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DIY Front Bumper/Air Dam (Yes, really)

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  • DIY Front Bumper/Air Dam (Yes, really)

    Forenote: This ISN'T really a how-to, but mods feel free to put it there for informations sake as it may have some helpful hints...

    So any true car DIYer out has had an idle moment where they went "Gee, I wonder if it's possible to make my own bodykit" and then sent their fingers typing their way to Google. But, as I'm sure even a quick search can tell you now, the majority of Google hits for such a query are people posing that question on various forums and being met with responses that range from "Don't bother" to "Seriously, don't bother".

    Well, my mate Steven (who is a member here, but hasn't posted since his before his 300ZX went to car heaven) got it in his head that he really didn't like the look of the front of his 1979 Nissan 280ZX and wanted to build a custom bumper to go there as the existing kits are either not what he wanted or not economical to get here. This is where I come in, because he has enlisted my help (I have the tools and space and between us the know-how should be there somewhere) and the naive fool I can be went "F*CK YEAH LET'S DO IT!"

    This is something like the basic idea of what we're aiming at:

    (only a bit more writing I swear)

    So originally the plan was to make a frame of cardboard, fill in the gaps with expanding foam then take it back to the desired shape before taking a fiberglass mould from that. Well I had a brilliant brainwave that involved the long-forgotten material 'extruded polystyrene'. That would have been perfect, if it weren't $100+ per sheet (needing 3 sheets), so we went back to the inferior plan A and made a second trip to bunnings for a few things. Then back to mine to begin:

    3 cans of expanding foam
    1 50m roll of tape
    30m roll of alfoil to cover parts that we didn't want destroyed by expanding foam (expanding foam DOES NOT COME OFF [okay, that's not entirely true but it's a ***** to get off anything at all])
    Also some lunch in the plastic bag...
    Some of Steven's tools (actually, most of them; that's why were at my house)
    Mountain Dew
    and cardboard, lots of cardboard

    For the interested, this is the foam we used (despite initial concerns I will vouch for it's usefulness). It was $16 for a 750ml can at bunnings and fills about 3x the amount expanded fully according to the can.

    We disassembled the front entirely so that we're left with just the gaping hole that will be filled with the front kit:

    (all the bits that came off the front)

    So anyway, we decided that to begin we needed to get a template of the basic shape of how the side sections would look, so we covered the headlight buckets in alfoil and gave them a cardboard base. This leaves us with a fillet/section/piece/slice on each side and they are the beginnings of the mould making. So maybe I (yeah, I'll take responsibility for these) got carried away with the foam, but it's hard to make it fill gaps when you don't have the patience to find out if it will expand to fill them or if you need to put more in, so I went the the ol' more-is-better approach and got this:

    Okay, cool. Those are massively oversized.

    It's also at this point that I begin getting pissy because I overlooked finding out how much the foam would harden as even after 30 minutes it is still far too flexible to be of any use to us (think: packing peanuts). Steven tells me to harden up, build a bridge and get over it and wait the full cure time before we panic. (not a fan of failing at anything, especially so soon into the project). Anyway since we spent the first half of the day going on a wild goose chase after way-too-expensive polystyrene this is where we lost the light and called it a day.

    But when you're excited about a project, a lack of daylight won't stop no one. As it turns out the foam cures hard to enough to be more than useful (perfect it maybe too strong a word, but it's not bad at all). So after the full 4 hour curing time Steven came back and we spent some time carving the excess foam off to get a closer shape. We were impeded by the fact that in some of the deepers spots there were pockets of still un-cured foam meaning that we couldn't get the shapes perfect today, but they are reasonably close.

    (half a bin full of the stuff we carved off both)

    (beer is definitely a requirement for this project)

    After some carving we had a quick and exciting test fit

    Carved out the stuff that was in the way, and managed to get both headlight buckets to hang in place. I tried to explain to Steven that unless you're doing the project you wouldn't understand WHY this next picture is exciting since it now looks like it's got droopy eyes, but take my word for it when I say it is definitely exciting:

    It's just so cool to see that it's all working so far and that a project like this is not impossible like most forum goers found via google would have you believe.
    Last edited by popsprocket; 10-02-2011, 04:38 AM.

  • #2
    im actually doing this right now for my micra..... fiberglass is a pain in the ass to work with.....
    looks good so far (better than mine :P)... honestly, its definitely worth it making your own kit.... this car is gona b one of a kind when this is finished with the kit

    good luck and keep us updated. i definitely want to see how u get this done so i can compare your method with mine (if theres any difference in the end).
    i asked god for a bike and soon realized god doesnt work that way. so i stole a bike and asked for forgivness,
    the early bird might get the worm, but the second mouse gets the cheese.
    sex is not the answer, sex is the question, yes is the answer.


    • #3
      Awesome work till now man, can't wait to see when its all done.

      Ps. I've seen a guy with a beemer somewhere in the US try out something very similar to this. He gave up eventually :/


      • #4
        i tryed this once before, i got half way threw and then decided to sell the car. but heres how it looked.

        i used a stock lip off a commodore, then screwed it onto my bar and filled in the gaps with sticky tape and chicken mesh then fiber glassed over the top and then bogged it up.
        Attached Files
        Qualified to do stuff!


        • #5
          Originally posted by Faceplant View Post
          i tryed this once before, i got half way threw and then decided to sell the car. but heres how it looked.

          i used a stock lip off a commodore, then screwed it onto my bar and filled in the gaps with sticky tape and chicken mesh then fiber glassed over the top and then bogged it up.
          Did you sell the car with the bog?


          • #6
            Originally posted by upamanyu View Post
            Did you sell the car with the bog?
            it was removed for the sale, i didnt get to the point of molding it to the bumper.
            Qualified to do stuff!


            • #7
              Okay, so we put another whole day into this project got more done since we didn't spend the first 6 hours of the day creating more problems than we were solving. We had a quick discussion when Steven got here on which part of we should do next and decided that having the bottom piece of the mould meant that we could add in a middle section without the pressure of anything having to match up perfectly to existing shape work.

              When I tell you that this next part took us 5 hours, it included cutting cardboard, taping cardboard together and getting up to get a drink once. Not even kidding. Making this cardboard frame was damn well time consuming. It is made to the way Steven has settled on, which is slightly different to the one on the photoshop in the original post. Made it in two layers, the bottom layer cuts backwards to form a bottom lip, and the top layer tapers forward slightly where it will eventually be continued until the taper meets the underside of the headlight buckets. The very front edge of the bottom piece SHOULD be vertically in line with the front of his car (if we get it right).

              Making a mess.

              Bottom layer

              Both layers ready (5 hours after starting) to have foam added.

              These pictures are a fairly accurate representation of where the bottom edge will sit as well since two bricks stacked up happens to be about the same height as Steven wants it to sit (150mm off the ground - not too low, not too high).

              We decided to follow the instructions on the can and do the foam in multiple layers since we'd had trouble with un-cured pockets of foam near the centre the night before while carving up the first pieces we made.

              The first layer:

              The second layer did go in today, but it's currently not pretty (and I didn't get pictures as we were rushing out the door to go see people). The cardboard deformed slightly, especially in the places we really needed it to stay flat for the sake of our sanity not having to make a smooth perfectly level surface. It will be a pain in the ass to get it back to the desired shape now, but since it took three whole cans of foam to do the two layers we weren't willing to write it off just yet.

              But, for future reference you should use wood (even though we won't even now). I personally don't like working with wood as it's messy, and mistakes aren't as cheap or as easy to fix as when you use cardboard. But it's something to consider.

              Stay tuned, due to a mix up in work shifts this project will get ANOTHER whole day tomorrow (Y) There's still four more sections to make and fill with foam before we can assemble it and start properly shaping it.
              Last edited by popsprocket; 11-02-2011, 04:03 AM.


              • #8
                Alright so while I didn't remember to take a picture, I can assure you that today started on a low with the prospect of having to carve up the monstrosity of a front lip that the foam had created. It was uneven on every surface intended to be flat and the amount of foam spilling out the front was daunting. It seems the amount the foam expands varies between cans, as a result one or two of the cans had foam that expanded way too much, while the others were more reasonable. After about 30 minutes of making a mess using a cheap bread knife and small toothed saw (a bread knife is easily the most effective tool to use aside from an angle grinder) to try and make the top and bottom level I decided it was time to break out the power tools.

                The sander didn't work, which is a shame because it has a large flat surface which would have been perfect for making a large flat face on the foam, but alas it did nothing but warm the foam and make a small amount of dust. So once again my old nemesis the angle grinder is the winner of the useful competition. We broke out the flap disc (a disc made of flaps of hard sand paper style stuff) which tore through the excess foam without blinking.

                Unfortunately to get at the top and bottom surfaces which were way too far off their original line, we had to cut off the old cardboard top and bottom, which presented the problem of not knowing where the edge should be exactly. But that's a story for a few seconds time, because we had a bumper to test fit after it's first go over with a grinder, and voila

                Definitely getting there. At the sight of this we were in a pretty good mood and didn't waste any time deciding that we needed a cardboard template for the top and bottom sizes before we could clean it up anymore.

                That presented problems, but after 3 hours of "But it's right when you measure it, just not when it's on there!" we got them on, shiny new templates to be our guides.

                With that, we cleaned it up even further and then went and stuck it under the car again just to get our spirits up, and boy did it work at that:

                At the end of the night we spent about an hour talking about what to do next because we were starting to confuse our selves, and ran across something that we hadn't caught yet in the form of the top template being the wrong size since it's first incarnation, luckily for us we caught it before cutting into the foam so we're still all good (Y)

                Last edited by popsprocket; 12-02-2011, 12:52 AM.


                • #9
                  slowly getting there, keep up the good work.
                  Qualified to do stuff!


                  • #10
                    Well this is about 60% of the foam bases we have to make there's probably 2 more days in making the rest and getting them roughly right, then there's probably 3 days work in getting them smoothed down with plaster filler (more flexible than bog) and then after that we can look at buying fiberglass.

                    First we'll take a (male) complete bumper off our foam mould, test fit it and generally figure out what needs to be improved and see if we have the mounting points right, and then use that to make a female mould that we will cast the final product out of. Then after that we'll see if there is any interest in the Z car community and might sell a few if it tickles anyones fancy.

                    Thanks for the comments guys, if you have questions just ask I'm more than happy to help (especially since you won't find much anywhere else on the internet).


                    • #11
                      make sure you leave good flow for the radiator in the design and perhaps angle the edges to help direct more air into it. and then add a big front splitter to help put some down pressure on the front wheels to help high speed turn in.
                      Qualified to do stuff!


                      • #12
                        We got some wind tunnel results from the Z community that say the hole at the front needs to be 30% the size of the radiator for optimal performance. I won't really pretend to understand it fully but I'll trust them on what they say about the ram air effect not working if the hole is too big. Steven will have a grill made for it and behind that we'll put a bit of black alloy to block off all but that 30%.


                        • #13
                          So we didn't get started until late today and I largely did my own thing on my car which left Steven to make the next section himself. It took him about 3 hours to work through the problems with lining the whole thing up and getting the foam under the headlight buckets cut so that they would meet up with the middle section. I took a few pictures of the test fit since we really ran out of sunlight before we got to filling them with foam.

                          There is mounting points for the front tow hooks that prevent our foam monstrosity from going as far back as it will be in the end, but it's getting reasonably close. The very bottom edge of the kit will line up vertically with the outside edge of the body work in the bonnet and headlight buckets.

                          It's worth noting that the bottom lip won't be that shape and will actually cut inwards until the middle line, and then taper outwards to form a bottom lip, a bit like this:


                          Only the bottom half will have a much more drastic kick out than the top.


                          • #14
                            looks like it could eat a neighbors dog... is that your plan?

                            " there ya are you little mutt ... wake me up at 2 in the morning!" * puts the pedal to the metal*

                            if thats the case please change the bonnet badge into a crosshair this will help you line them up.
                            Qualified to do stuff!


                            • #15
                              Thats looking sweet as.. Can't wait to see you finish it.

                              2008 Honda Civic Type R, Honda Accord Euro CL9
                              1991 Honda Civic Gli, 1977 Honda Civic 2 Speed Hondamatic Auto, Mini-Me Ed Civic