Are Cats Made from Duflex Panel Kits Strong ?

[UpOnStands]

Originally Posted by StuM

So that 50ft drop has now become 15ft. That's a lot more believable.

and dropped onto a sandy beach? lets see. boat was hulled then beached so
are you likely to get slings under both hulls or just one sling under the bridge deck. Imagine they tried to break one hull off, so one hull resting on the sand, the other lifted 15 ' - no failure so hull dropped down onto the sand?
If the hotel owner really wants the boat gone from the beach he is not going to accept attempts to smash the boat to bits on the beach. IMHO

[beiland]

Originally Posted by StuM

So that 50ft drop has now become 15ft. That's a lot more believable.

And is the cat in those pictures going to be 50,000lbs after it's been stripped of engines etc so that it can dropped to break it up? I doubt that.

Interesting how facts get added in? Who said it had been stripped of engines or anything else?

Yes one would think so, but perhaps there was no time allotted to that?

[beiland]

Originally Posted by UpOnStands

and dropped onto a sandy beach? lets see. boat was hulled then beached so
are you likely to get slings under both hulls or just one sling under the bridge deck. Imagine they tried to break one hull off, so one hull resting on the sand, the other lifted 15 ' - no failure so hull dropped down onto the sand?
If the hotel owner really wants the boat gone from the beach he is not going to accept attempts to smash the boat to bits on the beach. IMHO

Some more assumptions? "The vessel sat on a reef and chewed up the keels and then beached at some resort."
Sounds like the beach area was not just sandy, but rather 'rocky-reefy'?

Can't say the exact nature of the dropping procedure,...one hull or both.
at any rate it speaks well of the impact resistance.

BTW, have either of you gentleman ever read some observations by the famous designer Nigel Irens concerning complaint hull layups and reinforcements. I can't find them right now, but they are worth reading. He discovered them following the post examination of some failures on a few of those racing multi's.

[beiland]

Originally Posted by beiland

BTW, have either of you gentleman ever read some observations by the famous designer Nigel Irens concerning complaint hull layups and reinforcements. I can't find them right now, but they are worth reading. He discovered them following the post examination of some failures on a few of those racing multi's.

Here is one example...
As the 60ft tris get ready for their TJV start, designer Nigel Irens talks to Elaine Bunting about last year's damage
Read more at "They'll never arrive 100% intact" - Yachting World

“Last year there was a bulge in new boats being built and a wholesale move towards building in pre-preg carbon and Nomex core. Everybody had drifted towards this technology and although the stuff’s been around for a long time, what went wrong was the result of that. There may be a big learning curve now underway and it may be that some people won’t use these materials again. We certainly haven’t used them on Ellen’s boat [her new 75ft trimaran, currently building in Australia]. We’ve gone back to more traditional core material.

“Basically, what it’s all about is the materials have very adequate static strength and there’s no problem in terms of sheer pressure head. But in reality what’s appears to be happening is that there is not enough capacity to absorb the loads that the skin sees. These are much, much higher than was the case with a softer, more forgiving material.”

What made it all the more catastrophic, says Irens, is that failure of this type of structure spreads very quickly. “It’s a very localised sort of wave impact or slap that causes the damage. But because the material is very rigid, the rate of propagation of damage is very fast.”

Read more at "They'll never arrive 100% intact" - Yachting World

[flatop]

Mate, go on youtube and watch "sail, surf roam". Spirit 480 built in Tassie. Boat looks great and the guys are sailing her everywhere. Lots of Tech info as well. It is a entertaining watch regardless.

[beiland]

Originally Posted by flatop

Mate, go on youtube and watch "sail, surf roam". Spirit 480 built in Tassie. Boat looks great and the guys are sailing her everywhere. Lots of Tech info as well. It is a entertaining watch regardless.

I went to their website and found these 'build photos'.
the VESSEL — Sail Surf ROAM

Quite interesting, except I am not a fan of balsa core.

[Dirk01]

Originally Posted by Robertcateran

But seem quite strong enough for Australian conditions. Didn't know that the conditions in Europe were worse than Bass Strait or Cape Leuwin

Have you heard about the German saying "Nordsee ist Mordsee"?
Have you heard about the Fastnet Rock race desaster 1979?
Any suggestions to the Biskay Bay?
Ever heard about the Mistral and the "Golf du Lion" or Bora in Croatia?
And there are many many more examples.

I got a KITA by only some of them (and luckily not at the upper end of the scale) - it was no fun anymore. It was fight. Don't need it again.

Don't underestimate European waters.

Don't underestimate ANY waters ...

Anyway, CE might be good for stronger hulls. But brass thru hulls are allowed as well (with the restriction of regular checks and exchange after 5 years). IMO an absolutely no go.

You can find good things and bad things at every standard.

Cheers
Dirk

[Sand crab]

Europe never gets harsh conditions

https://www.youtube.com/watch?v=LHZ43R2gyAE

[Dirk01]

Originally Posted by olliric

Yes, unfortunately there are no care free materials that would make a light cat.

Structural Issues : Core Materials
With duflex panels I have the option to chose the core type. I am still debating what's better for the underwater part of the hulls. I am considering Airex duflex below waterline and balsa above.

Are David Pascoe's over two decades findings are still valid?
Or has foam core improved over the years?

Cheers
Dirk

[Sand crab]

Originally Posted by Dirk01

Are David Pascoe's over two decades findings are still valid?
Or has foam core improved over the years?

Cheers
Dirk

His article says most PVC foams have a shear strength of 60 to 80 PSI or even less. Corecell which is not PVC starts at 61 PSI and goes to 373 PSI for the dense stuff. So I would say foam has improved lately.
https://www.gurit.com/en/our-busines...als/corecell-m

Also just about every high performance multihull and some not so high performance models are built with foam core these days so I think it's proven itself in the 24 years since that was written.

[Dirk01]

Can't find the post of the temperature, but someone measured up to 143°F or so.

Divinycell HP
Divinycell HP brings all the advantages of Divinycell
H together with high temperature resistance
for prepreg processes or temperature critical
components such as dark topsides. It can handle
processing temperatures as high as 143°C (290°F).

Cheers
Dirk

[Dirk01]

Originally Posted by 44'cruisingcat

Sheer and compression strength are very inportant in the core. The core's job is to keep the laminates apart, and in position relative to each other. A core which is weak in either compression or sheer will result in a less stiff panel, all other factors being equal.

I've met "Lyra"'s designer/builder, and he has mentioned the lack of sheer strength in his cores. (He makes a brief mention of it in his article too.)

Divinycell HM
Divinycell HM is our ultra-performance core
designed for fast marine hulls where extra
toughness is required. Divinycell HM combines all
the qualities of Divinycell H, plus a very high shear
elongation. As a result, Divinycell HM is a very tough
product, capable of absorbing high dynamic impacts
such as slamming loads.
Divinycell HM’s very high elongation (above 40%)
exceeds the minimum requirements of ISO12215, GL
and ABS rules to allow for reduced safety factors in
structural calculations, providing a lighter, yet strong
structure. Divinycell HM offers a high operating
temperature, reducing the risk of print-through on
dark hulls.

Cheers
Dirk

[PippaB]

Originally Posted by Dirk01

Are David Pascoe's over two decades findings are still valid?
Or has foam core improved over the years?

Cheers
Dirk

They were probably a lot more valid in 2009 when olliric and the others were having the discussion to which you are responding.

[Dirk01]

Originally Posted by PippaB

They were probably a lot more valid in 2009 when olliric and the others were having the discussion to which you are responding.

Thx to everyone who made this discussion possible. Less than 12 years later and whoosh, the situation has clearly shifted in the direction of foam core.

So It's now the right time to go for foam core

At least there are three options for me:
A) Seawind (1370)
B) Max Cruise Marine (Max 44 SC)
C) Grainger Designs (Raku 44)

So, which suits best for long time cruising for a couple?
And who is willing for a hybrid version + 2kWpeak+ PV + rejectable propulsion + kickup rudders + iductive coocktop + drywasher + dive equipment + A/C + watermaker + etc. etc. etc.)

But that's off topic. Maybe I should open a new thread in this direction...

Cheers
Dirk

[Matt Johnson]

Originally Posted by Dirk01

Thx to everyone who made this discussion possible. Less than 12 years later and whoosh, the situation has clearly shifted in the direction of foam core.

So It's now the right time to go for foam core

At least there are three options for me:
A) Seawind (1370)
B) Max Cruise Marine (Max 44 SC)
C) Grainger Designs (Raku 44)

So, which suits best for long time cruising for a couple?
And who is willing for a hybrid version + 2kWpeak+ PV + rejectable propulsion + kickup rudders + iductive coocktop + drywasher + dive equipment + A/C + watermaker + etc. etc. etc.)

But that's off topic. Maybe I should open a new thread in this direction...

Cheers
Dirk

Sounds like the Seawind would be the best option for you. The Max Cruise and Raku 44 are very much performance cats and the "+ etc. etc. etc." you listed will sink those narrow hulls. They have hull ratios of 12.5:1 vs the around 9:1 (just a guess from photos) of the Seawind .... that's a huge difference in payload and would allow all those items to fit aboard.