Sail Loading on the Rig, Rig Loading on the Vessel

brian eiland · May 29, 2009

...this thread is a bit of an excerpt from an extensive subject matter I addressed elsewhere. Thought some might enjoy seeing some hi-tech hot rods sailing over in Europe

brian eiland said: ↑

The Boat ‘Is’ the Structure

Who would have ever dreamed that a lake sailing, ultra light-weight, racing catamaran would encounter, and be capable of sustaining rigging loads comparable to those of an America’s Cup boat??

From a recent article in Seahorse magazine, “Alinghi, Birth of a Crazy Boat”, this paragraph emerges, “The boat ‘is’ the structure. These boats are now so complex, and the loads so high, that structural aspects take on a particular high importance: imagine that on a 1.2 ton boat you can reach 23.7 tons of mast compression…levels seen on an IACC design weighing over 24 tons! Also one cable in the substructure is sized at 56 tons…it is amazing that such light boats can produce such enormous loads.” (let alone absorb them, BE)
Alinghi Catamaran
http://www.boatdesign.net/forums/showpost.php?p=98787&postcount=39
….attached PDF

The point is ‘the boat is, or should be, designed as a structure’ to carry the rigging loads. In far too many cases with production vessels and custom vessels this is not the case. Most are concerned with a maximization of the interior layout, and bulkhead placements are supplemental to this interior layout configuration. Yes, care is taken with the placement of the mast and the need to support the compression loads of the mast, but seldom are the shrouds and stays tied to a 'designed substructure’ of the vessel…they are simply and traditionally attached to the outer hull skins and ends of the vessel’s shell.

This ‘flaw’ can be even more of a problem with a multihull vessel. The catamaran platform lacks the ‘backbone’ structure of the traditional keeled monohull, or central hull structure of the trimaran. Yet seldom is there any serious thought given to some sort of supplemental frame structure in these vessels. No wonder we see so much headstay sag. No wonder these boats can not carry a nice masthead genoa. Added to this equation, the shrouds are attached at a ‘shallow angle’ (half that of the forestay), so their aft-pulling capability is limited by both this shallow angle and the 3 point (tri-angled) configuration. Then at their point of attachment to hull sides (skins) there is likely no firm bulkhead backing, just skin. The shell of the hull is being asked to absorb the load, which it does in a ‘forgiving manner’ resulting in more forestay sag. It’s no wonder these vessels can’t carry a decent size headsail.
...continued
Click to expand...

The "SYZ & CO" is a revolutionary hydrofoil catamaran which could become the fastest multihull on Lake Geneva with a view to both beating Lake Geneva speed records and winning its main races, most notably the Bol d’Or Mirabaud.

The hydrofoils are lifting foils placed under the hulls which allow them to rise so that only the foils remain in contact with the water. This substantially reduces the drag in the water, allowing the yacht to achieve far greater speeds than traditional boats.

Contrary to other prototypes which aim solely to beat records in very specific wind speeds, wind angles and wave conditions, the "SYZ & CO" hydrofoil catamaran aims to win races. As a consequence, she must be able to sail fast in all situations.

http://www.syzfoiler.com/projet/concept/index.lbl

..and look closely at the longitudanal supporting structure to maintain rig
tension..... http://www.syzfoiler.com/images/photo/index.lbl ..look under 3D VIEW

brian eiland · May 29, 2009

Boat with NO HULL

The 2009 version of the Mirabaud LX, Thomas Jundt’s foiler has a new hull that favours speed and stability by light wind. Its mast has also been reinforced in order to improve the upwind sailing angle, as well as the reactivity of the boat. Finally, the sensors used to trim the foiler’s flaps have been improved, allowing a better precision whilst sailing. Introduced in 2008 as “the boat with no hull”, the Mirabaud LX has recently proved that this wording could be translated into reality by sailing on its hydrofoils with no buoyancy at all. Thomas Jundt and his team have accomplished this challenge and validated a different and creative way to consider the sport of sailing.

...and check out this YouTube Presentation
http://www.youtube.com/watch?v=Lx6K1PzqnG0

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Sail Loading on the Rig, Rig Loading on the Vessel

brian eiland Senior Member

Attached Files:

SYZ cat foiler.jpg

brian eiland Senior Member

Attached Files:

foiler, no hull 2.jpg