Raising a Trunk?

[freebeard]

Looks good. Do those tufts in the separation bubble persist as you pull over to the side of the road, or straighen?

Maybe a biplane spoiler? Or would you rasie the lid above the bottom of the window glass?

[JacobLeSann]

Here’s some better photos, looks like this wing is king! The separation bubble has been minimized quite a bit. I’m leaving for a 600km trip tomorrow, and will be happy to observe my mileage.

Was pretty funny at work and filling up at the pump today. I just tell people “just got married!”. Needs a couple cans out back. Somebody asked my girlfriend about the “sperms” on my car.

[JacobLeSann]

Bad news, didn’t get it all done before the sun went down. No tuft-test photos of this section of the build.

I like the look of the Fusion LSR, as well as several landspeed record cars I’ve seen. I made it even closer to the wings they use by adding a pair of spill plates. I think it looks funky and I like it. I understand the spill plates are for straight-line stability and can generate vortices as they slice through the air, but I put ‘em on anyway. I like em.

Iirc, I read through a rallycross aero article about wing design, and the wings that didn’t use any spill plates had poor performance, due to air falling off the ends. I wonder if that applies; I noticed consistent flow down the rear windshield as well as tufts converging from the C-pillars to the centre line of the rear glass. Either way, the flow is good indeed.


The stability seems improved as well. I don’t have my belly pan/airdam attached right now, and I noticed front end lift as well as oversteer at around 170 km/h turning a hard corner. On that same corner, I attacked harder and didn’t feel any lift off; front or rear.

Now to do it all again in coroplast! Big test run comes tomorrow morning!!

[JacobLeSann]

2nd pic was taken in Australia, sorry.

TL;DR: 46.7MPG tank average, 473 miles on 10 gallons of gas. That’s with some gas spent screwing around too.

Got it all done up, tested it out. Worked great, although I didn’t have daylight or time to observe the airflow down the sides. The flow down the rear glass was better, with the separation bubble minimized but still present. I ended up staying awake very late getting everything bolted/taped up, and noticed a rock (from where the car was parked) which had strange slime on it that looked familiar. With it all attached to the car, I went and checked over it all to inspect any mechanical issues before putting on my skid plate/front diffuser.

The axle had torn its boot and shot grease everywhere! The rock was a red herring. I stayed up all night thanks to that. Good fun. Pays to have a parts car.

Anyhow, the car is doing really good! I had spent something like 50-60km doing speed runs back and forth to test aero, and left town shot about 2/8 a tank. With all my current modifications I have gone 762km on 38 litres of gas. In Americanese, that’s 473 miles on 10 gallons. I still had more in the tank, but decided to fill up. So safe to say I can hit 800km with a bit of effort.

Stability is good too. I think the spill plates help some. I was behind a big truck wavering all over the road in crosswinds while I didn’t have to steer much at all. Great area to put stuff on while the car’s parked. Picnic table?

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freebeard, I have considered both the Sierra biplane spoiler and raising the lid. This car is supposed to be my daily driver while I build up custom aero-mobiles from my many 90’s civics. So basically I want this all to be removable. That almost rules out the biplane spoiler as it attaches to the C-pillar and needs careful reinforcement. Raising the deck is easier, removable, and in the cards. Visibility of the third brake light will be tricky.

[freebeard]

Great area to put stuff on while the car’s parked. Picnic table?

That's why Bruce Meyers had flat front fender tops on the Meyers Manx.

[cRiPpLe_rOoStEr]

Originally Posted by freebeard

That's why Bruce Meyers had flat front fender tops on the Meyers Manx.

I thought it was meant to roll some joints or sniff some 'caine...

Too small to double as a picnic table. Maybe could serve for some snacks as small as a peanut bag...

[freebeard]

Cans of beer.

[Vman455]

Originally Posted by JacobLeSann

I noticed a lot more pressure on the rear (the tufts are flowing much faster), and the tufts spun and fluttered all over the place. I’m not sure if that’s good or bad, but that seems bad.

Tufts don't show pressure. Even separated vs. attached tufts don't necessarily tell you anything about the pressure.

Deliberately separating the flow behind a roof spoiler on my car dropped the pressure over the rear window.

(Not deliberately) separating the flow on the same window in front of a large Hellcat spoiler raised the pressure, pretty significantly.

If you want to know what the pressure over your rear window looks like with various spoilers, you will need to measure it. Fortunately, that's easy to do. Get a Magnehelic or digital pressure gauge, some tubing, and make or buy a pressure disk. Then test lots of designs and see what happens.



I would also suggest using a variety of measurements if your goal is to see what a particular change does to the airflow over your car. Tufts will show you one facet. Pressure measurement another. When I thought about fitting a splitter to my car, I used 4 different tests (steering angle, tufts, pressure, coastdown) to try and get a complete picture.

[aerohead]

Without a technical image of the car, I have no reference as to 'where the car is' aerodynamically.
Dimensional analysis is a critical tool used in fluid mechanics.
A blueprint of the CIVIC would be a 'roadmap' of sorts.
If you were to develop a rear spoiler the way Porsche did for their 911 Carrera RS 2.7 'ducktail', you'd be looking at $94,000 just in wind tunnel time alone.

[JacobLeSann]

Woah, thank you Vman455. I was just considering trying different forms of testing as I seen your post just now. Other methods could be best in this case. I think I’m seeing the pattern of vortices coming off the c-pillar and the “down-wash” mentioned by aerohead. I plan to keep testing and I’ll check out your site in the meantime.

aerohead, I understand what you’re saying when it comes to the relationship of input cost versus output savings, whether it’s time or money. So far I’ve spent perhaps $5.00, haha. But I have not counted the man hours.

I will post some more detailed images/observations in the original thread for this car (for the sake of continuity). Will update when I do that.