Location of VCG/KG

[Guest62110524]

Originally Posted by Ad Hoc

Guillermo

As i noted in #21, i haven't used 'avs' since i was a student some 25years ago. All the boats i design (commercial) avs is never a consideration.

I know that sailing boats use them as a basis for a measure of their "stability"....and I'm aware that there is "some use" as such in fishing boats. But exactly their usage in fishing boats to a criterion, I'm not fully aware of, since not my field. The boat shown was a small pleasure craft, which doesn't fall into to either category.

I just thought that since the boat in question doesn't fall into either, it would become confusing debating avs when it doesn't apply to the design, and certainly not to the original question of "stiffness" or "seakeeping".

But for 100% completeness, yes avs does apply to some design categories....but not many! I've never used it as a design 'driver'...may be you have??

I've reviewed several papers on fishing boats, but their concern was more about green water and freeboard on the fore deck and the reduction in GM/GZ owing to said, on the capsizing probabilities and referring to the Torremolinos Convention. Again, no avs metioned.

no you had no idea, so pl;ease just for once be honest
do not talk DOWN to people without degrees in NA you firstly said'I have no idea what AVS IS" NEXT NHING, YOUA RE SAYING" I DID NOT Study for 22 years"
we nver forget
Puts you at age 42?
I am am 63, I have 40 years building, so nver put me down , !! Ok!!

[Ad Hoc]

whoosh

ok, so let me get this straight. You start your 'post' about the seakeeping and stiffness of your boat. You mention the avs.

So, what is avs....so, it is an acronym I've never come across before, neither have others as noted by Paul. As professionals, before answering questions it is best to be clear on definitions, so we ask questions to avoid misunderstandings. It is simple.

You then seem to be under the impression that the avs is related to the seakeeping and stiffness, but then change tack, to suggest that anyone who doesn't know what 'avs' is indicative of what...??..er....pass

If you understood your own question, you would know that avs has nothing to do with your boat and your original question, which you have now removed.

You seem to think that everyone uses avs to establish the seakeeping but then again change tack to 'stability' for all boats. The avs is not a criterion for all boats, never has been. If you understand anything about rules and regulations and how this influences a design you would not make such a vacuous statement. And as such, understand the reply. You're not a naval architect, so i gave further clarification, but you decided to ignore this.

As usual you decide to ignore your own postings and replies of others which you don't understand or don't want to and revert to the usual personal tirades and ad hominem replies rather than the question itself.

And for someone who keeps going on about "..I am am 63, I have 40 years building, so nver put me down , !! Ok!!.."

You dont appear to know a thing about structures, noted here:
metal frame detail
you still haven't answered the question...to show me your LR cert for this shocking design which you maintain is acceptable. This is not evidence of someone being in building for 40years, only someone who has been in building, ie time, but during 40 years has learnt nothing.

Also you seem to know nothing about 6082, the main 6000 series extrusion being used in the shipbuilding industry for over 15 years:
6082 forming
What ahve you been doing for 40 years???..or at the very least, the last 15 years??

You don't appear to know how to contact suppliers of aluminum beyond, well, I'm not sure since anyone in the industry for 40 years would know, but when you ask for advice and its given:
kobe steel al al dnv plate in China

all you do is resort to ad hominem attacks again rather than address the question and not the person and, actually have the grace to say thanks for pointing you in the direction where all you need are just a few clicks from the database for you answer.

And then you decide to personally threaten and abuse me, because you cannot answer a simple question which you raised:
http://www.boatdesign.net/forums/boa...um-1196-3.html
post #43

I could post more, but there is no point. Anyone looking at those links can make up their own minds.

Such continual ranting and attacking I can only conclude you must have a personality disorder and/or an inferiority complex about anyone that may or may not know more than you or disagrees with you! Since you appear to think you know everything as noted by your statement above and you can't, no, MUST NOT be told otherwise.

Most sad behaviour for a 63 year old!...not a humble peaceful man

PS..no doubt i'll get the usual childish immature neg points again, so predictable

[baeckmo]

Woosh, when you use shorts or acronyms, do you really expect all combinations seen in your local corner to be in global use? Don't get rude with people when they ask for a definition for clarity of the discussion!! This is an international meeting place; the fact that we all communicate (the best we can..) in English of sorts, does not give you the right to climb any high horses!! You owe Ad Hoc an excuse!

The thread is about stability, which is not necessarily identical with safety. The "avs" is not per se a requisite for stability, but it may be so for safety!

As for the use of "range of positive GZ", it is used by DNV for commercial vessels ("15 m rules"). The integrated area under the GZ curve, up to zero GZ is a measure of the work needed to capsize the vessel, say from a knockout breaking wave.

For instance it says:

"GZ at 30 deg to be minimum 0.2 m"
"GZmax to occur at an angle more than 25 deg"
"GZ to be positive up to 70 deg for fishing vessels and 50 deg for others"

We designed and built some commercial cats for fishing and fifi/resque according to these rules. A seaworthy cat has different stability characteristics, making it nearly impossible to comply with number two of those limits. After lengthy discussions and tests, our design was accepted when its "positive GZ-area" (in addition to other demands....) was equal to, or better than a monohull with stability according to the book.

[Guillermo]

Originally Posted by baeckmo

"GZ to be positive up to 70 deg for fishing vessels and 50 deg for others"

Ad Hoc,
Here you have an AVS based criteria by DNV, i.e. Not at the office now, I can tomorrow search for more, but you're right: Not of common use for most vessels, except sailing and commercial fishing boats.

All,
Let's behave please. There have been more than enough ad-hominem attacks clouding this forums (and I'm not free of guilt, I must say) bringing nothing useful to debates.

Cheers.

[Guest62110524]

Originally Posted by baeckmo

Woosh, when you use shorts or acronyms, do you really expect all combinations seen in your local corner to be in global use? Don't get rude with people when they ask for a definition for clarity of the discussion!! This is an international meeting place; the fact that we all communicate (the best we can..) in English of sorts, does not give you the right to climb any high horses!! You owe Ad Hoc an excuse!

The thread is about stability, which is not necessarily identical with safety. The "avs" is not per se a requisite for stability, but it may be so for safety!

As for the use of "range of positive GZ", it is used by DNV for commercial vessels ("15 m rules"). The integrated area under the GZ curve, up to zero GZ is a measure of the work needed to capsize the vessel, say from a knockout breaking wave.

For instance it says:

"GZ at 30 deg to be minimum 0.2 m"
"GZmax to occur at an angle more than 25 deg"
"GZ to be positive up to 70 deg for fishing vessels and 50 deg for others"

We designed and built some commercial cats for fishing and fifi/resque according to these rules. A seaworthy cat has different stability characteristics, making it nearly impossible to comply with number two of those limits. After lengthy discussions and tests, our design was accepted when its "positive GZ-area" (in addition to other demands....) was equal to, or better than a monohull with stability according to the book.

No, not always, often not
I have learnt a lot of tolerance here over the years, But some members, take great delight in belittling others, can never admit to being wrong , can never ever learn, they deem it beneath them to learn from certain people they consider to be less(educated) in the formal sense
ROA,Mike used thsi term to me, I have not a clue as to its meanang, , if you look back, there are a 100 such examples, that only NA people are familiar with
When NA, s talk to people in here like myself, they need to speak in more layman like terms
they need to show patience , as do most One or two do not, they always try to be superior
So if I have offended some, there is a reason,
I talk to many from here in private It pays, that is the only way one can KNOW people
if you see some underlying frustration with a certain member, there is a good reason
cheers Stu

[Ad Hoc]

Guillermo

"...There have been more than enough ad-hominem attacks clouding this forums.."

Couldn't agree more, the site has been taken over by such, with egos the size of Europe and/or computer PlayStation button pushers defending their computer colour plots not the technical debate.. It stifles proper debate immediately. But for many, as also noted above, it appears to be their only way of debating, why...go figure???????

[Guest62110524]

also I find it hard to believe that (SHIP) ferries do not have AVS calculated in design

[MikeJohns]

Stuart moved his post here:


roll patterns and stabilty

And in reply to this

Originally Posted by whoosh

............
ROA,Mike used thsi term to me, I have not a clue as to its meanang, , if you look back, there are a 100 such examples, that only NA people are familiar with............

http://en.wikipedia.org/wiki/Respons...itude_operator

You only have to ask, no intention to confuse sorry.
I guess we get a bit immersed in everyday jargon in the fields we work in and presume it makes sense to everyone.

[Ad Hoc]

Mike

"...You only have to ask,.."

Exactly. Hence my qualifier above..."...before answering questions it is best to be clear on definitions, so we ask questions to avoid misunderstandings..."

"...I guess we get a bit immersed in everyday jargon in the fields we work in.."
Spot on again. Hence, just seeking clarification, that's it, no magic.

However, any more that is read into "asking a question for clarification" is of ones own choosing...

[Ad Hoc]

A very quick summary of stability for (SHIPS) ferries.

"avs" is not a driver....other more important issues such as min/max GZ/GM, downflooding point, 'range of stability' from downflooding/damage etc etc, are however!

But this is all about to change anyway with the new SOLAS2009.

Viz:

SOLAS2009 will supersede both IMO Resolution A.265(VIII) and the deterministic subdivision and damage stability calculations in SOLAS Ch II-1 Part B for passenger ships and replace SOLAS Ch II-1 Part B-1 for dry cargo ships.
For passenger ships, concepts such as floodable length, permissible length, criterion numeral, margin line, 1 and 2 compartment standards and the B/5 maximum extent of side damage penetration will be disappearing.

The revised SOLAS2009 damage stability regulations are designed to give an equivalent level of safety to the current SOLAS regulations. Extensive analysis of existing ships and collision statistics was carried out to determine the most suitable method of formulating the probabilistic terms such as p, s, A and R (Ref. MSC.194(80) Regulations 6 and 7). Much of this work was carried out under the auspices of HARDER, a European project involving maritime academic institutions and other authorities, all reporting their findings to IMO.

[Guest62110524]

Originally Posted by MikeJohns

Stuart moved his post here:
roll patterns and stabilty




http://en.wikipedia.org/wiki/Respons...itude_operator

You only have to ask, no intention to confuse sorry.
I guess we get a bit immersed in everyday jargon in the fields we work in and presume it makes sense to everyone.

no!!!! tis up to me to find out, and youa re always more than really helpful
you have a way of explaining(teecher) -- that is not belittling or talking down

[Paul Kotzebue]

Originally Posted by whoosh

also I find it hard to believe that (SHIP) ferries do not have AVS calculated in design

I work mostly with USCG intact and damage stability standards which are based on the IMO standards. The standards are more or less concerned with the amount of energy it takes to heel the vessel to a certain angle, or the energy to heel the vessel from one angle to another. Therefore, that is what drives the design. Most commercial vessels are not self-righting, so the standards are designed to keep the vessel from capsizing in the first place. Also, the standards consider the downflood angle to be the "end" of the righting arm curve. For most vessels the downflood angle is less than AVS, so AVS is not a factor. That said, it is easy for the designer to let the righting arm curve run out to or beyond the AVS if he/she is interested. I usually do just that for sailing vessel stability calculations.

The stability report I submitted to the U.S. Navy for the 85 ft Torpedo Retrievers I designed was nearly 200 pages long. All the righting arm curves, and there were many, stopped at the downflood angle which was always less than AVS.

I hope this adds some clarification.

[Guest62110524]

yes Paul , now I understand, but I ddi say in my case they also were not intersted and yes the downflood height is way before the point of no return
I do not know if you have seen these big ferries, waterplane gets get bigger as heel comes in
How far In your opinion would they heel before rolling