Aluminium Ore Carriers

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A l u m i n u m

O r e C a r r i e r s '

BY DAVID ~IACINTYRE, ~ I E M B E R 2 T O P I C A L O U T L I N E Introduction Historical Considerations D e v e l o p m e n t of the Project The Ship Designs

Tables of Principal Characteristics Hull Construction

Tables of F u n d a m e n t a l Design Comparisons; Form, Structure, Speed, Weights, and Bid Prices Structural Tests F u n d a m e n t a l Design Comparisons Economic Analysis Some Conclusions Availability of Materials

Growth of Aluminum Uses for M e r c h a n t Ship Construction

Standardization and Regulation References

minum and aluminum alloys in general are highly resistant to corrosion, and the alloys recommended for shipbuilding have been developed for the highest corrosion resistance to sea water consistent with high strength and workability. In a paper b y Forrest [14], the approach used in the design of the aluminum-hulled bauxite carriers was fundamentally considered. T h e properties of the structural alloy recommended, Alcoa 61S-T6, were provided in his paper, together with the pro- cedure used in computing the strength of the aluminum-hulled ships.

A secondary purpose of the paper is to suggest trades and vessels in the G r e a t Lakes area in which aluminum can be used advantageously for hulls, topside and other structures and equipment. Mention "also will be made of improvements in alloys and practices for shipbuilding de/zeloped since the aluminum-hulled ore carrier project was shelved.

INTRODUCTION

T h e prime purpose of this paper is to describe the aluminum-hulled bauxite ore carriers proposed for Alcoa Steamship C o m p a n y in 1945 and to provide structural and economic comparisons with the steel-hulled bauxite carriers of equivalent dimensions proposed at the same time. Although the aluminum-hulled ore carriers were not built, the world-wide maritime interest in the proposal has continued. I t seems appropriate, therefore, to divulge details of the project for the record of progress in naval architecture and for the information of the shipping and shipbuilding industries. F u t u r e design and construction of aluminum- hulled ships should benefit from this revelation and from its discussion.

The resistance of aluminum alloys to marine ex- posures has been covered by Mears and Brown [10] 3 and b y Walton and Englehart [24]. Alu-

1 Paper presented at the annual meeting of T h e Great Lakes Sec- t i o n of T h e Society of Naval Architects and Marine Engineers January 25, 19,52.

Head, Marine Section, Sales D e v e l o p m e n t Division, A l u m i n u m C o m p a n y of America, Pittsburgh, Pa.

3 Numbers in parentheses indicate references at end of paper.

HISTORICAL CONSIDERATIONS

After the invention b y Charles Martin Hall in 1886 of the electro-chemical process for smelting aluminum, naval authorities were a t t r a c t e d b y the increasing production and decreasing price of the metal, in addition to its light weight. In 1893, t h e year this Society was founded, an aluminum- hulled y a c h t was launched in Paris, and two years later a 55-ft, steam-turbined aluminum-hulled torpedo boat was built in Britain. In 1895, the first papers on aluminum in ship construction were presented b y Yarrow [1 ] in Britain and Mc- Guire [2] in the United States. T h e early aluminum hulls were very expensive and only par- tially successful in performance because suitable aluminum alloys and building practices had not been developed.

T h e aluminum industry waited 35 years before again advocating the light metal for ship construction. In 1930, Faragher [4] presented a paper on aluminum for ship construction before this Society to prove aluminum as a structural material for shipbuilding.

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A L U M I N U M O R E C A R R I E R S 545 Progress thereafter quickened. T h e U. S.

N a v y began utilizing the new marine alloys rec- o m m e n d e d for topside structures. T h e particular alloys a d o p t e d as s t a n d a r d in U. S. N a v a l practice were Alcoa 52S for sheet, Alcoa 53S for plate, rolled or extruded shapes a n d rivets, and Alcoa 195 alloy for castings. B y the o u t b r e a k of World W a r I I , over 100 U. S. N a v a l v e s s e l s - - m o s t l y destroyers, cruisers a n d aircraft c a r r i e r s - - were equipped with a l u m i n u m topside structures. Very few m e r c h a n t ship installations were m a d e before the war, the only ones of importance being in the three N e w York City ferries built with a l u m i n u m deck and pilot houses in 1937.

During World W a r I I , the use of a l u m i n u m in n a v a l vessels was practically suspended because of the enormous d e m a n d s of military aircraft production. T o m e e t the aircraft requirements the United States a l u m i n u m industry was expanded to an annual c a p a c i t y of over a million short tons, seven times the prewar production. Postwar it was expected t h a t over half of this c a p a c i t y would remain in economic production.

During 1944, a l u m i n u m production went over the h u m p and a n u m b e r of the government- owned smelting plants were closed. Postwar planning became inevitable considering the plen- teous a l u m i n u m production facilities.

Consideration had to be given to the increased i m p o r t a t i o n of foreign high-grade bauxite ore. During the war the domestic sources of high-grade ore h a d been rapidly depleted in supplying the a l u m i n u m industry war effort. T o handle the increased postwar importation of bauxite new ore carriers became essential.

Before the war, experimentation and tests h a d begun on Alcoa alloy 61S, a higher strength a l u m i n u m - m a g n e s i u m silicide alloy t h a n 53S. During the war, 61S proved so serviceable t h a t it was a d o p t e d in 1945 as a s t a n d a r d structural alloy of particular value for marine use. I n 1946, the first United States ocean-going m e r c h a n t ships were equipped with a l u m i n u m deckhouses using 61S alloy.

DEVELOPMENT OF THE PROJECT

Although Alcoa mines bauxite in Arkansas, the bulk of the high-grade ore used b y the c o m p a n y is imported from Surinam, or D u t c h Guiana, S. A. T h e bauxite is transported in ships of the Alcoa Steamship C o m p a n y for delivery to American mainland plants where it is processed into alumina, the white powder f r o m which a l u m i n u m is produced. T h e overseas flow of bauxite led to the development of specialized types of ore carriers.

T h e mines in Surinam are at two locations, one

a t P a r a n a m on the Suriname River and the other a t Moengo on the Cottica River. T h e Cottica flows into the Commewijne River, a t r i b u t a r y of the Suriname. There is a b a r a t the Confluence of the Commewijne with the Suriname which limits vessel draft. In addition to river bars there is also a b a r a t the m o u t h of the Suriname where it emp- ties into the Atlantic Ocean, limiting draft.

After s t u d y of p o s t w a r plans for transporting bauxite from Suriname, it was decided t h a t the m o s t economical integration would involve the use of several shallow d r a f t ore carriers to shuttle between the mines and Trinidad, B. W. I. A t Trinidad, transfer would be m a d e to various types of deep d r a f t vessels for carriage to Mobile. T h e plans also required the construction of a T r a n s f e r Station near Port-of-Spain, Trinidad. A t this station, now operating, bauxite is either trans- ferred directly from the shuttle ships to the deep d r a f t vessels or is unloaded into storage silos for later deep d r a f t ship loading.

Since 1930, Alcoa has sustained an organized effort to p r o m o t e a l u m i n u m alloys for ship construction. After the war, with the price of a l u m i n u m 2 5 % less t h a n in 1939 a n d with increased m e t a l production, the chances appeared excellent for utilizing a l u m i n u m in a substantial w a y for specific types of m e r c h a n t ships. Bulk carriers in regular services, especially when operating in limited channels, a p p e a r e d as one of the m o s t desirable for a l u m i n u m hull construction. I t appeared logical t h a t the Alcoa Steamship C o m p a n y could benefit f r o m the p o s t w a r alumi- n u m situation and t h a t demonstration of the first serious promotion of an all-aluminum m e r c h a n t ship should be with them.

T h e t o t a l n u m b e r of shuttle ships required h a d not then been determined, b u t it appeared t h a t several would be required for the postwar opera- tions.

T h e studies m a d e indicated t h a t two sizes of shuttle vessels should be considered, one limited to a length of 330 ft and a draft of a b o u t 18 ft; the other limited in draft, b u t without limit on length other t h a n dictated b y structural design proportions. L a t e r s t u d y showed t h a t the length of the latter ship should be close to 400 ft. I t was then decided to proceed with two designs, one aluminum-hulled and one steel-hulled for each of two sizes. T h e larger ships, it was decided, should h a v e a length of 400 ft, bp, hereinafter called Carriers " A , " and t h a t the smaller ships should h a v e a length of 330 ft, bp, hereinafter re- ferred to as Carriers " B . "

T h e r e was no experience to refer to in m e r c h a n t ship a l u m i n u m hull design. After the preliminary designs had been studied, it became necessary to

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546 A L U M I N U M O R E C A R R I E R S

conduct a n u m b e r of tests to establish basic values for the design of the a l u m i n u m ships' girders. F r o m these tests t e n t a t i v e agreements were reached on f u n d a m e n t a l considerations for strength, stiffness and allowances for corrosion. These tests will be described in some detail later. A t the s t a r t there was a tendency to favor too m a n y items of machinery, outfit and equipment in aluminum, b u t these were eliminated before the final consideration. There is a difference between an all-aluminum ship and an aluminum-hulled ship. I t is the consideration of the latter t h a t principally concerns us here.

Six shipyards were finally invited to bid. Dur- ing the time bids were being prepared, the shipyards were provided with considerable consultation and detailed information on aluminum. T h e novelty of the material for ship construction, the lack of reliable information on costs, shipyard practices a n d procedures, the consideration of new e q u i p m e n t requirements, a n d the difficulty of obtaining quotations on ship equipment, led to delay in m a k i n g up the bids. One shipyard carried out extensive fabrication tests to arrive a t estimation of structural costs. These tests will be described later.

T h e bids s u b m i t t e d were considered so high t h a t a considerable reduction in price appeared as necessary to m a k e building a possibility. I t was then decided to a t t e m p t to negotiate a contract with the low bidder for the construction of one aluminum-hulled ship, since no reduction in price appeared possible in the face of advancing ship- y a r d costs w i t h o u t considerable changes in the specifications. I t was decided to m a k e drastic specification changes. This decision envisioned stripping the vessel of all superfluous a l u m i n u m requirements.

All factors contributing toward the lowest priced vessel possible under the conditions then existing were investigated and exhausted. Thus, early in 1948, Alcoa was forced to state t h a t it had dropped the plans for building the ship because of

a prohibitively high price. A p r e m i u m of 3 5 % appeared to be too high for a gain in carrying c a p a c i t y of only a b o u t half t h a t percentage.

THE SHIP I~)ESIGNS

T h e plans and specifications for the four designs of ships involved are v e r y complete, especially those for the aluminum-hulled vessels. T h e y can only be briefly a b s t r a c t e d for description here.

All four vessels are similar in o u t b o a r d profile as shown in Fig. I for Carriers " A . " I t will be noted t h a t t h e y are typical ore carriers in appear- ance, with raked stems, semi-cruiser sterns and m a c h i n e r y aft. T h e r e is one complete deck, a long poop deck on which a superstructure is mounted, and a short forecastle.

T h e general a r r a n g e m e n t s and l a y o u t of spaces of Carriers " A " are as shown in Figs. 2 a n d 3. I n addition to six bauxite holds, there is a forward 'tween deck space for carrying a small a m o u n t of general cargo a n d for the Surinam mines supply. Stores are arranged for carriage b o t h a f t and in the forecastle. Fuel and cargo oil are arranged for carriage b o t h in the double b o t t o m and in the wing c o m p a r t m e n t tanks, with fresh w a t e r also in wing tanks. T h e crews' quarters are located aft, with ratings on the main deck, officers on the poop a n d b o a t decks and space for 12 passengers on the poop deck.

T h e general a r r a n g e m e n t s of Carriers " B " are essentially the same as Carriers " A , " except t h a t there are only four bauxite holds, smaller crew a c c o m m o d a t i o n s and space for eight passengers. T h e principal characteristics of the four designs of vessels are given for Carriers " A " in T a b l e 1A, and for Carriers " B " in T a b l e lB. Included are the principal hull dimensions, summaries of cargo and t a n k capacities and particulars of the pro- pelling machinery. T h e designs were predicated on a regular service allowing 48 voyages per y e a r for bauxite transfer, with y e a r l y periodic trips to Mobile, Ala., for d r y docking and overhaul.

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A L U M I N U M O R E C A R R I E R S 549 TABLE 1A.--CARRIERS " A , " ALUMINUM HULL AND

STEEL HULL SHIPS, PRINCIPAL CHARACTERISTICS L e n g t h o v e r a l l . . . 422 ft 0 in. L e n g t h b p . . . 400 f t 0 in. B r e a d t h , m o l d e d . . . 60 f t 0 in. D e p t h t o m a i n d e c k a t side, m o l d e d 28 f t 0 in. D r a f t , m a x i m u m m o l d e d . . . 20 f t 0 in. D i s p l a c e m e n t a t 20 f t 0 in. d r a f t . . . 10,2;32 t o n s Officers a n d c r e w . . . 42 P a s s e n g e r s , m a x i m u m . . . 12 P r o p e l l i n g m a c h i n e r y : One set of h i g h - s p e e d , c r o s s - c o m - p o u n d s t e a m t u r b i n e s d o u b l e - r e d u c t i o n g e a r e d to a single s h a f t N o r m a l sAp . . . 3000 R p m n o r m a l , a b o u t . . . 110 T w o h e a d e r t y p e w a t e r t u b e boilers a t 425 psig 750 ° F S p e e d , k n o t s . . . 12 C a r g o c a p a c i t i e s : B a u x i t e h o l d s . . . 250,935 cu f t D r y cargo . . . 29,405 cu ft T o t a l c a r g o c a p a c i t y . . . 280,340 cu ft T a n k c a p a c i t i e s : F u e l oil . . . 182.8 t o n s F r e s h w a t e r . . . 147.3 t o n s C a r g o fuel oil . . . 183.6 t o n s C a r g o D i e s e l oil . . . 45.9 t o n s S a l t w a t e r b a l l a s t . . . 3983.0 t o n s T o t a l t a n k c a p a c i t y 4542.6 t o n s E c o n o m i c s t u d i e s of b o t h D i e s e l a n d s t e a m p o w e r w e r e i n c l u d e d in t h e p r o j e c t in o r d e r t o de- t e r m i n e t h e i r r e l a t i v e a d v a n t a g e s . I t w a s d e c i d e d t h a t in t h e d e s i g n of C a r r i e r s " A , " s t e a m t u r b i n e s w o u l d b e s t u d i e d , while Diesels were s e l e c t e d for C a r r i e r s " B . " F i n a l a n a l y s e s s h o w e d t h a t t h e r e w a s no s u b s t a n t i a l difference in o p e r a t i n g costs. T h e r e is no specific n e e d for t h e p u r p o s e s of t h i s p a p e r t o g i v e a d e t a i l e d d e s c r i p t i o n of t h e m a c h i n - ery. T h e p r i n c i p a l c h a r a c t e r i s t i c s a r e b r i e f l y g i v e n in T a b l e 1A for C a r r i e r s " A " a n d in T a b l e 1B for C a r r i e r s " B . " F o r e a c h size of ship, r e s p e c t i v e l y , t h e d i m e n s i o n s , f o r m , full l o a d d r a f t a n d d i s p l a c e - m e n t were i d e n t i c a l for t h e a l u m i n u m a n d steel hulls a n d t h e r e f o r e t h e s a m e p o w e r a n d p r o p u l s i o n r e q u i r e m e n t s o b t a i n e d . T h e g e n e r a l a r r a n g e m e n t p l a n s a n d m i d s h i p s e c t i o n s s h o w t h e h o l d s a n d t a n k l o c a t i o n s suf- f i c i e n t l y well t o o m i t p r o v i d i n g c a p a c i t y p l a n s . T h e s u m m a r i e s of c a r g o a n d t a n k c a p a c i t i e s g i v e n in T a b l e s 1A a n d 1B, a l o n g w i t h t h e b r e a k d o w n of hull, m a c h i n e r y a n d o u t f i t w e i g h t s p r o v i d e d in T a b l e 4, s u p p l y e n o u g h d a t a t o m a k e c a r g o c a p a c - i t y a n d o t h e r w e i g h t c o m p a r i s o n s . I n t h e final c l a r i f i c a t i o n of C a r r i e r s " A " a l u m i -

TABLE lB.--CARRIERS

"B,"

ALUMINUM HULL AND STEEL HULL SHIPS, PRINCIPAL CHARACTERISTICS L e n g t h , o v e r a l l . . . 353 ft 0 in. L e n g t h b p . . . ' . . . 330 f t 0 in. B r e a d t h , m o l d e d . . . 54 f t 0 in. D e p t h t o m a i n d e c k a t side, m o l d e d . . 27 f t 0 in. D r a f t , m a x i m u m , m o l d e d . . . 18 f t 0 in. D i s p l a c e m e n t a t 18 f t 0 in. d r a f t . . . 6800 t o n s Officers a n d c r e w . . . 37 N u m b e r s of p a s s e n g e r s , m a x i m u m . . 8 P r o p e l l i n g M a c h i n e r y : T w o D i e s e l engines g e a r e d t o a single s h a f t N o r m a l shp . . . 2000 R p m , n o r m a l , a b o u t . . . 93 S p e e d , k n o t s . . . 12 C a r g o c a p a c i t i e s : a p p r o x : B a u x i t e h o l d s . . . 154,800 c u f t G e n e r a l c a r g o h o l d . . . 12,000 c u f t T o t a l c a r g o c a p a c i t y . . . 166,800 eu f t T a n k c a p a c i t i e s , a p p r o x . : D i e s e l fuel oil . . . F r e s h w a t e r . . . C a r g o fuel oil . . . C a r g o D i e s e l oil . . . S a l t w a t e r b a l l a s t . . . T o t a l t a n k c a p a c i t y . . . 52 t o n s 74 t o n s 260 t o n s 70 t o n s 2879 t o n s 3335 t o n s h u m hull d e s i g n for t h e p u r p o s e s of c o n t r a c t n e g o t i a t i o n , t h e o n l y i m p o r t a n t i t e m s of a l u m i n u m e q u i p m e n t r e m a i n i n g i n c l u d e d l i f e b o a t s a n d d a v i t s , h a t c h covers, a c c o m m o d a t i o n a n d o t k e r l a d d e r s . T h e b r i d g e s a n d o t h e r t o p s i d e s t r u c - tures, s m o k e s t a c k e n c l o s u r e s a n d m a s t s r e m a i n e d in a l u m i n u m , of course. T h e j o i n e r b u l k h e a d s , d e c o r a n d f u r n i t u r e were r e t a i n e d in a l u m i n u m in k e e p i n g w i t h t h e o w n e r s h i p of t h e vessels. Es- s e n t i a l l y , in t h i s s t r i p p i n g o p e r a t i o n , t h e d e v e l o p - m e n t w a s r e t u r n e d t o t h e o r i g i n a l o b j e c t i v e w i t h t h e p r i m a r y e m p h a s i s on t h e a l u m i n u m hull. • HULL CONSTRUCTION • T h e a l u m i n u m - h u l l e d vessels w e r e d e s i g n e d t o be b u i l t p r i m a r i l y of A l c o a a l l o y 6 1 8 - T 6 of r i v e t e d c o n s t r u c t i o n u s i n g A l c o a 538-T61 r i v e t s t h r o u g h - out, w i t h s c a n t l i n g s as s h o w n on t h e m i d s h i p s e c t i o n s in Figs. 4 a n d 6. T h e s t e e l - h u l l e d s h i p s of a l l - w e l d e d c o n s t r u c t i o n a r e s h o w n w i t h s c a n t l i n g s in t h e m i d s h i p s e c t i o n s in Figs. 5 a n d 7. F o r t h e p u r p o s e of c a r r y i n g b a u x i t e in b u l k , t h e c o n s t r u c t i o n in all c a s e s is a r r a n g e d w i t h t w o longi- t u d i n a l b u l k h e a d s , t h e c e n t e r c o m p a r t m e n t f o r m - ing t h e c a r g o s p a c e a n d t h e w i n g c o m p a r t m e n t s b a l l a s t t a n k s . T h e u s u a l b a l l a s t a n d oil t a n k s are c o n t a i n e d in t h e d o u b l e b o t t o m c o n s t r u c t i o n .

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550 A L U M I N U M O R E C A R R I E R S

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Base Line .3"x 3 V2"x V2"L Cli 15/32 "

\1

Length, Overall . . . 422'- O" Length, B.I~ ... 400'- 0" Breadth. Mid ... 60'- O" Depth fo Mare Deck at S~de.MId ... 28'- O" Draft, Maximum Mid ... 20'- O"

Sect. T - - - - ] ~ 3 / ~ " Pl. Coammg -~ <- . . . 15'- 0" Clear . . . ~ . . . 4 = R o d , u s Camber ~ 7"x 7"x 7/a" L~.~ ¢

Morn Deck Plating

Outboard of Flatches I"for V2 L

Decreased to tT/32"at Ends .£ Inboard of Hatches 7A6" ~i~ Shell Plating

Sheer Stroke 53"x I!'for I/2L fo 9/W' /

Stroke Below Sheer 7/8"for I/2L

tO

g/i6" ~ . S~de Shell 3/4"for Vz L fo 9/16"at Ends

Boff0m Shell 3/4"for V2L

7/a" for '/2 L to Fore End 11/16"{or Fwd End BefowWL. Keel Plate SO'x I"

Frames fhruouf Cargo Space Wing Tanks and Peaks 8"x 3,45"X 3,45t'x 3/8" E's

Mach mer~ Space IO"x 3 40"x 3.40"x s/s" E's Fro rues in Fdc~sle and Poop 6"x hS"x 3 5"xO 34" E's Frames 15-25, IO"x &40"x 3.40"x 3/a" Ds 19'- 3" Long'l W.T. Side Stringer V2" Ph Inner Boffom

Tank Top Plating

Center Stroke 50"x 2V32"for t/2 L to gA6"ot Ends C ,OfherSfrakes 9/m"fhruoutCargo Space

enter vert. Keet 2~/32" for '/2 L to g/16"afEnds Solid Floors every Frame

Thickness in

Holds

15/s2" In Machinery Space 9/le" Tank Ends s/a" 14'-0" N.T. Long'l Girder 15/sz"

g/re" In Way of Cargo Holds On l y ~ Chain Treble 7"- N X

"~I h 5'/'¢'ChamDbl' ~ 1 ~ h ~ I

iii,

I

::

;:; 3'/2 "x 3 '/2"x Y2" L -. a',~ a,,. s/~.,'.

_.x Lt~ X = k 3 Panel Sfiffks 4"x 3V2"x 3/8" L's

. . . N T Long'l Girder 14'-O"Off C.L.- . . . q

. . . 30'-0" Mid Half Breadth . . . -~

FIG. 4--MIDSHIP SI~CTION, ALUMINUM HULL, CARRIBR " A "

Carriers "A" were designed to be built on the transverse framing system. Carriers "B" were de- signed to be built on a combination transverse and longitudinal framing system. Scantlings generally were to be as s h o w n on the midship sections, with

allowance for substitution of shapes of equal strength and stiffness provided the weight of the structure was n o t increased. Generally, for both the steel and a l u m i n u m hulls, the lightest prac- ticable sections for frames, beams, stiffeners, etc.,

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A L U M I N U M O R E C A R R I E R S 551

Frame Spacing :

F, P 4.0 20 ... 24" 20 ~o 161 ... 28" 161 4.o A.R ... 24"

Class ,~ A-I (~) American Bureauof Shipping

Main Deck has no She?r

.f Main Deck 1 ~ 5"- 8 " x 4 " x 7 / l # ' L ~ 0.575" PL-3"Fig.-.._ Spaced Every Third Frame /

All l's in Wing Tanks are 7'k4"x %" Air Brackets are 0.375" Pl.- 3" Fig. where Indicated V~TSfrim l _1 Every Frame Leng4.h Overall ... 422'-0" Length B.R ... .400'- O" Beam Molded ... 60'- 0"

Depth fo Main Deck ... 28~-0 ' Design Draft. ... 2 0 " 0 " F . . . 15'- O"Clear- . . . 1 R a d l u s C o m b e r . . . . = Coaming -d • ' ~ - 5 / 8 " ~-

Main Deck Plating

3/4" Outboard of Hatches 0.95"for V~L

Decreased 4.o ~%2"af Ends Inboard of Hatches 3/e" Shell Plating

Sheer S4.rake 50"x "~'-'/3z"for V2 L 4.0 TAB"at Ends Side Shell gAB" for '/2 L 4.0 7/}s"a4. Ends Bottom Shell gAs"for V~L4.0 7/m"af At4. End

~VsFfor V2 Lto Fore End. I7/s~"for Fwd End BeIowW.L. Keel Plate 50"x ~/4"

Boss and Heel Plates 2V32"

Aifoching Frame i9

Af4.ermosf Shell to Stern Vs~" Inner Boi-{'o m

T a n k Top Pk~4.ing ~ '

rrs.29 4"o 13~ _.i

Center Stroke 5O"x ~Vm"

Other S4.rakes Inboard ofl7LO '' 5/8" Other Strokes Outboard of 17'-0" 7Ao" Margin Pl. V2"

Frs. 14 4.0 29 7/16"Margin P!,V2"

Aft of Fr. 134 V2"

Cen4.er Vertical Keel V2" for I/2 L+o 7./16"af Ends Solid Floors every Frame

Thtckness in Holds 3/8"Tonk End5 F2" Machinery Spaces 7,4'6"

N.T. Girder I4'-0" Off C.L %"Ligh4.ened wRh 16"x 20"Holes TAB"in Machinery Space Frames fhruouf Cargo Space Wing Tanks anti Peaks

7"x 4"x s/B"lnv, f.-

Machinery Space 8"x4"x TAB"Inv. L Frames in Foc's'le and Poop 6"xS'/s"x ¥8"lnv.L Frames 15 fo 26, 8"x 4"x 7/b" Inv, L.

Plating and Shffeners on Long'l Sloping B'h'ds fhruouf Cargo

~'TAe" Spaces as Indica4.ed

S4.ringer Plate 19L3"Above Base Line 13/32" . . . , 7 ' - o " o f f c L . ! d ...

. . . 4 ' - 9 L' . . . * ~ . . . 4'-9'-' . . . , "( . . . 4'-8'~ . . . t . . . NT. k o n g ' l G i r d e r 14'-o'roff C . L - . . . i ~ - . . . 5 0 ' - 0 " M i d H a l f B r e a d t h . . . *-J

F I G . 5 - - M I D S H I P S E C T I O N , S T E E L H U L L , C A R R I E R " A "

were to be used to meet classification society re- quirements.

In the case of the steel ships, no difficulty in re- gar d to design or construction of the hulls w a s

anticipated. The designs were normaI in every

respect, with all work to be in accordance with the requirements of the American Bureau of Shipping and the U. S. Coast Guard Bureau of Marine In-

spection where applicable. In view of the 100

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552 A L U M I N U M O R E C A R R I E R S

Frame Spacing :

0 % 15_ .. . . 24" 13 1,o 141 . . . 27" 141 Af-t . . . 24" Class (Experimenfal) @ A'I ( ~

American Bureau of SRipping All Maferial shown t'o be Aluminum Alloy

Plafes and Shapes ... Alcoa 61S-T6

R i v e t s . . . Alcoa 5 3 5 - T 6 1 6"X 6"x 3/4" Gunwale L Main Deck ~ / ! 3/4"~, 6.!

l

i i

k

Lengfh Overall ... 5 5 5 ' - 0 " L e n g t h [3. R . . . - . . . 3 5 0 L ' 0 '' 1 3 r ead 1 , h Mi d . . . 5 4 ' - 0 "

Depfh fo Main Deck af Side Mid . . . 27L0 '' Draft, Max. Mid . . . 18: 0"

6 " x S W ' x V 2 " L ~ 10"x 5">: 10.55"E - - ~ _ Dbl. Riv. L's Around Corners of Hafche: " 6 Spaces ~ 2:0"=

!--T

,aming ~t --~ . . . . I 1'-3" C l e a r . . . ~E - I8"Camber L 10"x 6.9 Lb. E a f Ord. Frames- }5"x 12.4 Lb.E a f Web Frames

19'- 9"to C.L.

5"x V2"L

. . . . Main Deck Plating

Outboa rd of Hatches 3/4" Decreased af Ends

Shell Plating

Sheer S~-rake 5/4"for V2 L to 7,46" Sfrake Below Sheer s/#' for V2 L to zA6" Side Shell s/8"for Vz L+o 7/16"af Ends ~ - Boffam Shell S/s" Decreased af Ends

Keel Plate 72"x 7/8"

~, Frames Thruouf Cargo Space Wing Tanks ' c 15"x 12.4 Lb. L's

Boi%m Long'Is 15"x 12.4- Lb. E's Deck Long'Is 8"x 641 Lb. or 7.85 kb. E's Inner [3offom

Tank Top Plating g2"wlfh Yz"Doublers Cenfer Vert. Keel 72"x 0158 II

< Solid Floors af Web Frame Y2" Web Frames 9'-O"Aparf

i ~o 22'-6" N,T Long'l Girder V2" I =, o~ _1 i I 1'-5'-' . . . ,- y / ,~r m "

oseL,o ]

]

[

I - - F I G . ( ) - - M I D S H I P S E C T I O N , A L U M I N U M H U L L , C A R R I E R " B "

c o n s t r u c t i o n of iron a n d steel ships, w i t h o v e r s i x t y for m i l d stee! a s t h e W o r l d - w i d e a c c e p t e d s t a n d a r d m a t e r i a l for b u i l d i n g m o d e r n vessels, t h i s is u n d e r s t a n d a b l e . T h e g e n e r a l a c c e p t a n c e of e l e c t r i c w e l d i n g in t h e c o n s t r u c t i o n of steel s h i p s

since its i n c e p t i o n 30 y e a r s ago, a n d its g e n e r a l use o v e r t h e p a s t 15 y e a r s , m a d e w e l d e d m i l d steel c o n s t r u c t i o n a n i n e v i t a b l e choice for t h e steel- h u l l e d ore c a r r i e r s c o n t e m p l a t e d , b o t h for e c o n o m y as well as for p u r p o s e s of c o m p a r i s o n .

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A L U M I N U M O R E C A R R I E R S 553 TABLE 2.--FUNDAMENTAL DESIGN COMPARISONS

OF CARRIERS " A " AND " B , "

FORM,

STRUCTURE AND SPEED CHARACTERISTICS

Carriers " A . " Carriers " B . " Dimensions A l u m i n u m A l u m i n u m

hull and steel hull and steel hull ships -hull ships lbp lwl B r e a d t h D e p t h D r a f t , lwl D i s p l a c e m e n t , mld. s . w . Block coefficient Mid-section coefficient P r i s m a t i c coefficient L e n g t h to b e a m ratio,

L/B

L e n g t h to d e p t h ratio,

L/D

B e a m to d r a f t ratio,

B/d

Speed in k n o t s S p e e d / l e n g t h ratio 400 ft 330 ft 403 ft 330 ft 60 ft 54 ft 28 ft 27 ft 20 f t 18 ft 1 0 , 2 3 2 t o n s 6 8 0 0 t o n s 0.745 0.742 0.985 0.984 0.756 0.754 6.66 6.11 14.3 12.2 3 . 0 0 3 . 0 0 12 12 0.600 0.660

I n the case of the a l u m i n u m hulls, however, m a n y factors h a d to be t a k e n into t h e b a s i c design considerations. I n the p r e l i m i n a r y consideration of t h e s t r u c t u r a l design, the several factors were t h o r o u g h l y discussed a m o n g t h e n a v a l architects, the m a r i n e r e g u l a t o r y bodies, the s t e a m s h i p com- p a n y a n d A l c o a ' s research a n d d e v e l o p m e n t s t r u c t u r a l a u t h o r i t i e s before submission of p l a n s t o the A m e r i c a n Bureau of S h i p p i n g a n d t h e U. S. C o a s t G u a r d for a p p r o v a l . G e n e r a l arrangements, s t r u c t u r a l drawings, s t r e n g t h calcula- tions a n d m a c h i n e r y a r r a n g e m e n t s were reviewed b y the m a r i n e r e g u l a t o r y bodies in g r e a t detail a f t e r submission, because of the novel c h a r a c t e r of the hull s t r u c t u r e m a t e r i a l . T h e a t t i t u d e of the A m e r i c a n B u r e a u of S h i p p i n g t o w a r d t h e designs is s u m m a r i z e d in t h e discussion b y Brown of the p a p e r b y F o r r e s t [14].

TABLE 3.--FUNDAMENTAL DESIGN COMPARISONS, WEIGHTS. SHIP CONDITION: FULL LOAD

DEPARTURE, LONG TONS (2240 LB) AT ~Carrier " A " ~ ~Carrier "B"-~ Particular

Light ship Fresh water Fuel oil

Crew, effects and

stores 34 Cargo General . . . . Fuel oil . . . . Diesel oil Bauxite ore 8,102 Displacement 10,232

Aluminum Steel Aluminum Steel

hull hull hull hull

ship, ship, ship, ship,

tons tons tons tons

1,920 3,090 1400 2150 55 55 38 38 121 121 29 29 34 26 26 62632 5367 4557 10,232 6800 6800 TABLE 4.--LIGHT SHIP WEIGHTS ALUMINUM HULL

CARRIER " A , " LONG TONS (2240 LB)

Hull A l u m i n u m Steel T o t a l M a c h i n e r y , A l u m i n u m Other m a t e r i a l T o t a l E q u i p m e n t and outfit A l u m i n u m O t h e r m a t e r i a l T o t a l L i g h t ship A l u m i n u m Other m a t e r i a l T o t a l Tons 1110 (97%) 33 28 (10.2%) 246 144 (28.6%) 359 1282 (66.8%) 638

STEEL HULL CARRIER " A "

Hull 2038 M a c h i n e r y 362 E q u i p m e n t and outfit 690 T o t a l 3090 Tons

1143

274 503 1920 TABLE 5. --Hull - - Slup Aluminum ~ S t e e l - ~

$per $per $per $ per

ton lb ton lb

Alum: hull 2 0 2 3 0.913 490 01218 Steel hull . . . 490 0.218

DETAILED BID PRICE ANALYSIS, CARRIERS

"A,"

LONG TONS (2240 LB.) - - M a c h i n e r y ~ ~Equipment and Outfit~ Ship Aluminum Other Aluminum ~ O t h e r - ~ ~ P r i c e - - - ~

materials materials

Sper $ per Sper Sper Sper $ per Sper $ per Sper $ per

ton lb ton lb ton Ib ton lb ton lb

17,950 8.015 3000 1.340 7380" 3.295 2040 0.911 2770 1.237 . . . 3 0 0 0 1.340 . . . 2 0 4 0 0.911 1130 0.504

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554 Main Deck ,A l A L U M I N U M O R E C A R R I E R S Frame Spacing, Ford of 15 .. . . 24" 15 t-o 26 . . . 27" 26 fo 28 . . . 50" 28 i'o I00 . . . 53" 100 t-o 125 .. . . 27" Aft. of 125. ... 24" (:lass (Experimental) q~ A-I I~)

American Bureau of Shipping

10"x 2 / / 6 " x 6"x 5/d'L Spaces (~ 2'-5"= I1'-: 7"x J8 8"[ 19'-9"to C L. 12"x 4"x V2" Fig 142" .J o ~o _1 m- Lengfh Overall . . . 5 5 3 ' - 0 " L e n g f h g !2 . . . 3 5 0 ' - 0" B r e a d t h Mid . . . 5 4 ' - 0" Depth fo Main Deck a f Side Mid . . . 2 7 ' - 0"

Draft, Max. Mid . . . 2 ... 18'- 0"

~j~TA6" PI Coammg i :" . . . 11'-3"Clear . . . _o,

,,

18" Camber ½

co Mare Deck Plafmg "6 Oufboard ofHafches 9Ad' ~ ' Inboard of Hafches 1~2" u Shell Plafmg

Sheer S1.ra ke 48';: 060"for V2 L +o 0 41" S~rra ke Below Sheer 0 55" for V2 L ~Io 041" Side Plahng 055"for V2L% 041"at Ends Botffom Plahng V2" for V2 L fo 0 54" Ford

and 041 "Aft

Keel Plafe 48"xO.66"Midshlpsand For'd 48"x 0.BY' A f t of V2 L

Frames t-hruouf Cargo Space Wing Tanks 9"x 4"x V2" Inv. I..:s Af Web Frames 9"x 4"x 5/8" Inv. L's

Boftom Long'Is 9"x4"xgAe"lnv L's

Deck Long'Is 5"xSVz"x 3/8" Inv L's 0ufb'd of Hatches 4"x 5"x 5A6 '' Inv. L's Inb'd of Hafches Inner Bollam Long'is 8"x4"x V2" Inv. Us Inner Boffom

Tank Top Plafing 7/8" Cent~er Veal- Keel V2"

Sohd Floors at Web Frames 0.41" Web Frames 8'-5" ApoH- N T Long'l Girder 56'x 3/8" ~ . . . 1 l ' - 5 " - . . . , f 7 / 8 "

l

1, j ~ j j

~, ~,~:" i 8"x 4"x V2" Inv. L's • ~;~ _ ~ F °58'' ',

I

l 0 S p a c e s ( ~ 2'-3"=22'-6"- . . . "1 - /

. . . 27'-0" Mid. Half Bread~'h . . . - ~

1

F I G . 7 - - M I D S H I P SECTION, S T B E L H U L L , C A R R I E R " B "

In the official preliminary consideration by the marine regulatory bodies, all possible information regarding the application of aluminum to ship and

other structures was provided. The view was

taken, however, that insufficient information was available from large 61S-T6 structures which might be regarded as being comparable to sea-

going hull structures. There was no comparable

experience and no precedents had been established as a basis for determining the behavior of the

aluminum alloys under the conditions to which they would be subjected in the type of vessel pro- posed. N o question was raised as to the quality of the aluminum alloy products to be used since that was easily substantiated and guaranteed b y Alcoa.

N o question was raised either as to the strength of 61S-T6 for the ship girders. The problem of re- lating the scantlings of an aluminum hull to a steel hull on the basis of ultimate strength or yield

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A L U M I N U M O R E C A R R I E R S 555

FIG. 8--RIVETED ALUMINUM GIRDER HVDROSTATIC TEST PLATES AND SHAPES 61S-T6, RIVETS 53S-T61

strength could be approached simply and with confidence, relying on experience with iron and steel hulls. In considering, however, t h a t all of the a l u m i n u m alloys h a v e a low modulus of elas- ticity, a p p r o x i m a t e l y one-third t h a t of steel, it was recognized t h a t in augmenting the 61S-T6 scantlings, using a comparable factor of safety with t h a t of steel, a resulting relative deflection of a b o u t two to one would occur under the same conditions a t sea.

As a result of the a p p a r e n t impracticability of approaching the problem from the viewpoint of deflection and its effects in riveted hull construction, it was agreed to confine the analysis of scantlings proposed to a strength viewpoint alone, with possibly minor modifications in regard to the superior corrosion resistant quality of a l u m i n u m c o m p a r e d with steel. T h e A. B. S., therefore, in view of the absence of a n y experience w h a t e v e r as a guide with the unknown factors involved, was prepared to class the vessels on an experimental basis only.

Assuming t h a t the effects of the u n k n o w n factors would not prove too serious in test or in service, the a l u m i n u m hull designs were reviewed on the basis of obtaining a strength of structure comparable with t h a t of a steel ship with only a slight allowance for corrosion. In general, the scantlings and a r r a n g e m e n t s proposed were found to be satisfactory, b u t modifications of a few details were recommended. Indeed, a p p r o v a l of all details involving particularly the strength of riveted shell and inner b o t t o m connections was reserved pending completion of box girder tests to prove the calculated efficiencies of the riveted connections.

STRUCTURAL T E S T S

T w o riveted box girders representative of equivalent strength steel and a l u m i n u m ship structures were designed, and a p p r o v e d b y all authorities. These are shown under test in Fig. 8 for the a l u m i n u m girder and in Fig. 9 for the steel girder. T h e y were built and tested b y an east

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FIG. 9--RIVETED STEEL GIRDER HYDROSTATIC TEST. STEEL TO A. B. S. REQUIREMENTS

coast shipyard. Both girders were tested as beams subjected to equal mechanical loadings plus an internal hydrostatic loading produced by a head of 24 ft of water above the b o t t o m of the girder. All seams were caulked outside and all rivet points driven countersunk outside and caulked according to accepted shipyard practice b y experienced riveters. T h e results showed t h a t deflection and leakage of water were about equal in both girders. T h o u g h a more satisfactory test could have been made with the countersunk rivet points and the caulking inside, it was considered t h a t the test was more severe with the water searching from the uneaulked inside. T h e A. B. S. accepted the results as proof t h a t the aluminum riveting and arrangements as proposed b y the naval architects were satisfactory, and the reser- vations imposed were then withdrawn. T h e con- ditional and preliminary approval previously given was then made final for experimental classification and to special survey.

In the course of design, a series of tests were made at Aluminum Research Laboratories to de- termine the buckling stress limitations for the transversely framed aluminum-hulled Carrier " A . " A description of the tests will not be given here since t h a t has already been done b y Forrest

[14].

At one of the shipyards, a number of fabrication and assembly tests were carried out in their ship- sheds using standard steel working equipment. These included : large 61S-T6 and 61S-T4 channel frame joggling and bevelling, cold; frame bending, cold and hot; roll forming, bumping, and braking of 61S-T6 and 61S-T4 thick plates, cold; joggling and flanging of 61S-T6 plates, cold; sawing, shearing, sub-punching, reaming and countersinking of 61S-T6 plates and shapes; riveting, caulking and welding. Fig. 10 shows the cold braking of a 6-ft length of li~-in, thick 61S- T6 keel plate and Fig. 11 shows the result; Fig. 12 shows the results of cold joggling and bevelling

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FIG. 10--COLD BRAKING 61S-T6 KEEL PLATE SECTION

with hot slab bending of a 61S alloy 12-in. channel at 750 ° F; and Fig. 13 shows the cold b u m p i n g of a

3

seetion of 3/~-in. thiek 61S-T4 bilge strake plate after cold rolling to template. T h e tests involved some of the m o s t difficult m e m b e r s to f o r m h o t for a steel hull structure. Some m e m b e r s were impossible to work eold in the 61S-T6 eondition, b u t others were formed cold with surprising ease b y means of good workmanship and clean equipment.

Cost estimates for the final contract negotiation were to some extent based on these tests, b u t the knowledge gained was difficult to translate without a wider b o d y of experience with a l u m i n u m eon- struetion. M o s t of the y a r d supervisory staff and workers who carried out the tests had little pre- vious knowledge of a l u m i n u m and no experience in the forming or fabrication of the h e a v y alumi- n u m m e m b e r s involved. T h e i r skills with steel were a b l y a n d cooperatively applied to a l u m i n u m a n d the work produced was of a high order, indi-

eating t h a t good results in a l u m i n u m hull con- struetion are readily a t t a i n a b l e in a first class y a r d without additional equipment, except p e r h a p s for reheat t r e a t m e n t furnaces for transverse frames when h e a t - t r e a t a b l e alloys are used.

FUNDAMENTAL DESIGN" COMPARISON"S

F r o m a technical viewpoint the project was a v e r y thorough and fascinating study. Of interest to the shipowner, it promised to provide the ulti- m a t e in weight saving and increased deadweight c a p a c i t y for economic m e r c h a n t ship purposes. T h e n o v e l t y of a new ship structure m a t e r i a l at- t r a c t e d and inspired the n a v a l architects more t h a n usual in approaching a new design. N a v a l authorities were concerned as it suggested possibilities for reduction of hull weights with re- sultant increases in speed, a r m a m e n t and armor. Shipbuilders vied for the privilege of building the ship, because of the know-how and prestige which would come to t h e m f r o m its construction.

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FIG. [ I - - R E S U L T OF COLD BRAKING 0 I S - T 6 KEEL PLATE SECTION

T h e basic design characteristics resulting f r o m the study, as compiled in T a b l e s 2 and 3, are suf- ficiently d e m o n s t r a t i v e in themselves as to re- quire no explanation or comment.

As indicated in T a b l e 4, the aluminum-hulled Carrier " A " had 9 7 % of the hull weight of 1143 tons in aluminum. I t s hull weight was 58%, and its light ship weight 62%, of the weight of the steel-hulled ship, while the cargo carrying c a p a c i t y was increased 17%. In the aluminum-hulled Carrier " B , " the light weight was 65% of the weight of the steel-hulled ship, the calculated increased cargo carrying c a p a c i t y being 16%.

C o m p a r i n g Carriers " A " a n d " B , " it will be noted t h a t the several coefficients are v e r y nearly equal except as influenced b y length. There was also a close similarity in the proportionate esti- m a t e d weights and in the gain in deadweight c a p a c i t y for the aluminum-hulled ships.

Therefore the conclusion m u s t be reached f r o m the studies t h a t , for the specific t y p e and speed of ship involved, a gain in carrying c a p a c i t y of a b o u t one-sixth was obtained b y the use of a l u m i n u m hull construction. On the basis of 48 voyages per year, and neglecting tidal conditions, the aluminum-hulled Carrier " A " would h a v e carried 390.000 tons of bauxite per year and the steel-

hulled Carrier " A " 335,000 tons, a gain for the a l u m i n u m ship of 55,000 tons per year, or the equivalent of eight voyages of the steel-hulled ship. With 48 voyages per year, the a l u m i n u m - hulled Carrier " B " would h a v e carried 255,000 tons and the steel-hulled Carrier " B " 220,000 tons, a gain for the a l u m i n u m ship of a b o u t 8 voyages per year.

ECONOMIC ANALYSIS

T h e project developed the general conclusion t h a t building of the ship was entirely practical, b u t the bids showed t h a t a t the time of the proposal it could not be considered economical. T h e bids s u b m i t t e d b y the shipyards showed t h a t the high bids ranged in price for all four t y p e s up to a b o u t 2 5 % higher t h a n the low bids. On an adjusted price basis, it was shown t h a t t h e a l u m i n u m - hulled carriers were estimated to cost slightly over 50% more t h a n the steel-hulled carriers. Basing the cost on the deadweight carrying capacity, on an adjusted price in dollars per deadweight ton, the a l u m i n u m carriers were shown to cost slightly over 3 0 % more t h a n the steel carriers.

Brief analyses of the low bids for Carriers " A " are given in T a b l e 5. T h e figures are presented in prices per long ton and also per pound. T h e y are

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FIG. 12--TWELVE-INCH CHANNEL FRAMES COLD JOGGLED AND BEVELLED, 61S-T6 FRAME AT RIGHT BENT AT 750 ° F

also broken down into the three usual general classifications of hull, machinery, and equipment and outfit, along with the complete ship figures.

I t will be noted f r o m the table t h a t for the steel- hulled ships the hull price per ton was $490, and, averaging the e q u i p m e n t and outfit price, a figure of $2040 per ton resulted. I t is unusual to figure costs per ton of ship machinery, b u t this is done in the table for the purposes of this analysis. I n considering the aluminum-hulled ship estimates, these units were used for the classifications to which t h e y applied in assessing the unit costs for steel and other materials. B y following this method, the cost estimates for a l u m i n u m in each classification were b r o u g h t out and this a p p e a r s fair enough for the practical purpose of arriving a t reasonably accurate a l u m i n u m hull structure unit estimates, a t least.

Upon examination of the aluminum-hulled ship estimates, the cost of a l u m i n u m structure is shown to be $2023 per ton. T h e preliminary cost investigations during 1945 assumed $400 per ton for steel structural cost and $1000 per ton for the aluminum construction which did not seem out of

line at t h a t time. E q u i p m e n t and outfit costs for the steel ship were assumed a t a b o u t $270 per ton while for the a l u m i n u m ship $900 per ton was assumed, allowing a b o u t 2 0 % of the weight in aluminum. F o r machinery, only items such as floors, ladders and gratings were originally considered to effect slight savings in weight and slight increase in cost.

F r o m 1945 to 1948, the price of steel and shipbuilding costs increased to an extent reflected in the bids submitted. T h e price of steel, according to The Iron Age finished steel composite weighted average, increased a b o u t 50%. During the same period, however, the base price of the a l u m i n u m products remained constant. A t the time the bids from which the analyses in T a b l e 5 were prepared, prices of ship structural steel products had advanced a b o u t one-third above the naval architects preliminary estimates.

After consultation b y this author with a l u m i n u m structural authorities on the cost of other a l u m i n u m structures, a conclusion was reached t h a t $0.75 per pound of installed aluminum-hulled structure would h a v e been adequate.

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FIG. 13- -COLD BUMPING SECTION OF (ilS-T4 BILGE STRAKE PLATE, FOI.LOWING COLD ROLLING

This is equal to $1680 per long ton. I t was assumed t h a t in tile riveted aluminum ship construction, 65% of tile material would be plate, 30c~o would be shapes and 5~o would be rivets. A t the then base prices of these aluminum products, the material cost would have been about $675 per ton.

The difference between the bid figure of $2023 per ton and the figure of $1680 per ton mentioned above equals $34.3. This difference, in our estimation, included not only a factor of safety to cover the risk involved b u t a factor of ignorance due to the lack of experience in large aluminum-hulled construction. In all fairness, there can be no com- plaint on this reality, considering the size of ship and the unknown factors a t t e n d a n t to building with the new structural material.

SOME CONCLUSIONS

Because an aluminum-hulled ore carrier was not built, the drawing of conclusions from the designs

must be confined principally to the technical interest and their value for future considerations. The essential problems were all met in subjecting the project to naval architects of highest reputa- tion in design, to the marine regulatory agencies for their opinions and approval and to capable builders for their practical consideration and estimates.

Though the aluminum-hulled Carrier " A " bids were found to be unacceptable, the final firm bid being approximately 35~o higher than for the steel ship, it was reported t h a t the aluminum-hulled ship could have hauled bauxite at almost the same cost as the cheaper steel vessel--the differential was only 2 cents per ton. The higher carrying capacity of the aluminum ship made the difference close.

F r o m the points of view of hull girder deflection and buckling of deck plating in the sagging condition, satisfactory agreements were reached from the

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A L U M I N U M O R E C A R R I E R S 561 structural tests made. Later tests conducted b y

Muckle [16] and summarized in a recent report [34] provide additional considerations. Recent papers by Corlett [26] and Schade [33] also are w o r t h y of study in connection with the stiffness of ship structures. The introduction and development of inert-gas shielded welding for aluminum vessels since the aluminum-hulled ore carriers were designed, offers another approach for the solution of deflection problems particularly in the framing systems of bulk carriers.

The development and introduction of the tech- nique of cold driving 61S-T31 as quenched and frozen rivets since 1948, providing higher shear strength more easily, reliably and cheaply than in the h o t driving of 53S-T61 rivets, would have assisted the aluminum-hulled carrier design. The number of rivets required and production costs would have been reduced. The inert-gas shielded welding equipment and techniques for aluminum alloys also developed since 1948 would have provided additional assistance and economy for construction. With a new Alcoa non-heat-treatable aluminum alloy available, (to be described later) particularly suited for welded ship construction, the chances would have been even better for reduc- ing costs and building one of the aluminum ore carriers.

AVAILABILITY OF lk,~ATERIALS

The situation t h a t developed because of World W a r I I in the production and distribution of the major metals is now recurring. The aluminum and steel productive capacities of the United States are being rapidly expanded for defense purposes, with aluminum at a rate greater than for steel.

In 1927 the United States production of primary aluminum was about 82,000 short tons and in 1939 it was about 164,000 short tons. In the peak year of World W a r II, the primary aluminum out- p u t reached 920,000 short tons, part of which was uneconomic war emergency production. The U. S. economic production of primary aluminum in 1953 is expected to be 1,400,000 short tons, an increase of 16 times in 25 years, or about double t h a t of 1950 when the U. S. production was about 719,000 short tons [31] [32].

In 1927 the United States marine applications of aluminum utilized annually about 125 short tons, none of it structural, b u t b y 1939 up to a b o u t 5000 short tons were being used annually, mostly for U. S. warship construction. In 1950 about 6000 short tons were supplied, mostly for U. S. merchant ship structural installations. This trend in marine structural applications appears to be increasing.

In one of the Society publications [18] it is shown t h a t the economic availability of materials for shipbuilding more than any other factor brings about their extensive use. I t is impossible, because of existing world conditions and inflation- ary pressures, to predict prices for 1953. But the possibilities in the increasing production of aluminum, along with its light weight, renew its attractiveness for ship construction.

CrROWTH OF ALUMINUM USES FOR -¥[ERCHANT SHIP CONSTRUCTION

T h a t topside applications of aluminum can aid in improving stability, trim, compass performance, safety and in some cases carrying capacity is indicated by the numerous American and foreign installations made in the past 5 or 6 years. Men- tion was made in the historical considerations of the initial t o p s i d e structural installations made aboard merchant ships. The. three New York City ferries mentioned were each equipped in 1937 with 30 tons of deckhouse and pilot house structures using Alcoa 52S and 53S alloys, though a n American coastal collier; the S.S. Glen White, was equipped in 1934 with an aluminum bulkhead forward using Alcoa 52S and 53S alloys to correct a condition of trim. In 1939 the first ocean-going cargo ship to be equipped with aluminum deckhouses, the M.S. Fernplant, was built in Denmark for Norwegian registry using 12 tons of an aluminum-magnesium alloy similar to Alcoa 52S. Earlier, in 1935, the lk~.S. Britagne was equipped in Norway with a pilot house of the same alloy with Norske Veritas approval. In 1939 an aluminum alloy conveyor boom was installed on the Great Lakes self-unloading ore vessel S.S.

Conneaut. The steel boom formerly used was 150 ft long, b u t b y using Alcoa 27S alloy for the outer 190 ft of a new boom its length was increased to 218 ft. I t was possible to stock pile 9400 c u f t of ore per front foot with the new boom for an increase of 57% in storage capacity.

The ocean-going United States ships fitted with aluminum deckhouses are all passenger ship con- versions, have World W a r I I built hulls and use Alcoa 61S alloy with 53S rivets. The installations were made during the period when the aluminum bauxite carriers were under consideration. These vessels, three Delta liners and three Alcoa combination ships in South American service and two A. P. L. liners in trans-Pacific service, were each equipped with 12, 30 and 125 tons of topside structures, respectively--for the latter two ships to correct an adverse stability condition. T h e tVIatson liner S.S. Lurline was re- converted after World W a r I I with 61S alloy plated deckhouses. Early in 1951 three new New

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562 A L U M I N U M O R E C A R R I E R S York City ferries went into service, each being

equipped with 90 tons of Alcoa 61S alloy deckhouses using cold-driven 61S alloy "frozen" rivets.

In 1943, the British began an organized investi- gation into the possibilities of a l u m i n u m alloys for ship construction and, t h r o u g h the activities of their A l u m i n u m D e v e l o p m e n t Association, worked out an extensive p r o g r a m of theoretical investiga- tion and research. Later, in 1946, with the or- ganization of the British Shipbuilding Research Association and in cooperation with the British Admiralty, interlocking Light Alloys C o m m i t t e e s helped in continuation of the effort. References to the numerous papers produced as a result are given in the References a t the end of this p a p e r be- ginning with [9]. France, the Scandinavian a n d the Low Countries [28] h a v e also conducted investigations with the result t h a t m a n y European countries are now installing a l u m i n u m topside structures aboard m e r c h a n t ships of several types, principally passenger ships, fishing vessels and oil tankers.

T h e r e are now well over 200 m e r c h a n t ships of the principal m a r i t i m e countries building or in service with substantial a l u m i n u m applications in topside structures. These include over 30 passenger and combination ships--American, Canadian, French, Belgian, Dutch, Danish and Swedish b u i l t - - f o r their own, Chinese and Portuguese registry; a b o u t 100 fishing vessels, m o s t l y trawl- ers, f o r British, Norwegian, Icelandic and Cana- dian owners; a b o u t 50 British tankers, b u t less t h a n a dozen d r y cargo ships. A b o u t two dozen aluminum-hulled barges up to a b o u t 100 ft long have also been built in Britain, principally of knockdown construction for overseas shipment and re-assembly in the tropics for river services.

T h e principal foreign a l u m i n u m construction under w a y a t present includes two large trans- Atlantic passenger ships building in France with a b o u t 150 tons of topside structures each and two passenger ships building in Belgium with a b o u t 100 tons of structures each for Portuguese registry and operation in trans-Atlantic service to Brazil. These vessels are building to Bureau Veritas latest rules for riveted a l u m i n u m ship construction.

Of the Canadian m e r c h a n t vessels equipped with structural a l u m i n u m installations, two have been in successful operation between the lower G r e a t L a k e s and the Gulf of St. Lawrence since 1947. These vessels, the S.S.

Redfern

and

Redriver,

were then each converted with poop,

bridge and smokestack structures, using an alloy similar to 61S. Use of a l u m i n u m for these and other installations has enabled t h e m profitably to carry additional cargo through the St. Lawrenc6

River lateral canals at the original full load draft. Incidentally, their structural installations are maintained unpainted to effect additional economy.

In the case of the U. S. Lines superliner S.S.

United States,

the a l u m i n u m applications are sub-

s t a n t i a l - o v e r 2000 long t o n s - - w i t h more t h a n half of it in topside structures. Such installations permit reduction of beam, d r a f t and displacement f u n d a m e n t a l l y to affect l e n g t h / b e a m and speed/ length ratios, with a cumulative weight saving several times t h a t of the a l u m i n u m to reduce power . a n d fuel requirements. T h e y produce the highest economy and ship efficiency in a passenger liner in all respects, including high carrying capacity. Reference is m a d e to the researches of H o l t [19], Muckle [12], [21] and Cor- lett [27], and their tests and analyses for full theoretical superstructure consideration; to Vasta [25] for full scale tests and analyses; and to Lewis [20] and Muckle [34] for economic considerations. F r o m these and future researches, with the p a t t e r n set b y the superliner, large passenger ships of the future are certain to utilize a l u m i n u m extensively for superstructures.

This p a p e r is primarily concerned with aluminum-hulled ships, b u t the case of going the limit with a l u m i n u m superstructures to gain specific ad- v a n t a g e s in performance is cited to point out t h a t in proceeding to the u l t i m a t e of a l u m i n u m hulls similar or greater economies m a y be gained. T h e extra first cost of a l u m i n u m m a y be offset b y reduced power and lower priced machinery, with less fuel consumption in a smaller ship with the same deadweight c a p a c i t y as a larger one built of steel, and the initial i n v e s t m e n t then might be less [30]. As an alternative, speed m a y be increased with the same power in the .smaller and lighter hull and it m i g h t then be a b o u t equal in price to the larger steel hull, with equivalent deadweight capacity.

A good example of a ship in which these ad- v a n t a g e s m a y be gained, using the experience obtained from the bauxite carrier designs, is the iron ore carrier reported under consideration to c a r r y L a b r a d o r ore from Seven Islands to the G r e a t Lakes. T h e limitations, unless the St. Lawrence Seaway is built, are the river and the canal channels and locks between M o n t r e a l and L a k e Ontario. T h e canal lock dimensions are 270 ft long, 44 ft wide and 14 ft deep a t low w a t e r on the sills, with a low water limiting depth of 14 ft in the river channel above Montreal. T h e ship's length, beam, d r a f t and displacement are fixed. Speed, and therefore power, would be limited for the canal passage, b u t not necessarily for the Lakes, River and Gulf reaches. Assuming such a vessel