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Old 09-24-2007, 04:29 PM
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Fiberglassing a hood scoop on a metal hood

In the past when I have tried to fiberglass a fiberglass hood scoop to a metal hood it ends up cracking at the point the fiberglass scoop meets the hood. We used three layers of mesh and rolled out the bubbles. In every case I have seen this done it has cracked in time. Is there a process that works?

Bob

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Old 09-24-2007, 04:33 PM
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About the best way I have found is to pop rivet the scoop in place then do the glass..metal and fiberglass have different expansion rates when exposed to heating and cooling so that can be a source of your difficulty..

Sam
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Old 09-24-2007, 04:47 PM
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Like Sam was saying pop rivet it down real good but I would use bondo instead of fiberglass , thats how we did them in the late 60's. use the bondo to blend the scoop to the hood. Bondo has evolved alot since the 60's also.
Gene
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Old 09-24-2007, 05:14 PM
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Actually some of the nicest installs I have seen was to lay out the fasteners so they were evenly spaced and just let it go that way..with no bondo or any thing..a bit of a different look that some might like..Use some small stainless screws or bolts when doing it that way..

Sam
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Old 09-24-2007, 07:34 PM
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Quote:
Originally Posted by OneMoreTime
Actually some of the nicest installs I have seen was to lay out the fasteners so they were evenly spaced and just let it go that way..with no bondo or any thing..a bit of a different look that some might like..Use some small stainless screws or bolts when doing it that way..

Sam
true. it gives it an aircraft look.
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Old 09-24-2007, 07:45 PM
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hood scoops......

polyester resin and metal are not compatible.period,for a SLIGHT chance of sucess,use only epoxy resins,and drill small holes in the scoop flange,for the epoxy to go thru,or,like was said in other posts.RIVET IT.
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Old 09-24-2007, 08:03 PM
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I put one on a metal hood,I roughed up the metal with 36 grit,In put a layer of dynoglass on the hood in laid the scoop on the hood in put something on top the scoop to hold it down,Then i came back in did the body work.In that was over ten years ago,in never cracked. Hope this helps.
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Old 09-24-2007, 08:41 PM
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Anyone ever use the all-metal filler by US Chemical?
Shane
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Old 09-24-2007, 08:41 PM
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Fusor makes an excelleny adhesive for this, then you use traditional mat and fillers to blend it into the hood. I did a step by step on this awhile back and I'll see if I can find it. The fusor stuff works good and it's designed for use over epoxy primer-I've never seen a failure.
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Old 09-24-2007, 08:52 PM
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You've got some work ahead of you getting this scoop on right, here's a run down on what you'll need to do.

Trial fit the scoop to the hood and make some reference marks so you can test fit it and locate it in the same spot each time it goes on. If the contour of the scoop does not fit the shape of the hood you'll need to modify the scoop untill it does. Getting the scoop to fit well is key to success before you bond it on. If you need to trim the scoop or add material do it, the scoop shouldn't have any stress on it when installed. Once the scoop fits the hood properly drill holes through the mounting flange every 4 inches and test fit with screws. If the fit is good your ready to prepare for the adhesive. If the hood has oem paint on it and the paint is in good condition just DA it with 80 grit. If the hood has a repaint on it or paint that is in poor condition you'll need to DA it to bare metal in the bonding area and apply two coats of epoxy. Let the epoxy setup overnight. Sand the underside of the mounting flange with 80 grit. Clean both mating surfaces- blow them off with compressed air then wax and grease remover then compressed air again. Apply a good sized bead of adhesive and set the scoop on the hood. Install your screws from the front working your way back. Don't overtighten the screws and push all the adhesive out- there needs to be adhesive between the flange and hood- .010 to .020" would be good. Let the adhesive setup overnight. Then remove the screws and with a 3" grinder remove all of the excess adhesive that has squished out. Grind the flange down around the perimeter slowly so you don't create a lot of heat. The flange needs to be ground so it tapers from full thickness out to paper thin at the outside edge. Remove any exposed adhesive. Use a 5/16" drill bit or a burr bit and countersink the screw holes slightly. Cut yourself some fiberglass mat strips and mix up some resin. The first layer of mat needs to go on the hood just outside of the flange, next layer should overlap the first and also 50% of the flange, third layer needs to overlap the second and 100% of the flange. Let this setup then rough shape with a grinder. Then apply a coat of Everglass over the complete bond area and shape with a half round cheese grater. Finish with regular body filler and glaze coat then prime. You'll need to apply some urethane seamsealer around the inside perimeter of the scoop to keep moisture from entering the seam and freezing (North Country). Also some drain holes towards the front of the scoop is usually a good idea. To do this job right figure on spending 4-5 weeknights. Hope this made sense.
Fusor 127EZ is what you need
http://www.lord.com/Default.aspx?tabid=1193#127EZ128EZ Bob
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Old 09-25-2007, 01:58 PM
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Fiberglassing

Thank you for the help. This site has been a life saver during the build of my Monza (check out my journal). I bought a fiberglass hood from Show Cars Unlimited but the quality is so bad I don't think I can use it. I would have to split the hood down the center and re-glass it back together just to get it to remotely fit. Then the quality of the fiberglass is horrible. I will save 7 lbs by using the fiberglass hood and I just don't think it is worth it. When I look at bad fiberglass work, horrible fit and at least 150 hrs work on the glass hood the stock hood is looking real good.

Bob
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Old 09-25-2007, 07:22 PM
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7 lbs ...... just leave it about a gallon shy of full.......and you'll save about $3.009 every fillup.
Shane
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