How Safe are Windows in the Hull

[awol]

How do people think aircraft and car windscreens are fitted?

Aircraft windows have mechanical fixings + are pressurised against their seals; car windscreens are glued but do not normally undergo forces that stress the glue line - video shows how to remove, I would suggest a fixing method not suitable for yachts!

 

[wombat88]

I had an old Vauxhall Cresta whose windscreen and rear window were stuck in place with a bead of black butyl. The windscreen always leaked and one day the back window fell out. I doubt it was much older than 15 years...

 

[dunedin]

The windows in our coachroof are on the outside with lots of sealant and lots of screws fixing them. For them to fail, it would probably be the glass plastic that fails and breaks. highly unlikely.

I suspect in this case the windows are fixed from the inside. No visible fixings on the outside so one would presume just glued in place to the inside of the hull and then covered on the inside with the trimmings of the interior.

As such that is form over function. Make them look nice but at the expense of a technically poor design, one good wave slamming against them could break the seal of the glue and the window can then just push in.

Whoever did the risk assessment of that design needs the sack.

Don’t know the specifics of the boat in question - but think most hull windows are put in from the outside into a flange moulded in the hull. So no possibility of being pushed in by a wave (but some risk of popping out if really badly fitted and glue fails?).

I think there are so many questions about the original rescue that it hardly sets any known precedent. And I think we are still at the case of ZERO documented sinkings due to hull window failure (unlike pilot house windows, propellor and rudder shafts, Orcas etc). Though I think it is right to wonder about long term repair costs for some of the huge custom windows fitted to most motor yachts and some sailing yachts, even if not a sinking risk.

 

[Rappey]

I had a lotus which had glass bonded to grp. At around 25yrs the bond failed and the windscreen moved around when driving, even on a smooth road.
It brought it home how much the glass formed a vital part of the cars rigidity. Had it rebonded.
Glass is easy to bond to. Some sealants are nearly impossible to get off glass. Polycarbonate/acrylic seems the opposite and difficult to find sealants that dont just peel off.

 

[Tranona]

Don’t know the specifics of the boat in question - but think most hull windows are put in from the outside into a flange moulded in the hull. So no possibility of being pushed in by a wave (but some risk of popping out if really badly fitted and glue fails?).

I think there are so many questions about the original rescue that it hardly sets any known precedent. And I think we are still at the case of ZERO documented sinkings due to hull window failure (unlike pilot house windows, propellor and rudder shafts, Orcas etc). Though I think it is right to wonder about long term repair costs for some of the huge custom windows fitted to most motor yachts and some sailing yachts, even if not a sinking risk.

Good summary.

As ever so much speculation about what might happen, but unsupported by any concrete evidence that these things DO actually happen. Add to that attempts to relate to other situations (cars, aircraft etc) that really have no specific direct relationship. On the other hand (until you mentioned it) little about windows always having been a problem on yachts when subject to extreme conditions. There must be tens of thousands of hull windows installed, many dating back over 20 years and there does not seem to be an epidemic of failures let alone founderings and deaths.

Rarely are designers/engineers/builders given credit for actually knowing what they are doing and assuring themselves that the products they offer are suitable for their intended use. There is an assumption by some here that anything "new" is suspect and that for example all bonded in windows are the same when in fact there are many variations in materials and techniques. Of course there will always be "failures" but equally they are almost always unique rather than systemic.

 

[Baggywrinkle]

Some vehicle bodies flex more than others, but vehicle bodies do flex and the car needs to be on a flat, level surface during the curing of the windscreen adhesive. If it isn't, as happened in Longbridge manufacturing plant when I worked there, then the window will be under permanent stress and will fracture. Some bright spark drove unfinished cars where the windscreen adhesive hadn't cured off the production line and parked them outside on kerbs so the car bodies were twisted.

The adhesive cured and when they were driven off the kerb, the windscreens cracked.

Body flex is normal, which is why racers fit extra bracing across the engine bay, across suspension turrets in the boot - and a good roll cage also helps control body flex. The adhesive is under stress, and the harder the car is driven, the more stress it is put under.

Flexing of the vehicle body is also the reason why small chips and cracks must be fixed immediately, with some insurers offering free repairs to avoid a full replacement. Cracks will propagate if the car experiences a shock due to a pothole, a kerb, or a if it is driven hard. Once a crack has got too big then instead of a repair, a new windscreen is needed.

Adhesives today also have a specified SDAT or Safe Drive Away Time ... this is to ensure the car is not driven until the adhesive has cured, and it is required due to the forces that can be exerted on windows by airbags.

 

[Sandy]

How do people think aircraft and car windscreens are fitted?

Spacecraft have a totally different set of problems.

 

[capnsensible]

There are shedloads of delivery skippers and crew who have taken gazillions of yachts with Hull portlights across oceans without a problem. Seems to me its a rare thing for one to pop. Just bad luck. Wouldn't over worry about it.

I never did......

 

[mjcoon]

Has anyone checked back on the YM "Crash Test" series to see if there's anything relevant? Or maybe, seen from now, the style of yacht used did not have hull windows...

 

[Laser310]

I agree with the comment above about rudders...

Many boats have sunk from losing a rudder - I'd be more worried about that.

with a failed window, tacking will do a lot to alleviate ingress while you work on a repair.

 

[noelex]

I agree with the comment above about rudders...

Many boats have sunk from losing a rudder - I'd be more worried about that.

I don’t know why more ocean going cruising boat manufacturers don’t place a coffer dam around the rudder. The top of the rudder is often close to waterline so it need not even be high.

 

[Chiara’s slave]

I doubt that many people worry about the strength of the windows, it's more the glue that holds them in. And not so much strength, but longevity.

 

[RivalRedwing]

There are shedloads of delivery skippers and crew who have taken gazillions of yachts with Hull portlights across oceans without a problem. Seems to me its a rare thing for one to pop. Just bad luck. Wouldn't over worry about it.

I never did......

but they would be mostly new(ish) boats... the time element / longevity of the glue is the issue that troubles me

 

[Tranona]

but they would be mostly new(ish) boats... the time element / longevity of the glue is the issue that troubles me

Judging by the number of threads on here about leaky windows and how to repair/replace future problems with bonded in windows are likely to be of similar order even if the nature of the failure and method of repair will be different.

 

[Fr J Hackett]

Judging by the number of threads on here about leaky windows and how to repair/replace future problems with bonded in windows are likely to be of similar order even if the nature of the failure and method of repair will be different.

But will it traditional windows had sealant developed perhaps 40 or 30 years ago the adhesives used to bond windows today are vastly different so there is no real relationship but time will tell.

 

[Tranona]

But will it traditional windows had sealant developed perhaps 40 or 30 years ago the adhesives used to bond windows today are vastly different so there is no real relationship but time will tell.

Thought that was what I said. There will be stories of failures and leaks but the failures will be different as will the repairs - just as they are now. there are all sorts of windows fitted to boats - different methods of construction, materials attachment etc already and seems none are trouble-free in the long run.

My personal view is that modern windows will give less trouble but likely more difficult to fix when they do. As for windows from the past it is often not the sealant that is the big problem but the rubbish design and poor materials used particularly on those screwed together monstrosities so popular in the days when MABs were being built. (guess who has those on his to do list).

 

[KevinV]

Easy enough to deal with aging bonding if it concerns you - have them redone if you buy such a boat, or at an interval that you deem acceptable.

I'm sure it'll end up being one of those things like standing rigging - we all have different perceptions of the risks, as do our insurers. I always find it interesting what insurers do/ don't get fussed about, because they deal in cold hard fact. They don't seem to mind hull windows, suggesting they don't often fail - if failures do become a regular thing they will certainly implement an inspection/ replacement regime (as per standing rigging)

As for the case in point, it's easy enough to imagine things being tensioned right up for a beat to windward, bashing into the waves, causing a bit of flex around a window frame.

 

[lustyd]

Glass is easy to bond to. Some sealants are nearly impossible to get off glass. Polycarbonate/acrylic seems the opposite and difficult to find sealants that dont just peel off.

Hull windows are largely glass. Most of the people saying perspex are I think guessing. Gone with the Wynns went to the Lewmar factory to see the process and got some pretty good explanations.

 

[lustyd]

Judging by the number of threads on here about leaky windows and how to repair/replace future problems with bonded in windows are likely to be of similar order even if the nature of the failure and method of repair will be different.

I think the repair issue isn't with the technology, it's with the owners. The boat I nearly bought recently had a bonded window (thankfully on the roof) that had been repaired with sanitary bathroom sealant. Whoever buys the boat will find out very quickly how useful bathroom sealant is in UV, probably within a couple of months I'd imagine.

 

[HenrikH]

Skagen race 2019

A surprising twist on the above event was that the yard response «the hull windows have to regularly re-glued»