I was watching a video on the HMS Victory (of Trafalgar fame…linked below and queued to the part where they talk about the ballast) and was wondering how the ship maintained its ability to sail as a voyage progressed?
The ships of that era did not pump in seawater as ballast. They had a certain amount of ballast to start but they also had considerable weight in consumables. Fresh water was 300 tons. 145 tons of food, 100 tons of ammo, 35 tons of gunpowder (and there’s more other bits but that is a lot of it).
As the ship moves about and engages in battles it is getting substantially lighter. Yet I see no way for them to add weight lost. Was this not important?
I once read that French sailors’ widows could only collect pensions if their husband’s bodies were buried in France, so the French ships would bury the corpses in the ballast for the voyage home.
The ships started with a certain amount of ballast that is always there.
My question is, as the ship does its thing, it is getting lighter. Modern ships just pump in seawater as ballast. But they did not do this (I do not think).
I would suppose keeping the ship properly ballasted and in peak sailing shape was a never-ending process. But sure…in the midst of a battle they probably were not dealing with it.
They tip over. Especially sailing ships which have those huge lever-arms (masts) pushing the ship over.
Famously, the Swedish warship Vasa tipped over and sank some 30 minutes into her maiden voyage in 1628. The center of gravity was all wrong and the wind tipped it over. Ballast is what stops that from happening (or at least is a big part of that). They have pulled it out of the water and it is now on display in a museum in Stockholm.
Fill a tub with water and put a drinking cup in it. It will tip over, and once it is on its side, it will fill with water and sink.
Then fill that cup with some water, if there is enough water in the cup (but not too much) it will stay upright and float but not tip over. That’s what sailors were dealing with.
You have listed about 600 tons. I believe Victoria was about 2500 tons. Add the weight of personal and you have a few more tons. If all the consumables are consumed that would be around 20%.The metabatic center would be a little higher and the ship will ride higher in the water and she will roll a lot more. But it will still sail. If a bad storm was encountered sea water could be added back into the empty water barrels. It would not be a comfortable ride but controllable.
I have been on an empty tanker. It rode really rough the screw was over 1/3 out of the water and every time one of the blades hit the water it would set the whole ship to vibrate. At 90 turns that was 180 times a minute.
In the 18th century there were two types of ballast. The permanent ballast was usually pig iron bars in various sizes. Occasionally old cannon were also used. …Above this was shingle ballast…these were smooth, rounded stones - usually from a sea beach
Whenever possible, the temporary ballast was some material that could be sold at the destination harbour, so being something like a high-density, but comparatively low value cargo… many houses in the Caribbean are built from bricks that came from Europe as ballast
If you are interested in how the stability of a sailing vessel is calculated, this video may be of interest. It is in relation to a boat, rather than a ship of the line, but the mathematics are similar.
Probably the strangest island in Australia is Bullock Island, Newcastle. Although not of pretentious appearance, it consists of soil from all of the continents of the globe. It has been formed of mud out of Newcastle Harbor, and of stone and earth which has been brought as ballast by ships from European, Asiatic, African ports.
[This is Newcastle in Australia, north of Sydney, then as now a major exporting coal port, so ballast was needed coming in but not leaving.]
Cargo isn’t a factor in ballast. Semi-permanent ballast alone should keep even an empty ship from capsizing as long as the weight of the ship is evenly distributed. Cargo (and provisions, artillery, ammo, etc) did have to be routinely redistributed during a voyage to keep the ship on an even keel and prevent capsizing but their weight is not used as ballast especially since much of it (like guns) is carried above the water line.
That was the entire point of mentioning it - the bricks were ballast in an otherwise empty ship. But it made sense to take something of some utility when possible.
Methinks you’re supposing wrong. I suppose they sailed with a relatively wide range of displacement and the consumption of stores generally didn’t move them out of that range.
I’d agree. The consumables would not be kept in the bottom of the hull and covered with ballast, they’d be kept higher up, perhaps above the CG, but close to the CG having little effect on balance compared to the soaring masts and sails.
Ballast was still dropped off in ports around the world after picking up cargo leading to interesting geological finds. The only known source for the mineral Cumberlandite, a heavy iron ore, is located in my town here in RI. The material had migrated from the one location on a nearby hill a few miles down to Narragansett Bay and there picked up by sailing ships and now found in ports around the world as discarded ballast.
