AERODYNAMICAL EXPERIMENTS UPON A YACHT'S MAINSAIL. 13 



Mr. Cornelius A. Wood (Communicated) : — Professor Everett showed me his paper 

 last summer regarding the most efficient ways of trimming sails, etc. The experiments which 

 he performed for these results are very ingenious, and I believe this is the first time that defi- 

 nite information has been collected in a strictly able way on this subject. 



For years I have been interested in yachting and have followed it up very closely and in 

 a more or less scientific way. I am convinced that Professor Everett's inductions are not only 

 the result of extremely careful and accurate investigations, but that they are of great theoreti- 

 cal importance in any scientific study of sails, as well as being of considerable interest to the 

 up-to-date racing skipper. 



Mr. C. F. Adams (Communicated) : — I received a copy of Professor Everett's very inter- 

 esting article on sails, and very much regret that it was impossible for me to be in New York 

 to hear the discussion held on it. As we know, sail-trimming is rather a matter of the eye 

 than of mathematics, as a rule, and it is to that extent difficult to say how exactly your results 

 correspond with the usual yachting practice; but I should think no variation is obvious beyond 

 what can easily be accounted for by the absence of a topsail and by the relatively heavy spars 

 which you are compelled to use. 



Mr. Charles H. W. Foster (Communicated) : — I received, in due time, the kind invi- 

 tation to attend a meeting of the Society of Naval Architects and hear Professor Everett's 

 paper discussed. I am very sorry that I shall be unable to be present. I have no doubt 

 there will be much said on that occasion that would interest me extremely. 



I have studied the paper and my first feeling is, how much I would like to sit down and 

 talk with the author about it. He has gone just far enough to make us yearn for more in the 

 way of real knowledge as regards a sail. It is astonishing that so little has been done upon 

 the subject which is really worthy of serious consideration. 



I note that he has determined the location of the true center of pressure, the normal 

 pressure per unit of area, and the proper angle of boom, all for a given sail. Of course, 

 all these facts are for one sail only, and no consideration is given to the fact that the gaff plays 

 just as much a part in the set of a sail as does the boom. In fact, I think those who are 

 most experienced in boat sailing as a practical matter make more of the trim and tension 

 of their peak halyards than they do of the trim of the boom. It is astonishing what the 

 effect of a slight change in the peak halyard will have in the behavior of a boat. Of course, 

 the effect of this change is not only upon those questions which the author has attempted 

 to analyze, but also affects pressure on the rudder, and in that way the speed. 



I do hope Professor Everett will continue his experiments, and to illustrate what is going 

 through my mind in regard to the present experiments I would suggest that he conduct some 

 Hne of experiments on a sail which is fixed, both as to the gaff and boom and held in the same 

 plane. These experiments should then be followed up by changes in the gaff. I mean by 

 allowing it to swing off more and less than he has done in the present experiment. It would 

 be very interesting to see what happened with his centers of pressure and the amount of pres- 

 sure. These experiments also would probably show quite a change in the proper position 

 of the boom, or perhaps, I should say, would change the conclusion which he has noted in his 

 present experiments that the boom should be approximately one-half the angle between the 

 apparent wind and the center line of the ship. 



In regarding this paper, the layman might not realize that the statements in regard to 



