Mechanlcal Studjes on the Characters of the V-door

Tsann-Jan Lee ； Ko Matuda

《臺灣水產學會刊》 3卷1期 (1974/06) Pp. 58-72

https://doi.org/10.29822/JFST.197406.0006

並列摘要

1．The V-door does nor hare as great lifting force as the up-right otter board, but it has been in use in Taiwan from 1956 to the present time. Has the advantages of robust construction and rarely crossing when shooting. For instance, according to Johnson (1970) there was no crossing when shooting in about 400 experimental operations. Another benefit is the stability. Here we can find that the V-door does not plough too deeply into the muddy bottom under actual operation, but there is a reduced horizontal trawl spread. It is worth while, therefore to examine the possibility of improvement in the mechanical characteristics of the V-door. Mechanical analysis, after some mathematical procedures, we get
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5．Results obtained in the course of experiment and mechanical analysis with the changes of C(subscript D)/C(subscript D0) and C(subscript L)/C(subscript D0) against the heel angle at α=15° for parameter θ are expressed that both C(subscript D) and C(subscript L) decrease rapidly in the corresponding range of θ. There is defect in construction of the semicircular bracket of the V-door used in Taiwan, having the freedom to move up and down resulting in an increase of the heel angle of more than 30° degrees. Thus, the lower plane of the V-door collects mud in actual operation.
Consequently, for increasing the lifting force to obtain a higher efficiency of the V-door, the stability of the bracket should be improved, thereby decreasing the heel angle.