Are Cats Made from Duflex Panel Kits Strong ?

[aclmck]

Originally Posted by nimblemotors

Count me in the armchair camp, but it is a definite disadvantage if a material must be used in tightly controlled ways, and otherwise would fail.
Having re-cored a balsa cored boat that was soggy (speedboat),
I tend to think it has downsides.
It just might be fine until 10-20 years later, when the boat isn't pristine and all 'as designed' anymore. No boat remains that way.
It seems to be boats made to be light in particular, can't take much of a beating, and get holed and sink rather too 'easily' in my view.

I am personally leaning to building my hulls using solid glass,
but still researching options.

Just my perception perhaps but most of the people that build one off custom boats (and a great many do) actually use them when complete so the tied up to a dock mostly for 10-20 years is not a good comparison to a boat that has multiple miles on it but only a few years old.

Mostly the boats with problems fall into the tied up category (not all) and like many unused boats little problems are not found until they are major.

Many boats have glass hulls then use composite panels for the rest, even Schionning spirited 38 has a glass"sole" with panels above

It appears you are building a cat why not talk to some cat designers to find their thoughts on what to use (Oram, schionning etc etc ) they all have differing points and you may in fact change you views good and bad regarding different methods

I Did and changed and now wouldn't build any other way than using composite panels.

Just remember aluminium,steel,timber and glass will fail if not used in a tightly controlled way as well, you are putting all of these products in an extreme environment which I can be unforgiving.

Another thing i have found is that saltwater does not cause as much trouble as fresh in timber products.(maybe the salt has a preservative of sorts when in timber)

i can point you to boats built light that basically race everywhere they go, have done thousands of miles and are 10 + years old that have no problems, they are however maintained to a serviceable standard, like wise i can point to boats of the same age not maintained , built like brick s**thouses and now have problems.

[44'cruisingcat]

Agree with much of what you say, but would point out that the Spirited 380 has balsa cores in the hull "shoes".

[44'cruisingcat]

Originally Posted by nimblemotors

Count me in the armchair camp, but it is a definite disadvantage if a material must be used in tightly controlled ways, and otherwise would fail.
Having re-cored a balsa cored boat that was soggy (speedboat),
I tend to think it has downsides.
It just might be fine until 10-20 years later, when the boat isn't pristine and all 'as designed' anymore. No boat remains that way.
It seems to be boats made to be light in particular, can't take much of a beating, and get holed and sink rather too 'easily' in my view.

I am personally leaning to building my hulls using solid glass,
but still researching options.

Of course balsa has it's downside. I think pretty much this entire thread has been spent discussing them.

But doesn't every material? Re solid glass construction - the same storm which damaged the cat I've been repairing, also blew at least 3 other boats into the same mangrove forest. One that I've seen was solid fibreglass. It is basically now a scattered pile of debris, barely recognisable as a boat.

[spiritcat]

Check out this site to see what can be built fron Duflex panels - www.streamline-catamarans.com. Streamline have built a number of large commercial and private boats.

Peter

[downunder]

Originally Posted by aclmck

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It appears you are building a cat why not talk to some cat designers to find their thoughts on what to use (Oram, schionning etc etc ) they all have differing points and you may in fact change you views good and bad regarding different methods

I Did and changed and now wouldn't build any other way than using composite panels.

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Nimblemotors should speak with American cat designers Kurt Hughes and Chris White re solid fibreglass.

Agreed that Australian designers/builders do not have any issues with either balsa or foam sandwich under the waterline.

[downunder]

I note from the June/July Australian Multihull World that Schonning Desigms has a Legend 60 currently underway in France using ATL type composite panels.

Apparently ATL Composites based in Australia and MuH von Linden a long established composites supplier from Wessel in Germany have formed a joint venture company to produce DuFLEX panels for the European Market.

Thjis overcomes the shipping and importing costs of the EU. Imagine will now see more Duflex construction in Europe in the future.

[beiland]

Originally Posted by 44'cruisingcat

But doesn't every material? Re solid glass construction - the same storm which damaged the cat I've been repairing, also blew at least 3 other boats into the same mangrove forest.

One that I've seen was solid fibreglass. It is basically now a scattered pile of debris, barely recognisable as a boat.

I wonder if any of that damage could be related to the 'brittle nature' of solid fiberglass?

Granted steel is NOT a multihull material, but imagine how a somewhat lightly built steel hull might had faired in that mangrove forest....quite dented, but not punctured?....ductility

[beiland]

Originally Posted by 44'cruisingcat

Agree with much of what you say, but would point out that the Spirited 380 has balsa cores in the hull "shoes".

I know that the Solitary Island 12M cat did have solid glass hull 'shoes'. I don't know of any others.
http://www.multihull.com.au/site/www...fic_40_kit.pdf

[downunder]

Originally Posted by beiland

I know that the Solitary Island 12M cat did have solid glass hull 'shoes'. I don't know of any others.
http://www.multihull.com.au/site/www...fic_40_kit.pdf

Very few Solitary Is 12M were ever built by comparison with Schonnings/Orams out of Duflex so don't consider it a very useful example to quote.

[44'cruisingcat]

Originally Posted by beiland

I wonder if any of that damage could be related to the 'brittle nature' of solid fiberglass?

Granted steel is NOT a multihull material, but imagine how a somewhat lightly built steel hull might had faired in that mangrove forest....quite dented, but not punctured?....ductility

There's a steel boat in there too. The salvage guys say it won't ever be coming out.

If you're trying to suggest that a polycore boat would have fared better, frankly, that's laughable.

[nimblemotors]

This surveyor David Pascoe does not like cored boat hulls.
Opinions on his opinions?

I will state for the record here that I have NEVER endorsed the use of balsa cores in boat bottoms, nor any other type of core materials.

Sea Ray and Balsa Core Bottoms - by David Pascoe, Marine Surveyor

[beiland]

Originally Posted by 44'cruisingcat

There's a steel boat in there too. The salvage guys say it won't ever be coming out.

......in that mangrove forest
Is that possible due to its greater distance into the mangroves,...or its greater weight to try and savage....out of cranes range? lots of other factors could elicit this statement.

Can you get them to say it is damage to the vessel that brings this response?

[beiland]

Originally Posted by 44'cruisingcat

If you're trying to suggest that a polycore boat would have fared better, frankly, that's laughable.

So I posted this previously

Originally Posted by beiland

BIG BANG #1, Lion Whelp's impact test

.....excerpted from an article that appeared in Soundings mag,
Building a Bullet Proof Boat
http://www.soundingsonline.com/boat-shop/on-powerboats/266332-building-a-bulletproof-boat

.....Have a look at some of the photos and the damage here:
Testing the NidaCore
http://www.portlandyacht.com/lionswhelp/whelp.html

BIG BANG #2, catamaran drop test


A customer of the NidaCore Corp, in the Caribbean islands had a 65' commercial charter boat, cored entirely with NidaCore poylpropylene honeycomb (less the hull bottom), including hull sides, deck and superstructure. It was scratched and water damaged on a coral reef during a major hurricane. The insurance copany agreed to write off the boat on condition that customer takes boat out of service and does not attempt to repair it. The charter boat operator agreed to dismantle the boat and discard of it.

Using one of the marina's cranes, they hoisted the 50,000 lb boat 50 feet in the air and dropped it onto a concrete parking lot, hoping that they would be able to collect the pieces and discard of them in the dumpster. To much of their astonishment the boat remained completely intact, with no visable structural damage. They repeated the procedure continuously for a couple of days to no avail. Finally to accomplish their mission they had no other alternative than to rent a chainsaw to cut the boat into pieces.


Although somewhat of an extreme example, it clearly indicates the superior nature of a 'resilient' cored-sandwich construction in boats. The increase in impact strength as compared to single-skin laminates is better demonstrated if one sees the core as a shock absorber that evenly supports the outside skin from impacts and protects the inside skin, while still having enough elasticity maintain the bond line between the core and the skins. Experience shows that although sandwich construction is not completely punture proof, it significantly increases skin penetrating puncture resistance.


The more brittle cross-linked PVC and SAN foams would simply crumble and shear under a sever impact whereas polypropylene honeycomb cored structures would be locally damaged, however the core structure would be intact, and cells, although elongated would still keep their structure and shape, ready to absorp or withstand more impacts and compressions.




Brian's NOTE: I have not personally verified this report. It was printed in a in sales manual/spec sheet document passed out by NidaCore corp.

[Factor]

Is there a single designer who is prepared to specify Nida Core?

genuine question.

[sparau]

Originally Posted by beiland

It was scratched and water damaged on a coral reef during a major hurricane. The insurance copany agreed to write off the boat on condition that customer takes boat out of service and does not attempt to repair it. The charter boat operator agreed to dismantle the boat and discard of it.

Using one of the marina's cranes, they hoisted the 50,000 lb boat 50 feet in the air and dropped it onto a concrete parking lot, hoping that they would be able to collect the pieces and discard of them in the dumpster. To much of their astonishment the boat remained completely intact, with no visable structural damage. They repeated the procedure continuously for a couple of days to no avail. Finally to accomplish their mission they had no other alternative than to rent a chainsaw to cut the boat into pieces.

Brian's NOTE: I have not personally verified this report. It was printed in a in sales manual/spec sheet document passed out by NidaCore corp.

That seems like an odd story. I suppose if you had the crane it would be fun in a mythbusters kinda way but i can't imagine anyone doing it for any other reason than to test the boat / material.

If true what is the world coming to where we smash 50,000lb of non recyclable, non renewable boat for being "scratched and water damaged".