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  #21  
Old 14th March 2011, 03:46 PM
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Default Re: "Phaedo" Gunboat 66

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Originally Posted by dmmbruce View Post
Oh, you surprise me. I had got the firm impression from the various postings here tat these are 'trophy' assets and are definitely marina cats for show, not use...Also that they are so unsuited to cruising that it has to be a professional crew...Mike
Do we have any Gunboat owners on the forum, or any members who actually know or sailed with a Gunboat owner? Maybe I missed them, but I don't recall any posts with first hand or "hands on" experience, though it might be an interesting read.

The Gunboat 62, Looking for Elvis, definitely does/did some serious cruising. I've seen it a number of times in the Caribbean.

The couple in this article doesn't sound like they are sitting in a marina or hiring a crew to get them anywhere, either:
http://www.sailingworld.com/sailboat...y-i-gunboat-66

There was an article in one of the US sailing magazines within the last year or two of a Gunboat division in the Heineken Regatta, as well.

I agree with you on the point of the cost of a Gunboat. Some owners may even have purchased a Gunboat to charter out to help pay for them, but want a high performance "play thing" at their disposal and hire a crew to do so. However, from what I have read (in magazines like above) I get the impression that while most Gunboat owners do have a certain degree of wealth (and may have purchased them through their corporations, or created one to purchase it), they are serious sailors and use the boat to do some serious sailing.

I know if I could ever own one, I would!

Marshall
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  #22  
Old 14th March 2011, 03:46 PM
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Default Re: "Phaedo" Gunboat 66

I stand by the post concerning the fact that a BOA/LOA ratio of under 50% is not a lose/lose. You apparently know who purchased all of these boats and that none are actually used - I find that suprising (indeed, I thought I had seen Gunboats in some transat competitions). Then again, I haven't followed the ownership/crew/itinerary of all of these boats as you have (personally, I don't care much about the lives of the rich and famous). I do know that I cannot afford one!

However, if you are correct that none of them are sailed except by professional delivery crews, then I suppose one cannot find the lack of reported capsizes to be strongly supportive of their safety (although I hadn't suggested that it was). Regardless, the lack of reported capsizes can hardly be said to detract from their potential safety, regardless of who sails them. And one suspects that professional crew, in making use of some corporation's performance boat, might also tend to sail them hard.

Brad
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  #23  
Old 14th March 2011, 05:07 PM
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Default Re: "Phaedo" Gunboat 66

at least two G66's are currently circumnavigating:
http://sailmagazine.com/cruising/des...hos_yer_daddy/
and
http://seagazelle.com/
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  #24  
Old 14th March 2011, 05:41 PM
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Default Re: "Phaedo" Gunboat 66

That's interesting. Thank-you.

Mike
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  #25  
Old 14th March 2011, 06:13 PM
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Default Re: "Phaedo" Gunboat 66

very welcome - one of them is featured extensively in the current edition of Yachting World as well
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  #26  
Old 14th March 2011, 06:21 PM
Sully Sully is offline
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Default Re: "Phaedo" Gunboat 66

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Actually, I'm speaking more from a technical standpoint. The formula for catamaran stability shows that beam and weight are stability factors, and sail area and the height of sail area are capsizing factors. It's all common sense, but it's quantified in the calculation. You can make an argument that speed could be more desirable than stability, but it defies the universally-used formula to suggest that these factors don't reduce stability.
I suppose I'm questioning the merit of the "stability formula" if it includes sail area, which is a variable.

The only way the stability formula is fully applicable across all boats is if the boat doesn't have a mast up.

If the stability calculation you used took into effect the sail area, then we are talking about something that is in the control of the skipper, which was the point of my post.

Better to have a boat with a bad "stability formula" rating when the sails are completely, 100% out than to have one with a great "stability formula" where it takes a gale to get it moving.

Trust me... I've had both extremes.

My Catalac couldn't be tipped over if you tried, no matter what amount of sail area you had out. It was an extremely safe boat from the point of view of capsize. It also wouldn't go anywhere unless there was a gale.

Since sail area is variable, the "stability formula" shouldn't include it.

It's wrong to suggest there is a capsize risk on a boat that has a lot of SA/Beam/Displacement, etc... pretending as if the skipper never reefs the boat. That's an arm chair sailor's formula, IMO.

Last edited by Sully; 14th March 2011 at 06:26 PM.
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  #27  
Old 14th March 2011, 09:03 PM
44C 44C is offline
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Default Re: "Phaedo" Gunboat 66

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Originally Posted by dmmbruce View Post
Oh, you surprise me. I had got the firm impression from the various postings here tat these are 'trophy' assets and are definitely marina cats for show, not use.

The very fact that they are so expensive makes them corporate purchases rather than private, or so it has been said. Also that they are so unsuited to cruising that it has to be a professional crew to get them to the chosen marina to be tied up and used for corporate hospitality stunts.

Maybe I had got the wrong impression. However, I have not heard of one being used.

Mike
Recently saw a US registered Gunboat (a 62 I think) in Sydney harbour. AFAIK it wasn't flown in.
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  #28  
Old 14th March 2011, 09:04 PM
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Default Re: "Phaedo" Gunboat 66

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Actually, I'm speaking more from a technical standpoint. The formula for catamaran stability shows that beam and weight are stability factors, and sail area and the height of sail area are capsizing factors. It's all common sense, but it's quantified in the calculation. You can make an argument that speed could be more desirable than stability, but it defies the universally-used formula to suggest that these factors don't reduce stability.
So best not to have a mast or sails at all then?
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  #29  
Old 14th March 2011, 09:09 PM
doubledip doubledip is offline
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Default Re: "Phaedo" Gunboat 66

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So best not to have a mast or sails at all then?
And if you add well-ballasted deep keels, stability would be improved even further
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  #30  
Old 14th March 2011, 09:12 PM
dmmbruce dmmbruce is offline
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Default Re: "Phaedo" Gunboat 66

Where has that "tongue-in-cheek" icon gone?
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  #31  
Old 15th March 2011, 12:25 AM
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Default Re: "Phaedo" Gunboat 66

Relatively narrow beam is not a lose/lose however:

1. A narrower tunnel permits a lower bridgedeck clearance, which in turn lowers the CG and allows the mast to be mounted lower, lowering the CE of the sailplan.

[My BigCat 65 has the same sail area and an air draft of 69.7' for the same sail area as the Gunboat 66. Boom height is governed by the desire to have standing headroom in the hulls, and for cruising safety, a boom height above deck a bit more than a tall man. The height of center gravity of the boat has so little influence on a catamaran that is is not a factor in the stability calculations in universal use.]

2. Lighter weight permits a smaller sail area for comparable performance, again lowering the CE of the sailplan (if designed properly).

[Yet no designer makes the CE of his catamaran rig as low as is possible. The trade off is the lift to drag ratio close hauled vs. capsizing force.]

3. Lowering the ratio of BOA/LOA improves resistance to pitchpoling.

[As proven by what? I doubt accuracy of this statement, in its unlimited form. The logical conclusion of this claim is a narrow monohull.]

I note that the Gunboat has a mast clearance of 78.8 feet - quite low for a 66 foot cat that is performance oriented. I also note that the boom is quite long and that the designers have avoided the currently popular flat-top main; both tend to distribute the sail area more fore/aft and lower the CE.

[And best of all, no chafe on the backstay. Of course with unstayed masts, there are no backstays, or shrouds to chafe on. Catamaran stayed rigs with no backstay typically prevent running under the main, which I consider a big drawback in a cruising boat.]

I can't imagine that Morelli and Melvin have designed an unsafe boat (as has been suggested); indeed, the fact that no-one here has referred to instances of capsize on Gunboats (which tend to be purchased by a performance, rather than accomodation-oriented sailor) tends to support that: many of those boats are sailed 'hard'.

[I am not accountable for the limits of your imagination. It is not 'unsafe.' It is easier to capsize. The only factor that improves catamaran speed without reducing capsize resistance is hull waterline beam. Further elaboration would be a restatement of my previous posts in this thread. If you knew how to calculate the stability of a catamaran, you would know that. The formula is given at the bottom of my website, and it is found on many other catamaran design websites.]
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Last edited by BigCat; 15th March 2011 at 12:37 AM.
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  #32  
Old 15th March 2011, 12:29 AM
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Default Re: "Phaedo" Gunboat 66

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I suppose I'm questioning the merit of the "stability formula" if it includes sail area, which is a variable.
The formula includes sail area, and the height of the center of the sail area. If you put 5000 square feet of sail on your boat, don't you think it would be a lot more likely to capsize?
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  #33  
Old 15th March 2011, 12:31 AM
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Default Re: "Phaedo" Gunboat 66

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So best not to have a mast or sails at all then?
Actually, the formula is about wind capsize. In wave capsize, mast length and weigh is helpful, due to its effects on the radius of gyration of the vessel.
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  #34  
Old 15th March 2011, 12:34 AM
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Default Re: "Phaedo" Gunboat 66

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Recently saw a US registered Gunboat (a 62 I think) in Sydney harbour. AFAIK it wasn't flown in.
Obviously, you have to have millions of dollars to own one. As the rich become richer and the poor and middle class become poorer, there are more and more people who can afford a Gunboat 66. I think there have been lots of voyages in Gunboats. I drive an SUV, but I wouldn't deny that it's easier to turn one over than a sedan.
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  #35  
Old 15th March 2011, 12:36 AM
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Cool Re: "Phaedo" Gunboat 66

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That's an arm chair sailor's formula, IMO.
I done lots of blue water miles.
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  #36  
Old 15th March 2011, 02:36 PM
Southern Star Southern Star is online now
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Default Re: "Phaedo" Gunboat 66

Bigcat, we've already debated your belief that the CG is essentially irrelevant to catamaran stability - and we agree to disagree. To use one of your reductio ad absurdum arguments, go ahead and put a grand piano on the top of your steel mast(s). According to your formula, it will make no difference to transverse stability.

As to your apparent belief that flat-top mains do not raise the CE of the sailplan, again I reailize it does not fit into your formula and hence you consider it essentially irrelevant. However, the simple fact is that even where sail areas are the same, a sailplan which places the sails (or more of the sail area) higher, has a higher CE, thereby leading to increased heeling forces. Why? Something called the lever principle.

We have also been through the balance between beam and fore/aft stability and your reductio ad absurdum argument fails because there are two bows. Yes, both bows create forward bouyancy and resistance to pitchpoling. However, pitchpoling frequently occurs (especially with sail up and/or waves aft of the beam) because the lee bow buries. The further the two bows are apart, the less the contribution of the bouyancy of the windward bow to resist burying the leeward one.

Let me give you a simple example: consider two logs that are 10 feet long that have been connected together to create a catamaran. In case one, separate the logs by 16 feet; in case two, separate them by 4 feet. Now, have someone stand on the front end (the bow) of one of the logs. In case one, the front of the log is going to bury further than in case two precisely because there will be less resistance to burying the front of that log contributed by the front of the other log. In his book on cruising catamarans, Gregor Tarjan, in describing the relationship of beam to not only transverse, but fore/aft stability, has some simple diagrams showing the force vectors involved. As I recall he also quotes one naval architect who says, in essence: "when you don't know whether a boat will capsize or pitchpole first, you have about the right ratio of beam/length." Anyway, I know your formula for capsize resistance doesn't take this into consideration (but then again, if I am not mistaken, it is a formula for capszie resistance, not resistance to pitchpoling????).

Finally, it is unclear to me whether or not you agree that, all else being equal, more bridgedeck clearance is required as the width of the 'tunnel' increases? Certainly this proposition seems well accepted.

In any event, what we can agree upon is that all else being equal, a catamaran with greater beam will be more resistant to capsize. Where we apparently disagree is with respect to other factors that affect capsize resistance and, the point of my original post, that increasing beam is not always a win/win situation.

Brad
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  #37  
Old 18th March 2011, 03:22 AM
Doe818 Doe818 is offline
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Default Re: "Phaedo" Gunboat 66

I was lucky enough to spend some time on 'tribe' which is hull 6201, the first gunboat built and originally designed and built to be peter johnson's own boat for a circumnavigation. So her design was actually intended to be a one off and for cruising rather than showboating. She is used more than a large number of production cruising cats out there and certainly does not sit at a dock nor is she run only by pro crew. There is also a very close relationship between gunboat owners and the builders as well as other gunboat owners which is great to see. Peter Johnson often visits boats he has built and sails them to see how they're doing, in fact he was on tribe at the same time. I could write here all night about how good they are, but that would get old real quick. They are definately sailed slightly differently to most cruising cats, but the adjustments in one's sailing techinique are not over the top and will surprise you because they are not what you think. If anything you have to learn to let the boat do its thing because you spend way less time trying to tweak an extra knot out of them like you might normally do, lets face it, could you be bothered if you're already sailing faster than anything else already? we spent way less time trimming and messing around with tribe than we did trimming my production FP. When the wind gets up, you reef early whithout losing too much of that already awesome speed for the same reason again, could you be bothered sweating when you go real fast at reef two anyway? I bet production cruising cats would spend more time 'on the edge' of rig tolerance etc trying to get that extra knot...think charter boats...This said, you do have to have a firm hand on them or they WILL get away from you, but then any cat will do that if you're fast asleep. The forward center cockpit makes all this very easy though, I can't stress how good a sailing position that is for a cat, you really have to experience it yourself to really 'see' it and the way it blends into the saloon area which in turn blends into the aft 'cockpit' area. Its sublime. In this regard gunboat and chris white are light years ahead of everyone else. as an aside, I was highly annoyed one morning to find a gunboat sticker on the stern of my FP, planted there by 'someone' who "just wanted to make sure I know where my next boat is coming from"....if only...
Tribe was recently sold with a limited factory warranty (even though she was built in 2002!) for not a bad price at all considering what she is...lets just say a decent new and well equipped 50 footer from most reputable builders would come in at the same price...so sit tight, a gunboat may well be in all our futures one day!
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  #38  
Old 19th March 2011, 01:17 AM
Sully Sully is offline
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Default Re: "Phaedo" Gunboat 66

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Actually, the formula is about wind capsize. In wave capsize, mast length and weigh is helpful, due to its effects on the radius of gyration of the vessel.
Obviously it's about wind capsize, or it wouldn't include SA.

I'm sorry. I fail to understand your point.

If you include sail area, a prudent skipper can set this number to near zero in 60 knot winds, changing your "stability formula" completely.

So, my point is valid: If you include SA, you are, by definition, including a large variable in your stability formula.

Could you post the formula for us to discuss? I'll show you what happens when SA->0.
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  #39  
Old 19th March 2011, 01:18 AM
Sully Sully is offline
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Default Re: "Phaedo" Gunboat 66

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I done lots of blue water miles.
That wasn't a challenge to you. That's a challenge to the formula. Please post it and we can have a discussion about it.
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  #40  
Old 19th March 2011, 02:00 AM
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Default Re: "Phaedo" Gunboat 66

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That wasn't a challenge to you. That's a challenge to the formula. Please post it and we can have a discussion about it.
As I posted above, it's on my website, near the bottom. It's also in US government documents which measure catamaran stability for sailing passenger-carrying catamarans, and on Richard Wood's website, and on Derek Kelsall's website, and on Wharram's website, and no doubt elsewhere. I don't have time to teach you yacht design, and you don't seem to be a receptive student anyway. :
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