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Old 06-06-2005, 07:36 AM
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fiberglass to fiberglass scoop

I've searched and I know that trying to bond fiberglass to metal has been covered over and over but I need to install a fiberglass cowl scoop to a fiberglass hood and I'm clueless as to where to begin. This is an exterior mount so I need to mold it to the hood smoothly enough to paint. Can anyone steer me toward some info. that would help? Please, keep in mind that I know NOTHING about fiberglass.
Peg
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Old 06-06-2005, 09:16 AM
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I am not a pro at this, but I did some fiberglass to fiberglass molding and I found that the fabric (fiber) and resin works best. You can buy sheets of fabric for fiberglass at your local auto parts store and there is a resin you use to make a "sandwich" of resin and fiber that when hardened becomes fiberglass...

I usually use/make some type of support system (skeleton) out of some aluminum strips and pop rivet it to the original pieces. This will give me a basic shape to work with then I just have to bridge the gaps (seams) with some cloth and resin. I lay out my fiber cloth on the project and cut out a piece of the fiber large enough to go at least a few inches past the seam. Then I follow the instructions on the can of fiberglass resin. I usually do an application of the cloth and resin on the inside of the skeleton first, then attach the unit to whatever I am attaching it to and then apply cloth and resin on the outside. Sand smooth, prime, and paint.
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Old 06-06-2005, 09:47 AM
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Some hints

It would be helpful if we knew that you are just putting on a scoop or are you building something like a Ram Aire IV that is a cold air scoop..

But I digress..place the scoop in the desired location and mark it with a sharp scribe..then cut the hood opening with a saber saw and file the edges until the scoop fits exactly in the opening..

Turn the hood over and sand with some 60 grit till any nasys are gone and do this to the scoop as well about 3-4 inches back from the edge..make it really clean..

Then make some "clamp strips" from sheet metal and screw those from the outside of the hood and scoop to hold the scoop in place..those will go away once the lamination is completed..about 3/4 by 2 1/2 inch strips of metal will do and screw them down with some short #8 sheet metal screws..helps to predrill those as starting a screw in fiberglass is hard..

The turn the hood upside down and start laminating across the joint..I start with a 3/4 ounce mat..then a layer of glass cloth..then another mat..another cloth and so on till Ihave a good secure layer across the joint..

Once that is cured out flip the hood back over..remove the metal strips and fill the holes with bondo and proceed with paint..if you have a good fit the scoop flange witl be flush with the hood and it will take very little bondo the get the scoop faired into the hood..looks like it was made that way once it is painted..


Ram Aire IV styles require that you buidl an airbox on the carb with a rubber gasket that fits exactly up to the bottom of the hood so only cold air gets to the carb..those are a bit more complex..

Kinda long answer but maybe helps you get the drift..

Probably you can find enough glass and resin in one of those hardware store boat repair kits for a job of this size..

Good luck..send pics..

OMT
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Old 06-06-2005, 09:54 AM
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Check out this link to Unlimited Products Site...
http://www.up22.com/ScoopInstall.htm
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Old 06-06-2005, 02:23 PM
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Thanks for the replies! Let me see if I can explain what I'm trying to do. This is a cowl scoop to go on a 86' Regal hood, both are fiberglass. What I need to do is get more clearance for the carb., this is a drag car, and I'd like to cut down on the air turbulence at the same time. So, my plan is to only cut a hole in the hood large enough to allow the top of the carburetor to come up into the new space made by the cowl.
I guess in a nutshell, what I'm trying to do is only cut a dinner plate sized hole in the hood and mount the cowl strictly on the top side of the hood. The cowl is 6" tall and has about a 2" flange on three sides, the back is open. Since all the fiberglass will be on the outside of the hood I assume I'll have to "step" the fiberglass down in thickness to blend back in with the original shape of the hood and that's the part I'm really confused about. I don't know if I should be able to do that 2" out from the flange or if it would take a foot on either side. Someone told me to pop rivet it before doing the fiberglass but is that necessary? Wouldn't it just add to the thickness that I'd need to mold back in? Did I mention that I'm clueless? lol
I've taken some photos of the cowl sitting on the hood and I'll try to get them up here later tonight or in the morning if that will help.
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Old 06-06-2005, 03:11 PM
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Let's see if I can figure out how to get ya'll a photo or two.....

cowl1
cowl2

As you can see there's not a lot of room on the hood until you either run off the edge or hit a body line so that's why I'm worried about how far out I'll have to go to blend this thing in and make it look like it's always been there.
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Old 06-06-2005, 03:41 PM
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No Joy!!!

And the cowl flange does not appear to fit down on the hood either...

Ok Now we need to do the hard thing..

You can cut the flange entirely off of the scoop and scribe to fit the scoop to the hood...Be sure and grind off the gel coat and get to solid glass..

Now glue the scoop to he hood with hot glue and then make a fillet with bondo at the intersection of the hood and scoop..using something rounded like a tonque depressor will work..use the knd of bondo with kitty hair..

Then make your layup over the fillet and running up the scoop about 2' and out on to the hood about the same..once that has cured then you are up for some sanding to get it nice and smooth and faired in so it looks right..

On the inside of the scoop it is a good idea to work some glass into that part of the joint as well..maybe it is overkill but then it is less likely to crack..use a small disposabe brush taped to a long stick and you can get the glass mat strips worked in there..wet the glass strips out on a piece of wax paper and lay them in wet works better..

Doing it this way should allow you to install the scoop and not run out to the body lines..and give a nice faired in appearance..

This is fairly common for glass parts to not fit up "just right" specially when they are gotten from different sources..

Good luck...

OMT
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Old 06-06-2005, 06:18 PM
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The fit-up of the scoop doesn't look that bad. Leave the flange on the scoop and grind it down thin, feathering it out from about half the width. The flange will give you a place to "glue" the scoop into the hood and thinning it down will allow it settle down to the hood contours. The thinning also cuts down on the "step" between the two surfaces.
Rough up the flange, top and bottom, and the mating surface of the hood with a 36 grit disc on a grinder. I would use a good fiberglass panel adhesive or 3M's industrial adhesive to glue the scoop down. Drill a few holes at 6" intervals and use some sheet metal screws to help pull the scoop down to the hood.
Let the adhesive set-up, remove the screws, and then grind the edge of the flange to further blend it into the hood. Cut some strips of glass mat into 1", 1 1/2" and 2" wide strips. Slather the joint with resin and lay in the 1" strips. Work the resin in with cheap paint brushes. Buy a bunch at Harbor Freight. Let that set-up then smooth it a bit with the grinder. Do the same thing with the other strips working up the 2" wide pieces. This should be enough to smooth the edge of the scoop into the hood and give you some room for blending with the grinder. Remember to fill all of the screw holes also.
Smooth everything out with a board sander and 180 grit paper and hit the glass with some polyester putty. Further smooth it with some 220 grit. You should be ready for a good primer surface now. Lay on a couple of heavy coats over the entire hood (after you prep it) and block it out with the 220 again. I know this is pretty simplistic but you'll pick up on it as you do it.
Also, you will be doing a lot of sanding so wear long sleeves and a respirator when working with glass.
Mark
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Old 06-06-2005, 09:07 PM
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I've installed one of those scoops on a 79 Malibu and fought with the same fit problems.
[IMG][/IMG]

I trimmed to front flange back some and built an inner flange for the front, there were also some mods to the very rear as well. Took quite a few hours to get the scoop fitting in a relaxed state. The scoop went on an original steel hood, a hole just larger than the 14" air cleaner was cut and I trimmed the bracing back a little more. I then made and airpan to fit over the carb that got sandwiched when the air cleaner was installed. Only about 3/4" of foam was needed around the perimeter to seal the airpan to the bottom of the hood. This was with a Bigblock with a team G intake and dominator carb. The customer noticed no improvement in quarter mile times running the car with no hood and again with the hood and scoop airpan deal.
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Old 06-06-2005, 10:39 PM
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do it the NASCAR way
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Old 06-07-2005, 06:24 AM
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Wow! Thanks for all the info! I'm a little overwhelmed. It will take me some time, and some more coffee, to be able to completely process all this but I do have a couple of questions now.

Am I right in assuming that the cowl shouldn't be under any strain when it's fastened down? There is a good bit of space between the flange and the hood but it does appear to just be because the flange is curled upward. I guess I could try grinding it down first to see if that's enough to make it relax down. If it doesn't then I can always cut the flange off and trim the cowl as needed. Very good guys! You've given me a place to start. I'm sure I'll have tons of questions as I go along but it may be a week or two before I have time to start on the hood.

Now I'm going to complicate things again....the hood has always wanted to sag a little in the middle, from side to side, so that it is slightly below the top of the fenders. I solved the problem temporarily by putting some padded brackets on the inside of the fenders for it to rest on. I'm concerned that the extra weight of the cowl will only make the problem worse but I've been told that if it's installed correctly it will actually make the hood stronger. I'm not sure. Any opinions on that? Should I consider reinforcing the hood from the underside before installing the cowl or do I just need to make sure that the hood isn't sagging when I put the cowl on?

Bob, I'm surprised that they didn't see an improvement but I'm sure I'll get one out of the fat plate I'm going to be putting under the carb. That Bu looks like it would be a bad ride! Do you have any photos of the whole car?

Grouch, does that tape come in purple? lol
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Old 06-07-2005, 07:03 AM
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Choices choices

well it comes down to what is desired in the final product and how much time one has to put into the hood..

Easy way is to just grind the flanges a bit..slather on some 3M huckum--pucky and pop rivet the dude and go racing..

Now if you wish to get it to look "just right" then support the hood so it has the correct curve to it and fits well..scribe the scoop into place and then glass it down...you can support the hood on the car with some blocks and shims and then gently close the hood down...

The addition of the scoop will make it somewhat stronger..hopefully it will hold its shape..

One of the issues with automotive glass is that it is desirable to have it lite..but then we lose the structure..ever seen a funny car body just blow off..Lack of structure is what does that..

You may wind up putting a rib across the hood to help it a bit..make one of those from a piece of 1/4" ply and glass over it..on the underside of the hood of course..

Just how much work you want to do depends on just "how right" you wish the final product to be..

OMT
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Old 06-07-2005, 07:09 AM
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A good friend used a simular cowl add on on his 67 Camaro and the guy cut the hood out and used an adhesive to "glue" the scoop on from underneith with the flange around the edge of the scoop.Looked great. He was meticulious with the cut and outside of a small seam(which will get filled before paint) was a beautiful fit.
Not sure what he used for the adhesive,but I'll try and find out.

We fab'd a "U" brace mounted to the cowl area below the windshield to support the back of the hood which the top of the cowl opening rests on this.
Ours is a 4 pin lift off and this really helped with the support of the back end.

As for sealing the carb to this style hood,IMO It defeats the purpose of the cowl design. A front opening scoop does need sealing.On a cowl hood I don't see the reasoning behind that.Come to think of it,I don't recall seeing ANY car's running cowl's that are sealed.
We run a Tunnel Ram was our reason to go with one in the first place.
Course,this will change after we stuff the 496 BB in it.

Last edited by Bee4Me; 06-07-2005 at 07:20 AM.
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Old 06-07-2005, 10:53 AM
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Quote:
Originally Posted by bluebu
[. . . snip . . . ]
Grouch, does that tape come in purple? lol
Sure, 12 colors.

I don't know diddly about fiberglas (see my egg in my project journal for proof), but this little trim trick from carpentry might help fit that cowl:

Get the hood unsagged (that a word?) by propping it the way you want it, position the cowl to suit you, temporarily and very gently duct tape it in place WITHOUT deforming the flanges or straining anything. Now find something about the same thickness as the height of the largest gap. Lay it on the hood inside the cowl, lay a marker across it and slide it along the hood inside the entire perimeter of the cowl. Trim to the line and it should perfectly match your hood -- wrinkle, wave and ding.

For the fiberglassing... see OneMoreTime.
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Old 06-07-2005, 12:31 PM
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Good glass

Grouch,
Your egg is a good example of a one off type deal..good job BTW..

And the trick with the scribe is a good one use it all the time..

OMT
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