Teardrop Ratios - above deck

There are several practical reasons you don't find tear drop shaped boats. The first one to come to mind is a domed surface is hard to stand on (This kind of makes it hard to move around when you need to dock a boat). Another thing that comes to mind is a boat travels across the surface of the water and it is often not smooth thus boats need a pointy prow to cut through waves so that the ride doesn't rattle (or knock) your teeth out.

Also since most boats don't go above 40mph drag induced from the water dwarfs any drag from aero dynamics.

Edit : If you think you can design a better race boat than the current designers go ahead and do it. I'm sure they need a good laugh.

 

As you mainly talk about the fastest types of boats: They hardly touch the water
Most literature you find, will deal with displacing conditions or planing hulls.
As a starter for your hydrodynamic reading I would suggest 'Principles of Yacht design' Larrson/Eliasson. Much of the book deals with sailing and other stuff, though.

 

Growing up next to one of the fastest boat racing circuits in the world I have learned one thing about boat aerodynamics. The aerodynamics of a boat are primarily needed to be such to keep the boat to impact the water in a way to minimize water drag. Aero drag is secondary to this. When a boat hits the water it tends to get pitched up, down, sideways, or in a roll. Excess aero drag is used to keep the boat pointing the right direction.

 

A brief article for your reference.

By Doug Ford
Reprinted from h1unlimited.com.
The Aerodynamics of Unlimited Hydroplanes
http://thunderboats.ning.com/profiles/blogs/the-aerodynamics-of-unlimited
Posted by Dale Fugier on January 12, 2011 at 9:49pm

 

kach22i,

Funny how you cite from an article that discusses everything about aerodynamics on boats being used for everything but drag reduction.

Also note that the pictured modeled hull (the Miss Budweiser T-4) was one that was unsuccessful. It was a hull that they focused on Aerodynamics to fly the boat around the course. They spent a year trying to dial it in and it only raced once before they gave up on it. It was then sold and totally rebuilt as a single wing boat.

 

Much of the aerodynamics on racing cars is to force them to the ground on corners where extra power is available and higher than 1 G cornering is required .

 

It's really not all that funny, just a reflection of how little is out there on the topic as I'm attempting to define it.

I'm sure it has to do with all the reasons already noted by forum members, with hull drag being far more important.

Perhaps research in the direction of sailboats which are forced to be more economical about energy use would be a good idea.

I assume any sailboat which is fast has an airfoil shaped mast at a minimum.

http://www.pdracer.com/mast/hollow-mast/


http://www.answers.com/topic/masts

 

Perhaps the premise behind the question as you are attempting to define it is not entirely valid.

• There have been considerable advances in understanding bluff body aerodynamics and drag reduction since the 1930's.
• "Optimum" depends on the requirements and circumstances. The claimed "optimum" shapes are not optimum for every set of requirements and circumstances.
• Aerodynamics is considerably more complicated than the application of a "template".

 

Excellent, and this was the basis for a past dispute in another forum with the head guru when a 3D teardrop study shape (based on blimps) he was promoting was reduced to a 2D template for boxes, I mean "Bluff Bodies".

It cause me some grief, but I stopped bashing my head against that wall a while ago - and I'm feeling much better now.

Can we settle one thing while this thread is still active?

Is the ground plane for a car going to be anything like the water surface plane for boats in regards to influencing the length ratio of a teardrop cockpit placed above deck because of an "air pressure wave"?

Two-Part bodies or "composite bodies' of Jaray/Hucho would in my mind be similar to a boat's teardrop cockpit placed above deck.

 

The surface of the water a boat is traveling through has a similar effect on the flow of air around the boat as the effect the ground/road surface has on the air flow around a car.

But it is not because of an "air pressure wave".

Let's start with the air flow around a car. If the car is somehow moving thought the air a considerable height above the ground then the air can flow in all directions around the car. But if the car is on the ground then the air cannot flow through the ground so the air flow is affected. Close to the ground the flow will be close to tangent to the ground. This will affect the air flow around the car. More air will have to flow around the sides of the car and over the top of the car.

Now consider a boat moving through the water. The surface of the water will have waves and not be flat like the ground. The size and shape of the waves will depend on the speed, size and shape of the boat. (The water surface may also have waves due to ambient conditions.) The air cannot flow through the water. Close to the water the flow will be tangent to the surface of the water. This will affect the air flow around the boat similar to the effect the ground has on the air flow around a car.

 

Sounds like the "head guru" on that forum should be demoted.

 

An "airfoil shaped" mast is not the optimum shape if the mas does not rotate.

 

I would not like the idea of reefing the main sail while I stand on an aerodynamic deck with low drag surface.
For safety and practical reasons, I believe that - on a sail boat - aerodynamic details can only be applied here and there, but not throughout.

 

Thank you for talking me though the air flow progression around a moving body which is in close proximity to the a ground/water plane.

I'm a visual person with an imagination, and right now I'm imagining the air which would normally be going under a "free air" moving body (aircraft/blimp) but cannot or is limited in car & boat examples bouncing up in ground effect and being squished - or pressurized. This is for not only the direct undersides or the car/boat but at the sides, perhaps to be determined from the top of the roof leading as a 45 degree vector down to the ground/water plane.

I made the above all up in my head, but like I said I can see how adjacent surfaces could effect energy distribution. Similar to the swimmer unlucky enough to be slated for the far lane against the pool side. His/her time will not be as fast as the middle lane person because of reflection of energy or it it pressure?

EDIT: I found this post in another forum on pool lanes, seems like all the focus in on the water, no consideration for air (air is a fluid as in fluid dynamics, right?).

http://www.twopeasinabucket.com/mb.asp?cmd=display&thread_id=2623799

 

Check out this excellent book, The Leading Edge, by Goro Tamai, it's a great read.

http://www.amazon.com/The-Leading-Edge-Engineering-Performance/dp/0837608600