Minimizing drag at 140mph+
 

Hello folks,

I am an amateur motorcycle racer, and at the end of the 2017 season I plan to enter the Race of Champions at Daytona. Unlike other tracks on the calendar, Daytona has long full throttle sections where you will hit and hold the maximum speed of your motorcycle for a relatively long time. Drag is not an area that amateurs put much effort into- we buy "race bodywork" and worry about other issues like tire costs, lean angles, and why there aren't more ladies in the grandstands.

So I have been doing some reading and think I have a general understanding of streamlining, but am hoping you can help me stay on track. My goal is to produce a second tail section (over these winter months) that I can swap on and test in race conditions for benefit to top speed.

I will try my first image upload in a moment to support the following questions:

1) Given the side view, how far off from "ideal" is the curvature of my back- does it even matter what the tail section looks like?

2) Assuming the back curvature is a workable aero shape- what should the tail section look like? It seems to me it should be taller, at a height relevant to the air flowing off of me and onto it smoothly. Thoughts? How about the gap between me and it?

3) My tail bodywork probably can't extend more than an inch or two further from the back without setting the race officials after me- so is a Kamm the way to go? How do I know what angle it should decrease by, and is it a speed-adjusted answer?

Thanks, Jake

race tuck

http://ecomodder.com/forum/attachmen...5&d=1481489508

With a bike, youre never going to have enough rear length for attached flow, you should focus on frontal area.

1)aero template Overlay found at the top under tools .Im working on an android so not as easy but doable
2a) that is pretty good-looking down to about the love handle area ,wight stripe on your lethers, things get too steap from there adding a spacer to fill the Gap behind your hips and continue the transition to the tip of the tale. Think like a fish. (|) not like a whale (--) your+bike are so short you don't realy have room for reattachment vertically.,However horizontal taper ,your setup is small, and you are tapering on 2 plains L&R. 12°per 10%length ea.take it as farback and down as the rules alow..
Tuck. your helmet has a cam built in , the gold wing, to reduce buffeting caused by the uneven separation of a standard helmet. However in the pic its more of a trip edge /spoiler. It needs ~(aproxamitly) 15° rotation clockwise. Based on the brick wall as levle this 15° will reduce frontal area and move the template 6" forward, allowing more room for taper=better CdA

2b) add a tail to your lether with industrial velcrow make follow the 3d template on 3 sides T,L,&R. Botom contorted to matchrear faring. Was thinking semi dense open cell foam.

2c) gap should be interference fit. Ast why I suggested the gap garde be attached to you . And with this attachment it must give in a crash and be brake away to prevent further injury.

3a,b)see 1 and 2a
3c) idk Aerohead or others may chime in.

I would think if you have more fairing, just enough to cover hands, legs, and shoulders more completely when in full tuck you'd have made significant progress. Fairing the front wheel and a more significant tail than you have would probably also help you slip through. Your suit/gear could do more to reduce separation beind your helmet in full tuck. Here are two images (you may well have seen before):

http://www.tonyfoale.com/Articles/Ae...s/AeroOpen.jpg

http://www.schultzengineering.us/Aero/img005.jpg

Those Hayabusas are blazing fast yes, until they encounter a corner...

I have a few observations on your dilemma

1. Congratulations on even thinking carefully about this subject, because aside from windtunnel testing rider position, even the MotoGP teams have made no serious attempts to "streamile" bike designs

2. Unlike cars, motorcycles have a different geometry, with much lower width/height ratio. For this reason it makes more sense to focus attention on smooth airflow down both SIDES not over the top. We have become accustomed to diagrams, templates and side-view photographs, all borrowed from the car industry which has led the way in all things aero. However, much of this is irrelevant.
Have a photographer snap you from above for a plan view, this will help you more.
As gumby says: Think like a fish!

3. I think the "dirtiest" part of the airflow will be aft of your arms above the elbows. This is the widest part of your plan profile and has no chance of re attachment and plan taper due to the abrupt cut-off. To mitigate against this you could consider filling the area from upper arms back to your hips
Think of flying suit wings, as used by the base jumpers. A strong flexible membrane would smooth the airflow back to the point of separation on your butt
It would mean modifications to your leathers not the bike, no problems with scruitineering and you'll get plenty of attention - make the membrane black. If it doesn't work you'll have to give up bike racing, because you'll forever be known as the "batman biker", but if it does work you will be instantly famous when Rossi and Marquez copy you.
One problem I foresee is that when you get your trophy, you won't be able to hold it up for all to see!

You are pretty limited by class rules.

I don't think any significant mods are going to be allowed, but I would study the Rule Book. It's all in there.

Airtech has nice aero fairings: Motorcycle bodywork, 6000+ fairings, tanks & tails, USA built!
Maybe you can find something over there that might find, post it and we'll give it a quick comment.

Thanks for all of the input, everyone.

As noted, I am indeed constrained by the rulebook, the key quotes are:

1)The front wheel must be clearly visible from both sides except for the portion covered
by the fender. [I might be able to add a little material without attracting attention,worth it?]

2)The rider must be visible from the side and above, while
in a normal riding position, and transparent material may not be used
to allow for such visibility.

I have finished races to find that I wore paint/fiberglass off the sides of my bodywork from the lean angles, so I have to consider width to already be maximized.

Working on more imagery, will be back to add to thread.

Those rules and your riding conditions seem to suggest that you could expand the top portions of the fairing to screen shoulders and more of your head. And I suppose leathers with a larger aero blister behind the helmet would help too. I doubt anything above the front wheel is worth it. Are there no rules about the rear wheen and the tail?

duct tape on our left was for visualizing the rider coverage if I added fiberglass in the easiest spots. also shows front fender

I am a bit crooked because I felt like the bike was going to fall out of the front stand. But you get the idea for how thin the tail is compared to rider..

The rules for that section are that the tail and fender will extend at least to the rear axle, so they were only setting a minimum rather than a maximum. I think I could extend the tail to end exactly above the rearmost tip of the tire without causing a commotion and failing an on-the-spot "new rule" during tech inspection.

Here are the areas I think I can add material without major trouble. Which are likely to help, and which are dead ends? Assume also for the tail that width could be increased to match my pelvis as shown in the overhead view.

I played with the ecomodder template a bit, but when it comes to actually placing that onto my form, there are actually a ton of fine adjustments possible, I'm not sure what the "right" overlay placement would actually be?

https://youtu.be/RnRPiENn954?t=4m10s

There's the bike in action, to visualize the environment. Or just for fun.

That airbag vest you see will not be used at Daytona. Willing to take the short term risk to get slippery.

1)Do they require a stock front finder? Or can you simply make a bigger finder ,cover more tire/wheel . The way i read it you you can not enlarge the findder but you can build a 1pice larger finder. I am gessing that this rule is to maintain airflow to the main brakes.. So make shure your brakes are not compromised by adjustments to shape and size.
1b) depending on the end results, has potential.



2)The fairing on your back is the basic shape I'm referring to. Make it come up to the bottom of white strips down to the seat and back to tip or beyond of the bike . It would be part of you, aka not obstructing in the view of the rider. The other benefit would be that it would work in the corners moving with you when you shift to lean off paint.

Can you post a link to a pdf rule book or web site . TY.

So you mention 12 degrees per 10% of length- is there some article I can review that discusses this rule of thumb?

As for the helmet and leathers, I really can't modify them per rules. With my chest slammed against the tank, that helmet position is my maximum upward look (actually takes a lot of effort). I am trying to get an unpadded race seat, which should lower my pelvis an inch or more into the bike- as the rest of my body follows, I might get those extra degrees clockwise rotation of the helmet that you recommended.

Thanks!

I took a look, what they have for a 2006 YZF-R6 is pretty much the same as what we have in hand..

Here's the rulebook:
http://www.ccsracing.us/forms/2017/r...20Rulebook.pdf

They say it can't cover the wheel- technically the wheel s not the tire, so I might be able to extend the fender down the sides another inch or two only blocking view of the tire but not the rim- is that even worth it?

I noticed that a lot of factory race bikes have a fender shape like mine, but they cut the back side off a lot sooner than mine. Check out this pic- Nothing to the rear of the fork tubes. I suppose they have a stack of radiators in hand in case they shoot a rock through one.. unlike me.

mine for comparison. tilted way back on the wheel more like a parachute..

I am surprised that nobody has mentioned the green box (transponder I assume) cable-tied to the front forks. That would cause a nice lot of turbulence and could also affect cooling.

I would consider flattening and bending the "beak" of the front fender downwards to reduce air getting under it. Also, what are the cable loops on the lower right of the bike?

Also, have you tuft tested the front fairing? I think the sculpting in the center that is covered by the racing number could be tuned a bit - maybe the number might have to be stretched across tighter to reduce the "valleys".

At the speeds you are talking about, these small details may all add up to something significant.

Simon

Aerodynamic Streamlining Template
Attachment 21045
Ill have to track down the quotes. I think it may have ben in Aerodynamic Streamlining Template: Part-C
You are more interested in the top view. . The 0 point would be your elbows.
http://ecomodder.com/forum/member-or...y-supplied.jpg

A bit of a tongue in cheek one here - have you considered body modifications like narrowing your shoulders?

Getting more serious, some of the tabs and stuff on the shoulders of your leathers will also trip up the air flow. Smoothing them with the "sharkskin" type finish may also help.

Simon

You are right, that is my transponder. The position is not mandated, I could experiment with mounting it somewhere higher inside the fairing. Would have to test if that causes timing errors from obstructions..

I am not sure what you see as cable loops, but maybe you are looking at brake lines or throttle/clutch cables?

I could find a way to de-sculpt that transition from bodywork to windscreen. It's like that as a yamaha styling.

For narrowing shoulders, are you referring to positioning or body composition?

I am a bit reluctant to attempt to modify the suit- it's $2000 of aussie roadkill and composite armors.
:eek:

Is this worth doing?

Is this one available as a transparent overlay? I am only finding the side view

http://www.rynofender.com/wp-content...nder-logo2.jpg
Would this help?

Btw, that vid of you on the track was impressive. good luck.

Rules interpretation
 

..... this makes my prvious tail/butt fairing useable, unless it is attached to the tail of the bike.
.... Theas are the materials you can use for your mods. Except parts associated with drake cooling and wind deflectors.

....I read this to mean the entire front wheel/tire can be covered by a 1pice finnder
A 1 pice finnder would combine both 5.2.11 and 5.2.4.c

They state a minimum... no maximum. Added length is a compromise between reduced aerodynamic drag and increased Rolling Resistance coefficients. Use Aerodynamic & rolling resistance, power & MPG calculator - EcoModder.com to figure out how far you can go and see a benefit.
Gumby Stay Flexible.

In tool "aerodynamic template overlay" select "Template #2" in point 4 of upper table. You should see it.

Harley XR750 long-track fairing with custom large/shallow taper seat:

http://www.eurospares.com/marcxlf.jpg

http://www.eurospares.com/marcxls.jpg

http://www.eurospares.com/marcxlb.jpg

The HD and Norton JPN fairing are the main "classic" RR fairings that I know of that were wind tunnel tested instead of styled. The HD was done by the Wixom brothers in the CalTech tunnel and I think the Norton at MIRA.

http://www.motorcycleclassics.com/~/...Monocoques.jpg

A 13" wide seat like that on the red bike (shown is a 15" seat) added 500 RPM in top gear to a pretty stock CB125 Honda engined bike and was good with tuft testing at freeway speeds. That bike had about 7-8 hp. Most rider's butts are 15+" wide and the seat should match the rider and fill in behind the legs to give a smoother outer surface.

Here's a photo of the last version of my Laverda F750 racer with HD fairing and big seat (not the same as the "big butt" HD seat):

http://www.eurospares.com/graphics/L...RLeftRear1.jpg

The back of the bike is more important than the front, and remember that the bodywork is there to streamline the rider NOT the bike. Unless you've got a CBX or a Boss Hoss the rider is the wide part of the combo. :)

Most rule books I've seen exempt the hands and forearms from the "rider must be visible from the side/top" rule.

If you look in this folder on my website

Index of /graphics/aero

you'll find a scan of an article (Free Speed) comparing 1970s RR fairings, including the Norton and HD.

Try to find a copy (used only available at this time) of John Bradley's "The Racing Motorcycle, Vol 1" as it has a lot of good info on RR streamlining including the wind tunnel runs on the Can Am LSR bike.

The trend in modern bikes seems to be to lower the top of the tank to make the rider's back more horizontal. Of course, that can make it difficult for the rider to see where they are going if they can't tilt their head back far enough.

cheers,
Michael

Those are good Michael Moore!

Typical land speed front fender, supposedly good for 2-3 mph:

http://www.airtech-streamlining.com/...SX13LSR4~1.jpg

Can you relocate your exhaust above rear wheel to fill the wake?

Good stuff. Some organizations limit the height of the tail box so you might want to check into that. If your back is horizontal with a slight curve, be sure there is no gap between you and the tail. A top view should look like a teardrop to minimize air flow separation. One trick we use on our pedal bikes is to streamline the spokes on the front wheel and use smooth disk wheel covers on the rear.

Something else to consider is whether or not you can get adequate leverage on the bars/clip-ons if you move them inboard. You might have to move the master cylinder inboard of the clamp or something similar, but that mod allows you to get your elbows out of the windstream some more. Also, consider running some duct tape around the top of your boots.

On my 216cc Honda vintage racer I made the bars very steep and narrow to encourage me to stay on the tank (the only time they were comfortable) as much as possible.

http://www.eurospares.com/graphics/H...CR216003a5.jpg

http://www.eurospares.com/graphics/H...CR216005a5.jpg

http://www.eurospares.com/graphics/H...CR216006a3.jpg

It ended up with a fairing that was sort of a 7/8 scale version of the HD long track part. A long Seeley aluminum fender never got installed on the bike before I moved on to other projects:

http://www.eurospares.com/graphics/H...CR216006a2.jpg

LSR example.
 

I did a bit of research and some fluid dynamic work when I was building my land speed racing moped. It is my belief that you want to do as much as you can to reattach the air behind you to minimize the vacuum. The attached photo isn't the final result but you get the idea. I was not able to get any wind tunnel testing but the bike holds the record for being the fastest 50cc motorcycle to run at the Ohio Mile. It is a 1977 Puch single speed moped so I suspect the aero had to help. The rear section starts out as the width of my butt and tapers as much as possible without the air separating then is chopped flat as per the rules pertaining to how far back the aero may extend.