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Old 01-13-2017, 06:10 PM   #61 (permalink)
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Old 01-20-2017, 10:51 AM   #62 (permalink)
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Progress so far

Smoothed out the needless sculptural stylings on the front, extended the fairing backward. Still want to add another layer or two for strength, making a notch for the windshield had the benefit of additional support for the extensions.

The area near the controls will be cut back as necessary to eliminate interference during steering.

I think it is an interesting form factor to have the fairing extend further back than the windshield- I see it as a puzzle piece fit relative to the shape of a head and shoulders.

So the next question I need to resolve is air intake shape/size. I think my intake is too large, and need to figure out the appropriate adjustment. If you look at a motoGP bike, the port is arguably smaller than mine in area, and flowing enough to support nearly twice the HP. As to shape, I am puzzling if there is any point to creating an "ideal" intake shape (flattened oval at the high pressure tip of the bodywork) if within the next 8 inches, the air intake is going into the frame as a square that divides in half around the steering stem and then rejoins behind before entering the airbox- better to just emulate that square so the air contorts as little as possible on its travels?
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Old 01-20-2017, 11:12 AM   #63 (permalink)
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Those tail sections are really interesting- particularly how they are hollow U-shapes.. anybody know how this form compares to a solid box? I am assuming that a box is better since it is not "asking" air to fill that space..

apropos to this, check out these things:


Those undertail "vanes" were immediately banned- thoughts? I am having trouble understanding their value..


Quote:
Originally Posted by Michael Moore View Post
Harley XR750 long-track fairing with custom large/shallow taper seat:







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.



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):



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
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Old 01-20-2017, 11:21 AM   #64 (permalink)
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That is beyond my means, but I did flip the exhaust can upside down so the stream is directed more up and into the area you envisioned, rather than splatting down at the ground. Shouldn't mess up the engine tune since I haven't changed the length or bends of the overall system..

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Can you relocate your exhaust above rear wheel to fill the wake?
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Old 01-20-2017, 11:33 AM   #65 (permalink)
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how did you determine the appropriate taper rate? Was expected top speed a factor in that math?

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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.
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Old 01-20-2017, 11:47 AM   #66 (permalink)
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0&7) The DOT race tires you see are my oldest set, for the bike to sit upon over winter. I race superbike and GP classes only, on full slicks. Those SS guys can keep their extra limitations, I want to build/race the toy I want.

1) going to experiment with that. The only way to really know is to go out in practice on a race weekend and see if they registered laptimes for my session. so this is on the back burner until April

2) totally agree. The race bodywork sold to us is derived from showroom differentiation rather than aero. Check out my progress pics.

3) interesting idea- I would have to do some testing on that because I believe the tire warmers are a rather tight fit already.

4) they don't make the corsa for the 2006 unfortunately. I ought to see how different they are from the 2008+ bike, something might be doable..

5) How did you determine the benefit?

5b) yes, I am on the newestfangled ultralight 520 chain/sprocket

8) No doubt- but this is the best I can do in the middle of winter
(I'm working on minimizing personal deadweight too)

Quote:
Originally Posted by freethink View Post
I'm going to assume you are running in the supersport class, seeing as how you aren't using slicks.

1) Move your transponder somewhere else. Maybe behind the gauge cluster. You still want it as far forward as possible, in case you are neck and neck with somebody at the finish line.

2) See if you can get a front fairing without those funky air channels on the sides. Chances are, if MotoGP guys aren't using funky bodywork, then it's probably just a gimmick.

3) A front fender that extends farther forward over the tire, might be beneficial. It looks like there is a pretty large gap (an inch or so) between your current front fender and the tire, which may act as a air scoop, increasing drag. Maybe you could modify the mounting holes, to get the fender closer to the tire

4) It looks like you already have a taller windscreen, but there are others on the market that look like they may provide better wind protection. I'm thinking of the Zero Gravity Corsa screen. The Sport touring one is even better, but you may run into helmet clearance issues with that one. Perhaps you could get that one and trim it so it doesn't interfere with your helmet.

5) When I used to go down the straights, I would take my hand off the left bar, and grab onto the top of the left fork. That would get my hand out of the air stream, and allow my elbow to get in tighter to the tank. I've even seen some guys put their left arm behind their back to reduce drag, lol.

Unrelated to aero:

5) Perhaps you could clean, polish and re-grease your brake pad retaining pins/sliding hardware to makes sure there is no excess friction. Same thing for your drive chain. Are you running a 520?

6) I hear Daytona is really hard on tires. I think they make special tires for that track to cope with the steep banks.

7) Superbike allows for a lot more modifications. Have you considered moving up?

8) Rider skill is by far the biggest factor in going fast on any track. Practice practice practice. Your riding looks very good though.
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Old 01-20-2017, 12:00 PM   #67 (permalink)
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My take on this is that ducati is probably right that this was a strategic block of the technology by manufacturers who had less to gain by the winglets. Ducati is known for being a powerful but wild ride which tends to lose out in the corners against the other bikes. Anything you can do to interfere with ducati's advantage in the straights is good for you as a competitor.



This race was an excellent demonstration of ducati top speed. It is also one of the best races I have ever seen. Crack a beer and check it out! (skip to the 30 minute mark to bypass the pre-race content)

Interestingly, a rider complaint about those winglets was that it added so much stability to the bike that it was noticeably harder to wrestle through directional changes. Dani Pedrosa's parakeet-like physique was so unfit for the task that he couldn't go the distance and thus his bike quickly did away with the winglets. This rule works out well for him in particular.

Quote:
Originally Posted by jkv357 View Post
Ya, I get what wings were used for, but if Ducati could find them useful I'm sure that The Honda could figure out how to make them work. The fact that Yamaha and HRC tried them and didn't use them consistently says that maybe they weren't all that.

Reducing R&D costs is the main focus of almost all new rules at this point.

I don't think that additional MotoGP wing development would have benefited street bikes very much, but that didn't stop Kawasaki from going nuts with them on the H2R - https://i.ytimg.com/vi/N3QvX24iBiE/maxresdefault.jpg

Kawasaki and Ducati were relying on big power to get all that top speed, because those wings aren't helping (except for reducing the need for more electronic wheelie control when accelerating at speed).
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Old 01-20-2017, 12:29 PM   #68 (permalink)
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Looking at your first picture, you might be able to get lower drag from your tuck by slightly standing up on the pegs, lifting your rear so that it is less angled. Take another picture like this and confirm that your frontal area is not increased.

Also, hard to see from your first picture, but does your front fender have deflectors on the sides of the forks? Moto GP bikes have those, and I would assume they contribute to lower drag.

Quote:
Originally Posted by jakehammer2000 View Post
how did you determine the appropriate taper rate? Was expected top speed a factor in that math?
I have hucho's book on aerodynamics, and I read in it that the longer the shape is, the greater the taper rate could be. Shorter vehicles have best drag at a taper rate of 13 degrees, while longer vehicles can get away with 22 degrees. Motorcycles are definitely the short kind.
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Old 01-20-2017, 02:43 PM   #69 (permalink)
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How about closing off as much of the radiator intake as possible? I would think a lot of drag is due to the design of the cooling system.

Would an automated grill block for motorcycles work?

How about a teardrop shape on the trailing edge of the arms (of the rider) made of foam? It seems the arms are often out in the wind.

I have no idea what the rules are, so I'm just thinking online.
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Old 01-20-2017, 02:43 PM   #70 (permalink)
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