the bulwarks. In Class Ic lifeboats the bulwarks are fixed, but in Class IIB lifeboats they are made to collapse and hinge down on the deck in the manner described for Class IIA

open

lifeboats.

FIG. 127.-Outline of "deck" and well of Class IIв pontoon lifeboat.

FIG. 128.-Section of Class IIc pontoon lifeboat.

Lifeboats of Class Ic do not find much favour with shipowners and shipbuilders, owing to the additional room required for the fixed bulwarks, and as deck space is of such great consideration in a passenger vessel, we usually find that Class I. open lifeboats

are attached to all the davits, and the additional lifeboats required to make up the full complement are of the pontoon or open type possessing collapsible bulwarks. Boats having collapsible bulwarks are thus able to stow under the Class I. open lifeboats attached to davits, as shown in Fig. 129, or may be stowed inboard, one above the other, transporting arrangements being fitted under the boats to bring them rapidly under the davits. Fig. 226 and the frontispiece show how the pontoon lifeboats are stowed inboard and adjacent to the davits.

The outstanding difference between pontoon lifeboats and the open lifeboats of Class IIA is to be seen in the method of providing the reserve of buoyancy.

Class IIA lifeboats are fitted with buoyancy air-cases, while pontoon lifeboats of Classes Ic, IIB and IIc depend entirely upon the watertightness of their hull for buoyancy. Therefore it is very essential that the workmanship and materials used in the construction of the pontoon lifeboats should be of the very best quality.

In the first place, the timber used must be thoroughly seasoned, and when completed and in service on board a vessel, they should be periodically and very carefully inspected. Every compartment must be easily accessible and ventilated at every convenient opportunity.

If there were the slightest trace of dry rot in the hull of the boat when first completed, it would very rapidly spread under the conditions of a close atmosphere after the compartments had been closed in by the watertight deck.

Reference has already been made when discussing the details of construction of ordinary pulling boats of the importance of having all shavings cleared out of the boat before and after painting. The necessity for this precaution is even greater in the case of pontoon lifeboats, owing to the special features of their construction. Shavings very quickly become infected with dry rot mycelium, and carry the disease to other parts of the

structure.

The watertight deck is open to the effects of the weather, and in the case of wooden boats the latter has a direct influence on the value of the deck to keep out water, and for this and the other reasons mentioned, it is essential to periodically inspect the interior of these boats.

The difference between the Class IIB and Class IIc pontoon lifeboats is found in the design of the deck, the former has a

well" deck and the latter has a flush deck. The skeleton

Q

decked lifeboat, stowed under a Class IA open lifeboat.

frames of these two boats are practically alike, and they do not greatly differ from the Class IIA lifeboats in this respect, except that the transverse bulkheads in the pontoon lifeboats are watertight. It is quite possible that the bulwarks of these boats will be of the all wood type in future construction, instead of the combined use of wood and canvas. Very few passenger vessels were completed during the war except as cargo-carrying ships, which considerably influenced the output of the boats with collapsible bulwarks.

The hull structure of a pontoon lifeboat is divided into a number of transverse watertight compartments, bounded by bulkheads built up in two thicknesses similar to the outside planking, and strengthened by longitudinal non-watertight bulwarks. The size of these watertight compartments are so arranged that should the structure become damaged with two compartments laid open to the sea, and having the full complement of persons on board, there would still be a reserve of buoyancy and sufficient stability to enable the boat to keep afloat without danger to the occupants.

The skin or planking is made up of two thicknesses of mahogany worked in diagonal fashion, and the planks are fitted from gunwale to gunwale at right angles to one another. The minimum width of the planks is 6 in., and between the two thicknesses is laid a covering or ply of stout calico and white lead-paint. Before the calico is worked the plank is treated with boiled linseed oil. An alternative preparation for the fabric is No. 5 Navy Canvas, laid in liquid marine glue.

These types of boats are very wide and shallow, giving a fullformed floor, and when stowed on deck and secured with gripes there is always a certain amount of "working" felt at the connection of the plank ends; the action of a seaway would have the same effect. To obviate leakage at the keel seam, and to maintain an unbroken skin to each compartment of the hull, the planks are fitted from gunwale to gunwale. The keel and bilge keelsons are fitted after the planking is complete, and the keelsons are formed with the usual hand grips to enable persons to cling to the boat should it capsize.

Lundin " Lifeboats.-Messrs. The Welin Marine Equipment Co., Long Island City, New York (now American Balsa Company Inc.), have specialised in the particular type of boats now under review. The London firm has been good enough to supply the writer with a number of photographs of the various designs from which illustrations have been produced.