NASA ST and a question about swan necks - 986 Forum - The Community for Porsche Boxster & Cayman Owners

The Radium King · 03-12-2019, 09:05 PM

so, building my car into a NASA ST-3 car for next year. anybody running NASA? question about rear bumper bars - my read is that you cannot remove or modify them?

and ...

if i gotta keep the damn thing, what do you think about hanging a chassis-mount swan-neck wing from where the bumper overriders attach? i could make it work easily enough, but am i just inviting someone to rear end me and f it all up?

Racer Boy · 03-13-2019, 07:28 AM

I'm unfamiliar with the NASA rules, but a good rule of thumb is to not have some kind of equipment that can get taken out easily by contact.

The Radium King · 03-13-2019, 07:55 AM

that's what i was thinking. in st-3 i'd have to run >100 TW DOT tires under 282 mm in width, so was looking for ways to get more traction in the back (i am putting a 3.6 in the car) however a standard wing will have to do.

regarding the rear bumper bar, the regs read:

Other than the listed exceptions, every Production vehicle must retain its unmodified:
1) OEM frame rails/rear frame cross beam, and/or Unibody, and Sub-
frames/suspension cross-members (in their OEM locations).

where some are interpreting 'rear frame cross beam' as the rear bumper bar. i'm trying to do my research before i ask, as when it comes to scrutineers it is sometimes a good idea to leave stones un-turned.

maytag · 03-13-2019, 08:32 AM

Huh... what's a "swan neck"?

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The Radium King · 03-13-2019, 08:44 AM

typically spoiler uprights attach to the bottom of the spoiler. a spoiler is an upside down wing and anything attached to that surface reduces the downforce generated. in a swan-neck wing, the uprights curve around (like a ... swan neck) and attach to the top of the wing instead. porsche is using one on the new gt4 clubsport. the swan neck approach also lets you mount the wing further back to increase the leverage of the downforce. given that the force is not directly down on the uprights anymore, there is now a torque action on the baseplates, so tuners have started mounting them to the chassis out the back of the car instead. not so good on a race car, however, where folks are always banging into you.

JayG · 03-13-2019, 10:19 AM

Has the aero been windtunnel tested?
If not, it could easily have an adverse effect on the performance

Lots of people hang a lot of crap on their cars assuming it will be beneficial

YMMV

The Radium King · 03-13-2019, 10:43 AM

apparently works for porsche ...

not sure if it's smog legal in california however.

truegearhead · 03-14-2019, 04:41 AM

NASA guy here. I run TT5 (same rules as ST5 and St-3 with less power). I don’t see anything not allowing swan necks and I know I’ve seen them. I only see the two limitations below in reference to wing design and rear bumber modification. I’ve also removed my rear bumber bar and cut my rear bumper cover and it passes tech. I also run a huge wing with 255s all around (which are also legal in ST3). The wing and splitter knocked off almost 2 seconds off my LapTimer at VIR. Right now it’s a spec boxster + aero and consistently runs time faster than the spec boxster lap record so that’s proof enough to me that the aero is worth it.

) Single rear wing or spoiler that does not exceed a height of 8” above the roof line, or width greater than the vehicle’s body width, or end plates greater than 12” in length or height, or 12” protrusion from the rear of the vehicle. Body width does not include flared fenders, mirrors, splitter, door handles.

Cutting/removal of the rear bumper cover/fascia where it does not cover the rear frame/bumper cross beam.

The Radium King · 03-14-2019, 08:37 AM

thanks - rules parallel between st and tt so if you can run without the bumper then i can too.

yes, not all of us can afford wind tunnels so proof is in lap times; most of the tt guys swear by them. needs front splitter and canards to offset the epic rear downforce however. you are probably seeing the chassis mount units in tt where there is no contact, however ...

truegearhead · 03-17-2019, 02:10 PM

Quote:

Originally Posted by The Radium King

thanks - rules parallel between st and tt so if you can run without the bumper then i can too.

yes, not all of us can afford wind tunnels so proof is in lap times; most of the tt guys swear by them. needs front splitter and canards to offset the epic rear downforce however. you are probably seeing the chassis mount units in tt where there is no contact, however ...

Canards are unfortunately not legal though.