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#1 ptmac3

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Posted Dec 20 2010 - 12:52 PM

Yesterday I was in an online race at Le Mans Sarthe using the 67GT Mod. I was in a Ferrari and managed to catch a tow down Mulsanne behind a MKIV. The MKIV was 200 yards in front of me (according to Pribluda) and I still had a tow from it. That's 600 feet! Or twice the length of a football (US) field! Is that realistic? I've recently experienced the same thing in a race at Reims using the 65 mod. And the car in front doesn't seem to speed up or if it does it's barely perceptible. Certainly makes it easier to pass someone down a straight, but doesn't seem realistic, or is it? I remember in the original 67 cars, before any mods came out, being able to catch a tow behind another car at the Grenzlandring, but one had to be almost within shouting distance before catching a tow and the car in front went faster too, as it should be. Thoughts?

#2 FloP

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Posted Dec 20 2010 - 01:27 PM

It's the original model that was/is considered the most unrealistic of all. On the other hand, I think the latest version of the 1969 mod uses a draft model that some think goes a bit too far, i.e. it's too strong and reaches too far. That still leaves the '65 and GT mods (among others) that should be as close as is currently possible. I'm not sure about the effect on the car in front, though. :wave:

#3 TvO - guest

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Posted Dec 20 2010 - 02:30 PM

View Postptmac3, on Dec 20 2010 - 12:52 PM, said:

... I remember in the original 67 cars, before any mods came out, being able to catch a tow behind another car at the Grenzlandring, but one had to be almost within shouting distance before catching a tow and the car in front went faster too, as it should be. Thoughts?

Well, that is not how it should be, as discussed many times at RSC when the 1966 mod came out. I'm actually surprised that it's mostly Americans who seem to think the above, when they have such highspeel oval events like the Daytona 500 and Indy 500 to watch it in action. Apperantly, teams running a car in the Indy 500 have to take into account that the car can experience a decrease in drag when it's as much as 9 seconds behind the leading car.

My own experience is driving 2 seconds behind a big truck can increase fuel efficiency a little bit, am I'm not pulling as much revs (automatic three speed). Also, I have a racing bike on which I practice at summers. When a car passed I can still feel the effect more than 25 yards away and this is with a speed of about 20-25 mph. In fact, slipstreaming is the whole point in cycling. That's why the Tour de France is won in the mountains and not on the flat roads. And remember drag increases exponentially with speed.

Tommie.

#4 brr

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Posted Dec 20 2010 - 02:52 PM

View PostTvO, on Dec 20 2010 - 02:30 PM, said:

Apperantly, teams running a car in the Indy 500 have to take into account that the car can experience a decrease in drag when it's as much as 9 seconds behind the leading car.

What is the source of this information?

#5 Rudy Dingemans

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Posted Dec 20 2010 - 03:14 PM

View PostFloP, on Dec 20 2010 - 01:27 PM, said:

It's the original model that was/is considered the most unrealistic of all. On the other hand, I think the latest version of the 1969 mod uses a draft model that some think goes a bit too far, i.e. it's too strong and reaches too far. That still leaves the '65

No, '65 after the latest patch became too strong as well, as did 66 (although a bit less). For the small cars of 65, draft should be a bit less powerful, but it wasn't (in general). The characteristics of the later mods' slipstream were better overall, only the draft effect didn't reduce enough over distance, making it too strong at large distances.

Regards, Rudy
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#6 Pedro

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Posted Dec 20 2010 - 03:36 PM

I think it makes it all more interesting.
In race's there is more overtaking :)

#7 TvO - guest

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Posted Dec 20 2010 - 04:31 PM

View Postbrr, on Dec 20 2010 - 02:52 PM, said:

View PostTvO, on Dec 20 2010 - 02:30 PM, said:

Apperantly, teams running a car in the Indy 500 have to take into account that the car can experience a decrease in drag when it's as much as 9 seconds behind the leading car.

What is the source of this information?

My head :) . Someone posted this fact at RSC but it's long gone.

View PostRudy Dingemans, on Dec 20 2010 - 03:14 PM, said:

View PostFloP, on Dec 20 2010 - 01:27 PM, said:

It's the original model that was/is considered the most unrealistic of all. On the other hand, I think the latest version of the 1969 mod uses a draft model that some think goes a bit too far, i.e. it's too strong and reaches too far. That still leaves the '65

No, '65 after the latest patch became too strong as well, as did 66 (although a bit less). For the small cars of 65, draft should be a bit less powerful, but it wasn't (in general). The characteristics of the later mods' slipstream were better overall, only the draft effect didn't reduce enough over distance, making it too strong at large distances.

Regards, Rudy
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Why should it be weakened? Where does all this sceptisism come from?

The F2 mod is going to have the same slipstream as the 1966, 1965 and Sportscar mods. It's the only slipstream model which accurately reflects what happened in the races, whether it was 1966 Reims, 1967 F2 Reims, 1967 F2 Enna, 1967 F2 Hockenheim or anywhere else. On these tracks cars race bunched together in a pack just like in real life.

#8 ptmac3

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Posted Dec 20 2010 - 04:52 PM

View PostTvO, on Dec 20 2010 - 02:30 PM, said:

View Postptmac3, on Dec 20 2010 - 12:52 PM, said:

... I remember in the original 67 cars, before any mods came out, being able to catch a tow behind another car at the Grenzlandring, but one had to be almost within shouting distance before catching a tow and the car in front went faster too, as it should be. Thoughts?

Well, that is not how it should be, as discussed many times at RSC when the 1966 mod came out. I'm actually surprised that it's mostly Americans who seem to think the above, when they have such highspeel oval events like the Daytona 500 and Indy 500 to watch it in action.


So, youre saying that the lead car doesn't go faster? Please show me something in black and white that supports your statement. According to Wikipedia the lead vehicle goes faster too.


View PostTvO, on Dec 20 2010 - 02:30 PM, said:

Apperantly, teams running a car in the Indy 500 have to take into account that the car can experience a decrease in drag when it's as much as 9 seconds behind the leading car.

That sounds like you're saying that a car 9 seconds behind will experience a tow. At 200mph an Indy car covers the length of a football field or 300 feet in one second. At 9 seconds that would put the trailing car back 2700 feet or about 1/2 of a mile. That's quite far behind. Show me please.

#9 ptmac3

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Posted Dec 20 2010 - 05:07 PM

View PostRudy Dingemans, on Dec 20 2010 - 03:14 PM, said:

View PostFloP, on Dec 20 2010 - 01:27 PM, said:

It's the original model that was/is considered the most unrealistic of all. On the other hand, I think the latest version of the 1969 mod uses a draft model that some think goes a bit too far, i.e. it's too strong and reaches too far. That still leaves the '65

No, '65 after the latest patch became too strong as well, as did 66 (although a bit less). For the small cars of 65, draft should be a bit less powerful, but it wasn't (in general). The characteristics of the later mods' slipstream were better overall, only the draft effect didn't reduce enough over distance, making it too strong at large distances.

Regards, Rudy
(GPLRank: -40)

Too strong at large distances is exactly what I think.

#10 TvO - guest

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Posted Dec 20 2010 - 06:36 PM

[quote name='ptmac3' date='20 December 2010 - 11:52 PM' timestamp='1292885552' post='57039']
[quote name='TvO' date='20 December 2010 - 03:30 PM' timestamp='1292877002' post='57031']
[quote name='ptmac3' date='20 December 2010 - 07:52 PM' timestamp='1292871121' post='57028']
... I remember in the original 67 cars, before any mods came out, being able to catch a tow behind another car at the Grenzlandring, but one had to be almost within shouting distance before catching a tow and the car in front went faster too, as it should be. Thoughts?
[/quote]

Well, that is not how it should be, as discussed many times at RSC when the 1966 mod came out. I'm actually surprised that it's mostly Americans who seem to think the above, when they have such highspeel oval events like the Daytona 500 and Indy 500 to watch it in action.[/quote]

So, youre saying that the lead car doesn't go faster? Please show me something in black and white that supports your statement. According to [url="http://en.wikipedia.org/wiki/Drafting_%28aerodynamics%29#Simulation_of_drafting"]Wikipedia[/url] the lead vehicle goes faster too.[/quote]

Yes the lead vehicle does go faster. In GPL the lead vehicle also goes faster, also in the 1966 mod, 1965 mod, 1969 mod and GT mod. However you can't really tell when you're driving. The difference is maybe one or two mph while you are keeping your eye at the other guy trying to slipstream past you so you feel slower.


[quote name='ptmac3' date='20 December 2010 - 11:52 PM' timestamp='1292885552' post='57039']
[quote name='TvO' date='20 December 2010 - 03:30 PM' timestamp='1292877002' post='57031']Apperantly, teams running a car in the Indy 500 have to take into account that the car can experience a decrease in drag when it's as much as 9 seconds behind the leading car.[/quote]

That sounds like you're saying that a car 9 seconds behind will experience a tow. At 200mph an Indy car covers the length of a football field or 300 feet in one second. At 9 seconds that would put the trailing car back 2700 feet or about 1/2 of a mile. That's quite far behind. Show me please.
[/quote]

We all covered this long ago at RSC but unfortunately it's all gone except in a little part of my brain. I agree 9 seconds sound like a long way but for the 1966 mod we examined laptimes of cars at Reims when running alone, or in varying stages of proximity of another driver. There appeared to be an effect when running as much as 6 seconds back judging by the raw data of the laptimes, looking at Brabham vs. Bandini amongst others. After a lot of tweaking in GPL we came up with a slipstream which starts about 3 seconds back, which slowly builds up untill it reaches an effect just strong enough to pull the Brabham BT19 alongside of the Ferrari 312 before it has to tuck down again. We also managed to run the same relative laptimes draft vs. no draft compared to real life. The absolute value of the slipstream, i.e. 0 yards away from the guy in front, is about half of the value used in the original 1967's, and covered about four times the distance. The effect of this is rather than getting quite close and then suddenly getting sucked in so you can slingshot past, you gain enough slipstream to catch up to your opponent at high speed tracks usually within two laps, but you can't slingshot past as easily so you have to actually overtake rather than cruise by. This is also what happened at the races I mentioned earlier.

In short, you can be sure we did our homework on this one as well :thumbup: .

You will see when the F2 mod comes out just how well the draft really works. Because F2 races were shorter and cars were easier to handle, drivers pushed the cars even more to their limits as they did in F1. As a result laptimes driven in GPL are closer to those driven in real life. Pole and fastest lap at Hockenheim in GPL for example is almost creepy close to what we do in GPL. At almost all high speed races it was a dash for the win, like at Snetterton (same time for P1 and P2), Hockenheim (.3 between P1 and P2 in both heats), and Enna-Pergusa (top 3 within a second). Remember 1967 F2's are similar in performance compared to 1965 F1's, only more reliable.

Edited by TvO, Dec 20 2010 - 06:48 PM.


#11 Burnsy865

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Posted Dec 20 2010 - 07:01 PM

View PostPedro, on Dec 20 2010 - 03:36 PM, said:

I think it makes it all more interesting.
In race's there is more overtaking :)
:iconcur:

#12 SteveC43

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Posted Dec 20 2010 - 08:15 PM

View PostTvO, on Dec 20 2010 - 02:30 PM, said:

Apperantly, teams running a car in the Indy 500 have to take into account that the car can experience a decrease in drag when it's as much as 9 seconds behind the leading car.

I tried staying out of this, but that statement is so clearly a case of seeing what you want to see, I have to point it out.

First, you're comparing apples and oranges, i.e. a car that relies heavily on downforce to ones that placed a premium on smooth lines and low drag. What the Indy car guys are talking about is not tow. They are talking about turbulent air. This causes the car to move around and can also take some of the downforce, particularly on the front end of the car, away. They have to add more wing usually to overcome this as well as do some things to increase mechanical grip. It does not necessarily make them any faster. It is also not a good comparison to a smooth car as I'm sure the air behind wouldn't be nearly as turbulent and the car behind may or may not feel it as much as a car relying on the downforce is.

As for how it is in the sim, I'm over it. There are enough known inaccuracies in the GT mod to make them a bit more fun to drive, one more isn't that big a thing. If they did them realistically, I doubt any of us would drive them long as they would steer and brake like tug boats if the Daytona Prototype in iRacing is any indication.

#13 JCarvalho

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Posted Dec 20 2010 - 08:20 PM

As I recall, the increase in speed of the leading car is due to reduced drag on the back of the leading car, the two cars approach the physics of one vehicle when close enough. I thought the two cars had to be pretty close for this effect, however.

Jim

#14 SteveC43

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Posted Dec 20 2010 - 09:15 PM

View PostJCarvalho, on Dec 20 2010 - 08:20 PM, said:

As I recall, the increase in speed of the leading car is due to reduced drag on the back of the leading car, the two cars approach the physics of one vehicle when close enough. I thought the two cars had to be pretty close for this effect, however.

Jim

Yup. This is proven in NASCAR as the leading car will lose downforce on the rear and get "loose" when a car gets right on his bumper while the trailing car gets "tight" and understeers from lack of downforce on the front. That's why they have such a hard time running really closely on 1-1/2 mile tracks with lower banking than Daytona or Talledega. It's also why they tried the silly wing and the new car, but failed for the most part.  :punish: At Talledega and Daytona, it makes them fast and the more cars lined up like this, the faster they will be.

And yes, they have to be very close for this to work well.

One other thing to keep in mind is that today's cars are really spec racers with a difference of maybe 1 to 5 mph between them versus 25 or 30 mph like the GT mod.

Edited by SteveC43, Dec 20 2010 - 09:22 PM.


#15 Burnsy865

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Posted Dec 21 2010 - 12:04 AM

View PostSteveC43, on Dec 20 2010 - 09:15 PM, said:

One other thing to keep in mind is that today's cars are really spec racers with a difference of maybe 1 to 5 mph between them versus 25 or 30 mph like the GT mod.
Good point Steve. Getting towed by a much faster car probably wouldn't increase the car in fronts speed at all. I like the discusion here about what should be happening and what shouldn't be happening, as far as I am concerned, the GT mod team did a bloody fantastic job with a 11+ year old sim.




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