Several years in development, the latest DNA F1 A-Class with its refined Mischa Sails DeckSweeper rig comes delivered off the shelf as a superbly finished ready to race package. The current boat comes with this part-curved (above) mainsheet track as standard, to speed things up when you need to dump power, along with these lifting L-foil rudders (left) which provide maximum lift and control within the A-Class rule-maximum beam
more side force we can manage for a given heeling moment. More side force results in more driving force which results in better VMG (speed and/or angle).
And the effect of lowering the centre of effort can be quite dramatic, even at the scale of an A-Class. If you take a typical total side force from the mainsail of 74.25kg acting at a centre of effort 4m
54 SEAHORSE
above the deck, then for the same righting moment, if the sail force now acts 3m above the deck then lateral equilibrium is now achieved with an increased side force of 4m/3m*74.25kg = 99kg [the driving force moving the boat forward directly correlates with side force assuming the same angle of incidence (trim) of the sail]. For mathematicians among us, we can
also invert this calculation, when we find that lowering the height of the side force is also the same as ‘virtually’ increasing the weight of our helmsman by the same factor of 4/3. So a 90kg helm now enjoys the virtual weight of a 120kg sailor. And, as we know, in a breeze when righting moment matters – particularly upwind – then a big guy is normally faster than a small guy. But of course those extra 30kg are only ‘virtual’ and so the all-up sailing weight remains the same.
GORDON UPTON
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 |
Page 89