metromizer replied while I was typing this - totally on point. I was surprised that you say that these materials will not work for large scale items. I believe AndrewJ used 1/8" ABS for his bumper / air dam, although I realize ABS is not the best for vacuum forming compound curves, in this case he formed a simple curve. I would think that a mold could be made for 1/8" PETG with ribs to strengthen the flat sections, or something else could be used to provide some framing. I could even imagine vacuum forming a second piece with crossed ribs as a framing component. Vacuum equipment had indeed scared me away from considering vacuum forming for a first attempt, but I think if it were a viable approach for short-runs I could make my own 3'x6' vacuum table and overhead oven. It doesn't seem like it would be all that expensive or difficult (40 hours maybe?), and I thought it would be feasible, but you could easily convince me otherwise. Certainly I know it isn't a tried-and-true approach for bodywork or aircraft, so I can imagine being wrong.
ref:
http://ecomodder.com/forum/showthrea...amics-312.html
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euromodder, I do agree that the "before" is better looking but I seriously doubt the aero is as good. My hypermiling was on local TV earlier this summer, it included a frontal shot of the car and no one even noticed the mod. But all front-end work should be aimed at moving air over or around rather than through the cooling
and under the car (as well as smoothing sharp transitions if needed), so the upper grill block should be first priority, since the drag difference in the two paths available here is largest (straight over the car vs through the cooling and then under the car). In addition, you can't tell from the picture, but the pipe insulation didn't fully close the gap and there were several messy openings. I was hoping for a few % improvement with the pipe insulation, but the change never blipped my mileage logs (not proof admittedly). The "after" looks significantly more aerodynamically sound to me, although aesthetically messy on the lower grill in this incarnation (and I still see an aero mess for the airflow toward the radiator that could be improved).
Freebeard, your comments echo my own thoughts. Wait till you see v2 (although this car is out of town with my wife and kids, so you will indeed have to wait).
bestclimb, I saw that foam method, it's good, but I've got some other things I want to try first. Er... maybe...
I'm going to be doing the Corolla v2 front-end next. The Corolla issues are not the same, specific enough I'm going to start a build thread for it and show designs before I start, assuming I decide it's actually going to move forward this week.
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Back on the primary topic (although these are all related issues): metromizer mostly had the type of reply I was looking for weighing practicality of various methods. Don't get me wrong, all the other comments have been helpful and have improved my own ability to judge, but anyone who can offer experienced judgement, i.e. fiberglass vs aluminum sheet forming or vs thermoplastic methods, is golden.
Certainly context matters; individual mods favor specific methods. I.e. I'm (tempted) to conclude that:
Vacuum forming on short-run production is the highest "total value" method for wheel skirts. (I'm also imagining more crude thermoforming might be possible for proof-of-concept.) But that doesn't apply to tail, bumper or louvered Kamm fabrication. I should end up with a matrix of optimal methods for each mod.
It's about time for me to just jump in and try stuff. At some point that has to be done. I'm not afraid to make my own missteps, and report back when I have results.
