Lagoon Cat smashed in Thailand

[barnakiel]

Cored hulls (here meaning cored below waterline) has been around for ages. I know boats built in the 60'ies that are still fine and taking up extended voyages.

Nothing wrong with any building technique as long as the design and the job are done to match the expected use of the boat.

b.

[monte]

Agreed b, I think the important thing to consider is nothing to do with skin thickness or layup, it's the overall engineered design which most of us aren't qualified to understand, especially so without complete plans and working drawings and engineering calculations. Supplying the layup schedule is like supplying the steel thickness for a bridge with no other data such as working load, span,web and bracing, etc. where a solid glass hull derives it's strength from its single layer of resin and layers of matt, a cored hull can have the same stiffness and strength with a much lighter layup, and consequently a cored hull with additional bracing from floors and bulkheads can also be constructed with a thinner lighter layup. The cored hull may be as stiff and structurally sound as the solid skin, but will be more vulnerable to impact loads like hitting the hard stuff.

[smj]

Originally Posted by monte

Agreed b, I think the important thing to consider is nothing to do with skin thickness or layup, it's the overall engineered design which most of us aren't qualified to understand, especially so without complete plans and working drawings and engineering calculations. Supplying the layup schedule is like supplying the steel thickness for a bridge with no other data such as working load, span,web and bracing, etc. where a solid glass hull derives it's strength from its single layer of resin and layers of matt, a cored hull can have the same stiffness and strength with a much lighter layup, and consequently a cored hull with additional bracing from floors and bulkheads can also be constructed with a thinner lighter layup. The cored hull may be as stiff and structurally sound as the solid skin, but will be more vulnerable to impact loads like hitting the hard stuff.

+1


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[D&D]

Originally Posted by monte

Agreed b, I think the important thing to consider is nothing to do with skin thickness or layup, it's the overall engineered design which most of us aren't qualified to understand, especially so without complete plans and working drawings and engineering calculations. Supplying the layup schedule is like supplying the steel thickness for a bridge with no other data such as working load, span,web and bracing, etc. where a solid glass hull derives it's strength from its single layer of resin and layers of matt, a cored hull can have the same stiffness and strength with a much lighter layup, and consequently a cored hull with additional bracing from floors and bulkheads can also be constructed with a thinner lighter layup. The cored hull may be as stiff and structurally sound as the solid skin, but will be more vulnerable to impact loads like hitting the hard stuff.

+2!

[barnakiel]

But we are just going circles in what modern day s.c. designers trained us to be: dumb consumers.

Think about it. We can have a sandwich composite with the outer layer as thick as a plain GRP hull. Then the sandwich structure gives us so many extra benefits: stiffness, strength, insulation.

Weight saving? What weight saving. (Note no question mark.) Lagoons and other such "weight saving technology" boats get regularly overloaded by their owners. Weight saving is very good if we want a light boat. And provided we can stay light. A modern cruiser is not "go light" minded person.

It is clear to anyone who understands the basics of physics (and I will disagree with the apparent necessity to have any extra amount of techie know-how to understand how laminates work and why) that if we keep weight constant we can get stronger (to area load, not to point load) laminate with a sandwich technology. But, in mass cruising context, contrary to what many may think, this "go lighter" trend with designers has nothing to do with "go stronger".

We are not racing. We are hardly ever sailing. The whole "lighter" thing is out there for the cruisers only to save on resins and other materials, making it possible to build cheaper boats. The same boats can be sold at a huge margin thanks to mortgage technology. ;-)

There are excellent quality, strong and safe sandwich boats around.

For those who are willing to pay the price.

b.

[barnakiel]

http://www.balticyachts.com/baltic-y...pdf?id=1150363

Good porn. Does not take a Ph.D. in physics to read and understand.

b.

[smj]

Originally Posted by barnakiel

But we are just going circles in what modern day s.c. designers trained us to be: dumb consumers.

Think about it. We can have a sandwich composite with the outer layer as thick as a plain GRP hull. Then the sandwich structure gives us so many extra benefits: stiffness, strength, insulation.

Weight saving? What weight saving. (Note no question mark.) Lagoons and other such "weight saving technology" boats get regularly overloaded by their owners. Weight saving is very good if we want a light boat. And provided we can stay light. A modern cruiser is not "go light" minded person.

It is clear to anyone who understands the basics of physics (and I will disagree with the apparent necessity to have any extra amount of techie know-how to understand how laminates work and why) that if we keep weight constant we can get stronger (to area load, not to point load) laminate with a sandwich technology. But, in mass cruising context, contrary to what many may think, this "go lighter" trend with designers has nothing to do with "go stronger".

We are not racing. We are hardly ever sailing. The whole "lighter" thing is out there for the cruisers only to save on resins and other materials, making it possible to build cheaper boats. The same boats can be sold at a huge margin thanks to mortgage technology. ;-)

There are excellent quality, strong and safe sandwich boats around.

For those who are willing to pay the price.

b.

Wow, can't say I agree to a lot of what you said except for maybe the last two sentences.


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[DoubleWhisky]

Originally Posted by barnakiel

But we are just going circles in what modern day s.c. designers trained us to be: dumb consumers.

Think about it. We can have a sandwich composite with the outer layer as thick as a plain GRP hull. Then the sandwich structure gives us so many extra benefits: stiffness, strength, insulation.

Weight saving? What weight saving. (Note no question mark.) Lagoons and other such "weight saving technology" boats get regularly overloaded by their owners. Weight saving is very good if we want a light boat. And provided we can stay light. A modern cruiser is not "go light" minded person.

It is clear to anyone who understands the basics of physics (and I will disagree with the apparent necessity to have any extra amount of techie know-how to understand how laminates work and why) that if we keep weight constant we can get stronger (to area load, not to point load) laminate with a sandwich technology. But, in mass cruising context, contrary to what many may think, this "go lighter" trend with designers has nothing to do with "go stronger".

We are not racing. We are hardly ever sailing. The whole "lighter" thing is out there for the cruisers only to save on resins and other materials, making it possible to build cheaper boats. The same boats can be sold at a huge margin thanks to mortgage technology. ;-)

There are excellent quality, strong and safe sandwich boats around.

For those who are willing to pay the price.

b.

+1

[44'cruisingcat]

Maybe you guys hardly ever sail. I sail a lot.

[Cadence]

Originally Posted by barnakiel

http://www.balticyachts.com/baltic-y...pdf?id=1150363

Good porn. Does not take a Ph.D. in physics to read and understand.

b.

Thanks! Looks like a good comprehensive read. I'll save it and go through it a piece at a time.

Thanks again,
Roger

[DoubleWhisky]

Originally Posted by 44'cruisingcat

I sail a lot.

Good for You

[Cadence]

Originally Posted by DoubleWhisky

+1

I'd have to agree in general. However I guess some people do want a light and fast boat and load them correctly. If that lights their fire fine. For those that have no idea and load the boat with the sacrifice in strength and really should have had a cruising boat.

It ain't my problem.

[minaret]

Originally Posted by 44'cruisingcat

Maybe you guys hardly ever sail. I sail a lot.

Nope. Too busy fixing broken boats.

[minaret]

Originally Posted by monte

Agreed b, I think the important thing to consider is nothing to do with skin thickness or layup, it's the overall engineered design which most of us aren't qualified to understand, especially so without complete plans and working drawings and engineering calculations. Supplying the layup schedule is like supplying the steel thickness for a bridge with no other data such as working load, span,web and bracing, etc. where a solid glass hull derives it's strength from its single layer of resin and layers of matt, a cored hull can have the same stiffness and strength with a much lighter layup, and consequently a cored hull with additional bracing from floors and bulkheads can also be constructed with a thinner lighter layup. The cored hull may be as stiff and structurally sound as the solid skin, but will be more vulnerable to impact loads like hitting the hard stuff.

So, which bridge would you choose to cross? One that you have some data on, or the one for which you have none? Hull scantlings are an important factor, and one which is easy to compare (if you can get anyone to give you the info). It's certainly not the only factor, but it is a critical one. Especially for boats with no core, such as the one we have been discussing here.

[smj]

Originally Posted by Cadence

Thanks! Looks like a good comprehensive read. I'll save it and go through it a piece at a time.

Thanks again,
Roger

Really was a good read. They are of the opinion that a well built cored hull will have more longevity than a single skin polyester hull.


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