Flotation

[Stevew23]

What is the position on flotation in the hull please? I'm fairly sure its not allowed and may well have been discussed here before - I have a fellow wanting to fit a complicated system of plastic bags and tubes in his hull, so wanted to get the right info...

[Barry Chisam]

Hi Steve not sure myself but its unusual for a rules question not to have plenty of opinions. Maybe they are all like me.
Better to keep your mouth shut and have people think you are stupid rather than open it and remove all doubt.

[Hiljoball]

The answer should be simple - the IOM Rule is 'closed' - anything not specifically permitted is non-compliant.

So look through the Class Rule and find a section that permits such buoyancy; and if it is not there, then you have your answer.

John

[Stevew23]

Well that's what I always understood, but I've heard several people say otherwise, so I'm starting to wonder...

[Hiljoball]

Hi Steve,

the answer is easy - when they make a statement like that, just ask them to show you the relevant class rule.

John

[David L Alston]

I am most intrigued by this question and even more so by the answers …for more than one reason.

But let us work through this for my benefit:-

The class rules envision a totally closed hull not an open boat design. But there is nothing actually stating this in the Class Rules.
Most crucially flotation is provided by the Hull.
There are no limitations upon flotation other than that the boat shall be 1000mm long, shall have a minimum mass of 4 kg and has a restriction upon voids.

What IS restricted are materials:-

D2.1 b) With the exception of elastomeric materials, materials shall not be: expanded, foamed, honeycombed.

And

D2.1a) (8) Thermoplastic, which may be moulded, containing only permitted materials.

So placing a plastic bag in the hull filled with air is clearly Class Compliant

However filling the hull with Polystyrene beads would not be Class Compliant because the material is not Class Compliant

[Hiljoball]

Also read the ERS, especially D1.1 which defines the hull.

John

[David L Alston]

Ok so ERS defines a hul as ...

D.1.1 Hull
The shell including any transom, the deck including any superstructure, the
internal structure including any cockpit, the fittings associated with these parts
and any corrector weights.

So the radio pot or container in terms of this definition is not part of the hull and given it is not specifically permitter is not in compliance of the class rules !

I still fail to make the connection with a plastic bag filled with air insude the hull.


Flotation is not defined in the ERS when applied to a boat. As in my old Finn and Enterprise which would surly sink if capsised without them.


Do get me wrong here I cannot for the life of me see the necessirt or advangage in filling the boat with plastic bags. But is there any reason why one cannot

[Hiljoball]

My take is that you could install bulkheads and create watertight compartments. But you cannot drop in air bags as they would not be part of the shell, but neither are they listed as allowable fittings.

John

[David L Alston]

..

[David L Alston]

John,
I hear you, but you must concede that a bag manufactured from a permitted material located within the hull becomes the part of the INTERNAL STRUCTURE of the hull as defined by the ERS.

The same would extend to a bulkhead formed with a polythene sheet, a radio compartment formed by a honey jar and any other container one may wish to include would be classes as the Hull.

ERS D.1.1 Hull
The shell including any transom, the deck including any superstructure, the internal structure including any cockpit, the fittings associated with these parts and any corrector weights.


The concept of not having a full deck and providing water exclusion / displacement locations by means of a plastic bag might be interesting but is not likely to save any weight or offer any benefit but let not kick a man because he is concerned that his boat may get holed and sink in a deep pond never to be recovered.

I believe we are too eager to dismiss an idea on the basis that it is unconventional or unnecessary in some one's option rather than truly identifying the specific area of non-compliance.

It must be accepted that a bulkhead or plastic bag does not provide flotation it simply restricts or controls flooding.

However a system of plastic bags or bulkheads arranged such that water ballast could be moved would defiantly not be in compliance of the class rules irrespective of the materials of construction would it not?

Clearly a plastic bag in the hull is in compliance with the Class Rules whereas filling the hull with polystyrene beads or expanding foam would not be.

..

[David L Alston]

Steve Woolfenden

I see your pain and I truly believe that the builder should make the decision as to the acceptability of a particular design and class compliance in place of trying to transfer this responsibility to a NCA or perhaps you.

So what is your friend actually contemplating. And is he such a bad builder that he feels a need to make the boat unsinkable.

As I recall there are no Icebergs in Florida Lake in winter

Dave