Golf ball boat - install a dimple plate?

Toma and Paul,

The only reason I could speak to the baseball thing is because it is in a brain section that is reserved for memory clarity. Probably due to self-delusional desires about being a major league catcher at one time in my life.

Everything else floats on a sea of luck.

It looks like I'm in good company... ;-)

Chris

 

Dimpled bottoms are available.

http://www.clacka.com/gulfStream.htm

Pericles

 

I have read this thread from the get-go. But only when you (Perry) posted that picture do I find words for what might be a practical problem (I really don't get all the mathematics involved): That bottom will be a b*tch to keep clean. I guess you could teflon coat it, though?

 

DB,

Drift boats are one way only, flowing downstream with the river current. Then, back on the trailer.

The text mentions a European car maker who has used dimples, Any ideas who?

Pericles

 

Somehow I missed that very good point :!:

Volkwagen? (for their Golf …)?

 

Found one (and not the bad joke about the Golf):

http://www.familycar.com/RoadTests/LexusLS430/Index.htm

However, it's a Lexus – not what I'd consider "european" …

Other than that I can only find people talking about BMW who used dimpled panels on the undercarriage, but they did so to reduce the noise.

 

Shark skin is dimpled.

 

Why would a drift boat be helped by any drag improvement? Sounds like the last reasonable application.

 

You're right, Tom. I get the feeling that it's more of a marketing tool than a functional improvement. The "tunnel" also strikes me the same way. Enhanced wetted surface to what end?

Now, if the frictional release actually makes the boat spin more easily, it may have limited value for the guy with the oars as he tries to point the dude with the rod in the right direction. The tunnel, on the other hand, would seem to actually slow the rotational movement. A zero sum game?

 

Pericles,
Thanks for that link...now I know I'm not completely irrational.

One would think those widespread dimples would cause suction - maybe to hold that boat in wild waters? I won't be adding them to my sculling shell anytime soon.

If the reduce air noise, I'm writing a letter to Ford. My Lincoln Blackwood's rear view mirrors create a lot of noise...better dimple 'em.

 

Dimples on a low speed application may reduce drag powered by oars. In a high speed application theres many reasons why that would not be desirable. The first one that comes to mind would be the effect of the turbulent water has on the drive. there would be to much aeration introduced to the propeller for efficient slip percentages. It is how ever desirable not to have a smooth bottom on the running surface were the hull planes at speeds that start to free the the hull approaching maximum velocity. Most Drag racers for instance will cross wet sand the aft portion of the hull with 600grit and there gear case also. This has been prov en to shave precious 100th of a sec in the liquid quarter. You will also never see a painted gear case in the pits they are all premiered only. Paint is to smooth. I guess its like what was mentioned above like shark skin. To much though like the size of the perforations or indents on a gulf ball would be to large.The theory is correct but the size comparison of a gulf ball isn't. Having said that all thing relative i suppose if you took the roughness of wet sanded 600 grit on a 19-21 ft boat and optimized that same scale relative pattern on say a 100fter than the perforations or sanded areas size would be more resemble that of a gulf ball? Perhaps the multiplied scale would only be like using 100 grit though also? I'm not doing the math Right now. You get my drift though. Speed has always been attributed in less wetted surface. How this is achieved is many different ways. Other than foils and hydro planes its buy less hull at the most aft portion of the hull. Any other ways and the aerodynamics take over from the hydrodynamics and you may end up with a wig. Don't get me wrong I'm not saying a new way to kite a hull isn't on the horizon but I see to many holes with the dimple theory the size of gulf ball indents is all.

 

You were probably looking at the page upside down!

But you would be right if you came here to OZ. We have to topspin our balls to keep them in the air.

MIK

 

you need random protrusions, not dimples

I remember reading an article in Nature magazine sometime around 1993 about researchers using surface treatments to enhance water flow. For their research, they used water flowing through a pipe, rather than a hull (pipe) flowing through water. What they found was that random protrusions in the pipe increased water flow something like 17% (or maybe it was 14%, I don't remember clearly as it's been ~14 years). Uniform protrusions did not have the same effect, maybe a few percent improvement.

The theory was this - as water flows along a smooth surface, the water that contacts the surface flows slightly slower due to friction. Meanwhile, the faster adjacent water is trying to hurry it along, and ends up "rolling" the slower water up into vortices (much like you might roll up a rug). These vortices (or "rolls") become larger and larger and finally break away from the near-surface area and introduce friction and turbulence to the overall water flow. However, by introducing small random protrusions, these vortices are broken up before they can "roll up" and become very large. The end result is a more laminar flow overall with less turbulence and greater hydrodynamic efficiency.

As far as automobiles trying the golf ball technology, Chrysler tried it on one of their NASCAR race cars back around '69 or '70 on a vehicle with a vinyl roof. However, the vinyl roof tore off of the car at race speeds before they could develop enough conclusive evidence to determine its efficacy. At the time, many of their innovations were being outlawed by race officials, so they likely didn't pursue it any further.

One thing the racers did learn was that their engine air intake scoops needed to be several inches above the hood to do any good as there was too much static air (or perhaps turbulence) right at the surface of the hood.

 

FYI:

Whale propeller thread:
http://www.boatdesign.net/forums/showthread.php?t=17382

Tail tube has fins inside to uncling air: The kulikovair website with detailed picture is down for an unknown amount of time.
http://www.aerospaceweb.org/question/helicopters/q0141.shtml