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Saturday, December 29, 2012

A Different Slant

We have received several questions regarding the unusually flared mid sections on Paradox compared to other A Cat designs.

The simple thinking is to push the outer gunwale (hull to deck joint) between the beams as far outboard as possible.
If each hull had vertical topsides (slab sided), the outer gunwales would move inboard as the the hulls are canted.
Since maximum beam is measured as the widest point overall, the gunwales would end up inboard of the turn of the bilge (or more precisely the point where the tangent to the surface is vertical, so somewhere on the radius where the bottom of the hull turns up to meet the topsides).

On Paradox the outboard edge of the deck is at maximum beam with the hulls canted.
This means you are trapezing as far outboard as possible, giving you more leverage and maximising righting moment.

A byproduct of the wider deck is that overall hull stiffness is greater.
Since there is a bit more deck area, deck weight would be slightly greater for a given laminate spec. However the inherent stiffness of the flared shape means that less reinforcement is needed so there is no net weight gain.
In addition, since the inner gunwales are closer together, the trampoline is marginally narrower and hence a bit lighter, offsetting any weight gains in the deck.

Moving aft, topside flare is maintained to dampen pitching: as the stern submerges, the waterplane gets progressively wider, rapidly increasing waterplane area, and offering more support to restore a level attitude.

Keep the questions coming and we will attempt to post on the more frequent ones whenever time permits.

Monday, December 17, 2012


Some close up shots of the new Paradox A Class Cat on the water, snapped by Andrea Francolini.
Detailed reports on the first weeks of testing sessions coming up soon.
This project is definitely 'centre stage' for Carbonicboats now that the summer is here, even though other developments such as RC yachts and UAV airframe work are also coming along nicely.

Wednesday, December 12, 2012

Exploring the Envelope

Not much time behind the desk recently, and for the coming weeks.
After the planning and design phase and a smooth build period, we are now exploring the performance profile of the new A Cat.

Here is our first in-depth discussion of the project outside this blog:

There is a bewildering array of variables to grapple with.
And this is just one of the configurations we plan to test.

Our approach is to quantify as many as is practical and gradually develop a tuning manual to allow customers to dial in fast settings out of the box as a starting point for individualised tuning.

We will post more detail but the short summary is as follows:
The skipper controls trim through fore/aft weight placement.
Foil AoA is controlled by a single line system and rudder foil angle is set 'on the beach'.
The interaction of these three variables is fertile ground for getting the best performance out of the boat.

In addition there are the usual tuning variables such as mast rake, rudder toe-in angle as well as sail trim settings.
Simple enough to explore with a good plan!

Sunday, December 2, 2012

More Machining

Another nice piece of CNC milling for production tooling...