Adding vee to cat hulls

We have to work with regulations, unfortunately. And one still can design light boat for CE-compliance, but it won't be easy to modify in terms of certification. Design loads depend on length of hull and weight, and we originally design within 5% structural margin of compliance, especially the bottom.

I mean if original deigner is involved and he approves modification - in most cases would be no problem, but frankly speaking this is experiment for customer's money.

I am sure there are few sucess stories, but there is another side of coin. Extension without re-considering all structural loads is amateurish approach.

 

Which was exactly the case in the examples I mentioned

And no where was the suggestion made to do that

 

Unfortunately the reality is not always there; some known multihull designers 'design' their boats in CorelDraw and do no produce any structural calculations for their designs. Yes, their boats sail well When it comes to modification, it is even worse... There is sample boat sitting here, in local marina - designed by 'known Australian designer'.

 

Known for what exactly?
Good designs or ***** designs.

I would love to hear a name and details, perhaps send a PM?

At the end of the day any mug can churn out some drawings and call himself a designer and some mug will pay big money for said drawings.

But this is not the type of designers and or boats I was talking about
I did mention Crowther as in Lock Crowther as being one of the main vessels I have seen cut, added to and modified over the years and I think even you would agree that he was one of the best in his field at the time.

 

Will send a PM.

Sure would agree.

 

It is IMO rubbish to suggest that every multi with a stern extension or plumbed bows is substandard. The facts (ie the number of boats so modified and sailing around quite happily) don't seem to bear this out.

in any case your answer completely avoids Sabahcats question. What is your claim to fame?...

 

Take the rules, make calculations of scantlings of extended version. If it does not comply, it is substandard. However they could sail good. Period.

 

And presumably substandard how ever sufficiently strong they are, even if they don't meet the rules you design to.

I repeat the question. What is your claim to fame? Or put more plainly what cruising sailing multihulls have you designed? And how many have been built?

 

Have You ever done scantlings? Any rule, ISO12215, LR SSC, ABS or GL? Do You know how they define design loads? If You have not, thee is no point to discuss the subject. For Your reference, even for racing boats ORC requires ISO12215 or ABS compliance for some race categories.

Read Australian Multihull magazine; plenty of them are published there as well as launching info.

 

Nice Straw Man. No. and I don't need to in the context of this discussion.

I read it regularly but don't know which of the many boats represented you refer to. So once again you avoid the question. Who are you and what boats have you designed that have appeared in Oz multihulls?

 

OK, then we do not need to waste time discussing term substandard with someone who is unaware of standards, right?

See profile.

 

I'm well aware of what the term substandard means. However I think you misuse it in the context of this discussion. At the risk of starting a circular argument I repeat: It is IMO rubbish to suggest that every multi with a stern extension or plumbed bows is substandard. The facts (ie the number of boats so modified and sailing around quite happily [and not falling apart]) don't seem to bear this out.

Nice to see a couple of bridgedeck sailing cats alongside the impressive range of powerboats you've designed.

 

OK, let's call those boats proven, for clarity? Many of them would turn out substandard if length/weight increased.

Besides I never said that ALL extended boats are substandard.

More than couple. But this is what sailing snobs usually point

 

Oh dear oh dear!
We get emotional again.
Jamez, let me assure you that Alik DOES have a claim for fame. I know him personally. (Now of course you may ask what my OWN claim will be )
Perhaps the general heat that I feel here is simply 'vocabulary'?:
ISO or CE and others have minimum requirements.
If -by calculation- after a modification these values are not met, then the whole boat is below the standard as per procedure.
Racing boats for example have not automatically such minimum standards, and so it comes that (so-specified) sub-standard boats still do not fall apart right on first launch.
Can we make peace now and get back to technology?

 

Just a little tidbit to add:

ABS Offshore rules have no problem at all with secondary bonding.

If you look at the way most one-off cats are built in the world, they are secondary bonded from stem to stern along the keel and along the deck. Typically a biaxial tape is used for this. My own ABS Offshore compliant boat is designed this way. In its entirety, a Bob Oram boat is made from taped flat panels. Fusion catamarans are all taped together.

None of these boats is known for a quality problem or for not adhering to standards.

Although the concept of the modification may or may not be correct, the idea of secondary bonding a catamaran hull is surely not a problem, as it is supported by class rules.