davidl

iTrader: (40)

That's cool. And thank you for mentioning that shortening the cord length would help. I got my scissors ready to go, tomorrow.

30Tooth

iTrader: (1)

If you can copy the bottom shape it would be better, see the straight section is the tail and not the leading edge? Also that it looks like a RC wing backwards? That's why I call RC wings air dams. If you need help just ask.

belewis01

iTrader: (5)

Is this something that can be analyzed in Flowsquare? Coming from the RC sailplane hobby, a lot of effort was made to optimize airfoils for performance, and I often wondered about the impact and effectiveness of a true foil for RC cars. My gut feeling is that given the cord size and the Reynolds numbers associated, it would probably not be worth the effort to create and use true airfoiled wings for Touring Cars.

Interesting point about the PF Cadillac body, I too tried that body last weekend, and it was noticeably better than my old body. When I set the 2 bodies side by side, the profiles from the front wheels back were almost identical. The front fascias were slightly different, with the Caddy having a more vertical profile. When I get a chance, I'd like to compare the PF Caddy to one of the current top TC bodies available. Given the multiple rules and strict dimensions for TC bodies, I wonder if they are all very close in profile - pick a shape that works and tweak the appearance for a different product line.

davidl

iTrader: (40)

Little short story, my first introduction to a large, national level rc car race was the Winter Champs at Grand Rapids, MI in 1988. They had two classes, 1/12 scale stock and 1/12 scale modified. All the total best of the US were there to run, including Joel "Magic" Johnson, Cliff Lett, Tony Niesenger, and the list goes on and on. There was an I main in mod and a U main in stock for over 400 drivers.

I had been messing with some composite guys in indy that did Indy cars. They built the composite chassis for Longhorn Racing that Al Unser ran for one lap in the 1980 Indy 500. Well, they made me two wings with the cord you pictured from a small carbon fiber layup and I took them to Grand Rapids. I gave one to Chris Dosek to run in mod and he mounted it on his TOJ body, including cutting out all of the back of that body to remove any upward lip and make room for this wing. He qualified second behind Mike Blackstock and finished second behind Joel Johnson. It was by far the best Corally chassis on the track that weekend.

30Tooth

iTrader: (1)

I agree with you, no sense in trying to perfect an airfoil because of how small they are, maybe if we pursue double deck wings we could get some good numbers... Getting the shape moderately right is enough, there's more to tackle like size, AoA and placement.
It's not that the dimensions are strict, just that it could be better understood. A smooth flowing body will have better flow (I mean the advantage of directing air flow to where we want) that one that is aggressive, like the current TC bodies.

That's very cool! I will try making one with my 3d printer

iliveonnitro

Does the rear of the car not go turbulent? I would expect, especially on a straight, the air would be turbulent behind the car. I'm guessing the software you have isn't that complicated, though.

This would be where most of the gains could be made (i'll post on that in a minute).

iliveonnitro

Mechanical engineer here, so this area is one of my interests.

Drag typically increases when flow goes from laminar to turbulent (granted, there are ways to make turbulent flow cause less drag, but that's not often the case with automotive speeds). I would think, at this scale and speed, turbulent air behind and under the car would be the biggest source of improvement for aerodynamics.

This is why, eg, a sedan has better fuel economy than the exact same version of the car made into a hatchback. If you ran the hatchback in reverse, you'd often reduce the coefficient of drag.

For example, a teardrop has better aerodynamics when the rounded end is facing the wind and worse drag when the pointed end is facing the wind.





Image behind an SUV (too large to attach in this thread): https://i.stack.imgur.com/zAYgb.jpg

Here's a decent video from MIT: https://www.youtube.com/watch?v=TKH1DyV9vNU

or this article: Aerodynamics - Introduction to the science of air flow

I would think that finding a way to round off the back into more of an airfoil shape would be best. Also, remove any mirrors if your car has them and make sure the wheels are smooth. The lowest frontal area is also important.

30Tooth

iTrader: (1)

I think it does, been thinking about it because the SW possibly only sees that in a 2d way, meaning the airflow on the sides doesn't exist. But take a look at this http://www.youtube.com/watch?v=fco87iQHilY

Thanks for your input!
Here mine from what I've been learning:
1- teardrop shapes are indeed the best! One with a Kamm tail is what I seem to aim for, unknowingly. Same about frontal area.
2- the rear wheels should be tucked in more than the front ones. I never thought that, current RC bodyshells are opposite of that.
3- rear wing AoA are too extreme and ill designed.
4- sharp edges blocking airflow on the body and underside.

Tackling those challenges isn't difficult but for me it's time consuming testing one change in the front and hoping it doesn't create havoc in the rear...

For example I'm "stuck" at the front splitter design, I have more validation now from the links and pics you posted, should unlock more potential.

BTW, while I have your attention I want to ask you something. Do vortexes have more drag than turbulent air? Speaking of canard induced and boot corner vortexes.

wtcc

iTrader: (2)

My recommendation would be to design a body without a front splitter. The splitter should be part of the undertray. Like this the efficiency of the floor is increased and you don't have to think of a way to close the gap between splitter and floor/bumper...

30Tooth

iTrader: (1)

Almost there! I though about doing a 3d printed front bumper lower support like the pic. A proper diffuser. Way easier than a tray, what you reckon?

stormridersp

Looking at these pictures of the aero simulations made me think that there might be a big flaw in the general concept. In the pictures, everyone assumes that the bodyshell/chassis is a solid body, when in fact, it's a hollow shell. One other thing is the fact that these are all 2d simulations, and as so, they should be made taking different parallel slices of the most important aero features of he bodyshell and simulating them individually.

davidl

iTrader: (40)

I agree with your points, but take it from another perspective. I run a 1/8 fuel onroad car that is regularly down the straight at 65 MPH. The debate is to run the light weight body in lieu of the heavier weight so there is a lower CG in the chassis. I run faster with the heavy weight body and I believe the reason is that the aero features of the body stay more true at those speeds and the aero performance out shines the LCG. And there is probably even more to this story than a small comment on a forum.

AMZ

iTrader: (6)

...and 'side force' , probably a whole other conversation.

niznai

Not sure if you mean a 1/8 pan car or not, but from my experience (1/8 pan) I agree with your comments. Running the lightweight body is a waste of time.

I run a Capricorn and we see the same speeds on the main straight. A lightweight body will flap around everywhere, so I gave up and used normal weight. That is a lot more stable. Some people use CF stiffeners, and I guess it works, but I see that as an unnecessary complication when you have a normal weight body available.

I ahve seen no adverse effect from the CG change (not that I am any expert).

davidl

iTrader: (40)

I run the XRAY RX8 chassis and use the side stiffeners even on the normal weight body. By using the normal weight body, my car did not require any additional weight to make minimum at a national level race. That was nice.