Cracked hull windows. Any advice?

[Deleted User YDKXO]

Mike, have you pulled the interior trim off round the windows to see if there's some component that's touching the edge glass at the location of the root of the crack? And to what degree has the apparently-degraded bonding failed - is there a gap or unadhered patch where you can slide some fine tool through?

No I haven't Jimmy. The window is sealed with Sikaflex both sides and on the inside there is a trim piece which is either sealed or glued in place and which I could make a real mess removing. It would be easier to remove the Sikaflex from the outside and poke around but I can't do that until the boat is lifted in March

 

[MapisM]

they responded by saying they'd never seen anything like it before

M, today I saw a F630 moored, and it popped to my mind that there might be some around with the same (or very similar) problem - possibly even unnoticed from the owner.
Now, in this particular occasion I didn't stand a chance to go near her hull and check the glasses, because she was moored with the usual Med style, and there weren't any marina folks around with RIBs to try and ask them.
But if by chance in PV, which is a big marina, there is a sistership somewhere, it might be worth going around with the tender and a camera...
Just a thought!

 

[jfm]

Oddly there isn't another 630 that I can think of in Port Vauban. There's one in Monaco (Fortvielle) with a retro painted blue hull and a custom made higher flybridge windscreen, and there's one in Golfe Juan on the last jetty as you walk around clockwise far side, just before you start the line of 50m berths, called "Bogey". Both are moored "med style" so it's hard to see anything

There are plenty of 731 and 750 in PV, which I think have the same window but not 100% sure on that

 

[petem]

"Let's put everyone else's premium up to pay for this dubious claim"

If it's accidental damage like a bad lift then Mike is entitled to claim. If is a latent defect he isn't.

But, as per my email earlier, I would suggest an optional Glass Replacement insurance bolt on.

 

[Deleted User YDKXO]

Oddly there isn't another 630 that I can think of in Port Vauban. There's one in Monaco (Fortvielle) with a retro painted blue hull and a custom made higher flybridge windscreen,

Yup for one of Ferretti's best selling models I haven't seen many about in the Med. I have seen the painted one anchored in Villefranche. Its hideous

 

[JumbleDuck]

So far no comment on the type of crack or how serious it actually is? As I say the crack does seem to be internal ...

I'd be very surprised if that's the case. I think it is far more likely that it is a crack in one of the sheets of glass which is now being pushed together again so that you can see the internal refection of the broken surfaces but can't feel anything on the surface. As to how it happened ... you can make a crack like this three ways: pull the edges apart in the plane of the material (2) push one edge along the other in the plane of the material or (3) pull the edges apart perpendicular to the plane of the material - ie one "in" and one "out".

In this case I think (2) is implausible and (1) unlikely, so I'll put by money on (3), caused by flexing of the hull and consequent deviation from its usual in=out curve along the bottom of the window. In which case, eithout strengthening of the hull, a replacement window may go the same way.

Meantime, it might be worth putting a stress-relieving hole in line with the end of the crack but a bit (4m?) further in. The stress (actually the stress intensity factor) around the tip of a crack is inversely proportional to the tip radius, which for a linear crack is tiny: hitting even a 2mm hole can stop a crack dead.

One of the reasons that GRP is so tough, by the way, is that cracks in the resin are stopped in just this way by the cylindrical holes occupied by the glass fibres.

 

[petem]

I'd be very surprised if that's the case. I think it is far more likely that it is a crack in one of the sheets of glass which is now being pushed together again so that you can see the internal refection of the broken surfaces but can't feel anything on the surface. As to how it happened ... you can make a crack like this three ways: pull the edges apart in the plane of the material (2) push one edge along the other in the plane of the material or (3) pull the edges apart perpendicular to the plane of the material - ie one "in" and one "out".

In this case I think (2) is implausible and (1) unlikely, so I'll put by money on (3), caused by flexing of the hull and consequent deviation from its usual in=out curve along the bottom of the window. In which case, eithout strengthening of the hull, a replacement window may go the same way.

Meantime, it might be worth putting a stress-relieving hole in line with the end of the crack but a bit (4m?) further in. The stress (actually the stress intensity factor) around the tip of a crack is inversely proportional to the tip radius, which for a linear crack is tiny: hitting even a 2mm hole can stop a crack dead.

One of the reasons that GRP is so tough, by the way, is that cracks in the resin are stopped in just this way by the cylindrical holes occupied by the glass fibres.

Sounds plausible, without wishing to be rude, how do you know this? Do you have professional experience in this field?

 

[JumbleDuck]

Sounds plausible, without wishing to be rude, how do you know this? Do you have professional experience in this field?

Twenty years of teaching fracture mechanics to undergraduate engineers.

 

[jfm]

JD, I think I'd place a side bet on mode 1 too. If the polyurethane glue is too stiff, either due to UV hardening or being applied too thinly, then any fore-aft stretch in the GRP flange that the glass is glued to (due to sagging in a hoist, or on stands, on waves, or something else that induces a sag-bend in the hull) will tend to induce mode 1 along the bottom edge of the glass.

In an ideal world, when changing the glass, I think I would want to laminate some epoxy/glass right around this flange to stiffen the flange. Access to do that lay up wont be at all easy or even possible of course, and it might be easier to use latest and greatest glue (like saba 760xl) and apply it 50% thicker than ferretti did (by using thicker foam stand off pads)

 

[JumbleDuck]

JD, I think I'd place a side bet on mode 1 too. If the polyurethane glue is too stiff, either due to UV hardening or being applied too thinly, then any fore-aft stretch in the GRP flange that the glass is glued to (due to sagging in a hoist, or on stands, on waves, or something else that induces a sag-bend in the hull) will tend to induce mode 1 along the bottom edge of the glass.

Fair point. Bet accepted.

In an ideal world, when changing the glass, I think I would want to laminate some epoxy/glass right around this flange to stiffen the flange. Access to do that lay up wont be at all easy or even possible of course, and it might be easier to use latest and greatest glue (like saba 760xl) and apply it 50% thicker than ferretti did (by using thicker foam stand off pads)

Yes, adding some additional flexibility to the joint seems like a Good Idea.

 

[MapisM]

I think it is far more likely that it is a crack in one of the sheets of glass which is now being pushed together again so that you can see the internal refection of the broken surfaces but can't feel anything on the surface.

I fully understand what you mean, but I would have thought that by swiping the tip of a nail very carefully across the crack, you should always feel at least a veeery tiny step.
In a couple of occasions, with cracked car windshields, I did experience such feeling.
And in one of those cases, the crack was very short, developing from one corner, and only on one side of the glass (I suppose due to "mode 3" as per your classification). But still perceivable, with some attention.
In Deleted User boat, I also tried to sense the crack on both surfaces, but it really felt smooth as silk...

PS: anyhow, regardless of the reasons and of where the crack exactly is, the stress-relieving hole idea sounds very clever.
I think I'd rather try that and see what happens, before going for the full monty job.

 

[Portofino]

Not so ,sure on the UV hardening theory , if so only the surface ? The bond may be protected or just does not .It may time harden degrade instead uniformally .Hope V what ever is an improvement on the original ?
Any how agree it acts as a buffer , as an interim easy fix agree thicken it up .

How ever my Professional experiance 30 y micro engineering in albeit a more hostile enviroment ,thickening up the "bond" rarely works ,as the failure is due to the flexing of the thing itself (in this case glass laminate ) .So the fix is to eliminate the flex .

The only answer that works in repeated failed # cases is CHANGE the material .
I mean use a different window material ,or thicker dimension if the same material .-to increase stiffness reduce flex .

Mearley using exactley the same part with thicker bond in my book will buy time sure .But it's a tempory fix and the "customer " needs to know .

I think the frame /moulding is now over flexing more then it did when new .Not sure exactley why - but it does not matter now -it is !

A permanent fix is different newer -part -glass laminate - ,pref not the same material or thicker if the same .

So agian Mike I would ask around and get replacement "glass" made up
Good news is its bilateral so will look ok to change ,when the new parts are fitted .

The two out of 7 sections on the screen on my Itama are being replaced .
Reason slight wrong shade -it annoys me in certain light -not # .
Ferretti have washed there hands and can not /will not access the parts ---so my Yard are having them made .
Although in this case copying the thickness to match the others ,just a shade change .

You could have what ever thickness made up ---- not the SAME -along with the thicker bond theory should provide a premantantly fix .Assuming the same forces will be applies in the sagging .

 

[JumbleDuck]

PS: anyhow, regardless of the reasons and of where the crack exactly is, the stress-relieving hole idea sounds very clever.
I think I'd rather try that and see what happens, before going for the full monty job.

It has a very high chance of stopping things getting any worse. There is often an invisible thin crack extending beyond the end of the visible one, which is which you put the hole slightly further on than you can see

 

[petem]

I can't recall if this was suggested before, but can you ask the original glass manufacturer what they think? Assuming Ferretti or someone can tell you who they were?

 

[Bandit]

The Glass is toughened, the glass can only be worked before it is toughened.

If you try and drill toughened glass it will shatter.

I think you will find that either the movement of the boat probably when at sea has either compressed or bottomed out the silicone resin and a point loading from GRP to glass has caused the crack or there is some debris in the silicone such as a stone or a hard plastic packer was used to stop the glass slipping down in to the sealant before it cured. The glass window must weigh in excess of 100kg and that would just sink in the sealant when fitted vertically. The plastic packer if not removed would provide a hard point a point load.

 

[JumbleDuck]

The Glass is toughened, the glass can only be worked before it is toughened.

If you try and drill toughened glass it will shatter.

Are you sure that it's toughened?

It seems unlikely that a stable crack of the size we've seen could exist in toughened glass, although it would be happy in laminated, which is what the OP says the window is. It is possible to get glass which is both toughened and laminated, but since the toughening has to be done first, making curved panels would be tricky.

 

[petem]

Are you sure that it's toughened?

It seems unlikely that a stable crack of the size we've seen could exist in toughened glass, although it would be happy in laminated, which is what the OP says the window is. It is possible to get glass which is both toughened and laminated, but since the toughening has to be done first, making curved panels would be tricky.

I believe the glass is flat.

 

[rafiki_]

Are you sure that it's toughened?

It seems unlikely that a stable crack of the size we've seen could exist in toughened glass, although it would be happy in laminated, which is what the OP says the window is. It is possible to get glass which is both toughened and laminated, but since the toughening has to be done first, making curved panels would be tricky.

I'm reasonably confident that it is a laminate glass, not merely toughened. There will be standards for this use of glass. I don't know what it is, but the CE approvers, probably RINA, will have checked and approved.

 

[JumbleDuck]

I'm reasonably confident that it is a laminate glass, not merely toughened. There will be standards for this use of glass. I don't know what it is, but the CE approvers, probably RINA, will have checked and approved.

The question then is whether it's toughened as well as laminated. From the crack, I strongly suspect not, but it's definitely something to confirm before drilling holes in it.

 

[jrudge]

Stop drilling is use a lot in planes ( far too much to be honest!).

Never seen it done in glass, but it can be drilled as long as not toughened so should like a good idea.

A stop drill and a local glass repair specialist to fill in the hole you just made and the problem might just go away for not much £. You certainly cant be much worse off unless it shatters.