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Old 11-24-2009, 05:11 AM   #21
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Quote:
Originally Posted by Sam Amporful View Post
It would be soo ironic if APR was using wood too
Its not ironic, its coincidental.
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Old 11-24-2009, 05:17 AM   #22
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Originally Posted by NA6C-Guy View Post
True, but that wasn't exactly done with weight as a priority as much as strength. I was just assuming ABS would be lighter than plywood and fiberglass. Then again my mind is so stuck on plywood being 3/8'' and 1/2'' building material that breaks your back after you have to carry 20 sheets of 4'x8' up 3 flights of stairs... I guess something like thin birch isn't so bad, especially in splitter size. You know what they say about assuming though...
According to my Machineryís Handbook

Desity

ABS plastic 1.04g/cc
Birch wood air dried 0.70g/cc

Im trying to find some elastic modulus comparison and havent found yet but I also think Birch is not only lighter it is stiffer as well.

Bob
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Old 11-24-2009, 05:26 AM   #23
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I'm sure it is, but I figured you would want some flex to avoid splitting or cracking them. Though I guess at the same thickness, ABS is probably too flexible like you said and at 150mph would be pretty crappy.

You learn something new every day on here. Plywood>ABS, who would have thunk it...
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Old 11-24-2009, 05:37 AM   #24
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Originally Posted by Full_Tilt_Boogie View Post
Its not ironic, its coincidental.
Actually Balsa wood makes an awesome core material for fiber reinforced plastic similar to honeycomb. Corvettes even used balsa in there tub structure at one point.

The floor of some trucks I’ve worked on use a massive amount of Balsa sandwiched between fiberglass panels for a floor structure, The Kenworth T2000 has been in production with a Balsa core floor for more than 10 years now. It is stiff as hell.

Bob
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Old 11-24-2009, 05:50 AM   #25
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And if you have any left over you can whittle an airplane and have a grand ole time. I used to love those little balsa wood flyers.
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Old 11-24-2009, 06:28 AM   #26
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Its not really necessary but are you gonna shield your exposed tire from onward approaching air?
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Old 11-24-2009, 06:31 AM   #27
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Originally Posted by Savington View Post
I use 12mm Birchwood with a 1" box aluminum frame. Lighter than an APR splitter of the same dimensions - I didn't even believe that one for myself until I met Manly Kao at SLB and he showed me his APR carbon splitter vs. the 12mm Birch splitter he had made. Same dimensions (the birch splitter actually mushroomed a little more) and the birch was quite a bit lighter.

ABS is not cheap, folks. I don't know what kind of material TAP recommended, but a 4x8 sheet of ABS was $130 or so for .250" when I got my quote from them. I think the cheapest I found it was $100 online, and the shipping was astronomical. I originally was going to use that, but the birch is 30% of the cost. For something that WILL get destroyed, you want it cheap and disposable, and stiff enough to do the job - weight is a nice afterthought, but not at 3x the cost.

Bob, I wouldn't even bother with the fiberglass unless you want the aesthetic qualities. I can pretty much stand on my 12mm birch splitter, and I don't have any forward supports on it either.

cjernigan crewed for APR's Rolex team this year at a couple of races, and IIRC he told me that 75% of the cars in the paddock at that event had wood splitters.
I may have to just go get a 12mm ply my local stores seem to sell just 1/2" not the 15/32" or 12mm though. I've got my pattern now so making it out of different material will be easy.

Bob
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Old 11-24-2009, 06:34 AM   #28
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Quote:
Originally Posted by Sam Amporful View Post
Its not really necessary but are you gonna shield your exposed tires from onward approaching air?
Yes I am planning on doing that too. The 275's with 15mm spacers expose a lot of tire in the front view.

Bob
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Old 11-24-2009, 09:06 AM   #29
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Quote:
Originally Posted by bbundy View Post
According to my Machinery’s Handbook

Desity

ABS plastic 1.04g/cc
Birch wood air dried 0.70g/cc

Im trying to find some elastic modulus comparison and havent found yet but I also think Birch is not only lighter it is stiffer as well.

Bob
Good post I wish all newbs did this,I wish IAlways did this
-G-
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Old 11-24-2009, 09:28 AM   #30
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Don't stop at the splitter. Go all out.

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Old 11-24-2009, 09:34 AM   #31
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FWIW I picked up a 4x8 sheet of .25" ABS locally for $75. Haven't made it into a splittr but I don't think it's stiff enough. It might work for a 1-2" but much more than that you'd have to reinforce it. I was planning on riviting a sheet or aluminum to the bottom, but I'm not sure if that'll be enough.

I'm looking forward to seeing how yours turns out.
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Old 11-24-2009, 11:14 AM   #32
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Post up some lap times from before and then after to shut all the haters up!
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Old 11-24-2009, 11:42 AM   #33
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Quote:
Originally Posted by Reverend Greg View Post
Good post I wish all newbs did this,I wish IAlways did this
-G-


Savington: you didn't mention 'glassing your birch. How does it hold up in wet weather if it's not glassed? Also, can you point us to some pics of the alu frame you made up? Welded together or bolted?

Thanks for the good info, all.
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Old 11-24-2009, 11:58 AM   #34
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Quote:
Originally Posted by tann3r View Post
FWIW I picked up a 4x8 sheet of .25" ABS locally for $75. Haven't made it into a splittr but I don't think it's stiff enough. It might work for a 1-2" but much more than that you'd have to reinforce it. I was planning on riviting a sheet or aluminum to the bottom, but I'm not sure if that'll be enough.

I'm looking forward to seeing how yours turns out.
That is what I thought. ABS might work for the little short cosmetic splitters like Track Dog makes for instance but for a real splitter that will create down force at high speed it needs to be much more substantial. You arenít going to be able to bolt a hunk of flexible plastic to the bottom edge of the bumper and have it support a measurable amount of down force.

Slick auto APR splitter.
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Old 11-24-2009, 12:22 PM   #35
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Quote:
Originally Posted by tann3r View Post
FWIW I picked up a 4x8 sheet of .25" ABS locally for $75. Haven't made it into a splittr but I don't think it's stiff enough. It might work for a 1-2" but much more than that you'd have to reinforce it. I was planning on riviting a sheet or aluminum to the bottom, but I'm not sure if that'll be enough.

I'm looking forward to seeing how yours turns out.
it may seem flimsy when in a 4x8 sheet, but might be a different story once you cut it down to size. it was like that when i bought my aluminum. i have a thin sheet but it's very strong and doesn't weigh a ton. you guys are way overthinking this. also thin wood has been used for years. the only time i bent my aluminum splitter was an off at VIR where i went over the rumble strip. i pulled into the hot pit lane expecting to see splitter hanging loose. (especially since i only have 4 points holding it on. to my surprise, it was still on tight. it was just bent down. i tried to bend it up but it was too stiff. then i tried to yank it off, kick it down to rip it off the attachment points, nothing, it wouldn't budge. i had to pull in and unbolt it. so it was way stronger than i expected.
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Old 11-24-2009, 12:30 PM   #36
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Originally Posted by Gotpsi? View Post
Post up some lap times from before and then after to shut all the haters up!
i don't think anyone is disputing the fact that splitters work.
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Old 11-24-2009, 12:38 PM   #37
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Quote:
Originally Posted by bbundy View Post
Slick auto APR splitter.

lets see that guy stand and hang somewhere other than RIGHT at the supports...
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Old 11-24-2009, 12:47 PM   #38
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Originally Posted by y8s View Post
lets see that guy stand and hang somewhere other than RIGHT at the supports...
Agreed (and he looks smallish)- check out this pic at speed. Looks like it has a fairly mean droop between the two supports.
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Old 11-24-2009, 01:17 PM   #39
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Agreed (and he looks smallish)- check out this pic at speed. Looks like it has a fairly mean droop between the two supports.
He is 145lbs.

Looks like they had to redo the place where the rods mounted to the body.

Before



After



Another reason that allot of people use wood especialy on the track is that if you have an off or damage the front splitter Alum will bend and f up your air-dynamics in the front. Wood will just break off.
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Old 11-24-2009, 02:44 PM   #40
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also don't forget that plastic is much less likely to go through heat exchangers than metal.
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