This is just getting stupid, regardless of what is actually possible it is not done IRL R/C racing due to the danger it presents on a track which actually goes right. Sure if you put Nascar racers in R/C cars they'd bash into each other driving down the straight, but if you went and drove into the back of the average R/C racer he'd tell you to f*** off.

Quote from tristancliffe :

What on earth are you on about Vacuums. There won't be a vacuum. To get a draft all you need is a situation where the air pressure following a car is lower than the air pressure not following a car.

In an F1 car the air is thrown about, directed upward, eddy currents and vorticies are set up and what have you. All of this helps to create a lower pressure region behind the car.

What the F1 designers try to do is reduce this pressure drop (which they can't do completely), and increase the rate at which the low pressure region recovers - thus not allowing the following car to gain a draft. Add in to that that modern F1 cars are designed to work 'best' in clean, predictable air (like a CFD program can cope with), but loses efficiency in 'dirty', turbulent air, and you have a recipe for low draft, low overtaking situations.

Spouting nonsense about the air going upwards and therefore not creating a vacuum just makes you look silly. And if you look silly, your chances of convincing us that bumpdrafting is used to any great extent in real life are greatly diminshed.

Well, I didn't see a need to get technical and vacuum is what best describes a low pressure area, since there's nothing with less pressure than no pressure at all. No matter what you do with the air around the car, as soon as there is less air directly behind the car than there is elsewhere, that's a partial vacuum and that's a low pressure area... And that's the only way a low pressure area is created... Turbulent air (dirty air) is NOT a low pressure area, it's a variable pressure area... Where air molecules collide there is high pressure, where they've bounced off of eachother there's low pressure. That's why F1 cars are inefficient in dirty air, there's unequal pressure working on the wings and pushing against the car.

That's also how the wings of cars and planes work. Air sticks to a denser object when it flows passed it. So the longer part of a 2 sided wing will have the exact same amount of air stuck to it, over a larger area, which means there's less air in that area than the other side, which is a partial vacuum, which creates a lower pressure, which creates downforce, or lift, respectively. What actually happens is that the air molecules travel a larger distance in the same amount of time, but while it is being used to explain what happens it is totally irrelevant to the creation of lift or downforce. The speed of air molecules has nothing to do with air pressure, only the amount of air molecules in a certain area does.

And F1 designers not only try to create as small a pocket of low pressure as possible so others can't draft them... The smaller the low pressure area behind the car, the more pressure there is at the back of the car, which simply means the lower the drag of the car will be (and the faster it will go).

It's not nonsense Tristan, it's explaining what happens in an easier to understand way than you do. I've only barely managed to keep the damn golfball my teacher loved out of the discussion.

I never said great extend, just a lot more than "only in NASCAR"...
It happens a whole lot more than you guys want to believe... And less than you seem to think I want to prove...

Quote from ajp71 :

This is just getting stupid, regardless of what is actually possible it is not done IRL R/C racing due to the danger it presents on a track which actually goes right. Sure if you put Nascar racers in R/C cars they'd bash into each other driving down the straight, but if you went and drove into the back of the average R/C racer he'd tell you to f*** off.

Yes, this is getting stupid, because I will for the 3rd time tell you that not everybody thinks like you... There are plenty of RL racers that do not mind an occasional bumpdraft, as has been proven over and over again in this thread... You keep referring to BD as "bashing into eachother" which it is not.
Only in your mind is BD slamming other cars... I'll go look for that link to that vid...

Here it is... Examples of guys who don't mind bumpdrafting, and one who does mind bumpdrafting. http://www.lfsforum.net/showthread.php?p=29907#post29907
(it's a 25 minute video so take time watching it)

Quote from TagForce :

Where air molecules collide there is high pressure, where they've bounced off of eachother there's low pressure.

What has your teacher been doing? What a crazy way to describe it...

Quote from Tagforce :

That's why F1 cars are inefficient in dirty air, there's unequal pressure working on the wings and pushing against the car.

No, it's because they're designed to work with laminar airflow. The pressure differences across a real bit of laminar airflow (or laminar enough) make little difference.

Quote from TagForce :

That's also how the wings of cars and planes work. Air sticks to a denser object when it flows passed it.

What are you on. The air doesn't know or care how dense an object is. A wing is equally good make from foam than steel, and steel is less dense.

Quote from TagForce :

So the longer part of a 2 sided wing will have the exact same amount of air stuck to it, over a larger area, which means there's less air in that area than the other side, which is a partial vacuum, which creates a lower pressure, which creates downforce, or lift, respectively.

Was your teacher on drugs. The normal way to describe in extremely basic terms how wings work is to say that the air has to flow faster over one side (the longer side) than the other. Faster air means lower pressure, which means greater pressure difference = resultant force. This talk of air sticking to wings, and the same amount of air being spread over a bigger area is extremely weird.

Quote from TagForce :

What actually happens is that the air molecules travel a larger distance in the same amount of time, but while it is being used to explain what happens it is totally irrelevant to the creation of lift or downforce. The speed of air molecules has nothing to do with air pressure, only the amount of air molecules in a certain area does.

Erm, no. Velocity is directly linked to air pressure. If you had one mole of air (fixed number of molecules) at speed x they should have pressure z. Move said mole of air at y m/s and the pressure will drop from z. Same amount of air, just different speeds.

Quote from TagForce :

And F1 designers not only try to create as small a pocket of low pressure as possible so others can't draft them... The smaller the low pressure area behind the car, the more pressure there is at the back of the car, which simply means the lower the drag of the car will be (and the faster it will go).

Erm, in simple terms this is the closest you've been to being right. But the designers not only design to keep the low pressure region behind the car small and fast recovering, but also to maintain good air behaviour over all the wings, inhibit separation, and a whole host of other factors. You can't make something for nothing, and to generate lots of downforce you MUST create lots of drag. And lots of drag tends to mean lots of slipstream. If F1 front wings were less effected by 'dirty' air then most people wouldn't 'know' about vorticies.

So far you haven't convinced me of your understanding of aerodynamics, which I feel are an absolute must to have any definitive answer to bumpdrafting (the whole point of this topic). As it is, you are left with conjecture and the voice of one or two unknown American drivers who say that bumpdrafting happens. But so far no one has make a single convincing explanation that it exists.

Quote from TagForce :

Yes, this is getting stupid, because I will for the 3rd time tell you that not everybody thinks like you... There are plenty of RL racers that do not mind an occasional bumpdraft, as has been proven over and over again in this thread... You keep referring to BD as "bashing into eachother" which it is not.
Only in your mind is BD slamming other cars... I'll go look for that link to that vid...

Here it is... Examples of guys who don't mind bumpdrafting, and one who does mind bumpdrafting. http://www.lfsforum.net/showthread.php?p=29907#post29907
(it's a 25 minute video so take time watching it)

You may be able to find the odd video of cars bumpdrafting on a long straight on a R/C, but it is not normal to do it on a R/C, most UK racers have never heard of it and don't know what it is, it may work, but it's a technique that is not used on real life racetracks, simply because it's never occured to people to try it

The fact remains that accidents on straights can be some of the worst in cars not designed to take high speed impacts like any of todays professional racing cars. I have seen several big crashes on straights, simply because the speeds are greater there, I have seen accidents resulting in fairly bad injuries in road cars from contact on straights and I know there was the double fatality when two Cobra replicas hit each other on the straight at Cadwell recently.

It's more because doing something like bumpdrafting creates an uneccesary danger on a part of the track with no run off areas that most club racers will not consider playing games on the straights. There are a large number of people here who are connected to club racing in some way and who go about there racing in a completely different mind set to those who drive big powerful cars round in circles who know there's little danger posed to them due to all the safety devices in their cars, the simple fact is in a car which has only had simple safety mods like harnesses and a cage a 100 mph T-bone or slamming into a wall is likely to be a fatal accident, not just climbing out swearing a bit explaining to a TV camera why it wasn't your fault, picking your cheque and repeating it next week.

This arguement is ridiculous. There are enough differences in opinions to justify that you should not bumpdraft anyone but your buddies who want you to. You shouldn't say, "I'll bumpdraft unless you tell me to stop." You should NOT bumpdraft unless someone tells you to do it. It's like me saying I will break into your house and steal your computer since it's better than mine. But if you tell me you don't want me to, then I won't.

It is my understanding that in drafting in LFS, the front car does not get a push from the draft as they do IRL at say Daytona in Nascar. So, the 2nd car gets a big speed boost from the draft and it does nothing to the lead car. Therefore the speeds of the 2 cars are too great for proper bumpdrafting. It seems to me the 2nd car will bump, push the lead car ahead, then the lead will lose that momentum, back down and the 2nd car will bump again. This will continue and I don't call that bumpdrafting, I call it bashing the car in front. In Nascar on the big high speed tracks, bumpdrafting occurs because in the draft, BOTH cars are faster than one, not just the 2nd car. But the 2nd car can be SLIGHTLY faster than the 1st and can push the 1st car a bit making them both just a little faster. Not the big speed differences like we have in LFS since the 1st car does not get a speed advantage from drafting. Therefore, in LFS, bumpdrafting is too dangerous because the 2nd car is much too fast for it to be pushing the 1st. If you get the car slightly out of wack pushing the other, you can easily spin the 1st one.

And I saw a comment I think that in Nascar they bumpdraft because if they lift up on the throttle, then they loose momentum and the draft and get hung out to dry. Yes if they lift, they loose, but they do not lift, they just tap the brakes a bit to slow their momentum slightly if they can not pull out and pass or don't want to yet. They don't bumpdraft because they can't lift. They bumpdraft at Daytona and Talladega because of the restrictor plates restricting their speed and the team up to work together in a very long race to move to the front. It is expected at the big restrictor plate races and does not happen at the other tracks. Well, in the case of Bush spinning out I think it was Biffle at Lowes? they sometimes make excuses that they were trying to bumpdraft when in reality they spun out another car whether on purpose or by accident.

No doubt bumpdrafting is bad & dangerous in LFS with the aero model, control methods, lag and whatnots. I did have a great race earlier though on Bl1/XFG:
The leader ([Fluid] Parise) was getting away with Dizman in 2nd and me in 3rd. Upon exiting the chicane after T1 I was right behind P2 and asked (it's bound to a key now ) if I can BD. Affirmative answer meant we both significantly gained on the leader, and in fact, Parise was so busy finding the "lol" key to comment on the BD question that he pulled the next corner wide and we both overtook him

See, no probs!

Quote from NotAnIllusion :

No doubt bumpdrafting is bad & dangerous in LFS with the aero model, control methods, lag and whatnots. I did have a great race earlier though on Bl1/XFG:
The leader ([Fluid] Parise) was getting away with Dizman in 2nd and me in 3rd. Upon exiting the chicane after T1 I was right behind P2 and asked (it's bound to a key now ) if I can BD. Affirmative answer meant we both significantly gained on the leader, and in fact, Parise was so busy finding the "lol" key to comment on the BD question that he pulled the next corner wide and we both overtook him

See, no probs!

Now THAT I dont mind, if boths racers are up for it then if yer not in danger of going off into someone else then go for it. Just dont do it to me.

I think the argument on this topic is more to do with peoples interpretation of bump drafting. Mrodgers basically sums it up for me in that my interpretation of bump drafting is to do with the air flow and that they aren't just hitting each others bumpers to push them along faster.

Tristan is right on the R/C cars shell which will absorb the energy. I've never seen such a move done in real r/c racing and if someone ever tried that on me I'd be shouting at them to stop. Another factor is it's far to difficult to judge what the car in front is doing with such a rapid accleration. I remember hearing the stats of a Nitro 1/10th touring car R/C car and it could acclerate from 0-60 in 1second. That would be hard enough to follow with your eyes yet along while bumping into someone.

Keiran

Bumpdrafting blows. Period.

As much as I appreciate your well thought out posts supporting it, I hate it with an unadulterated passion when people do it to me in NR2003. Repeat: HATE IT!!!!!

It accomplishes little and just makes me nervous and angry at the same time. Not a good frame of mind to race with. Even real life NASCAR drivers acknowledge its pathetic risk-reward ratio.

So do me a favor when I'm on track: go do your kinky driving with someone else.

Quote from tristancliffe :

Now, about the bicycle. It's already been mentioned that the karts, bikes, R/C cars etc all generate low pressure regions behind them, and therefore slipstreams. It's a nature of objects travelling through fluids.

But a bicycle is powered by the legs. Legs get tired - engines don't. Any energy saved by slipstreaming will save the legs of that slipstreamer to give him a later advantage.The same occurs in NASCAR. NOT being the lead driver, I believe, can save you quite a lot of fuel being sucked along.

Now, if a bicycle tried to bumpdraft there would be a crash. But also the gain in speed isn't that much - it's more about saving energy, which is the square of speed. A kart isn't trying to save energy (except perhaps in an endurance race, like all cars), but trying to maximise it's speed. But the little gains of speed a draft are likely to have been mostly lost in the inelastic collision when two karts touch. R/C cars - I can imagine the body squashes and aborbs the energy rather than channel it purely into the velocity of the lead car.

*breathes out*

Yes, we understand the saved energy, which is why most NASCAR drivers use it. They have to run 200 laps, I run 15/20. I also understand the slipstream of a kart is very little, but when you add maritime winds to the equation, the slipstream effect only gets amplified. And even if the karts are geared differently, the Kart 2 will accerlate even faster from the draft of Kart 1. So if Kart 2 transfers that extra energy into Kart 1, then drafts him, and regains even more energy back, would you still not call that a bump draft?

Quote from NotAnIllusion :

No doubt bumpdrafting is bad & dangerous in LFS with the aero model, control methods, lag and whatnots. I did have a great race earlier though on Bl1/XFG:
The leader ([Fluid] Parise) was getting away with Dizman in 2nd and me in 3rd. Upon exiting the chicane after T1 I was right behind P2 and asked (it's bound to a key now ) if I can BD. Affirmative answer meant we both significantly gained on the leader, and in fact, Parise was so busy finding the "lol" key to comment on the BD question that he pulled the next corner wide and we both overtook him

See, no probs!

Yea, we were bump drafting too. That was some of the best racing that I ever did on demo. You guys were bump drafting trying to catch Parise, while I was driving the wheels of my XFG trying to catch you guys. Which was nearly impossible, until you started battling for position. Then it was an all out battle.

Quote from keiran :

I remember hearing the stats of a Nitro 1/10th touring car R/C car and it could acclerate from 0-60 in 1second. That would be hard enough to follow with your eyes yet along while bumping into someone.

Yea, I had a hard enough time driving mine in a straight line let alone bumping another down the back straight.