Frontal Area vs Frontal Curve Smoothness
 

Just a general question about aerodynamics. Here, im referring to the general teardrop shape.

Is smaller frontal area more important than keeping the front curve smooth over the guts of the vehicle?

I am working on a new fairing design for my kawasaki ninja 250. I am wondering if it would be more beneficial to keep frontal area small, or should the fairing extend out past the handlebars? It seems as though a full exterior fairing is what most people aim for (looking at HPV designs).

Furthermore, is there some sort of equation or rule for figuring out the best front curve angle (length vs width)? Is it better to have a perfect semicircular front (from a top down view)

Curvature... There is - and it's a ratio of curvature/width (or something like that).... Alas, I don't have it available at the moment but it's in Hucho's book on road vehicle aerodynamics. Having more curvature beyond this critical ratio has diminishing returns.

The question of more FA versus not covering handlebars is an exercise in optimization. You want to minimize FA, but protrusions (handlebars) are never a good thing...

You are only going to be able to guess at which is better. If the extended fairing is aerodynamic enough, it can reduce drag even if it increases total frontal area, but without a windtunnel or CFG there is no way to tell for sure whether you've achieved this.

Remember, the frontal area of the fairing itself is not important; the amount of frontal area the fairing adds to the whole bike is what you have to consider. So if the fairing covers the handlebars (and where your arms are), but just barely so as not to add much FA, and the fairing is quite a bit more aerodynamic than the handlebars—which it should be if designed properly, it will likely reduce drag.

I'm not sure what you are asking, but it is OK to have a fairly sharp transition between front and side, rather than one continuous frontal curve. As long as you are pushing into the air, it is inclined to behave.

The big problems are at the rear anyway.

That is kind of moot, unless he makes some kind of fiberglass monstrosity that conforms to the back of his body and forms a boattail.
http://www.tonyfoale.com/Articles/Ae...s/AeroOpen.jpg



The practical place to aeromod on a bike would be the front end. Think of it like a kamm back to suppress your "it would be better going backwards" reflex

It's not moot at all.

He can make the slickest forward fairing ever and the aero will still suck.

I understand that the tail is very important.... that is not the question i asked.... this topic is strictly based on front end design. My question was also pretty straight forward. If you notice, i said "Here, im referring to the general teardrop shape."

A bike with a faired front end is going to be better than one without. Just because you're preoccupied with the idea of rear end aerodynamics being the most important doesn't mean that the front doesn't matter. Like I said, think of it as a kamm back

Tail Boxes Can be beautiful - and not monstrous or fiberglass... Big benefit just requires more work and thought :)

http://www.wisil.recumbents.com/wisi...p/IMG_1245.JPG

http://www.wisil.recumbents.com/wisi...an2004_vk2.jpg

I do agree with lee... There's a reason aero textbooks spend more time on the back end. Here's a cool picture I took awhile back showing these awesome rings in the water tunnel.

http://www.instructables.com/files/o...AEETVPLPW9.jpg

But it doesn't change my original answer - it's an exercise in optimization :thumbup:

A faired bike is NOT necessarily more aero! I have a Cycle World article with wind tunnel test data from several styles of bikes. What do you have?

AND it's NOT comparable to a Kamm back. Think about what makes a Kamm back a Kamm back and get back to us.

Front and back are both important.

I won't venture to say what the relative proportions are, but a brief perusal of Hoerner's Fluid Dynamic Drag compilation of aero studies makes me think the front is more critical.

Then, there's always the bugbear of what to do with the rider's feet at a stoplight, etc..

I have pictures of those old salt flat bikes with front fairings. Of course a bike can be low-drag enough in the front that adding a fairing and increasing frontal area increases drag. But what does that have to do with what you said about the big problems being at the rear?

What makes a kamm back a kamm back is the rearward decrease in cross section that is truncated... Just like some front end fairings.
My point is that a kamm backed vehicle doesn't have a boat tail like your "teardrops" but a void space in the back, and an aerodynamic front because front end aero matters.


Should this bike do away with the front fairing? Notice the tapered flanks BTW
http://www.airtech-streamlining.com/...bladustbin.jpg

Now THAT's a fairing! :thumbup:

Is this the kind of fairing ANYONE puts on anything on the street? Was OP gonna do something like this? I wonder if x-wind issues kept it from acceptance?

99.9% of fairings don't taper in before cutting off, thus not qualifying for "Kamm" status.

Just think if that Honda had a nice tail section too.

The Britten racer had kind of a "non-fairing" design. Cycle World in '92 had an article describing the aero theory of it. Supposedly it was the best around. Didn't necessarily go for ultimate smoothness, but frontal area reduction.

KIWI WONDERBIKE

http://i146.photobucket.com/albums/r...n_V1000_02.jpg

try this link

Tony Foale Designs, article on motorcycle aerodynamics.

Hi Frank,

The Britten has so many innovations -- a key element of the aerodynamics is the way the cooling system is set up! Can you spot the water cooling radiator? :p

Here are two more photos with visual clues:

http://www.britten.co.nz/photos/images/sot2003b.jpg
http://www.britten.co.nz/photos/images/sot2003a.jpg

Hint: the intake is in the nose, and the exhaust is in the "stinger"!

Whats wrong with putting a fairing like that on a daily driven street bike? :confused:

The design im going for is going to look something like this. Im sure many of you have seen his design before. Its a Ninja 250 converted to electric.
http://www.blogcdn.com/www.engadget....motorcycle.jpg

However, im not sure how much more drag will be created by having a fairing designed for up-right seating. How much less drag would this fairing design have, if you guys had to make an educated guess?
http://craigvetter.com/images/470MPG...-perethian.jpg

I would say that 75% of my riding on my Ninja 250 is in a crouched/layed down position, and i dont really have a problem with it.