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Old 25-02-2016, 17:12   #1036
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Re: Oyster Problems?

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Originally Posted by Polux View Post
Hull deck joints are traditionally bonded, some use screws too. Old deck joining (before superior bonding agents era) were made other way, probably with worse results.

It seems you agree that the problem are not bonding agents, that can have a superior performance, but the way they are used. It seems to me that Bavaria is using them in a proper way, using screws to be sure the bonding is tight.

I know adhesives are useful in structural applications. But use of adhesives requires significant experience and lots of cycle loading and destructive testing. The failure modes are not similar to bolted joints. Sometimes a failure is unrelated to the adhesive itself but the surface it is bonded with fails first.

I have no idea if Bavaria's hull/deck joints survived all the testing and real survival storms. What I observed was a pretty narrow (few cm) glue face and some screws that are not a backup to the adhesive. The adhesive or the laminates bonded by the adhesive are the only thing keeping the ocean on the outside. It would seem a simple belt and suspenders approach to through bolt with backing plates. That would be a "blue water" design feature. But it would add cost which is the only reason I can think why they don't do it.

In fairness, there were other more troubling design/build features in that video than the hull deck joint.
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Old 26-02-2016, 00:32   #1037
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Re: Oyster Problems?

If the Plexus is so good stuff why not 3D print the whole boat with it. One robot to install the hardware on the uncured bog. No screws and no employees
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Old 26-02-2016, 02:06   #1038
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Re: Oyster Problems?

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Yes you can design a structure that doesn't need bulkheads but the Bavaria is not one of them so what's your point? Personally I don't have a problem with glued joints as long as they are designed and built well. Who was the yacht builder that built your last boat?
So you know that Bavarias are designed to need the deck bulkhead joint and are not stiff enough because it is not tabbed?

My earlier boat was made by a very small Finnish-Estonian builder that was bancrupted more than 10 years ago. It was a modern design with many rather new design features for a C/R boat designed by a young designer. It also had a steel grid, which was only glued to the hull (+ keel bolts).
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Old 26-02-2016, 02:22   #1039
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Re: Oyster Problems?

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If the Plexus is so good stuff why not 3D print the whole boat with it. One robot to install the hardware on the uncured bog. No screws and no employees
You could equally well ask if bolts are show good, why not make the whole boat out of bolts or at least bolt everything (grid, bulkheads, interior, etc.) to the hull. Bolts are good for something that may be necessary to take apart later.

Why it is so hard to accept glues in boat building while there is no problem accepting them in cars and aircarafts? Glassfiber is made out of "glue" and fiber anyway and separate layers of glassfiber are only glued to each other so it is more natural to glue them compared to aluminium and steel.

Adhesives in the automotive industry | Wolf Group MastersClub
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Old 26-02-2016, 03:03   #1040
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Re: Oyster Problems?

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Why it is so hard to accept glues in boat building while there is no problem accepting them in cars and aircarafts? Glassfiber is made out of "glue" and fiber anyway and separate layers of glassfiber are only glued to each other so it is more natural to glue them compared to aluminium and steel.
Just the fact glue joint has no fibers so the entire bond is depending of the glue. Car's service life is short and the forces on glued joints are much weaker nor a fail in one present any major life threadening danger. Airplanes are inspected in regular intervals and serviced following strict protocol.
Don't try fool yourself about separate layers glued together. It's different engineering from a deck to hull joint or full liner to hull, and as you know there are other common problems as delamination which proves the point of poor bonding issues of a"glue"
Remind you I didn't say it' inevitable a glued joint to fail but I'd be a bit sceptic untill time tells how they cope with time and cyclic loading. And I don't think mechanical fasteners any more reliable but they are easier to check and change if in doupt.
Personally I don't trust any structural joint without glassing it over with adequately scheduled lamination.

BR Teddy
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Old 26-02-2016, 03:16   #1041
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Re: Oyster Problems?

The loads in a car are a diferent animal compared to a boat subject to a worst environment.... I don't see any posible comparison..
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Old 26-02-2016, 03:18   #1042
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Re: Oyster Problems?

Deck hull joint is quite easy to inspect. Just go sailing in some waves. If water comes in, you have a leak in that joint and thus a local failure of the joint. Or you can check the air tightness of the joint whenever you like. I found the leak location in my earlier boat by blowing with my mouth. There was glue missing for a few mm.

Has someone heard of a failure of the glued deck hull joint? I know several leaking bolted joints.
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Old 26-02-2016, 03:24   #1043
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Re: Oyster Problems?

Well , someone know the repair procedure for a Plexus hull to deck joint??
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Old 26-02-2016, 04:43   #1044
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Re: Oyster Problems?

I've read a fair bit (admittedly not all) but haven't seen a reference to what is a common problem, and a construction trap that is all too easy to fall into.

It doesn't just apply to boats either.

You can have what can possibly be called a failure due to a catastrophic cascade effect of slightly unsuitable tolerances.

Penny pinching is one of the main causes of this, along with inadequate oversight and supervision (the concept of competent work supervision has itself largely disappeared over the past 40 years).

A system is built with a lot of components with different tolerances. When specifications allow penny pinching to focus on the minus end of the +/- allowable, you can end up with everything being a) in tolerance individually, but b) badly out of tolerance as a whole.

I am not saying this is what has happened with Oyster, but I can say that far too much of this has been going on, for way too long in pretty much every field, and it is a problem that is not getting any better.

Now you add in penny pinching with individual component suppliers, where the component is also made up of several or many items with +/- tolerances . . . .

Often a manufacturer is blamed for inadequate product. But they do supply according to price. If you need a 20p item to reliably do the job, but are only prepared to pay 10p.

You get a 10p item.

As an ex importer/exporter, I have seen this process in action in real life, way too often.

It's how my father ended up buying a blender off Tesco's, that wasn't particularly cheap, but when he used it on his kitchen worktop, it burst into flames. A CE label isn't worth the letters that are printed on it.

When he took it back to Tesco's, to the branch he bought it from, the large pile of blenders they had for sale there previously, had disappeared, and they denied point blank that they had ever had any in the store to sell him (the receipt was worthless, because all the printing had faded to nothing within a few weeks of buying the thing).

I tried to get him to take it to Trading Standards, but he thought that would be a waste of time, because it was 'Tesco's'.

Now if you think this sort of corruption isn't afflicting boat building (or pretty much everything surrounding chronically overpriced products with the boating industry, among so many others), I have some great beachfront property in the Sahara to sell you.

How is it that a significant amount of so called marine grade calibrated chain, for instance, isn't? How come a significant amount of so called 1x19 stainless steel rigging wire, isn't? Anchors falling over and breaking in half isn't happening, is it? Etc. Etc.

If you keep playing their game, they will cheerfully keep ripping you off with substandard chronically overpriced gear.

The only way you win, is by refusing to play, and it is how complete industries end up committing financial suicide. The good end up being taken down by the bad, and with the bad.
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Old 26-02-2016, 07:10   #1045
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Re: Oyster Problems?

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Originally Posted by jmaja View Post
Deck hull joint is quite easy to inspect. Just go sailing in some waves. If water comes in, you have a leak in that joint and thus a local failure of the joint. Or you can check the air tightness of the joint whenever you like. I found the leak location in my earlier boat by blowing with my mouth. There was glue missing for a few mm.

Has someone heard of a failure of the glued deck hull joint? I know several leaking bolted joints.
Good luck with that in a boat with a liner. Boat Maintenance and Repairs: Dealing With Leaks
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Old 26-02-2016, 07:36   #1046
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Re: Oyster Problems?

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Well , someone know the repair procedure for a Plexus hull to deck joint??
I don't know. What is it for the bulted joint? I guess both would require opening the seam in order to be able to clean surfaces and put new glue or sealant in. Since deck is glued or tabbed to bulkheads etc. it will be very laborous to rise the deck more than a few mm. Maybe it is enough for grinding the old glue/sealant away.

One option is to glass over from the outside in both cases.
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Old 26-02-2016, 07:43   #1047
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Re: Oyster Problems?

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Good luck with that in a boat with a liner. Boat Maintenance and Repairs: Dealing With Leaks
That boat had a liner. No problems doing the inspection and adding some Sikaflex from the outside. After that the boat was completely dry inside. As is my current boat with glued deck hull joint. Never a drop of water in the bilge unless I drop a wet spinnaker in.
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Old 26-02-2016, 08:41   #1048
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Re: Oyster Problems?

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Just the fact glue joint has no fibers so the entire bond is depending of the glue. Car's service life is short and the forces on glued joints are much weaker nor a fail in one present any major life threadening danger. ....
Personally I don't trust any structural joint without glassing it over with adequately scheduled lamination.
BR Teddy
The stress is not lighter or weaker and will represent a threat to life if they fail.

If a car chassis broke or become lose at speed the results can be catastrophic and there are cars with bonded chassis and most of then are high performance cars that are subjected to more stress than normal cars and much more than a hull to deck joint. Some words about that from the car industry sector:

Using adhesives for body manufacture – adhesives which can be formulated for aluminium, steel and composite bonding applications on unprepared surfaces – is a trend that’s on the rise with automakers,”....Take weight saving, for instance:by introducing crash-resistant adhesives between the seams of core structure panels, the thickness of the steel used for the panels can be reduced,....Because the adhesive allows stress to be more efficiently transferred between panels, it helps boost body stiffness while maintaining crash performance...
Forming a bond to replace spot welding - Automotive Manufacturing Solutions

Regarding Bonded chassis on cars they are used by high end brands like Aston Martin and many others:

"The 2002 Aston Martin V12 Vanquish is one of the most technically advanced cars on the road. From its extruded aluminum space-frame to its carbon fiber transmission tunnel and energy absorbing crash structures, the entire vehicle is adhesively bonded together. "
http://www.speautomotive.com/SPEA_CD...03/pdf/b01.pdf

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Old 26-02-2016, 08:53   #1049
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Re: Oyster Problems?

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I don't know. What is it for the bulted joint? I guess both would require opening the seam in order to be able to clean surfaces and put new glue or sealant in. Since deck is glued or tabbed to bulkheads etc. it will be very laborous to rise the deck more than a few mm. Maybe it is enough for grinding the old glue/sealant away.

One option is to glass over from the outside in both cases.
Exactly , with a sealant joint we can know for sure how to fix it, now if you have a hard cracked bead of plexus at the joint i guess is something to consider if you attempt to stop a leak , how? no idea but my mind is thinking in a serious grinder carnage at the deck hull joint...
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Old 26-02-2016, 08:54   #1050
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Re: Oyster Problems?

I can just imagine what it might be like to repair one of these hi technology cars after an accident. Personally I have no problem with glues but if given a choice when choosing an offshore boat between something like a HR that has the hull to deck joint completely glassed to one that has been glued, I'll take the completely glassed one if for no other reason than the fact that they have stood the test of time in all weather conditions.
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