ISO 12217-1 Worksheet 4 Question

Can someone help me interpret what this means? Is it saying you must heel the boat until your down-flooding point is completely covered, and then measure the area of all other down-flooding points that are underwater? This doesn't seem right to me. Downflooding on my boat is a side door on the pilothouse so the boat would have to be nearly on its side to cover the door. For more context I'll upload a pitcure of my boat tomorrow.

 

The boat must be considered in a fully loaded condition. This verification can be done through an actual physical test or by calculation.

1. If the physical test is carried out, a number of people equal to the maximum crew must be brought on board. These people must be positioned so that the boat has zero heel and trim. Under these conditions, the height from the waterline to the various flooding points is measured.

2. When the study is carried out by calculation, the fully loaded condition is assumed, but the passenger weight (75 kg per passenger) is moved so that the equilibrium waterline results in zero heel and trim. The loading condition called mLD could give rise to a certain non-zero trim and heel. Therefore, for the test, the passengers are moved until zero heel and trim are achieved. In this situation, whose flotation is indicated by the study, the heights of the flooding points are measured relative to the flotation.

Furthermore, Figures 3 and 4 provide the minimum required flooding heights, depending on the design category chosen for the boat. None of the heights obtained using option 1 or 2 should be less than the figure obtained in Figures 3 or 4.
This check does not take into account any heel or trim. The heights of each opening relative to the waterline are simply measured (heel = 0 and trim = 0). The distance from the centerline does not even need to be measured, as is done in dynamic stability studies.

Now answering your question, "alpha" is the sum of the surfaces of the openings that are considered as possible flood points.

 

Thanks for the clarification. That's much simpler than I thought.

 

Yes, it is, but the creators of the ISO do everything possible to ensure that no one understands anything. They disguise themselves as scientists (I say they do because they aren't) and try to turn this manual, for people with limited expertise, into what ISO standards should be, into a manual for operating spacecraft.
Good luck with small crafts ISO standards.

 

Hi Andrew,

What is indicated by TANSL is perfectly right, except : "zero heel and trim".
This is not correct. People and mass onboard, whether actually tested or simulated, shall be at their rightfull place, in accordance with ISO 12217 definition :
EN ISO 12217-1:2017
3.4.5
maximum load condition
boat in the light craft condition with the maximum load added so as to produce the design trim, the crew
being in positions typically used when the boat is under way (e.g. within the cabin, cockpit, deckhouse
or wheelhouse) such positions being designated by the builder"

In addition, if the boat has any list in mldc, with maximum load being in positions as described in the definition, then the downflooding height of any downflooding opening shall be measured as the boat is, from waterplane to the bottom of the opening.

 

It's not wise to mislead the public further. Studying stability at high angles for the mLDC loading condition is one thing, and the test required by ISO is quite another. They are very similar studies, but not the same. In any case, this shows the lack of practicality and clarity with which the scientists who created the standard have acted. If you were right, wouldn't it have been enough to say that the corresponding IMO stability criterion should be met?

 

When IMO could be used instead of ISO, why not. If not, then ISO requirements shall apply.

 

Thanks for the clarification, Alan, but I see I've explained myself poorly. What I mean is that if the boat must meet a stability criterion that's the same as an IMO criterion, it would be enough to simply state it that way. On the contrary, what's being asked for is, or so I understand, something different—very similar in approach but different in its verifications—to the IMO criterion, something specific for small crafts.

Edited .. Sorry, @Alan Cattelliot, I was wrong, the standard talks about design trim and I interpreted it as zero trim.