Aerodynamics Fundamentals: Rear Wing Selection
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Rear Wing Selection
06.52
| 00:00 | In most cases at the club level, we're best off buying an off-the-shelf rear wing from a reputable manufacturer. |
| 00:06 | This will ensure that we get a product that has good aerodynamic performance, but is also strong enough to take the loads it generates. |
| 00:13 | An example wing that I've personally worked on and I can recommend is the Sydney Composites Brackley wing, which has an extremely optimized shape as well as a lot of intricate detail work which we'll discuss in a moment, to maximize aerodynamic performance. |
| 00:29 | The main differences between a well -designed rear wing versus a wing with worse aerodynamic performance fall into three categories, the wing's profile, detail work and adjustability. |
| 00:40 | A well-designed wing will have a customized, high-performance wing profile that's been optimized to generate high amounts of downforce without creating crazy amounts of drag. |
| 00:49 | In the case of high-performance 3D wings, this profile varies across the span to maximize performance when considering the typical flow profile of the back of a car. |
| 01:01 | In many cases, a 2D wing is perfectly adequate though, and is often the prime choice when going for a wing where we're unsure of the manufacturer's aero knowledge and testing program. |
| 01:11 | For a quick clarification, when discussing 2D vs 3D wing designs, a 2D wing has a constant section across the whole span of the wing, think of it like an extrusion of a single profile from side view, meaning that it's uniform across the entire width, whereas a 3D wing has a more sculpted or curved shape in an effort to optimize airflow across its span. |
| 01:33 | Moving on, I've been talking about detail work, but you might be wondering what this actually means. |
| 01:39 | Detail work refers to the smaller parts of the wing like bracketry and trailing edge thicknesses. |
| 01:44 | Ideally, we want a wing to have a round leading edge and a sharp trailing edge. |
| 01:49 | The trailing edge should be 2mm thick or less for optimal performance. |
| 01:54 | Detail work on the bracketry is things like putting aero profiles on brackets where possible, rounding off leading edges and minimizing steps to give the best performance. |
| 02:04 | It also comes down to things like selection of mounting of the main elements and tying the two elements together. |
| 02:09 | For example, is everything held together with swans or undermounts that made up the suction surfaces? Are the mounts bulky? Finally, adjustability is critical for a club level car, as we typically won't know exactly what the aero balance is on our car as we're building it, so we need to make sure you're prepared for all potential outcomes when we hit the track. |
| 02:30 | This means enough range of adjustability that we can balance out whatever's put at the front of the car, and that the wing performs well at all those adjustments. |
| 02:39 | Some wings, for example those with very aggressive second element curvature, will perform strongly at some angles and very weakly at others. |
| 02:47 | We also need to consider how easy it is to adjust the wing. |
| 02:51 | We want it to be quick enough that we can do it at the track without too much of a hassle. |
| 02:55 | These are all objectives that I aim for when designing a wing, and if we're purchasing something off the shelf, we should keep an eye out for these same things. |
| 03:03 | It can be tricky to sort out who's a reasonable supplier for a rear wing, as there are many options on the market, and all of them portray themselves as having a high-end product. |
| 03:13 | This gets complicated further when we have a manufacturer that offers both high-end and lower spec products. |
| 03:19 | For example, the popular APR GT series of wings is vastly different to their also popular GTC wings, and I have experienced significantly different performance when testing across these two different series. |
| 03:32 | There are a few things we can look at to help work out how performance oriented a wing is, though. |
| 03:37 | Firstly, look at the trailing edge. |
| 03:40 | Is it rounded with a big radius instead of sharp? Is there a huge amount of curvature still occurring at the rear of the airfoil? The answers to these questions are yes, you probably aren't looking at a high performance wing. |
| 03:53 | The next thing to look at is the CFD or wind tunnel data. |
| 03:56 | Any quality wing should have this data available. |
| 04:00 | Don't put too much weight into comparing numbers between manufacturers. |
| 04:03 | Different CFD settings and test conditions can massively exaggerate numbers here. |
| 04:08 | What we're looking for is A) Does the testing data exist? And B) Does the data make sense? For example, I saw a single element wing recently that claimed it was making 116kg at 100kmph, which would be SCZ 2.4. |
| 04:25 | But on the same chart, it also claimed 165kg at 200kmph and 256kg at 300kmph. |
| 04:33 | Which would be SCZ 0.85 and 0.59 respectively. |
| 04:40 | Now, all of these numbers clearly differ massively, in addition to 2.4 being unbelievably high and 0.59 being likely too low. |
| 04:49 | If I saw numbers like this, I wouldn't buy a wing from this company as there's clearly a problem in their simulations and they lack the aerodynamic experience to immediately see that problem at a glance. |
| 04:59 | Another thing to look for is if the absolute values of the numbers are reasonable. |
| 05:04 | A lift to drag ratio, also known as LOD, of up to 15 for a single element is possible on a car in low downforce scenarios, and an LOD over 30 is not. |
| 05:15 | Dual elements typically sit more around the LOD 6 mark. |
| 05:20 | Check the total downforce numbers too. |
| 05:22 | Single elements should be around SCZ 1 to 1.5, duals can go up to the mid 2s typically, or 3s if you have a very large 2 element wing that's being cranked super hard, but be wary of anyone claiming huge downforce numbers that are well in excess of those ballpark figures. |
| 05:39 | If you insist on making your own wing and not buying one from a manufacturer, then a good resource is the Airfoil Tools database, which you'll find linked below this module. |
| 05:49 | You can search any airfoil you're interested in here and it will give you lift and drag curves for the airfoil profile. |
| 05:55 | 9 times out of 10 though, what you'll end up going with is a Selig S1223 for a single element wing, or an MSHD as the first element for a dual element wing with a NACA 5312 as the second element. |
| 06:07 | It's not a perfect setup, but it'll get you 90% of the way there. |
| 06:12 | We've covered quite a bit in this module, so let's run back through the main points discussed. |
| 06:16 | At the club level, it's generally best to purchase a high quality rear wing from a reputable manufacturer to ensure good aerodynamic performance and structural integrity. |
| 06:26 | Key factors in differentiating a well -designed wing include the wing profile, detail work and adjustability. |
| 06:32 | A well-optimized wing offers a good balance between downforce and drag, while maintaining ease of adjustability at the track. |
| 06:39 | When evaluating wings, check for reliable CFD or wind tunnel data and be cautious of exaggerated or inconsistent performance claims from manufacturers. |
