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Hull bottom dimpled like a golf ball for better MPG?
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Hull bottom dimpled like a golf ball for better MPG?
Yeah that sounds crazy. But its a known fact that golf balls are dimpled for longer flight. Something about the dimples allows the air to slip over the ball easier.
I just watched Myth Busters. The myth was would a dirty car get better milage than a clean car because of the golf ball effect. Well the dirty car got worse milage.
But when they put dimples in the car resembling a golf ball the car went from 26 MPG to 29 MPG at 65 MPH.
How about dimples on the hull bottom to achieve the same effect? I have heard that some boat racers sand the shine off the bottom to help break the boat from the water.
I think that this might work. Look at competitive swimming. You will see that there suites are made to mimic shark skin to give better hydrodynamics in the water thus crating more speed. I believe that there could be some benefit to having a dimpled bottom. Look at what steps do for fuel efficiency. Would love to see that myth busters.
I believe this is what a stepped hull does when it comes to speed. It provides an "air" pocket. As far as gas mileage who knows?
I know this as a fact though. WAXING the bottom of a boat with a traditional paste/thick liquid wax will slow a boat down significantly.
Alot of the high performance race boats and bass boats take light grade sand paper and hit the bottom of the boat before they go out. I believe this is the same idea as the gold ball effect.
Just my .02
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If this helps I'll add this comment. when tubing if you go outside the wake you really feel the added tension on the tube. Stay behind the boat and you just flow along. The disturbed water makes the tube glide. I'd say if you could add dimples it might work but you might loose stability at rest.
Yeah that sounds crazy. But its a known fact that golf balls are dimpled for longer flight. Something about the dimples allows the air to slip over the ball easier.
I just watched Myth Busters. The myth was would a dirty car get better milage than a clean car because of the golf ball effect. Well the dirty car got worse milage.
But when they put dimples in the car resembling a golf ball the car went from 26 MPG to 29 MPG at 65 MPH.
How about dimples on the hull bottom to achieve the same effect? I have heard that some boat racers sand the shine off the bottom to help break the boat from the water.
Any thoughts?
Chris, go over to the Scream and Fly board and see how many of those guy's sand the pads on the bottom of their boats...to break surface tension..
I've been saying this for years, bottom paint doesn't slow boats down, but I got tired of arguing with the experts of the no paint cult.. The rougher surface it creates causes bubbles for the boat the ride on.. Same theroy with a stepped hull except on a larger scale, pockets of air..
Dunk, I've felt the same way. Been a while since I had this in skool, but you get into "laminar" flow stuff, boundary layer conditions.
Barnacles are a good example. Half dozen barnacles on a hull won't make much difference, ONE barnacle on a propeller will kill speed. Why? The relative velocities of the two. Tip speed of a propeller can approach 150 mph.
Dunk, I've felt the same way. Been a while since I had this in skool, but you get into "laminar" flow stuff, boundary layer conditions.
Barnacles are a good example. Half dozen barnacles on a hull won't make much difference, ONE barnacle on a propeller will kill speed. Why? The relative velocities of the two. Tip speed of a propeller can approach 150 mph.
No doubt that bottom paint doesnt' slow the boat down, I have first hand knoledge with this.
When I got my boat the bottom was unpainted. I bottom painted it and saw absolutly no loss in speed or performance. Its a myth for sure. And there is no doubt the bottom paint makes the bottom rougher.
I've posted this before and I guess I'll try it one more time. The purpose of the steps is to break up laminar flow. The rough surface you guys are talking about does pretty much the same thing on a smaller scale. What I remember from fluid dynamics class (almost 20 years ago) is that in a viscous fluid like water, laminar flow is the enemy for something like a hi speed boat. Laminar flow creates more drag / friction between the hull and the water. What you want is turbulent flow. Breaks the surface tension, etc. Really has nothing to with air bubbles. The effect would be the same w/o any air involved. Check out the surface of a submarine or even as someone else posted, a shark's skin. Think the shark carries air bubbles around with it so it can swim faster?
I had this conversation with a mate 10 years ago and my answer then and still is now that a hull with a golf ball dimple pattern would create drag due to the fact that each dimple would need to displace more water as opposed to a flat surface.
A golf ball needs the dimple pattern to stay airborn longer because once the ball is struck,there is no further propulsion and gravity will inevitibly play it's part.
On the other hand,a boat's hull has continuous propulsion and the smoother the surface it has,the less resistance it will have moving through the water.
Some years back there was an attempt made by a company to market an adhesive film that mimicked shark skin for the bottom of racing sailboats. I seem to recall it might have been used on an America's Cup trial boat but I'm not positive. I don't remember the details but I'm guessing it didn't work or it would be on those boats today.
With the amount of money these sailboat racers spend on competitions like America's Cup you can bet they try anything and everything to gain a fraction of a knot over their fellow racers.
Disclaimer: If you see emoticons, that means the above is written in jest. It is for entertainment purposes only. It is not meant to represent any actual persons, places, or things. It is the opinion of the poster that it is funny. Your opinion may vary. No animals were harmed in the typing of this post but a few egos may have been bruised.
On the other hand,a boat's hull has continuous propulsion and the smoother the surface it has,the less resistance it will have moving through the water.
Yes, you would think that, but it's totally wrong. The smoother the surface of a hull, the more laminar the flow around it will be and the more drag you will create. I remember watching films of laminar vs. trubulent flows in class. At the time, computers didn't have near enough juice to caclulate the flow patterns of turbulent flow and so no one was able to accurately predict results. I suspect the same is true today. Sort of like trying to calcuate the effects of a nuclear explosion on a sub-atomic level...out of reach of even the biggest super computers. What they did know without a doubt, from experimentation, was that laminar flow creates more drag than turbulent flow.
Engineers have rules of thumb that they use in applications like this and the rest is basically accumulated experience and poke and hope.
Some years back there was an attempt made by a company to market an adhesive film that mimicked shark skin for the bottom of racing sailboats. I seem to recall it might have been used on an America's Cup trial boat but I'm not positive. I don't remember the details but I'm guessing it didn't work or it would be on those boats today.
With the amount of money these sailboat racers spend on competitions like America's Cup you can bet they try anything and everything to gain a fraction of a knot over their fellow racers.
Link is Shark skin magnified 70 times.Pretty interesting.
Looks like it would be difficult to replicate.
However they are directional.
Dimples on a golf ball stir the boundary layer,ie area just above the surface.
The golf ball has spin when hit by a club.
Laces on a baseball have a similar effect.
If it doesn't spin then you get a knuckle ball which is slower AND no gyro stabilizing effect.
I saw the Mythbuster TV program last night also.
I would prefer multiple tests and of longer duration.
The F4C at the AF museum was Robin Olds plane in Vietnam.
It went to Spain,Homestead AFB,finally Kelly ANG in SAT,TX.
One day a hail storm dented ALL the F4s on the ramp.I saw 829 at the AF museum all dimpled before it was smoothed with BONDO and repainted.It had lots of dimples of different size and depth. http://nothingtoxic.blogspot.com/200...ation-x70.html
also read about high speed Russian torpedo.Pretty interesting
My experience is that when the water is smooth my boat is slower than when it is a little choppy. Less drag? As far as stepped hulls, I think the problem you run into is stability in a turn. The stern tends to want to spin out, because of the lack of directional friction surfaces (pad hull), and less contact with the water. But I'm no marine engineer or designer. So this is just opinion.
dimples would create a suction or low pressure effect slowing the boat down, they may work if they could be vented but how would you do that without a hole in the middle of the dimple. With out the hole the dimples would act like suction cups .
There are several other dry film lubricants that work.
What I was referring to is an actual plastic film adhesively bonded to the hull bottom, similar in concept to the advertising wraps that they put on boat hullsides. It had a surface treatment that supposedly made it similar in profile to shark skin (or at least that was the promotional jargon).
Disclaimer: If you see emoticons, that means the above is written in jest. It is for entertainment purposes only. It is not meant to represent any actual persons, places, or things. It is the opinion of the poster that it is funny. Your opinion may vary. No animals were harmed in the typing of this post but a few egos may have been bruised.
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Hull bottom dimpled like a golf ball for better MPG? 
