1831.1 
. Flat-bottomed River Boats . 
325 
VII. — Flat-bottomed River Boats. 
In your Analysis of Mr. Prinsep’s work on Steam Navigation, in the 29th 
number of The Gleanings, there is a note, page 157, stating that, “ the plan of 
Captain Forbes’ steam tug does not accord with the specification in Appendix A. 3, 
which refers to a boat with a double truss ; but the principle is the same in both.” 
If in the term “ both ” you allude to the plan submitted by me to the Marine 
Board, (a drawing of which on a reduced scale, is in the next page to that of 
Captain Forbes’ ;) I must beg leave to submit a few remarks, with a view of 
shewing there is not such similarity between the two plans as many people sup- 
pose, and as your note above alluded to implies, nor do I think it can be fairly said 
that the same principle has been followed, (although that term will probably admit 
of great latitude ;) they are both shallow flat-bottomed boats, but the one is 
secured by a system of trussing, and tying, connected from one extreme of 
the vessel to the other, and imbedded, as it were, in the frame work of the vessel ; 
while in the other, the connection of the trussing and tying is broken in the 
centre, by a simple frame work in the shape of a parallelogram, in which the 
principle of both truss and tie is lost sight of, with regard to the relative position of 
the weight it is intended to support ; for although the same, or nearly the same 
arrangement of materials is adopted in a flat-topped roof, v’here the upper hori- 
zontal beam is the truss beam, and the lower the tie, yet the weights to be sup- 
ported are so very differently situated that a comparison between them will not 
hold ; for viewed as a roof, the whole weight will be found to rest upon the 
he beam / and it is only through the medium of the queen posts, that it is 
brought to bear upon the rafters, (the diagonal timbers at each extreme of 
the frame work, fig. 1,) and again, the queen posts are not acted on by any 
direct strain, the principal weight being placed at a distance from either, so as to 
Cxe rt its pressure in a transverse direction on the floors and sleepers, and through 
these to the queen posts and trusses. Figs. 1 and 2 are the plan and elevation 
the boat designed by Captain Forbes ; Fig. 3 is an elevation of that designed 
b. v me : the latter shews one side of the boat, in, which the trusses and ties are 
^bedded as before mentioned, the trusses running inside the timbers, and the 
tbs made of flat iron, and shewn by the dotted lines, outside, both being firmly 
bolted together ; and the spaces between the timbers, being filled up with diagonal 
cheeks, following the course of the ties. Fig. 1 shews the framing in the middle of the 
being unconnected with the side. It is laid down as a principle in constructing 
fr'Une work, intended to resist great pressure, that all “ openings between the 
timbers should be triangles, and that all quadrilaterals should be avoided if 
possible*” a principle I have strictly attended to in the design, which exhibits six 
Wangled triangles firmly connected. In Captain Forbes’ design there are two 
^tangled triangles, with two quadrilaterals interposed ; which interposition 
Plainly appears to me a subversion of the principle of trussing. If the floor timbers, 
Und slee pers are of sufficient scantling to support the weight, and resist the stress 
the en gine, then it follows that this frame work which stands at the wig it 
of Kfeet from the surface of the water (at 2 feet draught), might well be dispensec 
since (to quote Captain Forbes’ words) they are but so many air or . 
opposing parts j” if these be not strong enough, then I should say, that a piece 
Iml)er the size of the truss beam from B to D, laid in the bottom o e 
and bolted to the sleepers, would be more effective than placed as it now is j for 
*** t ^ le timber in question to be 10 inches square and the sleeper tie sa , 
am) 1 t ned thus> the y be equal to one piece of 20 inches deep y 
ieel sure it needs no argument to shew which of the two is ca c a c 
