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Old 07-03-2016, 18:34   #31
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pirate Re: The sexiest Catamaran ever?

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Originally Posted by tp12 View Post
I'm no expert but from what I've read, and you can look at Factor's comments above for an indication, is that not all reverse bows are the same and that they need to be taken in context of other design considerations made for the boat they're on.

I'd be interested in what you think about that? I'm keen to learn.
I have no designer knowledge or scientific explanations.. I got expelled from school at 15 and joined the Royal Navy.. so one could consider me uneducated and thick..
However I've a lot of sea time on a great variety of boats from dinghies to Destroyers in sea's from ripple's to 15 metres..
My gut tells me that those cats are great for coastal waters and fast fair weather cruising where the speed can get you in before the **** hits the fan..
However if you asked me to deliver one from SMX to Spain..??
I'd give you BVImatelots e-mail address. and I've delivered some heaps of **** in my time..
And that's all I have to say about that
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Old 07-03-2016, 18:45   #32
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Re: The sexiest Catamaran ever?

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I have no designer knowledge or scientific explanations.. I got expelled from school at 15 and joined the Royal Navy.. so one could consider me uneducated and thick..
However I've a lot of sea time on a great variety of boats from dinghies to Destroyers in sea's from ripple's to 15 metres..
My gut tells me that those cats are great for coastal waters and fast fair weather cruising where the speed can get you in before the **** hits the fan..
However if you asked me to deliver one from SMX to Spain.. I'd give you BVImatelots e-mail address. and I've delivered some heaps of **** in my time..
And that's all I have to say about that


Fair enough. It's true that I'm looking for a technical understanding of how they work, or don't work, versus normal bows.

Anyway Weavis, sorry for the hijack
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Old 07-03-2016, 18:52   #33
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Re: The sexiest Catamaran ever?

LOL

I still think the TAG is sexy!
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Old 07-03-2016, 19:12   #34
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Re: The sexiest Catamaran ever?

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Just one tip... if you plan on offshore.. pick your windows with caution.. there's a reason the Navies of the World abandoned those designs.. and never returned.

I'm not so sure your speaking correctly boatman. I just googled "US navy destroyer latest" and these are the first few images to come up...

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Old 07-03-2016, 19:15   #35
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Re: The sexiest Catamaran ever?

And now, more to the point...
I like a lot of the modern hot cars WITH the reverse bow thing (but not TOO much), but this is THE sexiest cat ever built.
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Old 07-03-2016, 19:21   #36
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pirate Re: The sexiest Catamaran ever?

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I'm not so sure your speaking correctly boatman. I just googled "US navy destroyer latest" and these are the first few images to come up...

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That's because US search sites get confused.. whether it floats or submerges matters not..
DESTROY is the keyword..
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Old 07-03-2016, 20:53   #37
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Re: The sexiest Catamaran ever?

I had seen both KATO and Attitude in isolation and favoured KATO probably
because I saw it so often cruising last year and it usually sailed past me at about double my speed but spotted them docked faily close together last week.
Sorry KATO.
Mind you my old fat bottomed girl is pretty sexy when she is being kind to me
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Old 07-03-2016, 22:46   #38
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Re: The sexiest Catamaran ever?

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its not an aesthetic thing, well its not an aesthetic thing in a high performance boat, A schionning G Force for example the reverse bows primarily aid in reduction in pitching which as well as being uncomfortable it a performance sapper, they also aid in dispersion of water as in the bow wave is less likely to climb and stay attached to the bow, leading to a reduction in spray. (having said that they will be wetter when the bow buries with more water coming on deck)

reverse bows on the Balance 451 - definitely a fashion statement, reverse bows on Mojo, a 15 metre schionning that weighs four tonne less than the shorter Balance, definitely not an aesthetic/fashion statement its all about performance.

For most of us a plumb stem with compound inner curve - e.g. Seawind or a lightbulb shape - e.g. shuttleworth or a combination of the two, e.g. Pescott, is probably more appropriate, Reverse bow boats will ultimately be less resistant to pitchpoling, but that will happen a three and four times the speed , so it is manageable - just slow the boat down.

My point is, it is a fashion statement on some boats, not all. If a boat has a WLL to Displacement factor of 750 kg per metre or more, no point to them at all, between 500 kg and 750 - marginal,under 500 probably worth it (all rough rule of thumbs - YMMV, consult your own naval architect, seek your own informed advice - ALSO NOT A CRITICISM OF THE BALANCE - just using it as an example of where I think the reverse bow thing is more fashion than function. I like the Balance - well I liked the original Balance - the Montebello 12.5, I sailed one a fair distance and it was a better than reasonable boat)
I fully understand the theory behind them. And in a racing context, especially when/if there's help available if you stuff them to far, & flip the boat, then I have Zero problem with them.

My issue is that with normal bows, burying them is a CLEAR sign that you're pushing things a bit hard. And that you might want to ratchet things back some. Whereas with reverse bows, they're designed to take green water over them/be immersed. And so it's not nearly so easy to tell where the limits of things are, with regards to how close to that line of exceeding the bouyancy of the bows is.
And once you cross that line, things are FUBAR.

Also, trying to teach a newbie about all of the factors which play into how hard you can push a cat, particularly one with reverse, wave piercing bows, will likely fry most of the circuts north of their neck.
Especially as to teach them where that line is, you HAVE to stuff the bows enough so that the ass end of the boat well & fully leaves the water.
And in point of fact, do so many times, in the course of teaching them how to safely sail & push the boat to/near it's limits.

When, honestly, it's more than freaky enough for most sailors, to only come close to burying the bows on a "standard" cat. Even experienced sailors.

Such is where my distaste for them from a sailing perspective comes from. The other part is that I simply don't like them visually. Much as I have distaste for the 80% of the cars on the road which all look alike, regardless of who made them. Or the plastic, faux chrome trim they're covered in. Such things are just plain UGLY.

Not to mention which, I'm guessing we'll see/are seeing, a lot of designers jumping onto this design trend bandwagon, who don't know/understand enough about reserve bouyancy, particularly at speed & in waves. And thus the percentage of racing cats which flip will climb for a while, until both the sailors & the designers, ratchet their knowledge base/levels up a few notches, across the board.

I'm not a luddite, but I do know how progress works. Including those who then want to institute more inane, nannyish "safety" rules, in order to protect us from ourselves. As if such were possible. And in so doing, it takes away from the purity of the sport.
I mean, such BS, has gone way, way past the red zone, on the "stupid gauge" already!
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Old 08-03-2016, 00:03   #39
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Re: The sexiest Catamaran ever?

Sorry Lads...This is sexy. Not those bars of soap in the water...
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Old 08-03-2016, 00:18   #40
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Re: The sexiest Catamaran ever?

Undeniably beautiful, but the discussion is about exciting cats. But don't let that stop you, its taken to post 40 to have a monohuller come in to the multihull forum and and tell us why we are wrong. Nearly a record for this place.
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Old 08-03-2016, 01:00   #41
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Re: The sexiest Catamaran ever?

The trick to understanding the effects of 'reverse' bows (the term does muddy the waters somehow) is not to think of them as a plumb bow raked back, but instead imagine them being a plumb bow with its forefoot pushed forward.
Cats genuinely designed with reverse bows (as opposed to those modified with them), are normally a tad longer than the same general hull shape with a plumb bow. So in effect you are not reducing reserve buoyancy at all, you are adding to it, and in a very important spot which greatly reduces pitching moment. You are also extending the waterline and allowing the entries to be be finer (less drag), all of which reduce bow 'stuffing' rather than add to it.

Its been mentioned that the design practice disappeared with WW1 warships, actually they are now found on almost all new anchor handling vessels, rig tenders and deep sea salvage vessels that are required to operate and maintain station in just about all conditions. To take it one step further, in a way the reverse bow principle never left, almost all cargo vessels since the early 70's have had bulbous bows (there have been no plumb or overhung bows found on them since), which employ many of the same principles as the reverse bow (in addition of course to the other more important functions relating to bow waves and friction), they however need to be combined with bow flares so as to keep the decks drier to protect deck cargo and hatch combings (a problem the new anchor handlers etc don't have hence them abandoning the bow flare completely in favor of the full swept bow).

Its actually fascinating engineering and I encourage anyone interested to dig deeper into it.
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Old 08-03-2016, 01:26   #42
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Re: The sexiest Catamaran ever?

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The trick to understanding the effects of 'reverse' bows (the term does muddy the waters somehow) is not to think of them as a plumb bow raked back, but instead imagine them being a plumb bow with its forefoot pushed forward.
Cats genuinely designed with reverse bows (as opposed to those modified with them), are normally a tad longer than the same general hull shape with a plumb bow. So in effect you are not reducing reserve buoyancy at all, you are adding to it, and in a very important spot which greatly reduces pitching moment. You are also extending the waterline and allowing the entries to be be finer (less drag), all of which reduce bow 'stuffing' rather than add to it.

Its been mentioned that the design practice disappeared with WW1 warships, actually they are now found on almost all new anchor handling vessels, rig tenders and deep sea salvage vessels that are required to operate and maintain station in just about all conditions. To take it one step further, in a way the reverse bow principle never left, almost all cargo vessels since the early 70's have had bulbous bows (there have been no plumb or overhung bows found on them since), which employ many of the same principles as the reverse bow (in addition of course to the other more important functions relating to bow waves and friction), they however need to be combined with bow flares so as to keep the decks drier to protect deck cargo and hatch combings (a problem the new anchor handlers etc don't have hence them abandoning the bow flare completely in favor of the full swept bow).

Its actually fascinating engineering and I encourage anyone interested to dig deeper into it.
Thanks for that, it's the type of info I was interested in.

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Old 08-03-2016, 03:02   #43
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Re: The sexiest Catamaran ever?

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Its actually fascinating engineering and I encourage anyone interested to dig deeper into it.
+1 for reasoned thinking over knee-jerk reactions. Aluetian kayaks with bifurcated bows probably being the most ancient examples. Proven design from a thousand years ago.
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Old 08-03-2016, 03:04   #44
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Re: The sexiest Catamaran ever?

Another example.
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Old 08-03-2016, 03:16   #45
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Re: The sexiest Catamaran ever?

Modern inverted bow.
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