Stuck open fuel flaps and why do they open in that direction

[ReubenG]

When Mark Webber's fuel flap stuck open in the Bahrain GP, the commentators generally commented on the extra aero drag this caused. I noticed that the refuelling cover flab has the hinge at the rear, i.e if the locking/ closing mechanism which holds it shut during normal racing fails, then normal air flow will push the flap open and hold it there.

My question is as follows (and it's a bit long - please bear with me):
Good engineering designs allow for failure and make sure that failure of a device places the system in the safest [best] configuration. In the context of a valve controlling cooling flow to a nuclear reactor, the safe position for the valve to fail in is open so that cooling is not lost the event of failure. So back to the fueling flap on F1 cars: If the hinge is at the back, and the closing mechanism fails, the flap sticks in the open position => the extra drag is highly undesirable in racing. Does anyone care to estimate what this extra drag does to lap times? I am struggling to think of a safety reason why it is better for the flap to be open than shut. The driver probably has to return to the pits to have it fixed, which is a huge time penalty.

If the hinge was towards the front of the flap, normal air flow would keep the flap shut even if the locking mechanism failed (unless there was a very low pressure region over that bodywork which I don't believe is true as it would reduce downforce). The only time this would afffect normal running is during a pitstop to refuel, when a mechanic would have to manually open the flap (time penalty ~< 2 sec) before refuelling can start.

IMO, the time penalty due to extra drag from the a rear hinged flap stuck open is far greater than the time taken to open a front hinged flap during the pit stop. So why do the teams put the hinge flap at the rear? I had a look through the regulations (albeit the 2004 regs - still downloading 2007) and couldn't find any reference to the position / direction of the fuel flap hinge.

Is there a more detailed set of regulations that dictates the position of the flap hinge? Can anyone think of any reasons why the flap hinge is at the rear instead of the front ?

[DaveKillens]

This type of configuration places the flap between the fuelling connection and the hot exhaust. Normal practice is to place a barrier between these points during refuelling, and this flap is another barrier. If it was reversed, in event of a splash the fuel could be directed towards the exhaust, a much worse safety scenario.

[joseff]

The size of the flap does nothing to block the flow of fuel over the exhaust. But yeah the RB design looks non-optimal.

When refueling, the fuel man will hold the nozzle by the sides. This way, the flap is blocking his left hand. A better solution would be something with the hinge at the bottom, allowing proper hand placement. Or better, a sliding door.

In the end, the most likely reason for the design is packaging. Maybe they simply have no room for the hinge elsewhere.

[RH1300S]

A fair question..........

I would hazard a guess that a flap with a front hinge would be more likely to hinder the fuel rig as the car arrives. Fractions of a second count and the fueller would be slightly un-sighted, also may have to lift the rig a tad higher as the car arrives. A mis-cued nozzle MIGHT even slam it shut.

So I suppose is the "fail-safe" judgement to guess a bigger risk in the above scenario or the lost time on track if the mechanism fails?

I thought I had seen some cars with a top hinge - but cannot find any pics to verify.

[nae]

is the fuel flap no tied in with the pit lane speed limiter, hence the bright colour underneath.

regardless it is a rather minor problem for a team to solve (or fail to solve time and time again)

[zac510]

I was asking the same question on anothe forum although I was suggesting that they build a fail safe mode into it that caused it to break in the event it gets stuck in the 'up' position. Got a few flames for that!

I do recall the Ferrari a few yearsa ago having a hinge that moved the flap to a position parallel to the surrounding bodywork.

It sure is odd that such a highly engineered vehicle does not seem to be optimised in this area.

[zac510]

is the fuel flap no tied in with the pit lane speed limiter, hence the bright colour underneath.

regardless it is a rather minor problem for a team to solve (or fail to solve time and time again)

Problem for Webber is that the actuator fails to open it then something else breaks (probably a return spring) when they lever it open at the fuel stop. From then on the air outside the car pulls the flap open.

[Tom]

I think the Newey fuel flap was famous for swiveling out. A solenoid pushed the whole flap out by a few cm and then a spindle on the top left of the flap (viewed from off-side) twisted the whole thing out the way. This looked like the design on the side of Webber's car. I don't think it had as much effect as the comentators suggested but it did make a nice mess of the winglet on the side of the airbox. I noticed Roseburg still had a bit attached to his nose cone at the end of the race.

[zac510]

No offence Tom but I think you'll find you are wrong with regard to the design of the RBR3.

[nae]

what its does show is that simple design decisions are in fact anything but.

and what was the 'horns' dong falling of webbos car. that a result of the fuel flap or just a co-incidence.

[BSO_Cards]

my guess is if the hydraulic fails and the wind closes the flap, it would be pretty damn hard to open it when he comes in to pit

[mx_tifoso]

my guess is if the hydraulic fails and the wind closes the flap, it would be pretty damn hard to open it when he comes in to pit

Maybe a good ol' scewdriver might help in that case, if you had to resort to that type of a resolution. Although it would possibly extend your stop by a few seconds. And then the you would have the problem of closing it again.