search.noResults

search.searching

note.createNoteMessage

search.noResults

search.searching

orderForm.title

orderForm.productCode
orderForm.description
orderForm.quantity
orderForm.itemPrice
orderForm.price
orderForm.totalPrice
orderForm.deliveryDetails.billingAddress
orderForm.deliveryDetails.deliveryAddress
orderForm.noItems
Top recorded speed on the day – 28.6kt. The longest run in stable flight – 1nm. Watching Arkema 3 performing along the La Rochelle beaches in a blustery easterly is much more reminiscent of an AC45-F America’s Cup World Series cat than of the low-flying Imoca foilers. The lively Mini 6.50 foiler is just as likely to leap skywards AC45-stye as it is to crash off its foils into the wave ahead, as was quite common with the larger Imocas with their drag reduction – as opposed to flying – foiling systems. The rotating cassettes for the foils can be seen here (right) along with the articulating boom and twin tackles to adjust rudder rake. On a more ‘mundane’ level, note also the reefable jib (common in French offshore racing) and A-sail as well as the 2:1 tackline to help the solo skipper. This is a small boat rammed with clever thinking


Minis must still remain within a maximum beam of 3m when in port, and also during the start sequence, once the line is crossed the appendages can be extended to a maximum beam of 6.50m (the same as the length of the hull!). Designed by Romaric Neyhousser and


built for skipper Quentin Vlamynck by Lalou Multi, Lalou Roucayrol’s yard (the former Banque Populaire skipper has been racing professionally for more than 30 years and now skippers a Multi50), no900 Arkema 3 is not only innovative in its use of foils. The boat has been built using a new recyclable resin and features two rotating L-foils for lift plus as a mainsail a flexible and reefable two-element wing. Finally, there is the familiar (in the Mini class) telescoping canting keel… The rotating foil solution on Arkema


off completely, but the bow was lifting well above the water.’ This was less relevant in lighter winds


and when VMG sailing. And by definition the lower part of the foil (the tip) always remained immersed, which represented harmful drag at low speeds. ‘Drag at low speed was something we


had assumed,’ says Olivier Mousselon, designer at Mer Forte. ‘The problem is that the foil on 888 is only adjustable in rake, in other words fore and aft. ‘The foil shaft also produced a strong


sideforce to resist leeway: in fact, the boat would often climb to windward and proved difficult to sail deep and fast.’ At the other extreme, DSS-creator Hugh


Welbourn had drawn for a French skipper a very narrow Mini (1.88m beam) with a horizontal 3m foil. Capable of high speeds at broad sailing angles, the boat was short of form stability and most of the time had difficulty reaching the 10kt of boatspeed needed for the foil to kick in. Overall the boat was a disappointment. The new class rule brought in two years ago has changed the paradigm, for while


was initially chosen as a way of meeting the 3m rule in port, ‘without the skipper having to anchor up outside and then remove or instal his big fixed foils,’ explains Neyhousser. When the foils are fully retracted the shafts cross within a few centimetres inside the hull, the head of each foil ending up adjacent to the opposing entry slot in the hull. This rotating foil entry bearing (60° of


rotation is possible) has the additional benefit that it allows the foil shaft to be set vertically when the wind picks up in order to minimise leeway. The axis of shaft rotation is also cleverly offset, so the shaft angle of incidence deliberately changes either side of the neutral position. Low- ered, the profile is angled ‘downwards’ to generate sideforce, but as the foil starts to rotate up then the incidence angle reverses to generate maximum lift. Neyhousser had long ago realised that


for foiling purposes a ‘round nose’ hull (a path opened up in 2010 by David Raison’s Mini no747) would be advantageous. ‘But the choice of this solution is not to


add power to power but because, while all Minis are extremely voluminous for their length, the scow hulls become less asymmetric with heel. As a result, the


immersed foil maintains a more optimal angle with respect to the directional axis of the heeled hull. To say that the sailing mode of Arkema


is ‘flexible’ is an understatement. With the foils sliding in and out of their rotating cassettes, a complex system of pulleys allows them to be adjusted in three different axes: extension, cant and rake. Vlamynck can also change the angle of attack of his appendages by trimming his boat fore and aft using the rudder foils. In flight the Mini is supported on the


leeward foil, on the two rudders, but also on the canting keel (+/-40°). Whereas on the Imoca and VO65 the keel rotation axis is permanently cranked up by a few degrees to generate lift, on Arkema the process advances another step, the rota- tion axis of the keel fin being adjustable by means of raising and lowering the front bearing which allows the so-called keel tilt to be moved between 0° and 8°. The keel also telescopes to ensure maxi-


mum righting moment within the rule, a carbon rod system pushing the lower part of the fin with the bulb outwards by another 30cm when using large angles of keel cant, keeping the draft within the class rules but ensuring the bulb is always extended as far as possible to windward. A critical point with the rotating foils is


keeping out the ocean, which involves a complex system of rigorously tested Neoprene sleeves. This is not a big area of concern with the canting keel which oper- ates within a wet-box that extends above the waterline; but sealing the rotating foil apertures is more demanding and much more critical in the event of seal failure. ‘That is why we monitor this part of the boat so carefully,’ said Neyhousser, ‘and why all our sleeves are now constructed with double-seals for redundancy.’ When we saw Neyhousser this spring


during training at La Rochelle, Arkema 3 was very impressive, capable of reaching very high speeds, producing thundering accelerations, but also undergoing some spectacular stops!


SEAHORSE 31


w


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76  |  Page 77  |  Page 78  |  Page 79  |  Page 80  |  Page 81  |  Page 82  |  Page 83  |  Page 84  |  Page 85  |  Page 86  |  Page 87  |  Page 88