David
Cavitation is not something that only happens above 50 knots. It can be an issue above 20kts if you are not considering it in the design of the foils at the outset.
Also once you have done the polars you will realise there is a difference between lifting the boat, which is a constant force and restraining the lateral force, which varies relative to sail force depending on the point of sailing. That is when you will recognise the problem with a cambered restraining foil.
If you look carefully at the hulls on the large tris you will see they have flat sections. They are intended to plane. There is dynamic lift and it will reduce drag by about 20% over pure displacement mode. This makes them little different to what you will achieve with lifting foils.
Rick
On 15/12/2014, at 10:37 PM, "cruisingfoiler@yahoo.com.au [harryproa]" <harryproa@yahoogroups.com.au> wrote:
With regard to Paul Larsen's craft: I'm aware of the points you make. The foil was the biggest problem. A lot of stuff happens around 50 knots (and Mach 1) that the average foiler doesn't have to think about. The semantic issue was calling it a planing craft, when its a 3-way hybrid. And it foils. Up or down doesn't matter.
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Posted by: Rick Willoughby <rickwill@bigpond.net.au>
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