Sailing boats' Stability, STIX and Old Ratios

[Guillermo]

Originally Posted by Claus Riepe

Guillermo:
No need to be confused.
Just take it that 'Greater than' means exactly that, 'greater than'.
Greater than -say- 7.200 sq mmtrs. means any opening GREATER than 7.200 sq mmtrs..
Not -as you surmise-SMALLER than 7.200.

Why do you think 6.4.8 applies for 'small openings' only? The opposite is true.

Claus

Claus, I don't follow you. I DID NOT say 'smaller', but 'greater' Please read again carefully. And if you take the care of working down numbers, you'll find that a 96 mm diameter opening has a GREATER area than 7200 mm2 (7238 mm2, to be precise. And two 68 mm dia. ones totalize 7263 mm2).
And those are small openings, in my opinion, the type of a deck mushroom vent which's watertightness degree doesn't fulfill level 3 requirements.
My understanding is that Φda1 is conceived for such types of openings. There's something similar at the rules for the openings of outboards' cables in outboard wells. But now I'm at home and do not have ISO book with me. On monday I'll check and post. I'll also check ISO 12216, were I think I'll find some extra support to this.
Cheers.

[Vega]

Originally Posted by Guillermo

Not so. I consider irrespetuous people who when somebody disagrees with them (like you've done) say things as: “You don't know what you're talking about”, “you are not being honest”, "you really don’t know much about sailingboats", "you utilize fallacious arguments", "you need to be always right" and the like.....Quite respetuous indeed!

Sorry not having replied more promptly, as I should, because what you are doing is not right.

Originally Posted by Guillermo

… because several times you have contradicted my posts as if I were not knowing what I'm talking about. …. What is annoying is to cheat professionals with irrespetuous statements like I understand you've done in several occasions…
I would appreciate very much you being more polite when discussing…

You say that I have done that on other occasions, (I mean, contradicted and being "irrespetuous" to you), but obviously you are mainly saying that I have done it in this thread, otherwise it would not make any sense to say this in this thread.

To show that I have been “irrespetous” (disrespectful ?) to you in this thread, you seem to think that it is right to quote a serial of out of contest quotations from another thread, without any information of that fact, inducing that way, people to think that I have said those things in this thread.

Well maybe it is right by your rules of conduct, not by mine.

I will post the entire post where I have said those “irrespetous” things to you (the quotations you make).

I feel it is necessary, because it is the only way to put those quotations of mine in contest, and let people see what they really mean. Certainly I was not trying to insult you, only saying what I thought it was true, and explaining why.

Originally Posted by Vega

Well I was hopping that you were mistaken in that weight...and I was diplomatically waiting for you to correct...but no, it seems that you are really talking about an old 50ft, 10 T cruising sail boat.

It can only mean two things: Or you honestly don’t know of what kind of boat you are talking about or you know and then you are not being honest in this comparison.

About the Beneteau:

Anyway you are not being honest when you say that the Beneteau 50 "is a...good performer in their time”. Or perhaps you really don’t know that the Beneteau Oceanis 50 is the floating condo from Beneteau, a slow boat in the Benetau range. And even so your numbers are not right, the boat weighs only 13T ( this is the light weight boat, but I believe the 10T of the other boat is also a light weight) and has some more sail than the one you have considered ( instead of 105, it has 115.8).

http://www.beneteau.com/ressource/do...s50_230606.pdf

The only 50 ft Beneteau that can be considered a “... good performers in their time” is the new First 50. This one will displace 12.8T for 138.7 m2 of sail.

http://www.naucat.com/katalog/repDetalj.asp?id=1293

Of course, has this it a new boat, you can consider the older boat, the one this one replaces, the First 47.7, that has a displacement of 11.5T and 120 m2 of sail Area.
http://www.beneteauusa.com/sail/prev.../477_intro.php


The Luders 50ft/10T:

Alfred Luders was a good naval Architect who has made racing boats and cruising boats. HIs most famous boat is American Eagle, a racing 12 mR that was the Americans cup challenger in 1964. The boat was modified for ocean racing by Ted Brewer and has won a lot of races, including the 1972 Sydney-Hobart.

http://www.americascupcharters.com/us21.htm

His most known cruising yachts were the Sea Sprite series.
http://www.seasprites.com/BoatsFrame.htm

A 50ft Luders with 10T can only be a racing boat. I have doubts that you can call that a cruiser-racer, (the boat you have posted is racing), and I seriously doubt that that boat has only 10T.

Typically, racing extreme boats of that time (60’s) with around 15m were the 8mR class boats, a kind of scaled down America cup boat (the 12mR class).

A typical boat of that class, probably from the same time of that 50ft Luders is the Olin Sthephens designed 8m Racing sailboat Iroquois, a 1967 boat with 14M, displacing 9.5T with a beam of 2.4 a draft of 2.0. They don’t say the sail area, but typically in the 8mR class, it is between 75 and 80 m2. This boat is a very competitive one and has won the 1984 8mR cup in Norway and the 1985 Sweden cup.

If a truly fast, 46ft top of the range, racing boat of that time displaced 9.5T, how do you think it is possible a 50ft cruising boat to displace only 10T?

These boats were so beautiful and gave so much fun that the class still exists, with new boats competing against old boats.

Even today, using modern building techniques (cold molded mahogany and epoxy vacuum techniques) it is only possible to make a 8m Racing class boat with 8.2T, like the Spazzo, (2000 world cup winner with a LOA of 13,4 m carrying 82m2 of sail) .

http://www.spazzo.de/specs.html

It is just not possible to have a wooden 50ft cruising boat in the sixties with 10T.

Of course that boat you have posted looks like a racing boat (and it is racing in the photo) and even so, comparing its appearance with the one of a 8mR class boat, I would say that it must have more than 10T.

Only you, Guillermo, would try to compare a racing design from the sixties with a relatively slow fat condo from nowadays to see how they compare in their light wind performances saying :

“Just to compare old and new boats:
Fisrt, let's compare boats with similar overall length and recognized as reasonably good performers in their time.”

How about to compare 50ft modern fast cruising boats with old fast cruising boats and 50ft modern race boats with old fast race boats?

Here you have my contribution: This is a good fast old 50ft cruiser (Luders designed) sailboat with 13 T. They don’t say the sail area but in that time a cruiser had relatively small sails, by modern standards.

http://www.yachtshare.com/boats-for-...07_50_4604.pdf

Guillermo, I like boats and I like to discuss boats, but I don’t like pointless arguments nor I discuss to win or lose an argument, just to learn and to share what I know.

Obviously it is not your case. It is not the first time you utilize fallacious arguments to prove your point even if they make no sense at all (comparing an old racing boat with a modern slow cruising boat, regarding light winds performance).

I don’t know if you need to be always right or if you really don’t know much about sailingboats. For one that can go so low on devious arguments, you assume many times a patronizing tone, like in the post 63, while you say things that have no sense at all, like this:

It depends on the type of hulls Guillermo ...

Then in a 8mRacing 47ft boat (like the one posted) with a beam of only 2.5m and very little form stability, do we assume that it must have a very limited sail carrying capacity (initial stability)?

How the hell do you think it gets the initial stability to carry 93 m2 of sail? Certainly not in its form stability, but in its low center of gravity.

Please, Guillermo, try to be a little more modest and don’t assume other people don’t know what they are talking about. It is not agreeable and obviously it is not always true.

design for light airs (post 66)

About being Polite…well, Guillermo, I have tried, especially in this thread.

[Guillermo]

Paulo,
As you've probably noticed, I was very upset with that your scorning post, and ceased answering you because I didn't want going down into that level of personal aggresion discussion. After summer I tried to be nice to you again, just for the sake of these forums, but I realize it's of no use. You came back in with the same kind of attitude. Well, I'm not available to this nonsense anymore.

[Guillermo]

Now let's analize how STIX varies with the several input data. A kind of "what if" game. I'll use the data of the RED boat.

Originally we had:

Vessel Name: “RED MODEL” (LIGHT)

INPUTS

Overall Hull Length 11,98 m
Length Waterline 10,57 m
Flooded Buoyancy (Y/N) N
Beam Waterline 3,27 m
Beam 4,1 m
Displacement MSC 5165 kg
Displacement Max 6190 kg
Height of CE above DWL 6,87 m
Height of CLR below DWL 0,95 m
Angle of vanishing stability 123 deg
Downflooding angle 137 deg
GZ at downflooding angle -0,23 m
GZ at 90 degrees 0,58 m
Sail Area 71,1 sq.m
Area to flooding (Agz) 74,46 m.deg
Area to AVS 75,56 m.deg


RESULTS

Base Length Factor (LBS) 11,040
FL 1,001
Displacement Length Factor (FDL) 0,914
FB 2,519
Beam Displacement Factor (FBD) 0,815
FR 3,066
Knockdown Recovery Factor (FKR) 1,146
Inversion Recovery Factor (FIR) 1,010
Dynamic Stability Factor (FDS) 1,381
Vaw Not aplicable
Wind Moment Factor (FWM) 1,000
Downflooding Factor (FDF) 1,250
Delta 0

STIX 38,838

DESIGN CATEGORY A
Wave height max 7 metres
Windspeed max. Force 10


Now increasing LOA from 11,98 m to 13,0 m (just increasing overhangs to an oldies style one), we realize STIX (you may check it with the spreadsheet I've posted before), instead of increasing, DECREASES from 38,838 down to 38,771
Not a big deal, you may think, but in the limits this can make a long overhangs boat not categorizable under Cat A, while an squared ends one could pass (with all it's marketing consequences).
But it will have not only marketing consequences, but also safety ones, because surviving in rough weather conditions, in situations where a boat is heeled 90º or more, the boat with longer overhangs probably is able to defend itself better than a squared one. Rolf Eliasson states that for those conditions probably is LOA what should be doubled in the formula and not LWL.

(To be continued...)

[Vega]

Originally Posted by Guillermo

Paulo,
... I was very upset with that your scorning post... I didn't want to enter into that level of discussion.

Guillermo, I agree with you. There is no pleasure in replying to "scorning posts", even if a reply is needed, just to show that there was no reason for that “scorning”.

But may I remind you that in this thread it was you the only one who made scorning comments:

Originally Posted by Guillermo

Don't make me laugh. ...Please teach us. :rolleyes.

I hope that this disagreeable matter is finished, because I would like very much to have time to post about the subject of this thread: The STIX numbers.

No hard feelings,

Vega (Paulo)

[Guillermo]

Thanks, Paulo.
I recognize I overreacted. Let's go boating again.
Cheers.

[Guillermo]

Claus,
6.4.8 states that Φd shall be taken as the least of the following: Φdc, Φdh and Φda1. This last I've already posted what it is. The other two:

Φdc: Downflooding angle to cockpits that are not quick draining according to ISO 11812
Φdh: Downflooding angle to any main access hatchway.

Degree of watertightness 3 is "protection against splashing water", as known.

This, united to the relatively small area required, is what makes me think Φda1 relates to small openings. But I may be wrong, of course. In my opinion the sense seems to be this one, but I agree with you that redaction is not clear enough.

By a quick look I have not find a clue neither in ISO 12216 nor in ISO 11812

I would love to know other people's opinion or firm knowledge on this. Anybody?

On my side, I'll put the question to a Notified Body, to find out how they understand this. If I get an answer, I'll post it here.

Cheers.

[Vega]

Guillermo, I am relieved. I believe that both of us "fervemos em pouca água" (and I really don't know how to put this in English), so I believe that that the guilt in what concerns overreacting, is not only yours. I guess that in what concerns temper, we are not very different.

Cheers

Paulo

[Guillermo]

I would very much appreciate if somebody could provide accurate info on the Beneteau OCEANIS CLIPPER 44 CC. I've been sailing one of those for several days in the open waters of the Canary islands and I would like to analize her numbers against my sailing experience. Specifically, stability data and curves will be most appreciated.

A first glance to numbers, as provided at http://www.beneteau-owners.com/
and http://www.beneteauusa.com/sail/prev...44cc_intro.php
but using I,J,P,E from the Oceanis 440, gives the following:

Lh = 13,2 m
Lwl = 11,2 m
Bmax = 4,25 m
Bwl = 3,83 m (as 0.9 Bmax)
Draught = 1,75 m
HD = 0,75 m (guess)
Disp = 12598 kg (full load, 6 crew)
Ballast = 3100 kg
Sail area = 75,7 m2
Power = 72 HP

Length/Beam Ratio L/B = 2,87
Ballast/Disp Ratio W/Disp = 0,25
Displacement/Length Ratio D/L = 250,11
Sail Area/Disp. Ratio SA/D = 14,21
Power/ Disp. Ratio HP/D = 2,59 HP/ton
Hull speed HSPD = 8,12 Kn
Potential Maximum Speed PMS = 8,23 Kn
Velocity Ratio VR = 1,01
Capsize Safety Factor CSF = 1,84
Motion Comfort Ratio MCR = 32,91
Heft Ratio HF = 1,03
Angle of Vanishing Stability AVS = 116 º
Roll Period T = 3,23 Sec
Roll Acceleration Acc = 0,11 G's
Stability Index SI = 0,76


As per a first estimative, the STIX should be around 60, so well into the A Category. As said, more accurate info will be greatly appreciated.
Thanks in advance.

[Vega]

ISO 12217 STIX: 34

AVS: 110

I don't know if I can find a RM curve. The Avs and the STiX are on the low side.

Cheers

[Guillermo]

Thanks, Paulo.
Those STIX and AVS seem to be too low for such a boat. Did you get them from the manufacturer/designer?

[Vega]

Yes the data is provided by the manufacturer and I also think that those numbers are low for a 44ft boat.

Unfortunately it is not the only case:

BAVARIA 42 ISO 12217 STIX: 36
BENETEAU CYCLADES 43 STIX: 36
DISCOVERY 55 STIX: 37
BENETEAU 50 AVS 109 ; ISO 12217 STIX: 41

To have a STIX of 60 in the 45ft range you would have to look at another kind of boats, for instance to the Malo 45 (STIX: 62).

Cheers.

[Guillermo]

This supports my understanding that a lot of pressure was done from manufacturers when the stablishing of the STIX thing. Many boats nowadays categorized as being "A", do not fullfill the requiremnts for proper blue water cruising, as I understand it.

After logging 300+ miles in the Canary islands with the Oceanis 44 CC, in open waters and nice weather conditions, I have to say she has quite uncomfortable movements. Measured rolling period aboard is around 3 seconds, which agrees quite well with the estimated one. An this for a boat with a 4,25 m breadth.
Sleeping in the forward bunks and even in the cockpit is quite uncomfortable even with the slightest chopping/swell, both at sea or at anchor. And this for a very heavy full load cruising condition (My friend carries a lot of gear aboard, we had full tanks and and we were 5 big boys), so probably being the boat close to a 13 tonnnes displacement.
If we work numbers for what Mmsc could be (around 10842 kg), we get:

Ballast/Disp Ratio W/Disp = 0,29
Displacement/Length Ratio D/L = 215,25
Sail Area/Disp. Ratio SA/D = 15,7
Motion Comfort Ratio MCR = 28,33
Heft Ratio HF = 0,89
Roll Period T = 2,84 Sec
Roll Acceleration Acc = 0,15 G's
Stability Index SI = 0,67

So even worse than the ones I posted previously.

Further on, the steering system is not enough safe, in my opinion, with the autopilot disengaging the wheel. The keel configuration (low draught, winged) and the assimetrical hull lines when heeled, make for an excessive leeward walking. The low freeboard at the bow, along with the assimetrical heeled hull, makes the bow very wet, embarking green water on the forward deck when beating to winward, even with as low as 0,7-1 m waves.

It's amazing a boat this size and configuration can have an STIX as low as 34. In my humble opinion it should have been categorized as "B" at its most. I agree with Eliasson's statement about being 40 a much better lower limit for Category A. By the list you have posted, only the Beneteau 50' would have fulfilled the requirement (!). I also agree with him it makes not sense to favour plumb bows. A well conceived reserve of buoyancy forwards is important. Interesting to realize now that freeboard at the bows is not taken into account to stablish the STIX number, which is supposed to give a clue to the seaworthiness of a boat.

Being totally honest, I think most of this kind of boats should be categorized as 'C'. Nice weather coastal cruising 25 miles away from land (What some EU countries legislation allows for this category) is quite enough for them.

[Vega]

Originally Posted by Guillermo

This supports my understanding that a lot of pressure was done from manufacturers when the stablishing of the STIX thing. Many boats nowadays categorized as being "A", do not fullfill the requiremnts for proper blue water cruising, as I understand it.

After logging 300+ miles in the Canary islands with the Oceanis 44 CC, in open waters and nice weather conditions, I have to say she has quite uncomfortable movements. .....

Being totally honest, I think most of this kind of boats should be categorized as 'C'. Nice weather coastal cruising 25 miles away from land (What some EU countries legislation allows for this category) is quite enough for them.

Guillermo I was waiting for someone to reply, not wanting to turn this into a dialogue...but as no one has posted, I would like to comment on your statements.

I agree with you, without going to the point of saying that this boat should be classified as class C.

I have already said that for me, one thing is seaworthiness, other is comfort and the two are not necessarily linked.

For example, take a look at the STIX ,AVS, and seaworthiness of these very sporty and uncomfortable cruiser-racers:

Elan 45 : Stix 44, AVS 124 ;

Beneteau First 44.7 : Stix 41, Avs 130

X-Yachts IMX-45 : Stix 46, Avs 124

X-Yacht IMX-40 : Stix 47 Avs 132

J 133: Stix 46, Avs 130

Why does the Beneteau Oceanis 44 cc have such low numbers on seaworthiness? The Oceanis 411 is smaller and has a higher Stix (37). At first sight, that doesn’t seem to make much sense.

You know, some years ago, when Bavaria 40 Ocean came out in the market I was interested in it. It looked like an Oceangoing boat (very much alike the Halberg-Rassy 40), so I got some detailed information only to be vastly disappointed. That boat had the same hull as the “normal 40”, the same ballast, only the interior and upper deck were different.

As the boat had more freeboard and more weight up, it would have a higher center of gravity, compared with the “normal version” and it would not be more seaworthy, but less. Ridiculous!

I think that with the Oceanis 44cc it happens exactly the same.

This time, about comfort, in what regards the Oceanis 44 cc, I fully agree with you. That boat is sold under the image of a comfortable oceangoing cruiser, so it should be comfortable and seaworthy. It is like selling a car that looks like a Mercedes, has the safety of a cheap Fiat and it is as uncomfortable as a Ferrari.

Cheers

[luso]

Hello,
You guys are very knowledgable.So I wonder if you could help us. We have a 48' schooner metal hull made by Carof design in 87. I believe the model name is Lex Erterna. We could never find any information about her estability and I 'm very curious about it.We've been refiting her for the past 6 years. We are getting close to being ready to leave port and sail around for awhile. I am always wondering about her limits of estability. Would she flip back? How long would that process take? How far can she heel? Maybe you could help us answer these questions? Here goes some info on her:
Hull 48'
loa 42'
beam 14.5'.
hard-chine,
deadwood cut away type of keel,
freeboard 5',5"
displacement 30.000[I believe in metric]
We would appreciate very much any info you could give us
thank you, Luso