Streamlining CBR600 for Bonneville & Vetter Challenge

[redyaris]

I have a 1988 Honda CBR 600 that had a damaged fairing that needs replacement. So what I plan to do is build a dustbin type fairing with cargo space for 4 bags of groceries, and see if I can get into the 150 mph club at Bonneville and then get over 100mpg at the Vetter Challenge.

The numbers from the aero/rolling resistance calculater are

Wt 660 lbs
Crr 0.015
Cd 0.30
A 6.5 sq ft
CdA 1.95ft/0.18m
Eff 22%
Dr Tr 95%
Para 500 watts


This should get me 101.26 mpg @ 65 mph, and should need 49.5 bhp at 155 mph the bike is supposed to have 85 bhp.

[JethroBodine]

Looking forward to the build and seeing it in person at Bonneville.

[redyaris]

The first things on the to-do list are fit up belly pan and make apropriat brackets, then make new lowered seat pan; this should lower the seat height and rider by about 3" which will reduce frontal area by about 1/2 sq ft from the stock set up.

[housedir]

what?

[beatr911]

I, for one, would like a wide dustbin fairing.

Air tech has narrow ones that, though they may be period correct for vintage racing, are not necessarily what an everyday rider would want for big MPG numbers, or wind protection outside of a full tuck on a skinny 125.

Redyaris, you pick some tough challenges. You teach us alot about bike building and provide good discussion on engine tuning larger engines for MPG.

Seems that an advanced design engine with variable valve train, atkinson on demand and displacement on demand and advanced spark and fuel management systems and wide or dual ratio transmissions would be a large contributor to your goal.

Yousta be the bike guys got all the high tech, now it's the car guys. Even in B segment cars!

[redyaris]

beatr911
The dustbin fairing for the CBR 600 will be 24" wide at the front and 20" wide from behind the rider tapering down to an 8" wide rear bulkhead for mounting license and lights. the top of the rear cargo space will be lower than on the VT500 and round on the top in order to reduce side wind affects. I find I am more interested in what I can do with the bikes I own than simply going with the bike best suited to win the vetter challenge. In fact I find I learn quite a lot from this approch, which then gets applied to the next project. the final project will be a WR250 in a year or two, that one will be an all out attempt to win the Vetter Challenge over all...

[Grant-53]

Usually shoulders and hips are the same width: 20-22 inches. This can be the widest part of fairing. The lowered seat height should be 27 inches. Decide if you want to lean foward or lay back on the bike and arrange the controls to fit you comfortably. A body of rotation formed from a 5:1 aspect wing profile should minimize drag. Figure in some angle of attack to gain a bit of downforce for stability at high speed. For Bonneville consider some extra rear fin area. Internal flow should be ducted to reduce drag. Look at aluminum spars and ABS skin. Once the aero package is determined, power requirements will be known so tuning and gearing can be optimized.
Sound like a great project.

[redyaris]

I have chosen to lower the seat height to what can be accumplished without cutting the frame, this is about 2" - 3" which will give me a seat height of 29" +/-. I will be leanig forward, but some what less than stock, because of the lower seat height. I will not add any rear fine area as that will cause unnessisary affects from cross winds in normal raod riding, in fact I will be trying to reduce the rear side area to that which will accomidate 4 bags of groceries. the top of the behinde the rider cargo space will be a semi-circle; again to reduce side wind affects [at Bonneville if there is more than a 3 mph cross wind the runs are postponed, not so on the road...]. Much of this is from what I have learned from my VT500 project over 3000 miles. I will be using the same basic design as the VT500; which is aluminium skin over aluminium bulk heads. Much more care will be directed toward internal air duckting than with the VT500. On the CBR 600 the radiator is high and wide which will make ducting easier, and the front fender does a much better job of streamling the front wheel/forks. The transvers inline engine layout make cooling easier than with a V-twin Layout.

[redyaris]

I have been thinking about the 4 bag cargo space and where to put it. I would like to lower the overall height of the bike to reduce side wind affects, and what I have come up with is that the rear cargo section should start out at 24" wide so that the four bags of groceries can be placed lower. In order to do this I need to place the bags wider apart and lower down beside the wheel travel zone. This may also be the solution for a recumbent layout. I doubt that the additional width will be much of an aero penalty.

[3-Wheeler]

Originally Posted by redyaris

..... I find I am more interested in what I can do with the bikes I own than simply going with the bike best suited to win the vetter challenge. In fact I find I learn quite a lot from this approch, which then gets applied to the next project......

Yaris,

Couldn't have said it better myself!

Very good approach, especially on the first pass of a large project!

Jim.