Volume Ten - Pre-Victorian to the present day - even more aspects - The Patent for the Penarth Slipway - 1881 . . .

Mr. John Thompson cont'd :

He might mention the reason for not making such large slipways. As a practical question no doubt they could be made, and would act satisfactorily ; but the point was whether there was a sufficient number of ships of, say, 500 feet requiring repairs to render such large slipways profitable. It must be remembered that, although a dock capable of taking a ship of 500 feet could at another tide take two or more ships, so long as their aggregate length did not exceed 500 feet, yet the cradle of a slipway built to take these large vessels could not receive more than one vessel at a tide, however small it might be.

In this country, the majority of ships were from 200 to 300 feet long, and the size he had recommended was limited to this, merely to ensure constant employment, without which neither a slipway nor a graving-dock would be profitable in our larger ports.

With reference to the slipway at Penarth, the information given in the Paper was obtained about twelve months ago. According to his calculation there was one ship on it every five or six days, and he knew that some ships were on for very extensive repairs.

Mr. Giles had put the cost at £50 for each ship ; but the charge was not made in that way ; it was so much for docking, and so much per ton per tide for rent of the slipway. If a ship went on for extensive repairs, the cost would be say £10 or £12 for docking, and say 1½d. per ton per day for rent, so that profit was made by rental as well as by docking.

As to the straining of a ship by putting it on or launching it off the cradle, taking the inclination of the ways at about 1in 20, and remembering that the fore end of the cradle was not more than 18 or 20 inches deep, and the after end 6 feet, he did not think that as a rule there would be more strain upon the ship by placing it on the cradle than by putting it into dock where the blocks were level.

In a graving-dock the after end touched the blocks first and strained the ship, but so slightly that it had never been recognised ; and why there should be anything said of injurious strain when a ship was placed on a cradle he could not understand. The ship was put on, the cradle was hauled up, and no side-blocks were inserted until the after part of the ship touched the blocks. It did not heel over to the one side or the other, and there could not be a straining when that was the case.