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Most boats now use only adhesive for window fasteners, including offshore boats. Modern adhesives can be stronger than the laminates they attach to. But your boat, your call.

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Thats a good question, maybe it was weakened or flexed previously and an invisible fault developed that only surfaced after the recent work in the area. Another question is what action by a boatbuilder could have caused the cracks apart from a sledgehammer :), were there any other potential  factors? Without seeing in person, structurally it looks minor and as I mentioned a very easy repair. What have you been quoted to fix it?

 

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20 hours ago, Ex Machina said:

I did a window replacement about a month ago . I was very surprised at how flexible the area around the window cut out was with the window removed . 

I am taking a guess that the scraping force applied by the worker over 3 days  to remove the incorrect sealant flexed the laminate enough to crack the bog/filler on the inside of the window surround ? 

or a harmonic generated by someone going hard with an orbital sander could also do bad things to that bog on a thin slightly flexible panel.

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I have seen this kind of thing before.
Firstly, it is not structural.
Nor is it the fault of the Yard/person working on the windows. They are correct that it is a build issue, but in saying that, it is not due to poor build quality as such.
Basically what is happening is the Gelcoat has cracked at a point were two substrates have an ever so slight different rate of expansion when heating/cooling. Or one part flexing not quite so much as the other due to Hull movement. We are talking only fractional amounts, but enough to cause stress cracks like this. Note that the cracks are around the beefed up areas the windows are fitted into.
Inside the Glass will likely be some other filler material to increase the thickness. They don't tend to just add extra layers of glass when doing this. Often it is either plywood or foam. Then glassed over. The result is that there is a point where the expansion and contraction is different and it stresses the Gelcoat. Gelcoat is actualy very brittle.
If the cracks are right through the glass itself, this will be due to cloth being too light. This is the reason why when glassing over ply, you should use a minimum of 600oz glass cloth. Anything lighter can split due to expansion of the Ply underneath just from the heat of the day. Even in situations when Epoxy has been used. It will split the coth clean open if not heavy enough.

Moisture is another one that can cause a similar thing. Moisture will cause the Ply to swell a little. Or heat from very hot dry sunny days may even cause it to shrink. It only takes the slightest little pinhole or whatever for the moisture to get in or out and cause the ply to change shape enough to put stress on the Gelcoat/Glass cloth. Especially as the Gelcoat ages and becomes more brittle.
And one last scenario on that is when the windows were removed, did that allow exposure of whatever material is beneath. Just enough to change the moisture content.
It is even possible that the work carried out may have flexed the window areas a little, causing the cracks to appear. But only due to the stress already being there and they would have appeared eventually anyway. It is no real fault of the Worker as such. Normally you should be able to pound on a hull and not have cracks appear.
The repair should also be fairly easy to carry out. Just as has been done in the picture. A light grind back, fill, a layer of glass if the crack is through the glass, due to as I described above and then repaint. I suggest repaint with a two pot Urathane. Polyurathanes are flexible and will move with the substrates and will never crack on you.

The only real way of not ever having such happening, is to layer up glass till the required thickness is achieved. But that is not something a designer/builder of such a speed machine would want. They want to reduce weight as much as they can. Hence the lighter fill materials they tend to use. Plus they often want something in there to screw into as well. Ply is good for that.

I hope that helps, even if it does mean you might have to wear the cost. At least it may give you greater confidence in the yard.

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On 28/02/2022 at 11:24 AM, Island Time said:

Most boats now use only adhesive for window fasteners, including offshore boats. Modern adhesives can be stronger than the laminates they attach to. But your boat, your call.

Yes ... but the 'modern' adhesives that were used January 2018 failed... I am very glad we had the bolts thru the polycarbonate. 

And while on the subject of thru bolting the glass... The windows have used thru-bolts for 22 years and the polycarbonate has never cracked, so the point stressing issue seems moot to me.

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On 28/02/2022 at 4:28 PM, harrytom said:

Is it possible with the heat we have been having of late,shrunk the bog or no glass in frame the heat has caused a bit of warping??

The windows have seen far more heat in the past. Besides, the boat is inside a paint shed and there is no direct insolation. 

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18 hours ago, wheels said:

I have seen this kind of thing before.
Firstly, it is not structural.
Nor is it the fault of the Yard/person working on the windows. They are correct that it is a build issue, but in saying that, it is not due to poor build quality as such.
Basically what is happening is the Gelcoat has cracked at a point were two substrates have an ever so slight different rate of expansion when heating/cooling. Or one part flexing not quite so much as the other due to Hull movement. We are talking only fractional amounts, but enough to cause stress cracks like this. Note that the cracks are around the beefed up areas the windows are fitted into.
Inside the Glass will likely be some other filler material to increase the thickness. They don't tend to just add extra layers of glass when doing this. Often it is either plywood or foam. Then glassed over. The result is that there is a point where the expansion and contraction is different and it stresses the Gelcoat. Gelcoat is actualy very brittle.
If the cracks are right through the glass itself, this will be due to cloth being too light. This is the reason why when glassing over ply, you should use a minimum of 600oz glass cloth. Anything lighter can split due to expansion of the Ply underneath just from the heat of the day. Even in situations when Epoxy has been used. It will split the coth clean open if not heavy enough.

Moisture is another one that can cause a similar thing. Moisture will cause the Ply to swell a little. Or heat from very hot dry sunny days may even cause it to shrink. It only takes the slightest little pinhole or whatever for the moisture to get in or out and cause the ply to change shape enough to put stress on the Gelcoat/Glass cloth. Especially as the Gelcoat ages and becomes more brittle.
And one last scenario on that is when the windows were removed, did that allow exposure of whatever material is beneath. Just enough to change the moisture content.
It is even possible that the work carried out may have flexed the window areas a little, causing the cracks to appear. But only due to the stress already being there and they would have appeared eventually anyway. It is no real fault of the Worker as such. Normally you should be able to pound on a hull and not have cracks appear.
The repair should also be fairly easy to carry out. Just as has been done in the picture. A light grind back, fill, a layer of glass if the crack is through the glass, due to as I described above and then repaint. I suggest repaint with a two pot Urathane. Polyurathanes are flexible and will move with the substrates and will never crack on you.

The only real way of not ever having such happening, is to layer up glass till the required thickness is achieved. But that is not something a designer/builder of such a speed machine would want. They want to reduce weight as much as they can. Hence the lighter fill materials they tend to use. Plus they often want something in there to screw into as well. Ply is good for that.

I hope that helps, even if it does mean you might have to wear the cost. At least it may give you greater confidence in the yard.

Let's see...

There is No Gel Coat on this hull, it's all epoxy and polyeurathane paint systems.

There is fiberglass boat cloth under the 'glass'

I postulate that if your theory were correct then we would have seen some indication of cracks appearing more gradually over time in the last few years... (Not over the course of a 1/2 hour while caulk was being scraped)

 

 

 

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3 hours ago, 2flit said:

Not over the course of a 1/2 hour while caulk was being scraped

Sounds like flexing, if so it's probably unavoidable.

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3 hours ago, 2flit said:

Let's see...

There is No Gel Coat on this hull, it's all epoxy and polyeurathane paint systems.

There is fiberglass boat cloth under the 'glass'

I postulate that if your theory were correct then we would have seen some indication of cracks appearing more gradually over time in the last few years... (Not over the course of a 1/2 hour while caulk was being scraped)

 

 

 

 

Let me put it another way. There is absolutely no way someone could do this scrapping the sealant away from the substrate.
Does the crack run deep enough to go right through the Glass cloth, or is it just the surface Paint or whatever it is?
The places the cracks show are most certainly around the edges of the heavy build up areas. This certainly suggests a difference in movement of two differing components below.
Are you absolutely sure the interior is Polyurathane?? It certainly looks more like Gelcoat or Flowcoat to me.
I did not realise the Boat was 22yrs old. That age, it is a wonder you do not have far more cracking. These Hulls are subject to lots of stress and movement. I would suggest the cracks were there before hand and you likely have no noticed.

Are you replacing the windows?? Do not use Polycarbonate. Use Acrylic if you want to remain with light weight. Polycarbonate loses 50% of it's strength per year. Glass is stronger, lasts forever and Sealants adhere far better, but much heavier of course. Acrylics and Polycarbonates require very specialised adhesives to ensure long term fix to the substrate.

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I have to disagree wheels, and there is no gelcoat on a boat like this, it could easily happen due to flexing and the stresses  of removal . And Polycarbonate Lexan is very strong and properly bonded is fine.

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9 hours ago, Psyche said:

Sounds like flexing, if so it's probably unavoidable.

Except the caulk AND the windows were removed four years ago without incident?

This time it was only the groove of caulk around the window margins to allow for painting, the windows were not ripped out when this happened

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9 hours ago, wheels said:

 

Let me put it another way. There is absolutely no way someone could do this scrapping the sealant away from the substrate.
Does the crack run deep enough to go right through the Glass cloth, or is it just the surface Paint or whatever it is?
The places the cracks show are most certainly around the edges of the heavy build up areas. This certainly suggests a difference in movement of two differing components below.
Are you absolutely sure the interior is Polyurathane?? It certainly looks more like Gelcoat or Flowcoat to me.
I did not realise the Boat was 22yrs old. That age, it is a wonder you do not have far more cracking. These Hulls are subject to lots of stress and movement. I would suggest the cracks were there before hand and you likely have no noticed.

Are you replacing the windows?? Do not use Polycarbonate. Use Acrylic if you want to remain with light weight. Polycarbonate loses 50% of it's strength per year. Glass is stronger, lasts forever and Sealants adhere far better, but much heavier of course. Acrylics and Polycarbonates require very specialised adhesives to ensure long term fix to the substrate.

Hi Wheels,

The crack does not go thru the inner skin.

The lead yard guy insists that he would have seen these cracks just several days beforehand because they were closely inspecting the area about 5 cm away because there worker had located the heater vent fairing in the wrong location and were attempting to figure out how to resolve this.  There were three other folks closely inspecting the area without noticing them. They were not there days beforehand.... It is certainly very odd.

Yes I am 100% sure the interior is two-pack poly. I have the receipts for the paint purchased from Fisheries Supply in Seattle.

As too being surprised that there aren't cracks everywhere....Yep... Ian Farrier said it was the "best built" of all the F36/39 hulls he had seen. Ian was paid to supervise the construction when he had an office in Bellingham.  He advised  me many times before he passed away. There is absolutely no cracking anywhere else in this boat (inside of outside) This is true even in highly stressed areas around the 'water stay/strut chain plates and akas. The build was paid for by a fortune 500 CEO/owner. As an example 2,000 man-hours were on the job sheet for just fairing/sanding the interior alone.

We have already chosen Polycarbonate , so that train has left the station.

 

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9 hours ago, Psyche said:

Was the sealant removed with a vibrating tool?

Yes, At the very beginning the sealant was removed with a Fein tool, the blade used was for removing deck caulk a(this has a small razor sharpened hook at its end).... but  everyone says the cracks did not show up until four months later  -  after the grooved out area was being prepped for the new sealant.

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I just do not see how doing anything.....Vibration, hammering, levering.... anything is going to do that kind of damage. It really does not make sense.

So jut to be clear, the Glass below is OK, this is just the Paint layer only? Does the paint want to peel off the glass?? It must be a very brittle Two pot Urathane to crack like that. Gelcoat is brittle, but still takes a lot to cack it. Urathane would need far more flex to crack it. I find it hard to believe anyone could apply enough movement to make it crack that way. The only time I have ever seen long linear cracks like that has been when the Glass Cloth itself has split.

Waikiore, I stand corrected by your Lexan comment. I was told by a so called expert UV degrades Lexan. But I could find nothing on Line to prove my assumption. In fact I found that many Polycarbonate products today have UV stabalizers and even surface coatings to reduce scratching.

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I have seen hairline cracks like that in similar positions near windows on glass boats, Ive just put it down to flex over time eventually cracking the bog. Its easy to fall in the trap of coincidence but correlation does not mean causation. These cracks could have been there unnoticed for some time and the work just gave the final nudge for them to surface.  All panels flex can especially around empty windows frames, what we know is that the laminate is good so structurally everything is ok, its just the fairing that failed. Also the fact that only those rear stb frames (??) are faulty would tend to indicate that the particular area is vulnerable to movement or an issue with the original build otherwise one would expect similar faults on the other lights in a random pattern. The other thing you mentioned is the  high quality work of the yard in general, there has to be some trust in their opinion of what the fault is. Overall its a minor repair unless you are expecting an entire interior repaint, that would get complicated.

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