Full scale experiment was carried out in the southern sea of Korea to compare some important factors tested in the model experiment. The results obtained can be summarized as follows ; 1. The changing aspect of mouth performance of the full scale net was almost coincided with the results obtained by the model experiment. The vertical opening(H) and the opening area(S) can be expressed as a function of the towing velocity(V) as H=48.78. e0.38V(unit: m, k't) S= 1,443 .e-0.25V(unit: m2V, k't) 2. The changing aspect of working depth of the full scale net was almost coincided with the results obtained by the model experiment. The depth(D) can be expressed as a function of the towing velocity(V) and the warp length(L) as D=92.49.V1.37(unit: m, k't, L= 150m) D= 12.07+0.32. L (unit: m, V=2k't) [)= - 7.90+0.22 . L (unit: m, V=3k't) 3. Some problems were found to operate A - type full scale net by common bottom pair trawlers. The problems can be summarized as follows; (1) Entangling of wing and square head ropes while net casting.(2) Man power needed and time spent for net hauling by common bottom trawlers increased considerably.( 3) Tearing of nettings caused by over -load of tension and entangling of net pendant while net hauling. To solve these problems, the trawlers are favorable to be equipped with variable pitch propeller and llet drum. While the net is favorable to be constructed with trifurcated net pendant in stead of quadrifurcated net pendant used at present.

Towing tension of the model nets were determined by the load cell(O~20kg, 20DBBP) in front of W〈lrp with the combinations of towing velocity, warp length and the distance between paired boats. Towing tension of the full scale net was determined by the load cell( 0 ~ 6ton) in front of warp with the towing velocity. The results obtained can be summarized as follows; 1. The changing aspect of towing tensions of the model nets A and B varied by the same tendency in the range of O.356-2.019kg and O.352~2.117kg, respectively, depend on the operational factors. Among the factors, the towing velocity was the most influential. The tensions(T) can be expressed as a function of the towing velocity(V) as TmA = 1.57 . V1.86 (unit: kg, mlsec) TmB= 1.58 . V1.90 2. The towing tension of the full scale net was almost coincided with the results obtained by the model experiment. The towing tension(T) can be expressed as a function of the towing veJocity(V) as T=479V1.75(unit: kg, k't)

Working depth of the model net was determined by using of the same experimental tank and the same model net that used in the forwarded report in a series studies. The depth of the net which indicates the depth of the head rope from the water surface, was determined by the photographs taken in front of the net mouth with the combination of towing velocity, warp length and distance between paired boats. The results obtained can be summarized as follows: 1. Working depth of model nets A and B was varied in the range of 0.09~1.66〈TEA〉m,and 0.04~1.34〈TEA〉〈/TEX〉m〈/TEX〉(which can be converted into 2.7~40.2〈TEA〉mand 1.2~49.8〈TEA〉〈/TEX〉m〈/TEX〉in the full-scale net) respectively, and the depth of model net A was slightly deeper than the depth of the model net B. 2. Working depth (〈TEA〉D,which is appendixed m for the model net, f for the full-scale net, A and B for the types of the model nets) can be expressed as the function of towing velocity〈TEA〉〈/TEX〉Vt〈/TEX〉, as in the model net(〈TEA〉Vt=〈TEA〉〈/TEX〉m〈/TEX〉/〈TEA〉sec) 〈TEA〉〈/TEX〉DmA〈/TEX〉=(-1.99+0.65〈TEA〉Lw) 〈TEA〉〈/TEX〉e-1.72Vt〈/TEX〉 〈TEA〉DmA]=(-1.91+1.04 〈TEA〉Lw) 〈TEA〉〈/TEX〉e2.88Vt〈/TEX〉 in the full-scale net(〈TEA〉Vt=〈TEA〉〈/TEX〉k〈/TEX〉'〈TEA〉〈/TEX〉t〈/TEX〉 〈TEA〉DfA=(-29.32+0.65〈TEA〉〈/TEX〉Lw〈/TEX〉)〈TEA〉e0.40 Vt 〈TEA〉〈/TEX〉DfB〈/TEX〉=(-57.60+1.04〈TEA〉Lw)〈TEA〉〈/TEX〉e-0.67 Vt〈/TEX〉 3. Working depth 9〈TEA〉D appendixes are as same as the former) can be expressed as the function of warp length〈TEA〉〈/TEX〉Lw〈/TEX〉) in the model net, and can be converted into full-scale net as in the model net (〈TEA〉Vt=〈TEA〉〈/TEX〉m〈/TEX〉/〈TEA〉sec) 〈TEA〉〈/TEX〉DmA〈/TEX〉=-0.99 〈TEA〉e-1.42Vt+0.67〈TEA〉〈/TEX〉e-1359Vt〈/TEX〉〈TEA〉Lw 〈TEA〉〈/TEX〉DmB〈/TEX〉=-.258〈TEA〉e-3.77Vt+1.16〈TEA〉〈/TEX〉e-3.15Vt〈/TEX〉 〈TEA〉Lw, in the full-scale net(〈TEA〉〈/TEX〉Vt〈/TEX〉=k't) 〈TEA〉DfA=-29.28〈TEA〉〈/TEX〉e-0.32Vt〈/TEX〉+0.67〈TEA〉e-0.37Vt〈TEA〉Lw 〈TEA〉〈/TEX〉DfB〈/TEX〉=-69.10〈TEA〉〈/TEX〉e-0.81Vt〈/TEX〉+1.16〈TEA〉e-0.72Vt〈TEA〉〈/TEX〉Lw〈/TEX〉. 4. Working depth was gradually shallowed according to the increase of the distance between paired boats.

A model experiment on the pair midwater trawl net applicable to 800 PS class Korean pair bottom trawlers was carried out in the special-prepared experimental thank. the tank was prepared as a reverse trapezoid shape in its vertical section by digging out flat soil. The dimension of the tank showed the 9.6 W×43.0 L(m) of the upper fringe and the 4.8 W×38.0 L(m) of the bottom with 3.0m in depth. The depth of water was maintained 2.7m during experiment. The model net was prepared based on the Tauti's similarity law of fishing gear in 1/30 scale considering the dimension of the experimental tank. Mouth performance of the model net during towing were determined by the photographs taken in front of the net mouth with the combinations of towing velocity, warp length and distance between paired boats. The results obtained can be summarized as follows: 1. Vertical opening of the model nets A and B was varied in the range of 0.18~0.88 m and 0.21~0.78 m (which can be converted into 5.4~26.4m and 6.3~23.4 m in the full-scale net) respectively, and was varied predominantly by towing speed. Vertical opening (H which is appendixed m for the model net. f for the full-scale net. A and B for the types of the model net) can be expressed as the function of towing velocity〈TEA〉Vtas in the model net 〈TEA〉〈/TEX〉Vt〈/TEX〉 : m/ sec)〈TEA〉HmA=1.67〈TEA〉〈/TEX〉e-1.65Vt〈/TEX〉 〈TEA〉HmB=1.15〈TEA〉〈/TEX〉e-1.13Vt〈/TEX〉, in the full-scale net (〈TEA〉Vt : k't) 〈TEA〉〈/TEX〉HfA〈/TEX〉=50.27〈TEA〉e-0.37Vt 〈TEA〉〈/TEX〉HfB〈/TEX〉=34.46〈TEA〉e-0.26Vt. 2. Horizontal opening of the model nets An and b was varied in the range of 1.03~1.54m and 1.04~1.55 m (which can be converted into 30.9~46.2 m and 31.2~46.5m in the full-scale net) respectively, and was varied predominantly by distance between paired boats. Horizontal opening (W, appendixes are as same as the former) an be expressed as the function of distance between paired boats 〈TEA〉〈/TEX〉Db〈/TEX〉as in the model net 〈TEA〉WmA=0.69+0.09〈TEA〉〈/TEX〉Db〈/TEX〉 〈TEA〉WmB=0.73+0.09〈TEA〉〈/TEX〉Db〈/TEX〉, in the full-scale net 〈TEA〉WfA=20.81+0.09〈TEA〉〈/TEX〉Db〈/TEX〉 〈TEA〉WfB=22.11+0.09〈TEA〉〈/TEX〉Db〈/TEX〉 3. Net opening area of the model net A and B was varied in the range of 0.28~1.04 〈TEA〉m2 and 0.33~0.94〈TEA〉〈/TEX〉m2〈/TEX〉(which can be converted into 252~936〈TEA〉m2 and 297~846〈TEA〉〈/TEX〉m2〈/TEX〉 in the full-scale net) respectively, and was varied predominantly by towing velocity. Net opening area (〈TEA〉S, appendixes are as same as the former) van be expressed as the function of towing velocity〈TEA〉〈/TEX〉Vt〈/TEX〉 as in the model net 〈TEA〉vt : m/sec) 〈TEA〉〈/TEX〉SMa〈/TEX〉=2.01〈TEA〉e-1.54VT 〈TEA〉〈/TEX〉SmA〈/TEX〉=1.40〈TEA〉e-1.65Vt, in the full-scale net (〈TEA〉Vt : k't) 〈TEA〉〈/TEX〉SfA〈/TEX〉=1.807〈TEA〉〈/TEX〉e-0.35Vt〈/TEX〉 〈TEA〉SfA=1.265〈TEA〉〈/TEX〉e-0.24Vt〈/TEX〉. 4. Filtering volume of the model nets A and B was varied in the range of 0.32~0.55 〈TEA〉m3 and 0.37~0.55〈TEA〉〈/TEX〉m3〈/TEX〉(which can be converted into 8.640~14.850 〈TEA〉m3 and 9.990~14.850〈TEA〉〈/TEX〉m3〈/TEX〉in the full~scale net) respectively, and was predominantly varied by towing speed. filteri..