US2969760A - Hull form - Google Patents

Description

Jan. 31, 1961 G, G, EDDY 'I 2,969,760

HULL FORM Filed March 18, 3.957 5 Sheets-Sheet 2 I N V EN TOR. George 6. .E0/afg 96,44@ ,wrom/EY patterns and, anattemptto'ov'ercome the s United States PatentO 2,969,769 HULL FORM :GenrgeGiEddr .Bay .Gift Mish' @sa un einen,

Ynaar Mar..1s,s1ss1,ssr.-Ng. erspart s claims. (ci. 11A-66.5)

t0 which any hull approahss v.dsfl alanine-.is @Renew upon the relationship vbetweeen the of Ithe bloat',- sthe speed, the particular hull -form einplpyed, andl'the hydrodynamic reaction characteristics l of fh? Plagingfsurf'aces of the boat.

'nie arr .of building a semi-planing @r planing 1.11411 term ,for passage through fluids has been lighly'developed.

v Originally. Yit was thoushtthafasmpgth'11u11term uld give fastest and most friction-'xfree contact withiafluid .when r.passing therethrough, therefore', 'inostfdesiigners looked to various hull shapes to provide the'rnjost eticient hull form. `However, when the most efclient hull torni had been developed, the coelcient of friction deyeloped by the hull passing through the iuid was kfound toibe suits high-@dansers were Freeda' 15 ,rsde'tbis saette cient of friction. The dvelopmentofthe Alapiz nstrtl- Spaces between ,theY `hull and the ter .Spacis tended to brk la thetowsf 11.1,:asain thereby substantially'affectingthe boundary 'layer owing against fluid. U.S. Patents 2,039,585 and 2,039,586 described-,the use' of ,lapped constructionfwherein the laps were angled recognizing the existence of pressure anime.

latentv2,42`3,860 vthen developed theai't one by Vproviding a lapped construction wherein the at angles recognizing presure patternsf; Y vhad a number ofsharp jogs in an attempt to break up the"`pressure patterns and v reduce thecoeftlcientof friction. None of these designs however, hayebeen `cxo'rnpletely successful in" givingrnehighstpassible speed withfh lowest horsepower and highest weight ratio.

It is, therefore, a principal object of the present invention to provide a hull construction which recognizes the importance of water pressure patterns as a factor in decreasing the efficiency of a planing hull. Another object of the present invention is to provide a planing hull form having a multiplicity of steps thereon, each step being at substantially right angles to the pressure patterns developed by the hull planing through a fluid. Still another object of the present invention is to provide a multiplicity of surfaces on a hull form whereby a myriad of air bubbles are introduced between the hull can be determined by trial and 'error'e'forlieachparticular @hull under diierent conditions. Asifhas'b'e'e'ii stated,

*substantially* right angles,

and the uidkthereby to cause interruption of the boundary layer between a hull and uid through which it planes. Afu'rthe'r object of the present invention is to provide a planing hull form having a lapped construction and a'multiplicity of steps thereon, each step intersecting the pressurespatterns of the hull planing through a huid at Other objects .will become .apparent hereinafter. These being among the objects of the present invention, l'the invention coincides incertain features of iconstruction and combinations of parts to be'hereinafter. described with reference tothe accompanyi-ngdrawings and then claimed having the above and other objects in view. In theaccompanying drawings which-illustrate suitable embodiments of the presentl inventionl and in 'which like numerals refer to like parts throughout the several different views.

Fig. l is a bottom elevational view of the steps of the present invention as applied to a well known planing hull designed to be operated at an average load condition.

-Eig. 2 is a section of the hull shown in Eig. l, the section being vtaken at lines 2-2 ofFig. 1.

Fig. 3 is a side elevational view of the hull of. Fig. 1. Fig 4 is a perspective view of a single longitudinal extending planing surface of the type used to. build up a hull ofthe present invention. It is' to be understood that other means of building the hull bottom of'theprese'nt invention may be used. -Fig. 5 diagrams typical pressure patterns generated by a smooth surface hullat planing speeds.

Fig.-6 is, aperspective view of hull of. Fig. 1.

-Fig.=7-is.a' perspective sectionfofthe hull of Fig. 1

`andirag. 6.'

Referring now to the specific drawings, itwill be noted lthat aboat hull 10 having a .transom 13' and sides `11 v and A12 tapering to a bow 16 is provided. Oi'thebottom of Ythis hull is a planing bottom made of 'a' lapped construction of longitudinally`extendingplaning surfacesv'lfl extending from the forward portion v'of the'. hull 110 tothe bottom edge of the transom13. 'On the surfaceof each of the lapped longitudinally extending planingsurfa'ces' 14 are a plurality of steps 15. Thesestepsfarerearward and may bev either tapered or rectangular. Each o'f these steps vis at an acute angle from the 'perpendicular to'the keel line v 16. This angle-decreases .from am'xinun hear- Hest the ,front portion of the hull -toafmirii'm'um nearest the transom. Ideally, these steps will. beperpendicular tothe pressurel patterns 17 illustrated'ror Va particular hull form at a specific speed inFig. S

It is to beunderstood that this is a generic drawing for aspecic group of pressure patterns under spcific`conditions. However, generallyr speaking allhulls planing" or ,.Semifplaning through a iiuid willl'gener'atelsirilar patuterrrs, yalthough the fspecic anglesv maybe ydiler'eiit and ideally, ,the steps;1 5 a're,.placed perpendculartd'fthe pressure patterns 17 generated.bya'paticular'ihllhnder specic conditions. But, since these conditions will vary widely depending upon the horsepower and weight placed on a hull, approaching perpendicular is the best that can be achieved.

As shown in Fig. 7, the steps 15 do not have to be deep, just sufficient to break up the boundary layer of water adjacent to a hull passing through a Huid. Preferably, the steps are suiciently deep to cause a breaking up of the boundary layer and a consequent interruption` of the pressure pattern, but n'ot suticently deep to cause an excessive back drag at the step. Thus, by providing a step which is excessively deep, reversal of the normal flow to ll the void caused may be achieved, with the resultant drag adversely affecting the speed of the hull.

While Fig. 2 and Fig. 4 illustrate the preferred method of construction of the hull of the present invention, .e., a lapped construction of a multiplicity of longitudinally extending plam'ng surfaces 14 having steps 15 thereon,-it is to be understood that other methods of achieving the same result may be employed.l For example, laying up a plastic material on a conventional smooth hull in a manner so as to provide a multiplicity of steps having the proper angle to intersect the pressure patterns, or.,by laying up metallic sheet also to form steps at the proper angle are also satisfactory. Other methods of forming the hull bottom of the present invention will be apparent to those skilled in the art. i

While it is preferable to have the steps of the present invention intersect the pressure patterns perpendicularly, it will be understood that since ideal conditions 'are seldom, if ever, obtained, those angles which are perpendicular under most conditions vare usually employed. Determination of the pressure patterns is readily accomplished by observing the exit waves of a particular hull form at a particular speed under a given horsepower and weight factor. The steps are then designed to intersect these pressure patterns at right angles. These angles will vary from. 45 to` 80 near the front of the hull and from 60 to 89 near the rear of the hull, of course,

depending on the particular hull form and the conditions u under which it is operated.

In order that the invention may be better understood,

the following speciiic description is given, but it is-to be understood that the invention is not to be limited thereto. A 16 foot planing boat frame was provided with a transom, a keel and two plywood sides proceeding fromy the transom to a junction at the bow. There was also provided a series of longitudinal planing surfaces having a series of 4-5 rearward steps thereon, each step being at an angle less than perpendicular to the keel line, those near the rear being closer to perpendicular than those near the front. Each step was between 1A; inch and 3i@ inch in depth and extended across substantially the width of the planing surface. A series of seven of these surfaces were placed on each side of the hull frame between the keel and the side, each surface lapping. the other surface and providing a 3%; inch depth of lap.

The resulting boat showed a better speed for unit of horsepower and weight over asimilar hull having -a smooth planing surface, a reduced frictional contactarea,

.a reduced surface tension effect, that is, a reduced frictional resistane resulting from adhesian of surface tension, a smoother ride due to the increased amount of air under the hull, a handling ease, and an increased apparent buoyancy. Additionally, the angle of attack of the hu'lly at the fluidwas inherently decreased due to Iventing and Yrelieving the negative pressure areas, and more speed could be obtained with less powerl While this invention has been particularly described as applying to planing hulls, it is to be understood that 'it' is also applicaple to boats, ships, barges, pontoons, flying boat hulls, etc., that is, any shape which must be moved through a uid with the resulting generation of pressure patterns and a boundary layer.

. .Various modifications may be made in the present invention without departing from the spirit or scope thereof, and it is to be understood that I limit myself only as defined in the appended claims.

I claim:

1. A planing hull comprising: sides, transom, keel line, and at least two fluid-contacting surfaces between said sides, said transom and said hull line, a plurality of steps on said fluid-contacting surface, each of said steps being positioned so as to be substantially perpendicular to the pressure patterns developed by said hull planing through a fluid, and each of said steps being of a length substantially less than the distance between said keel ine and said sides.

2. A planing hull which comprises: a fluid-contacting surface having a multiplicity of steps thereon, each of said steps being substantially perpendicular to the pressure patterns developel by said hull planing through a fluid and each of said steps having a length substantially less than one-half the distance between the edges of said liuidcontacting surface. w

3. A planing hull which comprises: a iluid contacting surface comprising a series of longitudinally extending 'planing surfaces lapped toward the outer edge, each of said surfacesY having a plurality of steps thereon, each step being at an angle less than perpendicular to the keel line and the adjacent steps so located as to form discon- Y tinuous lines from said keel line to said outside edge.

' step being at an angle less than perpendicular to the keel,

said angle of said steps being closer to perpendicular near the rear of said hull than near the front of said hull, said steps being so positioned as to form discontinuous lines between said keel and said sides, each of said steps having a length substantially less than one half the width of said fluid contacting surface at the position of said step. l

5'. A 'planing hull form comprising: sides, transom, keel line andra uid contacting surface consisting of a longitudinally extending lluid contacting surface, said surface having a multiplicity of rearward steps thereon, those forward steps being at an angle from to 80 from the keel line near the front of said surface and from 60 to 89 from the keel line near the rear of said planing sur- `face, said steps being so positioned as `to form discon- Jtinuous lines between said keel and said sides, each of said vsteps having a length substantially less than one half the width of said uid contacting surface at the position Aof said step.

References Cited in the file of this patent f UNITED `STATESr PATENTS '971,029 Fauber sept. 2o, 19,10 1,935,622 Eddy --V.. Nov. 21, 1933 l 2,039,585 Eddy et al. May 5, 1936 Y 2,364,541 Makarot Dec. 5, 1941 FOREIGN PATENTS y Great Britain of 1909

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