Golf ball boat - install a dimple plate?

Ok...I just have to ask:

Granted - a dimpled golf ball flies 30% farther than a smooth golf ball as the dimples create lift.

Then why doesn't the bottom of a big, wide and flat boat get some lift and relief of suction from dimples as well? Perhaps reverse dimples (pimples) would be better as dimples may cause more suction....like mini cupped hulls.

I Googled and cannot find anything about anyone trying a dimpled (or pimpled) area near the transom on a boat hull.

Tony in Sw FL

(sorry...have free time today because the stock market's up SO much)

 

JuiceMan...

Take a look at the relative, speed through the air, of the golf ball and the relative, speed through the water, of a given hull design and make your relevant relationship models.

That should tell you the answer.

 

Considering...

different media's, air is compressable and water is not.

The golf ball has dimples all round in all directions, the boat will have them on one side only - the under side.

The golf ball might travel slightly (but only slightly) faster than a boat.

You cannot tee a boat, but - a boat with dimples can be a handicap.

The golf ball has a shape that drags wind like a commet behind it. The boat has a sharp front for cutting throught the water. If you swap these two features, you'll have a golf ball you have to play in the water with with the sharp end towards the hole or in this case the well, and a boat that has to fly to work like the space shuttle does. Or similar, but you'll have to tack really fast.

The golf ball rotates when it is creating the lift. The only time a boat turns is when the beer is up and you have to head for the fridge on the land. A boat rotates after the third trip to the fridge when a gust of wind (could be from the golf ball) gets you between a broad reach and a close reach.

One is meant for playing golf, the other for FISHING

 

A golf ball's dimples don't create lift, but do maintain a better laminar flow around the ball so it's resistance is less. In fact a golf ball with bumps, (I was a friend of the son, who's father invented it, working at Dupont) flies better still, but the PGA banned them promptly, after they realized all golf courses would be too short with the new ball.

Bumps and dimples have been tried, as have thousands of holes which allowed air to fill the low pressure areas (try and keep all these clean and open in a race). Vortice generators and all sorts of things (like soap and oil injection) have been attempted, most with limited success (though oil injection works very well).

As an object subjected to flow, spherical things aren't particularly good (they suck actually), regardless of the viscosity in the flow medium.

You can increase the laminar flow qualities with some well designed surface protrusions, but what works good at some S/L ratios may be the feature that hurts you at other S/L ratios. If your design will operate within a narrow S/L range, then putting some bumps on the bottom may be worth the trouble. If you expect varying S/L ratios during general use, then you should consider suffering along with just a smooth bottom or possibly hanging an oil filled bag with a slow leak off your bow, so you can "slide" along a wee bit better.

 

Someone tried that recently, using an integral tank in the bow in lieu of a hanging bag. Couldn't control the leakage rate, though.

 

The hole you see there is where you park boats in.

You could have something like a shark skin effect to slightly (only maybe) increase efficiency. One of those back to front things again. You need the boat to catch the sharks for their skin but you cannot finish the boat since you do not have the shark skins.

It's like the skippers license thing, just as back to dront. You cannot sail if you do not have a skippers license. You cannot get a skippers license if you do not sail.

 

I'm grateful for all of your comments. The golf ball is spinning and the dimples creates a vacuum above the ball for lift and less drag. Doh! I should have figured that one on my own. Instead I've wondered about it for years. (I warned you...we financial minds are usually challenged). I guess a spherical shaped boat that spins backwards is out of the question?!

I saw something online last year where they put crystal shaped thingys in the gelcoat and brushed them all the same direction to act like sharkskin. I haven't heard another word about it...so, apparently the results weren't Earth shattering.

Tony in Sw FL

 

PAR set things straight about the dimples on golf balls. They delay the onset of flow separation, making laminar flow last longer. Injecting some materials into the stream is effective though and is deemed illegal by the yachting authorities while painting the boat with the miracle stuff of your choice is not.

Electric power plants and other units with closed loop water systems often treat the water with long chain polymers to reduce friction in the boundary layer and increase efficiency. Britain Chance did build a sailboat that had a series of small holes near the bow where a long chain polymer was injected into the flow. It was promptly outlawed.

If I'm looking at it properly, a backwards spinning golf ball creates down force not lift.

 

Hmmm. You'd think someone would have brought wet exhaust to the front of the hull to ad lubrication from, for example, a filthy pair of Detroit Diesels.

In any case, I'm going to figure a simple and effective way to add air under this wide hull...eventually:
http://www.boatdesign.net/gallery/showgallery.php/cat/500/ppuser/22690

 

Just to clear up why the dimples work on a golf ball, and not on bigger slower things like boats....

See the attached image. This is a classic system found in all fluid mechanics texts, and one that an amazing number of students fail on their Fluids II midterms.

The dimples induce a slight bit of turbulence in the boundary layer- the very thin film of air that is right against the surface of the object. With a laminar boundary layer, the flow would travel in smooth layers, and would separate from the ball very close to the leading edge in order to maintain these smooth layers- leaving a huge, turbulent wake behind. A slight bit of turbulence in the boundary layer delays the separation, allowing the flow to remain in relatively smooth contact with the ball until somewhere along its trailing face- thus, when the flow does break from the ball, the turbulent wake is much smaller.

It's not a complicated system, but it is important to distinguish between turbulence in the boundary layer and turbulence in the wake. A slight increase in the former, for a golf ball, greatly reduces the energy dissipated in the latter.

The spin on a golf ball is not intended for reducing drag. What it does is to induce a slight circulation around the ball, which results in a net upward force (a lift) on the ball. This effect is not nearly as intuitive as it sounds and some reading on potential flow theory is required to understand why it works. But in the end, the lift comes at the expense of the rotational inertia of the ball, and so while the spin slows down in flight, it spends more time in the air and so goes farther.

Now to a boat. Unless you're sailing a harbour tug, you do not have separated flow on the underside of the boat to begin with. And you're not in the same Reynolds number regime as a golf ball. So the increase in skin friction you get by forcing a turbulent boundary layer is not offset by a decrease in the energy dissipated in a separated wake, because there is no separated wake to begin with.

Predatory sharks, AC yachts and other high-tech marine systems sometimes use tiny ridges and other structures on the skin of the animal/boat. Exactly how they work is the subject of a lot of research right now; essentially, they are manipulating the boundary layer to provide the right combination of laminar and turbulent properties for the pressure gradient in a particular area. Simply slapping the stuff on has no benefit without knowing what it's doing to the boundary layer in which area.

 

You are right, you were looking at it backwards.

Observe how a pitcher in baseball gets the ball to curve or sink. The rotation applied to the ball from the hand release and wrist snap, imparts a powerful forward rotation from the top of the ball rolling downward over the front of the ball. The ball, literally claws its way in a downward arc much more drastically than a simple, decaying parabola of arc.

A ball given the opposite rotation, such as a really hard fastball with lots of reverse spin, is called a riser. Golf balls hit with lots of backspin climb higher and also stop quicker before rolling backwards, hopefully on the green.

 

There has been some thought on entrained air benefits on Viking long boats. In more modern times, there has been fairly extensive study on the effect by a Danish boat designer, who's name escapes me now, in which he deliberately formed air entrainment channels in his hull surfaces in order to facilitate the same effect he was seeing in the Viking boats.

I saw this guys work on the Internet and was truly interested in his work. I have since saved it to my computer in such a fashion that I can't find it anymore (sunspots, or maybe brain spots) His boats were in the Faering size of things and looked to be working quite well.

If anyone has a memory jog from this suggestion, I'd really like to have a current URL for the design work of this gentleman.

Chris

 

As the price of fuel rises the more these things (dimples and bumps) will be revisited.

Maybe there will some progress made on the topic in the near future.

 

What I was looking at improperly was which direction backwards spin was.

http://en.wikipedia.org/wiki/Magnus_effect

I plead dislexic observation.

 

Don't feel bad Tom, I suffer from a very mild dyslexia sometimes, usually when the one that must be obeyed asks me to do something. I pray to Dog every night, that it will go away.