Final Report on USSA Pitching Moment project

F i n a l R e p o r t

U S S A P i t c h i n g M o m e n t P r o j e c t

15 October 1992

by

Karl L . ICirkman

Table of Contents

item

ABSTRACT

INTRODUCTION

ORGANIZATIONAL & OPERATIONAL HISTORY

NON - TECHNICAL SUMMARY

TECHNICAL APPROACH

R E S E A R C H ON MEASUREMENT

R E S E A R C H ON A D D E D RESISTANCE

R E S E A R C H ON W A V E SPECTRA

E X P E R I E N C E WITH IMPLEMENTATION

IMPLICATIONS OR RESULTS

RECOMMENDATIONS

APPENDICES

List of Figures

Figure P^g^

Figure 1 - Comparison of IMS Target and Measured Speeds for Anthem 6

Figure 2 - Mark IIB Measuring Machine

J.4

Figure 3 - Comparison of Measured and Predicted Pitch Time

History for L \ C C Model

13

Figure 4 - IMS Base Boat Body Plan for Seakeeping Study

17

Figure 5 - Variation of Added Resistance with L/B

18

Figure 6 - Variation of Added Resistance with DLR

19

Figure 7 - Variation of Added Resistance with LCB

20

Figure 8 - Variation of Added Resistance with L C F

21

Figure 9 - Variation of Added Resistance with Gyradius

22

Figure 10 - Measured and Predicted Resistance for 12-Metre

24

Figure 11 - Measured and Predicted Resistance for Cruiser/Racer

25

Figure 12 - Computed Values and Linear Fit for U B

27

Figure 13 - Computed Values and Linear Fit for DLR

28

Figure 14 - Computed Values and Linear Fit for LCB

29

Figure 15 - Computed Values and Linear Fit for L C F

30

Figure 16 - Computed Values and Linear Fit for Gyradius

31

Figure 17 - Breakdown of Added Resistance for Selkie

32

Figure 18 - Breakdown of Added Resistance for Gaucho

33

Figure 19 - Variation of Added Resistance with Wave Heading

for Fn =0.20

34

Figure 20 - Variation of Added Resistance with Wave Heading

for Fn =0.265

35

Figure 21 - Variation of Added Resistance with Wave Heading

Figure 22 - Variation of Added Resistance with Forward Speed

for Heading of 180-degrees

Figure 23 - Variation of Added Resistance with Forward Speed

for Heading of 160-degrees

Figure 24 - Variation of Added Resistance with Forward Speed

for Heading of 140-degrees

Figure 25 - Variation of Added Resistance with Forward Speed

for Heading of 120-degrees

Figure 26 - Correction Factors for Speed and Heading Effects

on Added Resistance

Figure 27 - Comparative VPP Outputs with and without DELR2

Figure 28 = Locations of Race Course Wave Measurements

Figure 29 - Summary of Wave Observations

Figure 30 - Averaged Wave Records for Three Wmd Strength Bins

Figure 31 - Comparison of Wave Spectra Fit to Measured Data

ABSTRACT

i n w a v e s from s h a p e a n d w e i g h t d i s t r i b u t i o n v a r i a t i o n s .4

T h e work was a c c o m p l i s h e d i n two P h a s e s ;

* P h a s e I was t o i n v e s t i g a t e f e a s i b i l i t y o f r a t i n g w e i g h t d i s t r i b u t i o n v a r i a t i o n s and t o p r o d u c e h a n d i c a p p i n g i n f o r m a t i o n f o r u s e t o s u p p l e m e n t t h e VPP, and

\ Kirkman, Karl L., "Progress Report on U S Y R U Pitching Moment Project", 1 November 1990.

\ "Pitching Moment DELR", memorandum report to ITC by Karl L.Kirkman, 15 April 1991.

* P h a s e I I i n w h i c h a f i n a l measurement m a c h i n e p r o t o t y p e was d e v e l o p e d , and a more r e f i n e d c a p a b i l i t y t o a c t u a l l y r e p r e s e n t added r e s i s t a n c e i n w a v e s was c o m p i l e d . i n p r e d e c e s s o r p r o j e c t s o f t h i s t y p e i t h a s b e e n t r a d i t i o n a l t o t u r n t h e r e s e a r c h r e s u l t s o v e r t o r u l e making b o d i e s f o r i m p l e m e n t a t i o n . To t h e e x t e n t t h a t t h i s i m p l e m e n t a t i o n w i l l r e q u i r e a d d i t i o n a l t e c h n i c a l s u p p o r t from t h e P r o j e c t , t h e T e c h n i c a l C o l l a b o r a t o r s r e m a i n a v a i l a b l e t o a s s i s t i n t h i s work.

INTRODUCTION

ORGANIZATIONAL & OPERATIONAL fflSTORY

The p r o j e c t was a d m i n i s t e r e d w i t h i n t h e O f f s h o r e O f f i c e o f USSA, b u t w i t h s t r o n g o r g a n i z a t i o n a l s u p p o r t and ^"P°^^f^ement from t h e c r u i s i n g C l u b o f A m e r i c a , t h e I n t e r n a t i o n a l T e c h n i c a l C o m m i t t e e , and t h e O f f s h o r e R a c i n g C o u n c i l , The r e s e a r c h was c o n d u c t e d p r i m a r i l y by v o l u n t e e r t e c h n i c a l c o l l a b o r a t o r s , b u t w i t h some f u n d e d r e s e a r c h P e r f o r m e d by o u t s t a n d i n g c o n t r i b u t o r s n o t a s s o c i a t e d w i t h t h e Y^ r i o u s o r g a n i z a t i o n s . The e x p e n s e s w e r e u n d e r w r i t t e n by c o n t r i b u t i o n s by i n d i v i d u a l s , and o r g a n i z a t i o n s . The O f f s h o r e i " ^ . c r u i s i n g C l u b o f A m e r i c a s u p p o r t e d t h e work w i t h s u b s t a n t i a l c S ^ i ? i b u t i o n s w h i c h w e r e s u p p l e m e n t e d by t h o s e o f i n d i v i d u a l y a c h t s m a n . CRAY R e s e a r c h d o n a t e d a b l o c k °f ;^°^P^^t^^^„^^^^^^°

p r o j e c t . The P a r t n e r s h i p f o r A m e r i c a ' s Cup t e c h n o l o g y made a v a i l a b l e t h e k n o w l e d g e f r o m an e x t e n s i v e r e s e a r c h program i n t o s e a k e e p i n g i n c l u d i n g b o t h c o m p u t e r c o d e d e v e l o p m e n t and e x p e r i m e n t s . The f o l l o w i n g i n d i v i d u a l s w e r e t h e p r i n c i p a l T e c h n i c a l C o l l a b o r a t o r s i n t h e r e s e a r c h : R i c h a r d c . McCurdy R i c h a r d S. McCurdy J o h n O'Dea P r o f e s s o r P a u l S c l a v o u n o s , MIT James T e e t e r s K e n n e t h B. W e l l e r James A. McCurdy

NON - TECHNICAL SUMMARY

1. IMS t a r g e t s p e e d s f o r a p a r t i c u l a r y a c h t . Anthem, t a k e n from t h e IMS c e r t i f i c a t e .

3. An i n d i c a t i o n o f t h e m a g n i t u d e o f t h e e x p e c t e d c h a n g e i n s p e e d due t o w a v e s a s computed i n P h a s e I o f t h e P r o j e c t . ii 'A Ci 8.Ö

Anihem 7/12/90 I7KX) to fiDuh

o o o

^5 -nv-as-T»

15^ 40

True Wind Speed. Ku

Figure 1 - Comparison of IMS Target and measured speeds corrected to calm water conditions for the yacht Anthem from the 1990 Hampton Race

T h e s e s a i l i n g d a t a w e r e t a k e n u s i n g a S e a s t a t e L o g g e r

A p p r o a c h

The a p p r o a c h t a k e n was t o make c e r t a i n s i m p l i f y i n g a s s u m p t i o n s e a r l y i n t h e s t u d y w h i c h a r e n o t e d i m m e d i a t e l y b e l o w , t o c o l l e c t l i m i t e d d a t a on r a c e c o u r s e w a v e s a n d t h e n t o s e e w h e t h e r c a l c u l a t i o n s on t h e s i m p l i f i e d b a s i s g a v e i n s i g h t i n t o h a n d i c a p p i n g d i f f e r e n c e s b e t w e e n y a c h t s . I n l i n e w i t h t h e name o f t h e p r o j e c t , t h e i t e m i d e n t i f i e d i n t u i t i v e l y a s t h e d r i v e r t o a d d e d r e s i s t a n c e was w e i g h t d i s t r i b u t i o n ; " p i t c h i n g moment"

The i m p o r t a n t s i m p l i f y i n g a s s u m p t i o n s made a t t h e o u t s e t were: * " P i t c h Moment" c h a r a c t e r o f a y a c h t c o u l d be m e a s u r e d i n s i t u , * The e f f e c t s o f w e i g h t d i s t r i b u t i o n d i f f e r e n c e s on added r e s i s t a n c e i n w a v e s c o u l d be e s t i m a t e d a c c u r a t e l y u s i n g e x i s t i n g s t r i p t h e o r y c o d e s d e v e l o p e d f o r n a v a l s h i p s and a c a l m w a t e r VPP, * H a n d i c a p p i n g c o u l d be e f f e c t i v e by a s s o c i a t i n g a s i n g l e wave wind c o n d i t i o n w i t h e a c h c e r t i f i c a t e w i n d s p e e d We w e r e n o t b e t r a y e d by any o f t h e s e a s s u m p t i o n s .

The work i n P h a s e I o f t h e P r o j e c t was c o n c e n t r a t e d i n t h r e e a r e a s :

- Development o f a p r a c t i c a b l e measurement e x p e r i m e n t ,

- Development o f a z e r o t h o r d e r code f o r added r e s i s t a n c e i n waves, and

- A d j u s t m e n t t o c e r t i f i c a t e h a n d i c a p p i n g i n f o r m a t i o n t o r e p r e s e n t wave e f f e c t s .

T h a t work was c o m p l e t e d i n w i n t e r 1991, and made a v a i l a b l e t o r u l e m a k e r s a t t h a t t i m e . However, t h e f o l l o w i n g u n r e s o l v e d i s s u e s w e r e i d e n t i f i e d a s r e q u i r i n g a d d i t i o n a l r e s e a r c h :

* The B e a s u r e m e n t m a c h i n e was j u d g e d t o be t o o e x p e n s i v e f o r w i d e s p r e a d a c c e p t a n c e ,

and

* The r e s e a r c h h a d shown poor v a l i d a t i o n o f s t r i p - t h e o r y code p r e d i c t i o n methods w i t h p u b l i s h e d e x p e r i m e n t a l r e s u l t s . AS a r e s u l t a P h a s e I I , r e p o r t e d h e r e i n , was u n d e r t a k e n t o c o n f r o n t t h e s e d e f i c i e n c i e s . I n P h a s e I I , t h e P r o j e c t : * I d e n t i f i e d a n d p r o t o t y p e d a minimum c o s t m a c h i n e , * O b t a i n e d t h e r e s u l t s o f a d v a n c e d

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* D e v e l o p e d a new added r e s i s t a n c e module, DELR2 w h i c h c o u l d

The e f f e c t on r a c e r e s u l t s

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The wave s p e c t r a t h a t w e r e d e t e r m i n e d by buoy m e a s u r e m e n t s t o a p p l y t o t y p i c a l r a c e c o u r s e s show more wave e n e r g y i n l i g h t a i r S o S d i t i o n s ' ^ t h a n w o u l d be a s s o c i a t e d w i t h t h e w i n d / l o n e The r e s e a r c h shows t h a t t h i s i s c o n s i s t e n t w i t h e f f e c t s o f t h e wakes o f p a s s i n g v e s s e l s , and t h e i m m a t u r e n a t u r e o f t h e w a v e s from ? n c r e a s i n g ^ w i n d s f r e q u e n t l y e n c o u n t e r e d . However, t h e c o n s e q u e n c e t o h a n d i c a p p i n g i s t h a t d i f f e r e n c e s i n p e r f o r m a n c e o f y a c h t s w i l l be s u b s t a n t i a l i n l i g h t a i r e v e n t h o u g h one n o t f a m i l i a r w i t h t h e wave d a t a m i g h t n o t e x p e c t t h i s t o be t h e c a s e . u n c e r t a i n t i e s i n A p p l i c a t i o n P a r t o f any r e s e a r c h i s t o u n d e r s t a n d t h e p o t e n t i a l w e a k n e s s e s o f t h e r e s u l t s . 1. A l i k e l y u n c e r t a i n t y i n a p p l y i n g t h e r e s e a r c h i s r e l a t e d t o t h e p r a c t i c a l r e q u i r e m e n t t o u s e a z e r o t h o r d e r ^ode t o p r e d i c t added r e s i s t a n c e , and t o n e g l e c t some c o m p l e x i t i e s o f t h e u n s t e a d y f l o w and d y n a m i c s . We b e l i e v e t h a t t h e z e r o t h o r d e r a p p r o a c h i s r o b u s t enough t o m i n i m i z e t h e o p p o r t u n i t y f o r r u l e b e a t i n g f o r now. I f i t becomes n e c e s s a r y t o i n t r o d u c e a more c o m p l e x ^ n o f ^ l o j p e r f o r m a n c e , t h e knowledge e x i s t s t o do s o . The a b i l i t y t o b l e n d s a i l i n g d a t k r o u g h w a t e r e f f e c t s w i t h VPP p r e d i c t i o n s s u c h a s i n F i g u r e 1 s h o u l d e n c o u r a g e t h e n o t i o n t h a t t h e s i m p l i f y i n g a s l u m p t i o n s p r e d i c t d i f f e r e n c e s c o r r e c t l y , and seem t o g e t a p p r o x i m a t e m a g n i t u d e s a b o u t r i g h t . 2 An a d d i t i o n a l u n c e r t a i n t y w i l l i n e v i t a b l y a r i s e r e l a t e d t o t h e d ; t ^ i n a t ! o n o f g y r a d i u s v a l u e s . U n t i l a p r a c t i c a b l e ^ l a c h i n e i s i n h ^ d and we h a v e e x p e r i e n c e w i t h m e a s u r i n g on a p r o d u c t i o n b a s i s i t i s i m p o s s i b l e t o p r e d i c t a l l t h e p o s s i b l e p a t h s f o r e S i o i t a t i o n ^ b u f t h i s must L w a t c h e d c l o s e l y - J ^ ^ J : - " J ^ ^ n r - e n a r a t i o n o f a y a c h t f o r measurement does n o t a l l o w f o r S a n i p S a i ? o n o f t h e ^ g y r a d i u s measurement i n a manner t h a t d e f e a t s t h e a d d e d r e s i s t a n c e p r e d i c t i o n .

3 A t some t i m e , i t may be n e c e s s a r y t o a d j u s t t h e a s s u m e d wave s p e c t r a and add o f f - w i n d added r e s i s t a n c e ( w h i c h i s p r o b a b l y n e g a S v 4 ) ? o t S e VPP p r e d i c t i o n scheme t o h a n d l e s u r f i n g p e ? f o r m a n c e o f l i g h t e r y a c h t s . T h e r e i s no r e a s o n t o e x p e c t t h a t t S e c o d e s u s e d t o d a t e w o u l d n o t p r e d i c t t h i s a s p e c t o f added r e s i s t a n c e p r o p e r l y , b u t no e x p e r i m e n t a l d a t a i s i n h a n d t o v a l i d a t e s u c h a p r e d i c t i o n .

TECHNICAL APPROACH

c e r t a i n c r i t i c a l t e c h n i c a l d e f i c i e n c i e s

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l i m i t S l o n l h a v e d i s c o u r a g e d t h e i n t r o d u c t i o n o f t h x s c a p a b i l i t y

i n t o h a n d i c a p p i n g r u l e s u n t i l now:

* T h e i n a b i l i t y t o p r a c t i c a b l y measure minute d i f f e r e n c e s w e i g h t

e x i s t i n g y a c h t s ,

* L a c k o f d a t a r e g a r d i n g d e t a i l s wave c o n d i t i o n s t o b e expected f o r

t y p i c a l r a c e c o u r s e s ,

* A l a c k o f v a l i d a t i o n o f seakeeping computer codes f o r s a i l i n g

y a c h t h u l l s .

* W i t h t h e develcp-nente i n « " ^ f f ^ r a " " y e ' = h t " m , c o S ? f be

c a n a b i l i t v t h e p i t c h moment o f i n e r t i a o f a y a c n t , l y y ,

S e a s S r e d i n S e S a t e r by a reasonable measuring d e v i c e .

t o p r o d u c e r a t i n g c e r t i f i c a t e s , * D i r e c t * s u b s t i t u t i o n i n t o a VPP o f added r e s i s t a n c e " * would p r o v i d e c o r r e c t h a n d i c a p p i n g r e s u l t s ; t h a t i s , n e g l e c t i n g u n s t e a d y e f f e c t s on t h e h u l l a n d r i g , * T u n i n g o f t h e r e s p o n s e o f a y a c h t t o a p a r t i c u l a r wave s p e c t r a w o u l d n o t d o m i n a t e o v e r a l l h a n d i c a p p i n g t o t h e e x t e n t t h a t a n a d d i t i o n a l h a n d i c a p p i n g v a r i a b l e : s p e c t r a l c o n t e n t , w o u l d be r e q u i r e d t o h a n d l e w e i g h t d i s t r i b u t i o n e f f e c t s .

In Phase I, an even more restrictive assumption was made and validated: two additional conditions: head seas and upright hull form.

RESEARCH ON MEASUREMENT

* T h e m e a s u r e m e n t s y s t e m s h o u l d b e a b l e t o d e t e c t d i f f e r e n c e s e q u a l t o "one man on t h e bow", a n amount p e r c e i v e d by s a i l o r s t o a f f e c t p e r f o r m a n c e i n waves by a d i s t i n g u i s h a b l e amount, * T h e m e a s u r e m e n t s y s t e m s h o u l d i n c l u d e s u f f i c i e n t i n t e g r a l d a t a q u a l i t y a s s u r a n c e f e a t u r e s t o m i n i m i z e t h e o c c u r r e n c e s when r e m e a s u r e m e n t w o u l d be r e q u i r e d , * T h e t a r q e t c o s t o f t h e measurement s y s t e m was s e t a t l e s s t h a t $ 5 , 0 0 0 . 0 0 ^ , w i t h a d e s i r e t h a t i t b e m i n i m i z e d c o n s i s t e n t w i t h t h e o t h e r c o n s t r a i n t s , and * T h e p i t c h m o t i o n a n a l y s i s a t t h e t i m e o f m e a s u r e m e n t c o u l d b e a d e q u a t e l y m o d e l e d by a s i m p l e damped s p r i n g - m a s s s y s t e m . T h e s e s p e c i f i c a t i o n s w e r e s a t i s f i e d by t h e m a c h i n e p r e v i o u s l y r e p o r t e d by M c C u r d y S a n d s u m m a r i z e d i n R e f e r e n c e 1. T h i s m e a s u r e m e n t system' was d e s i g n a t e d a P i t c h o m e t e r .

5 This cost was agreed at the ITC meeting in the fall of 1991 to be exclusive of computer hardware on the basis that measurers could be expected to possess a PC-type machine.

^ McCurdy, Richard S.," Feasibility Study of the Measurement of the Mass Moment of Inertia in Pitch for Cruiser/Racer Yachts", NESYS, 1990.

I n d e e d , i t was e x p e c t e d t h a t t h i s P i t c h o m e t e r c o u l d be p r o d u c e d i n q u a n t i t y f o r a p p r o x i m a t e l y $3,000.00. However, c o n c e r n t h a t t h e c o s t i m p a c t o f m a k i n g s u c h a machine a v a i l a b l e t o e a c h m e a s u r e r a r o s e a f t e r c o m p l e t i o n o f t h i s d e v e l o p m e n t . A c c o r d i n g l y , t h e p r o j e c t t h e n s p e n t s i g n i f i c a n t e f f o r t a t t e m p t i n g t o i d e n t i f y a l e s s c o s t l y s y s t e m . I n p a r t i c u l a r , d e v e l o p m e n t o f m i c r o - e l e c t r o n i c b a s e d i n s t r u m e n t a t i o n was i n v e s t i g a t e d b a s e d upon p r e l i m i n a r y i n d i c a t i o n s t h a t s u c h a s y s t e m m i g h t be p r o d u c e d i n q u a n t i t y f o r a f r a c t i o n o f t h e c o s t , ex d e v e l o p m e n t c o s t s . U n f o r t u n a t e l y , t h i s a d v a n c e d t e c h n o l o g y t u r n e d o u t t o be i n s u f f i c i e n t l y m a t u r e a t t h e t i m e f o r i n t r o d u c t i o n . F o r P h a s e I I , a number o f a l t e r n a t i v e P i t c h o m e t e r s were s u r v e y e d , and a c o n c e p t s e l e c t e d f o r r e f i n e m e n t w h i c h was d e s i g n a t e d Mark I I B . T h i s c o n f i g u r a t i o n i s shown i n s c h e m a t i c form i n F i g u r e 2. The u p p e r p o r t i o n o f t h e F i g u r e shows t h e s e t u p f o r l o n g i t u d i n a l i n c l i n i n g , and t h e l o w e r p o r t i o n t h e s e t u p f o r dynamic p i t c h i n g .

P r o t o t y p i n g o f t h i s P i t c h o m e t e r c o n c e p t was u n d e r t a k e n i n S p r i n g 1992 t o t h e f o l l o w i n g s p e c i f i c a t i o n :

* B a s e d upon s i m p l e damped s p r i n g mass s y s t e m w i t h c h i r p e d f r e q u e n c y v a r i a b l e ,

* Heave m o t i o n i g n o r e d ( b a s e d upon e x p e r i e n c e from Phase I r e s e a r c h ) ,

* T r a d i t i o n a l l o n g i t u d i n a l i n c l i n i n g t o g e t p i t c h s t i f f n e s s was i n t r o d u c e d ,

* P i t c h m o t i o n t i m e h i s t o r y was assximed s u f f i c i e n t , and f o r c e a t t i m e o f r e l e a s e was d e l e t e d from s y s t e m , * E r r o r b u d g e t c o n s i d e r a t i o n s i n d i c a t e d t h a t i n c l i n i n g w e i g h t s s h o u l d be m e a s u r e d on an e l e c t r o n i c d i g i t a l s c a l e . W a t e r bags were p r o p o s e d t o d e a l w i t h l a r g e r w e i g h t s n e c e s s a r y t o l o n g i t u d i n a l l y i n c l i n e l a r g e y a c h t s , , and t h e a b i l i t y t o a c c o m p l i s h t r a n s v e r s e i n c l i n i n g u s i n g same s y s t e m was p r o v i d e d . McCurdy t h e n d e v e l o p e d s u c h a m a c h i n e b a s e d upon an i n c l i n o m e t e r u t i l i z i n g t h e i n s t r u m e n t m e t e r b a l a n c e p r i n c i p l e , and

Tilt Portable Gauge computer

Figure 2 - Mark IIB Measuring Machine

l a t e r s e c t i o n of t h i s r e p o r t .

u n d e r t e s t by PACT f o r o t h e r r e s e a r c h . The p u r p o s e o f t h e s e e x p e r i m e n t s w a s t o p r o v i d e d a t a w h i c h e x a c t l y e m u l a t e d a p i t c h o m e t e r o u t p u t s i g n a l s o t h a t a d v a n c e d c o m p u t e r p r e d i c t i o n c o d e s d e v e l o p e d b y S c l a v o u n o s c o u l d b e u t i l i z e d t o v a l i d a t e t h e a s s u m p t i o n t h a t a g y r a d i u s c o u l d b e e x t r a c t e d from t h e p i t c h o m e t e r o u t p u t . T h e r e s u l t s o f t h i s a n a l y s i s , p r e s e n t e d b y S c a l v o u n o s t o t h e I T C a t t h e f a l l 1992 m e e t i n g i n d i c a t e t h a t t h e P i t c h o m e t e r s i g n a l c a n i n d e e d b e t r a n s l a t e d a c c u r a t e l y t o a v a l u e o f g y r a d i u s f o r t h e y a c h t . F i g u r e 3 shows a c o m p a r i s o n o f t h e p r e d i c t e d a n d m e a s u r e d t i m e h i s t o r y o f p i t c h a n g l e a s p r e s e n t e d b y S c a l v o u n o s . I n f a c t , a d d i t i o n a l r e s e a r c h and d e v e l o p m e n t o f s i g n a l p r o c e s s i n g h a s a l r e a d y b e e n i n v e s t i g a t e d w h i c h p r o m i s e s t o a l l o w e x t r a c t i o n o f t h e g y r a d i u s v a l u e . I n p r a c t i c e , t h i s more e l e g a n t p r o c e s s i n g i s e x p e c t e d t o b e made a p a r t o f t h e p r o c e s s i n g o f d a t a f o r p r o d u c t i o n o f s a c e r t i f i c a t e b y t h e n a t i o n a l a u t h o r i t i e s r a t h e r t h a n b e i n g embedded i n t o t h e P i t c h o m e t e r s o f t w a r e , b u t t h e v a l i d i t y o f t h e P i t c h o m e t e r a s s u m p t i o n s i s c o n f i r m e d by t h e r e s u l t shown. 0.0100

I ' '

T i m e Fseel

Figure 3 - Comparison of Measured and predicted Pitch Time History for lACC Mode

^. Sclavounos, Paul D., "Radius of Gyration Identification from Pitch Decay

Measurement and Theoiy", ITC, 25 September 1992.

RESEARCH ON ADDED RESISTANCE

The r e s e a r c h i n t h i s a r e a was p r i m a r i l y c o n d u c t e d by P r o f e s s o r P a u l s c l a v o u n o s , o f MIT, and James T e e t e r s . However, s i g n i f i c a n t c r e d i t m u s t go t o PACT f o r i m p o r t a n t u n d e r l y i n g f u n d a m e n t a l ? e S e a r c h i n c l u d i n g b o t h e x p e r i m e n t s and . f ^ t i m a t m g methods P r o f e s s o r S c l a v o u n o s b r i e f e d t h e I T C i n d e t a i l on h i s work a t t h e S e p t e ^ e r i s s f m e e t i n g , and t h e t e c h n i c a l d e t a i l s o f h i s w o r k w i l l be r e p o r t e d ^ a t t h e f o r t h c o m i n g 1993 C S Y S . A t t h e s u b m i s s i o n o f t h e r e p o r t on P h a s e I o f t h e r e s e a r c h , t h e need t o p u r s u e added r e s i s t a n c e c a l c u l a t i o n s w i t h more a d v a n c e d t e c h n i q u e s was i d e n t i f i e d a s r e q u i r i n g f u r t h e r r e s e a r c h T h i s c o n c l u s i o n was b a s e d upon t h e p o o r l e v e l o f c o r r e l a t i o n b e t w e e n p u b l i s h e d model t e s t d a t a on added r e s i s t a n c e and " s t r i p t h e o r y c o d e s f o r e s t i m a t i n g added r e s i s t a n c e ; t h e P r e d i c t i o n s d^ci n o t a g r e e w i t h t h e model d a t a , b u t e v e n more i m p o r t a n t , t h e d i s c r e p a n c i e s c h a n g e d w i t h h u l l t y p e .

T h i s s i t u a t i o n l e d u s t o s u s p e c t t h a t any P r e d i c t i o n i n v o l v i n g h u l l form d i f f e r e n c e s w o u l d be q u e s t i o n a b l e , and t h e DELR module p r e s e n t e d a t t h a t t i m e was s u i t e d o n l y f o r p r e d i c t i n g t h e e f f e c t s o f a w e i g h t d i s t r i b u t i o n change f o r a y a c h t .

F o r t u n a t e l y , t h e P a r t n e r s h i p f o r A m e r i c a ' s Cup T e c h n o l o g y (PACT) S o s e t o make s e a k e e p i n g one o f i t ' s p r i o r i t y P r o j e c t s f o r r e s e a r c h , and t h e r e s u l t s o f t h i s r e s e a r c h a r e now a v a i l a b l e f o r h a n d i c a p p i n g p u r p o s e s .

PACT c h o o s e t o f o s t e r d e v e l o p m e n t o f a d v a n c e d s e a k e e p i n g p r e d i c t i o n methods by p u r s u i n g b o t h ^-D and 3 D ^e^^^^^ a^^^^ p r o v i d i n g e x p e r i m e n t a l d a t a on m o t i o n s and added r e s i s t a n c e of a ? a c h t h u l l c o n d u c t e d t o a v e r y h i g h s t a n d a r d o f e x p e r i m e n t a l u n c e r t a i n t y .

P r o f e s s o r S c l a v o u n o s t h e n u t i l i z e d one o f t h e s e c o d e s : SWAN, t o p e r f o r m a p a r a m e t r i c s t u d y o f a d d e d r e s i s t a n c e f o r a n IMS b a s e

«. Sclavounos, Paul D., and Nakos, D.E.," Seakeeping and Added Resistance of lACC

Yachts by a Three-Dimensional Panel Method", to be presented t at CSYS

1993.

b o a t , F i g u r e 4, a n d p r e s e n t e d t h e r e s u l t s o f t h a t s t u d y t o t h e I T C a t t h e F a l l m e e t i n g i n Newport.

^4.000

-a.ooo -5.000 4.000 .3.000 -2.000 -1.000 0.000 1.000 2.000 3.000 4.000 5.000 8.000 7.000 8.000

Figure 4 - IMS Base Boat Body Plan for Seakeeping Study

H i s work c o n s i s t e d o f p e r f o r m i n g e x p l o r a t o r y c a l c u l a t i o n s on t h e b a s e h u l l t o i d e n t i f y a s e t o f p a r a m e t e r s w h i c h d o m i n a t e d t h e a d d e f ? e s ? s i a n c : o f t h e t^ype, and t h e n c o n d u c t i n g co-P-tat^^^^^^ f o r s y s t e m a t i c v a r i a t i o n s o f Length-Beam R a t i o L / B ) , F i g u r e 5, d i s p l a c e m e n t - L e n g t h R a t i o , F i g u r e 6 5;°"9itu^^^^^^^^

B u o y a n c y L o c a t i o n ( L C B ) , F i g u r e 7, l o n g i t u d i n a l C e n t e r o f F l o t a t i o n L o c a t i o n ( L C F ) , F i g u r e 8, a n d g y r a d i u s . F i g u r e 9.

' Sclavounos Paul D.," Parametric Study of Added Resistance of IMS-40 Base Boat with'3-D Panel Code SWAN ITC, September 1992.

VARIATION WITH LENGTH-TO-BEAM RATIO

VARIATION WITH LCB

OJ

<

Q.

0.30 =

0.20 h

0.10 h

0.00

T h e s e s e n s i t i v i t i e s w e r e t h e n u s e d a s d e s c r i b e d n e x t t o p r o d u c e a n i m p l e m e n t a t i o n o f t h e added r e s i s t a n c e e s t i m a t o r i n t h e VPP.

A t t h e same t i m e t h a t h e p r o d u c e d t h e h u l l forin and w e i g h t d i s t r i b u t i o n s e n s i t i v i t i e s , S c l a v o u n o s a l s o p r o v i d e d s e n s i t i v i t y d a t a f o r added r e s i s t a n c e w i t h f o r w a r d s p e e d , and a s a f u n c t i o n o f h e a d i n g r e l a t i v e t o t h e w a v e s . T h e s e w e r e a l s o i n c o r p o r a t e d by T e e t e r s a s d e s c r i b e d b e l o w . A t t h e o u t s e t o f t h i s d i s c u s s i o n o f a d d i n g s e a k e e p i n g t o t h e e x i s t i n g VPP, i t s h o u l d be n o t e d t h a t t h e r e e x i s t s w i t h i n t h e p r e s e n t VPP r e s i s t a n c e f o r m u l a t i o n some s o r t o f a c c o u n t i n g f o r added r e s i s t a n c e i n w a v e s , a l b e i t i n a n i m p l i c i t f o r m . I n s u p p o r t o f t h i s n o t i o n r e c a l l t h a t : * T h e t a r g e t s p e e d s p r o d u c e d by t h e VPP match s a i l i n g e x p e r i e n c e s u f f i c i e n t l y w e l l t o be u s e f u l i n t u n i n g a n d m o n i t o r i n g p e r f o r m a n c e , and * A t t e m p t s t o compare model t e s t r e s i s t a n c e d a t a w i t h VPP p r e d i c t i o n s f o r t h e same h u l l s h a v e c o n s i s t e n t l y shown t h a t t h e VPP o v e r p r e d i c t s c a l m w a t e r r e s i s t a n c e . E x a m p l e s o f t h i s d i f f e r e n c e a r e shown i n F i g u r e 10 f o r a 1 2 -M e t e r a n d F i g u r e 11 f o r a c r u i s e r / r a c e r .

UPR^&HT R E S I S T B W C E l t * . v ^ t u . B W ^

IZ METER •

I-/

CONV. Keel. 7

"TT'

. j i l - : i ^ : I . M.S. ( S ^ S LPf^^

a

-rre«- 2.SOT Cw=

ad'*-©

r 6

/

/

&

I t s h o u l d a l s o be n o t e d t h a t one o f t h e r e a s o n s t h a t P h a s e I r e s u l t s w e r e p r o d u c e d i n t h e form o f t i m e a l l o w a n c e d i f f e r e n c e s w a s ^ l w n f n a d e i a c i e s i n t h e . VPP r e s i s t a n c e f o r m u l a t i o n a n d an e x o r e s s e d c o n c e r n a t t h a t t i m e t h a t t h e i m p o s i t i o n o f a new c ^ p o n e n ? o f R e s i s t a n c e i n t o t h e VPP d i r e c t l y w o u l d <^^f^oY^e a n o a r e n t u t i l i t y o f t h e t a r g e t s p e e d s m u s e . I t was e x p e c t e d t h a t S e s e m i g J t be^ r e c t i f i e d by t h e t i m e P h a s e I I r e s u l t s w e r e a v a i l a b l e by i m p r o v e m e n t s i n t h e VPP c a l m w a t e r r e s i s t a n c e ? o m u S t ? o n 7 b u t t h i s h a s p r o v e n t o b e a n o p t i m i s t i c a s s u m p t i o n . A c c o r d i n g l y , t h e DELR2 code p r e s e n t e d h e r e i n i s s t r u c t u r e d t o be u s e d i n a d i f f e r e n c e mode a t t h e o u t s e t , b u t c a n a l s o b e u s e d t o p ? e d i c ? a

ï

; f n

? ï

? a t i v e

Teeters, James," Implementation Study of Added Resistance for IMS Handicaps",

rrC, September 1992.

INT{R(w)*S(w)} VS Length/Beam

-5.00E-04 2.500

INT{R(w)*S(w)} VS Length/Disp 4.00E-03 3.S0E-03 3.00E-03 2.50E-03 2.00E-03 1.50E-03 1 .OOE-03 5.00E-O4 O.OOE+OO 0 Ï I M

I

₃

2

r

INT{R(w)*S(w)}v8LCB Z50E-03 iOOE-03 1.S0E-03 1.OOE03 4 -5.00E-04 o.oo&;oo 500 .510 .520 .530 .540 .550 .560 .570 LCB

I N T { R { w r S ( w ) } v 8 L C F

.590 .600 .610 .620

2.00E03 S.00&O4 o.nf)F,-=flo ,10

_/IU

.20 .21

F o r a s a m p l e y a c h t : S e l k i e . F i g u r e 17 shows a breakdown o f t h e added r e s i s t a n c e components r e l a t i v e t o a b a s e b o a t f o r a r a n g e o f w i n d s p e e d s . I n t h i s c a s e , Selkiê w o u l d b e « ^ ^ ^ ^ e d t o h a v e 18.27 pounds o f added r e s i s t a n c e more t h a n t h e b a s e b o a t i n 1° ^ ° ^ s o f VTW, o f w h i c h t h e l a r g e s t components a r i s e b e c a u s e o f h e r assumed g y r a d i u s a n d h e r l e n g t h - b e a m r a t i o , L / B . Test: selkie I, B Disp LCB LCF Gyr 31.41 10.13 20427 .5325 .543B 7.55 BASE Gyr/L .240 UB 3.101 UD 97.1 LCB .5325 LCF .5439 2pGL 4022.84

Param. d-Gyr d-UB d-UD uLCiJ Value .22 3.330 128 .534 .584

ARct 1.80E.03 1.54E-03 1.54E-03 1.S4E-03 1.S4E-03 Slope 1 315.03 8.53E-Oa g.5eE-03 -3.38E-03 Slope

Vi d-Gyr d-UB d-UD d-LCB d-LCF delta 6 8.82 7.41 -4.58 -.35 1.84 10.00 ft e.oo 0.88 -8.07 -.48 2.18 14.82 10 11.38 12.34 -7.59 -.58 2.73 18.27 12 13.84 14.81 -9.11 • 69 3.27 21.92 14 15.91 17.28 -10.83 -.81 3.82 25.58 10 18.18 19.75 -12.15 -.92 4.37 29.23 10 20.48 22.22 -13.87 •1.04 4.gi 32.88 20 22.73 24.89 -15.18 -1.15 5.48 38.54

I n c o n t r a s t , a y a c h t l i k e Gaucho m i g h t be e x p e c t e d t o h a v e l e s s added r e s i s t a n c e t h a n t h e b a s e b o a t , a s s u m i n g a low g y r a d i u s , and a l o w l e n g t h - b e a m r a t i o when h e e l e d . H e r e x a m p l e i s shown i n F i g u r e 18 f o r a h y p o t h e t i c a l s e t o f l i n e s , w h e r e i t i s i n d i c a t e d t h a t s h e m i g h t h a v e 10.16 pounds l e s s added r e s i s t a n c e t h a t t h e b a s e b o a t i n 10 k n o t s VTW. Test: Gaucho L B Disp LCB LCF Gyr , 37.85 ;,S' 10 19382 J81B .6015 7.57 BASE Gyr/L .200 Lm 3.785 UD 179.1 LCB .5818 LCF .8015 2pGL 4847.4

Panm. cl-Gyr d-U8 (l-l/O d-LCB (J.I.CP Value .22 3.330 128 .534 .564

ARcf 1.80E-03 1.54E-03 1.&4E-03 1.S4E-03 1.54E-03 Slope 1.30i;.02 .1.34U.03 o.ssa.oo 0.a0t:.03 •3.3013.03 Slope

Vi (! Byr d-UB d-LTD d-LCB d-LCF delta 0 -«.07 -17.71 10.07 13.29 -3.68 -8.10 8 -10.78 -23.61 13.43 17.72 -4.01 -8.13 10 -13.45 -29.52 18.79 22.15 •fl.14 •10.18 VA -18.14 -35.42 20.15 28.58 -7.38 -12.19 14 -18.83 -41.32 23.50 31.01 -8.59 -14.22 10 -21.51 -47.23 28.86 35.44 -9.82 -16.25 IB -24.20 •53.13 30.22 39.87 -11.04 -18.29 20 -28.89 -59.03 33.58 44.30 -12.27 -20.32

Figure 18 - Breakdown of Added Resistance for Gaucho

The c o r r e c t i o n s shown above a r e f o r t h e c a s e o f h e a d s e a s , and a n o m i n a l s p e e d . T e e t e r s t h e n h a s p r o d u c e d c o r r e c t i o n f a c t o r s t o a p p l y t o t h e s e f i g u r e s t o a l l o w f o r t h e a c t u a l b o a t s p e e d and h e a d i n g from t h e VPP s o l u t i o n .

i n o r d e r t o p r o v i d e f o r t h e s e f e a t u r e s , S c l a v o u n o s p r o v i d e d a d d i t i o n a l c a l c u l a t i o n s a s a f u n c t i o n o f wave h e a d i n g f o r t h r e e F r o u d e Numbers, F i g u r e s 1 9 - 2 1 , and f o r d i f f e r e n t F r o u d e Numbers a t f i x e d h e a d i n g s , F i g u r e s 22 - 2 5 .

VARIATION OF ADDED RESISTANCE WITH WAVE HEADING

FrNo=0.265

Figure 22 - Variation of Added Resistance with Forward Speed for Heading of

180-degrees

VARIATION OF ADDED RESISTANCE WITH FORWARD SPEED

<

P

= 160°

/

Figure 23 - Variation of Added Resistance with Forward Speed for Heading of

160-degrees

Figure 24 - Variation of Added Resistance with Forward Speed for Heading of

140-degrees

VARIATION OF ADDED RESISTANCE WITH FORWARD SPEED

= 120°

Figure 25 - Variation of Added Resistance with Forward Speed for Heading of

120-degrees

T e e t e r s t h e n f i t t e d t h e s e p r e d i c t i o n s w i t h c o r r e c t i o n f a c t o r s t o a c c o u n t f o r s p e e d a n d h e a d i n g r e l a t i v e t o p r i n c i p l e wave d i r e c t i o n , F i g u r e 26, a n d wave s p r e a d i n g .

AR Integral {R(w) • S ( w | ' 2/pl'cos(u)*2} vs Froude Number (Fits use Cosine aistnDution|

1.20E-03 1.OOE-03 0.006.01 O.uüE.OÖ 4.0CE-04 iOOE-04 O.OOE+00 ARnmitctiesdata B«140<1, Fn».325 £3— f=n.200 Fn ,285 - Fn .325 -a— • .200 o--- .285 . Ö— .325 .._o... • .350 180 170 180 150 140 130 120 110 100 80 II—ding(110; H—da—«>

F i n a l l y , a c o m p a r i s o n o f VPP o u t p u t s f o r a s m a l l t e s t f l e e t b e f o r e a n d a f t e r added r e s i s t a n c e e f f e c t s a s computed by DELR2 i s shown i n F i g u r e 27.

Polar Deltas, Wave Added Resistance, Upwind VMG Solutions (negative is faster) MIMIB CRESCENDO WHISKERS SELKIE CYNOSURE QUINTESSENCE KROPP DUSTER WONDER GAUCHO HOLGER OANSKE MIMIB CRESCENDO WHISKERS SELKIE CYNOSURE QUINTESSENCE KROPP DUSTER WONDER QAUCHO HOLGER DANSKE evMOu C U u 1.x A- VbaM 8NC40

n.nm

n.8m

Figure 27 - Comparative VPP Outputs with and without Added Resistance Module

D E L R 2

I t s h o u l d be n o t e d t h a t t h e s e r e s u l t s a r e b a s e d upon a s t a n d a r d g y r a d i u s d e t e r m i n e d a s a f u n c t i o n o f o v e r a l l l e n g t h , and t h a t d i f f e r e n c e s b e t w e e n y a c h t s s h o u l d be e x p e c t e d t o v a r y when

RESEARCH O N WAVE SPECTRA

The r e s e a r c h i n t h i s a r e a was c o n d u c t e d p r i m a r i l y by R i c h a r d C. McCurdy.

A t t h e o u t s e t o f t h e p r o j e c t , i t was c l e a r t h a t we u n d e r s t o o d l i t t l e a b o u t r a c e c o u r s e w a v e s . A c c o r d i n g l y , a buoy c a p a b l e o f m e a s u r i n g a c t u a l waves was p u r c h a s e d a n d t r a n s p o r t e d t o many v e n u e s o f a c t u a l r a c e s t o i n c r e a s e o u r k n o w l e d g e on t h i s p a r t o f t h e p r o b l e m . F i g u r e 28.

A summary o f t h e wave o b s e r v a t i o n s i s g i v e n i n F i g u r e

Location Number of Observations Average Wind, knots

Wind less than 8 knots ^ o

Block Island 7

Caulina ^ 5*^

Waukegan 4

Chesapeake 0

Puget Sound 12 Group Average 4.2 knots

Wind 8 - 1 6 knots Long Beach 4 Catalina ^ j 2 . l San Francisco 6 LIS, Noroton 2 .^^ Puget Sound 7

Group Average 10.7 knots Wind greater than 16 knots

Puget Sound 2 ^.^ San Francisco 1 G r o u o Average 16.5 knots

B a s e d upon an a n a l y s i s o f t h e s e o b s e r v a t i o n s , a number of g e n e r a l l e s s o n s w e r e drawn:

* R a c i n g r a r e l y t a k e s p l a c e i n s i g n i f i c a n t l y l a r g e waves,

* The wave s i z e m e a s u r e d i s o n l y m i l d l y c o r r e l a t e d w i t h t h e o b s e r v e d w i n d s p e e d when c o n s i d e r e d i n t e r m s o f c l a s s i c a l deep open o c e a n wave s p e c t r a , and * T y p i c a l r a c e c o u r s e w a v e s do n o t e x h i b i t t h e s h a r p l y p e a k e d s p e c t r a o f f u l l y d e v e l o p e d s e a s p e c t r a . None o f t h e s e l e s s o n s i s s u r p r i s i n g i n h i n d s i g h t b e c a u s e we t e n d t o r a c e i n p r o t e c t e d w a t e r s and t o e n c o u n t e r d i u r n a l w i n d p a t t e r n s . However, t h i s p a r t of t h e r e s e a r c h p r o v e d t o be p a r t i c u l a r l y c r i t i c a l b e c a u s e o f the l a c k o f p u b l i s h e d d a t a on t h i s i m p o r t a n t a s p e c t o f added r e s i s t a n c e i n waves. I n o r d e r t o c o n s t r u c t a model f o r u s e i n t h e VPP, t h e wave r e c o r d s w e r e a v e r a g e d i n t h r e e b i n s : w i n d s l e s s t h a n 8 k n o t s ( VTW avg = 4.8) , w i n d s 8-16 k n o t s (VTW avg = 11) , and w i n d s g r e a t e r t h a n 16 k n o t s ( VTW avg= 1 7 ) , t o b r o a d l y r e p r e s e n t l i g h t , medium , and h e a v y w i n d s r e s p e c t i v e l y a s shown i n F i g u r e 30.

From t h e s e f a i r e d s p e c t r a , e n e r g y a t v a r i o u s f r e q u e n c i e s a s c a s e b a s e d upon t h e o b s e r v e d c o m m i t t e e . The f i t o f t h e model 31. a f i t was s e l e c t e d t o r e p r e s e n t a f u n c t i o n o f w i n d s p e e d , i n t h i s w i n d s p e e d a s t a k e n by a r a c e i s compared t o t h e d a t a i n F i g u r e

I "

AVERAGE SPECTRUM Av| ol Local ion Avencn <l ku

AVERAGE SPECTRUM AUI oi L o E i m A w i f n <..<I6 ku

AVERAGE SPECTRUM Av| LoMDM A v « n | a 16» kta

/

k

\

P r e s u m a b l y , a s more wave o b s e r v a t i o n s a r e made o v e r a b r o a d e r group o f v e n u e s , t h i s model may be r e f i n e d o r ^^P^^^^^' e a r c h e « p u r p o s e , t h e P r o j e c t wave buoy i s a v a i l a b l e t o o t h e r r e s e a r c h e r s who w i s h t o u n d e r t a k e s u c h a d d i t i o n a l m e a s u r e m e n t s .

EXPERffiNCE WITH IMPLEMENTATION

Of c o u r s e t h e f i n a l r e s e a r c h h a s n o t been i m p l e m e n t e d a t t h i s t i m e ; t h e comments w h i c h f o l l o w a r e i n t e n d e d t o i n f e r w h a t we might from r e l a t e d e x p e r i e n c e s .

The P h a s e I r e s u l t s were p r o d u c e d i n t h e form o f a h a n d i c a p p i n g c h a n g e t o r e f l e c t t h e e f f e c t s o f w e i g h t c o n c e n t r a t i o n o n l y . T h e s e r e s u l t s a s r e p r e s e n t e d b y t h e c o m p u t e r c o d e modules DELR a n d SPM w e r e i n s t a l l e d i n a n e x p e r i m e n t a l v e r s i o n o f t h e IMS VPP a t USSA i n summer 1991, and t h e r e s u l t s o f a t e s t f l e e t made a v a i l a b l e t o t h e IMS Committee a n d t h e I T C a t t h e f a l l 1991 m e e t i n g s i n Newport. When a t e s t f l e e t was r u n f o r a l a r g e v a r i a t i o n i n t h e v a l u e o f p i t c h moment o f i n e r t i a , t h e h a n d i c a p c h a n g e s seemed t o e x p e r i e n c e d ^ ^ o b s e r v e r s t o e m u l a t e t y p i c a l d i f f e r e n c e s o b s e r v e d w h i l e r a c i n g . B e c a u s e o f t h e a p p a r e n t p r o m i s e o f t h e P h a s e I r e s u l t s and a demand t o u s e t h e r e s e a r c h r e s u l t s e v e n w h i l e c o n t i n u i n g d e v e l o p m e n t o f t h e m e a s u r i n g m a c h i n e , t h e F l a g O f f i c e r s o f t h e C m i s i n g C l u b o f A m e r i c a r e q u e s t e d t h a t a s u r r o g a t e method be d e v i s e d f o r t h e 1992 Bermuda R a c e w h i c h would u s e t h e n e x i s t i n g r e s u l t s t o h a n d i c a p t h e R a c e , and t o make t h e o p p o r t u n i t y a v a i l a b l e f o r e x p e r i m e n t i n g w i t h h a n d i c a p p i n g f o r p i t c h i n g moment i n a c c o r d a n c e w i t h t h e p u r p o s e o f t h e R a c e r e l a t e d t o c o n t r i b u t i n g t o t h e e n c o u r a g i n g t h e d e v e l o p m e n t o f c r u i s i n g y a c h t s .

A s y s t e m w a s d e v i s e d and t r i e d w h i c h was b a s e d upon t h e f o l l o w i n g a p p r o a c h : * S i n c e measurement d a t a d i d n o t e x i s t on w e i g h t d i s t r i b u t i o n p e r s e , a means o f i n f e r r i n g t h e r e l a t i v e a t t e n t i o n p a i d t o added r e s i s t a n c e i n w a v e s u s i n g c e r t i f i c a t e d a t a was d e v e l o p e d , * T h i s m e a s u r e o f p r o b a b i l i t y t h a t a y a c h t h a d b e e n o p t i m i z e d f o r p e r f o r m a n c e i n w a v e s was assumed t o c o r r e l a t e w i t h a l o w p i t c h moment o f i n e r t i a .

Note that for such apparent agreement, it was necessary to reason that the boats which appeared to be stripped out had indeed achieved weight concentration thereby. This leap of faith was based upon calculations of what sort of weight concentration should be possible for a typical yacht, and was not based upon measured weight concentration properties of the test fleet.

* The assumed v a l u e of p i t c h moment of i n e r t i a was then ^ s e d i n

c o n j u n c t ' f o T w i t h t h e r e s u l t s of t h e Phase I r e s e a r c h t o c a l c u l a t e

e x p e r i m e n t a l c e r t i f i c a t e s f o r t h e f l e e t .

d e v e l o p e r s .

T n f a c t

t h e s u r r o g a t e method was s u f f i c i e n t l y a p p e a l i n g t o the

IMS o'Jiers C o S ^ i t t e ^ of USSA, t h a t i t was -^opteaj^y^SSAj^^^^^

P r o s c r i p t i o n e f f e c t i v e 1 June 1992, and we now have had t h e b e n e f i t

orSmost o? r s e a s o n of r a c i n g under t h i s implementation.

The g r e a t e s t weakness i n any implementation a t t h i s time i s

IMPUCATïONS OF RESULTS

T h e u s e o f a n o m i n a l g y r a d i u s , e v e n w i t h o u t a s u r r o g a t e method, w i l l a l r e a d y s t a r t t o h a n d i c a p t h e f l e e t i n t h e s e n s e t h a t t h e s h o r t - e n d e d y a c h t s h a v e l o w e r g y r a d i u s t o s a i l i n g l e n g t h r a t i o s t h e n more t r a d i t i o n a l y a c h t s h a v i n g l o n g o v e r h a n g s . Of g r e a t e r c o n c e r n , i s t h e p r o b l e m t h a t i m p l e m e n t a t i o n w i l l i n v o l v e a p p l y i n g c o r r e c t i o n s t o a n a l r e a d y c o n t a m i n a t e d s p e e d p r e d i c t i o n a s d e s c r i b e d i n an e a r l i e r s e c t i o n . U n t i l s u c h t i m e a s t h e c a l m w a t e r r e s i s t a n c e p r e d i c t i o n t o o l c a n be i m p r o v e d t o t h e e x t e n t t h a t i t a g r e e s w i t h measured r e s i s t a n c e s o f h u l l s , some r i s k e x i s t s t h a t i m p l e m e n t i n g t h e added r e s i s t a n c e r e s u l t s m i g h t n o t i m p r o v e h a n d i c a p s . T h i s r i s k i s c o n s i d e r e d t o be s m a l l , and s h o u l d be m i t i g a t e d by c a r e f u l s t u d y o f t h e r e s u l t s on a t e s t f l e e t b e f o r e i m p l e m e n t a t i o n .