!ser. 1130 



PRELIMINARY DESIGN OF A MOTORROAT 853 



/Trace of Desioned Waterline 



In Second Layout 

 Enqme Should 



Be Moved 

 Forward and 

 Passengers Aft 

 to Provide 

 More Comfort 

 for Them 



Weather 

 Protection 

 Over Corqo 

 and Boqt^Qqe 

 '*- not Shown 

 Here 



Desiqned" Woterlineot rest 



96765|43ZIF|P Stations 

 Fig. 77. Q Sketch op Tentative Space Layout for Round-Bottom Tender for ABC Ship 



mentioned in Sees. 77.13 and 77.14 for installa- 

 tion in the 24-kt planing tender, with a maximum 

 brake power of 225 horses, may be sufficient for 

 the round-bottom tender. At least, it will be used 

 for a first weight estimate. 



77.29 First Weight Estimate for the 18-Knot 

 Hull. A first weight estimate is made by using 

 a few known weights plus reasonable percentages 

 (from Fig. 77. D) of the estimated gross weight 

 of 18,000 lb. These are, in lb: 



18-kthull 14-kthuU 



(1) Pay load, including crew 1,000 3,000 



(2) Diesel engine, one HN-10 or the 



equivalent, including water 



and oil in the engine 2,650 2,650 



(3) Fuel for 6 hr at full power, reck- 



oned as 0.5 lb per brake horse 338 (half 675 



Pb = 



Total 13,582 lb 16,099 lb 



In round figures these become 13,600 and 

 16,100 lb, or 6.071 and 7.187 t, respectively. 



77.30 First Power Estimate for the 18-Knot 

 and 14-Knot Conditions. The first power esti- 



mates for the round-bottom tender are made by 

 five separate direct methods, some of which are 

 the same as those employed in Sec. 77.14 for the 

 full-planing tender. 



I. Employing first the K. C. Barnaby formula of 

 Eq. (77.i) with if, = 2.80 from Table 77.d for 

 a 35-ft round-bottom boat, the brake power 

 estimates for the two speed conditions are: 



(a) For the 18-kt boat 



F^ ^ (18)^(6.071 ) 

 K? (2.80)' 



(b) For the 14-kt boat 



_ 7!E_ (14)^(7.187) 

 ^^ ~ K\ ~ (2.80)' 



II. Using the PhilUps-Birt Eq. (77.iiia), with 

 K^ = 2.80 from Table 77.e for a 35-ft round- 

 bottom boat, the brake-power estimates for the 

 two speed conditions are exactly the same as 

 for the K. C. Barnaby formula in I. preceding. 



III. Using the Crouch-Werback Eq. (77.iia) of 

 Sec. 77.14 for the 18-kt boat only, as it is not 

 vahd for T, < 2.5, and taking C as 64.7 from 

 Fig. 77. F, 



„ W (lb) V (kt) 



= 251 horses 



= 180 horses. 



cWl^l (ft) 



13,600(18)' ^ 

 (64.7)' V35 



178 horses. 



