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Old 15-12-2014, 13:03   #916
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Re: The Yard Guys

Quote:
Originally Posted by Polux View Post
'Thank God we're alive!' says skipper - Yachting Monthly

Note that I am not saying by any means that the Island Pack 38 is not a seaworthy boat for his type in what regards stability. I am saying that in what regards new boats or recent used boats a mass market boat of the same price would be a much bigger boat with more stability.
From the article:
‘In the north Atlantic we experienced some of the harshest conditions known, over a period of 36 hours, with winds gusting hurricane-force 12. At 10.00hrs on 1st May 2009 the decision was made that the risk to our own personal safety was too great to continue and a rescue was co-ordinated with Falmouth Coastguard.
Force 12! They rolled three times, came out alive. The sea anchor broke away. I would hope my boat could do that. On second thought, I wouldn't want to be out there to test if it could.

Quote:
Regarding the actual catalog from Island Packet the IP37 would be the equivalent boat. The IP 37 has a Loa of 37'10'' but a LWL of only 31'0', costs USD 429 950 about the same price of a Jeanneau 50DS that has a LOA of 49'5'' and a LWL of 43'0''.

The 50ft Jeanneau will have a much bigger stability and will be muck more difficult to knock down or roll then the similar priced Island Packet 37.

All small boats (meaning small yachts till 70ft or so) can be rolled, given the circumstances, but the ones with more stability (and that is connected with size) will be generally harder to capsize then the smaller ones.

That's just what I wanted to point out regarding a discussion about bluewater boats, where the money one has for a boat is an important part of the equation. The ones that don't have limits on a budget for a boat are very few, normally there is a limited budget and for one that wants a new boat the budget for a IP37 is similar to the one for a 50ft Jeanneau.
Perhaps you have access to information I don't, however, I ran the numbers as listed in sailboatdata.com through Sail Calculator Pro v3.54 - 2800+ boats
and the story they appear to tell differs from what you wrote above. I understand the limitations of that calculator that you have expressed before, but not having access to the stability curves, it is the best I have to go on. Please provide us with additional information, if you have it.

You are comparing two boats that are 12 feet different in lengths. The IP has a capsize ratio of 1.82, versus the DS of 1.9. The motion comfort calculations is for the IP is 32.46, versus 28 for the DS. Higher is better.

Based on that information (screen shots attached), one could not agree with your statement that the DS is superior in stability.

Perhaps you could give us more data than we have available? One of us will have to adjust our perspectives I would think. I am always glad to accept new, and better information, as one should be careful about making generalizations that bigger is always better.

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Old 15-12-2014, 13:38   #917
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Re: The Yard Guys

Quote:
Originally Posted by avb3 View Post
From the article:
‘In the north Atlantic we experienced some of the harshest conditions known, over a period of 36 hours, with winds gusting hurricane-force 12. At 10.00hrs on 1st May 2009 the decision was made that the risk to our own personal safety was too great to continue and a rescue was co-ordinated with Falmouth Coastguard.
Force 12! They rolled three times, came out alive. The sea anchor broke away. I would hope my boat could do that. On second thought, I wouldn't want to be out there to test if it could.

Perhaps you have access to information I don't, however, I ran the numbers as listed in sailboatdata.com through Sail Calculator Pro v3.54 - 2800+ boats
and the story they appear to tell differs from what you wrote above. I understand the limitations of that calculator that you have expressed before, but not having access to the stability curves, it is the best I have to go on. Please provide us with additional information, if you have it.

You are comparing two boats that are 12 feet different in lengths. The IP has a capsize ratio of 1.82, versus the DS of 1.9. The motion comfort calculations is for the IP is 32.46, versus 28 for the DS. Higher is better.

Based on that information (screen shots attached), one could not agree with your statement that the DS is superior in stability.

Perhaps you could give us more data than we have available? One of us will have to adjust our perspectives I would think. I am always glad to accept new, and better information, as one should be careful about making generalizations that bigger is always better.
That is just a bit crazy. I believe you are saying what yo say in good faith but let me tell you that the best you have to do is throw away that calculator.

I, or anybody that understands the basis of boat stability will know instantly that it will be needed much more energy, read a bigger breaking wave, to capsize a Jeanneau 50 DS than a a IP 37. The energy needed will be equal to the total amount of positive stability that equals the area under the positive part of a RM curve. A RM curve is obtained multiplying all values from a GZ curve (arm values) by the weight of the boat.

The GZ curve from the Jeanneau 50DS will have bigger arm values due to the much bigger beam of the boat and to the lower CG due to a bigger draft and the ballast more deeply situated. The weight of the IP 37 is considerably smaller than the weight of Jeanneau 50DS (23 800lbs to 29542lbs).

The values that will result from the product of the bigger Jeanneau weight for the bigger Jeanneau arm will be obviously much bigger as the stability from the Jeanneau compared with that of the IP. I am not making up and I do not have interest in taking this further or determinate how more stability will have the Jeanneau over the IP, so please try to understand what I am saying.
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Old 15-12-2014, 13:46   #918
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Re: The Yard Guys

We've discussed this incident before, and we have no real information on the actual experience of these guys... but, this is one of the most telling parts of the story:

Quote:
The yacht had left Plymouth as part of an expedition to Greenland under the flag of the ‘Carbon Neutral Expedition’. After the planned arrival in Greenland, Ben’s two crew – Raoul (40) a landscape gardner from Jersey, and Richard (31) a physiotherapist from Bristol – had planned to cross the Greenland ice cap.
Was this another case of "just buy a 'bluewater boat' and you'll be fine"?

More here:
BBC NEWS | UK | England | Eco-sailors rescued by oil tanker

Quote:
The team, which left Mount Batten Marina in Plymouth on 19 April in a boat named the Fleur, aimed to rely on sail, solar and man power on a journey to and from the highest point of the Greenland ice cap.

The expedition was followed by up to 40 schools across the UK to promote climate change awareness.
And here:
http://www.bristolpost.co.uk/Bristol...ail/story.html

Quote:
In an ironic twist their rescuer – a 113,000-ton tanker called Overseas Yellowstone, carrying 680,000 barrels of crude oil – had to make a detour of an estimated 50 nautical miles to pick them up, pumping out an estimated extra 54.2 tonnes of CO2 into the atmosphere in the process.
"Comfort factor" turned ironic environmental harm.
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Old 15-12-2014, 14:47   #919
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Re: The Yard Guys

You are comparing a small Ip with a 50 FT Jeaneau, good job!! why you dont take a size by size Ip v Jeaneau? By the way F12 is Hurricane forcé winds, what do you expect?
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Old 15-12-2014, 15:09   #920
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Re: The Yard Guys

Quote:
Originally Posted by Polux View Post
That is just a bit crazy. I believe you are saying what yo say in good faith but let me tell you that the best you have to do is throw away that calculator.

I, or anybody that understands the basis of boat stability will know instantly that it will be needed much more energy, read a bigger breaking wave, to capsize a Jeanneau 50 DS than a a IP 37. The energy needed will be equal to the total amount of positive stability that equals the area under the positive part of a RM curve. A RM curve is obtained multiplying all values from a GZ curve (arm values) by the weight of the boat.

The GZ curve from the Jeanneau 50DS will have bigger arm values due to the much bigger beam of the boat and to the lower CG due to a bigger draft and the ballast more deeply situated. The weight of the IP 37 is considerably smaller than the weight of Jeanneau 50DS (23 800lbs to 29542lbs).

The values that will result from the product of the bigger Jeanneau weight for the bigger Jeanneau arm will be obviously much bigger as the stability from the Jeanneau compared with that of the IP. I am not making up and I do not have interest in taking this further or determinate how more stability will have the Jeanneau over the IP, so please try to understand what I am saying.
So your suggesting that the better numbers indicated by the information available to us is not representative of what one can expect?

I'm one of those "show me" individuals. I gladly take new information and assess my conclusions based on that. However, a "trust me, I just know" doesn't work well with many, including me, if bona fides have not previously been established.

Bigger is NOT better, nor more stable, just because it is bigger. A Nor'sea 27, a Flicka 20 or a Nebe Cape 28 will run circles around many much bigger boats from a stability point of view, which I am sure you're aware of. They will also be able to handle bad conditions better than many.

So perhaps you can point us at some empirical evidence to back up your generalization that the IP 38 is not as stable a boat as the DS 50. Any information I presented and that is available seems to indicate otherwise.

Remember, 'just trust me' needs to be substantiated in some way, don't you think?
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Old 15-12-2014, 15:30   #921
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Re: The Yard Guys

Just for fun.

BENETEAU 50 AVS 109 STIX 41

BAVARIA 42 STIX 36

BENETEAU 50 STIX 41

BENETEAU 57 STIX 53

CATALINA 34 MK11 STIX 36

CATALINA 42 40 AVS 105

COMET 36 STIX 32.5 AVS 127

CONTESSA 32 STIX 33 AVS 155

CYCLADES 39 STIX 38 AVS 126

CYCLADES 43 STIX 36 AVS 121

DISCOVERY 55 STIX 37 AVS 122

ELAN 37 STIX 40 AVS 136

ELAN 40 STIX 37 AVS 128

ELAN 44 STIX AVS 124

ETAP 32 STIX 36 AVS 122

ETAP 34 STIX 37 AVS 123

ETAP 37 STIX 42 AVS 123

FIRST 36.7 STIX 34 AVS 126

FIRST 40.7 STIX 37 AVS 126

FIRST 42.7 STIX 35 AVS 118

FIRST 44.7 STIX 41 AVS 130

FIRST 47.7 STIX 46 AVS 123

FISHER 34 STIX 33 AVS 180

FISHER 37 STIX 43 AVS 180

HANSE 371 STIX 35 AVS 122

HANSE 411 STIX 33 AVS 128

HANSE 461 STIX 35

HANSE 531 STIX 39

HARLEY REFLEX 38 STIX 41 AVS 143

HOD 35 STIX 41 AVS 140

HUNTER CHANNEL 31 (single keel) STIX 32 AVS 130

HUNTER CHANNEL 31 (twin keel) STIX 33 AVS 130

HUNTER CHANNEL 323 STIX 35 AVS 149

ISLAND PACKET 350 STIX 49 AVS 141

ISLAND PACKET 370 STIX 43

ISLAND PACKET 380 STIX 55 AVS 136

ISLAND PACKET 420 STIX 59 AVS 136

ISLAND PACKET 440 STIX 48 AVS 133

ISLAND PACKET 445 STIX 53 AVS 141

ISLAND PACKET 485 STIX 66 AVS 143

J12O STIX 43 AVS 127

J100 STIX 37 AVS 126

J125 STIX 42 AVS 131

J133 STIX 46 AVS 130

J145 STIX 52 AVS 139

J160 STIX 57 AVS 118

J42 STIX 45

J46 STIX 48 AVS 127

MALO 45 STIX 62

MISTERY 35 STIX 32 AVS 156

NAJAD 380 STIX 43 AVS 128

OCEANIS 343 STIX 34 AVS 134

OCEANIS 351 STIX 35 AVS 125

OCEANIS 361 STIX 32 AVS 120

OCEANIS 36CC STIX 35 AVS 126

OCEANIS 373 STIX 36 AVS 132

OCEANIS 381 STIX 38 AVS 130

OCEANIS 393 STIX 43

OCEANIS 411 STIX 37 AVS 114

OCEANIS 423 STIX 38 AVS 119

OCEANIS 44CC STIX 34 AVS 110

OCEANIS 461 STIX 37 AVS 115

OCEANIS 473 STIX 48 AVS 119

OCEANIS 523 STIX 46 AVS 111

OCEANIS 42CC STIX 38 AVS 38

SEAQUEST 32 STIX 37 AVS 132

SEAQUEST 36 STIX 46 AVS 142

SEAQUEST PRIMA 38 STIX 52 AVS 131

SOUTHERLY 110 STIX 55 AVS 151

SOUTHERLY 115 STIX 51 AVS 150

SOUTHERLY 35RS STIX 37 AVS 160

SOUTHERLY 135 STIX 54 AVS 139

SUN ODYSSEY 37 STIX 33

SUN ODYSSEY 39i STIX 33

SUN ODYSSEY 40DS STIX 37/39

SUN ODYSSEY 40.3 STIX 36/38

SUN ODYSSEY 43/43DS STIX 44

SUN ODYSSEY 52.2 STIX 50

SUNFAST 35 STIX 33 AVS 127

SUNFAST 37 STIX 32

SWAN 40 STIX 36 AVS 112

SWAN 44 STIX 38 AVS 123

SWAN 45 STIX 57 AVS 134

SWAN 46 STIX 53 AVS 128

SWAN 48 CR/R STIX 49 AVS 135

SWAN 56 R STIX 50 AVS 127

SWAN 56 R/C STIX 55 AVS 124

SWAN 57 RS STIX 53 AVS 132

SWAN 60 R STIX 68 AVS 128

SWAN 60 R/C STIX 70 AVS 122

SWAN 601 STIX 84 AVS 153

SWAN 62 STIX 63 AVS 122

SWAN 68 R STIX 76 AVS 127

SWAN 70 STIX 82 AVS 133

SWAN 75 R STIX 81 AVS 121

SWAN 80 R STIX 80 AVS 138


SWAN 82 R ST

HOD 35 OD2,2241140AHUNTER 7071,4817121CHUNTER PILOT 27FIN KEEL28144BHUNTER PILOT 27 B/KTWIN KEEL25139BIMX 402,4447132AIMX 452,8646124AISLAND PACKET 38055136AISLAND PACKET 42059136AJ 1001,7537126AJ 1051,9833120AJ 1092,133121AJ 111 2.20 EUEU2,2134140AJ 111 2.20 USUS2,244143AJ 1202,1343127AJ 120 S/DShallow draft1,843127AJ 1222,241129AJ 1242,1644130AJ 1252,4842131AJ 1332,2946130AJ 1452,7252139AJ 145CShallow Draft2,2950125AJ 1602,1557118AJ 321,8333133AJ 35 2.102,133120AJ 42 & J 42 D/DNormal & D/D Version2,0345120AJ 46Normal Version2,3548127AJ 46 S/DS/D Version1,9348127AJ 801,4923123BJ 921,7931129BJ 92S1,931129BJ 9527116BJ 9737134AJ.P.K. 110 (?) NOT 101044137AJ.P.K. 9.601,9535132AJOD 35No water ballast1,9533129AJOD 35With 500kg water ballast1,9531119BJUDEL/VROLIJK 52YOUTH TRAINING YACHT3,4662140AKER 11.3 OD2,3746149AKER 40 2.60OD2,643139AKNIERIM 49345134AKnierim 533,265130ALANDMARK 432,860152AM 342,541142AMARTEN 493,6456144AMAT 1010 2.102,138143AMAT 122,5551147AMAX FUN 352,232127AMELGES 24 OD1,5215130CMoody 38S1,533118AMOODY 5641120AMUSTANG Mk2MK 21,7124134BMYSTERY 35DEEP KEEL1,8132156ANAUTINER 3027125BNissen 562,9643117AOCEANIS 28125117BOCEANIS 311STANDARD27118BOCEANIS 311 D/KLIFT KEEL26123BOCEANIS 32133110AOCEANIS 323ALL26119BOCEANIS 331LIFT KEEL-ORIGINAL28116BOCEANIS 331LIFT KEEL - NEW32AOCEANIS 331 & CLIPPERBULB KEEL31125AOCEANIS 343ALL34134AOCEANIS 35135125AOCEANIS 36132120AOCEANIS 36CCCC35126AOCEANIS 373 D/DDEEP KEEL1,8536132AOCEANIS 373 S/DSHALLOW KEEL1,4536132AOCEANIS 38138130AOCEANIS 3931,943AOCEANIS 393 S/D1,543AOCEANIS 40 1.951,9536119AOceanis 40 1.951,9536119AOCEANIS 40 CC38112AOCEANIS 41137114AOCEANIS 42 CC38120AOCEANIS 42338119AOCEANIS 44CC W/KWING KEEL1,834110AOceanis 462,0540119AOCEANIS 4611,7537115AOCEANIS 47348119AOCEANIS 523 D/DDEEP KEEL2,346111AOCEANIS 523 S/DSHALLOW KEEL1,846111AOCEANIS CLIPPER 42CC(GTE)38120AOYSTER 4933118APACER CLUB 42Deep Draft2,550133APLATU 2517121CPOGO 10.502,836124APOGO 8.501,7535121BPRIMA 38 OD2,4652131APRONAVIA 382,344139APRONAVIA 42 SportSPORT2,6353150ARANGER 245FIN26140BRANGER 245 B/KTWIN KEEL25139BRANGER 265FIN28146BRANGER 265 B/KTWIN KEEL26139BREFLEX 281,7426132BREFLEX 382,341143AROGERS IRC 46 (06)2,8756149ARUSTLER 3637147ARUSTLER 4241123ASALONA 42 2.252,2535123ASALONA 42 2.50IBC2,544125ASANTA CRUZ 372,341145ASEAQUEST 32237132ASEAQUEST 36NOT RP 362,2646142ASEAQUEST RP 362,2542138ASIGMA 331,8324117BSIGMA 382,0829116BSinergia 412.402,437120ASJ 3201,9737132ASNAPPER 241,5223136CSOUTHERLY 1102,1850144ASOUTHERLY 115Series 251150ASOUTHERLY 13553131ASOUTHERLY 35 RS37160ASOUTHERLY 42RS40119ASUMMIT 40 KING 2.512,5154152ASUN FAST 32001,938138ASun Fast 32i1,9832131ASUN FAST 352,1534131ASun Fast 372,0732122ASUN ODYSSEY 36i Performance2,135131ASun Odyssey 39i234119ASUN ODYSSEY 401,9538122ASUN ODYSSEY 45 DS2,0535101ASUN ODYSSEY 52.21,839115ASWAN 100104130ASWAN 112 RS84110ASWAN 36 (67)S&S1,8933145ASWAN 36 (88)Frers2,1533115ASWAN 371,9632140ASWAN 3712,134119ASWAN 38 T/R2,0233115ASWAN 3912,2528110BSWAN 40S & S2,0536112ASWAN 40 (92)Frers2,1632112ASWAN 412,1132122ASWAN 4112,2132120ASWAN 422,4427107BSWAN 43 (69)S&S2,1539121ASWAN 43 (85)Holland2,5333113ASWAN 44 (72)S&S2,3236123ASWAN 44 Mk2MK 22,238123ASWAN 4412,432116ASWAN 45 OD2,8157134ASWAN 462,538111ASWAN 46 (04)STANDARD KEEL2,351128ASWAN 46 (04) DaggerboardDAGGERBOARD/TWIN RUDDER49121ASWAN 46 C/BCENTER BOARD32109ASWAN 46 Mk239114,2ASWAN 47FIXED KEEL49133ASWAN 48 (72)2,445128ASWAN 48CRCRUISER/RACER2,449135ASWAN 48CR2,949135ASWAN 48RREGATTA2,9449135ASWAN 512,736114ASWAN 533,141114ASWAN 5312,4452117ASWAN 56 CR 2.70CRUISER/RACER2,755124ASWAN 56 CR 3.40CRUISER/RACER3,455124ASWAN 56 RREGATTA3,450127ASWAN 572,847120ASWAN 57 RS53132ASWAN 60 CRCRUISER/RACER70122ASWAN 60 RREGATTA3,568128ASWAN 6013,6184153ASWAN 62 & RS63122ASWAN 652,9855123ASWAN 65161121ASWAN 683,5476127ASWAN 70482133ASWAN 7581121ASWAN 804,380138ASWAN 8288127ASWAN 8663114ASWAN NY/CLUB 422,7Sweden Yachts 422,139123ASYDNEY 462,8543127ATANGO 30FIXED KEEL35134ATIDE 2829135BVANCOUVER 2836170AVANCOUVER 34CLASSIC1,4636139AVQ 32UP TO 350KG WATER BALLAST41140AVQ 32No water ballast2,142149AWARRIOR 4047133AWESTERLY OCEAN 4340129AX 3321.80m draft only1,831119AX 341,8939135AX 35One Design2,1533123AX 37& Sports1,9834120AX 37 Sport2,3234120AX 402,141127AX 40 Sport2,438124AX 412,543127AX 43 2.20(shoal draft)2,240121AX 43 2.502,540121AX 4422,332110AX 46 2.40Standard draft2,444123AX 46 2.70Deep draft2,744123AX 4822,532108AX 50346123AX 553,254124AX 562 M/HM/H2,8557122AX 6123,251110AX 65 3.00365118AX 65 3.403,469121AX 705,3773126AX 7384121AXc 3835111AXc 42Standard (not shallow draft)2,137111AXc 45Standard2,240113AXc 45 S/DShallow draft38112AXc 5044113AXp 33 1.901,935135AXp 38 2.102,148144AXp 38 2.402,446144AXp 44 2.302,347126AXp 44 2.652,6549128A
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Old 15-12-2014, 15:32   #922
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Re: The Yard Guys

Quote:
Originally Posted by neilpride View Post
You are comparing a small Ip with a 50 FT Jeaneau, good job!! why you dont take a size by size Ip v Jeaneau? By the way F12 is Hurricane forcé winds, what do you expect?
Polux seems to be making the point that for the money you'd spend buying a 37' IP you could buy a 50' Bene, & thus a more "stable" boat. Not sure how this advances the debate, but I've already been thinking that for awhile now.

And yes, hurricane-force 12 conditions, three knockdowns, a failed attempt at a sea anchor, and the cap knocked on the head before calling for help. And once again, bald speculation but absolutely no evidence that the bluewater rep of the IP made the cap & crew overconfident about undertaking the voyage. As avb3 suggested, it could be a testament to the "bluewater" characteristics of the boat that the crew survived at all in conditions like this. Either way, might be more relevant to the debate to figure how a similarly-sized, lightweight production boat might have done. Smack will tell us, I'm sure, but we already know he's never experienced conditions even close to this on his beloved Hunter.

As Neil has commented, the "repairs" & "maintenance" that occasioned the bottom job on the Oyster looked to be part of the routine prep that anyone who has either done his/her own bottom job, observed others being done, or has done some research would recognize. That Smack appears to be the only who failed to recognize this necessarily answers avb3's question about his lack of any experience in this area too.

I'm starting to come around to Minaret's comment that the intent of posts like these is to instigate vs. inform. Probably works better on SA vs. CF.
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Old 15-12-2014, 15:40   #923
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Re: The Yard Guys

Yeah, i notice that, Pólux love numbers and data, thats why is going to be busy for a while trying to figúrate the algorithm up there, how much cost a DS 50? Im sure for that money i can found something better. my 2 cents..
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Old 15-12-2014, 16:05   #924
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Re: The Yard Guys

Anyone notice the stix and avs from a Contessa 32, without multi wide beam chine hull form doublé Wheel polipop!!!

1979 fasnet disaster ,the only yacht in the small boat class to finish the disastrous 1979 Fasnet race.
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Old 15-12-2014, 16:27   #925
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Re: The Yard Guys

Quote:
Originally Posted by neilpride View Post
Anyone notice the stix and avs from a Contessa 32, without multi wide beam chine hull form doublé Wheel polipop!!!

1979 fasnet disaster ,the only yacht in the small boat class to finish the disastrous 1979 Fasnet race.
OK, I'm sure there are others who don't know what the stix & avs values mean, but I'm willing to reveal my ignorance for the sake of learning something. The only data I've seen in this regard pertains to how quickly a boat will right itself after being knocked down to 90 degs. Is this the stability index or "stix"? Does "avs" pertain instead to how easily a boat can be knocked down?

That Contessa 32 is a beauty. Always heard good things about those boats. But they're old -- best check the rudder!
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Old 15-12-2014, 17:04   #926
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Re: The Yard Guys

Quote:
Originally Posted by Exile View Post
OK, I'm sure there are others who don't know what the stix & avs values mean, but I'm willing to reveal my ignorance for the sake of learning something. The only data I've seen in this regard pertains to how quickly a boat will right itself after being knocked down to 90 degs. Is this the stability index or "stix"? Does "avs" pertain instead to how easily a boat can be knocked down?

That Contessa 32 is a beauty. Always heard good things about those boats. But they're old -- best check the rudder!
STIX is a stability index, the higher the number the better, AVS is the angle of vanishing stability.



To get the STIX of a certain model they need the overall measures of the boat, beam , lenght, etc..and the righting arm curve GZ.


Im sure Contessas Owners keep teir rudders in good condition, after all is kind of a cult boat, but yes why not , check your rudders!!!!
Im just checking Contessas in the net, overall they are well maintained..

BTW Exile, im not a expert in this matter, but what you say about how quickly a boat will right itself after being knocked down to 90 degs enter in the STIX equation to.
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Old 15-12-2014, 18:11   #927
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Re: The Yard Guys

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Originally Posted by neilpride View Post
Just for fun.
....

ISLAND PACKET 380 STIX 55 AVS 136
...
ISLAND PACKET 440 STIX 48 AVS 133

ISLAND PACKET 445 STIX 53 AVS 141
..
...
What is the fun of posting about something you don't understand. we have already saw that you cannot understand rat language.

Do you know how the STIX is calculated? It has a direct relation with what I has talking about, meaning the energy needed to capsize a boat?

The Island Packet 445 and the Island Packet 440 have a STIX number smaller than the Island Packet 380. Do you really think that the energy needed to capsize the 380 is bigger than the energy to capsize the Island Packet 445? That the 380 has an overall bigger stability then the 445

You should not post about things you don't understand.
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Old 15-12-2014, 18:15   #928
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Re: The Yard Guys

Easy Pol, chill, im just posting what some NA are explaining in the net, they are not my words, so , you see, if you want i bring you the links to see with your own eyes that im not saying nothing weird, its in fact NA words. Now go ahead, where is the SD 50 avs, mr i know all!!!
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Old 15-12-2014, 18:28   #929
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Re: The Yard Guys

Quote:
Originally Posted by neilpride View Post
STIX is a stability index, the higher the number the better, AVS is the angle of vanishing stability.



To get the STIX of a certain model they need the overall measures of the boat, beam , lenght, etc..and the righting arm curve GZ.


Im sure Contessas Owners keep teir rudders in good condition, after all is kind of a cult boat, but yes why not , check your rudders!!!!
Im just checking Contessas in the net, overall they are well maintained..

BTW Exile, im not a expert in this matter, but what you say about how quickly a boat will right itself after being knocked down to 90 degs enter in the STIX equation to.
Thanks Neil!

More info here:

Sailboat Design Categories for Ocean, Offshore, Inshore and Sheltered Waters

Note the distinction made b'twn "A" for "Ocean" and "B" for "Offshore." Not just based on tankage as some have earlier argued. Primary factors are STIX & AVS.

And here:

How Gz Curves Reveal the Truth about A Sailboat's Stability

Many factors including righting moment, but seaworthiness is essentially defined as resistance to capsize.

As for rudders, this thread has me paranoid! All I (think I) know is that a solid bronze rudder stock won't be subject to crevice corrosion but may be susceptible to friction & wear if the bearings/bushings go bad (like steering pulley pins). Hopefully this would result in noticeable play when inspecting on the hard. But a SS stock could be subject to crevice corrosion & may not be detectable w/o dropping the rudder. Is any of this correct?

And then there are the couple of hollow SS stocks I've seen at the yard on inexpensive boats that have busted, probably after hitting something but who knows? Of course, this is not because hollowed-out SS is cheaper to produce, right? Must be to make the boat lighter & thus enhance performance.

I'm off to check out Contessa's . . . .
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Old 15-12-2014, 18:43   #930
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Re: The Yard Guys

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Originally Posted by avb3 View Post
So your suggesting that the better numbers indicated by the information available to us is not representative of what one can expect?
No, you can have correct information. The only way to have precise results is to get a stability curve from the IP 38 and the Jeanneau 50S and compare the energy needed to capsize both boats, but has I have explained the difference in stability is so evident that it is not necessary to have them to know that the overall stability of a Jeanneau 50 is considerably bigger than the one of a IP38.

What is the information you have, the one you posted, the so called capsize ratio? it has been explained to you by several members that does only work relatively to similarly design boats of a given era, old boats. And even so you don't seem to realize that even in what regards those boats it is a relative number.
The formula is a very simple one: = Beam /(Displacement / 64)1/3
and will not differentiate between a 100ft boat or a 20ft boat. It will give you for that design a ratio. It can give you for a 20ft boat a much better ratio than for a 100ft boat. Do you really believe the 100ft boat will be easier to capsize than the 20ft boat? Is that what you call "the information available to us"?

Quote:
Originally Posted by avb3 View Post
Bigger is NOT better, nor more stable, just because it is bigger. A Nor'sea 27, a Flicka 20 or a Nebe Cape 28 will run circles around many much bigger boats from a stability point of view, which I am sure you're aware of.
How big do you mean? I have already explained that you get a righting moment when you multiply the weight of the boat by the GZ and that all RM at all angles of heel till the AVS are a measure of the boat stability (the area below the positive part of a RM stability curve).

I have already explained on this or on the thread about rudders how you get the GZ (arm) for each angle of heel.

Heavier boats can have a better overall stability then slightly bigger lighter boats...but when a boat is substantially bigger and is also heavier, if it is well designed, no way it will have lesser overall stability than the smaller boat, meaning by overall stability the energy required to capsize the boat. It is impossible.

If you do not understand these basic concepts I can point you to several sites that, with some work, can give you the basics regarding boat stability.

Quote:
Originally Posted by avb3 View Post
So perhaps you can point us at some empirical evidence to back up your generalization that the IP 38 is not as stable a boat as the DS 50. Any information I presented and that is available seems to indicate otherwise.
Remember, 'just trust me' needs to be substantiated in some way, don't you think?
I have already told you, but you have to understand the meaning of what I said.

Quote:
Originally Posted by Polux View Post
..

I, or anybody that understands the basis of boat stability will know instantly that it will be needed much more energy, read a bigger breaking wave, to capsize a Jeanneau 50 DS than a a IP 37. The energy needed will be equal to the total amount of positive stability that equals the area under the positive part of a RM curve. A RM curve is obtained multiplying all values from a GZ curve (arm values) by the weight of the boat.

The GZ curve from the Jeanneau 50DS will have bigger arm values due to the much bigger beam of the boat and to the lower CG due to a bigger draft and the ballast more deeply situated. The weight of the IP 37 is considerably smaller than the weight of Jeanneau 50DS (23 800lbs to 29542lbs).

The values that will result from the product of the bigger Jeanneau weight for the bigger Jeanneau arm will be obviously much bigger as the stability from the Jeanneau compared with that of the IP....
This is evident if you understand the basis.
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