Know Various Parts of Your Sailboat
Sailboats are not like cars. You definitely know that you can drive your car without necessarily knowing how the car's piston or engine works. All you have to do is use the ignition to turn on the engine, shift into the required gear, step on the gas pedal and you'll be good to go. Unfortunately, the same cannot be said of a sailboat. Well, you have to play a far more active role in bringing together and harnessing the power that propels the sailboat forward, which in this case, is the wind.
Without having the winds in your sails, the boat will not move forward. Instead, you'll only drift along and get stuck in the neutral. Worst still, you can easily capsize. As such, it's of great importance to have a good grasp of how the wind works in propelling a sailboat and what you can do without it.
When there are forces of the wind on the sails, it's referred to as aerodynamics and can propel the sailboat by lifting it in the same way the winds lift an airplane wing. Generally, the force of the wind that lifts and propels the sailboat often contains sideways force and small forward force and so you need to trim the sails accordingly so that you can experience the least resistance. But what happens when there's no wind? Well, here's what you can do.
You can rely on Hydrodynamics of the Water Flow
As we noted earlier, it's physically impossible to have a total absence of wind while out there on the water. But even if it happens, which is of course very rare, you can rely on the heat from the warm zone to the cold zone, which will definitely create some form of hydrodynamics or flow, which would then create currents to at least propel your sailboat even if not in the same way as the winds.
In terms of relativity, strong winds may not be of great help to you when it comes to propelling your sailboat if it's accompanied by insignificant currents. Similarly strong currents with insignificant winds may not be of much help in propelling a sailboat. However, many modern sailboats are designed in such a way that they can work just fine even when there are strong currents with insignificant winds without a lot of modifications.
The most important thing is to ensure that the sails of your boat are relative to the existing strong currents. For example, if the existing currents have a speed of 15 knots, it would be easier to propel your sailboat using the same exact techniques you'd use when you have the winds or 15 knots. The idea here is the many modern sailboats are designed with hydrodynamic engineering techniques that make them feel as if you have 15 knots winds when the currents are at 15 knots.
The only difference may revolve around the fact that in addition to the normal sailing speed that you're managing, you also have to manage the 15 knots offset in the direction of the currents. This explanation may seem complex from the onset but it's pretty much easy. When there's no wind and you're trying to sail with the current, it means that you're technically trying to sail upwind, so you have to apply the similar techniques that you always use when sailing upwind.
Sailing with the Current
Simply put, sailing upwind means that you're sailing exactly anti-parallel to the wind. This revolves around the wind blowing into the sails and pushing against them. The science behind this is that the wind is faster than a sailboat, which leads to the air getting decelerated by the sails. The sails will push back against the wind so the wind pushes forward on the sails. It's a lot easier to sail upwind because the wind pushes you in the same direction it is going but it may not offer the most interesting way of sailing.
The same can be said when you have to rely on the currents when there are no winds. The only difference is that the currents will push the keel if you're sailing in the direction of the currents.
Sailing against the Current
The problems revolving around sailing without winds may start sneaking up their heads when you're sailing against the currents. You will most likely drift along, remain afloat, or even make negative progress. As such, the best thing is to deal with the situation by tiding over and doing your best to remain afloat until the winds fill up your sails.
You have to remember that it's almost impossible to control the direction of your sailboat by just relying on a single strong current. Generally, a sailboat can only go in a different direction from the direction in which the wind is blowing because it has a second sail, which is the keel under the water. But because you can no longer use the actual sails, you only have the keel and it will be impossible to apply both the aerodynamic forces of the wind and the hydrodynamic forces of the water currents, and your sailboat will most likely remain stagnant or make a negative process if you have to travel against the currents with no winds.
On the contrary, if you're drifting the direction of the very fast currents, you'll get your sailboat moving even when the wind speed over land is zero. Of course, you won't get lots of speed but you'll make some progress.
Relying on Propellers
If your sailboat has motor propellers, then it will be pretty much easy to propel your sailboat even when there are no winds. The propeller works by literally using a portion of the forward energy to propel the sailboat forward while directing the same energy back to the propeller to blow backward. This then creates additional energy and an additional thrust in some form of a domino effect or an amplifying cycle.
So if you anticipate that a time may come that your sailboat might have to work without wind, you can choose to fit your sailboat with a folding or feathering propeller to give you an extra knot when the sails seem not to be the reliable option just because there are no winds. Many modern propellers are designed not just to minimize drag but also in a position perpendicular to the water flow. This is to help them have a neutral cutting edge to the water and can propel the boat ahead.
If your sailboat does not have motor propellers and you do not want to rely on the currents, your remaining option would be to go back to the good old days when muscles were the order of the day. You can do it the way Egyptians and Romans used to do by rowing your boat. This can be quite exhausting but it's good for your body and soul if you have to move forward at all costs.
The idea here is that you have to be your own wind by creating opportunities for yourself. Rowing will be tiresome but it can give you the right momentum that you need when the wind comes back. So if there is no wind, no propellers, and the currents are working against you, rowing could be an ideal alternative.
To this end, it's important to be prepared in the event that there are no winds to propel your sailboat. Knowing what to do in such a situation can be the difference between life and death. And even if you've decided to sail with the water currents, use propellers (if they're already fitted on your boat), or have to row your boat, just don't take your sails down. It won't be long before the wind comes so you should give up just yet.