Sorry Cuz, but you're really off in left field on this one. I wouldn't have described it as Mark does, but every Mac X owner knows what Mark writes of. If you'd driven a Mac, you would too. The issue is undue hydrodynamic lift created across the symmetrical foils. At anything beyond normal sailing speeds, it applies to CB and rudders alike, but especially to the larger, deeper CB. (You would not assess it as a "structural precaution" to avoid motoring at 10 or 12 knots with the mainsail hoisted and sheeted? . . . would you? . . . hope not)!GreatLooperDave wrote:Wouldn't disagree w/your point on handling as the driver. However, that doesn't diminish the structural rationale for MacGregor's policy. After all, few things torque a boat hull worse than swapping ends or broaching under power.
Even at 10 knots, dead ahead, the symmetrical foil sets up vigorous alternating lift across one side or the other. This causes oscillations that constantly redirect the vessel's path. The result is imprecise, unpredictable, potentially dangerous steering. This is far from mysterious, and completely unrelated to the hull, the transom, torsion, or any other structural design element, or failure thereof. The foil is simply causing fully understandable and expected, but undesireable lift to either side. It's not mysterious, not deficient, and certainly not structural in any manner.
This second problem, during turns, is also quite straightforward to understand. The Mac X's hull shape induces a quite natural feeling "powerboat" style of speed turn. The hull leans naturally and with authority into any turn, just as we've experienced on any power runabout. It's quite eerie to feel this when a rig towers 35' above the water, but it's quite solid and predictable. Of course, centrifugal force simultaneously skids any boat slightly to the outside of the turn. Should the board be unknowingly left extended, the boat leans alarmingly outboard because the board deters centrifugal drift, and she "trips" over her board. The towering rig is no doubt exacerbating, but here again, the effects are far simpler than you're (apparently) imagining.
You really need to get a ride. Most dealers will sea-test a brand new boat for only a hundred dollars or so. (P.S. Your deep perception of the rationale for factory policies [or scientific testing] is indeed, truly enigmatic.)
As respectfully as ever,
yer Cuz
