Rudder Failures

[smackdaddy]

Originally Posted by minaret

Get some plexus and apply it to a waxed surface, then peel it off for a thin sheet of straight plexus. Then do the same with a typical bulkhead tab layup. Then bend yer samples till they break. The plexus breaks easily by hand after bending not very far. The glass can bend full circle with no fractures. Just try it.

This is your documentation?

What is the typical tab layup made of exactly? And why are these boat-builders in these reports saying the opposite (see image)?

[neilpride]

Then i dont undestand why the more expensive brands are still fg tabbing the internal components? even grid liners in some cases, they can save a ton of cash doing with plexus no?

[smackdaddy]

Originally Posted by neilpride

Then i dont undestand why the more expensive brands are still fg tabbing the internal components? even grid liners in some cases, they can save a ton of cash doing with plexus no?

Again, I don't know about cost. I've not really made that argument.

I'm just looking at the issue of strength in these reports since that is what started this conversation about Plexus in this thread (i.e. - that glass tabbing is stronger/superior).

[Polux]

Originally Posted by minaret

You thought wrong. Bonding with plexus is never as good as a laminate-never. Its strictly a money saver for the builder. Also, it is not possible to glass in a hull liner. ..

Never?

You know, there are technicians and scientists that study materials with proper method and adequate experiences in controlled environments and that is not their opinion.
I am not saying with this this that bonded is always the best solution for all cases neither that is always corrected used, just saying what is common knowledge after extensive testing: In some cases bonding is a better solution than laminate and it is not only regarding the price.

[neilpride]

Originally Posted by smackdaddy

Again, I don't know about cost. I've not really made that argument.

I'm just looking at the issue of strength in these reports since that is what started this conversation about Plexus in this thread (i.e. - that glass tabbing is stronger/superior).

I understand Smack , but again i ask the question if someone can answer , its a good point, if Plexus is widely used in the low spectrum of the production list why the most expensive brands Fiberglass the vital components like bulkheads, partitions, grids etc...why a VOR 65 have the CF bulkheads glassed to the hull, or why a HR do the same??? when they can choose plexus, cheaper and stronger? no?

And yes is cheaper no matter what, Tabing bulkheads with cloth mean the yard need to drop crews in the bulkhead process with batchs of resin and cloth and start to laminate by hand , in the other side drop a bulkhead in the liner slot , bed a line of plexus and make a fillet is faster and cheaper. or not?

[transmitterdan]

Polux,

The drawing you show is not what we see in the photos of actual bulkheads. And even in the drawing you show the amount of stress is only one part. The strength of the layup has to be considered. The problem is not as simple as the glossy brochure writers want to make it.

[smackdaddy]

Originally Posted by neilpride

I understand Smack , but again i ask the question if someone can answer , its a good point, if Plexus is widely used in the low spectrum of the production list why the most expensive brands Fiberglass the vital components like bulkheads, partitions, grids etc...why a VOR 65 have the CF bulkheads glassed to the hull, or why a HR do the same??? when they can choose plexus, cheaper and stronger? no?

And yes is cheaper no matter what, Tabing bulkheads with cloth mean the yard need to drop crews in the bulkhead process with batchs of resin and cloth and start to laminate by hand , in the other side drop a bulkhead in the liner slot , bed a line of plexus and make a fillet is faster and cheaper. or not?

Isn't the VO65 carbon? If so, there is this statement from the same report:

All these adhesives have excellent adhesion to reinforced plastics such as glass-polyester, but for carbon-epoxy composites it is mandatory to use epoxy adhesives.

[neilpride]

Ok Smack forget the vor 65 , what about the rest?

[smackdaddy]

Originally Posted by transmitterdan

The drawing you show is not what we see in the photos of actual bulkheads. And even in the drawing you show the amount of stress is only one part. The strength of the layup has to be considered. The problem is not as simple as the glossy brochure writers want to make it.

I think we all get that. What we (or at least I'm) saying is that nor is it as simple as saying "glass tabbing is superior to Plexus"...or, more specifically to your earlier statement...

Fiberglass reinforcement over a large area is much better structurally than gluing two things together at a narrow strip...

Doesn't that depend on the forces being applied? Surely you don't mean it's always better for every condition? Again, not that simple as you point out above. Yet you present it as such.

This is not about the "glossy brochures". It's about facts. At some point, you have provide some.

There are plenty of other examples/drawings in that same report. Look through them and counter what you disagree with with other facts. Otherwise, it's just brochure talk.

[transmitterdan]

Yes, I mean it is always possible to do it better with fiberglass than with glue. It is possible to do it wrong with either glue or fiberglass. But comparing two things where one is done incorrectly is pointless.

In the drawing Polux showed they call it a stringer. No fiberglass structural stringer should
be built as they show it. So right away my BS meter is pegged. Stringers should be hat sections tabbed on both edges of the hat. A cantilever section like they show is not where the stresses will come. They come in the other plane. And for that I would much more trust fiberglass tabbing. Not that the glue will fail but that what it is glued to will fail first.

[transmitterdan]

Originally Posted by Polux

Never?

Yes, never.

In this picture if the fiberglass tabbing job on the right were on both sides of the "stringer" it would be several times stronger than the glued version. It would be even stronger if the "stringer" were a hat section and tabbed on both edges of the hat. But it would cost a lot more money to fabricate and tab it correctly which is the whole issue.

They are using the glue where there is no access for proper tabbing. Then they try to make some kind of weak argument the adhesive method is better than bad tabbing. Sorry, you have to find another comparison to convince me.

[Polux]

Originally Posted by transmitterdan

Yes, I mean it is always possible to do it better with fiberglass than with glue. It is possible to do it wrong with either glue or fiberglass. But comparing two things where one is done incorrectly is pointless. .

Are you an Engineer expert in materials and contemporary yacht building? What qualifies you to have a different opinion than those that are? Have you tested as they have tested?

[robert sailor]

I personally like the double spade set up and you can be sure Oyster will build it and the associated support systems properly. I think as you increase the beam and bring it further back you need a more powerful steering system.
As to the single handed racers...I have to say they have added quite a bit to the improvement in autopilots. Many of these boats were quite squirrely and the older pilots held them back but as tech'ys added more complex software they were able to really drive these new boats hard. We cruisers got some of that technology handed down to us in the form of vastly improved autopilots.

[minaret]

Originally Posted by Polux

Are you an Engineer expert in materials and contemporary yacht building? What qualifies you to have a different opinion than those that are? Have you tested as they have tested?

Perhaps because he's not being paid large sums of money for his opinion, unlike the fellows who made that "study", you might consider he is being more honest?

[smackdaddy]

Originally Posted by transmitterdan

Sorry, you have to find another comparison to convince me.

Unfortunately, that's not how it works. I don't really care about trying to convince you. I'm just doing some research on what some of you guys are claiming and I'm finding industry-level evidence out there that is contrary to those claims.

If you've got similar evidence to back up your claims you should post it. Otherwise, it's not very convincing to anyone. It's just a "trust me".

Again, I'm just a guy who is interested in boats and how they are put together and why. I'm no expert in any of these areas. But like most people, I ABSOLUTELY trust professional data over a "trust me" in a forum.