres lots of new designs emerging and i wonder how hot they will be, i like this new one from grainger which employs shading;
Image

How effective are the films in reflecting the heat?

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