2o6. 



NATURE 



[November 15, 19 17 



The Porsgrund Cement Castings Compiiny took 

 up the question of ferro-concrete vessels in 191 3, 

 and built a bridge pontoon in 1915 which is I 



most, and using an inner shutter, 

 ing only, so far as the vertical 

 cerned. This plan was adopted 



Fig. 2. — Vessel turning o 



claimed to be the first vessel of this type built in 

 Norway. This vessel was cast with double board- 

 ing, or shuttering, in the walls. Experience of 

 Ihis method 

 showed c o n - 

 siderable diffi- 

 culties; the ar- 

 rangement o f 

 the reinforce- 

 ment gaA-e 

 trouble, and 

 there was no 

 guarantee that 

 the iron would 

 be in proper 

 position. Cast- 

 ing the con- 

 crete also was 

 trouble so me, 

 and one or two 

 places were 

 found where 

 faults had to 

 be remedied. It 

 was considered 

 that these 

 difBculties with 

 pontoons hav- 

 ing fairly rect- 

 angular section 

 would become 

 very pronounced in building vessels of ordinary 

 section, and Mr. Harald Alfsen has overcome 

 them by building the vessels bottom upper- 

 NO. 2507, VOL. 100] 



I to 2 without cobbles was used, 

 ness is i"97 in. 



•or outer board- 

 sides are con- 

 with the lighter 

 Beton L, in- 

 terior shutter- 

 ing only being 

 used. This 

 vessel is a 200- 

 ton deadweight- 

 carrying motor 

 vessel ; the cal- 

 culations and 

 design were 

 prepared b y 

 Messrs. Bonde 

 and Norman. 

 As the vessel is 

 intended to be 

 sea-going, the 

 reinforce m e n t 

 was made 50 

 per cent, 

 heavier than in 

 lighters in- 

 tended for in- 

 land waters, 

 rib and girder 

 dimensions 

 were increased, 

 and a fat con- 

 crete mixture of 

 The wall thick- 



The shuttering was built on a sledge, which 



Final stage of launching 



followed the vessel into the water at the launch. 

 Fig. I shows the vessel travelling down the 

 ways, bottom uppermost, as built. On becoming 



