Gludy - the Raggie

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So avoiding damage in a storm is all about minimising the energy in the boat due to the velocity of the boat. A boat of mass mass 1 travelling at say 10 knots has a kinetic energy of 50 untis. Travelling at 5 knots this reduces to just 12.5 units and at 1 knot just 0.5 units - it is this energy in the speed of the boat that can damage the boat because it is chucking itself against the sea.

The lighter the boat the lower this energy a Fast Cat would have about half the weight and hence half the energy of a normal cat.

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Interesting! I always thought the QE2 should have been made from balsa wood. A boat of zero mass would clearly be the ideal.

Perhaps you should consider the relationship between the inertia of the boat and that of the water it has to move out of the way. It might also be wise not to consider the wave as a brick wall.
 
æInteresting! I always thought the QE2 should have been made from balsa wood. A boat of zero mass would clearly be the ideal"

That is not a sensible response - I would welcome a discussion on this but please say what you mean.

"Perhaps you should consider the relationship between the inertia of the boat and that of the water it has to move out of the way. It might also be wise not to consider the wave as a brick wa;;"

The whole point is that with a cat when underway its has little water to move out of the way.

Inertia is important. For example when at near zero speed with a parachute attached, I think that the heavier cat would be more comfortable than the lighter cat but the lighter cat would be safer providing it had the same strength.

Ads regards the space age multi-million pound racing boats - these are not cruising boats.Crusing boats tend to use well established technology but even this can result in obe boat being half the weight of the other for the same size.

I really would welcome a sensible discussion on any of these points but do think that specific direct points should be made.
 
[ QUOTE ]
In a storm we talk about the waves pounding us and the danger of a breaking waves - really that is wrong.

Its more like we pound the waves because we are heading into them. The water in a breakibng wave is a lot of froth and not to dangerous the real danger is hitting the bottom of the wave in front or going on broadside so it can broach you.

So avoiding damage in a storm is all about minimising the energy in the boat due to the velocity of the boat. A boat of mass mass 1 travelling at say 10 knots has a kinetic energy of 50 untis. Travelling at 5 knots this reduces to just 12.5 units and at 1 knot just 0.5 units - it is this energy in the speed of the boat that can damage the boat because it is chucking itself against the sea.

The lighter the boat the lower this energy a Fast Cat would have about half the weight and hence half the energy of a normal cat.

So the good news is that you can anchor your boat anywhere out there in the ocean and stop the punishment by reducing the speed of your boat down to almost zero and turning of the breaking waves in your path by creating a calm slick - even in 40 foot waves. This is done with a parachute.

Ultra light cats weighing a fraction of the FastCat brave the Southern ocean etc and survive.

Now take a proper look at the safety of three boats - a heavily built power boat 0 a sailing mono hull and a cat of either type..

There are two stable positions for the power boat - floating on top of the water or on the bottom.

The same for the sailing mono hull but this can roll and turn itself upright and so is much safer than a power boat.

Then there is the cat which has different stable positions- either floating or floating upside down - they do not sink and are designed to to float upside down with hatches to get in and out of them.

So when it comes to it we can choose to switch off the pounding of the waves in any boat by using a parachute. When disaster does strike would you prefer to be in a very stable upside down hull designed for just that or would you prefer to be alone just floating in your life jacket with your boat a mile underneath you?

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Sounds like people have been feeding you answers you want to hear - or is this Gludy self-taught naval architecture and oneanography?

I am highly sceptical of a lot of what you write above, but I'll leave it to people with more expertise to comment in more detail. I'll just make these points.

1. Comparing power boats with monohulls is pointless - they're not designed (in general) for the same work.

2. Have you considered that the fact that a cat is/may be stable inverted is NOT a virtue?
 
I think the main disadvantages with CATs are - restricted cabin space, restricted berthing opportunities due to beam and the type you are looking at have sails.

Sailing is a completly different proposition to motor boating and it requires a quantum leap in attitude change. I'd put money on you motoring rather than sailing the vast majority of the time, which begs the question, why bother?

Sorry to seem all doom and gloom, it's just that like many others here I'd like to see you happy with your next boat.
 
Observer

"Sounds like people have been feeding you answers you want to hear - or is this Gludy self-taught naval architecture and oneanography?"

By all means debate the issue but please try and refrain from piling on the normal insults - it does not add to any discussion.

If you wish to make points then make them - just stop the smearing bit.

"1. Comparing power boats with monohulls is pointless - they're not designed (in general) for the same work."

Power boats are normally monohulls - I do not know what your point is. My point related to remarks about their safety at sea and my response was clear.

"2. Have you considered that the fact that a cat is/may be stable inverted is NOT a virtue?"

Yes of course I have and having studied it in depth concluded it is a great virtue.
Typically a 50 foot mono sailing boat requires of the order of 50,000 lbs force to roll - the same size cat requires 250,000 lbs force .

Because of that enormous resistance to rolling or tipping its very rare that they ever do but in the even that they do, then they provide a stable inverted platform with hull hatches etc that provide access into and out from.

So please by all means comment on that - explain what you mean but do try and resist the easy smear bit.

If you disagree with what I have stated about heaving to with a parachute anchor - then tell me where you disagree.
 
Magnum
Thanks for such direct honest questions and opinions.

On the 50 foot cats I am looking at the cabin space is big - king size beds, dressing room, shower with bath - the owners have one hull all to themselves.

On the 52 foot Powercat in the BVI that I chartered I thought it so bad that i opted for a much cheaper mono hull and lost the substantial difference in charter costs I disliked it that much.

I am more than aware of the issue you raise but can promise that on a 50 foot cat there is no such problem and of course the saloon and cockpit are massive.

I totally agree that sailing is a quantum leap in attitude change - I have been doing some of it and plan to do more but seeing as in my last power boat our preferred cruising speed for comfort was 8.5 knots, its maybe not the leap for us that it may be for you /forums/images/graemlins/smile.gif

If I was motoring most of the time, which I doubt, then I would be doing so at the speed we like on a very stable platform. However that will not happen because we both understand the change and will enjoy it.

I know that because I have made so much in the fight on the red issue that many think that I am personally effected a lot by that issue - for the record I am not, my fight was very much on behalf of others and the effect that I believe it will have on the industry. I would be making this change regardless of that issue because its the best way for us to cruise world wide.

I wonder how tcm has got on with his sailing cat? I mean he has gone from a Leopard to a sailing cat!!
 
Well, all I can say is the very best of luck and I really hope that you (finally) get the boat that you want.

fwiw, I think for blue water crusing, where you are much less reliant on crowded marinas and have the whole ocean to play in a cat makes perfect sense.

If you are on board for long periods you have the space and volume you will need, plus if you have a falling out at least you can take a hull each.

As for the lightweight vs heavy weight arguement I am not an engineer, so dont know where to start but I dont think heavier always means better.
 
I'm telling you how your post appears to people who are capable of independent critical thinking. You may not like it but that;s how it comes across.

Your comparison was power monohulls and sailing monohulls. You know exactly what I was referring to and it's not a valid comparison.

I'm not insulting you or smearing. I'm highly sceptical of your assertions, which are characteristically illustrated with hyperbole, such as the false dichotomy "would you prefer to be floating in an upturned cat or in your LJ with the boat on the seabed below you".
 
It seems to be a pointless poll, you say that your boat has sunk, but only two options have sunk!
What makes you think a cat cannot sink? If you hit a large object you will sink even in a cat.
 
The fact that you think a poll (in those terms) can do anything to help your arguments is a compelling indictment of your quality of reasoning on the matter.

I was inclined to allow you the benefit of remaining agnostic (if still sceptical) about your assertions, but seeing this reinforces my scepticism.
 
Cruising cats are designed not to sink - the structure is lighter than water.

A mono sailing boat has heavy keels to counteract the sails etc and so sinks as does the power boat.

Basic to the RCD directive on sailing cats etc is the means to renter the hull when inverted.

If you hit a large object and it split open your cat it would still float.

The poll is simply to point out that cats are the best boat to have a disaster in because they float afterwards - other boats do not.

There are advantages and disadvantages to any boat type but this is an advanatge that a cat has,

You need not take my word for it - check it out is is common knowledge well documented all over the web.
 
But the weight of the keel on a sailing monohull means it cannot be stable in an inverted position so it will roll upright quite quickly. And monohulls (sailing) can be built with substantial inherent buoyancy; they may become waterlogged but won't sink. Your question presupposes there are is little between 'normal sailing' and 'disaster'.

I'm not out to get you Gludy but I know bullsh*t when I see it. For example, your assertion that a breaking wave is "mostly froth". I'm not a scientist or an engineer but I know I have read, in places more authoritative than an internet forum, that the force of one of those 'monster' waves breaking on an ocean-going ship is far beyond the design capability it's built to withstand. If you're wrong on that (and I am 99.99% sure you are), why should I believe the rest of what you have to say? Your assertions simply don't square with my (admittedly limited) knowledge. So I am sceptical.
 
øbserver
"'m not insulting you or smearing. I'm highly sceptical of your assertions, which are characteristically illustrated with hyperbole, such as the false dichotomy "would you prefer to be floating in an upturned cat or in your LJ with the boat on the seabed below you". "

But that is the stark choice.

My points made about sea anchors, waves, inverted cats are all well established facts born out of a lot of people sailing millions of miles etc.

My claims are not mine - they are basic, well established facts that you may not have nee exposed if you had no interest in Ocean sailing.


I am happy to discuss any point but you have to tell me what you disagree with.
 
Observer- thank you for posting direct points.

"But the weight of the keel on a sailing monohull means it cannot be stable in an inverted position so it will roll upright quite quickly. "

Thats a fact. Its is also a fact that it will roll like tat with about 20 per cent of the force needed to roll a cat.

A cat will stay inverted when rolled but will float. Many mono hulls sink because they fill with water and then have a greater denisty that water. MANY LOSE THEIR KEELS -THEN SINK.

"And monohulls (sailing) can be built with substantial inherent buoyancy; they may become waterlogged but won't sink."

NO TRUE - A sailing mono hull needs the weight and leverage to counter act the forces on the sail. They cannot be built light because they have a huge heavy keel to counteract the sail forces and so as a whole are heavy boats and they do sink.

"Your question presupposes there are is little between 'normal sailing' and 'disaster'."

No - in a sailing situation the mono will have its mast in the water when the cat is only 20 per cent of the way to tipping and still very level. However when the cat does go it cannot come back and will stay inverted.

My choice is a level deck of a cat - much safer.

In the case of disaster - I prefer to be floating upside down than on the bottom.

Again thank you for putting specific points that contribute to a proper discussion. /forums/images/graemlins/smile.gif
 
Magnum Posts
[ QUOTE ]
Sailing is a completly different proposition to motor boating and it requires a quantum leap in attitude change. I'd put money on you motoring rather than sailing the vast majority of the time, which begs the question, why bother?


[/ QUOTE ]
I agree

I know its not the same but I once owned a Firebird (Firebird II) in fact.
She is a high performance racing sailing cat like this:-
orion28.jpg


web page

I think at one time she was that 26th fastest ever round the Isle of Wight (not me sailing her though).

Now I know this isnt the same and very different to the kind of thing you are talking about but I think it will illustrate my point.

We used to dry sail her from Calshot and I particularly remember one day when we decided on a cruse to Lymingtom and back. This is the sort of thing you do in a mobo without thinking about it but, that day and even in perfect wind conditions, the cruise took all day - we were knackered when we got back.

My point - sailing boats take much longer to do only the simplest of trips. Dont just compare the speed - they are very dependant upon elements and at times can be much more frightening - the Firebird scared the ?hit out of me.

20 knots on the Firebird was absolutely flying - and she's a quick boat.
 
[ QUOTE ]
I'm not out to get you Gludy but I know bullsh*t when I see it. For example, your assertion that a breaking wave is "mostly froth". I'm not a scientist or an engineer but I know I have read, in places more authoritative than an internet forum, that the force of one of those 'monster' waves breaking on an ocean-going ship is far beyond the design capability it's built to withstand. If you're wrong on that (and I am 99.99% sure you are), why should I believe the rest of what you have to say? Your assertions simply don't square with my (admittedly limited) knowledge. So I am sceptical.

[/ QUOTE ]

I understand you being sceptical - I am a chartered engineer and so was I for a short while.

I can point you to may, many sources but here is one chap who has done 33,000 miles around the world in 11 years of sailing.

Link 1

Here is a simple podcast on the same subject

Podcast - voice only

After reading and listening lets discuss.
 
Hurricane
I agree with every word you have written.

Mu comments are:-
1. On a day like you had I would simply switch on the engines and motor back in a straight line at 10 knots.

2. High speed in a cat can be dangerous and the weather limits the top speed in the sense that heavy weather means you reducing the speed and even putting drogues out to slow the boat down or eventually stopping with a sea anchor.

3. Performance cruising cats go no faster in heavy weather - its all about how they perform in light weather with under 25 knots of wind.

I am not going into this blind - I have been full time learning about it and greet all incoming info with a scientific wary eye.
 
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