This is the chronicle of my home-made hood vent project.
I believe that form should follow function. And since the function of a hood vent is to extract hot air from behind the radiator, a bigger vent should yield more function. But at the same time, I didn't want to cut into the frame to accomodate a deep recessed scoop. And I didn't want a huge bulge sticking out the top of my hood, either.
So I reached a compromise. The idea was to build a scoop that's half recessed and half raised. I hit upon the idea of using the rear decklid as the mold. The hump in the notchback decklid is the perfect shape! The front edge of the hump can be used as the front lip of the scoop. And the back of the hump, turned upside-down, can be recessed into the hood.
So I pulled the decklid off my Fiero and went to work. I washed it twice with degreaser, then applied 4 coats of furniture wax, and finally a light coat of axle grease (just to be safe). In the photo below, you can see the glass fiber cloth being test-fitted onto the decklid hump.
Luckily, the glass fiber conformed to the shape with no problems. So I started the layup process. I used 6 layers of generic glass fiber cloth (available in hardware stores) with epoxy resin. I also used a small roller to smooth it out between layers. This helped to prevent bubbles.
The result looked like this:
Let me tell you, cracking the fiberglass loose from the mold always makes me a bit nervous. This made me especially nervous, because my decklid was at risk! After carefully working the fiberglass loose, I positioned the two pieces how they would be installed in the hood, to see how they look. The top of the photo would be the front of the hood.
I liked the way the two pieces looked, and so continued with the project.
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10:50 PM
PFF
System Bot
Blacktree Member
Posts: 20770 From: Central Florida Registered: Dec 2001
The next step was to cut a hole in the hood. The sides are 2" from the crease lines in the hood. I'm not going to give exact measurements for the front and back edge, for a couple reasons. First of all, the location of the front and back will depend on the size of the scoop pieces you make. And second, there's some room for "artistic expression".
After cutting the hole, I tapered the edges with my angle grinder and a 50-grit sanding disc. The taper is roughly 1" wide all around. This, along with a matching taper on the scoop pieces, will help you create a seamless joint. See the diagram below.
The grinding creates a LOT of dust. You should at least wear a filter mask. Goggles and a long-sleeve shirt would help, too. You've been warned.
After cutting the hole, I test-fitted the scoop pieces inside. I found that the channel for the weatherstrip interfered with the back half of the scoop. So I had to grind it down. In the photo below, the green arrows show where I accidentally went all the way through.
If I had a chance to do this over, I wouldn't put the recessed piece so far back. That would probably eliminate the interference with the weatherstrip channel.
Now that the hood and scoop pieces are ready, it's time to bond them together. I hit the hood and scoop pieces with 100-grit sandpaper, then mixed up a batch of epoxy resin. The resin, along with a single layer of glass fiber cloth, will be used as the adhesive. The glass fiber cloth's absorbancy helps to keep the resin from draining away.
Several clamps and heavy objects were used to hold the pieces in place while the resin cured.
Here's a closeup of the joint. The transition from hood to scoop is almost seamless.
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10:52 PM
Blacktree Member
Posts: 20770 From: Central Florida Registered: Dec 2001
Now I start work on the "fill pieces" between the front and rear section of the scoop. There is about 2" of open space between them. The idea is to make the front and rear sections flow together like they were made from a single piece of fiberglass.
I don't really like free-forming fiberglass. But I didn't have much choice here. Making a mold for such a small thing would be a waste of time and resources. So I stretched a piece of glass fiber cloth across the gap, secured it with masking tape, and wetted it with resin. After it hardens, I can build up some more fiberglass on it.
If you look closely, you can also see the black lines I traced with a marker beforehand. Those curved lines will be the edges of the opening.
You can also see that I had to repair some other damage to the hood. This is a good time to do that.
The next order of business was to fill a slight dip in the center of the scoop. Since the dip wasn't very deep, I decided to fill it with a few layers of fiberglass. I used the edge of a ruler to find the edges of the dip.
The idea here is to start off with a small piece of fiberglass in the middle, then lay a slightly larger piece on top of that, etc, so that the top piece will be nice and flat.
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10:55 PM
Blacktree Member
Posts: 20770 From: Central Florida Registered: Dec 2001
This is as far as I've gotten. What I've posted so far represents about 2 weeks of work. So it could take a week or 2 to complete the project. I'll post updates as they become available.
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10:58 PM
Lambo nut Member
Posts: 4442 From: Centralia,Missouri. USA Registered: Sep 2003
There isn't anything really interesting going on right now... just alot of sanding and some fill work.
Lately, I've been having problems with my resin gelling up too fast. With the sun shining down and 90°F temperature, the stuff goes ballistic. It actually melted the bottom out of a mixing cup!
So I put my resin cup in a big jar of ice-water to keep it cool. It worked! I had plenty of time to finish the layup work. And when the resin hit that hot hood, it warmed up and catalyzed nicely.
I guess you really do learn something every day.
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02:55 PM
Nikemann Member
Posts: 148 From: West Bend, WI Registered: May 2005
Today I cleaned up the edges of the scoop opening, along with some detail sanding. The fabrication work on the topside of the scoop is done. But the underside needs some more fiberglass. After that, I'll be in the home stretch.
Here's a teaser pic:
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02:18 PM
Apr 20th, 2006
Blacktree Member
Posts: 20770 From: Central Florida Registered: Dec 2001
This morning, I laid some putty on the hood. I'm using an Elmer's brand "fiberglass repair kit" that I bought at Lowes. It's epoxy based with a creamy texture, and is relatively easy to spread. Plus, it has a pot life of 20-30 minutes.
would you be willing to make a quick copy (just a few layers of glass ontop of what you have done) ? I really like the idea (as i used the bubble from a decklid for a hoodscoop a few years ago) but I think i'd rather have it the opposite of the way yours is layed out so a copy would be perfect...
pretty please?
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11:35 AM
exoticse Member
Posts: 8654 From: Orlando, Fl Registered: Jun 2003
Thanks to everyone for the compliments. In return, I'll give you some shots of the hood... all one color!
As you can see, the scoop has a low-key look from the front and sides (the photos exaggerate that effect). But when you look at it from the rear, it's like "HELLO!"
I still have plenty of work to do on the hood. There are some minor imperfections, and lots of pinholes from the fiberglass molding process. Plus, I still have to lay some fiberglass on the underside to fill the voids that were created when I chopped that big hole in the hood.
But I'm seeing the light at the end of the tunnel... hope it's not a freight train!
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02:14 PM
Apr 22nd, 2006
Blacktree Member
Posts: 20770 From: Central Florida Registered: Dec 2001
I'm with crazyfieromike, would you consider selling me one.....I would not expect perfect but somthing I could start with along with a little instruction sheet to "Help us along" (yes some men read instructions!) PM me if you would like. Thanks T.J.
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09:54 PM
PFF
System Bot
Apr 23rd, 2006
Blacktree Member
Posts: 20770 From: Central Florida Registered: Dec 2001
crazyfieromike said: any chance of you makeing copies to sell?
Maybe, maybe not. We'll see. Even if I do decide to make a mold, it'll have to wait until after the car is painted (and buffed, and waxed). Until then, I still have plenty of modding to do.
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01:14 PM
RCR Member
Posts: 4409 From: Shelby Twp Mi Registered: Sep 2002
I was gonna do that to my last project (but a buddys GT came u for sale, so Im too busy with it at the moment... that and im considering norms hood) anyhow... Nice set up you got going on there, the lights and this C4 hood are really setting it off IMO... vents pretty inventive too... Nice work
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10:17 PM
Apr 27th, 2006
Blacktree Member
Posts: 20770 From: Central Florida Registered: Dec 2001
cire36 said: You are going to [make] a C4 Corvette style hood where the top half of the fenders open with the hood.
That's right. So far, it's been pretty easy too. Getting the hood and fenders lined up *just right* before bonding them together was a bit tedious, but didn't require any rocket science.
I removed the fender mounting bolts beforehand, and bonded the parts together on the car. This should keep the fenders lined up with the rest of the body. After the fiberglass cures, I'll cut the fenders with my trusty Dremel along the top edge of the moulding. Then I'll be able to open the hood again.
I'll also need to do some fiberglass molding on the underside... and then alot of sanding/grinding/prep work.
[This message has been edited by Blacktree (edited 04-27-2006).]
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11:46 AM
cire36 Member
Posts: 674 From: Rio Rancho, NM Registered: Feb 2002
Just a thought, would it be better to cut below the moulding, that way, the moulding can move with the hood and the lower fender retaining features can be hidden under it (the moulding) when it is closed.
Just a thought.
Thanks for correcting my spelling error.
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04:51 PM
Apr 28th, 2006
Blacktree Member
Posts: 20770 From: Central Florida Registered: Dec 2001
looks like masking tape and a paint stick were your alignment tools (after the fender was detached, before you glassed them to the hood) am i correct ?
[This message has been edited by 88GTFormula (edited 04-30-2006).]
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12:27 AM
LoW_KeY Member
Posts: 8081 From: Hastings, MI Registered: Oct 2001
To Boosted2003: I bought the headlight conversion kit from Kris Munson (PFF username "kmunson56").
To 88GTFormula: Correctamundo. That kept the hood and fender parallel horizontally. I also put shims under the hood in various spots to keep them parallel vertically.
Also, I used the angle grinder on the edges of the hood and fender to create a V-shaped channel. The fiberglass was laid down in that channel. I used 3 layers of glass fiber cloth, with epoxy resin. I had to do it in 2 stages. The first stage is the two strips you see in the photo. The second stage filled in the empty spots where the tape and sticks were.
That by itself seems to be strong enough to hold the hood & fenders together. The fiberglass is actually stiffer than the fender! But I'm also going to layup some fiberglass on the underside (after grinding a similar V-shaped channel). The fenders are kinda floppy, so I may end up reinforcing them.
Tomorrow (or actually later this morning ) I'll show you why I sliced the fender along the top edge of the moulding.
EDIT: It kinda goes without saying, but I removed the radio antenna before starting the fender mod. The antenna will need to be relocated.
[This message has been edited by Blacktree (edited 04-30-2006).]
EDIT: It kinda goes without saying, but I removed the radio antenna before starting the fender mod. The antenna will need to be relocated.
Theres a mod several guys have done just to loose the antenna and they fill in that factory antenna hole with bondo or some other filling agent... Thery mount the antenna above the fender well... I dunno if you've seen this mod or not... But one i get an extra set of fenders, I'm gonna attempt what you did...
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01:43 PM
Blacktree Member
Posts: 20770 From: Central Florida Registered: Dec 2001
WHEW! Wetsanding is alot of work! But my car looks sooooooo sexy now.
Alright, back to business. Here's why I cut the fender along the top of the moulding. There are 2 things that made me decide:
1) If the side marker light is attached to the hood, it will interfere with the frame. You'd need to cut a pretty deep notch in the frame (maybe even all the way through) to make room.
2) The bottom corner of the fender, top corner of the fascia, and wheel well liner are all held together by one screw! The screw goes through the wheel well, then the fascia, and into a body nut in the fender. If the bottom of the fender remained attached to the hood, there would be nothing to hold the top corner of the fascia and the wheel well together.
I'm sure these problems could be overcome with some time & effort. But decided it wasn't worth the trouble. Besides, the black moulding will still camouflage the seams. Black is good at hiding seams.
YaY, got my tom's flushmounts with Kris's covers semi fine tuned... I guess a hood mod similar to this one may be one of my next body mods... and or possibly a vent mod. on the decklid... gotta figure out a few things for the rockers though... We'll see what happens... woohoo
sorry, keep the pics. comin blacktree 'whatcha doing next?'
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09:32 PM
May 6th, 2006
Blacktree Member
Posts: 20770 From: Central Florida Registered: Dec 2001
Well, it's been a few days since my last update. I've haven't had much time to work on the hood. But nonetheless, I've made a bit of progress.
First of all, the vent scoop is practically finished. All that's left is sanding and prep work. This involved molding some fiberglass to fill the empty spaces where the channels in the hood used to be. I crammed some styrofoam into the voids and laid on the fiberglass. Then I chopped up some paint sticks, glued them to the hood, and sanded a nice curve to match the curve of the scoop. Then I laid fiberglass (and some filler) on top. This will provide a nice transition between the underside of the hood and the upward curve of the scoop.
I also took this opportunity to work on the underside of the hood/fender mod. As mentioned before, I laid some fiberglass on the underside of the hood/fender seam. You can see the rough fiberglass seam below.
Notice that the mounting flange (where the top of the fender attached to the frame) is now gone. I chopped it out and ground the area flat.
After the seams are smoothed out, I plan on molding some more fiberglass to fill some awkward-looking spots in the fender. There's also an alterior motive here: filling in those spots will provide a flat mating surface between the upper and lower fender. I can then stick something soft in there (like weatherstripping) to keep the two panels from chaffing. In the photo below, the yellow lines outline that area.
[This message has been edited by Blacktree (edited 05-06-2006).]
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02:31 PM
madcurl Member
Posts: 21401 From: In a Van down by the Kern River Registered: Jul 2003
"Anyone can make a copy of something, it may look good but it ever is the real car, make something from your imagination, something unique, something nobody has, anything is possible and, ideas can be a reality."