Is the research on self righting of catamaran innovative?

After long-term research and development of catamaran, is the research on self righting of catamaran innovative? Although they are all floating bodies on the sea, catamaran has two same floating bodies, so it is more difficult to have self righting ability, isn't it?

 

Technically, yes, it is more difficult to make a catamaran self-righting.
However, does this mean it cannot be done.. no, of course not, as it can be.

The issue will be what is the prime objective of the catamaran?...as that shall dictate how possible it will be to do, with the design you wish to be self-righting.

Since a multihull, with the wider hull spacing, creates a large restoring force, which is the opposite of what you require, once the vessel is knock down. With the KG being relatively 'low' in relation to the metacentric height leads to a high GM, the issue will be to create a design where the spacing and size of the hulls does not result in a large restoring force coupled with a very low GM.

So, with clever use of the hull size/shape, and ensuring the KG is 'ideal' to result in a low GM, then it is possible.
Otherwise, it tends to become extremely challenging at best.

 

An example of a self righting catamaran for whitewater was the Russian Bublik. Types of Rafts for Whitewater Trips | Whitewater Guidebook https://www.whitewaterguidebook.com/pro-tips-types-of-whitewater-rafts/

 

In this search, probably unsuccessful, to find a lower value of the GM, that is, and among other things, to reduce the inertia of the flotation, it is likely that we would come to the conclusion that the solution is a monocoque.
It would be necessary to present a concrete example that shows us that it is possible. Talking just to talk is easy.

 

Can you please post an example of a monocoque catamaran that is self righting...as per your description...

Since, as you say:

 

Who has spoken of monocoque catamaram?. I don't. Don't talk nonsense, please. Don't let passions override your intellect and think a little before writing. Be a little more serious and professional, if that's not too painful for you.

 

Oh dear..

If you're going to jump into threads, at least read the Ops request, rather than an immature reply to snip at others that actually do answer the question:

As is asked for, noted above, repeated for the hard of reading:-

The question is there for anyone to read....the subject hull form is...catamaran.

Hence, please show everyone your:

Or is it the usual case of the kettle calling the pot black:

Indeed..!!

 

It is possible to have a self righting catamaran as the examples shown by KJL38 show.
Either the sail [and perhaps chambers in the mast...]. is inflatable or there is a deflated arrangement similar to a life vest [boat vest?] that by pulling a cord sets off the inflation , this could be automatic.. think attached inflatable liferaft , I suspect that there would be more than one or chambers and would end up quite heavy to cope with the loads asked of them. If they were inflated before capsize they would probably throw the boat around and make for an uncomfortable ride and make steering difficult except for going with the wind.

 

Anything is possible.

But as noted, you need a hull shape that provides a low restoring force coupled with a low GM.
Once you have that, it becomes possible.

Because once you have that, once the vessel is knocked over, what do you need to right her back up?...buoyancy...placed in the correct location!
So, that is where judicial placement of buoyancy/volume/shape - beit, in the mast top of the mast...anywhere in fact - that is shaped to provide that buoyancy when inverted, to recover the hull back to up right, simply by being 'unstable' when inverted.

 

It's quite interesting, you opening up my mind now. Thank you! There are many researches on self righting of catamaran.

 

Why not just use a hinge design, so the hulls fold mostly together when it is upside down? That way it can be very stable (because the hulls are widely spaced) when upright, but not so stable when upside-down. Plus, the hulls are up in the air when upside down, making the boat top-heavy - so it flips back over. Once upright, the hinge lets the hull spread apart.

The problem of course, is that they might instead just come to the surface, so the boat is on its side.

So instead of an entirely passive design, let me add an extra element: a kayaker or canoeist with a paddle, who flips the boat upright. Or a smart computer/mechanical system with momentum wheels. Bringing the hulls together just makes it easier to roll.

The inflatable raft system with the large inflatable arch looks awkward. Plus, I can imagine wind conditions that prevent it from rolling up.

Or shallow water where the big inflated arch gets stuck on the bottom.

If you want a passive design - how about a trimarain instead. The center hull normally rides deeper, with a very heavy bottom ballast. The ballast is sufficient to bring one of the hinged hulls upwards and over. But there are still wind/shore-hitting conditions where under it will never right itself - but that is true of any self righting design.

 

I just realized my folding trimaran (with a limited range of motion hinge) idea could be done with a cat too. But in any event, the hinge would bounce - making it fragile and trouble prone. The hinge would need to be padded, and you might need springs and a release catch. Probably better to winch it open and shut by hand instead of automatic.

And you still need a way to drop the mast (if it is a sailing vessel) while it is upside down - possibly another system of winches.

The upside is that folding into a compact shape would also make it easier to trailer or car top. The downside is that would be heaver than a rigid cat, with more moving parts, hence more trouble prone, and slower. It's obvious that when you add extra constraints (like self-righting, to a design, there are often trade-offs. So I assume the idea has been thought of many times before.

Those whitewater self-righting catamaran rafts must have trade-offs too. Obviously a very slow paddling design. The very things that make them self-righting must also make them easy to flip. I wonder how fragile the lightweight overhanging arch is. And, while they may be fine in deep water with no rocks to pin against or get caught on, they must be pretty dangerous when there are a lot of rocks near or at the surface.

 

Their main limitation was getting caught in holes. The movie "A Glorious Way To Die" has information on them, mostly starting around 18 minutes.

The Creaturecraft rafts is another self righting raft design Rescue Boats | Inflatable Boats | CREATURE CRAFT https://www.creaturecraft.com/

 

OMG. I had no idea some of these boats were home made jury rigs.

It looks like a substantial part of the safety issue comes from being able to go places that are too dangerous for whitewater boaters in other craft to go. In the much less risky places I have dared to paddle, rafters can often be rescued by kayakers. And the kayakers can often self rescue, because of their higher speed and maneuverability. These rafters are very strongly dependent on rescues from shore, which aren't always practical.

 

We hope that the ship can rely on its own shape stability to achieve self-reliance, just like kayakers can save themselves