Project Slipster: Streamlining the Kawasaki Ninja 250 (WIP Thread)

[3-Wheeler]

Hi Brian,

I can not endorse the full coverage you are proposing for several reasons:

This has already been done before, with dire consequences during the Craig Vetter High Mileage contest in 1980 or so.

Take a look at one of the most respected entries in the contest, by Honda... It was a beautiful design, both conceptually and through eloquent construction...



....CRASH!....

Now take a look at the damage that ensued, after stunt rider Debby Evans had control of the bike taken away by strong side winds... A very skilled rider could not cope with the sudden side forces.



Please note that the Honda entry has less side area than your taller design. Can you imagine riding on very windy day, with sustained gusts at 40 mph, and raining? I have had this happen to on occasion after putting 105,000 miles on my bike. Those conditions literally take your breath away as one fights for every inch of traction the tires will give!!

You've seen my small *full coverage* fairing, and it was a handful on those gusty days. Imagine how much more so with four times the side surface area of the proposed design!!

A much more safe design compromise would be to copy the Rifle fairing with your creative flair added...

This design offers way less surface area to side winds, and more easily decouples air attachment to the upper body, by sitting up of all things, when strong side winds happen.

Yes, frontal coverage is less with this design, but decidedly safer for you.



I'm not trying to burst your enthusiasm, but simply keeping you alive to ride for many more years. Applying the wisdom of those that have come before us, certainly helps as well, as there are many lessens to gained by reading these old articles.

Jim.

[thatguitarguy]

Many recumbent bicyclists use Lycra bodysock fairings, that are quickly and easily fully removable.



You could build smaller hard fairings, and then add a scaffold in order to stretch cloth between the front and rear fairings, and even an extended tail at the rear when calm conditions warrant, or quickly remove and store the cloth when it gets windy.

Stay safe!

[dcb]

a rudder on the back and/or front to cancel out the torque moment caused by the side wind/camber effect might help too. getting a computer to control it based on wind speed/direction + vehicle speed might not be too challenging.

[theycallmeebryan]

Thanks for that post Jim. I appreciate the constructive criticism, thats the whole point of this thread! I'd like to get most of the guess work out of the way before i start getting hands on with the project.

The user "Cd" here had mentioned trying to use window screens on the sides as a way to buffet some of the side winds. The idea is that a screen may be solid enough where air will flow across it, yet porous enough that side winds penetrate through.

One of my goals with this project is to increase protection from the outside elements. Also, in my main thread i had talked about back pain i was getting while sitting in a crouched position for extended trips. I want to try to avoid having to crouch down, and in doing so i was still able to maintain over 90mpg with the bike, even given the increased frontal area and the addition of a taller windscreen.

At bare minimum i would say that ill still have a front fairing and a rear tail, but perhaps have a gap between the two, and figure out a way to trick the airflow into thinking there's a solid surface there and to stay attached. I've tried to test a few different designs using flowillustrator, but everything i have tried produces a lot of turbulence between the two fairings.

Can anyone provide information on aerodynamically "jumping" air from one object to another across a gap?

[solarguy]

Sorry, has anyone discussed mounting and dismounting? What about vertical stability while stopped at stop lights?

I saw a motorcycle streamliner in Austin Texas back in 1985 or so. Completely enclosed. They dealt with the stop/start/vertical issue by having little outrigger wheels that deployed as you stopped, I think.

Very interesting,

Please carry on,

troy

[dcb]

Originally Posted by dcb

a rudder on the back and/or front to cancel out the torque moment caused by the side wind/camber effect might help too. getting a computer to control it based on wind speed/direction + vehicle speed might not be too challenging.

edit, oops, not on the front. that won't work as it would have to move into the direction of the wind and probably add to the effective side camber in the process.

[botsapper]

Home Page

Not fully enclosed but a safer design compromise. You could still have upright riding, stoplight stability and ease of mounting & dismounting. Supposed been up to 150 MPH. The minimal side surfaces lessens dangerous side buffeting. Your design criteria has more engineering challenges but not impossible. I'm working on some solutions.

[Christ]

Regarding "Jumping the air" from one fairing to another, Look at the wheel fenders of very aero cars. You want the rear surface slightly thinner than the front.

You can find the "accurate" amount to thin the rear fairing under normal conditions by making a curve with a 12* arc and taping the edge of it to your front fairing and matching the leading edge of your rear fairing to the arc at the point you want it to begin on the bike.

If that's not clear, let me know and I'll try to make it more understandable.

[Cd]

It might be wise to have the front portion of the bike shroud pivot or slide forward.
It could also be made to break away and have foam padding and smooth sides around the edges.

In case you ever had to slam on the brakes or were involved in an accident, you would be safely ejected from the bike ( .... only to slam head first into the road. )

I was happy to see that Craig Vetter joined the conversation. I have a lot of respect for him.
I must admit though that I shudder when I look at his bike shroud and see all those sharp edges, rigid frame pieces, and pop rivets that would slice you to pieces in an accident.

The idea of having the shroud slide forward for entry would not only help in an accident, but would also be a very clever way of entry ( as pointed out by other folks here .)

Getting back to the topic of cross winds, worse case scenario, you could have outriggers mounted on the bike that might help.

[theycallmeebryan]

Originally Posted by Christ

Regarding "Jumping the air" from one fairing to another, Look at the wheel fenders of very aero cars. You want the rear surface slightly thinner than the front.

You can find the "accurate" amount to thin the rear fairing under normal conditions by making a curve with a 12* arc and taping the edge of it to your front fairing and matching the leading edge of your rear fairing to the arc at the point you want it to begin on the bike.

If that's not clear, let me know and I'll try to make it more understandable.

Are you talking about something like this?



Ran it through flowillustrator:
http://www.youtube.com/v/xZT511YgBnQ&hl=en_US&fs=1&