What is the visibility like under the following situation:
on a lake
at night under heavily overcastted condition/or in a mild storm. (no moon, no star)
no other ambient light what so ever. (think you are in the wild, no light from the shore, no light reflected from near by cities.)
How dark would it be? What would the visibility be like without a lamp? How far would you be able to see?
What if you have a very small, non-focused oil lamp? How much would that help? How far could you see?
Are all ten rowing? If so, you’ll certainly go faster than 1.5 mph. When the wind dies, my wife and I can row a 17’ x7’ sailboat faster than that. With ten unskilled rowers, and no oarlocks, you’re talking at least 4 mph, maybe faster.
The head wind Q depends on the style of boat. The higher the boat stands out of the water, the more effect the wind will have.
On the visibility, it will be as dark as the inside of a moose. A single oil lamp will make you visible to other boaters, but the light shines into your own eyes, so it bleaches out your night vision chemicals (visual purple.)
You don’t say where this hypothetical lake is, but in the US, a 25 foot boat is required to have more lights than that. A single white light is OK if you’re anchored, but if you’re moving, you need a red/green light set on the bow and a white light on a stalk at the stern.
I have a feeling that you’re asking about an emergency situation, though.
I’m not sure what you are getting at, but visibility would be poor under those conditions. Visibility distance would be greater than, say in a wooded environment or a city due to the lack of obstructions. The horizon would limit the maximum distance.
Certainly the water wouldn’t enhance anything or provide any light.
As an anecdotal experience, I can tell the story of some fishermen who headed out on Lake Michigan at 4AM one dark morning. They may have had lights on their boat, but no searchlight in front. As they cleared the canal breakwater, they thought, “no one around to worry about or look out for,” so they opened up the throttle.
Unfortunately, they ran full speed into a 10-ft metal buoy with a 2-ton cement base used to define the channel and their boat disintegrated. So I guess visibility (or smarts) wasn’t very good that day.
Also, there can be quite a bit of fog that forms over lakes at night, depending on the weather conditions the previous day. Visibility could be severely affected by that.
I took my canoe out onto a fairly large lake near my home one morning at 3:30 am. I was a little drunk at the time, and it seemed like a cool idea. It was DARK and I became very disoriented. After hitting a partially submerged something and almost capsizing, I gave up. Unable to backtrack, I just sat and awaited sunrise.
What kind of rowing? Like with an old-fashioned row boat? I’m having trouble picturing what type of boat you’re thinking of that can have ten people rowing all together. Racing shells only hold 8+coxswain. Whale boats are kinda rare and not usually seen on lakes. Dragon boats hold a lot of people but are really slow. Or are you talking some sort of paddling like with a kayak or a canoe?
Regardless of the boat, six hours is a long freaking time. I’ve done marathon rows (26.2 miles) and they took 3 and a half hours and I was totally beat at the end (not to mention that my hands were completely shredded). As for speed, in an all out race, maybe 2000 meters in 8 minutes for a racing shell. That’s 9 miles per hour. You won’t be going anywhere near that fast. 1.5 mph is probably reasonable, especially if you’re just paddling. Head wind will make a huge difference, not just in speed but also in how fast your rowers will get tired out.
Visibility will be crap. If you’re worried about other peopel being able to see you, you can make pretty decent lights out of LEDs. We use cheap LED keychain lights strapped to a plastic card to make up our bow and stern lights. White for the stern light and red for port (left side) and green for starboard in the bow. If you’re worried about spotting stuff in the water, get a good spotlight, station someone in the bow, and go slow…
Based on your previous question and this one, can I guess you’re writing some kind of historical novel?
Nowadays, ambient light is kind of hard to avoid. However, without any nearby lights and no moon, a lake would be extremely dark. Navigation would be tricky to say the least. Even during the day, it’s often hard to figure out where you are on a body of water. An oil lamp wouldn’t help a bit except maybe to illuminate a compass. And assuming your protagonists are skulking about (why else would they be rowing in the inside of a moose?), the light would just give away their position.
Speed of the boat depends on how heavily it’s loaded and its construction. But 1.5 mph would be on the low side. A headwind could slow it down substantially, not only by wind resistance but also by kicking up waves and making navigation even trickier.
If you’re far from civilization, the sky is clouded over, it’s night, and you have no lights on board, then there’s just plain no light source. Many people don’t appreciate that even the animals with the best night vision still need some light to see. With no light at all, you can’t see, period.
However, once you start introducing light sources, things change. In such conditions of total dark, if there were a single light source, of any sort (even a single candle), above the horizon, you’d be able to see it (provided that it’s still dark in your immediate vicinity, and your eyes are well-adjusted, and it’s clear at surface level). If you have an oil lamp on board, it’d probably be enough to read your compass (essential, or you’ll end up going in circles), and might be enough to identify what it was you just ran into, but probably not until after you ran into it (unless it’s something very big and obvious).
Oh, that changes things. Anyway, I am often out on the lake at night. Even though Town Lake is right in town so there’s a fair amount of ambient light, it can be very difficult to see much on the water. Even white boats blend into the darkness. A lot depends on the weather/moon. Full moon, clear skies, visibility is actually not bad at all. No moon or very overcast skies, it’s very difficult to see anything. One of the boats out with us Tuesday (a very overcast night) didn’t have lights. I couldn’t see it until I was maybe 15 feet away and that’s with ambient light.
You gussed right, it is for a historical novel.
It’s probably an old style row boat. So not all people would be rowing together.
Based on your responses, I would say 1.5 mph is a very conservative estimate as long as you don’t get lost.
As for visibility: So it is probable that you might be 50 feet next to the shore and not realising it? (Actually, in normal rowing motion, would the oars go very deep?)
I don’t know if being on a lake would change anything, but I don’t see a reason why it would.
Try it by yourself (being in the countryside, with no moon and an overcast sky) and you might be surprised, as I was when it happened to me. There should still be some light, so it won’t be pitch dark, but still very close. Basically, you’ll see nothing. Let’s be generous and assume your rowers will notice shapes a couple meters away if they pay attention.
With a lamp, it would be significantly better, since at least you’ll see what’s ahead of you. But it is to be hoped that you’ll have some way to know where you’re going (in my case, there were some candle lights in the distance. Don’t ask what I was doing walking in the dark in the direction of candle lights). The advandage in this situation is that you’ll easily see even a tiny source of light at a distance.
Something else : with a modern lamp, you can illuminate and see things at quite a distance. With an old candle-lamp, I’m not sure how it would work out, thought many had a kind of moving “shutter”, allowing the bearer to get a directionnal ray of light. So, I would suspect it should be possible to see the shore 50 feet away, and very possibly at a much longer distance with such a lamp, but I’m not sure at all.
