The Banner in the Gust
The parish banner has gone along the cliff on the Sunday before Saint Piran's Day every year since 1936, and this year a fifteen-year-old is carrying it for the first time into a forecast gust of 15 metres a second. The parish assistant works out what the wind will ask of his hands, 364 newtons on the cloth and about 1,240 at his upper grip, tests the figure with a luggage scale on the churchyard gate, and will not say yes. The answer is a rule, a sleeve and a lee, and it costs the family their pride for 300 metres.
Bert Trevenna had carried the Piran banner on the Sunday before the saint's day for forty-one years, and on the last Sunday of February his shoulder told him, in the vestry, in front of the whole of the altar guild, that it was done.
He did not say so. He said that Jory would carry it, as if this had been settled at the christening, and Jory, who was fifteen, and fifty-two kilos, and the third Trevenna to be asked, said "Okay" in the voice of a boy who has just been handed a live fish.
The banner was silk on a crossbar of ash, one metre twenty wide and one eighty deep, with Saint Piran's black cross on white, which the parish said was the old flag of Cornwall and the Church said was the saint's, and nobody had ever quarrelled with the other. It hung from a pole four metres long, which stood in a leather cup on a belt at the carrier's hip. It had been carried a mile and a quarter from the church to the cross on Carn Gwyn every year since 1936. It had gone in 1940. It had gone, with its silk patched, in 1987, when a gust had taken it out of Bert's father's hands on the cliff and put it in a gorse bush, where it had stayed until the Monday.
The forecast for the Sunday said south-westerly, gusting fifteen metres a second at eleven.
"I'd like to put a number on that before anybody puts a boy under it," said the assistant, which the parish called Chough, because the first priest to install it had kept a pair on the cliff and thought it was the right sort of bird for a thing that sat on a wall and listened. It was speaking from the vestry tablet to Bert, Jory, Morwenna Pascoe, who was sixty-three and ran the procession and had run it since Bert's wife died, and Father Nick Carne, who was in his second year at Porthgwyn and had not yet been told about 1987.
"Fifteen metres a second is fifty-four kilometres an hour, thirty-four miles an hour, a Force 7. The pressure of moving air on a flat face is half the density times the speed squared. Air on a cold morning is about 1.25 kilograms to the cubic metre, so that's half of 1.25 times 225, which is 140 pascals. The banner is 1.2 by 1.8, 2.16 square metres. A flat plate of that shape in a wind takes about 1.2 times the pressure, because the air piles up in front and sucks behind. I am guessing that 1.2; a silk banner on a bar will not be a flat plate exactly. So the push on the cloth is 140 times 1.2 times 2.16, which is 364 newtons. About thirty-seven kilos, leaning on a pole."
"I've carried it in worse," said Bert.
"I believe you have, in a wind that was a bit lower, or from behind, or between the gusts," said the assistant. "I don't doubt that it can be done. I want to know what it costs the person who does it, because I think it's a lot more than thirty-seven kilos. Jory, will you hold the pole for me, as you'd carry it, in the cup?"
He held the empty pole in the vestry with the cup on his belt, and the assistant asked him to put his hands where Bert put his, the lower one at about half a metre above the cup and the upper one a metre. The centre of the banner, when it hangs, is about two and a bit metres above the cup.
"The wind pushes at the middle of the cloth," said the assistant. "Your hands are a lever. The push is 364 newtons at 2.2 metres; your lower hand is half a metre up and your upper hand a metre. If the lower hand does nothing but pivot, then the upper hand has to pull 364 times 1.7, divided by half a metre, with the 1.7 being the gap from the pivot to the cloth. That is 1,240 newtons. A hundred and twenty-six kilos. At the top of a lever you are standing under."
Nobody said anything.
"You weigh fifty-two," the assistant said, gently. "That's 510 newtons. A grip of 1,240 is two and a half times what you weigh, for the length of a mile, in a boy's wrists. I don't mean you couldn't hold it for a second. I mean that I cannot find a way in which you hold it for a mile. And a mile on a cliff in a gust is exactly the place you would let go, and the banner and the pole come down on whoever is behind you."
"There's the cords," said Morwenna. "We've always had cords."
"There are, and they help; I'll come to them. Before that I want to check my own figure, because I told you I'd guessed at the 1.2. There is a better way than an argument, and it needs a luggage scale and the churchyard gate."
On the Saturday afternoon the tower anemometer, which the parish had put up for the bells and the flag and not for any good reason, read gusts of nine metres a second from the south-west, and Jory and Morwenna tied the pole by its crossbar to the lych gate with a luggage scale in the line, the cup standing on a block on the path, and the banner open.
"Nine metres a second," said the assistant, "gives half of 1.25 times 81, which is 50.6 pascals, and with my guess that is 131 newtons. A little over thirteen kilos. What does the scale say at the top of a gust?"
Morwenna read it off, shouting over the wind: twelve kilos, and once twelve and a half.
"One hundred and eighteen to one hundred and twenty-two newtons. So the true figure is about eight per cent under mine, and the shape coefficient is nearer 1.1 than 1.2. Thank you; that is as good as I can expect from a tower wind that is not at the banner and a scale marked in half kilos. I'll keep 1.2 for tomorrow. If I'm wrong it is wrong on the side of the boy."
"And what's the answer?" said Bert, from the bench by the porch, where he had come without being asked.
"The answer is a speed," said the assistant. "A grip equal to Jory's own weight is my limit, because it is the point at which a good boy leans back and still goes forward. Five hundred and ten newtons of grip is 150 newtons on the cloth. 150 divided by 1.62, which is half the air density times my 1.2 times the area, gives 92.6, and the square root of that is 9.6. So I'd call it nine and a half metres a second, a gust, on the anemometer. Under that, he carries the banner open, and two people hold the cords. Over it, the banner is furled. I did not get that from any standard. It's my rule, and Father or Morwenna may change it."
"Furled," said Bert.
"Rolled up the pole to the crossbar and tied, in its sleeve. You've a sleeve; I've seen it in the biscuit tin. The cloth then takes about a quarter of a square metre. At fifteen metres a second that is thirty-six newtons, and Jory's hand is a hundred and twenty. Twelve kilos. He could carry that to Land's End."
"It's a banner," said Bert. He had a voice for this, and it was not loud. "It isn't a flag you roll up. It's a banner so as people on the cliff can see it."
"Yes," said the assistant. "And that is what it costs. For the part of the route where the wind is not covered, which is the three hundred metres along the top, nobody on the cliff will see it, and they'll see a boy with a pole. I'm sorry. I couldn't find a way to give you both."
Father Nick said he would like to think about it, and thought about it in the sacristy for ten minutes, and came back and said that the rule was the rule and he would be glad if Morwenna would set up the anemometer at the cross.
Bert did not come to the church on the Sunday morning. He was on the bench by the porch when the procession formed up at ten to eleven, in his good coat, with a flask, and he did not speak to Jory, and Jory, in the cup and the belt with his father's old waxed jacket on, did not look at him.
The wind on the tower read eleven, twelve and then thirteen. Morwenna had the hand anemometer on the wall by the gate. "Twelve and a half in the gust," she said, "at the corner."
"Furl it," said the assistant, in her ear, in the voice it kept for these things.
They did it in the lee of the church wall, two of them, Jory and a girl called Demelza Rowe who had done it before for the school's flag: the cloth rolled twice round the bar, tied with the three cords from the sleeve, so the black cross showed as a tight dark stripe. It looked, said somebody, like a washing line with a cross on it. Jory heard that. He lifted the pole into the cup and set off in front of the cross, with the whole parish behind him and the sea on the left, grey and tall and noisy, and did not look round, because there was no reason to; the pole in his hands was light.
They went along the top at a good pace, singing the hymn into the wind, which took most of it. Nobody on the cliff, which was perhaps a dozen walkers and a man with a dog, knew what they were looking at, until they saw Father Nick.
At the foot of Carn Gwyn the path turned inland behind the hill and the wind fell away as if a door had been shut. Morwenna read it off the wall of the old engine house: five and a half, gusting six. At six metres a second the push on the open cloth is 58 newtons, and the grip at the top of the pole is 200, twenty kilos, which is a heavy thing but a thing a boy can do for two hundred metres.
"Open it," said the assistant.
Demelza and Morwenna each took a cord, in the way of the old photographs, at forty degrees either side, and Jory stood for a moment alone at the foot of the hill while Demelza picked at the knots with her cold fingers. It took a long time. Nobody helped, because there was a way of doing it that nobody remembered, and she was doing it.
Then the cloth dropped out of its roll and hung for one breath against the pole, and a gust came round the shoulder of the hill, the only one that reached that hollow, and filled the silk and cracked it once, loud as a door, over a boy's head, and the whole parish heard it.
Bert Trevenna had walked up the hill behind them by the quarry path, slowly, with his bad arm in his coat, and he was standing at the cross when they came. He did not say anything about the sleeve. He said, "You kept it straight," to Jory, and Jory said "Yes", and neither of them looked at the other, and Father Nick said the short blessing at the foot of the cross with the sea gone quiet behind the hill.
Bert had a way of holding the flask. He held it out afterwards, unscrewed, and Jory, who was fifteen and under age, took a mouthful of cold tea, which was what it was, and gave it back.