NO. 2 HYDROMECHANIC EXPERIMENTS RICHARDSON 9 



the difficulty of construction involved, particularly if the surface run- 

 ning qualities are to be retained, we see that the present forms are 

 reasonably satisfactory. While the possible saving of 3.5 # head 

 resistance is worth considering, it must only be considered if its 

 attainment does not involve increased weight, cost or difficulty of 

 construction to such a degree as to outweigh the small gain possible. 

 Such savings increase in importance in proportion to the square of 

 the speed desired. It thus appears that increased efficiency must be 

 aimed at in those members of the structure which offend to a greater 

 degree than the hull, namely, the multiplicity of the truss members; 

 and the exposed power plant, especially the water cooled power 

 plant. 



The peculiar form of Model 1617-1 is due to an attempt to utilize 

 the advantage of the flying boat arrangement of bottom and step, 

 together with a good shape stream line hood in place of the ordinary 

 pontoon with the hydro-aeroplane type of machine. 



It is interesting to note that the coefficient of fineness of this 

 model is less than that for Model 1602-2 which indicates that per unit 

 of area of maximum section the resistance of this form is slightly 

 less than that of the 1602 model. An inspection of line 29 will show 

 that the probable reason for this is due to the very low value of the 

 frictional component of the resistance of this model. However, when 

 the comparison is based on /cpir^*, the form factor used by Lord Ray- 

 leigh, this form is much coarser than the 1602 model. 



An independent experiment is worthy of note at this time. An 

 experiment was made to determine the existence and amount of 

 "nosing" torque on model 1350, at various angles of incidence. 

 Unfortunately the apparatus carried away before the experiments 

 were completed, but it was found that there is a " nosing " torque 

 of about 90 ft. lbs. when the deck of ^he pontoon is parallel with the 

 line of flight. To this torque should be added that due to the head 

 resistance which is approximately 5.42 lbs. X5 ft. = 26.10 ft. lbs. or 

 a total torque due to the pontoon tending to make the machine head 

 down of about 116 ft. lbs. This with the c. p. of the diving rudder 

 15 ft. abaft the c. g. would require the diving rudder to carry a 

 negative load of about 7.75 lbs. if the machine were " balanced " for 

 all other eft'ects, at 60 m. p. h. 



Additional experiments on submerged models are contemplated 

 with a view^ to determining the stream line flow about the models as 

 a means of arriving at improvement of form, and other experiments 

 to determine the effects of the cockpit openings, sponsons, etc., and 

 a more complete series for determining torque at different angles. 



