Propeller Design Detail Stage To this point we have developed the K T vs J2 J4 design approach Most references present the series data in alternative format One version is curves of constant efficiency and 1 J on a scale of P D vs B P1 or P D vs Kq1 4 J 5 4 These are due to D W Taylor plotting the series data using B P which we will define later The best description of use of the forms of the charts I found was in PNA page 159 Propulsion and Propellers Section 10 Propeller Design by Karl Schoenherr The following is excerpted from the text The procedure in using these charts depends on the nature of the problem to be solved that is on which data are known and which are unknown In general propeller design problems belong to one of the following categories 1 Preliminary Design a Given The designed speed of the ship the corresponding ehp and the propeller diameter Required The propeller pitch and the rpm for best efficiency b Given The designed speed of the ship the corresponding ehp and the engine rpm Required The propeller pitch and the propeller diameter for best efficiency 2 Final Design Given The ehp curve as a function of the ship speed the propeller diameter and the power output of the engine at the designed rpm Required The propeller pitch the efficiency and the ship speed obtainable under the given conditions 3 Analysis Given The propeller dimensions the ship speed power thrust and rpm Required The true slip wake fraction and thrust deduction The KT vs J2 J4 design approach we have done to date is directed at 1 Preliminary Design At this stage the power required is determined based on a reasonable first estimate of propeller efficiency determined with this approach The propulsion plant is then sized accordingly The propulsion plant may have discrete incremental sizes and thus may not exactly match the first estimate exactly The ship design proceeds perhaps a new resistance close to preliminary design etc is obtained and then Final Design takes place At this point PD power delivered to the propeller is known It may not match exactly the preliminary estimate hence the V s may be different Taylor selected two parameters for plotting information for design work BPn N P1 2 VA5 2 where N rpm P power delivered hp Q 2 N and VA speed of advance kts n number of blades and BUn N P1 2 VA5 2 where N rpm U useful power hp T V A and VA speed of advance kts n number of blades These are not non dimensional but Taylor thought that was ok since propellers work in water of practically constant density which will be taken care of by the constants used S P page 100 This motivated NSMB to present the data on plots of P D vs K Q 1 4 J 5 4 B P 1 2 constant which can be shown to be equivalent as follows 1 5 4 4 KQ J 9 13 2006 see B series units US mcd 1 0 17279 BP 1 2 P in hp n in RPM VA in kts similarly not developed here 1 1 3 4 4 KQ J 1 1 75 BP 2 2 P in hpUK D in ft VA in kts 1 5 1 4 Q VA 2 5 n D n D 4 4 KQ J 5 1 PD Q 2 n 4 lbf ft PD hp 550 2 hp s 2 min rpm 2 5 2 sec ft sec 60 2 lbf 4 VA kt 1 688 sec kt min ft in lbf 4 ft BP 2 5 VA 1 5 1 4 4 KQ J 1 2 rpm V kt 5 A PD hp 4 1 1 removing units 1 99 4 P n2 D 550 2 5 sec V 5 2 2 lbf A 1 688 60 4 ft 4 1 4 1 1 1 4 2 4 BP another approach which accommodates other units for P D VA and n is shown in 4 0 1728 5 2 2 1 688 60 550 2 1 2 PD n 5 V 2 A B series units conversion xmcd regression coeff Re 2 10 6 details these are fixed form of plot shown in PNA P D vs Kq1 4 J 5 4 Curves are constant and 1 J These are derived from the same data as our previous K T KQ curves EAR 0 40 z 4 1 4 1 2 P D 1 0 8 0 6 0 4 0 0 2 0 4 0 6 0 8 Kq 1 4 J 5 4 9 13 2006 2 1 4 0 5 2 n 1 2 n PD PD Q sec 1 2 1 4 another form of the same information conversion of Kq1 4 J 2 5 to BP note constant efficiencies absi j bp1 i j 0 17279 abscissa is log scale 2 158 871 1 60 1 6889 139 697 J 124 652 nn 112 533 102 562 EAR 0 4 z 4 0 5 0 55 0 6 0 65 0 7 higher to right 0 7 1 2 0 65 1 P D 0 6 103 0 55 0 8 112 0 5 125 0 6 140 159 0 4 1 10 100 BP1 an example of use of these curves say we have a design such that n P D BP1 VA PD 16000hp 100 min VA 16knot 0 5 2 5 BP1 12 353 0 5 hp BP ans BP1 2 5 min knot 9 13 2006 n 3 v line 0 5 0 6 1 5 we will plot that vertical line on the curves and determine the maximum efficiency P D and 0 7 1 2 0 65 P D 1 103 0 8 112 125 0 6 0 55 0 6 140 0 5 159 0 4 1 10 100 BP1 it appears that for the max is 0 140 0 0 67 P over D0 0 98 approximately n D VA ft D min knot 0 VA n let s say the diameter is limited to 20 ft by another constraint n D1 ft min knot D 22 4 ft D1 20ft VA 1 ft min knot 1 125 then the best situation is 1 0 65 P over D1 1 25 approximately N B The shape of the developed curves is generally OK I m not completely confident in the exact values The validation is not as close as I would like 9 13 2006 4