Getting started fabricating (seeking advice for producing good-looking aeromods)

[christofoo]

I'm new to bodywork, and I'm having a hard time getting started on my "big" aero mods (front bumper and tail). I'm a physicist, and I am pretty handy with a range of different DIY tools (esp. woodworking, home improvement, and electronics). I feel like some of you with more aero bodywork experience could help steer me. I've read a ton, but without the experience I just don't feel it coming together, and I've already had a couple false starts.

My goals:

• I want it to look good. My 6th gen Civic sedan is the one that really needs mods. It's actually my wife's car, and she demands that the mods be svelte. In particular I think the corrugated look is not okay where it gets noticed.
• I want my mods to be cost-effective and time-effective, but:
• If I end up with some low-tech molds that I can re-use, I think it would be cool to do some short-run "production" and sell my mods. But I don't have to. To understand me better, if a good-looking fuel-efficiency body-kit were available for the Civic for much less than $1k, I would buy it and be done (my time is precious to me). On the other hand if I could spend 200 hours becoming a FE bodywork master and be the one to produce that product and make a little money doing it on the side, that would also be worth it to me. Is it worthwhile?

Here are my thoughts on non-molded approaches:

1. Minimalist: Grill blocks and air dam below the bumper in coroplast (or lawn edging for the air dam). I think this is not the ideal nose configuration for efficiency, it won't lower the point of stagnation as much as it should due to the curvature of the bumper, and I will still need better tricks for the wheel skirts and tail.
2. "Sports" body kit (front bumper and skirt): should result in some fuel-efficiency gains, but requires grill modification, and in the end would not be optimal. Also I think the fact that the front is lower than it ought to be will mean that scraping will be more severe than it ought (correct me if I'm wrong, I think the "sports" bumpers are lower than optimal). Overall I think this doesn't rank highly for cost-effectiveness, although it ranks well for time-effectiveness, but not really because I still have to learn some bodywork tricks for the rear wheel skirts and tail. I'm also hung up on the look. Obviously some folks love it, but I'm not one of them and I'm not enthused about meeting ricer chums.
3. Reinforced coroplast methods with added "finishing". By finishing I'm thinking a layer of hollow-bead-filled epoxy, sanded and painted, to eliminate the corrugated look. For reinforcing I could use metal or corrugated strips underneath, and/or fiberglass before finishing. Not sure though, maybe the fiberglass is necessary to make the system hard enough so the finishing layer doesn't crack. Possibly I could search for a finishing layer a little more flexible than epoxy, and yet it needs to be hard enough to sand. Bead-filled Liquid Nails?

My thoughts on molded methods (as I currently understand them):

1. Molds: I like foam for ease of creation. (Easiest for male molds, just use a straight hot wire.) But if I want the mold at higher temperatures (thermoplastics) I should maybe switch to woodworking. I've also thought about coating a foam mold, i.e. brush on plaster, sand it smooth. Plaster over foam might crack though, maybe silicone would make a better high-temperature top-coat, but I don't think silicone is sandable. Mix silicone with a filler? Filled liquid-nails?
2. Fiberglass: to me the primary drawback of fiberglass is the number of chemicals I have to safely master. Just feeling a little chicken here. Also if I want to reuse my molds and do some short-run production, fiberglass layup will take a lot more time per unit than thermoplastic. Check me; does fiberglass tend to be around $3-5/sq-ft including resin after you apply the required 3-4 layers?
3. Simple-curve thermoplastic: if I can avoid compound curves, then I can form the thermoplastic without a vacuum fixture. Mcmaster has a temperature-controlled heat gun which I think would be good for this purpose. Not sure about a hair dryer. As long as it's a simple-curve, I could use a foam mold and use a sheet of something to protect the mold from the heat. A sheet of silicone would be re-useable. A sheet of corrugated plastic could probably be formed together with a solid thermoplastic exterior and the two could be glued together to form a stronger double-layer.
4. "Frame molded" simple-curve thermoplastic: use "frames" instead of molds. I.e. construct a re-usable frame where the curves are created by metal conduit of the desired diameter. Use the heat gun to apply heat from the inside of the conduit. I just had this idea. I think it would be perfect for tail-end stuff. Not so much on the front bumper where I need to match the curves on the car. Hmm. The curves could be multi-layer for strength, and the straight panels could have bar reinforcement.
5. Vacuum forming: Probably my favorite idea for compound curves and short-run production, but I imagine making a vacuum fixture for myself would be a bit of a pain. Anyways I'm questioning whether compound curves are needed.
6. Is thermoplastic ever much less than $2.5/sq-ft? I'm looking at 4x8' 1/8" sheets of PETG on McMaster. Any pointers on the best thermoplastic choice would also be welcome. I think ABS might have better qualities, at least for simple-curves, although it costs more that PETG. (Admittedly, I have a local plastics supplier I haven't quoted either material yet.)

Sorry, I know this type of post has been repeated, but not everyone's goals are the same. I'm at that point where I've tried to help myself but I think an expert leaning over my shoulder would help.

Thanks in advance,
Chris

[freebeard]

so what have you tried that didn't work?

[christofoo]

Primarily my coroplast bullnose piece. It didn't look as good as I hoped (definitely didn't pass the wife test), also the aero design was flawed. http://ecomodder.com/forum/showthrea...ast-23162.html I also have a roll of lawn edging and a bunch of fasteners I bought for one idea or another and then thought better of it before I started fabricating. For instance at one point I thought I would do an air dam located behind the bumper, but before starting got to thinking about where the deflected air would tend to flow and decided a lot of it would end up going under the car, and so it might even result in a drag increase.

So generally my false starts have seemed to be more about bad aero design than construction method. But my motive for changing the tried-and-true ecomodder designs was for simplification of the construction or some other factor. I see why that was a mistake, now I want to do it right.

[MetroMPG]

This is a tough one.

Have you browsed the aero sub-forum enough to find examples of mods that pass your "good-looking" test? There are a few out there that look professional-esque to me. 3-wheeler's Insight tail comes to mind, obviously. As does CigaR007's grille blocks. I think a8ksh4's pickup aero shell is headed in the right direction too.

Another potential option for reshaping the front of the car, by the way, is to make a simple, "ugly" mod, then hide the construction material with a custom or modified vinyl "bra". Sewing vinyl is easier / faster than doing bodywork!

I'm in the same boat - I've been procrastinating about doing a permanent grille block for my Insight. I want it to look "pro". But rather than deciding on a fabrication approach and diving in, I've just been repeatedly re-taping the plastic sheeting that's been threatening to fall off the car for over a year now.

[christofoo]

Originally Posted by MetroMPG

This is a tough one.

Have you browsed the aero sub-forum enough to find examples of mods that pass your "good-looking" test? There are a few out there that look professional-esque to me. 3-wheeler's Insight tail comes to mind, obviously. As does CigaR007's grille blocks. I think a8ksh4's pickup aero shell is headed in the right direction too.

Another potential option for reshaping the front of the car, by the way, is to make a simple, "ugly" mod, then hide the construction material with a custom or modified vinyl "bra". Sewing vinyl is easier / faster than doing bodywork!

I'm in the same boat - I've been procrastinating about doing a permanent grille block for my Insight. I want it to look "pro". But rather than deciding on a fabrication approach and diving in, I've just been repeatedly re-taping the plastic sheeting that's been threatening to fall off the car for over a year now.

I'm not sure if we're in exactly the same boat, since my wife doesn't want temporary ugly stuff hanging off her car, so right now the FE effectiveness of my unfinished mods is 0.

I'd never heard the vinyl fabric idea. Do you have any examples you can direct me to?

AndrewJ is probably is the closest to my way of thinking. http://ecomodder.com/forum/showthrea...amics-312.html IIRC he free-formed ABS (thermoplastic). Most similar to my options #3 or #4, although he free-formed instead of making a mold, which is another option I didn't list. (Not sure if I feel comfortable with free-form though, maybe I should try it.)

I've actually got some pipe insulation on the lower grille currently, maybe inspired by CigaR007 (don't remember), but I'm suspicious it doesn't work as well as you might think. Maybe it doesn't work at all. Really I don't think we've tested the (grill-block + airdam) camp vs (bumper overhaul), but my gut feeling, just imagining the airflow, is that the bumper overhaul is significantly more effective. I.e. if I do not fundamentally change the side-profile of the nose, then the point-of-stagnation will remain close to the middle of the bumper (even if the existing transition radii are tolerable). Probably if I scoop the air dam it will help. But even then, overhauling the bumper profile also enables a radiator inlet duct. Not sure if I understand the principle perfectly, but I believe a duct with gradually sloping top and bottom will slow the ducted air flow so it creates less drag passing through the engine bay, with a net result in less drag for a given cooling requirement. Perhaps I'm obsessing? Tough to know without an A-B-C-A test.

BTW, for the tail, I'm planning a hitch-mounted cargo rack tail, functionally similar to the "CargAero trailer" http://ecomodder.com/forum/showthrea...ibe-22780.html. That means I don't need an exact match to the car's end profile, it won't be formed onto the car, and I think I can probably get away with simple-curvature rather than compound.

All of the fiberglass-on-foam methods I saw in the forum pass the good-looks test. If thermoplastic doesn't work for me for whatever reason then fiberglass is definitely the best remaining. Bonus points for foam-molds that are reusable. Docked points for nasty chemicals.

Thanks!

[christofoo]

I almost forgot, another method may be aluminum panels - simple curves only (not going to hydroform here). Not sure what thickness I would need, but it runs $1.7/sq-ft and up. I hesitate to go this route since the Aerocivic is built that way and didn't pass the wife-test (sorry Basjoos, it's beautiful to me). Still, I wonder if I could make it look good if I could stick to a radius bending frame (similar to the thermoplastic option #4). It seems like thermoplastic would be easier though. I'm imagining forming a large sheet over a conduit frame, then using a hot wire cutter to trim. Hot wire > jigsaw > tin snips. Even if I used a jigsaw on the thermoplastic it wouldn't deform and take on weird imperfections the way aluminum might.

I don't believe I've seen any forum members use aluminum "successfully" though.

[christofoo]

One other thing, I've been thinking seriously about:

a) Building the molds I want,
b) Doing 1-offs in fiberglass (or maybe heat-gun formed thermoplastic if the curves are all simple)
c) If there were enough interest, doing short-runs vacuum formed in thermoplastic.

(Assuming I make high-temp molds, see above.)

Does anyone agree that yields the "best-looks, best practice" of bodywork? [Edit: I mean short of $100k-$1M capital for production hydroforming molds.]

I'm also thinking seriously about doing the "minimalist" front-end (grill-blocks+scooped-air-dam) in the meantime - my wife needs to take the kids cross-country next week, and I think "minimalist" is something I might get done before then and she might be okay with it. Who knows, after I do a bumper overhaul I might even do an A-B-C-A test.

(Sorry if it sounds like I'm thinking out loud sometimes.)

[some_other_dave]

Have you ever thought of getting a shot bag, some dollies and hammers, and a bunch of sheet metal? I know several people who do metal shaping (some hang out on Metalshaping Tools, Supplies and Equipment) and some of them can produce astonishingly nice looking results.

It is a whole lot of physical work, though!

-soD

[MetroMPG]

Originally Posted by christofoo

I'd never heard the vinyl fabric idea. Do you have any examples you can direct me to?

Lots of fabrication-hiding potential with something like this. (Though it would have to be modified if you significantly change the underlying shape.)

[christofoo]

Originally Posted by some_other_dave

Have you ever thought of getting a shot bag, some dollies and hammers, and a bunch of sheet metal? I know several people who do metal shaping (some hang out on Metalshaping Tools, Supplies and Equipment) and some of them can produce astonishingly nice looking results.

It is a whole lot of physical work, though!

-soD

That's a new method for me. It does look like an awful lot of work. I suspect a newb could easily expend a lot of effort and still end up with choppy results. I wouldn't rule it out though, if I thought improved collision deflection were worth having on the front bumper, it needs to be either metal or heavy fiberglass. Plus it looks fun.

(It's funny, when I did my pizza-pan wheel covers I was trying to imagine a method like that; I invented a rounded hammer and sand-box in my head, but didn't know what it was called, and didn't know if it would work.)

Metro, I guess I was just too scared to google 'car bra'.