1815.] Col. Beaufoy on the Construction of Sails. 185 



Article III. 



On the Construction of Sails. By Col. Beaufoy F R S 



(With a Plate.) 



(To Dr. Thomson.) 



^ MY DEAR SIR, BushelJ Hta ^ July ^ ^ 



Should you think the accompanying paper on the Construc- 

 tion of bans worthy a place m the Annals of Philosophy, you 

 will much oblige me by its insertion. • / 



I remain, my dear Sir, 



Very sincerely yours, 



Mark Beaufoy. 



The generality of vessels being impelled by wind, it is a most 

 important circumstance in naval mechanics that sails be so made 

 as to produce the greatest effect ; for should they be improperly 

 constructed, the sh.p-builder will, to little purpose, have exerted 

 his skill in giving the hull of the vessel the most advantageous 

 form for dividing the water. The time most important that 

 sails should be scientifically made is when beating to windward 

 especially off a lee shore, as the safety of the vessel and caro-o,' 

 and, what is of much more consequence, the lives of the crew 

 may entirely depend on their action. ' 



It is not my intention to write a treatise on sail making, or to 

 describe their variety of shapes; I shall, therefore, confine my 

 emarks to those sails technically termed fore and aft sails, and 

 the form in which I conceive they ought to be made to enable 

 them to expose a flat surface to the wind, and which I have prac- 

 tised with success.. . l 



vJ!hi S ?i ilS ^i°u e - made ' the first aeration is to cut cloth 

 by cloth, the width being regulated by the length of the yard 

 boom, gaff or stay, and the depth by the height of the mast ; the 

 most simple mode of forming the sail is by sewing the selvages 

 of the canvass together, and making the seams rectilineal as 



SET 6 ? in PL XC , VI ' fig - 4 5 but aS Sa,ls When large/and con- 

 structed of canvass alone, are not sufficiently strong to resist the 



impulse of a powerful wind, the edges are usually surrounded 

 with cordage, called bolt-ropes, to diminish the strain and 

 prevent renting. When sewing on the bolt-rope, it is neces- 

 sary to gather up at the head and fore leech about one-seventh 



hLdVfT^'. I ^ Ch meanS in hoistin S and ^reading the 

 ZLtl / i 8a I ' C , St l eSS 1S tr ? nsferred «™ the canvass to the 

 cordage ;* but a sail thus made will not, when set exnose a 

 plane surface to the wind ; for, besides being concave, soCe of 



whVr. ? tk I * fter - l T h Wi " have the <*«* of back sails, 



ri?: 65 , 6 VeSSe £ P r0 S ressiv * velocity, and material^ 

 augments the leeway. To remedy this two-fold disadvantage, 



«*£ toZSf f ,Cr " leC<1 '' , ,", rC S,,OU, ' , be " ,e sarae ,p "Sth of bolt-rope a, 

 •ranv.,,*, „, other wctd», w pari ol the canvas* should be gathered in. 



