Rustoleum Neverwet

Just saw an ad for this stuff, and wondered how it would do on a boat's hull. Would it help the boat's hydrodynamics, creating less drag, thereby better top speed and fuel efficiency? Thoughts?

Re: Rustoleum Neverwet

no not at all... slick hulls are SLOW hulls

Re: Rustoleum Neverwet

smokeonthewater said:

no not at all... slick hulls are SLOW hulls

Click to expand...

What? lol
How do you mean? I thought less drag and lower coefficients of friction were the key to a faster/more efficient boat?

(slick paint vs rough truckbed liner)

Re: Rustoleum Neverwet

So... smokeonthewater...you sayin I should keep those barnacles on the bottom side?

Re: Rustoleum Neverwet

this has been covered soooooooooo many times... save the wisecracks and do a search

a smooth bottom is obviously good but porosity holds air bubbles and air is MUCH slicker than any wax... dull smooth sanded bottoms are faster than super slick waxed bottoms

Re: Rustoleum Neverwet

smokeonthewater said:

this has been covered soooooooooo many times... save the wisecracks and do a search

a smooth bottom is obviously good but porosity holds air bubbles and air is MUCH slicker than any wax... dull smooth sanded bottoms are faster than super slick waxed bottoms

Click to expand...

Do you have any good links to read? Just trying to understand what you're talking about... my first thought is the physics of a mass moving in water. I mean, boats don't depend on air underneath to move? (I'm feeling kinda stupid right now lol)

I mean, whether it's air or water, friction is present. And there are paints that are geared towards lower coefficients of friction....

Re: Rustoleum Neverwet

A planning type hull will ALWAYS entrain some air underneath it. In fact, many newer hull designs incorporate "slots" and "steps to help entrain air and decrease the wetted surface area.

The dynamics are similar to airplane wings where laminar flow sticks to the surface of the wing, creating drag, properly managed turbulence decreases drag without affecting lift.

SO when you make the hull slicker, it actually "sticks" into the water better, increasing drag and decreasing speed. Remember, this is a surface already in the water, and not shedding it like the shoe in the ad.

Re: Rustoleum Neverwet

Ahh right, but since the boat is in the water (medium) and comes across air (as you move), doesn't the slicker bottom do better than a rough bottom (that would catch air) because the air wants to escape up?

I mean, I'm seeing it this way, perhaps I should read up more on it..

As you pass through water, air gets trapped underneath, the faster you go the higher percentage of air underneath. But because air wants to escape up out of water, you're constantly cycling a certain percentage of air under the hull. (slower moving= less air and more contact with water, faster moving= less contact with water, more contact with air)

But* no matter what medium you're travelling through (and never 100% air) it would come down to the friction coefficient of the paint? (that's why there's no devices to add air in front of the engine, to reduce it's drag? hehe)
Air < water, as far as friction is concerned, BUT a rough bottom boat coating will never be less than a slick coating in the areas of friction and drag...

I'm thinking of these principles without any sort of bubbler or air entrapment, think of a plain old V hull..

I know they apply principles of a bubbler to torpedos and such, but I'm curious as far as averages go.
Makes me wonder why companies even bother making hull coatings that are lower coefficients of friction if the way to go was something dull and rough (to catch air)

Under these pretenses, an old boat with a rough paint job (even broken peeling paint to trap bubbles) would preform better than a new paint job?

Re: Rustoleum Neverwet

Since smoke is a cranky pants.....

For boats, unlike aircraft, we are talking about incompressible flows-hydrodynamics. The boundary layer development, breakdown, and separation are critical because the high viscosity of water produces high shear stress. A consequence of high viscosity is called the slip stream effect. The simple answer is that slicker does not mean faster.

Re: Rustoleum Neverwet

I guess I should ask then, how does one decide on a hull coating? (if the desire is for faster travel)

Re: Rustoleum Neverwet

The point of it all is that you can paint your hull with a good bottom paint and be done with it. Regardless of what you do, you are not going to see a substantial difference in speed.

Re: Rustoleum Neverwet

What about the paint......anyone used it?

Re: Rustoleum Neverwet

I'm curious about the paint too.

As a side note, I found this, pretty decent debate about which circumstances yield different results.
Waxing the bottom of boat?

I agree Idonthaveaname, I'm sure it's a very minimal speed increase/decrease, I just love science though
I wonder though, why hasn't anyone replaced gel coat with something else, or why isn't there a boat manufacturer that adds dimples to the hull paint job...

Re: Rustoleum Neverwet

kungpaoshizi said:

I'm curious about the paint too.

As a side note, I found this, pretty decent debate about which circumstances yield different results.
Waxing the bottom of boat?

I agree Idonthaveaname, I'm sure it's a very minimal speed increase/decrease, I just love science though
I wonder though, why hasn't anyone replaced gel coat with something else, or why isn't there a boat manufacturer that adds dimples to the hull paint job...

Click to expand...

You answer your own question...."it's a very minimal speed increase/decrease."

Like science? Slippery Sailboats

Re: Rustoleum Neverwet

idonthaveaname said:

You answer your own question...."it's a very minimal speed increase/decrease."

Like science? Slippery Sailboats

Click to expand...

LOL is it bad I visualized that experiment before you linked that... heh

I think the real answer to the question though is to strap dolphins to the bottom of the boat :|

Re: Rustoleum Neverwet

Hmmmm....So if water doesn't stick to the paint wouldn't more air be trapped between the water and boat making it faster?

Re: Rustoleum Neverwet

Though the water doesn't stick to the paint, think of 2 vinyl tiles. One is water, one is the boat. Now add gouges to one tile.

2 surfaces rubbing against each other that are both completely flat, friction increases. (before gouges)
2 surfaces rubbing against each other and one has gouges, less molecules moving against each other because of the gouges, friction decreases. (air is less dense than water, water less dense than solid, solid is most dense)

The golf ball example is a good one too(Waxing the bottom of boat?)

Re: Rustoleum Neverwet

cranky pants?

no just not into answering the same question in great detail over and over again IF I can get someone to search...

The problem with the slick hull has nothing to do with water sticking but rather it has to do with air NOT "sticking" with a rough hull the air TINY bubbles remain on the bottom and keep the water from sticking to the hull with surface tension...

The high tech bottom treatment for fast boats absolutely DOES exist..... It's called sand paper

Re: Rustoleum Neverwet

"just not into answering the same question in great detail over and over again"

Well...that's just part of being here. The same questions are asked very often in that most of these type questions are asked by a newbie; what kind of wood, epoxy or resin, what is cabosil, what is PB...... The list goes on and on and on. One really big challenge is the "search" function on this site is not so good. I design search capabilities for technical websites and this one leaves a lot to be desired-not intuitive. I am savvy at searching and have tried searching here gaining little in results. That said, sanding lightly works but the end answer is that it doesn't really matter unless you are in a challenge with the America's Cup.

I like the golf ball dimple answer..that's a good one and maybe why me leaving the barnacles could work. ;-)

Re: Rustoleum Neverwet

so maybe you could volunteer to improve the search feature


I answered his question and in fact until it became a debate I was the only one to answer.....

btw I never use an onsite search ... I use google

since you are "search savvy" you didn't need to ask about barnacles did ya? lol