Rear Diffuser
Race Director
Joined: Jun 2004
Posts: 13,966
Likes: 710
From: WI
Really coo stuff here fellas, a lot of talent too.
I got one stupid question, unless you guys are going to spend time north of about 125MPH for extended periods of time, why do you NEED a diffuser?
The fastest I go is about 109 at the end of the 1/4 mile. Unless higher speeds are in the game, why the diffuser? I doubt co-efficient of drag will be reduced to any measurable margin. So for gas mileage cannot be the reason.
If your doing just because it is cool, that is fine, just thought I'd ask.
FYI, I like the pic of the Integra with one....wow like your going to go 150+ with an Integra, granted with mods is possible, but why?
I got one stupid question, unless you guys are going to spend time north of about 125MPH for extended periods of time, why do you NEED a diffuser?
The fastest I go is about 109 at the end of the 1/4 mile. Unless higher speeds are in the game, why the diffuser? I doubt co-efficient of drag will be reduced to any measurable margin. So for gas mileage cannot be the reason.
If your doing just because it is cool, that is fine, just thought I'd ask.
FYI, I like the pic of the Integra with one....wow like your going to go 150+ with an Integra, granted with mods is possible, but why?
Burning Brakes
Joined: Apr 2006
Posts: 1,218
Likes: 7
From: Burleson Texas
I should have clarified. I'm planning on making this a 'plug' and then use it to make the real mold. just in case I want to make more or better if for some reason i screw something up. That way I won't have to do everything over.
If I did do this, where can I find mold release? How expensive is it?
thanks guys.
If I did do this, where can I find mold release? How expensive is it?
thanks guys.
Carnuba Wax is a great release agent, same thing you use on a car, doesnt have to be a special brand, the cheap turtle wax will work.
I would wax the surface with several coats, buff to a shine, then use PVA.
You can get all of this almost anywhere. grocery stores, hardware stores, but walmart should have it all. PVA is green, and it will say poly-vinyl-alcohol on it. I would say under $20 for both. And that will get you plenty.
here is a video of just wax
http://www.youtube.com/watch?v=nsvgaWHPMF4
Thread Starter
Safety Car
Joined: Dec 2008
Posts: 3,588
Likes: 10
From: North New Jersey
I should have clarified. I'm planning on making this a 'plug' and then use it to make the real mold. just in case I want to make more or better if for some reason i screw something up. That way I won't have to do everything over.
If I did do this, where can I find mold release? How expensive is it?
thanks guys.
If I did do this, where can I find mold release? How expensive is it?
thanks guys.
Safety Car
Joined: Sep 2010
Posts: 3,752
Likes: 190
From: Indiana PA
The track I go to the most is Road America. For practice lap times are low 2:40ish. Every 2 mins 40 seconds there are three straights that I get around 145 mph on. Sessions last 20-30 mins and there are five per day. Aero is important to my build and I like to learn and fabricate things as well.
I find it interesting the C4 and C3 have less rear lift at speed compared to the C5/C6.
That being said, I bet my C4 has more than most,as the smooth side of the spare tire carrier directing airflow is NOT in place on my car.
This is a really cool thread, FYI.
Burning Brakes
Joined: Apr 2006
Posts: 1,218
Likes: 7
From: Burleson Texas
Le Mans Master
Joined: Jul 2009
Posts: 7,182
Likes: 101
From: Pendleton IN
The flat sheet is actually flush with the bottom of the bumper. This car also has a speed certification for 170.281 mph. Must have worked a little. LOL
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Thread Starter
Safety Car
Joined: Dec 2008
Posts: 3,588
Likes: 10
From: North New Jersey
So besides fiberglass what other options are there that are cheap?
I found this site that sells abs sheets... a 48in x 96in sheet is only $22...
I just dont know if this can be used due to weight and the ability to "attach" pieces together...
I am just trying to think of other options as well... Fiberglassing a large piece like this isnt going to be easy for a beginner.
http://www.interstateplastics.com/Bl...46%40yahoo.com
I found this site that sells abs sheets... a 48in x 96in sheet is only $22...
I just dont know if this can be used due to weight and the ability to "attach" pieces together...
I am just trying to think of other options as well... Fiberglassing a large piece like this isnt going to be easy for a beginner.
http://www.interstateplastics.com/Bl...46%40yahoo.com
Le Mans Master
Joined: Jul 2009
Posts: 7,182
Likes: 101
From: Pendleton IN
So besides fiberglass what other options are there that are cheap?
I found this site that sells abs sheets... a 48in x 96in sheet is only $22...
I just dont know if this can be used due to weight and the ability to "attach" pieces together...
I am just trying to think of other options as well... Fiberglassing a large piece like this isnt going to be easy for a beginner.
http://www.interstateplastics.com/Bl...46%40yahoo.com
I found this site that sells abs sheets... a 48in x 96in sheet is only $22...
I just dont know if this can be used due to weight and the ability to "attach" pieces together...
I am just trying to think of other options as well... Fiberglassing a large piece like this isnt going to be easy for a beginner.
http://www.interstateplastics.com/Bl...46%40yahoo.com
Thread Starter
Safety Car
Joined: Dec 2008
Posts: 3,588
Likes: 10
From: North New Jersey
Racer
Joined: Oct 2007
Posts: 321
Likes: 0
Started laying the first layer of fiberglass on the finned side... Man this is more time consuming than I thought. I went ahead and decided (based on easiness on my beginner skills, time, and money) that i'd do what dogfish suggested and seal the cardboard inside the glass. With one layer on its pretty dang stiff with the cardboard and all. I think I may end up only doing 2 layers on each side. So glass, glass, cardboard, glass, glass. This will definitely be a longer term project than expected. I'll keep you guys posted. So far its looking real good. It'll still require a lot of bondo and finishing work but thats 'half' the fun right......? ha
Last edited by crzydrumer14; Mar 22, 2012 at 11:03 PM.
Thread Starter
Safety Car
Joined: Dec 2008
Posts: 3,588
Likes: 10
From: North New Jersey
Started laying the first layer of fiberglass on the finned side... Man this is more time consuming than I thought. I went ahead and decided (based on easiness on my beginner skills, time, and money) that i'd do what dogfish suggested and seal the cardboard inside the glass. With one layer on its pretty dang stiff with the cardboard and all. I think I may end up only doing 2 layers on each side. So glass, glass, cardboard, glass, glass. This will definitely be a longer term project than expected. I'll keep you guys posted. So far its looking real good. It'll still require a lot of bondo and finishing work but thats 'half' the fun right......? ha
What weight/type of fiberglass did you end up using? I am curious about the stiffness because I am doing the whole underside of my Vette...
Cant wait to see this finished!!
Racer
Joined: Oct 2007
Posts: 321
Likes: 0
Yeah my original plan was to eventually do a full underbody panel(s) but I may save that for a later date. This stuff aint cheap. As of today it looks like each layer I put on the finned side is gonna cost me about 20 bucks each. I ended up using a little more that 8 ft^2 of fiberglass mat and a full jug of resin and small hardener bottle. I got all my materials from auto zone and home depot so Im not exactly sure what the weight is but it works.
Le Mans Master
Joined: Jul 2009
Posts: 7,182
Likes: 101
From: Pendleton IN
Yeah my original plan was to eventually do a full underbody panel(s) but I may save that for a later date. This stuff aint cheap. As of today it looks like each layer I put on the finned side is gonna cost me about 20 bucks each. I ended up using a little more that 8 ft^2 of fiberglass mat and a full jug of resin and small hardener bottle. I got all my materials from auto zone and home depot so Im not exactly sure what the weight is but it works.
Doing good so far
Last edited by Vette Daddy; Mar 22, 2012 at 11:27 PM.
Thread Starter
Safety Car
Joined: Dec 2008
Posts: 3,588
Likes: 10
From: North New Jersey
Use more matt and less resin. The strength is in the matt, not the resin. Use a stiff paint brush to saturate the matt. The white bristle cheap 2" brushes work best. Spread a thin layer of resin on the dry cardboard first, then lay on the matt. Dab the matt with the bristels until it's just wet. Apply more matt and saturate again.
Doing good so far
Doing good so far
Le Mans Master
Joined: Jul 2009
Posts: 7,182
Likes: 101
From: Pendleton IN
There's no need for saturation of the cardboard. It's only acting as a structure. Just get it wet enough for the matt to stick to. It will help to saturate the matt before you do the dabbing with the brush. The matt and resin from the auto parts store is thin stuff. You'll need three layers on each side. It's only about 1.0 ounce matting at best. Normal fiberglass parts are made from three layers of 1.5 oz matt and industrial resin, which is a thicker viscosity. Heavier bodied.
Burning Brakes
Joined: Apr 2006
Posts: 1,218
Likes: 7
From: Burleson Texas
Started laying the first layer of fiberglass on the finned side... Man this is more time consuming than I thought. I went ahead and decided (based on easiness on my beginner skills, time, and money) that i'd do what dogfish suggested and seal the cardboard inside the glass. With one layer on its pretty dang stiff with the cardboard and all. I think I may end up only doing 2 layers on each side. So glass, glass, cardboard, glass, glass. This will definitely be a longer term project than expected. I'll keep you guys posted. So far its looking real good. It'll still require a lot of bondo and finishing work but thats 'half' the fun right......? ha
http://forums.corvetteforum.com/c4-g...s-of-pics.html
I used 2 of the mat packages for one of these small pods, and about a gallon of resin. Much of it was trimmed, so there was excess waste, but this just shows how much it used. You should probably use much more mat than I did there...
Overall, awesome job! I am keeping an eye on this thread!
And when I get my engine back from the machine shop, I will start on my belly pan and diffuser. Mine will be different cause I put modified c5 Corsa Indy Pace mufflers on it, so the underside rear is completely different than a stock c4.
Thread Starter
Safety Car
Joined: Dec 2008
Posts: 3,588
Likes: 10
From: North New Jersey
Awesome job man. Just a couple pointers... try to trim the glass when its still wet, using some serious scissors, otherwise, its considerbally harder once its cured. And I agree with vettedaddy, you need thicker mat. The stuff from home depot and autozone is way over priced and really thin, its meant for small repair or small structures... like these speaker pods I built...
http://forums.corvetteforum.com/c4-g...s-of-pics.html
I used 2 of the mat packages for one of these small pods, and about a gallon of resin. Much of it was trimmed, so there was excess waste, but this just shows how much it used. You should probably use much more mat than I did there...
Overall, awesome job! I am keeping an eye on this thread!
And when I get my engine back from the machine shop, I will start on my belly pan and diffuser. Mine will be different cause I put modified c5 Corsa Indy Pace mufflers on it, so the underside rear is completely different than a stock c4.
http://forums.corvetteforum.com/c4-g...s-of-pics.html
I used 2 of the mat packages for one of these small pods, and about a gallon of resin. Much of it was trimmed, so there was excess waste, but this just shows how much it used. You should probably use much more mat than I did there...
Overall, awesome job! I am keeping an eye on this thread!
And when I get my engine back from the machine shop, I will start on my belly pan and diffuser. Mine will be different cause I put modified c5 Corsa Indy Pace mufflers on it, so the underside rear is completely different than a stock c4.
Le Mans Master
Joined: Jul 2009
Posts: 7,182
Likes: 101
From: Pendleton IN
If you wait until it's hardened up, just use a cutoff wheel. Then use a sanding block with 80 grit to finish out the edges nicely. Works great.
