280 NICHOLLS'S SEAMANSHIP MXT) NAUTICAL KNOWLEDGE

(3) With centre D and radius 2 tons descnbe an aro cutting JSP
at F.

Join DF and produce DF to A so that DA=6 feet Draw CM
perpendicular to DG and produce it to B, so that CB=CA AB \^
the distance between the shackles, viz , 7-9 feet

Fig 22.

Calculation. —

In to tangle DEF. Given DF=2 tons, DE=*l-5 tons,

A
scc 6=^=^=1*333 .-.6=11° 25'

/n trian/jte ZX4C. D^=6 ft., ^ 6=41° 25'. Z.C=90°. Find AG

AC=AD sin 0=6 sin 41° 25'=6x '662 =3-972.

-4^=2 ^0=2x3-972=7 -944 ft.

Distance between shackles A and 5=7 -94-1 ft.

.--A square cargo tray 4'x4', slung by four corner legs
each leg 7 feet long and meeting in a ring at the top, supports a
weight of 20 cwt. Find the tension on each leg of the sling.
C0ns*rod«w..-Make a preliminary sketch to illustrate the question as
in fig. 25. Assuming the load to be evenly distributed on the tray so
that its centre of gravity acts downwards at 0, the middle of the tray,
then each leg of the sling will do the same amount of work. Consider
one pair of diagonal legs, DA and DBt to be doing aJI the work and