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Discussion Starter #41
I should be able to provide before and after CFD's. I have scanned the body already already.

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shay2nak
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I cut holes in my Reverie side sills to allow jacking up the car without having to pull the sills. I put Velcro on the jacking points and cut-down (smaller diameter) hockey pucks. The pucks stay in place which makes jacking the car easier. I use the rearward jacking point to jack up one side until I get the jack stands in place.
That's a good idea, but I'm afraid to cut into the board. lol
 

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Acme Super Moderator ** The Enforcer **
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That's a good idea, but I'm afraid to cut into the board. lol
Easy peasy lemon squeezy. I'm assuming you saw the pic (post #21) in this thread. Here are pics of a "hole" from one, just to show it cuts cleanly. I could cut yours if you want.
Exige_Sill_Hole_1.jpg
Exige_Sill_Hole_2.jpg


San
 

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I should be able to provide before and after CFD's. I have scanned the body already already.
I'm interested in the scan and a way to get into the CFD process. I looked into getting one from 9Lives Racing but I would have to drive the car to the east coast and they are not real clear on what I would get from their CFD service. I am working on a much closer to stock car with aero mods legal for an autocross class rule set. I want to do CFD in order to play the what-if game. I would appreciate any advice on non-professional usage of CFD and getting a stock Exige or Elise CAD model to start from.

I'm also interested in how you performed the scan as I've been reading up on how to get one. There has to be something in a city the size of Houston but the one company I found only replied that I would not be able to afford it.

I like the front wheel vents, are they custom or did you adapt something?
 

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I should be able to provide before and after CFD's. I have scanned the body already already.
I'm more curious how you went from the scan to a reverse engineered model that is useful for CFD. I've worked with quite a few STL files from scans and they're not easy to convert to parametric models if the geometry has a lot of curvature. Flat surfaces, cylinders, holes, cones, etc.... sure. But an Elise body would be a whole new level of frustration.
 

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Discussion Starter #46
I have quite an expensive scanner which gives me the mesh and it's software converts it to various files including STL . I have another friend whose we versed in this and states that it can be done.
It will take a while as this is a hobby and I have a real job that pays the bills. The scanner is really an extravagant toy for me.
My fund a friend to work on this project. He's a pro at carbon fiber. We have a massive oven for dry carbon.
This is all custom.

Now , one can look at this project and think well until we have CFD data this is all just fanciful. That's kind of like saying we don't have enough data to determine whether jumping out of a plane without a parachute really kills u since we don't have a double blinded placebo controlled trial consisting of 10,000 individuals... Ok . I'm going way over . Lol.
If you connect the dots between the angles on this model and what one sees on other time attack race cars in Japan, Super GT , etc . This has gotta be at least a little better than stock in terms of grip.
If we manage to pull this off and get data/CFD without the budget of a race car team, I think this is cool. Trust me, thus far, it's cost a lot of time, money and frustration. But without innovation and failure there cannot be progress.


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If you connect the dots between the angles on this model and what one sees on other time attack race cars in Japan, Super GT , etc . This has gotta be at least a little better than stock in terms of grip.
One of the best exercises I've seen for working out the aero of a car is to really understand how Canards work. If you think they are wings, do the math based off their area, and you'll find they are useless as wings. Heck, they hold on with strong tape. So how do they work? They create a vortex down the side of the car with a vector inward at the base of the door - this fights the air trying to exit the bottom of the car and creates a sort of invisible side skirt. This means a Canard can actually add rear downforce since it improves the diffuser, so why do they sometimes reduce rear downforce? Because that same vortex travels down the car and hits the rear wing with an upward vector. This negates some of the downforce at the edges of the wing, so you want to set the Canard such the the vortex hurts the rear wing as little as possible, and that's not something you can eyeball.

Not to imply you don't already know this if you do, just saying I think it is a great example of the interconnectivity of aero
 

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Discussion Starter #48
I didn't know that the canards can influence the wing. Thats interesting .
The canards would have to be installed them adjusted just like the wing , or rather one adjustment at a time , in order to get the best result.
If the wing is set further back ( swan neck mount ), this reduce the way the canards and wing interact?

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I didn't know that the canards can influence the wing. Thats interesting .
The canards would have to be installed them adjusted just like the wing , or rather one adjustment at a time , in order to get the best result.
If the wing is set further back ( swan neck mount ), this reduce the way the canards and wing interact?

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The biggest advantage to setting the wing further back is that it actually helps the diffuser. The low pressure region below the wing can draw more air through the diffuser, and you end up with more net downforce than the sum of just the two separately. Thing of it like a giant dual-element wing. The downside is that you shift your center of downforce even further backwards, and that's less than ideal.

With the size of your side skirts, I would think that, without CFD that requires a supercomputer, guess/test/repeat will be your best bet, but the canards aren't likely to be a noticeable help. I have a personal and barely founded theory that most people who remark about the increased from grip from canards are actually loosing rear grip and just feel the balance aero shift forward because of that.

Simon McBeath's Competition Car Aerodynamics textbook is an excellent and easily approachable reference, and I have to give him credit for almost all my theories about Canards. He also includes some examples of an Exige in a wind tunnel that provide a lot of insight for your project.

Here's a link: Competition Car Aerodynamics 3rd Edition, McBeath, Simon - Amazon.com
 

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Discussion Starter #50
Great info.
In fact when I switched to a bigger front spoiler with canards the difference was night a day when cornering . I could take a sweeper at 10-15 percent faster . There didn't seem to be a car that could manage to same speed on the track . Definately changed the front to rear balance but I liked it as my confidence grew.
Thanks for the book tip ... I'll add it to my collection

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I have had some email conversations with Mr. McBeath about details of my aero plan. The interactive effects the aero are why I'm interested in doing the CFD. There is an interesting video of a Pikes Peak amateur team by an aero engineer about how they used CFD and straightaway testing to greatly improve their aero performance. They put sensors on the suspension to measure the amount of compression at 100 MPH on a very smooth straight. They used those results to tune the CFD such as decreasing the cell size to improve the accuracy of their CFD model.

 

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I was looking into low-budget CFD solutions a while back. I'm not sure how accurate the model is, but Hum3D has an S2 Elise (and S3 for that matter) model. The model formats include STL, STEP, IGES, etc. In particular, the latter two appear useable for a meshing environment.

Here's a screenshot of what the model looks like in CAD:


In terms of CFD... Autodesk had a free simulation tool for a while, but it was limited in capability, though neat to look at the animated visualizations.
 
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