Fiberglass Hood Panel
Description

1. The under side of a hood and trunk lid are often the most neglected part of a custom car or truck. The factory had no intention of making this area look nice. Our project is a’70 Ford Torino hood which features a fiberglass duct that runs across the middle and sticks down in to the engine bay. Sad to say, but Ford did not have “A Better Idea” on this one. This hood is a great candidate to show our techniques for building a custom cover because it has so many contours and close tolerances to clear the engine. Lets get started!


2. Some of the materials needed are as follows, 5 gallon polyester resin, vinyl gloves, large and small disposable paint brushes for resin application. Air bubble roller, masking tape, Tyvek spray suit, razor blades. Etc


3. 3M Plastic car cover works good as a masking agent and resins release from it pretty easily.


4. Chopped Strand Mat, this close up shows how the strands go in all directions. It is available in different thickness / ounce levels. The thicker you go the more strength you have with less applications needed, but the less flexibility it has to contour to convex and concave shapes. As with all fiberglass work it is best used in conjunction with Screen Matting for maximum strength. Search the internet for a supplier near you.


5. Screen matting has excellent contouring abilities compared to strand mat. It also sells in different ounce levels which changes the thickness. In general it is a thinner product then chop strand and is usually applied on top of the chopped strand as it gives a smoother surface after it cures. Use it as the second layer over each chop matt layer for max strength. I also use this screen for small touch ups on tight areas by itself.


6. Jeff started out by taping off the areas where the outer edges of the panel will be located. 3M green tape has the best adhesion but does not release from the surface as easily as the blue painters tape.


7. Depending on how many unusual shapes you have, a heat gun may be needed to assist in pressing out the tape for a skin tight fit. A mold it only as good as the prep you put in to it. Avoid wrinkles and lines as they will show up in the finished product.

8. We flipped the hood over bottom side up for easy access while building our new panel. Notice the 4 inch thick foam pads we use to support the hoods weight. This supports the panel with out causing damage to the outer sheet metal. We also pulled the foam apart to allow clearance for the scoop to rest untouched.

 

9. We have the outer edge taped off tight and are now ready to shape our inner section,.


10. We placed the 3M plastic inside our hood section to keep any resin from sticking to the steel hood and we are ready to proceed! Be sure and pull it somewhat tight to minimize wrinkling.


11. Jeff lays out some polyester material purchased from a fabric store. We like a heavy weight poly that can be stretched if needed but will also allow swooping contours. It is also important to use a heavy enough material that will support the weight of the resin applied and still keep its shape without sagging.


12. A close up shows the cross hatching pattern of this poly, The larger the perfs or holes the more it stretches. The more it stretches the less it will hold its shape after resin is applied to it.


13. We cut back the edges using scissors and tape in to place on a few edges to get an idea where it will lay out in to the shape we desire.


14. Where the fiberglass factory scoop protrudes in to the engine bay we added a few pieces of tape in order to keep the poly from folding around this area. This will act as a bit of support.


15. As seen in the back section we have about a 3 inch drop which will provide ample clearance between our engine air cleaner and hood panel.

 

16. Once it lays out you want to look it over and adjust the tape so the poly is shaped enough to give you the gradual swooping contours while retaining enough spring tension to overcome the weight of the resin we will be applying.


17. At the front section we have one inch which will do the job. We have a nice slope side to side and front to back. We are now ready to apply a very light coat of resin.


18. We mixed up about one quart of resin with MEK hardener per the MFG specs. Notice we are using a smaller application brush. This enables us to coat the poly with just enough resin to make it a mold that will support the fiberglass matting once dried. Too big a brush means more resin and you will then soak the poly too much which will make it weighty and sag in areas you do not want. Apply very sparingly just enough to wet the thickness of the poly.

 

19. She is coated and ready to cure. Now is the time to pull the material a bit here and there if needed by releasing and repositioning the two inch tape. If you notice it sagging a bit to much, pull the tape in that needed area. If it is too taunt then release the tape and let the weight of the resin swoop the material down more in the area you desire. If you are working in a hot climate, only mix 2/3rd of the hardener in your cup per mfg so you have ample/more time to mix and coat, re-adjust and tape down as needed.


20. Our polyester mold is cured and will keep our contoured shape while supporting the extra weight of the glass matting once soaked with resin. We will start with the chopped strand then the screen mat and then back to the chop and again screen 2 to 3 sheets each. This combination makes a very strong panel at just under 3/16th of an inch thick. It will keep its shape and not bend or sag from gravity weight after final installation. We start by building the center areas first and will finish the outer perimeter last. This allows us to release the panel from our hood easier. Note! We fog blasted the panel for adhesion between rounds, this is important for max adhesion.

21. This matting procedure calls for a large resin brush as seen. We coat it thoroughly saturating all the fiberglass strands.

22.  Air bubbles can get trapped when hand laying fiberglass glass down but we have the remedy. These must be removed for a perfect panel.

23. After the matting is applied take a “glass mat roller” and work out the air bubbles. Work aggressively as the clock is ticking and you need ample time to get it all worked out before the resin starts to kick-cure.

24. We let it cure for 2 hours then Shannon lifted up the panel away from the hood. She looks good. The masking tape keeps oxygen from the surface which can tend to keep it from curing completely and as quickly as the open sections. Once you pull the mold up and away from the surface it will finish curing in those areas.

25.  As seen we have a nice release from the sheet metal with no problems removing the panel.

26. The 3M plastic simply peels away from the fiberglass mold.

 

27. Using a roloc 40 grit disc on an angle grinder we knocked down wrinkles on the back side from the resin on our mold.

28. Once again we combo the matting for max strength. This is the same procedure Boat MFG’s use. 1. Be sure and lightly scuff grind or fog blast the dried panel between matting applications. This will give you max adhesion. 2. If the panel is tacky and still curing then adhesion will be fine directly on top of the panel. 3. Depending on the brand of resin once dried you can wipe down the area with acetone and if the panel gets tacky that will also allow good adhesion. But in general #1 is the best way of securing max adhesion between applications.

29. As seen at the “red arrows” the outer edges of the support plate is sandwiched between the fiberglass layers. The tab is 1/8th thick and simply slips in to the black cut out groove to hold the front section of the panel in place with no detection of fasteners.

30 . We go on to the trunk lid to discuss some different techniques. As seen we used 2 inch masking tape to get our mold close to what we were looking for as the deck lid had the usual dips and low places between the braces and we want a smoother flatter panel.

31. A close up shows the angled side sections where the hinge bolts are located. As seen “red arrows” the hinge supports are covered so the fiberglass panel will be installed after the deck lid is put on. The hinge bolts will be completely covered for a smoother no fastener look.

32. Once you apply the polyester you can pull it some until a nice transition is formed as seen in the slightly lighter shade “black arrow” it is actually one inch away from the tape at this point. Behind this location is where the latch is installed so no fasteners will be visible here either.

33. The hinge insertion hole needs to be cut away on our panel. “black arrows” In addition the hinge attaching bolts are covered by the panel for a cosmetic upgrade.

34. Our mold dried up and we trimmed it around the edges for a preliminary fit. The area marked is where the hinge will slip up into the trunk. We simply use a drill for a 1/4 hole then burr tool the glass away in this area.

35. As seen on the green tape line we want to trim a bit more before we attach the Trunk lid to the car for our initial clearance check. The hinge cut out has been trimmed and she is about ready.

36. Just like the hood in order to hide any fasteners apparent to the eye we built a guide holding system for the trunk panel which features 1/4 stainless pins with a vertical strap. We simply blasted the surface once fitted and used Evercoat Vette Panel adhesive to attach the strap to our panel. We then laid down a bit more matting to cover this. These pins will insert at the very back of the trunk lid.

37. Once attached you can see how the pins protrude from the panel. To attach the panel after the trunk lid is installed we tilt the panel down toward the front of the car and push the pins in to the back of our trunk lid alignment holes. We then swing up the section at the rear and attach two screws to the bottom edge of the trunk lid. Those screws will be hard to detect when standing at the back of the car. We also installed two more screws in the center that will be located under a cosmetic trim piece.

38. This a forester bit used in wood working. This allows a recessed area in the glass to attach the panel support screws as mentioned on each side they will be below the surface. The cosmetic piece which will be painted and or upholstered will simply snap on with door panel clips to cover these screws.

39. Once the screw is installed you can see how it is below the surface just a bit.

40. When trimming the edges to get it close or achieve rubber seal fit we simply follow our taped edge with by using a small angle grinder with 3M roloc 40 grit disc, They work great, are aggressive but do not chew up the edge of the fiberglass.

41. When you want to finish the edge to a nice burr free line finish off with a block sander using 80-120 grit.

 

42. Ahh- yes the first trial fit. On deck lids especially it is pretty much impossible to see how it fits from the underside. The rubber seal section needs to be clear of the glass panel. If you have room in your trunk you can get inside, then have a buddy close the lid while you mark it using a light but if you have a speaker box such as our project then you will need a borescope. This pro-vision unit is inexpensive and allows you to look up inside any panel on your project to see what is going on for clearance and inspections etc.

43. Shannon made a note where he needed some clearance and scribes it with a straight edge. Be careful to only cut off small amounts at a time because it is hard to add material..

 

44. Another little trick we use is rope caulk to check the thickness/clearance such as the distance between the custom subwoofer box and our deck lid panel cover. As seen we have quashed the material in a few areas so we need to grind the deck lid cover back for 1/8th minimum clearance to allow room once painted.

45. You can pick this stuff up at any depot or lowes hardware and it is only afew bucks per box.

46. On the hood we added our cosmetic “boomerang bird” trim to match the outer hood edge. This covers over the hidden attaching screws “ black arrows” and under the bottom edge of the hood by the windshield which will also go undetected. The ‘red arrows” show the location of the hidden 1/8th thick flat stock guides as seen in Caption #29 She is now ready for a quick smoothing then upholstery to finish her out. Bon Appetite!

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12/20/2017 (12/20/2017)
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Texas, United States
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