Rear Spoiler Progress - Magnum

[Hemissary]

After many iterations, I'm pleased (finally) with a spoiler shape that becomes a part of the vehicle as opposed to just an add-on. Keep in mind this particular shape only adds approximately 38Lbs of downforce at 100mph. In other words it is designed more for looks than performance.

I hand-formed pieces of 020 aluminum sheet to precisely fit the contours of the lower rear edge of the OEM spoiler. This gives me a basic shape and backbone that I can then create various curves along the trailing edge (TE).

One of the (very) few things that I did not like about the OEM unit was the thick/blunt TE. One of my areas of expertise includes aerodynamics, thus the ability to figure out in advance what angles of attack (AoA) will give X-downforce at a given deflection and velocity. It is a given that blunt TE's create drag, and in this case might be there on purpose to add some energy to the stagnant low pressure area directly behind the vehicle (help with evacuation to lower cD). But given the dust patterns I have observed on the rear glass and yarn I have taped in place to observe surface flow/direction, it ain't working.

More importantly for this excersise was is to create something that is unobtrusive and melds/blends into the existing shape of the Magnum. A very difficult proposition, at least for me. The OEM unit just plain fits well, with adequate proportions.

Here are a couple of shots showing preliminary bending/forming:




This side view approximates the angle the unit would sit at on my Magnum (given the lowering and neutral/negative road-racing stance I prefer):



This pic shows how I have elected to blend the bottom TE edge into the existing spoiler:



This pic approximates the view from the rear:


This pic shows how I cut out the protrusion that houses the 3rd brake light. This created a single/simple curve for the aluminum backbone. I glued in an aluminum bar to give back rigidity while constantly handling during fabrication:



This view shows temporary attachment and a decent shot of the TE sweep:


Next I will use an adhesive-backed MYLAR I use in my other hobby to cover and add color to radio controlled aircraft. Essentially, you use an iron to pull taunt and adhere the material along the leading edge (LE) and TE. The material is pulled around to adhere to the underside of the OEM spoiler and the backside/rear of the aluminum support. Once this is done, a heatgun is used carefully to shrink the material drum-tight. The end-result is the most beautiful compound curve between the LE and TE. Now the pics of the tip-shape above should become evident, the MYLAR will begin floating immediately to create that awesome compound curve!

Here is a quick pic of one side of a V-tail showing the MYLAR (in this case translucent yellow) on an open balsa/carbon fiber wing structure.



Now I'm sure most folks are thinking what the hell is this gonna do. Well, once I am happy with the curve/shape, I wax the MYLAR/aluminum back support with a parting agent, cut fiberglass and carbon fiber cloth (E-glass for support/rigidity and low mass - a light carbon weave for looks), wet it out with epoxy resins, lay it on, and roll/tamp it out. Given the nature the material, it flows/hugs those compound curves with no effort.

Given that the work (OEM spoiler/aluminum backbone) is basically a positive mold, there will be some surface prep required to achieve a paintable finish. Some work is involved here.

But the combination of the OEM spoiler and the aluminum backbone offers some interesting possibilities. I could make a negative mold of this same structure out of structural glass and produce a final (and repeatable) product from it. I've done this with hi-performance sailplanes...however it's too much work and I don't have a lot of time anymore it seems (who knows...might make a topic for discussion).

Now I could incorporate the aluminum backbone right into a one-off design "as" the backside of the spoiler. Or I could glass that rear face at the same time as the compound curve and have a wet-joint along the entire TE (which would be desirable for added strength/endurance). This would creat an even lighter structure and git rid of the problems of proper/adequate prep of aluminum prior to paint application (aluminum begins oxidizing immediately).

Oh yes, after the epoxy has cured, I simply work up one edge with a blade and apply compressed air between the existing OEM spoiler/aluminum backbone and the new composite structure, and it pops right off.

Clean the structure up, remove the parting agent, remove the aluminum backbone, apply a urethane adhesive (PL-Premium for example - same stuff I used to adhere the shaped sheet-steel I cut to shave the rear wiper/hatch handle prior to filling), and attach it to the OEM spoiler. Some filling/sanding/prep and presto.

What I really like is the sharp/defined TE. Not only does it meet one of my end-goals, there is significant aerodynamic advantage by creating a clean (unturbulated) break between energized air flowing along the roofline and stagnant/turbulent (otherwise known as dirty) air which exists in the low-pressure area directly behind the Magnum. A very defined shear-layer is created by that sharp TE which reduces interaction with that dirty air, which in turn creates less turbulence, and therefore less drag.

If I get to installing the MYLAR this evening, maybe I can post pics before bedtime, Update 11:04PM, see a few messages down...

[blackmagnum06]

awesome spoiler! you got skillz! any pics of it next to your magnum to see how it would look?

[Charg-um@BMC Performance]

Very interesting, I like the look of the aluminum bottom, even though it is just for shaping.

Look forward to seeing the final shape.






My wing project should be back on track shortly for those that want to ask...

[Hemissary]

Hemissary is under the knife getting the rear *&^%$#! quarter repaired from the last snowstorm;

http://www.lxforums.com/board/showthread.php?t=109146

should be back in my arms by next week. Anyways, here is the results of covering the "buck" (OEM spoiler/aluminum back support) with silver Ultracote. Hard to believe eh?






Now I could mount this in it's present form and drive around with it for quite awhile, but it ain't no Inferno Red. Note the glass smooth finish, just ripe for a negative mold.

This shot shows the backside, I'm literally using an iron to adhere it to the aluminum and thermoplastic. That's Nimbus my roommate stupervising:



OK, ready for the heat gun:



Backside trimmed:


I got carried away and forgot to take some action pics of the MYLAR shrinkage, here is all that was left to tidy up:



I need to remove the MYLAR and dolly the extreme left/right rear a bit to lift the (aluminum) trailing edge (TE) a bit more. Although I shaved some of the OEM spoiler's top surface, the MYLAR is touching , allbeit barely. You can just make it out in this shot:



I will re-apply a MYLAR that is a few MIL's thicker for more rigidity, then start cutting/glassing. I think I will retain the aluminum back support for a couple of reasons. I will have a very hard TE that will be ding-resistant, and it will be easier to incorporate the 18" LED strip from Oznium using a laser to cut the 50(!) LED's. I just had an idea, I could laser the 5.5mm holes in a wavey sorta pattern mid-span/mid-height on the aluminum back support!

Now a question for you all; Basecoat/clearcoat Inferno Red to match, or semigloss black? Or Inferno on the top/front side and semigloss black on the backside? Or I could use carbon fiber cloth and clearcoat. Or?

A final shot:

[Magnum375 Jr]

Damn...looks really nice...Good work my friend, can't wait to see it on the car.

[Charg-um@BMC Performance]

That will look sharp on the car !! Pun intended !

[MAGNUM8R]

Built a ton of model airplanes myself.
Your wife lets you do that in the house???

Hope the covering does not deflect or sag when you lay up the glass!!!

Keep us posted!!!

[MAGFX]

Nice work there, Simon. I love it and can't wait to see it finished and flying through the air.

[pigpen]

Woow, nice,

[Hemissary]

That's your donor spoiler Pigpen, thanks again!

[B.high]

looks good

[lowriderman3]

Very nice!

[hemicanucksfan]

looks great. can't wait to see it installed.

[AlbertaAMX]

I saw something in there about negative molds. Going to be going into production?

[Hemissary]

Let's cross that bridge when it has been test-mounted and it's appearance is actually proven to be worthy.

Then there is the manner in which to would be mounted; As in whether or not the resulting composite structure should be sold as-is, and you folks have the ability to mount it and then blend it in.
The flip-side is actually (me?) mounting the structure to existing OEM spoilers and marketing that.
To be truthfull, time is at a premium for me as is most of you. I love the idea of offering something folks would enjoy, but the execution of such can be difficult to balance with the rest of my activities in life...

The thing to do might be to gauge interest after pics have been posted, and a consensus is drawn on what something like this would actually be worth to those who see value...