This paper numerically investigates the influence of separation variation of the outriggers on the hydrodynamic performance of a high speed trimaran(HST)aiming at improving its applicability in diverse realistic disciplines.The present investigation was performed within the framework of the 2-D slender body method(SBM)by calculating the resistance of three symmetric trimaran series moving in a calm free surface of deep water.Each trimaran series comprises of 4681 configurations generated by considering 151 staggers (-50％≤α≤+ 100％),and 31 separations(100％≤β≤400％)for 81 Froude numbers(0.20≤Fn≤1.0).In developingthe three trimaran series,Wigley(C)-st,AMECRC(C)-09,and NPL(C)-4a models were used separately for both the main and side hulls of each individual series models.A computer macro named Tri-PL(C)was created using the Visual Basic for Applications(C).Tri-PL(C)sequentially interfaced Maxsurf(C)then Hullspeed(C)to generate the models of the three trimaran series together with their detailed hydrostatic particulars,followed by their resistance components.The numerical results were partially validated against the available published numerical calculations and experimental results,to benchmark the Tri-PL(C)macro and hence to rely on the analysis outcomes.A graph template was created within the framework of SigmaPlot(C)to visualize the significant results of the Tri-PL(C)properly.