Concerto
Well-known member
Having read the thread and links, I have some further comments to make.
I am not against hull windows. What I see as the problem, is relying on bonding alone. In my opinion mechanical fixings should be used in conjunction with bonding. The material of the windows is not a problem and is strong enough.
Comments about aircraft windows being bonded only, seems to be a false claim as in post #17 of this link https://www.pprune.org/rumours-news/655290-titan-a321-loses-windows.html shows a photograph that the windows are mechanically fixed and they are multi layered, and in the incident discussed talked about the outer layers of 3 windows being lost.
Car windscreens have been bonded for some considerable number of decades, but can still fail. My own car started a leak at the top of the windscreen at about 6 years old and it had never been in any accident. Fortunately for me the glass cracked a few months later after a large stone hit the screen. Cars do flex and in my case the bonded windscreen failed due to this.
The link to Sirus yachts and their windows was interesting to read. How strong are the hull windows on a boat? They predict their yachts should last 100 to 120 years, yet they also comment that the windows may require removal and refitting from time to time. They do not mention what time scale this should be. Should it be every half century or every decade, so the comment was not that helpful for potential owners. They certainly do not guarantee the windows for the life of the yacht.
Every hull that has hull windows should be reinforced in the recess to ensure no flexing should occur. However the hull can be subjected to many forces that can cause flexing. The windows are fitted before any rig is fitted and tensioned. Heavy seas can subject them to weighty loadings. Berthing alongside a marina pontoon or wall in rought conditions can apply repeated loadings that will cause localised loadings. A hard grounding like hitting a rock can flex the hull. Even once lifted out of the water a hull will change shape as it is no longer supported in the same way when resting on its keel and chocks. All of these situations will cause some flexing of the hull, and could start the breakdown of the bonding. Most of these problems I have experienced on different boats.
I am not against hull windows. What I see as the problem, is relying on bonding alone. In my opinion mechanical fixings should be used in conjunction with bonding. The material of the windows is not a problem and is strong enough.
Comments about aircraft windows being bonded only, seems to be a false claim as in post #17 of this link https://www.pprune.org/rumours-news/655290-titan-a321-loses-windows.html shows a photograph that the windows are mechanically fixed and they are multi layered, and in the incident discussed talked about the outer layers of 3 windows being lost.
Car windscreens have been bonded for some considerable number of decades, but can still fail. My own car started a leak at the top of the windscreen at about 6 years old and it had never been in any accident. Fortunately for me the glass cracked a few months later after a large stone hit the screen. Cars do flex and in my case the bonded windscreen failed due to this.
The link to Sirus yachts and their windows was interesting to read. How strong are the hull windows on a boat? They predict their yachts should last 100 to 120 years, yet they also comment that the windows may require removal and refitting from time to time. They do not mention what time scale this should be. Should it be every half century or every decade, so the comment was not that helpful for potential owners. They certainly do not guarantee the windows for the life of the yacht.
Every hull that has hull windows should be reinforced in the recess to ensure no flexing should occur. However the hull can be subjected to many forces that can cause flexing. The windows are fitted before any rig is fitted and tensioned. Heavy seas can subject them to weighty loadings. Berthing alongside a marina pontoon or wall in rought conditions can apply repeated loadings that will cause localised loadings. A hard grounding like hitting a rock can flex the hull. Even once lifted out of the water a hull will change shape as it is no longer supported in the same way when resting on its keel and chocks. All of these situations will cause some flexing of the hull, and could start the breakdown of the bonding. Most of these problems I have experienced on different boats.
