Is the w i n g Iceel, i n its various f o r m s , o f
genuine benefit to the cruising yachtsman
or j u s t a passing m a r k e t i n g tool?
G E O F F P A C K investigates this latest
t r e n d o f t h e m o d e r n cruising yacht
A
G L A N C E a r o u n d any shore-basedb o a t s h o w w i l l c o n f i r m that the latest s a i l i n g f a s h i o n is the w i n g keel. T h e y ' v e s p r o u t e d i n d i f f e r e n t shapes, sizes and c o n f i g u r a t i o n s o n dozens o f m o d e r n boats T h e late B e n L e x c e n c o u l d n e v e r have k n o w n w h a t he was s t a r t i n g w h e n he p a t e n t e d , the w i n g keel f i t t e d to the A m e r i c a ' s C u p w i n n i n g Australia IL H e w o u l d also h a v e been the first to a d m i t that t h e y are n o t h i n g n e w and have been e x p e r i m e n t e d w i t h aboard yachts f o r decades. H o w e v e r , i t was Australia Ws a m a z i n g p e r f o r m a n c e that s p a w n e d so m a n y l o o k - a l i k e s i n the c r u i s i n g field.
A n o t h e r f a c t o r has been the general d e m i s e o f t h e I O R r u l e and its i n f l u e n c e o n
T h e M k V W a r w i c k Collins T a n d e m keel, here fitted to an 80ft sloop whose draught was cut f r o m a n o r m a l 12ft to 8ft 6in
Figure 1
y a c h t d e s i g n . T h e l O R n e v e r a l l o w e d w i n g keels; indeed the centre o f g r a v i t y aspects o f that r u l e e n c o u r a g e d h i g h aspect r a t i o t a p e r i n g keels w h o s e w e i g h t was h i g h up rather than l o w d o w n . Sure e n o u g h c r u i s i n g boats, a l t h o u g h n o t g o i n g to this rather b a c k v / a r d e x t r e m e , nevertheless f o l l o w e d suit w i t h fin keels w h i c h i n the sixties had been n a r r o w r o o t e d b u t t h i c k e n -i n g as t h e y progressed d o w n (to ach-ieve best centre o f g r a v i t y ) t o even-sectioned p a r a l l e l o g r a m — better than I O R but h a r d l y ideal.
I f one l o o k s at the keels o f boats l i k e the Pioneer 10 they had w h a t t o d a y m i g h t be t e r m e d as a d e r i v a t i v e o f t h e Scheel keel ( F i g 1). M a n y o f the V a n de Stadt and D u f o u r boats (in p a r t i c u l a r the S y l p h e and A r p e g e , designed i n 1967) had the b u l b e d keels ( F i g 2) that w e ' r e s t a r t i n g to see m o r e o f these days, w h i c h rather d e m o n -strates t h a t design has c o m e f i l l circle in the m e a n t i m e .
Why a wing?
T h e r e are t w o m a j o r p r i n c i p l e s b e h i n d the latest c r o p o f keels. T h e first is i r r e f i i t a b l y
e f f e c t i v e and s t r a i g h t f o r w a r d — b y c o n c e n -t r a -t i n g w e i g h -t as l o w as possible i n -the keel's shape, a designer can achieve the same, and s o m e t i m e s an even b e t t e r , centre o f g r a v i t y as he w o u l d w i t h the c o m m o n c o n v e n t i o n a l c o n s t a n t s e c t i o n p a r a l l e l o -g r a m keel, b u t w i t h less d r a u -g h t . T h i s he achieves b y a n u m b e r o f routes — the a d d i t i o n o f w i n g s , general t h i c k e n -i n g at base a n d t h -i n n -i n g o u t at r o o t ( w h i c h Scheel b r o a d l y bases his idea a r o u n d ) o r b y u s i n g a b u l b .
B y d o i n g this he can reduce the d r a u g h t o f the y a c h t c o n s i d e r a b l y , w h i c h is a desirable characteristic o u t o f sheer p r a c t i -c a l i t y (and is a f e a t u r e w h i -c h m a y w e l l sell m o r e boats).
Figure 2
So f a r so g o o d , b u t he is t h e n u p against the n o t i n c o n s i d e r a b l e p r o b l e m that the s h a l l o w e r a keel becomes the less e f f i c i e n t i t is. A s the boat leans against her keel and m o v e s f o r w a r d , a g o o d deal o f the w a t e r o n the l e e w a r d ( h i g h pressure) side escapes u n d e r d i e keel. T h i s is r e f e r r e d to as v o r t i c a l t i p loss. T h e s h a l l o w e r the k e e l , the greater p r o p o r t i o n o f its area is a f f e c t e d b y i n e f f i c i e n t t i p losses, d e m o n s t r a t e d i n F i g 3.
H e r e e n t e r s t h c s e c o n d m a j o r c h a r a c t e r i s -tic o f these n e w keels — the s l i g h t l y m o r e
c o n t e n t i o u s p o i n t o f t h e v a r i e t y o f m e t h o d s designers 'have c o m e u p w i t h t o reduce these t i p losses and t h e r e b y m a i n t a i n t h e i r s h a l l o w d r a u g h t / i d e n t i c a l C o f G .
Scheel keels (Fig i)
F i g 1 s h o w s o n e o f t h e f o r e r u n n e r s i n this t h i n k i n g , the Scheel keel d e s i g n e d b y A m e r i c a n naval architect H e n r y Scheel,' w h o first came up w i t h the idea as far back as 1947. I t w a s n ' t u n t i l the 1970s, h o w e v e r , that he started using i t , to great e f f e c t . Since that t i m e , l i t e r a l l y h u n d r e d s o f y a c h t have been fitted w i t h the Scheel keel i n c l u d i n g such classes as the R i v a l / B o w -m a n s , -m a n y Swans and O y s t e r s — w h o s e c a l i b r e alone g i v e credence to its c l a i m s . T y p i c a l l y , a 3 7 - f o o t e r r e q u i r i n g 7 f t d r a u g h t w i t h a c o n v e n t i o n a l keel can get a w a y w i t h 5 f t w i t h the Schee] keel, a s i g n i f i c a n t s a v i n g that can e x t e n d t h e yacht's c r u i s i n g l i m i t s c o n s i d e r a b l y .
Conventional wings
(Fig4)
F i g 4 is t y p i c a l o f t h e m o s t c o m m o n w i n g s b e i n g fitted to several p r o d u c t i o n c r a f t a n d , i n t h e i r v a r i o u s f o r m s , these are close relations to Lexcen's Australia IL E v e r y
Figure 4
designer has his o w n theories and t h e r e f o r e each o f these keels varies i n detail and shape — o b v i o u s l y space doesn't a l l o w us to e x p l o r e e v e r y v a r i a t i o n . Fig 5 s h o w s a s i m i l a r t y p e o f w i n g b u t used o n a m u c h h i g h e r aspect r a t i o keel w h e r e d r a u g h t is n o t a c o n s i d e r a t i o n , and w h i c h makes i t p a r t i c u l a r l y suitable (and e f f i c i e n t ) f o r a d a g g e r b o a r d .
B r o a d l y s p e a k i n g , these w i n g s satisfy the t w o p r i n c i p a l aims t o m a i n t a i n the same centre o f g r a v i t y (or keep i t as l o w as possible) and to reduce t i p losses to a m i n i m u m b y c r e a t i n g an endplate. T h e w i n g s are o f t e n f i t t e d t o v.'ards the back edge o f t h e k e e l , because this is w h e r e the u p losses o c c u r as the y a c h t m o v e s f o r w a r d . T h e a l t e r n a t i v e is u s i n g a c u t - o f f delta shape
w h i c h serves the same p u r p o s e .
H o w e v e r , h y d r o - d y n a m i c s is a v e r y c o m p l e x subject and there is c o n s i d e r a b l y m o r e t o p r o d u c t i n g a s h a l l o w d r a u g h t b o a t t h a n b y s i m p l y a d d i n g w i n g s t o a s t u m p i e r keel. I n s i m p l e t e r m s , the m a j o r p r o b l e m is d r a g a n d the successful w i n g keel is o n e w h o s e d r a g (and t h e r e f o r e size) is m i n i -m i s e d w i t h o u t c o -m p r o -m i s i n g the boat's w e a t h e r h n e s s .
D u e t o the u n a v o i d a b l e d r a g , the w i n g keel w i l l never o u t p e r f o r m the c o n v e n t i o n -al keel i n l i g h t e r g o i n g , say less than 12-14 k n o t s w i n d s p e e d . O t h e r than the i r r i t a t i o n o f p o o r e r boatspeed caused b y the w i n g s b e i n g t o o l a r g e , there is the s i g n i f i c a n t danger t h a t t o o m u c h d r a g w i l l induce i n a y a c h t a t e n d e n c y to b r o a c h d o w n w i n d a n d g r i p e w h e n g o i n g to w i n d w a r d . T h i s u n d e s i r a b l e feature is one t o bear i n m i n d i f the w i n g keel has been designed hastily a n d added as a m a r k e t i n g g i m m i c k .
W h e n d e s c r i b i n g w i n g s , one o u g h t to
bear i n m i n d that, i n s o m e boats, w i n g s are added n o t necessarily to reduce d r a u g h t b u t s i m p l y to i i n p m v e e f f i c a - i i L y hy g e t t i n g the v / e i g h t l o w e r and r e d u c i n g t i p losses b y creating an endplate. A s l o n g as the w i n g s are n o t so large as to create t o o m u c h d r a g , one s h o u l d n ' t need to w o r r y a b o u t the yacht s a g g i n g o f f to l e e w a r d because the lateral area o f the .keel is m o r e o r less u n c h a n g e d .
Figure 5
As a contrast, the end plates fitted on the H u n t e r H o r i z o n 26 are just that — they reduce tip losses and i m p r o v e efficiency but the lateral area and draught o f t h e keel is the same as a conventional fin
The bulb keel
(Fig 2)
T h i s was v e r y c o m m o n , especially d u r i n g the early years o f t h e f m k e e l . Its p r i n c i p a l a i m was to keep the centre o f g r a v i t y as l o w as possible and, t h r o u g h its t o r p e d o shape, to m i n i m i s e d r a g as f a r as possible. I n f a c t , as a b y - p r o d u c t i t serves to help reduce t i p losses a l t h o u g h n o w h e r e near as e f f i c i e n t l y as w i n g s . I n general, as l o n g as a keel's lateral area hasn't been m i n i m i s e d t o o m u c h o n the basis o f t h e b u l b ' s existence, the b u l b keel is all g o o d n e w s f o r the c r u i s i n g m a n .
The Tandem Keel
(Fig 6)
D e s i g n e d b y W a r w i c k C o l l i n s , the T a n -d e m keel is m o s t unusual i n e m p l o y i n g t w o f o i l s and a delta endplate t o create a keel w h i c h is g e n u i n e l y as e f f e c t i v e u p w i n d as a deep keel b u t w h i c h cuts d o w n the y a c h t ' s keel d r a u g h t ( n o t o v e r a l l d r a u g h t ) b y as m u c h as 4Ü per cent. It is fair t o say that t h e r e has been m o r e research, b o t h t h e o r e t i c a l and practical, c o m p l e t e d o n this keel t h a n any other t y p e o f keel c o m m e r c i a l l y available f o r yachts. T h e T a n d e m k e e l also has a n u m b e r o f o t h e r characteristics, s o m e o f w h i c h w i n g e d keels also have.
B y c o n c e n t r a t i n g a p p r o x i m a t e l y 55-60 per cent o f its w e i g h t i n the endplate, s t a b i l i t y is v e r y g o o d . T h e endplate also dampens the m o t i o n o f t h e y a c h t c o n s i d e r -ably w h i c h , apart f r o m the o b v i o u s c o i n f o r t element (at sea, T a n d e m — and w i n g - k e e l e d yachts all feel m u c h b i g g e r than t h e i r L O A w o u l d suggest), also means that the r i g , instead o f g y r a t i n g a r o u n d o v e r the h u l l , w o r k s m o r e e f f i c i e n t l y , c r e a t i n g m o r e d r i v e and t h e r e f o r e better speed.
I n next m o n t h ' s issue w e test t w o identical boats, one f i t t e d w i t h a T a n d e m , the o t h e r w i t h a f m keel. D u r i n g those trials the d i f f e r e n c e i n w i n d w a r d p e r f o r m a n c e i n a s l o p p y sea was m a r k e d — the T a n d e m streaked ahead.
A n o t h e r feature o f the T a n d e m keels, and indeed m a n y o f t h e w i n g keels, is that
The Parker 31 sits very steadily on her wing-keeled daggerboard
their l o w e r aspect r a t i o (ie b e i n g greater i n l e n g t h b u t s h o r t e r i n d e p t h ) means t h a t the y a c h t has m u c h better d i r e c t i o n a l s t a b i l i t y and behaves m o r e l i k e a t r a d i t i o n a l l o n g -k e e l e d boat t h a n a f i n and s-keg y a c h t .
W i t h o u t g o i n g i n t o the f i n e r p o i n t s , the T a n d e m keel w o r k s o n a b r o a d l y s i m p l e concept. T i p losses n o t o n l y create a great deal o f drag; t h e y also reduce the e f f e c t i v e -ness o f t h e keel's lateral area. B y r e d u c i n g
Figure 6
t h e m s i g n i f i c a n t l y , the keel's area can be m i n i m i s e d b y w o r k i n g e f f i c i e n t l y . C o l l i n s set a b o u t r e d u c i n g t i p losses i n t w o w a y s — one b y the delta endplate and the o t h e r b y i n t r o d u c i n g a gap b e t w e e n w h a t w o u l d •become t w o f o i l s o f t h e k e e l . A s can be seen
f r o m F i g u r e 7, the accelerated flow t h r o u g h this slot (aided b y the delta endplate) counteracts the n o r m a l v o r t i c a l t i p losses w h i c h in t u r n cuts d o w n d r a g s i g n i f i c a n d y ioi^'pressure (Windward)side High pressure (Leeward) side Sfrong counter-vortical flow through slot , Normal vortical y tip flow
Schema tic wie ity from forward of
counler-vortical flow Muced txjslol
Figure 7O C T O B E R 1988
a n d makes the f o i l / k e e i w o r k v e r y e f f i c i e n t -l y . N o t o n -l y that, b u t b y s h a p i n g the s-lot i n a b r o a d l y V - s e c t i o n w i t h the w i d e r gap at the t o p , the w a t e r tends t o be f o r c e d u p w a r d s as i t is accelerated t h r o u g h w h i c h also helps to c o u n t e r a c t the n o r m a l v o r t i c a l fiow o n the k e e l .
A g a i n , w i t h o u t d e l v i n g t o o d e e p l y i n t o
the reasons, the a f t e r f o i l o f the T a n d e m keel w o r k s i n v e r y clean w a t e r flow m e a n i n g t h a t its resistance t o s t a l l i n g is v e r y h i g h . T h i s has t w o e f f e c t s : o n e , i n a possible b r o a c h s i t u a t i o n w h e n a c o n v e n t i o n a l keel is a b o u t t o s t a l l , the T a n d e m w i l l n o t , and t w o , l a m i n a r flow attaches'early o u t o f a tack ( F i g 8) so the y a c h t accelerates a w a y faster w i t h o u t the need to bear a w a y i n i t i a l l y ' t o get g o i n g ' .
W i t h regard to b r o a c h i n g , the T a n d e m keel's e n d p l a t e (and i n d e e d , w i n g keels i n general) also reduce d o w n w i n d r o l l i n g
76 s i g n i f i c a n t l y w h i c h , c o m f o r t and ease o f w o r k i n g apart, can i n d u c e a b r o a c h .
Practical considerations
T h e b i g g e s t ' i f a b o u t w i n g keels is d r y i n g o u t w i t h t h e m . T h i s aspect falls i n t o t w o b r o a d categories; the p l a n n e d g r o u n d i n g a n d the accidental. A p l a n n e d g r o u n d i n g d o e s n ' t need m u c h m o r e o r g a n i s a t i o n t h a n w h e n d r y i n g o u t a c o n v e n t i o n a l fin-kecler. M o s t w i n g - k e e l e d yachts w i l l sit u p r i g h t o n h a r d , level g r o u n d (ie concrete) b u t i t is q u i t e a risk at the best o f t i m e s ; one r a r e l y sees the b u i l d e r s o f these boats d i s p l a y i n g t h e m as such at boat s h o w s .B e a c h i n g legs w i l l n o r m a l l y be r e q u i r e d , o r a l t e r n a t i v e l y the b o a t can lie alongside, a n d be lashed t o , a w a l l o r piles w h i l s t a g r o u n d (especially as v e r y o f t e n the g r o u n d near such w a l l s w i l l slope and m a k e the b o a t lean o u t w a r d s ) . W h i l s t s o m e boats' w i n g keels are arranged so that they lie p l u m b u p r i g h t , others, i n c l u d i n g the T a n d e m keel, have a s l i g h t v-shape o n the b o t t o m w h i c h a l l o w s the boat to be heeled s l i g h t l y and leaned against a q u a y s i d e . T h i s is b y f a r the m o s t desirable a r r a n g e m e n t .
T h e accidental g r o u n d i n g is a b i g g e r p r o b l e m . W e are all g u i l t y o f g o i n g a g r o u n d f r o m t i m e to t i m e despite accurate echo s o u n d e r s and the alarms o n t h e m . I f o n e d o e s n ' t m a n a g e to get o f f and the tide is f a l l i n g , i n a c o n v e n t i o n a l fin keeler one w i l l n o r m a l l y heel the boat b y means o f p i l i n g the anchor a n d c h a i n and c r e w o n one side so that she leans the w a y y o u w a n t her t o . I n this w a y , i f a g r o u n d o n a n y t h i n g o f an i n c l i n e (as w i l l be the case o n the edge o f a c h a n n e l , f o r e x a m p l e ) the y a c h t can lie i n w a r d s and reduce the final angle o f heel.
T h i s c a n n o t be d o n e w i t h a w i n g - k e e l e d y a c h t unless one is able t o heel her o v e r q u i t e c o n s i d e r a b l y (see F i g 9, each is d i f f e r e n t , d e p e n d e n t o n the w i d t h o f t h e w i n g a n d h e i g h t o f C o f G ) . N o t o n l y that, b u t t h e sequence i n F i g 10 d e m o n s t r a t e s that the w i n g k e e l e d y a c h t w i l l a l w a y s f a l l o u t -w a r d s a n d t h e r e f o r e n o t o n l y m a k e l i f e v e r y u n c o m f o r t a b l e , b u t be i n a v e r y d a n g e r o u s p o s i t i o n w h e n the t i d e r e t u r n s . T h e o n l y possible s a l v a t i o n is b y r i g g i n g b e a c h i n g legs v e r y q u i c k l y b u t , i f there is any i n c l i n e , the s t r a i n o n the o u t w a r d o n e w o u l d be e n o r m o u s ( a s s u m i n g i t d i d n ' t s i n k i n t o t h e g r o u n d ) .
I t has t o be said t h e n that accidental g r o u n d i n g s w i t h a w i n g keel c o u l d be disastrous i n m a n y c i r c u m s t a n c e s . H o w e v -er, an a c c i d e n t a l g r o u n d i n g i n s o f t m u d can be salved i f a m a s t h e a d l i n e is t a k e n o u t t o a s t r o n g p o i n t (or m a y b e a n c h o r ) a n d the y a c h t heeled i n w a r d s , w h e n the w i n g s w i l l s i n k i n t o the m u d a n d the y a c h t d r y o u t as n o r m a l .
C r i t i c s o f t h e w i n g keel c l a i m that there is a p o s s i b i l i t y o f the w i n g s b e c o m i n g s t u c k i n
Quite large wings fitted on an otherwise high aspect ratio keel w h i c h w o u l d be impossible to dry out in n o r m a l circumstances
g l u u n o u s m u d p r e v e n t i n g the y a c h t f r o m rising. W h i l s t several cases have been r e p o r t e d o f yachts f a i l i n g t o f l o a t i m -m e d i a t e l y d u e to this s u c t i o n , as f a r as w e ' r e a w a r e n o n e has s i m k because o f i t . I t m i g h t be w o r t h b e a r i n g i n m i n d that i f the yacht's b e r t h is a m u d d y , t i d a l one, due a l l o w a n c e s h o u l d be m a d e f o r this t e m p o r a r y e x t r a d r a u g h t r e q u i r e m e n t .
A n o t h e r p r a c t i c a l p r o b l e m associated w i t h w i n g keels is p h y s i c a l l y p a i n t i n g t h e
Figure 9. W h e n going aground, in order for the yacht to lean the way tlie crew desires, she must be heeled to angle x before the Centre o f G r a v i t y falls beyond the w i n g tips
l o w e r faces o f t h e w i n g s because, unless the y a c h t is i n T r a v e l i f t s l i n g s , the underside is d i f f i c u l t t o get at. It is a l l the m o r e i m p o r t a n t as the u n p a i n t e d area can be large and, i n t h e same w a y that aeroplanes have p r o b l e m s t a k i n g o f f w i t h ice o n t h e i r w i n g s , a y a c h t w i t h m u c h m u d , barnacles and w e e d u n d e r her w i n g w i l l be v e r y i n e f f i c i e n t . T h e w i n g keels w i t h s l i g h t l y vshaped b o t t o m p r o -files are easier t o reach a l t h o u g h there are b o u n d t o be u n p a i n t e d sections, as there are, f o r t h a t m a t t e r , o n n e a r l y all fin-keeled boats t o o .
T h i s w i n g keel errs towards some questionable thinking — the lateral area of the keel (compared to an ordinary fin) has been cut d o w n considerably with very large wings fitted to make up for it
O C T O B E R 1988
Conclussorjs
So are thelatest c r o p o f k e e l s a genuine b o o n to the c r u i s i n g y a c h t s m a n o r n o t ? T h e r e are, o f course, g o o d and bad and w e feel sure that certain b u i l d e r s have, perhaps rather hastily, latched o n t o the idea p u r e l y f o r m a r k e t i n g pu rposes rather than necessarily o n m e r i t .
S h a l l o w d r a u g h t is u n d o u b t e d l y a s i g n i -ficant advantage f o r the c r u i s i n g m a n a l t h o u g h this f a c t o r m u s t be balanced against the uncertainties i n v o l v e d i n d r y i n g out, especially accidentally.
T h e t w o c o n f i g u r a t i o n s that c o m e o u t head and shoulders above t h e rest are W a r w i c k C o l l i n s ' s T a n d e m keel and the Scheelkeel. A l t h o u g h , ideally, the T a n d e m is best m a r r i e d t o one o f C o l l i n s ' s h u l l s , i t w i l l fit t o m o s t m o d e r n hulls w i t h an external keel. I t is n o t cheap. For an average 3 5 - f o o t e r i t w i l l cost s o m e t h i n g i n t h e r e g i o n o f £ 3 , 5 0 0 r e t r o - f i t t e d (quite a l o t cheaper i f fitted at the oiitset).. H o w e v e r , i f one is especially keen o n s h a l l o w d r a u g h t but also o n r e t a i n i n g the p e r f o r m a n c e o f deep keel, i t is w o r t h it i n l i g h t o f t h e o v e r a l l cost o f t h e boat.
A l t h o u g h less sophisticated and c o n -servative, the Scheel keel has p r o v e d t o be v e r y p o p u l a r w i t h hundreds o f yachts fitting t h e m all o v e r the w o r l d .
In next m o n t h ' s issue w e test f u l l y w i n g keels and T a n d e m keels against c o n v e n -t i o n a l fin keels fi-t-ted -t o iden-tical yach-ts. W i t h o u t p r e - e m p t i n g details o f that r e p o r t , none o f t h e v a r i a t i o n s o f w i n g k e e l ( i n c l u d i n g the T a n d e m ) p e r f o r m s as w e l l as c o n v e n t i o n a l fin keels i n l i g h t airs u p t o 12-13 k n o t s . A g a i n , i t is the price y o u p a y f o r the s h a l l o w d r a u g h t .
The wings o f t h e D u t c h Contest 35 which are both large and fitted canted
downwards, some w a y up f r o m the root of the keel. Note h o w they are set back some distance along the keel
L i k e e v e r y t h i n g , the present c r o p o f n e w g e n e r a t i o n keels o f f e r s the y a c h t s m a n another c o m p r o m i s e . W i n g keeled yachts all have a m u c h steadier m o t i o n than c o n v e n t i o n a l fin keelers o f their size and, p e r f o r m a n c e apart, this w i l l m a k e l i f e o n passage a l i t t l e easier. I f s h a l l o w d r a u g h t is h i g h o n y o u r p r i o r i t y list then these keels o f f e r s i g n i f i c a n t advantages and are d e f i n i t e l y w o r t h serious c o n s i d -e r a t i o n . T h -e practicaliti-es o f d r y i n g o u t are n o easier t h a n f o r a fin-keeler and accidental g r o u n d i n g s o n f a l l i n g tides are
even m o r e i n a d v i s a b l e . O
Next month: We report our findings after going afioat w i t h two different types o f keels. A pair of Sadler 34s with T a n d e m and fin keels were compared, also two Beneteau Oceanis 350s, one w i t h fin keel, the other w i t h a w i n g
