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A few questions about undertrays - FC

Old 08-15-09, 02:13 PM
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A few questions about undertrays - FC

I started working on my undertray/airdam template today and although it mocked up just as I thought it would, I have a few questions that I was hoping the track guys might be able to answer.

Basic plan: flat underbody back to the steering rack (probably out of sheet aluminum), with a small airdam cut out in front of the radiator and behind the oil cooler (its a V-mount). I'm planning on welding or pop riveting on 2 vertical brackets that will then bolt to where the factory tow hooks are as the main mounts. This where my questions come in.

I mocked it up out of cardboard, and I was surprised by the amount of space around the lower area of the radiator that is normally covered by the stock undertray. Would it be super ghetto to hack up the stock undertray? I would cut the center out but retain the sides, bolting them in like stock and then probably riveting them onto the new undertray to seal and provide additional support. I was feeling that I would end up with a very complicated piece of aluminum to replicate the general shape and the seal around the sides, and I am trying to keep costs down til I can find an engineering job.

Second question has to do with where I should end it. I had planned on going back to the steering rack. Should I go shorter, like end it right at the bottom of the radiator? Would the diffuser effect of the air gaining all that new space between the rad and the engine (and the resulting pressure drop) help my airflow through the radiator? Or would it be so turbulent that I'd end up with a higher pressure?

Any other thoughts or suggestions? I'll get pics once its a bit further along.
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Old 08-15-09, 11:00 PM
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Careful there, you're gonna potentially generate enough downforce that you need a rear wing to balance it out. Just a lip on my FC with no rear wing seemed to contribute to a "spins out while braking straight into turn one" problem I was having.
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Old 08-17-09, 06:14 AM
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I have seen a few fc scca road racers use a a piece of plywood instead of thin metal. They do give you front downforce at speed so it needs to be strong.
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Old 08-18-09, 09:46 AM
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Ok, so make my mounts beefy since they need to be able to withstand some downforce, and think about a rear wing. I didn't real have downforce in mind, I was thinking more along the lines of helping with my cooling, but that seems like a nice bonus. Any other thoughts? I did read the thread on the plywood and that doesn't seem like a bad idea.
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Old 08-19-09, 04:05 AM
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Firstly if there is a rule book for the series you regularly compete in then check out what you might be limited to. Running a splitter/undertray back ot the front of the subframe just under the steering rack is just fine. In fact use the 3-4 holes on the front of the subframe for the rearward/center mounting point. Marine grade ply or MDF will work fine. Think about getting rid of your factory tow hooks and having a single one out front that is strong enough to service you well. And yes balance out the added downforce with a rear wing, mounted as high as your eye, and the rules will allow.
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Old 08-19-09, 06:19 PM
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Love to see some pics of the setup when you finish.
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