Never-Wet is a superhydrophobic spray-on coating that repels water. Would the boat sink?
No, it wouldn’t sink (unless it would have sunk without the coating).
For a boat of any practical size, the coating wouldn’t make a significant difference in how the floated in the water. For a very small (toy) boat, it might make a difference. Hydrophobic coatings are why ducks float - they sink if the coating is removed.
No.
Never-Wet has no effect on buoyancy. From your perspective, nothing would happen.
That, surely, is because their feathers will become saturated with water so that they are no longer buoyant. It is not the not the hydrophobic effect as such that keeps them afloat. They float due to buoyancy, just like anything else (including a toy boat). For ducks, however, much of that buoyancy is provided by air trapped amongst the feathers.
Really, it is not correct to say that hydrophobic stuff repels water. There is no force pushing the water away. All it means when a surface is said to be hydrophobic is that water will not soak in, or wet the surface with a thin coat of water. Rather, if it gets wet, the water will run of easily, quickly and more completely than it will from non-hydrophobic surfaces.
Why, the same thing that would happen if you took Imodium and Ex-Lax at the same time. It would create a tiny black hole spinning off two alternate universes in which both of you are in agony.
But seriously, a boat floats because its density is far, far less than its surface area. Unless the coating will increase the density of the boat to overcome the huge chamber of air the cabin holds, it won’t sink or even sneeze at the water.
Except for very tiny things, like water striders which “float” by surface tension of the water, not buoyancy. They can only do that because their legs have hydrophobic hairs.
So next question then, if I painted my boat with it, would it improve my gas mileage?
I think that it would slightly decrease drag but given all of the other forces in play, it wouldn’t have a noticeable effect.
If it reduces drag, then yes. But probably very nominal at best.
It is partially a question of semantics. At the atomic level, polar and nonpolar molecules may actually attract each other, but at the macroscopic level, we still see a repulsive hydrophobic force. This force is a so-called entropic force, resulting from the statistical trend toward higher entropy. It is very real at the macroscopic level, even if we can’t easily identify a repulsive force at the microscopic level. See for example: Wikipedia: Entropic Force.
Note also that some have proposed that familiar forces like gravity are actually entropic forces.
I think you have the right idea here but you can’t compare density (m/v) to surface area (d[sup]2[/sup]). Also density can be a bit of a red herring unless you’re careful about how you measure it. A boat floats because its volume is greater than that of the water it displaces.
What if you coat a boat’s hull and propeller with the stuff and then put it in a river pointing upstream? The water would never come into contact with the propeller, so the prop couldn’t move the boat against the current, but the river would never touch the boat so it couldn’t push the boat downstream…
Well, you seem to be using “macroscopic level” in a bit of an odd sense here. AFAIK the notion of a “hydrophobic force” (as a sort of useful fiction) may have a certain value when you are talking about things at or around the molecular level, such as the the conformation of protein molecules or the formation of cell membranes. It is a way of talking about, and even getting quantitative about, how, in an aqueous environment, hydrophobic molecules, or molecule parts, tend to clump together. At the more realistically macroscopic level that this discussion was actually concerned with, the level of ducks and boats, it is not at all helpful to talk as though some repulsive force or pseudo-force is operating. A boat will not ride higher in the water if you paint it with never-wet, and the water is not repelling it. All “hyrophobic” means at the level of macroscopic surfaces like a boat’s hull, is that water does not “wet” it, i.e., stick to it, coat it in a thin film that does not easily run off, as water does tend to do with non-hydrophobic surfaces.
And, scr4, I am reasonably sure that there is no use or value in invoking a “hydrophobic force” to explain those insects that walk on water, either. I have always understood that phenomenon to be a result of water’s surface tension. The insect’s feet probably do have to be hydrophobic to prevent the water wetting them, i.e., sticking to them, but the water is not thereby repelling the feet (or vice-versa), just failing to be attracted to them.
Presumably you are joking, but just in case there is a real misunderstanding here, water is perfectly capable of being in contact with a hydrophobic surface, and if you put a boat, or anything else, with a hydrophobic coating into water, the water touches it, just like it touches anything else. The only difference is that water does not stick to hydrophobic surfaces, but does tend to stick to other ones.
Coating your boat in never-wet might make it capable of moving a tiny bit faster, as it will not experience so much drag from the water clinging to it. (I do not know if this really happens, or if the effect is more than negligible, but I think it is plausible that it might.) There could, that is, be an effect akin to lubrication, reducing the friction between boat and water. It will not, however, float any better (or worse).
So, yes, maybe, but probably not by very much.
By the way, I am baffled by why you would even imagine that the boat might sink.
Consider it the equivalent of a really good wax job on your car.
now I’m wondering if it would be of use on the planing surfaces of my scale hydroplanes…
hmm…
Unlikely. It’s not “like a wax job”. It would mostly like increase drag vs a fiberglass hull. The never-wet surface is not that smooth after application, and would be much less smooth than finished fiberglass.
See
Plus it’s very expensive and wears off quickly.
not necessarily. Hydroplanes “skim” across the surface of the water, and the fastest ones have “speed coatings” on the planing surfaces to reduce drag. Scroll down to “question 7” on this page. The black paint on the planing surfaces is very rough. I can’t find a cite other than I’ve seen this boat in person.
Yeah it was sort of an “airplane on a treadmill” scenario. I thought it was funny… 
A hydroplane plane coating is a precisely engineered surface designed to have specific surface tension properties at speed.
See http://www.wearloncorp.com/index.php/product/Wearlon_Super_F-1M
A never-wet coating is made up of a matrix of silica particles and is most closely analogous to hyper-fine sandpaper. I doubt it’s going to help drag or offer any benefit over a smooth fiberglass surface. It’s likely IMO to perform worse, plus you have the weight of the coating to contend with, plus the coating wears off relatively quickly which will further add to the rough uneven texture of the surface.