Another question (I am adrift)

[KitingHigh]

I’m on a sailboat, but there is no wind.
The boat is on a river.
The river is a mile wide and flowing at about 6 miles per hour.
My destination is downriver.

Will I get there faster with the sails down or up?

 

[SeaPA]

Yes.

 

[LesClaypool]

I would use the emergency outboard motor to be sure.

 

[NoleFan2U]

Down. They will provide more drag if up with no wind?

I dunno. Just a guess.

 

[KitingHigh]

I would use the emergency outboard motor to be sure.

Good answer. I had to do that yesterday, though it was an inboard Diesel engine. And I was in a current rather than a river and my destination was up current.

 

[KitingHigh]

@F4Gary you should get this one. Sailboats and planes use the same physics.

 

[F4Gary]

I was thinking the same as NoleFan2U, the sails would create drag if there is no wind. But they could also let you change your position in the river to find the fastest current channel.
I guess you could wave the sail back and forth to maybe create a little thrust, kinda like fanning yourself.
?

 

[KitingHigh]

I was thinking the same as NoleFan2U, the sails would create drag if there is no wind. But they could also let you change your position in the river to find the fastest current channel.
I guess you could wave the sail back and forth to maybe create a little thrust, kinda like fanning yourself.
?

So the first part is that if there is no true wind and the boat is drifting with the current, the apparent or effective wind would be that of the current. That would create drag.

However a sail is a foil just like the wing of an airplane. By raising the sail and trimming it properly it will create lift. It will create it on a horizontal plane rather than a vertical one. Thanks to the principals discovered by Venturi and Bernoulli, sailboats can sail toward the wind. Not directly into the wind, but close. The boat is moving relative to the air so the sails do have an effective wind force on them and they will function properly.

By raising the sails one can sail towards the wind and tack (zig zag) across the river and forward thus increasing his VMG toward the destination.

It's not all that dissimilar to the question of whether or not a plane can take off if its on a treadmill. It doesn't matter what the wheels are doing. It's what the prop or jet is.

Also, creating some thrust is essential. Without movement relative to the water the control surface (rudder) is ineffective and you wouldn't have any ability to steer (aside from using the sails as control surfaces since there is relative movement through the air, good call on that).

 

[NoleFan2U]

So the first part is that if there is no true wind and the boat is drifting with the current, the apparent or effective wind would be that of the current. That would create drag.

However a sail is a foil just like the wing of an airplane. By raising the sail and trimming it properly it will create lift. It will create it on a horizontal plane rather than a vertical one. Thanks to the principals discovered by Venturi and Bernoulli, sailboats can sail toward the wind. Not directly into the wind, but close. The boat is moving relative to the air so the sails do have an effective wind force on them and they will function properly.

By raising the sails one can sail towards the wind and tack (zig zag) across the river and forward thus increasing his VMG toward the destination.

It's not all that dissimilar to the question of whether or not a plane can take off if its on a treadmill. It doesn't matter what the wheels are doing. It's what the prop or jet is.

Also, creating some thrust is essential. Without movement relative to the water the control surface (rudder) is ineffective and you wouldn't have any ability to steer (aside from using the sails as control surfaces since there is relative movement through the air, good call on that).

Well you didn't say i had to sail the boat too

 

[totallynot321Nole]

Well you didn't say i had to sail the boat too

To be fair, he said he was the one adrift. The rest of us get to drink cocktails and forget to tip him.

 

[Oclawaha]

Don’t some rivers flow south to north in the northern hemisphere? I’m not even sure which way is downriver in those cases.

 

[CC0492]

Question: But if you are tacking back and forth across a mile wide river, won't you be increasing the distance and time required to reach your destination, rather than travelling in a straight line with the sails down at 6mph?

 

[Squirrel J.]

Before you got to the river, did you leave a good job in the city
so you could work for the man every night and day?

 

[Nole-4-Life]

How do you steer? If a boat isn't under power, be it motor or sail, it won't respond to the rudder.

 

[KitingHigh]

Don’t some rivers flow south to north in the northern hemisphere? I’m not even sure which way is downriver in those cases.

Contrary to the claims from Jacksonville there are over 200 rivers that flow south to north in the northern hemisphere. The most well know is of course the Nile and in Florida the St. John’s.

Regardless of the cardinal direction, downriver is always the easier way.

Go with the flow.

 

[KitingHigh]

Question: But if you are tacking back and forth across a mile wide river, won't you be increasing the distance and time required to reach your destination, rather than travelling in a straight line with the sails down at 6mph?

You will increase the overall distance traveled. However you will also increase the VMG (velocity made good) toward the destination.

Imagine you are on a piece of paper that is on a treadmill. You start at one edge and the opposite edge will get to the other end of the treadmill first. If you just let yourself drift with the paper you will get to the edge of the treadmill the same time as the trailing edge of the paper. But if you zig zag your way to the front of the paper while it drifts you will reach the end of the treadmill earlier with the leading edge of the paper. You will have travelled more distance overall, but your effective speed toward the destination will be greater and you will get there sooner.

 

[KitingHigh]

Before you got to the river, did you leave a good job in the city
so you could work for the man every night and day?

Yes, and no

 

[KitingHigh]

How do you steer? If a boat isn't under power, be it motor or sail, it won't respond to the rudder.

Good question. I kinda addressed it earlier, but the answer is to put up the sails. Then the boat will generate some speed through the water and the rudder will then work.

If you’re really good, and I am, you can actually steer the boat by trimming the sails a certain way.

The key is that the boat moving with the current will actually generate apparent wind, which will give the sails power.

 

[Oclawaha]

Contrary to the claims from Jacksonville there are over 200 rivers that flow south to north in the northern hemisphere. The most well know is of course the Nile and in Florida the St. John’s.

Regardless of the cardinal direction, downriver is always the easier way.

Go with the flow.

OK let me see if I understand. Even in the case of rivers that flow south to north, downriver, or north to south is faster?

 

[KitingHigh]

OK let me see if I understand. Even in the case of rivers that flow south to north, downriver, or north to south is faster?

What river?

 

[F4Gary]

OK let me see if I understand. Even in the case of rivers that flow south to north, downriver, or north to south is faster?

Good grief. Down river is with the current flow. Up river is against it.

 

[Nole-4-Life]

How do you steer? If a boat isn't under power, be it motor or sail, it won't respond to the rudder.

Good question. I kinda addressed it earlier, but the answer is to put up the sails. Then the boat will generate some speed through the water and the rudder will then work.

If you’re really good, and I am, you can actually steer the boat by trimming the sails a certain way.

The key is that the boat moving with the current will actually generate apparent wind, which will give the sails power.

But you definitely have to have some sort of propulsion to steer. That was my only point.

 

[Oclawaha]

Ah forget it. I’ll drive.

 

[KitingHigh]

But you definitely have to have some sort of propulsion to steer. That was my only point.

And you are correct. The sails provide that propulsion.

 

[KitingHigh]

Well you didn't say i had to sail the boat too

I never said you were on the boat.

 

[PoopandBoogers]

Ive seen where they put some kind of sail under the boat to catch the current when there's no wind. Do that, kick back with a cocktail in one hand, other on the rudder. Profit.

 

[Gonolz]

I'm not a complicated man with fancy answers. When I run into a question like this, I'm pretty sure the right answer is a simple one. That being said, the answer is "gators suck".

 

[TennNole17]

Folder.

 

[SoddyNole]

Good grief. Down river is with the current flow. Up river is against it.

Unless you are in an eddy.

 

[squiffynole]

Use the sail to fashion a sea anchor to increase the effect of the river current.

 

[62Nole]

Don’t some rivers flow south to north in the northern hemisphere? I’m not even sure which way is downriver in those cases.

Not sure. Never used a compass on a river. However, hemispheres are
important and not the same in all ways. Dan "The Quiz" Quisenberry, formerly of the Kansas City Royals, related how south of the equator water flows backwards when a toilet is flushed. What happens in the shower?

 

[More Kirk Less Spock]

Sea Tow?

 

[Oclawaha]

Not sure. Never used a compass on a river. However, hemispheres are
important and not the same in all ways. Dan "The Quiz" Quisenberry, formerly of the Kansas City Royals, related how south of the equator water flows backwards when a toilet is flushed. What happens in the shower?

Hellifiknow. The only thing I know about water at this point is that it’s wet and that it rolls downhill.
I guess.

 

[squiffynole]

This thread reminds me of quiet weekday at St. Marks when I had to cock my bimini like a sail to come back in from the bird roost. And the time I was lost in the Apalachicola distributaries. Then there was being towed by a sailboat from Boca Grande Pass to Matlacha. Boating is full of adventures most of which I never told my wife.

 

[LLOYD72]

I have never understood sailing where you are at the mercy of the wind. I am a powerboat guy and go where I want wheni I want....except if I run out of gas

 

[SeaPA]

Don’t some rivers flow south to north in the northern hemisphere? I’m not even sure which way is downriver in those cases.

Rivers flow downhill. Doesn’t matter whether it is north, south, east, or west, nor does hemisphere matter.

 

[F4Gary]

Rivers flow downhill. Doesn’t matter whether it is north, south, east, or west, nor does hemisphere matter.

Really? I'll be.

 

[62Nole]

Sung-a-dung!! Never considered gravity. I mean the "pull"
type, not the really serious type.

 

[KitingHigh]

I have never understood sailing where you are at the mercy of the wind. I am a powerboat guy and go where I want wheni I want....except if I run out of gas

I have good friends that are power boaters. When they comment on sailboats being slow I challenge them to a race... to Hawaii.

Seriously, though sailboats can sail against the wind and are equipped with engines for when there isn’t wind.

There are many reasons people prefer one or
The other; but the simplest is probably this: The average power boater is more concerned about the destination; while for the average sailor, the journey is the destination.