10 AERODYNAMICAL EXPERIMENTS UPON A YACHT'S MAINSAIL. 



APPENDIX B. 



The method followed in working up the results from the original observations 

 was briefly as follows : 



The observed scale pan weights (d, C2, Di and D2) were plotted on angles as 

 abscissae and the curve faired. (The maximum deviation of any point was about 

 13^ per cent.) From these faired curves, the differences Ci — C^ and Di — D2 

 were computed and also faired. The values of c and d were computed, using the 

 values of Ci — C2 and Di — D2 given by the above curves. The values of x and 

 y were computed directly from m, c and d, and are plotted on Plate 6. The values 

 of 2 were computed from the faired values of the scale pan weights {Ci, C2, Di 

 and D2) plotted, and Table I gives the results from the curves. 



Simple algebraic transformations give the following equations which were the 

 ones directly used for the solution of x, y, d, c and z : — 



M 



d tan + c 

 <^ = 5-625 (C-Q 



flr=5.625(A-A) 



Z =- 



Q-Q 



DISCUSSION. 



The President; — Gentlemen, you have heard the very interesting paper read by Pro- 

 fessor Everett, entitled "Aerodynamical Experiments upon a Yacht's Mainsail." The meet- 

 ing would like to hear any discussion. Some of you, I hope, are prepared to discuss the paper. 



Mr. William Gardner, Member: — I have read over Professor Everett's paper with 

 interest, and I think he is to be congratulated upon being the first one to make a scientific 

 investigation of the principles of sail propulsion. The question of the shape of sails and 

 their form — and by the form I mean the flatness or fullness of the section of the sail— has 

 been a matter of discussion since the early forties. When the America went abroad to race 

 the English boats had full baggy sails, while the America had much flatter sails, but not abso- 

 lutely flat, and a good many attributed the success of the America as much to her sails as to 

 her hull. 



