Best LCF position for fast craft.

[dmatt45]

Hi All.
I am looking to find the best position for the Longitudinal Centre of flotation, for fast craft. What is the acceptable difference between LCF and LCG whilst the vessel is sitting still on design waterline(acceptable static trim angle). Bearing in mind the need to keep the LCG further aft possibly 70% of DWL from fwd Perp for dynamic trim angles.
Many thanks.
dmatt45

[gonzo]

That depends on the hull design. Also, what do you mean by "fast craft"? The vessel's top speed would make it possible to give you a better answer.

[dmatt45]

Vessel is 12m loa
9.9lwl static
65 knots

[Perm Stress]

12m boat at 65 knots is in pure planing mode. LCF, and any other hydrostatic features, while at rest are completely irrelevant.

[Alik]

You should draw the hull for certain displacement first, and then check other hull factors.
Starting and stucking with too many 'optimum' numbers is not good idea as it will produce ugly 'monster'-looking hull.

LCF for planing craft is of some interest for ride stability and for payload.

[Alik]

LCF for planing craft:
On DLBA website look dynamic stability calculator.
They use center of planing area to evaluate stability of ride. Not LCF, but it is corelated with planing area.