Rule 4.3.3

[sir_skiffalot]

G'day from the Southern Hemisphere!

I'm currently designing a National 12 (mostly for shits and giggles), and I am unsure as to how Rule 4.3.3 is meant to be interpreted...

4.3.3 - At midlength, measured 229mm above the lowest points on the outer surface of the skin (or a straight line, bridging any hollows, parallel with the vertical plane through the fore and aft centreline) between 40mm and 150mm from the fore and aft centreline of the hull at midlength, shall not be less than 1168mm. This measurement shall be taken to the straight line bridging adjacent lands if any.

The way I see this is: At a transverse section at midlength (1830mm from bow), the boat shall pass through a point 229mm above the baseline of the boat (baseline defined as a horizontal line passing tangential to the lowest point on the skin in a fore-aft manner) in a fair fashion at a beam of no less than 1168 mm.

As such, I've started designing my hull to pass through this point, and then narrowing to a chine below the DWL.

Is the extra complexity of the rule simply there to prevent significant hollows beneath the measurement point, such as on some of the older Int. 14s and NS14s?

Cheers,
skiff-a-lot

[Mikey C]

Youve read it right. The rule is there to effectively guarantee that boats are of a sailable waterline width.

The 40 - 150 bit is to make allowances for older boats that still have bilge keels - I believe this was added when the hollows rules were tidied up.

Would be interested to see what you come up with!

Cheers

Mike Cooke
N3489 Radical Edward

[sir_skiffalot]

Cheers Mike,

Got to wonder why the rule is so convoluted then when a simple "at midlength, the boat shall pass through a measurement point 229 above the base line in a fair manner, with no hollows in the transverse plane" would suffice! I know these boats have been around since Noah (I think he had a Uffa King...), and as such the rules shouldn't rule out those who want to sail their arks, but simplicity would allow average joe to design his own boat without having to ask questions for clarification and looking like a burk in doing so.

I'll do some renders when I'm happier with my design (looks a little TOO much like a Big Issue at the moment... some more originality wouldn't go astray on my part... plus I don't want to annoy Phil M.!). I'm also considering going for a flatter underside and going for a multi-chined, or at least partially multi-chined design, perhaps becoming rounded towards the bow... ah the joys of being able to muck around with these things!

Unfortunately, there aren't any nat. 12s in Aus, so I've only got pictures and impressions to work off. As such, I think my hull depth is a  bit over the top (I've seen piccys of one really deep nat 12, 3485 I think it is and I must admit while it has practicality and comfort advantages, I'm not a huge fan. These things are meant to be cut-down racers after all!).

Mike, can you give me a rough impression as to the overall depth (hull only) of the B.I. 2 and Foolish? It would be appreciated, just to get the boat in the right kind of scale.

Thanks,
Skiff-a-lot

[Mikey C]

50cm at stem i think for a Foolish, and between 55 - 60 for a Big Issue...

I'm with you on the simplicity, but if you start outlawing older boats, it can all start getting a bit messy!


Cheers

Mike