Hood scoop bonding questions

[383 240z]

I just bought a hood scoop for another car of mine. It is an 87 RX-7. the scoop is a 4" cowl induction style that was designed for a flat hood the rx's hood is curved. does anybody have any ideas on how to mate these two surfaces? I was thinking about cutting the glass at the same curve as the hood but then how do I transfer the curve? then how do I attach it? I will post some pix if this will help you all in understanding my poor grammer and inability to articulate (sp) what I am seeing into what I'm saying. Keith

[blueovalz]

Here is what I would do. First cover the hood (and good paint) with 2" masking tape, with a minimum of overlap between runs. This will protect the paint from the resin of the fiberglass (cover a very large area). Next, determine the maximum thickness of the gap at any one spot on the scoop as placed onto the hood (for example if the bottom of the scoop is flat, but the hood is curved, you may have 1/4" in front and in back under the scoop that is not touching the hood when the scoop is physically resting on the hood. Next cut out enough mat so that it can be placed between the hood and the scoop and fill in any and all gaps. Next lay a couple of complete layers of mat that will be of an area of the entire scoop footprint (resin soaked) onto the hood (an outline from a Sharpie of where the scoop is going will orient you very well. Next, place resin soaked pieces that are appropriately cut out to fill in the gaps. Now place the scoop onto the wet resin (make sure you rough up the bottom of the scoop with, say, 36 grit sandpaper) firmly in place without distorting the shape of the hood. You will still be able to see the Sharpie outline originally drawn on the tape through the wet mat. Let it kick (but not fully because it will be much easier to pop it off the tape if caught just when the resin has just had a good time to gel, but not get glassy hard), then peel it off the tape (or the tape may come with it) and sand the edges to be flush with the scoops sides. Now the bottom of the scoop matches perfectly the contour of the hood where you want to place the scoop. And if you really want to do it right, before you start, drill holes in the hood for bolts, the when the scoop is in place over the holes, mark the bottom of the scoop, drill, tap, and insert heli-coils into the fiberglass so that the scoop can be bolted to the hood. It will now never crack, or separate (as on a bonded scoop). This method is how I did this scoop:

[383 240z]

I think I understand what you are saying. but the gaps on this is more like 2" in the front and two in the back. If I put the front flush the back is about 4" off the surface. I love the hood in the pix you posted. This scoop is pretty big and poorly made there are a bunch of pin holes in the gel coat and has 1.5" wide 90* bend down both sides (left,right, and front). I really like the idea of bolting the scoop down. I was going to cut the "flange" off the scoop and transfer the contour of the hood to the scoop and glass some bolts to the inside of whats left and bolt it down. I will try to take some photos to show you what I have. Keith

[Guest Anonymous]

Terry is the fiberglass expert around here. What little I learned was from Lone who got his info from Terry. 4 inch gaps ! I have been using roof sheathing ( thin sheet metal) from Home Depot that comes in various size rolls to make fiberglass flat molds,flanges and repairs. This roll sheathing is electrically galvanized ( very smooth) and fiber glass does not stick to it. Place your scoop on the hood and temporarily secure it .Get a roll of 6 inch sheathing and fit it to the outside of the scoop with dry wall screws so the bottom ends meet the hood (trim to fit with tin snips or stout scissors). Remove the scoop with the sheathing in place. From the inside of the scoop lay in fiber glass cloth to the scoop and onto the metal sheathing which will act as a "flat mold" to fill the gap area. (Clean and prepare the fiberglass for bonding as Terry instructed) Remove the metal sheathing after fiberglass cure which should leave you a fairly smooth outside surface after some minor fill in with glass fiber filled fiberglass resin gel. Now follow Terry's instructions on mounting the scoop. You can also use the roll sheathing bent in 90 degree angles as a flat mold to form inside flanges to the scoop by attaching the sheathing angle by drywall screws to the inside and fiberglassing overthe bottom of the sheathing. Remove metal and you will have nice smooth flange. Self tapping screws work great Terry's idea is better in fitting the scoop to the hood.

[Guest Z-rific]

I like rivets for this type of work also, if you can make some minor indentions in the fiberglass. And with the amount of glass you'll be building it may be possible to file some areas for rivets. Use only metal rivets, not aluminum. Either rivets or bolts makes the whole assembly much stronger.

 

Of course, Terry dwarfs my knowledge of glass, so go his route if you are unsure if this will work.

[Guest Anonymous]

I have using a device known as "T nuts" that is imbedded by drilling a hole in wood and driving in the the T nut to attach or join various parts or objects to wood.I cut off the the four little nails of the T nut and use the threaded nut and integral washer im-bedded in the fiberglass or welded to metal to attach fiberglass panels. Various regular threaded fastners/bolts can be used