Speed Boat Developments

8/19/2019 Speed Boat Developments

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Speed Boat Developments From The Past Into The FutureMorley S. Smith

Abstract

Speed boat development began in the early 1900s !ith the development o" the "irst gasoline

po!ered piston engines. These engines !ere large and heavy. Boat hulls !ere long narro! round bottomed displa#ement hulls.

$s engine design improved% the &ee bottomed% hard #hined planing hull and the stepped hull !eredeveloped. Drive systems in#luded the dire#t drive% &ee drive% stern drive% and sur"a#e drive.

The per"orman#e o" ea#h #ombination o" hull type and drive system #an be illustrated by a grapho" Per"orman#e Fa#tors. 'Po!er Fa#tor vs. Speed Fa#tor( These Per"orman#e Fa#tors ta)e intoa##ount the running !eight% engine horsepo!er% and measured ma*imum speed.

For ea#h #ombination o" hull type and drive system% there is a ma*imum per"orman#e line or

+imit +ine. By #omparing the +imit +ines o" di""erent #ombinations o" hull type and drive system%!e #an also see ho! the e""i#ien#y o" boats has in#reased over the years.

The "inal,step is to loo) at #ombinations and #on"igurations !hi#h might produ#e even greaterimprovements in the "uture. The #ombination o" sur"a#e drive and stepped hull !ill be

signi"i#antly more e""i#ient than #urrent pleasure #ra"t.

Morley S. SmithPer"orman#e Plans% Freeville% -.. Member

* * *

The history re#orded herein% begins at about 1900 !hen internal #ombustion piston engines began

to repla#e heavy steam engines and boilers. Many o" the e*amples given herein are ra#e boats.These,boats !ere the most e""i#ient types o" their day. The speeds !eights and horsepo!er areo"ten re#orded.

Displacement Hulls

$t the turn o" the #entury !hen internal #ombustion engines !ere physi#ally large and very heavy%

the hulls used !ere displa#ement hulls. /hen a displa#ement hull moves "or!ard% the sharpnarro! bo! pushes or displa#es the !ater out to the sides. $s the hull passes% the !ater #loses in

behind it.

Figure 1 sho!s the lines o"Standard % one o" the

"astest displa#ement hullsat that time. 1

+ength 20 "t. Beam 3,2

110 hp. Speed 40 mph. in1904

These displa#ement hulls!ere round bottomedhulls. &ie!ed in #ross

se#tion% the tops o" the


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Figure 1. Standard , 1903

Figure 2. Displacement Hulls

Showing the effect of of waterlinelengthEngine weight = 30 lbs/HP

Photo of Dixie temporaril! nota"ailable#

Figure 3. Dixie, $isplacement hull

sides !ere more or less

verti#al. $s the sides movedo!n!ard% they #urvegently into a nearly "lat

bottom at the )eel.

Direct Drive:

The dire#t drive engine islo#ated at about mid lengthin the hull. The propeller

sha"t goes a"t "rom theengine transmission%

through the bottom o" the boat% to the propeller!hi#h is lo#ated a"t under

the transom.

5e"er to Figure 14% "or a s)et#h o" $lternate Propulsion Systems.

The per"orman#e o" a displa#ement hull is su#h that the po!er re6uirements in#rease as the speedin#reases. $t higher speeds% the po!er re6uirements in#rease more rapidly% until a speed isrea#hed !here great in#reases in po!er produ#e negligible in#rease in speed.

Figure. 7. illustrates the "irst basi# #hara#teristi# o"displa#ement hulls8 The greater the length% the higher thelimiting speed. I" you !ant to go "aster% you build a longer

hull.

+u#)ily the ra#ing rule ma)ers sa! !hat !as about to happen.

5a#e boats !ere already getting absurdly long. -e! ra#ingrules in 190: limited the length o" ;old 0 "t..

Dixie I +ength >0 * Beam :,2 1 1:0 =p. Dry !eight ?:%1:0 +b.

79.@ Mph in 190>A 47 Mph. in 1902Designer8


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Figure 4. Displacement HullsShowing the effect of weight

%went! foot waterline length

Figure 6 %he lines of a t!pical planing hull&

than 0.9 pounds per #ubi# in#h. 1


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Figure 7. %rim an$ Dragcharacteristics of a t!pical $irect$ri"e monohull&

Figure 8. Performance actors for Direct

Dri"e Planing Hulls

-early all o" the "iberglass planing pleasure boats made today have a vee

bottomed% hard #hine #on"iguration.

The #on#ept o" the hard #hined hull !as not ne!. E. /. ;rae" published

plans "or a hard #hined% vee bottomed displa#ement hull named Dolphin.

'b( It !as also dis#overed at about this time that a "lat deadrise or "lat

bottomed hull !ill have less drag than a highly veed hull. 4

Figure 3 sho!s the Trim and Drag #hara#teristi#s o" a typi#aldire#t drive monohull. '5unning !eight ? 7%:00 lb.(

$s the speed o" a planing hull in#reases% the trim angle% orangle o" atta#) de#reases.

'a( This in#reases the !etted area and greatlyIn#reases the drag.

'b( The propeller sha"t% sha"t strut and rudder also#ause drag. $ppendage drag. The appendage dragin#reases as the s6uare o" the speed. Total drag

in#reases very rapidly as speed in#reases.

/hen designing very high speed #ra"t% it is important to#onsider all o" the li"t and drag "or#es a#ting on the

appendages.

'Propeller% propeller sha"t% sha"t strut and rudder.( These "or#es#an greatly a""e#t the position o" the #enter o" li"t o" the hull

and the optimum hull proportions. Pro#edures and re"eren#es"or #al#ulating hull drag and appendage "or#es are given in the appendi*.

Planing Hull Limits

Figure '@( Per"orman#e Fa#tors "or Dire#t DrivePlaning =ulls

Per"orman#e Fa#tors are #omple* mathemati#ale*pressions !hi#h #ombine running !eight% engine

po!er and measured ma*imum speed. These

mathemati#al e*pressions are derived "rom models#aling pro#edures. By using these #omple*

e*pressions% all sie e""e#ts are eliminated. '$ moredetailed e*planation o" Per"orman#e Fa#tors is given in

the appendi*.(

The Per"orman#e Fa#tors sho! that as the amount o"applied po!er is in#reased% the speed in#reases. $t high

speeds% #onsiderable in#reases in po!er produ#erelatively small in#reases in speed.

By using these #omple* numbers !e #an #ompare the per"orman#e o" any sie or !eight o" dire#t drive

planing hull !ith the ma*imum per"orman#e possible. >


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There is a de"inite limit to ho! mu#h speed tan be obtained "rom a dire#t drive% ee bottomed

hull. This is #alled the +imit +ine% and this limit depends upon horsepo!er and !eight. The #loserthe a#tual per"orman#e #omes to the +imit +ine% the more e""i#ient the #ra"t.

The graph sho!s #ir#les !hi#h represent test data "rom a#tual boats. : 2 There are numerous

possible reasons !hy these data points do not lie on the limit line.

'a( The #hine beam o" the test boat is not optimum "or the po!er and

!eight.

'b( The propeller #hosen "or the test is not optimum "or top speed. Itmight be #hosen "or best #ruise e""i#ien#y% ma*imum a##eleration or a

#ompromise.

The engine might not have been produ#ing its rated po!er on the day o" the test. 'd( The data "or

running !eight is not al!ays a##urate.

-evertheless% I "ind it surprising that the test data "or very di""erent #ra"t is so #losely bun#hed

near the limit line.

The ra#ing rule ma)ers banned stepped hulls "rom the ;old


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Figure 9. Planing Hulls ) Har$ 4hine

Figure 10. Newg

Jn"ortunately% the heavy steam po!er plants o" that day #ould not push a hull "ast enough to

plane% and ta)e advantage o" the ne! #on#ept.

$s early as 1902 there !ere published dra!ings "or small stepped hulls !ith hard #hines. /illiam=enry Fauber @ obtained a J.S. patent "or hulls !ith multiple steps in 190@% but #ould "ind "e!

people in the J.S.$. interested% so he moved to Europe.

T!o small boats Solair '17( and 'lapper '1:( demonstrated the potential o" stepped hulls as did

the =arms!orth #hallenger Pioneer ': steps( in 1910. 'See Data


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Figure 11: Performance actors for

5acing Steppe$ Hulls&

Bet!een about 191: and 19>0% a great many motor torpedo boats and "ast patrol boats !ere built

!orld !ide% !ith stepped hulls. 10 The per"orman#e o" these #ra"t varied #onsiderably% !ithsome being very ine""i#ient.

Stepped Hull Limitations

The stepped hull maintains a nearly optimum angle o" atta#) over most o" the speed range. The

hydrodynami# hull drag is almost #onstant. The drag o" the propeller sha"t% sha"t strut and rudder%'appendage drag( in#rease as the s6uare o" the speed.

Figure 118 Per"orman#e Fa#tors "or 5a#ing Stepped =ulls.

The graph o" Per"orman#e Fa#tors sho!s a#tual speed datao" di""erent prominent ra#ing stepped hulls. The data points

are numbered and re"er to numbers on the data #hart Figure17. The boats are numbered in se6uen#e a##ording to theyear !hen the speeds !ere established. The se6uential

in#reases in po!er "a#tor re"le#t engine development and nothull development. -oti#e that most o" these boats per"orm

almost on the limit line. ;ar /oods #iss %mericas !erereally 6uite ine""i#ient. Many stepped hulls "rom England!ere signi"i#antly more e""i#ient and o"ten "aster. They "ailed

to !in ra#es be#ause o" a la#) o" strength and me#hani#alreliability. The very streamlined %lagi !as slightly moree""i#ient than the others.

Stepped hulls are di""i#ult to design. There are many designvariables #ompared to the design o" a &ee bottomed

monohull. I do not )no! o" any a##urate method available tooptimie stepped hull design other than by model testing.

Stepped hulls dominated ra#e boat design until about 194@ !hen $dolph $pel patented the three

point hydroplane #on"iguration. &entnor three point hydroplanes dominated small limited #lassra#ing% yet stepped hulls !ere running #ompetitively in Jnlimited #lass ra#ing up until 19>9. In

19:0% Slo-#o-Sh$n demonstrated prop riding and boosted the !orld speed re#ord signi"i#antly.'More on prop riding later.(

Stepped hulls de"initely have the potential o" being signi"i#antly more e""i#ient than rnonohulls.


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'd( There !ere many huge !ar,surplus air#ra"t engines available a"ter the

"irst !orld !ar% at reasonable pri#es% and "e! light !eight marine enginesavailable. It !as easier% 'and possibly #heaper( to buy a big engine "or amonohull% than to develop an e""i#ient stepped hull.

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RACING HULLS

NAME YEAR

LENGH !EAMRUN

"EIGH

L!

#$"ERH#

S#EE%M#H

#$"ERFAC$R

S#EE%FAC$R

%IS#LACEMEN HULLS &R'u() !'**'+e),

6a7 Standard 80. 0( ()* -.00 110 30 1-&32 &-

6b7 Vingt et Un II 80. 32:)9* .:)* .-00 - . 1&9 12&2

6c7 Chip 80- ()3* 30 1-&3 0& &0 12&1

6$7 Dixie 80- .0( -()* -- 1-0 &. 19&-9 0&.26e7 Dixie II 802 39:)9* -().* .00 0 3-&2 .3&. 3-&2

HAR% CHINE% #LANING HULL

617 Vida IV 80 1-( 130 1. - &9 3&0.

SE##E% HULLS

617 Solair 810 1( 1-- 0 . -3& ..&9

67 Flapper 810 1-( 20 .0 . & -0&1

637 Miranda IV ( -:)11* 3-00 11- .0&3 & 3&

6.7 Dixie IV 811 39()* ()11* 2-. ..0 .-& 39&. 3&0

6-7 Newg 8- 12()* .:)10* 12- 90 .- .-&2 .0&2

67 Amer VI 82 .-0 00 20 .9&9 -2&.

67 Estelle IV 89 3-( 9()* 93-0 000 10- 1.&. &3.

627 England II 830 32()* 10()* 1.1-0 300 99 13&-9 3&

697 England III 83 3-( 9:)* 10-00 ..00 10&- 23& 21&.3

6107 Amer X 833 32( 9:)2* 1.1-0 00 1- 3.-&3- 20&3

6117 Delphine IX 833 ( 2:)* .00 --0 - 9& -2&1

617 Britan III 833 .( .39 13- 110 ..&3 2-&9.6137 Blue Bird 83 3( -9- 1-0 10 9&- 29&

61.7 Alagi 832 0( 00 .-0 91&. 1.& &9

61-7 Canada III 839 -( 3-0 1000 100 -&2 2&

617 Canada III 3200 1-0 10 3.& 9&1

617 Canada III 3-0 .-0 113&2 3

6127 Canada IV 8-0 33( --00 3000 1.3 .10&- 10&

6197 !epsi 8-0 3( 1()* 1.30 ;3-00

10 12- 10-&

Aerodynamics


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Figure 13.


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Figure 14, shows Performance actorsfor Stern Dri"e Pleasure oats

Engine !eight is a"t o" mid length% and the propeller sha"t angle is less in#lined than !ith a dire#t

drive. =aving the !eight a"t tends to li"t the bo! o" the boat% as does the more level thrust line o"the propeller. The hull be#omes more e""i#ient at high speed than the dire#t drive monohull.

Stern-Drive

The engine is a"t against the transom !ith the drive sha"t going a"t through the transom above the!ater line into a right angle gear bo* mounted a"t o" the transom. The drive goes do!n into

another right angle gear bo* !hi#h #ontains the propeller sha"t.

Engine !eight is "ull a"t% and the propeller thrust line is basi#ally parallel to the )eel. Moderndesigns are hydrauli#ally adustable so that the propeller sha"t angle #an be varied up or do!n.

Jp!ard thrust o" the propeller helps a monohull get up on plane. Do!n!ard thrust o" the propeller helps to li"t the bo! at high speeds. 'More e""i#ient "or this hull.( The stern drive is the

most #ommon drive system '!ith inboard engine( "or modern planing pleasure #ra"t. $ hard#hined monohull !ith a stern drive% is almost as e""i#ient as a stepped hull. '/ith the samedeadrise and a pra#ti#al po!er range.(

The monohull is mu#h easier to design than a stepped hull. /hen !e #onsider that the number o"designers o" good stepped ra#ing hulls in the past !as probably no more than a hal" doen% !e #an

understand !hy the large volume boat manu"a#turers o" today avoid su#h #omple* designs.

Figure 1>% sho!s Per"orman#e Fa#tors "or Stern DrivePleasure Boats The small #ir#les represent data points "rom

a#tual boat tests published in 1997. The limit line is alsosho!n. The boats tested in 19@> and prior years !eresigni"i#antly less e""i#ient. The limit line !as "urther to the

le"t. 4

The general #hara#teristi#s o" the +imit +ine are similar to

!hat !e have seen "or dire#t drive monohulls and dire#tdrive stepped hulls. $s the speed in#reases% the po!erre6uirements in#rease.

Surace Drives

$ sur"a#e drive is one in !hi#h only the lo!er hal" o" the

propeller is in the !ater. This !as tried by $lbert =i#)manon his Sea Sleds in the late teens and on ainbo! I& in197>. 1 In these appli#ations% the propeller sha"t !ent a"t

"rom the engine and through the transom ust above the bottom o" the boat. $s the propeller rotates% only one hal"

o" the blades are in the !ater at a time. $ three or "our bladed propeller is used in order to redu#ethe vibrations #aused by blade impa#ts. It is a #hara#teristi# o" sur"a#e pier#ing propellers to shoota great plume o" !ater out behind the boat.

The 5oostertail is evident in photos o" ainbo! I& '197>( and o" =i#)mans SeaSleds '1970, (.l Sur"a#e pier#ing propellers must have a larger diameter than submerged propellers be#ause not

all o" the blade area is !or)ing at any one time.

The advantage o" the sur"a#e drive is that It eliminates the drag o" the propeller sha"t and sha"t

strut% and part o" the rudder area. -either #ra"t ust des#ribed e*hibited any really signi"i#ant gainsin speed. 'This !ill be e*plained later.(


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!odern Developments

The sur"a#e pier#ing propeller !as redis#overed almost by a##ident by three di""erent ra#e boats%in three di""erent #ountries in the late 19>0s.

'$( Bl$ebird

In 1949 Sir Mal#olm : mph. the transom started to li"t. The transom mounted engine#ooling !ater pi#)up !ould #ome out o" the !ater and the engine !ould overheat. /ith the !ater

pi#)up relo#ated to a "or!ard sponson% a speed o" 120 mph. !as a#hieved. /hen the stern li"ted%

the propeller #ame part !ay out o" the !ater and be#ame a sur"a#e pier#ing propeller.

$s the propeller rotates% the blades #ome out o" the !ater% travel through the air% and then #ome

do!n out o" the air and into the !ater !ith #onsiderable impa#t "or#e. This impa#t "or#e is seen asa li"ting "or#e on the propeller sha"t. It is this li"ting "or#e !hi#h supports the a"t end o" the boat.The a"t end o" the boat rides on the propeller "or#e% thus the name Prop 5ider.

The propeller sha"t% sha"t strut and part o" the rudder are li"ted out o" the !ater. This eliminatesmu#h o" the appendage drag and allo!s a #onsiderable in#rease in speed.

The angle o" the Bluebirds sponson bottoms !as then #hanged so that they !ould have ane""i#ient angle o" atta#) a"ter the stern li"ted o"" the !ater. $ speed o" 130 mph. !as rea#hed

be"ore the #ra"t hit a "loating log and !as too badly damaged to rebuild.

'B( #iss CanadaI&

In 19>@ =arold /ilson established a -orth $meri#an re#ord o" 14@ Mph. in a t!o step hydroplane

designed by Doug &an Patten. 1> $lmost the same speed that Mal#olm


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Figure 1-, Performance actors of Different

4onfigurations

transom. Gn the $rneson system the short propeller sha"t is pivoted about a verti#al a*is "or

steering. These drives e*hibited some speed in#rease !hen installed on G""shore ra#ing tunnelhulls% but nothing near the speed in#reases seen on three point hydroplanes. ainbo! I& and theSeasleds did not e*hibit great in#reases in speed in their day either.

Modern sur"a#e drives use super#avitating propellers. Gn a super#avitating propeller% the !aterseparates "rom the su#tion "a#e o" the blade and leaves an air #avity bet!een the !ater and the

blade "a#e. The #avity e*tends a"t o" the trailing edge o" the blade. Sometimes the trailing edge o"the blade is made very blunt or "lat. These are #alled #leaver propellers.

"uture

It all goes ba#) to the "a#tors !hi#h limit the per"orman#e o" any vee bottomed planing hull. Theangle o" atta#) o" the hull planing sur"a#e relative to the !ater sur"a#e.

The sur"a#e drive has t!o "a#tors !or)ing against the monohull. The propeller li"t "or#es '!hi#hare !ell a"t o" the transom on the $rneson drive(% and the propeller thrust line !hi#h is high andnear the bottom o" the hull. Both these "a#tors tend to push the bo! o" the hull do!n% "latten the

trim angle and ma)e the hull less e""i#ient. $ny gains "rom redu#tion in appendage drag are o""set by an in#rease in hull drag. The boat does not travel signi"i#antly "aster. The redu#tion o" one set

o" drag "or#es is o""set by the in#rease in another set o" drag "or#es.

The idea is to #ombine the e""i#ien#y o" the sur"a#e drive !ith a hull that !ill have ma*imume""i#ien#y% in spite o" the prop li"t o" the sur"a#e drive. This re6uires a stepped hull.

I #all the #ombination o" sur"a#e drive and stepped hull% a Sur-Step. The potential gains "romsu#h a #ombination are #onsiderable.

-o! you #an see !hy a study o" hull design history is desirable. It enables us to loo) at the overall

advan#e o" te#hnology !ithout getting buried in minute details.

Perormance Comparison

Figure 12 sho!s the potential speeds "or "our di""erenttypes o" boat in the 1@ to 70 length range. The hull!eight is "i*ed. The running !eight is adusted "or

engine sie% and drive type !eight. @y using a single boat sie% the numbers should be more meaning"ul to

the average reader.

The Sur",Step is about @ mph. "aster than a steppedhull% or 17 mph "aster than a stern drive !ith the same

po!er. This magnitude o" gain is !orth pursuing.

Sur-Step

;eneral design


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Figure 16, Horsepower "s& Spee$ for$ifferent configurations&

area is redu#ed and runa!ay #avitation is less li)ely to

o##ur.

I pre"er to e*tend the hull bottom a"t on either side o"the propeller to redu#e hull drag during the pro#ess o"

getting up onto a plane. This should "urther redu#e propeller loading at that #riti#al speed.

$ "urther enhan#ement !ould be to pla#e a shroudaround the upper se#tion o" the propeller. $ lip on theshroud a"t o" the propeller !ill help pressurie the

!ater at the propeller diameter.

I" the shroud e*tends out to the hull side e*tensions%

the propeller !ill be operating in a trun#ated tunnel.

The designer must be a!are o" the "a#t that a propellerdra!s in !ater "rom a dis# area !hi#h is signi"i#antly

larger than the propeller diameter.

The primary hull step must be lo#ated "or!ard o" the e""e#tive #enter o" pressure in order to

prevent porpoising.

The large li"ting "or#es produ#ed by the sur"a#e pier#ing propeller% move the #enter o" pressure!ell "or!ard o" the stati# #enter o" gravity.

Dual Deadrise


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Some #ombinations do not promise signi"i#ant improvements in Per"orman#e +imits. $ stepped

hull !ith a stern drive is only slightly better than a rnonohull !ith a stern drive. The monohull!ith a sur"a#e drive is only slightly better than a monohull !ith a stern drive.

It is the #ombination o" sur"a#e drive and stepped hull !hi#h #an produ#e signi"i#ant

improvements in e""i#ien#y "or pleasure #ra"t. 'Jp to >0K less po!er re6uired.(

The tas) o" designing an e""e#tive Sur",Step #ra"t !ill re6uire the #ombined %e""ort o" hull designer

and propulsion system designer. Mu#h o" the te#hnology is available. The drive system is#omple*. Stepped hulls are mu#h more di""i#ult to design than monohulls% and some o" the designse#rets !hi#h have passed on !ith the old designers might have to be relearned. Dont e*pe#t the

"irst prototype to per"orm at the +imit +ine. The potential gains are still substantial.

#eerences

l D./.Fostle% Speedboat Mysti# Seaport Museum% 19@@

7 +indsay +ord% -aval $r#hite#ture o" Planing =ulls%

4 Daniel Savits)y% =ydrodynami# Design o" Planing =ulls Marine Te#hnology% G#tober% 192>

> Morley S. Smith =o! Fast /ill It ;o So#iety o" Small


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70 Donald +.Blount David +. Fo*% Small,


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is to optimie the hydrodynami# drag o" the hull. There is little to be gained by trying to improve

or optimie anything but the hydrodynami# drag. 4 1@ 19

Gn high speed boats% the appendage drag% aerodynami# drag% and appendage li"t "or#es #an be verylarge. 'These "or#es in#rease as the s6uare o" the speed.( +i"t produ#ed by the angled propeller

sha"t o" a dire#t drive system shi"ts the e""e#tive #enter o" gravity 'or #enter o" hydrodynami# pressure seen by the hull(% "or!ard. The angle o" atta#) o" the hull de#reases% and the hull drag

in#reases. The real optimum #hine beam "or this high speed hull !ill be di""erent than it !ould bei" sha"t li"t !ere ignored in the #al#ulations. The !hole system must be #onsidered during thedesign stage o" high speed boats. 70

Limit Lines

The limit lines sho!n on the graphs are mathemati#al e*pressions !hi#h are valid "or the

parti#ular #ombination o" hull type and drive system being investigated. Gne e6uation should#over all o" the #ra"t o" a given #ombination.

The naval ar#hite#t #an develop a mathemati#al e6uation !hi#h !ill #losely appro*imate the limit

line. The basis o" the e6uation is that the horsepo!er put out by the engine e6uals the total o" all o"the losses and drag "or#es in the system. This e6uation in#ludes "a#tors su#h as8 transmission

losses% propeller slip% aerodynami# drag% hull drag% appendage drag% 'rudder% propeller sha"t% strut%et#.(

By using su#h e6uations% the naval ar#hite#t )no!s !here the horsepo!er goes and !hi#h losses

are greatest.

/hen #al#ulating the hydrodynami# drag o" a planing hull% the designer must ta)e into a##ount theli"t "or#es on the in#lined propeller sha"t and rudder% and the su#tion "or#es produ#ed by the

propeller on the hull.


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'5eprinted "rom Speed Boat De*elopments from the Past Into the '$t$re by Morley S. Smith%

Freeville% -(

H!$roplane Histor! Home Page%his page was last re"ise$ %hurs$a!, gmail&com

? 'eslie iel$, 001

Speed Boat Developments

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