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post #21 of 44 (permalink) Old 10-04-2013, 05:52 AM
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Help round out my knowledge on front canards, and I don’t mean to highjack this thread so if needed I can start a new thread.

Most of what I read about canards say that they produce minimal down force on their own. The bigger advantage is the vortex that is created down the side of the car that seals, cleans up the aero further down the car.

Canards and vortex generators
Automotive Aerodynamics - Sport Compact Car Magazine (about 1/2 way down)

as some examples.

So with people saying they are using strings and go-pro'ing and/or the Reverie pictures that show the airflow over (just) the canard, what are you looking at/for?

It seems to me that you would want to look at the aero down the side of the car to see if you have the canards in the correct place.

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post #22 of 44 (permalink) Old 10-04-2013, 06:13 AM
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Vortex generators are usually very small and plentiful. They used used to "fix" aerodynamic problems discovered during testing (wind tunnel and flight/driving). Vortex generators create lots of energy to keep the boundary layer attached...they only work inside the boundary layer. So, canards cannot be classified as a vortex generator. Canards can be classified as aerodynamic fences. An Aerodynamic fence is used to re-direct airflow. This re-direction on a car produces down force and re-directs the air stream across the side of the car...Reverie does not share that information, but I seriously doubt it does anything of consequence to the rest of the air flow (down stream) across the Elise/Exige.
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post #23 of 44 (permalink) Old 10-04-2013, 06:17 AM
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Canards can be classified as aerodynamic fences. An Aerodynamic fence is used to re-direct airflow. This re-direction on a car produces down force and re-directs the air stream across the side of the car...Reverie does not share that information, but I seriously doubt it does anything of consequence to the rest of the air flow (down stream) across the Elise/Exige.
So they, for street cars anyway, are more for show than go.
Ok, thanks.

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post #24 of 44 (permalink) Old 10-04-2013, 06:46 AM
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So they, for street cars anyway, are more for show than go.
Ok, thanks.
No...I didn't say that! I guess I need to be clearer.
What I tried to say is that a vortex generator is a different kind of aerodynamic device than an aerodynamic fence. The canard is an aerodynamic fence. It is not a vortex generator...per se. Any aerodynamic device will produce a vortex off the end of it, if it works! And, it is just as effective as any other aerodynamic device. Just like any other aerodynamic device, the faster you go, the better it will work...so drive fast!

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post #25 of 44 (permalink) Old 10-04-2013, 07:06 AM
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This is where I had Pooter put mine. Unfortunately it was after I deployed and he had not driven mine on the track before, so I have no real information on how much they help. I am just looking forward to next spring when I get home and track season starts!!!
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post #26 of 44 (permalink) Old 10-04-2013, 07:10 AM
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My guess is that yours are too low...looking at where Reverie placed theirs, it looks like they were aiming to get the canard's down stream to work with the mirrors...but just my guess.
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post #27 of 44 (permalink) Old 10-04-2013, 07:13 AM
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Doug asks a good question - what is being looked for with airflow and string movement?

I should say up front that I'm not an expert and don't want to put myself out there as one. I've read a few books, studied a good bit of video and consider myself to be a curious guy and for the most part this serves me pretty well.

With that said - I was looking for smooth and attached airflow along the clam shell just below the headlight and above the canard primarily. If you get the shape or angle wrong the strings do crazy things and can whirl in circles or even start to face forward if you get it way wrong. But get it right...........or closer to right..........and the strings on the canard lay pretty flat and point up and back on the canard and don't just flail to the side. The strings on the clam just below the headlight stay stuck to the clam and run more or less parallel to the canard indicating that the air is rising in that area. I did not cover the entire side of the car with strings and see how the canard affected airflow over the front wheel well and back toward the rear wing. I think that would be fun and interesting.

____________________________________________


This is a bit off topic at this point but one place I found really lacking in the original Lotus design was the rear diffuser. All the reading I did said that the angle of the roof of the diffuser was really critical and that the typical effective angle was somewhere between 7° and 14°. The stock Lotus diffuser is made of of three sections with the outer two having a roof angle much steeper than the center section.......and much steeper than the accepted 'norm'.

Using the same strings and GoPro technique I tested the airflow on the center section of the diffuser and the steeper outer sections. The airflow on the center section looked to be smooth and attached..........the strings stayed against the roof of the diffuser and pointed back. I tested this at low speeds as I am most interested in solo events so I was testing at 55 mph. At higher speeds the strings were quieter and almost looked glued or stuck to the roof.

The outer sections of the diffuser were not this way. The roof angle is very steep and the strings pointed mostly down and whirled in circles. This made me think that the air is in stall here...........it certainly wasn't attached airflow. Common sense lead me to believe that the air would need to move back and up, just like in the center section, to best make a low pressure area under the car.

So I next made a fake cardboard roof for the side pod of the diffuser that I could adjust the angle of. I then tested the airflow at various angles and found that much like the angle of a rear wing - a very small difference can have a profound effect on how the air moves. I changed the roof angle about 2° at a time until I got good attached flow at my relatively low speeds. It was very cool to drop from 11° to 9° and watch the string action totally change. I settled on 9° which coincidentally or not was the same angle as the large center section of the diffuser.

Once I established the angle I wanted took a stock diffuser and removed the side sections and replaced them with sections that I made at the new lower roof angle. I made them a bit longer in an effort to make them as effective as I could.

____________________________________________


I did all this stuff for two reasons - I race solo (XP) and want every advantage I can get and I find learning new stuff to be fun. I've had many question why I would bother with aero stuff for solo as the speeds are so low. Well I'm lucky to have a place were my SCCA club and the others in Montana use a large facility that allows for sustained slalom speeds of 80+ mph. There is also a section of road (the place is a police and fire training facility) that has a long radius right/left curve combo that can be taken at well over 80 mph.

Before I made the aero stuff and bought the wing the car was unstable in these high speed sections and if I had gone in too hard or deep it was a real wrestling match to keep the ass end of the car behind me - lift and spin. With the aero stuff in place I can now flat foot it though this high speed road section and if I'm going too hard can lift a fraction and not fear the car swapping ends. My times dropped and my placings went up.

I feel completely confident in saying that someone with more smarts and experience could set the aero stuff up better than I could and that the car would be faster still.........and at the same time I am 100% sure I am faster, and that the car sticks better, due to the fine tuning of things. If I had just bolted stuff on it would probably improve some but I feel good knowing that I did what I could to get the most out of the car. And it's just gravy that the race results have been very good.

Fun stuff to mess with.

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post #28 of 44 (permalink) Old 10-04-2013, 07:14 AM
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If you guys don't know - Travis is the man. Thanks chief. BTW (off topic) did you ever do a thread/write-up on Jason's shifter? I know it's a very specific product but man, there's something there...

We were going too, but then we noticed that the paper model that we made at first kinda looked like a kids project from grade school, so we were going to glue macaroni to it before we posted photos (kinda like a red panda thread)... and then we forgot...

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post #29 of 44 (permalink) Old 10-04-2013, 07:22 AM
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If they are too low I will move them. Car has been through one too many fields before I started to track it. So best I figure out what works best before I have the front fixed so no worries on drilling extra holes.

Now you guys having me miss my car terribly. Sorry for hi-jacking the thread with extra pics
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post #30 of 44 (permalink) Old 10-04-2013, 07:27 AM
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When your car looks that good no need to apologize for the extra pictures! Love that Difflow diffuser - I don't think you can go too big there and that looks fantastic!!

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post #31 of 44 (permalink) Old 10-04-2013, 07:35 AM
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Adrian Newey's Exige had the front of the canard at the level of the top/front line angle.


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post #32 of 44 (permalink) Old 10-04-2013, 07:40 AM
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Thank you for the complement. Especially compared to your car Ross. Just amazing

She has had a hard life but always brings me home.

Glen does and nice job on his diffusers. I have been very happy with them. Going to do a back to back day with this race vs my old railer this spring to see which I like better

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post #33 of 44 (permalink) Old 10-04-2013, 11:57 PM Thread Starter
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JJ......Thanks for the input. Looks like this is the correct place............


Good2go.....thank you for the pictures!

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post #34 of 44 (permalink) Old 10-05-2013, 12:00 AM Thread Starter
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Oh god! Next time refresh the page before reply........It sploded!

Thanks for the input and pictures!

2012 Evora 2+0 IPS.
2007 Exige mental track toy.
2005 Elise.
1982 Brunette.

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post #35 of 44 (permalink) Old 10-05-2013, 02:43 AM
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JJ......Thanks for the input. Looks like this is the correct place............


Good2go.....thank you for the pictures!
When I get mine, that is where/how I'm going to mount mine...
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post #36 of 44 (permalink) Old 10-05-2013, 11:15 PM Thread Starter
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This is some fascinating reading: https://docs.google.com/file/d/0B5kL...it?hl=en&pli=1

I guess I need a new diffuser!

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post #37 of 44 (permalink) Old 10-06-2013, 04:37 AM
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This is some fascinating reading: https://docs.google.com/file/d/0B5kL...it?hl=en&pli=1

I guess I need a new diffuser!
Interesting isn't it? They got pretty much the same results I did with my strings and Go Pro.

My gut tells me the only diffuser out there that one can buy that would work as it should is the Difflow flat model. it would be interesting to put some strings on it and see what they do. The strings never lie.

dave
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post #38 of 44 (permalink) Old 10-06-2013, 05:51 AM
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If you guys don't know - Travis is the man. Thanks chief. BTW (off topic) did you ever do a thread/write-up on Jason's shifter? I know it's a very specific product but man, there's something there...
+1. That shifter is an amazing bit of engineering IMO

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post #39 of 44 (permalink) Old 10-06-2013, 08:24 AM
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Interesting isn't it? They got pretty much the same results I did with my strings and Go Pro.

My gut tells me the only diffuser out there that one can buy that would work as it should is the Difflow flat model. it would be interesting to put some strings on it and see what they do. The strings never lie.

dave
I would say the Reverie diffuser...
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post #40 of 44 (permalink) Old 10-14-2013, 03:43 AM
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I've just stumbled across this video...
Lotus in the A2 Wind Tunnel - YouTube
When the smoke stream goes to the front corner of the car, it direct the stream into the side scoops. With large canards, that could inhibit that. In my opinion, the outside shape of the canard is very important for that...not only placement...I would copy a Reverie shape if I could find one...
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