US1755709A - Stern construction for motor boats and the like - Google Patents

Description

April 22, 1930. J. c. SMALL 1,755,709

STERN CONSTRUCTION FOR MOTOR BOATS AND THE LIKE Filed Bee 10, 1929 n .Duzezzior eioualiimztifimall 6' Byway 35 culties of getting available bait,

Patented Apr. 22, 1930 iIISEJGQ JONATHAN coox SMALL, or raovrNcnrowN, MASSACHUSETTS STERN coNsrImoTIoNrort Moron Bears AND THE LIKE I Applicationfiled December 10,1929. Serial No. 413,020.

This invention relates to improvements in marine propulsionland particularly to the increasingof the speed of motor driven boats which have heretofore-been retarded by inv adequate relations between hull design at the stern and the propeller power. There have been many andradical develop v 'ments in motor boat design particularly along the type of the so-called speed boat, but in the morefsturdytypes of craft the lighter I powered motors have'not been productive of increases in speed suchas seemed reasonably tripe expected by the horse power made avail- To illustrate the'princlples of invention, I call attentlon to a'type of craft in general use and well illustrating" the problem. These boats maybe readily distinguished from the'speedboat type in that they are of generally deeper draft and generally of the squarer stern type.

.These are usually, but not necessarily of the duty type of motor boat in which certain oomlnessis required; and sea worthiness an absolute prerequisite.

Such boats'represent the substantial interestsofdeepwaterbusiness such as that of mostimportant. I q I I 7 of. illustration I cite the usual proper coast boatadapted for offshore work as for example the very practical conditions under which the fisherman must operate. The modern market for the catch, the difiiof any and all season supply impose conditions which call for sea worthy, capable craft, but of speed heretofore unknown." 'e The requirements for sucha boat are most exacting and'theyare'difiicult to design. So

far, the practical ideal boat for such work has not been produced. I therefore base my disclosure on my own experience in redee signing or readapti-ng standard types' to a uniform improvement in performance; 7 l .Imay take as an -illustrative problem that of the squarestern, rather deep draft. keel I speed seemed to be of no avail. V

'1 type of the coastfisherman. Such boatshave 'u'sually been provided with; powerful engines but even with ample engine power the fisherman. For such; sea worthiness is by original building,

the demands 7 less of reserve engine power.

soon reach a limit beyond which they cannot I I 'bedriven though-below that of theoretical engine capacity. i The problem Was to provide-for increased speed without sacrificing the desired feature 5.5 of design. v 1

The operation of such a square stern boat is greatlyaifected by the suction at the stern, caused by the passage of the boat through the water, resulting in a dragging'of a volume of 69 water of great weight. It .has been observed that this suction increases so as to reach its maximum when the boat is moving-at '12 knots an hour and when it is so great that with the ordinary equipment of a fishing vessel, 5 it is practically impossible to exceed a speed I of 12 knots. The drag increases very rapid- .ly as the speed is increased from ten miles to reason of the fact that the water not being solid tends to slip away from the propeller I blades ;this slipping of the water is,.of course,

greatest toward the surface of the water .as the surface of the waterindicates the way of least resistance. 1 l

My invention contemplates by addition or the presence of stern factors which prevent the stern settling under the submersion tendency of the propeller and the back drag on the stern inselfalso the slippage of the propeller thrust.

. In general, Iprovide on'each side of the stern'what, as shown, is a box like compartment structure in the nature .of a counter sponson and at a slight angle to the race of V the propeller.

The difliculties seemed to .ee that these 9 boats at certain speeds peculiar to their 'design developed a sterndrag that so rapidly diminished the otherwise possible. acceleration as to make a practical speed limitregardand under such conditions, the propeller red sistance diminished so that added propeller Whilejmy invention is capable of embodiment in original structures my immediate In addition practical problem was that of discovering the deficiencies of craft already built and in "shown the same boat otherwise unchanged did twenty-two and one-half knots. .The practical difference in the service use er this boat made one days work out of what had been one and one-half or two days In such practice and by applying the principles of my invention on the basis of removable auxiliary stern lifting members or sponson like character, it is possible by test to make adjustment to make up for the stern sag differential between the stern design and the propeller power.

on so adjusted and fitted these members operate as follows In starting the stern usually settles somewhat slightly submerging the auxiliary chambers. Thesettling is however, soon overcome and as the boat picks up speed the stern rises to normal water line. This relieves the stern of any back drag and the wake runs clean. Furthermore, the downward pitch of the box bottoms takes-slightly of the propeller race thrust Which not only keeps the ster'n'sustained, but steadies the propeller race.

In practice my invention may find many embodiments.

general solution for an immediate demand.

The drawings therefore show an average type square stern motor boat of whatmight be called a general utility type. It is to be understood asof suitable power engine equipment.

In the. drawings:

Fig. 1 is a side view of a stern equipped in accordance with my invention. I

Fig- 2 a stern view thereof, and

Fig. 3 a bottom view. 7 V

Considering the problem of such a boat as is indicated there is the general hull portionl framed on ;and having a stern 3 and counter 9.

general keel member 2 ,The details of design are not involved in "the application of principle.

As shown, the stern has an overhang and the propeller 4 is on a shaft 5 which has a slight downward pitch.

To make simple thedisclosure I show but one and that acase of I such ordinary occurrence that it involves the With such a design I equip with a pair of lateral box cells sponson members. These consist of longitudinal side members 6 and 7 fitted at their upperedges to conform to the contour of the counter and straddling the rudder post.

These sidem'embers 6 and 7 'are fitte'd with a bottom 8 the forward edge "of which is fitted to the hull at its line of contact.

The rear of each chamberis closed by an 'end piece 9.

Wherethe stern design is such as to permit this to overlapthe stern it may be made to constitute a supporting member.

The ends 9 are scuppered as to accommodate any leakage.

The bottom members 8 are given a slight downward pitch so as to receive the race of the propeller 4. This. steadies the thrust of at 10 in order the propeller and imparts to the stern a' slight upward resultant.

Furthermore, when such a boat as above suggested isfpropelled at a speed exceeding about twelve miles an hour each compartment'relieves itself of all water that may be in it; thus creating a greater buoyancy under the stern of the boat.

When this condition or situation has been brought about the bottom of the compartment is still below the level of the water which isalongside the boat, being keptf-rom rushing in from the sides by the projecting sides of the compartment. It is also kept from coming in at the open end of the structure by the depression injthe wake caused by the drag ofthe stern. The effect of this in greatly increasing the speed of the boat seems to result in further reducing the slippage, by reason ot the decrease of friction due to the reduction of the displacement" and the resulting lightening of the load on the engine. 7

What I therefore claim and desire to secure by Letters Patent is:

1. In combination with the stern of a -mo- *tor driven boat, of a pair of stern sponson boxes disposed one on eachside of the rudder post and having a flat'bottom pitched slightly downwardlyand rearwardlyand disposed above th'efpropeller race. 2. In combination with the stern of a motor driven boat, of a pair of stern sponson boxes disposed one on each side ottherudder post and havinga fiat bottom pitched 'sli-ghtly downwardly and rearw'ardly and diSPOSQdQ- above the propeller race, and of displacementsubsta'ntially equal to the stern submersion tendency of the boat at maximum propeller speeds.

i 3. Incombination with the stern of a mo:

tor boat, pair of attached flat bottomed sponson's disposed one on each side of the rudder post and having their bottom fat substantially normal water line and slightly the propeller race.

downwardlyand re'arwardly inclined into the sides and bottom one on each side of the rudder post, the box 4. In combination with the stern of a motor driven boat, a pair of stern chambers disposed one on each side of the rudder post and having a flat bottom pitched slightly downwardly and rearwardly and disposed above the propeller race and of displacement substantially equal to the stern submersion tendency of the boat at maximum propeller speeds.

5. In combination with the stern of a motor boat, a pair of flat bottom counter boxes disposed one on each and having their bottoms at substantially normal water line and scuppered at their rear ends. I

6. In combination with the stern of a-motor driven boat, a' pair of boxes each consisting of sides bottom and end members, fitted to the counter,

ends overlapping the stern and supported thereby. v

7. In combination'with the stern of a motor boat a pair of auxiliary chamber members disposed one under each counter an havlng a combined dlsplacement substantially counteractive of the submersion tendency of thepropeller at maximum speed.

In testimony whereof I aflix my signature.

JONATHAN COOK SMALL.

side of the rudder post

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