Aero trunk lid project

[Pendragon]

Originally Posted by California98Civic

The tape that I still have to use to seal the gaps and edges has damaged the paint job with sticky glue that I can't get off (yet). Bummer. Magnets hold it down via straps to the lid's underside. And I have tested the straps hold, but the tape seals gaps and smooths edges. I'm pausing this project until I'm better skilled in fabrication. I'll test the current build once I get the paint clean and devise a better way to seal gaps. Good luck with your efforts Brucepick. I'll be following. On to my airdam today after work and yard projects...

You might try some bug and tar remover with a soft cloth to remove the adhesive. If that does not get it all there may be a product at the drug store used to remove bandage adhesive from skin, but they usually come in the form of a wipe. If you wind up using rubbing alcohol, wash the area right away and put some wax on it as the alcohol tends to dry things out if left there to its own devices.

[California98Civic]

Thanks man. I was hoping for a pointer. Car's old but it doesn't look too crappy yet.

Cheers,
james

[brucepick]

Originally Posted by California98Civic

The tape that I still have to use to seal the gaps and edges has damaged the paint job with sticky glue that I can't get off (yet). Bummer. Magnets hold it down via straps to the lid's underside. And I have tested the straps hold, but the tape seals gaps and smooths edges. I'm pausing this project until I'm better skilled in fabrication. I'll test the current build once I get the paint clean and devise a better way to seal gaps. Good luck with your efforts Brucepick. I'll be following. On to my airdam today after work and yard projects...

Honestly, I haven't done a lick of work towards a trunk lid spoiler, beyond tossing some cardboard cartons in the garage for possible mockups, and of course all the design contemplation in these threads. However, I've been doing some work on the belly pan and future flat wheel covers.

As for removing the tape ick, try some Goo Gone. Hardware store, maybe also in WalMart and Home Depot. A yellow/gold fluid in a tall flat clear bottle. Works very well, but TEST IT first on a hidden spot, maybe the hood underside. I have not had it destroy any finishes but it is strong stuff. I've also used charcoal lighter fluid to get that sort of mess off painted surfaces, very successfully.

[Whitey]

Goo Gone is great (and it even smells good, too).

[ChazInMT]

Sorry to be so late in the game here. Seemed to me like the thing to build would be something like this if you have a notch back.



Unless you wanna go drag racing, but that's hell on fuel mileage, unless you pulse & glide....which is hell on your win loss record.

[ChazInMT]

Originally Posted by aerohead

California98Civic,with respect to the plan-taper of your car,I would establish the rate of curvature from your elevational view 'Template',using the height of the car,then transpose that curvature onto the plan-view of the Civic.
It looks like the body taper begins around where the center of the rear tires are.Try to dovetail onto that spot.
If you use too 'fast' a curvature on the sides,you'll lose your boundary layer and trash the airflow.
Also,you might set up attached longitudinal vortexes ( really high drag ) as the slow side flow intersects with the faster downwash coming off the roof.

I think Aeroheads tryin to say this.

[California98Civic]

Originally Posted by ChazInMT

Unless you wanna go drag racing, but that's hell on fuel mileage, unless you pulse & glide....which is hell on your win loss record.

Hahahaha! I saw this in your design phase, I think. Is this a photo as built? Got more pics? I might yet switch plans, having taken my lumps with the trunk lid idea. This seems an easier thing to build, and I now know how difficult it is to make a trunk lid that can still allow access to the trunk AND be effective.

[CFECO]

I was thinking, that "Follow the template always" may not be the best idea. If we had cars with the same front shape as the ideal, then yes, the rest should be as close to it as possible also. But since we have rounded off box shaped front ends, with setback windshields, the airflow will not match the ideal from the start, so I'm not sure the rest, always will either. Without a windtunnel, who knows? Back when I was doing cylinder head work, the flowbench showed me the air "wanted to go places" that I didn't always expect. A car with a blunt front end seems to like the waist area pinched in, looking from above, which is where the template shows it to be the widest. I imagine that is where the air is coming back to the body at an angle, and wants the body to match that angle smoothly. I think the speed matters also, higher the speed, the farther back the pinched in area should be. I realize this thread is all about the rear area, I'm thinking the air is coming back "down" from going up the windshield, and hitting the roof before the rear glass, and maybe needs the roof raised in the center in order for the spoiler to work. Just a thought!

[ChazInMT]

Originally Posted by CFECO

I'm thinking the air is coming back "down" from going up the windshield, and hitting the roof before the rear glass, and maybe needs the roof raised in the center in order for the spoiler to work. Just a thought!

Ironically, I posted this simplistic diagram the other day in another forum which illustrates your point, and shows an alternative point. It is a common misconception that the air is "Flung Out" by the windshield & front end, and to a small degree it may be. But the effect is much smaller that you imagine.

In my mind, I see the Template as being the ideal balance between having too aggressive a shape and too flat a shape. An aggressive shape creates a dynamically induced low pressure drag at best, and shreds attached flow at worst creating turbulent flow, both Cd killers. Too flat a curve which will make for a very long vehicle with no appreciable gain, or, more likely, a shortened version of a longer template which will have a larger rear area flat area leaving the air to come up with its own way of dealing with itself, which is never a good thing on the back end of a shape.

So, in effect, air in front of a vehicle is "Smart" and can overcome problems by sort of creating its own shape, going from the ideal crappy front end, to an ideal aero shape front may gain you 20-30% overall gains in Cd.

In the back of a vehicle, the air is "Stupid" (No offense to any stupid people who may be reading this post) and does not manage itself well in the absence of a shape to follow, we must, as a people, as true eco-modders, devise ways to guide the stupid air. One of the easiest most effective ways is to follow the template. It is through proper use and adherence to this template, that 70-80% of the achievable gains may be realized. As always, YMMV (which is really just another way of saying your probably doing it wrong).

Finally, let us ponder the mystery of the shape, and give it our praise.

[California98Civic]

Originally Posted by ChazInMT

Finally, let us ponder the mystery of the shape, and give it our praise.

Amen. It has humbled me by frustrating my efforts to defy its "gravitation" (or should I say "flow"?).