displacement 12 hull?

[samdoman]

I was just thinking about the shape of modern 12's, and the hulls seem to be more oriented towards heavy weather performance. why has nobody come up with a displacement 12 that would surely dominate in light winds?

I have come up with this model as a possible idea

[rules man (Guest)]

could i driect you towards the class rules?

[samdoman]

I believe it is within the class rule, what do you mean?

[Derek]

Can I suggest you read sections on hollows and on gunwhale overhangs.
Unless things have changed you are not allowed any hollows aft of mid-length and the gunwhale overhang outboard of the sheerline its limited to 50mm.

The flare on this hull must be either hull or gunwhale so it must contravene one of those.

N12s are quite good at getting minimum waterline beam on a 2m wide hull with no hollows. It is one of the main challenges of the design. Another constraint to look out for is the rise of floor which whilst intended initially to avoid boats becoming overly narrow on the waterline, now measures a point about 35mm above the design waterline. Most hulls are spot in the minimum rise of floor by design and some are bumped to meet it. Feeling Foolish is a notable exception.

The "no hollows" rule was (I think) introduced to prevent the need for expensive cold moulded boats and was prompted by the arrival of the 505 with its flared topsides. (Makes it a late '50s rule).
Since we no longer have anything in the rules about "catering for those of limited means" (which was in the first couple of lines of the rules initially) and since we can mould concave surfaces as easily as convex ones, perhaps we should think about deleting the hollows rule.
It would make for a more interesting looking boat - only time will tell if it is faster but it would be interesting to allow someone to try it!

[samdoman]

sothe hull isn't allowed to be concaved?

[mutt]

thats about the long and short of it. No hollows.

[samdoman]

could somebody please explain the gunwhale overhang rule ?

[Marcus (Guest)]

This is an interesting concept and one that I certainly had to get to grips with in producing my latest creation N3503. The boat has no decks in the conventional sense, the topside of the hull simply comes up and rolls over to form a lip that constitutes the deck. However, as Derek has pointed out the deck or gunwale is not allowed to extend more than 2'' outside the shearline athwartships. Thus in order to create a wider lip to give us something to sit on I'm planning to add a strip that stands proud of the hull surface and runs fore aft around the hull 75mm below the shear line. The strip is only 1/8'' thick so it doesn't contravene the "no hollows" rule. The consequence of adding the strip is that the shearline is pushed more than 1/2'' outside the projection of the hull topside and the lip can therefore be wider than 2'' and is thus made more comfortable to sit on. This, I think, is the limit of what you can do at the moment.

From a construction point of view the boat was easier to build because the need to deck it was negated. However, having sailed the boat already this season we have noticed that it's easier to fill it up with water when tacking if we're not careful.

If someone remindes me how to put a photo on the discussion group I'll try and put one of the boat on here.

In summary it would be interesting to see what sort of hull shape one could come up with if the hollows and decking rules were removed but the rise of floor rule retained. As Derek has noted it shouldn't make construction any more onerous in this day and age: perhaps some scope for development, it would be interesting hear other peoples' thoughts particularly those on the technical committee!

Marcus    

[samdoman]

it would be really interesting...it may lead to a boat almost like an international moth for two people?!

[THG]

Marcus,

Any pics of your boat during / after build?  A description can be hard to follow - annotating a pic to show what you mean would be cool  

The RS300 type shape could also be a possibility - not sure how close this is to the rules currently.  I'm not sure many would take a risk and why the Class seems to have only a small number of designs sailed at the top, FF is dominating the new builds now.

THG

[Marcus (Guest)]

I'm not sure that you would want to end up with a moth like boat; as I've said I think it might be worth revisiting the hollows and decking rules to give the designer more freedom above the waterline but if you remove the rise of floor rule as well then there's nothing to stop the boat becoming very narrow underneath and the consequences of this are that the boat would soon become unmanagable!

The best arguments for relaxing the aforementioned rules will, I guess, be based upon possible simplification of construction, developing alternative buoyancy disposition and evolving performance.

Marcus

[Jimbo41]

[quote by=Marcus (Guest) link=Blah.cgi?b=Cool1,m=1196853525,s=10 date=1196863750]if you remove the rise of floor rule as well then there's nothing to stop the boat becoming very narrow underneath and the consequences of this are that the boat would soon become unmanagable!

Marcus [/quote]
If that were the case then surely the designs would self-limit to those dimensions which are not  unmanagable. The designers would  be free to experiment in order to find these limits. Or am I talking garbage as usual?  

Jim.

[Mikey C]

Geoff Camm and myself drew up something very similar, which could have been legal a few years ago (circa 2004) The rules have been tightened up to stop something like this being built.

[greight expectations]

Mike..

Why.. what evil was prevented by the tightening up?  

Roger

[THG]

Weren't the rules changed to prevent a 'Vortex' style 12 with twin 'hulls'??  But Vortex is a real dog in light winds and tacking round.