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Thread: Trunk lid fit advice please (see pics)

  1. #1
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    Trunk lid fit advice please (see pics)

    Here’s my lid. The top is fine (I need to shave a touch off the bumpers to get it perfect). But the bottom corners stick out. Even when clicked in fully to the latch (in photo it’s not quite matched to make it apparent) it still sticks up at the corners like you see here. It does appear that the shape doesn’t match the body shape just right. They where flush until I put bumpers in the middle of the curve to get it up to and level with the body. Guidance please!


    '33 Hot Rod
    Ordered: 3/25/17. Delivered: 5/6/17. 1st start: 8/24/18

    MK4 Roadster
    Ordered: 7/10/13. Delivered: 8/20/13. Completed: 10/26/15.
    I did everything except spray it. She ain't perfect, but she's mine.

  2. #2
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    A number of people have resorted to bolting square steel tubing to the underside, that has been bent to a sharper radius, so it changes the shape of the lid. Some have even machined fancy aluminum pieces to do the same thing. See post 52.

    http://www.ffcars.com/forums/120-fac...d-706-a-3.html

    Here's another thread:

    http://www.ffcars.com/forums/120-fac...trunk-lid.html

    See post 12:

    http://www.ffcars.com/forums/120-fac...ps-tricks.html

    As some folks have found out, fiberglass can change shape after sitting out in the hot summer sun. When I built my '37 Oze, I assembled the entire car and drove it 1200 miles during the summer while doing the body work. Doing lots of critical fitting before the body has seen some significant heat is usually a bad idea. Getting a waterproof seal around any trunk opening can also be difficult. I used Soffseal E715. The lower legs were a little too long on the outer side and had to be trimmed. A huge number of hours were spent gradually sanding down the vertical drip rail to get the right fit, along with a lot of body filler work. In the end though, my trunk does not leak when being washed or driven in the rain and the fit has not changed.

    I should also note that the gap at the lower edge will change as the shape changes. I tried to keep all gaps down to 1/8".
    Last edited by DaveS53; 01-04-2018 at 05:39 PM.

  3. #3
    EFI Rules and Carbs Drool Arrowhead's Avatar
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    No need to CNC metal brackets or metal reinforcing. A couple ratchet straps, some blocks of wood and the sun are all you need. The fiberglass is pliable under heat and pressure and can be coaxed into taking on a different shape - just not quickly.


    The real trick is to have the panel supported by weather strip or bumpers all the way around once you have corrected the shape. If it's not, will relax in the sun over time and end up reshaping it's self. Never make a latch or hinge force a fiberglass panel into shape when closing. I always fit my panels without latches first. They should only be used to a keep a panel closed, not correct alignment when you shut it. (that goes for metal or glass).

    I didn't realize how pliable it would be and had made relief cuts on the bottom side and then re glassed the cuts after it had been reformed in the sun. Turns out I probably didn't have to and could have performed the reforming with just the straps holding pressure in the sun.
    Attached Images Attached Images

  4. #4
    Seasoned Citizen NAZ's Avatar
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    Had the same issue with mine. Working with fiberglass is new to me and very frustrating. There is nothing about my body that is even close to being symmetrical and I've noticed it has moved around just from setting in the sun. I wonder if it will ever stabilize over time or continue to move.

    Those trunk lids are very flexible and move around in the heat. I never could get mine to cooperate on its own even with weights & straps helping to coax it into shape -- no joy. Fortunately my build included a spoiler and that was the thing I used to not only stiffen up the lid but also reshape it. The radii was off a bunch on all four sides but the spoiler mounting brackets I fabricated are controlling the shape and supporting the lid, at least on three sides now.

    If I were to build another FFR 33 I'd go with the steel body version. Like a good dog you can train steel to "stay".

    Good luck.

  5. #5
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    I made a frame of 3/4" sq. tube that I bent over a platen I cut from MDF. It's fairly easy to do and it will let you hold the exact right curve to fit the body.
    I made mine with a complete 4 sided assy. so it helped stop the flex at the trunk latch and let me use lift supports without worry that they would eventually
    reshape the lid out in the sun under a constant strain. I also used Mazda 3 trunk hinges because they are cheap, strong, compact and have the integral
    mount for the lift supports. Getting rid of those BIG hoop style hinges also gave me back a lot of trunk space.
    thframeliftrs1.JPG
    DSCF2069.JPG

  6. #6
    Ol Skool
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    Mine wasn't quite that far off. I set the latch and hinges without getting things too tweeked. Then just the lower corners stuck up so I pulled them in by putting Quarter Turn fasteners in. Of course I'm not in a hurry to get it painted. The Roof, Hood, and trunk all needed time in the sun with "encouragement" like ratchet straps, push/pull clamps, and quarter turn fasteners. I made my hood and it really warped bad, but, I left it strapped in place out in the sun and then after I got some engine heat under it, it conformed nicely. Fiberglass likes warm weather...

  7. #7
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    FWIW, my Oze fiberglass body no longer seems to move. It's been in the sun in 2015, before paint, 2016 and 2017 after paint. I'm sure that the body is not made from super-duper vinyl ester resin like FFR bodies, probably isothalic tooling resin, which has good heat resistance. My trunk lid is quite a bit larger and apparently quite a bit stronger, since the inner skin makes the trunk about 2 inches thick. There's no coaxing it to change shape. Fortunately, I just had to add a lot of reinforced filler to the lower right area.

    I see nothing wrong with adding metal supports, if that's what it takes to strengthen the lid so it won't change shape on it's own. Steel isn't the best metal, since the expansion rate is far less than fiberglass. Aluminum would be better with regard to expansion, but it has 1/3 the strength.

  8. #8
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    Thanks for the advice guys. I think going to do both. Ratchet strap and some sun (once the weather warms back up anyway) and once the shape is right I may make it permanent with some reinforcement. I already have some other area I want to reinforce anyway so the trunk lid will get added to the list.

    Maybe I won’t have to wait though. I’ve got 1000w lamps I use to warm my water pump shed during freezes. I bet they would help it get warm to pull into shape.
    '33 Hot Rod
    Ordered: 3/25/17. Delivered: 5/6/17. 1st start: 8/24/18

    MK4 Roadster
    Ordered: 7/10/13. Delivered: 8/20/13. Completed: 10/26/15.
    I did everything except spray it. She ain't perfect, but she's mine.

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