Swain BS_36 Stability curve

Don't have 12217-1 at hand so I can't check it, but shouldn't 12217-2 (Sailing yachts 6m to 24m) be the part of the rule used here instead?

 

Probably. 12217-1 applies to non-sailing boats with As < 0.07 * mldc^(2/3).

 

compliance

NZ , can do as one wishes BUT when going foreign she will need Cat 1 that is same as for ocean racing. But only if she is NZ registered
Eu recreational craft directive, if not for sale compliance not reqd

 

weight Angel

I do not know how you would arrive at conclusion that a double ended 46 footer with say and immersion of 200-240 kg /cm could be down 200mm due to builder, what would a builder place in such a small boat that may put her disp.up 4- 5 tonnes?In thaty case was home built In the case of the 90 30 tonne , these figures being approximates.In the case of the bigger boat, most of his launchings were like this. this was in days when CAD was not in use.

 

That was not the point Angel made..

It's was this..

And I think it's a pretty good one too..

 

Teddy

Quite right. It wasn’t until I double checked, I realised I picked up 12217-1 not 12217-2…oh well. But the result is the same.

If you look at 12217-2, say 6.4 Stability Index and look at 6.4.2 Dynamic Stability Factor

FDS = Agz/{15.81*sq.rt(Lh)}...........Lh = hull length

If being generous and saying that downflood occurs at say 100 degrees (very conservative), the values for Agz up to 100 degrees is roughly 18.5deg.m, as per Tad’s GZ curve.

Therefore FDS = 0.37

ISO states that FDS shall never be taken as less than 0.5 or greater than 1.5

So, according to 6.4.2 of ISO, it fails.


Abcdefg

In the EU….rules now apply in the same way as with a car. If Joe Bloggs down the road built a car from scrap..hailed it as the best car ever…and then wanted to take it on the raod…the car must be inspected and subjected to the EU national state law on road compliance. Does it satisfy minimum standards for road safety etc. If not..it is not allowed on the road….would you buy a car that is not legally road worthy?

Finally, the same is now apply to boats…that is the raison d’être of ISO. If you try and get insurance with your boat..first question…what standards does it comply it. End of story…same as a car..is it legally road worthy.

The reasons for ISO is to stop back yard builders/designers with no professionalism and accountability. It is to bring the leisure market more in line with the commercial filed, for accountability.

If You wish to put YOUR life in danger with a backyard boat built by “anon” and designed by “anon”, fine..but YOU’RE not allowed to place others in danger…unless you’re outside the EU..in which you can do what you like, just don’t try and sell the boat in the EU.

In the waters of the EU....however, many other states outside the EU are now adopting the ISO rules. I recently did a boat for the US Govt....they quoted ISO standards for stability.

Not true.

The "National Standrad for Australian Builders Plate for Recreational Boats" states

9.5 BUOYANCY INFORMATION
Where the buoyancy information specified in Clause 8.1 h) is the term “basic flotation” or the term “level flotation”, the buoyancy performance shall be determined in accordance with one of the following:
a) ABYC Standards and Technical Information Reports for Small Craft
Edition 3 Page 14 21 November 2005
National Standard for the Australian Builders Plate for Recreational Boats
b) AS 1799
c) ISO 6185
d) ISO 12217
e) ISO 13590
f) A relevant national or international standard that is not one of those listed above

And in case you're not familair with your own rules and its objectives, it states thus:

2 OBJECTIVE
The objective of the ABP is to enhance the safety of persons on a recreational boat. It does this by providing for—
a) a declaration by the builder or importer that the boat meets, to the extent specified within this Standard, the requirements of relevant national or international standards applicable to recreational boats;
b) ready access to essential safety information on the limitations applicable to the use of the boat to encourage appropriate and responsible use of the boat; and
c) information on the buoyancy characteristics of the boat so that persons may make informed decisions regarding its purchase and use.

 

and these last two excellent and factual posts by Ad Hoc should bring closure to this issue hopefully. What is the point of continuing the stability issue of this design/boat?
Based on the tedious efforts of TAD producing quite an accurate stability curve and numbers on data available to him, and Ad Hoc's postmortem of the data to legal requirements;

1. It failed the ISO criteria
2. Design non compliant making it a risky affair.

What more can be discussed unless the design is drastically altered to comply with the ISO standard, and I accept bets that wont be forthcoming.
One cannot give a dead man medicine....

 

well then go up and see where i answered her.
And she did ask about weight too. Thank you

 

My interpretation is if FDS < 0.5, then FDS is taken as 0.5 for the subsequent STIX calculation. If FDS > 1.5, then FDS is taken as 1.5 for the subsequent STIX calculation.

 

Paul

It depends upon how you view the results, but that is not correct according to ISO.

In this case the FDS is < 0.5, so it is a fail. Therefore what must be done for the vessel to comply?. Since you can’t just assume, well I get 0.38, so I will then use 0.5 instead, you must ensure the result does produce a value of at least 0.5; it is not a default value. ..hence, clearly the FDS must be between 0.5 and 1.50…..how is that achieved??

Well, the rule has 3 inputs.



1) GZ area up to downflood (if less than AVS)
2) The downflood angle itself
3) Hull length

One can raise the downflood angle….but once the vessel is more than 90 degrees, this is not such an easy proposition! Increasing the freeboard to said downflood is fine when upright...but when the vessel is horizontal, or greater (as in the very generous 100 degrees I used), the increase in freeboard to downflood makes no real difference.

So, the area under the GZ curve or length would be the drivers here.

Change hull length….possible…but using the values from Tad’s and rejigging the formula, the hull would have to be 5.47m waterline to pass….hmmm..don’t think would happen.

Therefore the only option available is to increase the area under the GZ to produce a FDS of at least 0.5 which is roughly 24.5deg.m. She is currently 18.5 deg.m..not so easy perhaps too?

To increase the area under the GZ require lowering the KG and/or manipulation of the hull form. In either case, hull form manipulation would not be so easy, it is near “fixed” since it is “pulled” into shape…ergo it is what it is.

Therefore lowering the KG is the only way to satisfy 6.4.2 to obtain an FDS between 0.5 and 1.5 to pass.

 

I am well aware of the CE system, In a former position, it was my responsibility to look after my employers interests with regard to obtaining and maintaining the CE mark on their products (boats).

If I recall correctly, in the EU, a self built boat (which we are supposed to be talking about) that is not intended to be sold for a period of time (5 years??) is not required to undergo the same analysis as the professionally built commercial and liesure vessels. I also believe racing vessels are except in a similar manner. Please do not confuse them.

Again, with the commercial vessels thing? Apples and oranges.

Read a little more carefully. 8.1h refers to vessels less than 6m in length. Last I looked, 36' is a little more than that. Please refer to the discussion above on the application of imperial and metric units

Besides, the section you refer to is solely concerned with the determination of how much foam is required to be added and its distribution in order to keep a swamped vessel either afloat (basic flotation) or afloat and upright (level flotation). This is completely seperate from intact stability as is being discussed.

I like to think I am familar with most of our own rules, considering I use them on occaision........



So I ask again, under which juristiction, is this particular vessel, an amatuer built, amatuer design, of 36' built for long range personal cruising (not likely to be sold) required to comply with the requirements that you have set for it? Canada perhaps??? New Zealand??? Japan???

 

Correct section 8.1 is “Boats Less Than 6m in Length”.

Perhaps you are unaware that section 8.2 is “Boats 6m or More in Length”. Ergo the BS36” falls under this category and compliance when apply ISO 12217 as 9.5 d) of said rule.

Where ever one lives and whichever rules are imposed by the local authority where one lives.

One cannot assume, I live in say… France, I won’t comply with ISO 12217 for example. It is a European standard. The standard is a measure of safety for leisure boats.

Are you suggesting that one should not build/design a boat to an internationally accepted set of rules and regulations because….”I can’t be bothered” or…”it is too difficult”…or “rules are for people with deep pockets”…or whatever reason you care to suggest?

Since either one is happy to comply or one is not.

If you do not accept the ISO, or its variants, I assume you take the same caviller attitude with your car…and buying from a backyard builder and care not what materials are used nor if the brakes are fitted and drive at speeds and take corners beyond what is considered safe for the car and its "parts"….or your house, built by a cowboy with materials washed up on the beach and salvaged from scrap yards…etc

Whether “we” like it or not…these standards (ISO et al), are for the safety of those less informed about such things so when they buy a product, all reasonable measures have been taken to ensure that the product under normal operating conditions, is safe.

Either you’re happy to buy a product that meets international standards or you’re happy to buy a product that does not meet them. The choice is yours…but I’d wager most would like to know whether a product meets an set of safety criteria before they buy.

Would you buy a slab of beef that has a big large stamp BSE free, tested to XXX standards... next to a slice of beef that has nothing on it but is a bit cheaper..?

Everything comes at a price....when i go to sea, i don't gamble with my, or others, safety, period!

 

Plainly and simply, you are wrong.

Section 9 refers to standards that may be used in the determination both 8.1 and 8.2.

Iso 12217 appears as a standard that may be used to determine the required amount and arrangement of foam floatation (or buoyancy compartments). I am assuming that there is a method within 12217 that allows for this. Myself, I tend to use AS 1799 for this purpose which is one of the other standards listed. "9.5 buoyancy information" underwhich 12217 is listed is applied to 8.1 which concerns vessels less than 6m.



Please read it again, and again if you don't believe me.

Again, we are not talking about commercial vessels, or commercially produced recreational vessels.
This "design" (a very loose description) is driven directly toward amateurs with vast available time building boats for themselves on the cheap. Profit driven organisations are a different ball game.

If you had said that the information presented by tad above (please keep in mind the nature of the information - no offence to tad) does not meet the appropriate stability standards required to sell it in a profit driven sense as a recreational vessel into the EU then that would be fine, but you did not.



Finally, I did not say that I reject recognised standards such as ISO, etc and I can assure you that I do not take a cavalier attitude to the vessels I design.

 

Ad Hoc, see http://www.nmsc.gov.au/media/pages_media_files/files/faq_build_Jan11.pdf

where it states;

"New boats are required to have an ABP plate with the exception of: an amphibious
vehicle; a canoe, kayak or surf ski or similar vessel designed to be powered by
paddle; a rowing shell used for racing or rowing training; a sailboard or sail kite; a
surf row boat; a hydrofoil or hovercraft; a race boat; a sailing vessel; a submersible;
and an aquatic toy.
A sailing boat with an auxiliary engine is exempt from the requirement to have an
ABP fitted.

This is confirmed by regulations, for example the state of Victoria's "FAIR TRADING (INFORMATION STANDARD) (AUSTRALIAN BUILDERS PLATE STANDARD) REGULATIONS 2009 (SR NO 125 OF 2009) - REG 4(3)(c) and 4(3)(i) exclude racing vessels from having to have an ABP, while 4(3)(l) excludes sailing vessels (which under Reg 3 are defined as including sailing vessels with an auxiliary engine).

So someone can design and build a cruising yacht here without worrying about ABP. In many ways it's very different from a car - if a car's brakes or steering fail when it's on a Sunday drive there is a high chance that other road users will be killed or injured. If a boat rolls when it's on a Sunday sail there is a very low chance that other boaters will be killed or injured. I'd hazard a guess that the chance of a yacht rolling at any one time is a lot less than the chance of a car being involved in an accident.

Of course, I'm not saying that unsafe boats should be at sea. But there is a cost/benefit analysis in everything in life, and maybe sometimes loading on extra rules may not be worth the cost.

As you say, "Everything comes at a price...." Are you sure that given the fact that nothing is free, it's always better to spend some of the limited available funds on obtaining ISO certification? Money, time and effort may be better spent on other areas depending on the planned trip, crew, etc.

"when i go to sea, i don't gamble with my, or others, safety, period!"

Depends on your definition of "gamble"... we always apply some cost/benefit/practicality limits to our safety, don't we?

 

Hmmm..this is deteriorating into a I say potaTO and you say poTAto discussion..not sure what the point is really.

In section 9.5 “..the buoyancy performance shall be determined…”
There is no mention of may be …but, shall be. Your point being you read this wording as may be, when it states shall be…so not sure what you’re trying to say?

Just so Im clear…

Not sure I follow,…where does it say that the information/data used is NOT that presented by Tad and that using said data to compare against ISO,,?...your point being?

Where does it state in ISO that the rules only applies to profit driven vessels?...i cannot find profit as in input into the measure of a vessels stability in ISO, can you guide me please, as this is a new one for me.