Why didn't anybody use a flat underbody with venturi tunnels?

FninjaP90 · #1 09-05-2006, 04:19 AM

So, why didn't anybody incorporate this into their design this year? Does full-scale car aerodynamics play the same role in 1/10th scale? If so, it should provide downforce without the need for large wings and would almost eliminate the danger of a lift-off and crash.

Pressure regions on the Ferrari F430

Underbody of Ferrari Enzo

Making an airtight body with a flat underbody with venturis would be easy. All you need is some spare aluminum or lexan sheet to fabricate with and to fill the gaps in the front/rear/sides between an R/C chassis and the lexan body. I'd imagine the issue of running air through the motors/electonics to cool them wouldn't matter much in a single speed run as they would in an A-main.

It seems that Aerodynamics are the major hurdle with these speed records, since motor and battery power are essentially limitless and Nic Case proved that foam tires hold up at 160mph. Maybe I'll enter a 6hp brushless with a full aero body next year

balang_479 · #2 09-05-2006, 04:36 AM

yeah thats true, my dad equipped a flat underchassis and venturi holes on his and also put droop down side skirts and he said he could do the entire local track flat out without letting off an inch the throttle because there was so much downforce, car was glued to the track... but then again speed was reduced so you would have to test it for maximum speed and dowforce which may take a bit...

Adanmtxt1 · #3 09-05-2006, 10:55 AM

You mean everyone just stuffed a lot of power into a chassis and didn't optimize aerodynamics?!!! Lol! I cannot talk badly because I didn't enter, but managing the airflow about the car is very, very important if you want a fast and safe car. Making a flat bottom alone would increase performance, not to mention tunnels and careful ducting. It is somewhat limited as to what we can do, but if we can make everything just a little more efficient, you can achieve a big return.

Mini-TBasher55 · #4 09-05-2006, 05:12 PM

Quote:

Originally Posted by Adanmtxt1

You mean everyone just stuffed a lot of power into a chassis and didn't optimize aerodynamics?!!!

From what I saw, most of the serious entrees were very well thought out. Almost all of them tried to be as aerodynamic as possible, and some even windtunnel tested. Tony Phalen's 18T had a very aerodynamic body. I of course woulda slammed a Mamba with Lipos in a M18 and see how fast I could get!

FninjaP90 · #5 09-05-2006, 07:42 PM

IMO, the top of the chassis isn't very hard to make aerodynamic, with all the lexan bodies out there already. The bottom is the killer in RC cars though, because all that unsealed crap causes a lot of turbulence.

Adanmtxt1 · #6 09-09-2006, 03:35 PM

Quote:

Originally Posted by Mini-TBasher55

From what I saw, most of the serious entrees were very well thought out. Almost all of them tried to be as aerodynamic as possible, and some even windtunnel tested. Tony Phalen's 18T had a very aerodynamic body. I of course woulda slammed a Mamba with Lipos in a M18 and see how fast I could get!

Yeah, but the thing about aerodynamic (or laminar) flow is that in order to be as efficient as possible, you need to take into account every path the air will flow. Something as simply as making the chassis out of a flat and uninterrupted plate of carbon fiber would decrease the drag measurably. What can be done, then, to aid cooling? Something called ducting, using low-drag ducts to direct airflow to a certain area (the engine) without disturbing the airflow about the car. You can also manage airflow by instituting fins (like those vertical ones at the rear of the Ferrari). Simply put, having a good body doesn't do aerodynamics (or anything else

) justice. This is part of the reason F1 is so darn expensive.

A4DTM · #7 09-10-2006, 12:00 AM

http://www.geocities.com/dave_beeby/aero

LongRat · #8 09-16-2006, 03:32 PM

That's my website in that link above. Amazing coincidence.
I was just looking over this forum after months not reading it. I see the results are extremely impressive. The car I built looks a bit old tech now doesn't it. RC2400 NiCds! :>:> It would have been fun to enter it anyway! As for aerodynamics, I'm pretty sure the undertay is the way to go. You may even be able to do without any downforce-providing devices on the top of the car if the undertray is designed 'extreme' enough. That was my ultimate goal.

Cheers
DAVE

PocketAce · #9 09-16-2006, 07:49 PM

Because it's too hard to make a big chassis, that can seal everything, AND that's light.

USATorque55 · #10 09-17-2006, 01:44 AM

Its possible we'll see some guys who know how to form carbon fiber, imagine how that would be. a completely ducted and sculpted molded chassis that was designed for a certain type of body.

PocketAce · #11 09-17-2006, 06:43 PM

Quote:

Originally Posted by USATorque55

Its possible we'll see some guys who know how to form carbon fiber, imagine how that would be. a completely ducted and sculpted molded chassis that was designed for a certain type of body.

That's something completely professional. It can be done, but it is too out of reach for me or most of the amateur hobbyst's. And that guy would need to find a way to seal the body on the chassis, then seal the chassis to the floor (Skirts). That's hard work, mate!

LongRat · #12 09-18-2006, 04:51 AM

I don't think it would be a huge problem. There are thousands of RC glider enthusiasts who mould their own fibreglass and carbon wings. The materials are easy to get and the skills are posted all over the web. It would not be too hard to make a wooden model of the desired undertray, and mould sheet material over it.

jhbronx · #13 09-26-2006, 12:04 AM

I believe Team Associated's Cliff Lett made a RC10 pan car with a carbon fiber under body about 10 or 15 years ago. It was reported in Car Action magazine. He was at one of those velodrome races trying to make a speed record attempt. But the car somehow managed to get airborne a few times. I've seen some sick looking car come from those speed attempts I wish I had back issues or pictures.

furnik28 · #14 09-26-2006, 08:01 AM

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jhbronx · #16 09-27-2006, 08:30 AM

Hahahaha, yeah that's it! 1,000 mah cells. lol. Man those cars still look awsome. I don't remember how he mounted the batteries in that one on the top.

It would be nice to see a car using side skirts, side ducts, an air dam and splitter in the design.

jhbronx · #17 10-04-2006, 03:57 PM

I just realized if you use a chassis with an fully independent adjustable suspension it wouldn't be possible to adjust it accurately for toe in, droop, and front and rear track with a flat underbody chassis. Unless the chassis was two piece in design. Ughhh...... this is gonna be a pain in the butt.

PocketAce · #18 10-04-2006, 11:37 PM

Don't need to be a flat chassis. Use a very thin removeable plexiglass underbody cover or a also removeable but thick undrebody cover in lexan. You could secure and seal everything with some, I dunno, silicone, after you tuned everything right. Turn the car on, and secure the body on place with something like this, some tape. Use it in a carbon fiber chassis and it could be quite light. You guys are right, it is quite possible. Heat up plastic and it can assume any shape that you want. Heat it too much and it can burn and smell horrible, turning into a black cloud of death around your garage...

jhbronx · #19 10-05-2006, 12:18 AM

Quote:

Originally Posted by PocketAce

Don't need to be a flat chassis. Use a very thin removeable plexiglass underbody cover or a also removeable but thick undrebody cover in lexan. You could secure and seal everything with some, I dunno, silicone, after you tuned everything right. Turn the car on, and secure the body on place with something like this, some tape. Use it in a carbon fiber chassis and it could be quite light. You guys are right, it is quite possible. Heat up plastic and it can assume any shape that you want. Heat it too much and it can burn and smell horrible, turning into a black cloud of death around your garage...

With the exception of the venturi tunnels, if the chassis isn't flat then what shape would it be? I don't know if I would want to use silicon to secure the body to the chassis. You would have to tear the body apart just to charge or replace the batteries, perform maintence or make adjustments to the suspension. But, I like your concept of being able to bolt it on to a main chassis. I'd prefer a stronger material more impervious to side impact.

The problem I think a lot of these flat under bodies have is when the car hits a bump the front end develops a higher rack angle which causes lift, like when you stick your hand out of a car window at an angle. I think properly placed fans would further reduce pressure under the chassis and keep it low. It's just a guess, I don't know anything about aerodynamics.

Adanmtxt1 · #20 10-05-2006, 04:35 PM

When we say 'flat', we mean with no cutouts for anything. It allows air to flow unobstructed.

PocketAce · #21 10-05-2006, 07:32 PM

That's why the silicone. Seal that body to the underbody, put no holes on the body shell, turn the car on and seal it really nice. If you do things right it can get pretty flat under the body. It is still removeable for tunning. If you design all the bolt-on underbody parts correctly, you could easly build venturi tunnels on the rear and front panels. And switch between different venturi designs with ease. Or, if you're using a modified carbon fiber chassis, make it tubular, but with holes to make it light but so that you could BOLT a one-piece underbody made in anything that you want, even carbon fiber, if you don't trust plexiglass or a thick chunk of lexan. I'm telling ya, do it right and it could be simple but still as smooth as a babie's butt.

PocketAce · #22 10-05-2006, 07:34 PM

Quote:

Originally Posted by jhbronx

...I think properly placed fans would further reduce pressure under the chassis and keep it low...

I like the fans idea. Keeping everything light is the only problem.

jhbronx · #23 10-05-2006, 11:32 PM

The things with fans though, is that it would need ducting and a place to vent, otherwise what you suck in might cause a mess inside your car, llike a track vacuum cleaner.

Sigurd Ruschkow · #24 11-09-2006, 03:28 AM

For my car from 2004, I used a completely flat bottom - excepth for the wheel cut outs - together with a Venturi tunnel.

(batteries were placed at the front as an experiment)

The Venturi tunnel can be seen on
http://www.ruschkowski.se/images/F1000026.JPG

Sigurd

Mod Man · #25 02-01-2007, 10:02 PM

Here's the flat bottom of my FT TC4.

http://forums.radiocontrolzone.com/s...d.php?t=227918

It is light. It is made out of 3mm thick CF/PLY laminate. It weighs less than the same pice in 1.5mm solid carbon and is stiffer than the stock chassis.

The Vette C6 body Velcros around the edge.

Matt