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Old 13-12-2014, 23:05   #46
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Location: Liveaboard cruiser. Home port Brisbane, Queensland, Australia
Boat: Lagoon 400
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Re: Leopard Catamarans from South Africa

Quote:
Originally Posted by Dulcesuenos View Post
Ahh you may want to check some things before making these kinds of comments.
The difference in keels is you rip open a lagoon keel you flood the boat.
On the difference of glass thickness, I've seen pictures measured of the lagoons glass thickness below wl and it is a few mm Thinner than the outer skin layer on the leopards and roughly equal to the inner skin layer.
Have you seen Lagoons with damaged keels that flood the boat? Mine's solid for all but the top 6 inches of it's structure.

The "pictures" of the thin Lagoon bottom layup were comprehensively debunked on this forum. I think you'll find they were of the non- structural cover plate that surrounds the saiłdrive leg, not the hull bottom at all. Perhaps check your facts.

I'm not attempting to rubbish the quality of Leopard Catamarans. They are well constructed catamarans. I simply joined the thread to challenge another Lagoon bashing post.

Why do you think builders use cored layup in the first place? So that each of the 2 fibreglass skins can be far thinner than a solid layup in order to save weight and yet still have a structurally strong laminate. It would be counter productive and un- necessary to use a balsa or foam core if the outer skin was so thick that
it provided all the structural strength required.

When we discuss a grounding the structural strength becomes way behind the ability of the material to resist being ground, cut and gouged away. In this regard, balsa or foam would as much resistance as ice- cream. Not sure where the bullet proof chest comes in?
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Old 14-12-2014, 00:29   #47
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Re: Leopard Catamarans from South Africa

Balsa's main use is weight saving,after that it is glassed then it has a performance similar to solid layup,but interestingly it has a higher deflection and puncture resistance than steel 4mm or ally6mm (that's off ATL website)

this is why so many builders prefer it

i agree it is easier to grind and gouge but it needs to wear the glass away first,most groundings i see are just bad scrapes (easily repaired) steel and ally corrode, ally from the inside out, so i don't understand many of the posts here glass and balsa/foam will out last metals with little upkeep if used correctly in the first place and give more boat for the dollar.after all we swapped from wood to glass to save money and upkeep

there are plusses and minus for ALL MATERIALS.
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Old 14-12-2014, 18:04   #48
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Re: Leopard Catamarans from South Africa

Quote:
Originally Posted by aclmck View Post
Balsa's main use is weight saving,after that it is glassed then it has a performance similar to solid layup,but interestingly it has a higher deflection and puncture resistance than steel 4mm or ally6mm (that's off ATL website)

this is why so many builders prefer it

i agree it is easier to grind and gouge but it needs to wear the glass away first,most groundings i see are just bad scrapes (easily repaired) steel and ally corrode, ally from the inside out, so i don't understand many of the posts here glass and balsa/foam will out last metals with little upkeep if used correctly in the first place and give more boat for the dollar.after all we swapped from wood to glass to save money and upkeep

there are plusses and minus for ALL MATERIALS.
+1 Good post.

Balsa core has a much better record here in Aust with seemingly better practices by builders than in USA where it has often been inappropritaly used.
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Old 15-12-2014, 00:10   #49
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Re: Leopard Catamarans from South Africa

Quote:
Originally Posted by aclmck View Post
Balsa's main use is weight saving,after that it is glassed then it has a performance similar to solid layup,but interestingly it has a higher deflection and puncture resistance than steel 4mm or ally6mm (that's off ATL website)
its really nice to see that someone really does get it..

in this discussion between single skin and cored composite, a lot of people seem quite ignorant of the huge advantages cored layups present. Yes they can be lighter, but also they can be a lot stronger on the same weight. The entire aero industry has followed this pursuit for opposite reasons, generally to reduce weight but maintain strength.

Separate a single skin design model into two and insert a foam core to double the skin thickness, panel rigidity goes up by 7 times and strength by 3. The weight of the model is barely different from a single skin.

Use the same layup with a 4x thickness core, and the relative stiffness increases to 37 times, the strength to 9.2 times, but the weight only increases to 1.06 times.

Notably with composites one can vary the layups to include fibres, biaxial, triaxial, kevlar, carbon, etc which also greatly affect the engineering utility of the design.

I challenge anyone to put their hand up if they think that isnt an advantage.
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