While playing around with calculations for the change in waterline as
the ww hull rises, I came to the conclusion that it didn't change
sufficiently to make much difference before the displacement speed was
well and truly passed. I figured that going narrower and deeper would
not make much difference, if any, to the wetted area. Internal room
can be ok if a flare is added on the outside just above the fully
loaded waterline at the middle and rising at about 5 degrees to taper
about a metre back from the bows, and a significant bevel added on the
inside. This 5 degree angle is a little more than the maximum the bow
depresses on the lw hull before the transom starts to lift. Possibly a
two stepped flare. This would reduce spray, and possibly give a little
lift as it skips across the chop.
I was also looking at the ratios of the hull lengths, and figured I
may as well go to 15m lw, a skinny 10m ww with significant reverse
stem and 1:17 beam /length ratio for both hulls. This would also
reduce the height above the water by 10cm, giving marginally better ww
ability, provided the bows were the same height above the waves.
If I am not worried about frequent awkward trailering or Marina usage,
then the extra length is not much extra hassle and is very little
extra in cost. Basically a Harry at Visionarry length able to carry 1
tonne in the ww hull, and weigh no more than 200kg more than the
12m/9m Harry.
regards,
Robert
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