Generic question to which I can't seem to find any answer.

I race my MGA (roadster) in vintage events. The car has maybe 100 HP so to try to make a pass (emphasis on "try"), I need to try to draft the car in front. I don't want to be right on his bumper as in NASCAR or Miata Racing due to the 13/13 rule in vintage racing. The 13/13 rule says that if you have contact that is your fault, you are placed on probation for 13 months; and if you have a repeat offense within the 13 months, you are suspended for 13 months across all vintage clubs in the US. So, given the rule - and especially the much greater value of the other cars running - it doesn't make sense to have inadvertent contact.

So at best, I'm 1/2 car length to say maybe 3 car lengths behind. And I usually place my car about 1/2 car width to the side, like the second goose in a flight of geese, especially when I'm close.

My questions: How far behind the car in front might I still be getting the benefit of a draft? e.g., If I'm three car lengths back, have I lost all benefit? Is there some sort of formula? And do I get any advantage at all if I stay 1/2 car length to the outside as opposed to being directly behind the car in front?

 

If you're trying to maximize the effect, being directly behind would be most beneficial. The effectiveness I figure would depend on how big of a shape the car you're trying to draft is, as well as what speed they are at, which should effect how big their "wake" is, if I'm using the correct terminology?

 

KOS, I agree that being directly behind is best - but how close before the draft effect is lost. If I'm 2 or 3 car lengths back, am I wasting my time

In qualifying for the big weekend vintage events at Lime Rock, I've sometimes just drafted behind my usual Nemesis with the idea that we would both have better starting positions relative to the other competition, rather than try to fight to pass him.

I hoping for some insight, however, as to how best to do it under race conditions - or at least how effective, if any, my technique might actually be.

 

Starting at about 10 cars you will see some benefit as you get closer that benefit is bigger. You need to be directly behind as any movement to the side you will be into both stagnant and turbulent air and the wall will be big. like a lot of things in life, Get directly behind and don’t pull out until the last minute.

 

I don’t know the shape or speed of your car but in spec Miata I don’t See any benefits beyond 3 feet. Of course we are 115hp on a good day but when bump drafting at a place like Sebring it can add 5-7 MPH on a long straight. That’s of course bump drafting where the rear car ispushing the front car.

In WRL racing we can’t make contact so I spend time moving around and creating confusion, almost think you may just do your best to be a distraction and cause a mistake.

 

Thank you both. Disparate opinions. Of course, if I am 10 car lengths behind, I'm unlikely to make up the gap. And in my racing, we also aren't allowed contact, so 3 feet is a bit too close for my comfort level. I can maybe get to 6 feet, but worry about the car in front braking and that is why I tend to run a half car length to the side. My car is a MGA, so similar in size and shape to a Miata - and even less HP.

 

Here is a good demo of how tight the draft must be. These guys get really clinical at about 7:00 minutes.

 

Thanks Miamirice.

That was just about the best track video ever! Thanks for sharing. Of course, I'm not good enough to do any of that! But if I can learn the necessary language of drafting and the hand signals, I'll pretend when I go to the bar.