Wheat Googling #9

How do I get some natural light into the lower decks of my ship?

Good morning!

Well, I don’t know about you, but I have been having a bit of a time. A friend and I decided that, in order to give our children the kind of wholesome childhood we wish for them, we would buy a caravan to take them on adventures. Since a caravan is laughably far out of our combined budget, we instead decided to buy a 30 year old one for £1000 and renovate it. The late discovery of black mould under the old floorboards mean I have spent quite a lot of this week in the very sailorly occupation of cleaning and scrubbing a damp wooden floor. I am only thankful I have access to the kind of bafflingly named mould-defeating chemicals that 19th Century sailors could only dream of. Also, my back hurts.

Anyway, all this to say I am writing this at midnight. As promised, it’s about light.

Why was it so dark below decks on a sailing ship?

Well, obviously because there aren’t any windows on a vessel that needs to at least be a nodding acquaintance of the term ‘water tight’. They were stuck with lanterns, and those would swing about like mad if the ship was moving. Not ideal. Especially not ideal for performing surgery, which is why only emergency operations were performed in the dark orlop during battle, with everything else happening higher up.

Didn’t they have any natural light?

Yes! They did! Well, some of them did, anyway. The captain had those massive stern windows, as well as windows on the sides in the quarter galleries. Like this!

In fact, this is Admiral Nelson's cabin on the Victory, but you get the idea.

There might also have been skylights built on the quarterdeck (directly above the captain’s suite of rooms) to allow light into his other rooms.

For everyone else, there were gratings.

It is a hatch, as you see.

The grating provided light while also being something you could walk over, and if you took it off it also provided access to the deck below. If it was really wet weather, you could ‘batten down the hatches’.

What shall I do?

Well, here I will be borrowing from the Discovery again. With their somewhat more advanced technology, they used prisms!

These prisms give light to the officers' dining area below

This prism lights one of the officers' bedrooms below

The prisms are made of tough glass, and spaced a fixed minimum distance apart to protect the structural integrity of the ship.

On the ceiling of the deck below, as you will see in the next picture, a surprising amount of light can be generated by cutting little windows into the deck and knowing about light refraction.

As you can see, the light doesn't travel far, but it is fairly bright directly underneath it.

The Discovery had to make sure the ship was supple and strong enough to withstand being frozen into the ice for an entire winter, and that might be why their glass floor windows are basically just disks. A more effective way to diffuse light into a space is to use a much less flat prism.

So that’s what I will be doing. Do you remember the diagram from my last letter? Well, here it is again just in case.

This time, we are looking at the stars

See the crosses in diamond shaped boxes spaced about 2 metres apart on the weather (highest) deck, and in the waist of the upper deck (which is open to the sky)? Those are my deck prisms. And you see the stars on the deck beneath? That shows you where the light is coming from in those lower rooms.

So far, so good. I have managed to get actual daylight to an entire extra deck. But unfortunately, that still leaves most of the lower deck and all of the orlop in darkness. So what to do?

Well, I have had a bonkers idea which I am yet to find a physicist (or possibly engineer) to discuss with me. Here it is. I want to turn the three masts into gigantic sun tunnels!

What is a sun tunnel?

It’s basically a long cylinder with the interior lined with the most reflective substance the manufacturers can find. The top is laid into the roof, and the other end comes out in the ceiling of a room that has otherwise no access to natural light. You put one of our old friends, the prisms, in the ceiling of your previously dark bathroom to diffuse the light, and at the top of the tunnel you put a dome so it can catch the light from more angles. It looks like this.

I borrowed this picture from Lightway, a company who would like to sell you a sun tunnel.

These modern ones can send light down 20 metres and still provide plenty of light, though of course they benefit from modern manufacturing methods to make the reflective interior.

You see the thing is, a mast is basically a really long cylinder. And actually those towering masts you see on tall ships are in fact three shorter masts strapped together. The one at the bottom is only about 30 metres long. Now, we can’t have the kinds of technology that are available today, but I think I can construct a reasonable imitation using only 1890s technology (sticking to my scheme of allowing my ship innovations from later in the century).

Here is what I’ve come up with.

To answer your two questions: no, it's not to scale, and yes, I know what it looks like.

The ventilation shaft that goes all the way round the outside is to protect the inner sun tunnel from blunt force damage a bit, but also to keep it cool. A plus is that it will also allow the crew to ventilate the lower decks! The two little ears I forgot to label are little baffles at the point the mast goes down into the ship proper, and are again to protect it a bit.

Now, I found this particular bit of wheat googling literally impossible. I can find information about sun tunnels, and I can find information about how they made really shiny mirrors in the 19th Century. I can establish that hollow masts are a thing, and that they are used for ventilation. But I can’t find out how much light will actually get down to my aperture in the orlop. So, if you are, I don’t know, some kind of glass engineer/ship expert/materials scientist, please do get in touch!

Enjoy the rest of your day!

Grace xx

PS: Thanks to Nina for pointing out that I misspoke in my last letter, and claimed that cutters were famously fast but unmaneuverable. I mean to say that clippers were like that. Cutters actually were pretty nimble.

PPS: It turns out that writing one of these every two weeks is really hard, so I’m dropping it down to once a month. x

Next time

I am gearing up to write you a deep dive on leisure time, but I think I might keep things simple next month and write about buttons and epaulettes. Have a lovely September!

This week’s interesting link

A forum thread about different methods of ventilating the lower decks of a warship in the Age of Sail.

I love the model ships community. I have so often managed to find the answer to a really obscure question on their many detailed forums.

Right now, the project for which I am doing most of my wheat googling is a choose your own adventure IF game I’ve been commissioned to write for Choice of Games. You can find out all about it, and play the 60K word demo, here.