Sunday, April 17, 2011

Straw Ropes

During my recent research I came across a plan of Perran Foundry dating from 1860. Though that is 30 years later than the period of my new book, the plan was invaluable regarding the layout. At that time the foundry covered six acres and employed 400 men. Though the names on many of the buildings and sheds were self-explanatory: smith’s shop, engineer’s shop, milling shop etc. when I came across the straw rope shed it stopped me short. What on earth were straw ropes, and what would they be used for? I asked an engineer friend, and he had no idea. Then he spoke to his 90-year-old uncle who had been in marine engineering all his life and knew the answer.

Straw ropes were exactly what the name suggests, ropes made from plaited straw. Because each straw is hollow it holds air. Air has excellent insulating properties. So these straw ropes were closely wrapped around the boilers in early steam ships to form an insulating jacket, much like those we use today around our immersion heater cylinders. (It’s so obvious when someone explains.)

But straw is highly inflammable and there was always a risk from stray sparks when more coal was shovelled into the boiler’s fire box. To minimise this risk, sacking strips - similar to the old-fashioned lagging used around water pipes to stop them freezing in winter - were wrapped over the top of the straw. This sacking was first soaked in a solution of borax then dried, as borax was commonly used as a fire-retardant in the early part of the C19th. Unfortunately, as a safety measure this was all too often ineffective.


Anonymous said...

Surprising and interesting, and akin to the recent move to build houses from bales of straw for the same reason--the insulating power. Nothing new, I guess.


Jane Jackson said...

Thanks for your comment, Dick. Something else I found fascinating was the fact that all the lathes and other machinery in the foundry were were run by waterwheels - free power!