^1> 



of values shown on Figure 35 provided the float remains at least slightly 

 submerged. This conclusion is based on the observation discussed in the 

 foregoing that the float became unstable for C^ = O.58 at a speed-length 

 ratio greater than 8.3. This is probably not a serious shortcoming, however, 

 since most designs will involve greater loadings and the float will conse- 

 quently become submerged. 



The problem of an optimum design remains to be investigated, since 

 the value of Q = 1 .31 does not represent the maximum allowable load that 

 may be imposed on the float. Since the float will develop increased lift 

 with increased submergence, reaching a maximum value at some depth greater 

 than that tested, the optimum value of C^ will be somewhat higher than 1 .31 . 

 On the other hand, if the required performance is dictated by considerations 

 of visibility, the value of 1 .31 may well represent the optimum, especially 

 if the float is to remain afloat when at rest under load. At any rate, for 

 applications in which maximum loading is desired, e.g., small, efficient 

 floats for supporting very deeply submerged loads, further calibration would 

 be necessary. 



CONCLUDING REMARKS 



The analysis of the characteristics of the TMB planing float in the 

 planing regime showed that the relation between total load, total drag, and 

 speed-length ratio can be represented by a single equation. Although the 

 method used in this analysis was checked on data available for several plan- 

 ing boats, it must be remembered that the analysis neglects any dependence 

 on Reynolds number. It would appear doubtful that a unique relationship of 

 the type derived c^n be obtained for large planing surfaces over a wide range 

 of Reynolds numbers in which there is a large variation in frictional drag 

 coefficients. It may be concluded, however, that the method may prove appli- 

 cable to planing boats which are running in the planing regime but are heavi- 

 ly loaded, so that the pressure drag and the wave-making resistance will 

 undoubtedly be much higher than the friotional drag. Here again, however, 

 predictions of full-scale performance from model tests of planing boats 

 analyzed in this way must be accepted with caution since the magnitude of 

 the error involved in the assumptions, though not important for the range of 

 floats likely to be used, cannot ordinarily be tolerated in the design of 

 comparatively large boat hulls. 



The foregoing remarks would also apply to a very large form similar 

 to the TMB displacement float, although there do not appear to be any practi- 

 cal applications in water for such a form. It is clear, furthermore, that 

 the type of analysis used for the displacement float, as well as the planing 



