| 摘要 |
Otter board which is provided with a means for adjusting net-mouth expanding force which can be driven by liftingrope thereby to freely vary said force. According to the first embodiment of the invention, said otter board is formed by biplane construction of board planemembers, and said means for adjusting the net-mouth expanding force comprises the outermost board plane member of said biplane construction that is variable in its angle of attck about a pivot provided in the biplane construction. According to the second embodiment of the invention, said means for adjusting the net-mouth expanding force comprises a through bore in a single otter board construction, said through holehaving a variable opening area by means of an oscillating member.
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