Page 174 - Theory and Design of Air Cushion Craft

SES transverse dynamic stability 157

Input data
Craft Principal dimensions
Sidewall offsets, LCG, VCG
Bow and stern seal dimensions
Craft dynamic trim curves (Fig 5.21)
Overturning moment (if required)

Generate thrust and resistance curves
v t, v 2, 3 ................... v,,
V
v j=
T= r,, T 2, T 3, .................. T n
also trim moments M R and M T about VCG
T
Define a series of heeling angles 9^9 2,0^....
and associated heeling moments M Tj

At speed V,, assume a series of inner bow and stern drafts t bi, t s!
and initial value for dynamic trim angle a

Calculate air leakage area Determine sidewall buoyancy and restoring moments
for various inner drafts Determine cushion forces and moments
Define forces acting on the seals

Solve the following relationships:
(iterate to equilibrium)
W=f L [r w,r to, t si,t sa, A .]
Q=f [fw,'*».f«.' I0.AJ
PC =f IQ]

Calculate restoring moment at

Output data - for dynamic equilibrium at V,
Cushion pressure, flow rate,
equilibrium inner and outer drafts at craft bow and stern,
equilibrium dynamic trim angles a tj
transverse restoring moment curve,
transverse equilibrium heel angle (if required)

Fig. 4.22 Block diagram for calculating dynamic transverse stability.