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MODEL TEST RESULTS AND PREDICTED EHP FOR AN 86-FOOT PERSONNEL BOAT, FROM TESTS OF MODEL 4675 by Eugene P. Clement and Charles W. Tate, Sr. December 1958 Report 1288 NS715-086
NOTATION A AW AX I B CB CG r Area of a vertical transverse underwater section Area of waterplane at the load waterline Area of maximum vertical transverse underwater section Baseline Breadth at the maximum-area section, measured at the LWL Block coefficient (volume of the underwater body,v, divided by the volume of a rectangular parallelepiped, LWL B HX) Center of gravity Centerline Cp rprismatic coefficient (volume of the underwater body,v, CW divided by the volume of the prism, LWL AX) Waterplane coefficient (ratio of area, AW., to area cf rectangle, LWL BX) C Maximum section coefficient (area, AX, divided by the area of rectangle, B 1 x 0) ehp FnV Effective horsepower Froude number based on volume, in any consistent units, g H R LCG LOA LWL P R V v w A V x Acceleration due to gravity Draft of underwater hull, measured from IL to LWL Draft at the section of maximum area Longitudinal center of gravity location Length overall Load waterline or length on load waterline Effective power, ft-jb/sec Total resistance, lb Speed, knots Speed Density of water, weight per u:at volume Displacement at rest, weight of Displacement at rest, volume of Linear ratio, ship to model 71 Trim angle of hull with respect to the at-rest position ii
ABSTRACT Smooth-water model tests were made of an 86-ft personnel boat de r,-red for "all-weatherp operation. The model was tested for ehp at full-scale displacements of 130,000 lb, l40,000 ib, and 150,000 lb. In addition, at one speed and displacement, the lines of flow were determined by the acid-trace method, in order to find the appropriate location for the bilge keels. I"L ODUCT Ivi4 The Bureau of Ships, by Reference '.* requested ehp tests of a new design for an 86-ft, "all-weather," personnel boat. MODEL AN1D TEST PROGRAM A 1/16-scale model, 4675, was built to the lines of Reference 2. The lines are shown in Figure 1. The tes's were made in the high-speed basin, using Carriage 3. The model was towec in the shaft centerline, which is shown in Figure 1. Tests were maide et full-scale displacements of 130,000 ib, 140,000 1b, and 150,000 lb. Initial trim was zero deg in each case. The speed range tested was up to 18 knots, full scale. Resistance, trim angle, and bow rise were measured. Because of the relatively small size of the model (5 ft in length), it was considered that artificial stimulation of turbulence might be required. Accordingly, the model was towed both with and without a trip wire. The trip wire was 0.042 in. in diameter and was attached to the model surface 3 in. aft of the bow. The 3-in. dimension was measured along the surface of the model, parallel to the waterline planes. However, it was lound that at low speeds the trip wire did not consistently have the exrected effect of prolucing higher and more consistent values of rpsistunce. Furthermor-., at the hign speeds, the trip wire caused the water to separate from the side of the model for a short distance aft of the wire. For these speeds, the model had consistently lower resistance wit.i, the trip wire than without--presumably because of the reduced, wetted, rea. For the above reasons, only the data obtained without a trip dire are presented in this report. TEST RESULTS The mowel data obtained are presented in Figure 2. The air drag of the touin2 rear has been subtracted from the measured resistance data. Values if i',ll-scale ehp are presented in Figure 3. The ehp was calculated by tl.*. method described in Reference 3, using the 1947 ATrC friction coefficiente with zero roughness allowance. Values of wetted surface and wetted length for the differe't displacements tested, are tabulated. *Referenct.s wre listed on page 2.
Full-Scale Model Model LWL Model Wetted Displacement Displacement Length Surface lb lb ft ft 2 3.30,000 ;().86 5.02 5.138 140,ooo 33.24 5.03 5.330 150,000 35.61 5.03 5.505 An acid-trace test was also run to determine the appropriate location for the bilge keels. This test was run, in accordance with Reference 1, at a full-scale displacement of 140,000 lb, and at a speed corresyonding to 160 ehp, full scale (12.1 knots, full scale). Figure 4 shows the appropriate location for the bilge keels, as indicated by the acid-trace test. REFERENCES 1. Bureau of Ships ltr S82/27(452) Ser 452-30 of 51 May 1957 to David Taylor Model Basin. 2. Bureau of Ships Sketch No. 027170, 86-Foot, All-Weather Boat, Lines and Offsets. 3. Gertler, M., -The Prediction of Effective Horsepower of Ships by Methods in Use at the David Taylor Model Basin,* David Taylor Model Basin Report 576 (Dec 1947). 2
FIot DESIGN Wi DAVID W TAYLO NO VZNE APPM~AOSS: KZZL SHIP AND NODSL DATA FOR BUSHIPS 86-FT PIRSONNIL BOAT M0IJLL 4670 IN rfit SHIP MODEL LdL COSFFIC1:QNT LiNGT14 (LdL) 80.50 5.031 tco* volume of Kos L-,NT (IU) 86.0i2 5.37 1 jicuded In cal -an,19.25 1.203 c. a-a U in TO0,5000 33.24 [ -20 LI.WT AiA 100 3.910 PT-1 LCG/LvIL *0.482 FROM STUiN A - 16 ~tnr~a ALK.IT- *~T~? TRIM. v AGs;NCY: BU.1HIPS, LIN66 P~LAN: 027170 AIAI STATIONS aa
IGURE 1 DATA SHEET.OR MODEL BASIN NEB.t4 1908 0F I I0-40 :ee1 nol 0.12 -. - 20-~ calculation-- --. 0.1 _- -. 0o 0.1ic I A "{.0 Calculated from test at 33.2:-lb - lipl.. Zero Initial trim. nuals- I,.6C tant iand power corrected to 100 u00lbuing 1947 A.T.T.C. Ship Model- Correlation - Line - with zero / I I 0.5 1 1.0 a roghes allwace IF, liet * L* -4-- St" a noe J I!1 i JI 9 ',// -sew. of - W 6 - _ei 3
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INITIAL DISThIUTION Copies 12 CHBUSEIPS, LMbrea7 (Code 312) 5 Tech Librax 1 Tech Asst t-o Chief (Code 106) 2 Preliminary Design (Code 420) 1 Bull Design (Code 440) 3 Boats and Small Craft (Code 449) 7
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