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December, 1923 MARINE REVIEW 463 RESERVE BUOYANCY Reserve Buoyancy in Excess of the > ee Requirement of the Board of Trade German Winter (1909) —~ Requirement of ‘The Board of Trade 35.8% (Winter) Proposed Drafts for the Lakes te co Draft FIG. 11—RESERVE BUOYANCY OF LAKE VESSELS AT DRAFTS PROPOSED IN TENTATIVE FREEBOARD TABLE ing the latter part of November, it amounts to 1% inch per foot of draft as compared with the winter freeboard increase of only %4 inch per foot of draft which is proposed in the British report. In Fig. 11 are also plotted the drafts which would result if the present German freeboard regulations (Vorschriftender See- Berufsgenossenschaft) were followed. These drafts are computed from. tables in “Hilfsbuch fur Schiffbau.” The dia- grams indicate that on the lake freighters, the reserve buoyancy is much in excess of the requirements of both the British board of trade and the German regula- _ tions. These vessels have then, clearly, an ample margin of reserve buoyancy at the proposed drafts. It is, however, well to remember that the provision of a large amount of reserve buoyancy is not sufh- cient in itself to ensure the safety of a vessel in the flooded condition. Only in conjunction with an efficient subdivision is it possible to take full advantage of the reserve buoyancy. This phase of the problem will be treated more in de- tail in a later chapter. Height of Working Platform Experience gained in the actual opera- tion of different types of vessels has early focused attention on this element in fixing a proper freeboard. This ques- tion has also been the subject for some interesting investigations. In a paper read at a meeting of Die Schiffbautechnische Gesellschaft in 1901, Herr Rudolf Rosenstiel describes some complete investigations of the behavior ot ships among waves; and he dis- cusses the influence of waves in determin- ing the needed height of deck platform.* for larger vessels will permit, in gen- He points out that this consideration eral, a less freeboard than has been con- sidered necessary from the viewpoint of on , ‘ bee J oo aoeitmicecune der TifladeLinicn reerve buoyancy. He. also. shows that Yahrbuch der Schiffbautechnischen Gesell- when a vessel is supported by waves schafit. 1901. shorter than the length of the vessel, the WAVE PROFILES Scale ve pa!t.t030.4.50 6070 009000 Feet Vessel 420° X52 x 28’ =| Vessel = a >| S = FIG. 12—CHARACTERISTIC LAKE WAVE PROFILES