Sailboat spade rudder Calculation Sheet
U. Mancuso, Jan 13
INPUT DATA Instructions:
HULL PARAMETERS INPUT
1) Fill all the input boxes (blue cells)
Loa (m) 8,00 2) Check the allowable ranges
3) Visualize the results and charts
LWL (m) 7,85 Note: If one of the areas required is missing, input the empirically derived
m LDC (kg) 2000 values.
SA (m2) - sail area, upwind 32,00
Design category (tick one) Empirical Formulas used:
Category A ("ocean") 2
2,65 LWL
3 V 2,7 K v LWL KV
3 2
Category B ("offshore") m LDC
Category C ("inshore")
Category D ("sheltered waters")
category of boats considered suitable to operate in seas with
DEDUCTED VALUES
significant wave heights up to 2 m and a typical steady wind
force of Beaufort Force 6 or less Kv 1,029
fwR (Design category factor) 0,75 V (knts) - design speed 7,67
V (m/s) - design speed 3,95
VMAX (knts) - max speed 11,6
FnMAX (-) - max Froude nr 1,32
Design information
Design n° - Revision nr° 2
Designer - Date 20-gen-12
Boat name Spirit of Freedom Boat owner Mancuso
Design information
Club racer/weekend sailer.
Variation of Dudley Dix's Didi26
Sailboat spade rudder Calculation Sheet
According to ISO/CD 12215-8
U. Mancuso, Jan 13
INPUT DATA Rudder dimensions
Board parameters INPUT Suggested
Type I c
hr (m) - Span 1,27 Ru
b1 (m) - Root chord 0,35
b2 (m) - tip chord 0,2
2
hu
A (m ) - side area 0,39 0,416
h1
b1
(m2) - Geometrical Aspect Ratio 4,10
RL M T
Kb (-) - rudder bending coefficient 0,45 hc
hc (m) - bearing to root 0,04
Zb (m) - Bending arm 0,652 0,604 zB h2
kbhr
A 0,3 c
u (m) - stock to leading edge 0,06
c (m) - middle span chord 0,33 r
hr u
r (m) - Torque arm 0,035
c
Rudder load, ISO
Cr (-) - Max lift coefficient 1,50
F (N) - blade force 3.514
T (Nm) - blade torque 124
M (Nm) - blade bending moment 2.291
b2
Zeq (-) - equivalent bending arm 0,653
Material
Rudder load, GERR (choose one) Al EN 6082
W p (kg) - Water pressure 161 y 280 N/mmq
TM (kgm) - torque 5,7 u 330 N/mmq
BM (kgm) - bending moment 104,7 d 165 N/mmq
CM (Nm) - combinend moment 2055 Ok Km 1,02 -
Results - required stock diameter
- use ISO diameter as design minimim, use GERR diameter for safety factor Check -
Stock diameter, ISO Stock diameter, GERR
Rudder type
Sailboat, spade rudder
(tick one)
d316 (-) - S-steel diameter 51,04 1
Specific mass (kg/mc) 2,70 Sailboat, skeg rudder
dMAX (-) - Stock diameter 52,1 SFMIN (-) - Minimum safety factor 3,34
SF(-) - Safety factor 4,4
dMAX (-) - Stock diameter 51,9
Stiffness check
- calculate flexural rigidity and angular deflection at bottom bearing for stiffness Check -
dMAX (-) 52,0 mm
E bending modulus 71.000 N/mmq
4
IX (mm ) - Moment of Inertia 1.794.540,56
4
IXX (mm ) - area modulus 3,6E+05
EI flexural rigidity at bottom neck 2,5E+10 N/mmq
(deg) - angular deflection 1,68° deg.
(deg) - angular deflection A316 0,64° deg.
(mm) - side deflection at tip 37 mm
Material data
Material y u d E
N/mmq N/mmq N/mmq g/cmc N/mmq
AISI 304 241 565 216,9 8,09 200.000
AISI 316 200 600 180 8,09 200.000
AISI 329 450 750 375 8,09 200.000
AISI 630 720 930 465 8,09 200.000
Aqualoy 22HS 986 986 493 8,14 600.000
Al EN 6082 280 330 165 2,7 71.000
Al Ergal 7075 460 520 260 2,69 71.000
