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104 that Prof. Hovgaard mentions I think emphasizes this fact very strongly-- se that really the structure of the bulkhead is perhaps of: more import- ance than the number of bulkheads. In passenger vessels, of course, we can design them to float with any two or three compartments flooded, but it is practically useless to do so, if the bulkheads are going to give way when under load. I think that is the keynote of Prof. Hovgaard's paper. : With regard to the general treat- ment of bulkheads, I fully agree with Prof. Hovedard that. it..is. a useless thing to put stiffness on both sides. There is no particular point in it, it may be a little simpler, but I think in general we can get all the stiffness we want by putting the stiffeners on one side of the bulkhead, and so get- ting the benefit of the bulkhead plate itself. I am sorry I have not had time to look over the mathematical treatment of the subject in detail, but from a casual glance at it I think as far as I can see the method is original. I do not remember ever having seen quite the same treatment before, and Prof. Hovgaard is to be congratulated on this elemental way of treating the subject. The Steamboat Inspection Service. _ There is, however, one other point to which I would like to draw atten- tion. This morning the question as to whether this Society could appoint a committee to consider the question of the merchant marine was discussed. As far as I am aware, this Society is Mot tepresented in any of the dis- cussions in connection with the steam- boat inspection service. As far as I am aware, we have not any standing committee that is called in when questions of a technical nature are being discussed by the Steamboat In- Spection Setvice. I think it is a mis- take. This Society should represent the 'best available technical knowl- edge in the country, and it seems to me absurd that this Society should not 'be represented when technical questions are being discussed in con- nection with steamboat work. I have had that brought home to me, and I suppose all of you have had, in con- nection with some of the require- ments, and particularly the require- ments for bulkheads. If you will look at the rules, you will find that the Steamboat Inspection Service will not allow you to put a stiffener on a bulk- head less than 3.5 x 3.5 in. That is their rule. Now, suppose you have a somewhat lightly constructed river THE Marine REVIEW steamer, with bulkhead plates 4 in. thick, probably using about a erin. rivet, I think you will all agree with me that a little 5é-in. rivet on a 3.5 flange looks somewhat foolish, to say the least, but we have to put in this 3.5-in, flange to take a 9-in. rivet. Also this other flange is specific, and in some cases there is no doubt that 3 in. might be enough, and in other cases 3.5 in. is not nearly enough. The whole question is left in one case in a rather foolish state, and open to adjustment between the in- spector and the builder. I just draw attention to that fact, because, as I say, this comes up in connection with this paper, and I think this is a mat- ter in which this Society should take some interest, not only in connection with bulkheads, perhaps, but with other matters pertaining to shipbuild- ing generally. Difficulties of the Ship Builder. Mr. Main: I would like to remark that this is certainly a valuable paper, but when a naval architect or ship- builder is called upon by an owner to get at the cost of a new. ship, which he sometimes has to do-in a period of about 24 hours, and if the vessel is not to be classed by any of the registration societies--and in these days of keen competition it is natural that the shipbuilder will en--- deavor to design the vessel as light as is consistent with the requirements which the vessel has. to fulfill--and of course you can see if he has no data before him it would be quite a problem to take some of these form- 'ulae and work them out. This paper is very valuable, and I would like to see it supplemented by scantlings for bulkheads, and plating, and stiffeners for various depths of hold. I think that would be a fine thing to append to such a_ paper as this, so any one taking it up could lise it, readily, and could -find the minimum weight of bulkheads to do the required work. Admiral Bowles used to tell us you can always tell when a ship is too light, 'but you can never tell when she is too strong. There is no com- plaint if she is too strong, but when she is too light, you notice it. Prof. Sadler's remarks are very ap- propriate, regarding the rules of the Steamboat Inspection Service. These rules, as you know, about a. year ago called for bulkhead stiffeners to be spaced not more than 24 in. apart, but salt water seems to have de- creased in weight or pressure, and If the increasing we are now allowed 30 in. registration societies are March, 1919 the weight of stiffeners, our laws are decreasing them by spacing them wider. I have not followed the . paper closely enough to give you any Dos- itive angle at which the horizontal stiffener should be bent, but in one case, with a small bulkhead, the bulk. head bent out 2 in. when the tank was filled. But the bulkhead did not leak. The bulkhead was strong enough to hold the water, but you could harq. ly send the vessel out in that condi. tion. That bulkhead was effectively stiffened up by gutting a horizontal channel one-third of the distance from the 'base. There is a case whete a horizontal stiffener was more useful, and of lighter weight, than: increasing all the other stiffeners. Strains Upon the Bulkhead. Chairman Stevens: The chair would respectfully suggest the consideration of the strains upon the bulkhead by the blow, even when it does not strike the bulkhead directly. It is probably impossible to formulate mathematical- ly a very satisfactory statement of such stresses, but it would appear that a little practical experience as to the effect with ships that have been struck, not on the bulkhead, but in the neigh- borhood of the bulkhead, showing how the structure of the bulkhead had stood the effect of the shock, absorb- ing the energy of the blow, would be of interest. I trust that some .of the members who.have had practical ex- perience along that line will give us the benefit of any data they may have on the subject. If there is no further discussion, Prof. Hovgaard will close. Prof. Hovgaard's Reply. Prof. Hovgaard: I quite agree with what Prof. Sadler said, that the main point of this bulkhead question is that we should make the bulkhead strong enough--practically irrespective of the question of how many bulkheads there are, we can at least require in the passenger vessel that the bulkheads, when they are called upon to carry the pressure of water, that they should be strong and possess the same margin of strength as does the outer shell of the ship. That seems enough, not to have been the case in the steamship Republic, and I mention that case because it is one we all know about, although we do not yet positively know how it was she went down, but we know that had the bulkheads of that ship been absolutely strong and snug she would have float- ed, because she floated for the greater part of a day, and had the bulkheads