One of the considerations for a sole above the bottom is torsional rigidity. Hulls inevitably transmit torque along their axis and having a defined path for the torque transmission is good design. There may be circumstances requiring the bottom of the hull to form a box beam, which is good for torque transfer from beam to beam or whatever is inducing the toqrue.
A schooner rig HP does not get torque under sail loads in relatively flat water because the heeling moment is coupled directly from mast to beam. However once angled to waves the differential pitching forces on the two hulls induces torque between the beams. If there is no box structure to carry the torque then any openings in the hull between beams will be highly stressed if not suitably strengthened. It may be more economic to make the cabin sole and bottom a box beam to provide a defined torque path. It only needs a torque box in one hull. A hull that does not have openings between the beams is also an effective solution to transmit torque between beams.
The simplest way to think about this is to support the lee hull at both ends and the ww hull at only one end. The unsupported end of the ww hull will droop depending on the ability of the hulls to transmit torque between beams. If stiffness is low there will be a lot of twisting of the beams relative to each other and the unsupported end of the ww hull will droop much lower than supported end.
On 13 Oct 2018, at 6:47 am, '.' eruttan@yahoo.com [harryproa] <harryproa@yahoogroups.com.au> wrote:I cannot see a reason to add a second floor to raise the floor, can you? One wants low weight, cheaper, lighter hull, etc., right?
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Posted by: Rick Willoughby <rickwill@bigpond.net.au>
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