Boat Hull

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by Alex Zidock Jr.
Boat Hull
D E S I G N
Boat Hull
D E S I G N
Hu ck F i n n ’ s raft was a b asi c f lat-
b o tto m b o at. S o was R o b ert F u lto n ’ s
Clermont, th e fi rst co m m erci ally su c-
cessfu l steam b o at. T h e d esi g n o f a
b o at h u ll d o es n o t d ep en d o n o verall
si ze, b u t o n th e i n ten d ed u se o f th e
b o at, o r th e resu lts th e b o ater wan ts to
attai n . M i su se o f a b o at wh o se h u ll
was d esi g n ed fo r an o th er ap p li cati o n
co u ld b e co stly.
Wh en m y so n was ab o u t ei g h t years
o ld , we to o k o u r wi d e-b o wed f lat-b o t-
to m car-to p p er to a Van S ci ver L ak e,
p art o f th e p ri vately ru n P en n Warn er
C lu b , i n T u llyto wn , P en n sylvan i a, fo r
an aftern o o n o f fi sh i n g . T h i s p o rti o n
o f th e lak e was a resu lt o f a san d an d
g ravel o p erati o n th at left th e en ti re
b o tto m an alm o st p erfect 2 0 feet d eep
wi th few m o u n d s an d very li ttle b o t-
to m stru ctu re. T h e sp ri n g d ay was
b ri g h t wi th n o n o ti ceab le wi n d .
L au n ch i n g th e b o at was u su ally an
easy o n e-m an o p erati o n , excep t o n
th ese week en d o u ti n g s wh en i t to o k
b o th o f u s, wo rk i n g to g eth er,” to g et
th e b o at read y to sai l. A b o u t an h o u r
after we were o n th e lak e, I n o ti ced a
sli g h t wi n d . A b o u t 1 5 m i n u tes later, I
co u ld feel th e co ffee-can cem en t an -
ch o r b eg i n to b o u n ce as th e wi n d an d
sm all waves li fted an d settled th e b o at.
N o th i n g to wo rry ab o u t, I th o u g h t,
an d p ro b ab ly i f m y so n weren ’ t o n
b o ard an d th ere was n o li g h tn i n g , I ’ d
ju st ri d e i t o u t.
M y ti m e to h ead fo r sh o re” an -
n o u n cem en t was m et b y a fro wn as h e
p u t h i s ro d i n th e b o at. Wi th so m e
an xi ety i n m y vo i ce I su g g ested h e
ti g h ten th e strap s o f h i s li fe jack et, an d
I p u lled th e 3 H P en g i n e to li fe.
A s I b eg an o u r 1 0 0 -yard jo u rn ey
q u arteri n g i n to th e wi n d , an d b ack to
sh o re wh ere th e stati o n wag o n was
p ark ed , m y co n cern fo r h i s safety g rew.
T h e b o at b eg an to p o rp o i se as th e i n -
creasi n g wi n d q u i ck ly rai sed waves,
an d th e b o w o f th e b o at b eg an to sco o p
water i n to th e b o at. N o w I co u ld see
m y so n ’ s g ri p ti g h ten i n g as h e watch ed
m y reacti o n . T h i s was th e fi rst ti m e I
exp eri en ced th i s p ro b lem wi th th e
li ttle f lat-b o tto m b o at, an d m ayb e i t
was ju st b ecau se o f h i s ad d ed wei g h t
n ear th e b o w, b u t I k n ew I co u ld n o t
p ro ceed o n co u rse o r we’ d swam p .
T h e wi n d wan ted to b lo w u s p arallel
to th e sh o re an d i n to a co ve th at h ad
so m e li ly p ad s. I q u i ck ly calcu lated
th at a lo n g walk aro u n d th e lo wer p art
o f th e lak e was m u ch b etter th an a
sh o rt swi m , so I slo wed th e m o to r
en o u g h to m ai n tai n a co n tro lled d ri ft,
an d th e water n o lo n g er cam e i n th e
b o at. We f lo ated i n to th e p ad s, wh i ch
were clo se to sh o re, an d wi th th e h elp
o f th e o ars we reach ed safety. I t co u ld
h ave b een wo rse, an d even th o u g h th e
f lat-b o tto m jo h n b o at was n o t th e
p ro b lem , i t m et i ts m atch . A h i g h -
si d ed V ” -h u ll d esi g n so o n fo u n d i ts
way to th e rack s o n th e wag o n .
Flat-bottom boats
T h e o n e th i n g yo u can say ab o u t
f lat-b o tto m b o ats i s th at wi th th ei r
larg e b o tto m area, th e b o at i s very
stab le i n calm weath er. C h aracteri sti -
cally, h o wever, th e f lat, b ro ad b o w area
creates a ro u g h ri d e. T h ese b o ats are
u su ally li m i ted to lo w h o rsep o wer m o -
to rs b ecau se th ey d o n ’ t h an d le well at
h i g h sp eed . F lat-b o tto m b o ats are
g reatly su i ted fo r fi sh i n g i n sk i n n y wa-
ter fro m th e S u sq u eh an n a R i ver to th e
F lo ri d a K eys, wh ere a very sh allo w
d raft i s a m u st.
E arly i n o u r n au ti cal h i sto ry, b o ats
were p o wered b y wi n d o r b y h an d -
stro k ed o ars. E arly b o at d esi g n ers
fo u n d th at b o ats wen t faster, an d were
Flat bottomwith hard chines
chine
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Flat bottomwith soft chines
chine
§
Vee bottom
Vee bottomwith pad and strakes
pad
strakes
§
§
Vee bottomwith strakes
strakes
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Pennsylvania Angler & Boater www.fish.state.pa.us
illustration-TedWalke
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easi er to steer, i f th e b o w was p o i n ted .
T h ey also so o n d i sco vered th at b y lo w-
eri n g th e cen ter o f g ravi ty, th e h i g h sai l
m asts h ad b etter b alan ce, an d u su ally
k ep t th e b o at u p ri g h t even i n b ad
weath er.
Displacment, planing hulls
T h ese early b o ats were co n stru cted
wi th d i sp lacem en t” h u lls. T h i s m ean s
th at th e h u ll wo u ld p u sh th ro u g h o r
cru i se th ro u g h th e water. T h e p ro p er
p ro p eller fo r a d i sp lacem en t h u ll i s o n e
wi th a lo wer p i tch wh en p o wered b y an
o u tb o ard o r stern d ri ve. Wi th th e ad -
ven t o f m ech an i cal p o wer cam e b o ats
wi th p lan i n g ” h u lls, wh i ch li ft th e
b o at p arti ally o u t o f th e water to sk i m
o n th e su rface. T o d ay, i t’ s so m eti m es
d i ffi cu lt to tell th e d i fferen ce b etween
th e two , b u t th ere are sli g h t d i fferen ces.
P ro p ellers o n b o ats wi th p lan i n g h u lls
o ften are n o t fu lly su b m erg ed , so th ey
n eed to p ro vi d e h o ld i n g ab i li ty as well
as h i g h er p i tch an d rak e, b ecau se o f
h i g h er to p -en d sp eed s.
Round-bottom hull,
“V” bottoms
T h e ro u n d -b o tto m b o at h as m o stly a
d i sp lacem en t h u ll an d i s u su ally u sed
fo r d i n g h i es, ten d ers, an d so m e car-to p
b o ats. T h i s b o at style i s u su ally easi er
to m an eu ver at slo w sp eed s th an th e
f lat-b o tto m b o at.
T h e V ” -b o tto m b o at i s p ro b ab ly th e
m o st co m m o n h u ll d esi g n . M o st
m an u factu rers o f b o ats b u i lt to d ay u se
m o d i fi cati o n s o f th i s d esi g n . T h i s d e-
si g n o ffers a g o o d ri d e i n ro u g h water
as th e p o i n ted b o w sli ces fo rward an d
th e V ” -sh ap ed b o tto m so ften s th e u p -
an d -d o wn m o vem en t o f th e b o at. T h e
d eg ree o f th e an g le o f th e V ” i s called
“ d ead ri se.” A s th e V ” sh ap e exten d s to
th e b ack o f th e b o at, i t u su ally f latten s
o u t u n ti l i t all b u t d i sap p ears at th e
tran so m . S o m e V ” -b o tto m b o ats h ave
a f lat su rface at th e very b o tto m called
a p ad .” T h i s p ad allo ws a li ttle m o re
p lan i n g su rface an d at th e sacri f i ce o f a
li ttle so ftn ess i n th e ri d e, b u t th i s ad d i -
ti o n i n creases to p sp eed .
Tri-hull, tunnel hull
T h ere are m an y b o ats i n P en n sylva-
n i a waters th at are a d i sti n ct
m o d i fi cati o n o f th e V ” -b o tto m th at
are called tri -h u lls an d cath ed ral h u lls.
T h e tri -h u ll b o at i s th e trad i ti o n al V ”
h u ll wi th ad d i ti o n al o u tsi d e h u lls.
T h i s d esi g n i s m o re stab le th an th e
“ V ” -b o tto m at rest, b u t i t g i ves a
ro u g h er ri d e i n ch o p p y water b ecau se
o f th e i n creased su rface at th e b o w.
T u n n el b o ats h ave b een d esi g n ed to
trap a cu sh i o n o f ai r b en eath th e h u ll
to red u ce d rag o n th e o u tsi d e h u lls.
T h i s d esi g n i s d i fferen t fro m a catam a-
ran b o tto m b ecau se th e i n n er ed g es o f
th e o u tsi d e h u lls h ave sh arp co rn ers to
i m p ro ve th e h an d li n g o f th ese b o ats at
very h i g h sp eed s. M an y race b o ats are
co n stru cted wi th tu n n el h u lls an d are
so m eti m es called “ h yd ro p lan es.”
Pontoon boat
Very p o p u lar i n th e K eysto n e S tate
are p o n to o n b o ats. A n d ju st as th e
n am e i m p li es, th e p o n to o n , o r d eck
b o at, i s a f lat, rai sed d eck su p p o rted
wi th two o u ter h u lls p o n to o n s) th at
are u su ally co n stru cted o f alu m i n u m .
T h ese b o ats co m b i n e a lo t o f featu res
o f o th er b o ats. T h ey ri d e very d ry b e-
cau se th e d eck i s rai sed ab o ve th e
f lo ats. T h ey are stab le, an d wi th th e
tran so m m o u n ted to th e u n d ersi d e o f
th e d eck , th ey are easy to m an eu ver
wi th an o u tb o ard m o to r.
T h e b o ater wh o i s lo o k i n g fo r all-
aro u n d u se can m ak e alm o st an y h u ll
d esi g n wo rk fo r m an y water co n d i -
ti o n s. B u t even i n th e b ro ad est
m ark ets, h u ll d esi g n i s a co n ti n u al re-
search an d d evelo p m en t p ro ject. I n
sp eci fi c n i ch e m ark ets, li k e water sk i -
i n g , an d n o w i n th e fastest g ro wi n g o f
th e water sp o rts m ark ets,
wak eb o ard i n g , th e co m p eti ti o n fo r
b etter h u lls i s to u g h .
Wh en yo u are sh o p p i n g fo r a n ew
b o at, fi rst co n si d er th e water i n wh i ch
yo u ’ ll u se th e b o at. T h en tak e i n to
co n si d erati o n h o w m an y p eo p le wi ll
g en erally u se th e b o at, an d th en d eter-
m i n e h o w th e b o at wi ll b e u sed . B o ats
co m e i n a wi d e ran g e o f co lo rs an d
co ck p i t co n f i g u rati o n s th at yo u can
li ve wi th i f yo u li k e all o f th e o th er at-
tri b u tes th e b o at h as to o ffer. B u t th e
o n e th i n g th at sh o u ld b e at th e to p o f
yo u r sh o p p i n g li st i s wh at’ s o n th e b o t-
to m o f th e b o at yo u wan t to b u y.
Catamaran
Pontoon
Tri-hull or cathedral hull
Tunnel bottom
Tunnel vee
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