FAST BUT ORC/IRC OPTIMIZED
Hundreds of hours of optimisation with the best experts and tools result in a highly optimised shape. The strongest invention is the flat stern section with heel. The exit angle of the stern lines when heeled is almost zero, which means a perfect planning shape. And with up to 30 degrees, the keel weight works very effectively - so you carry your sails much longer than usual. CFD calculations have proven that a single rudder and a close eye on the wetted area is best for short and medium distance racing in typical wind conditions around the world. But for long distance racing in strong winds, a twin rudder system is superior. If you are unsure of your intended use, you can choose both systems and switch from single rudder to double rudder and back in a matter of minutes.
The Design
The most difficult issue in good boat design is three-dimensional thinking with heeling and waves. Designing a boat that sails fast when upright is easy. But designing a boat that is fast in all conditions is a real challenge. We checked a big range of hull styles including full “scow” hull shape. The scow style works very well in races with large reaching and running components but can suffer significantly in light air and in upwind conditions with waves. The AEOLOS P30 has sufficient fore-body volume to provide dynamic lift downwind.
The boat is designed for shorthanded sailing with a crew of two, and for medium (up to 500 mile/2-3 days) and short distances. But the boat can be sailed with a crew of 5-6 round the cans like in Cowes, or single hand like Silverrudder. The typical windspeed for Baltic Sea and Solent is 12-14 knots. We tested various modifications of the hull with more rocker and/or more volume in the middle section with different fins and rudders. For all variations we are checking the influence on the rating.
Trimm target is to sail the boat in the constructive/design heel angle of 25-30 degrees. At this angle, the keel bulb generates an enormous uprighting moment, which means that the sails produce a lot of momentum, forward driving power. Upwinds the long rudder leads to a lot more lift due to the 2,5-5 degrees rudder angle. For the crew, this means living on boat which is usually heeled most of the time, starting with 8-12 knots of wind.
A boat desiged to carry a big gennaker. With heeling the weight of the keels becomes more and more useful - if the hull is designed for this purpose.
Fast in Light Wind
In light winds this AEOLOS P30 construction has little wetted area and a very slender waterline. The circular shape in the front section offers maximum volume with small surface when sailing upright.In very light winds it is easy to trim the AP30 to the bow to reduce the wetted area much more (see picture). This has proved to be very successful in our last races.
iterranean. Despite the normal rudder, also downwinds the "4sale" is more benign than, for example, the very similar L30 with twin rudders, although the "4sale" has more sail area and is much wider.
The hull shape is designed for planning when heeled.
The underwater ship designed minimum area in light winds.
Speed in Heavy Wind and Waves
This boat moves through the waves quite smoothly when heeled - the bow section always has the same shape between 0-30 degrees heeling. Hans Genthe, the project manager, has been sailing a BB10 for 25 years with a classic sharp V-shape in the bow. Very fast on flat water, but upwind with windy conditions the boat has an optimal heel angle of 25-30 degrees, which means that the boat hits the waves with the flat side of the V. Awful noisy and uncomfortable. But sailing upright is awful slow.
But the most powerful design aspect here is the flat stern section with heeling. The near to zero exit angle of the stern lines when heeled, means perfect planing shape. And with up to 30 degrees the keel weight is working very effective - due to that you will carry your gennaker or code 0 a lot longer than usual.
Be aware, if you are heeling a lot your yacht will become weather helm, will turn to the windward side, so it´s perhaps necessary to reef or flatten the main to carry the big downwind sails or jib. During the single hand race Silverrudder 2019 Hans Genthe was flying through the field with such a setup (see picture right). Thanks to the V-shaped transom, the rudder allows full control up to 30 degrees angle of heel - according to the simulation, another 5 degrees more than other designs. His Farr280 "4sale" for example was incredibly good-natured with 25 degrees.
FARR 280 is overtaking Luffe 45 with 30knots windspeed during "Nordseewoche"
The flying jib made by ELVSTRØM is a real weapon. The range of use varies from upwind light wind to heavy wind for deep reach courses.
New ELVSTRØM flying jib.
Wind Resistance increases in the Square of Speed!
This means that wind resistance is an important issue for fast yachts upwind. Due to the low, round sheerline and the aerodymamic shaped roof, but especially due to the hull shape in front of the mast, this boat has a considerably lower wind resistance than other yachts in this segment. Especially when heeling, the air flow to the jib has less turbulence. On normal the sheerline causes huge resistance and turbulences, the wider the boat, the more.
At the Aeolos P30 the jib is much more effectively due to more usable profile/area - and this without rating penalty.
If you have to move to the bow in windy conditions you will love this shape, the deck offers a almost horizontal gangway when the boat heels.
By the way: The wide transom brings your crew weight on the useful side and offers a great view to the front. In double handed mode you are sleeping in the carbon tube bunk below deck, only 20-30cm less effective than sitting on deck legs outside. The bunks are mounted relatively high in the boats widest point. They are adjustable, so you can always sleep close at the side of the hull.
The wind resistance of hull and deck is underestimated.
One, Two or Three Rudders?
Even if it is the current trend: double rudders are not automatically better. It depends on the a) shape of the hull and b) the application of the boat:
a) With a wide, flat transom, the rudder must be very far forward, otherwise it would come out of the water when heeling. With the V-shaped transom of this boat, the rudder will stay in the water up to 35 degrees.
b) On a long downwind course with strong winds I would prefer double rudders, but most of us sail inshore around the buoys or medium-distance races with a fairly high upwind component. And very often we sail in rather light winds. At these regattas there are many more starts or situations where you need a "close combat tactic".
c) One good aspect of the AP30: If you are unsure of your intended use, you can choose both systems and switch from single rudder to double rudder and back in a matter of minutes.
Most CFDs studies we know of show that individual rudders are faster under these conditions. The rudder is part of the lateral plan and reduces drift. It must not be too small. Upwinds you should balance the boat so that it's a bit weather helm so the rudder has a small angle of attack ... then it creates lift, like a centreboard in a dinghy like 505 or FD. With this you can pinch off everyone at the start.
Hans Genthe´s personal experience was that the Farr 280 "4sale" is a real weapon, works like a Swiss Army knife and is perfect for the Solent, the Baltic Sea or most conditions in the Mediterranean. Despite the normal rudder, also downwinds the "4sale" is more benign than, for example, the very similar L30 with twin rudders, although the "4sale" has more sail area and is much wider.
Due to the unexpected demand of the Australian market we are offering a AP30 double rudder system (with kickup for UFOs - underwater floating objects). Recommended for long distance offshore racing: this system has advantages compared to a singe rudder at an average wind speed above 20knot upwind/16knot downwind.
The unique rudder design is inspired by the humpback whale flippers, that relies on its superior maneuverability when catching prey. While feeding the humpback whale swims forward and then changes direction continuing by lunging upwards, between 30°-90°angle from the water surface. Seconds later he rolls 180° and attacks its prey at full speed.
A foil with tubercles showing delayed separation at the tubercles, and improve the maneuverability of a vessel but at the same time it increases the resistance. But in high waves it´s an option to improve safe sailing and tolerance for the autopilot, means you carry the big kite longer.
The double rudders increased the resistance in light air and don´t deliver the lift upwinds compared to a single rudder
CFD and Rating optimization
The difference between the first ORC measurement certificate (GPH 550 double hand) and the numbers after the optimization process (GPH 563.3 double hand) without loss of speed shows that the Aeolos P30 design will be very fast.
We have added a wider fin, longer rudder, modified the lines plan, changed the main shape and come to a solution that will be faster upwind, a little slower downwind, even more good natured.
We have some solutions for IRC rating, if there is interest.
ORC optimized sails
The new developed cableless ELVSTRØM A5 Gennaker is based on the design we made for the Farr280.The high performance polyester spinnaker cloth converts every gust in pure speed.
The new developed cableless ELVSTRØM Code 0 fits in the ORC-Rule without penalty.
