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  1. #1
    Bill 98nightmare's Avatar
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    Cool Stepside beds and dually fender repair. SMC not fiberglass..

    Most people use fiberglass to shave the steps, gas door and even tail lights.. even bonding roll pans. This info will tell you why it always cracks.. Do NOT use fiberglass on ANY late 70s and up Chevy panels that look like fiberglass. They are actually made from a product called SMC. Hopefully this will explain the great myths of how to fix or customize stepside beds and or dually fenders...






    A new composite material is gaining widespread use in the automotive, industrial, and personal watercraft markets that presents unique repair problems. It is called SMC, or Sheet Molded Compound. Recognizing SMC from other types of FRP composites is critical so the proper repair can be performed. Parts made with SMC are produced in compression molds, so they are smooth on both the inside and outside. That is the first clue to look for when identifying them. Next, SMC parts do not have an outer gel coat, but they are usually painted or color molded. When the paint is sanded off, the underlying surface has a marble appearance. Finally, when damaged SMC is sanded, short coarse fibers are exposed and a dryer powdery dust is produced compared to conventional materials. These hints will make SMC identification quite straightforward. SMC is a polyester-based material, but it cannot be repaired with polyester resin. This is due to the mold release agent that is present throughout the entire SMC part. Unlike conventionally molded parts where release agents are applied to the mold surface, SMC is compounded with them in the resin mix for quicker processing. This means that as the damage is sanded to prepare a good bonding surface, fresh mold release agent is exposed. Polyester resin products are not strong enough to adhere to this surface. SMC SHOULD ONLY BE REPAIRED USING EPOXY-BASED RESINS, FILLERS AND ADHESIVES. When painting, use only catalyzed type paint systems. Once the extent of the damage and the type of material used is known, determine if the part should be repaired or replaced. If the manufacturer's specifications are available, check whether the damaged area is too large to be repaired. If no information can be reviewed, make a quick estimate of the materials and labor time needed for the repair and compare the figure to the price of a new part. A savings of at least 50 percent is the typical cut-off point to warrant proceeding with the repair.

    *** Most affordable product with the longest working time is a product called Marine Tex... It can be found on Ebay

    This is a link to a proper video of a repair, they use a two part epoxy that is the dual tube with mixing tip. http://m.youtube.com/watch?v=eGaF15W...%3DeGaF15W3mXA
    Last edited by 98nightmare; 08-22-2013 at 09:40 PM.


    ~Bill~



    Quote Originally Posted by dagen_1 View Post

    it's 18ft long and weighs almost 5,000 pounds. nothing miniature about it :/

  2. #2
    Warranty Killer! DRAGGIN95's Avatar
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    It is stuck. Great info!
    95 CC stepside with a 408 stroker LS motor from Texas Speed and built 4L80E
    96 CCSB daily
    93 2DR Blazer 2wd swap in progress
    90 Nissan low MPG truck
    00 CC Dually Tow Pig 53 Chevy 2dr car

  3. #3
    Bill 98nightmare's Avatar
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    Thanks bro!


    ~Bill~



    Quote Originally Posted by dagen_1 View Post

    it's 18ft long and weighs almost 5,000 pounds. nothing miniature about it :/

  4. #4
    REDNECK ROMEO SCOTTYINWV's Avatar
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    thanks a million and sweet truck man!
    SCOTTYINWV aka S3
    1989 K1500 355/RV CAM HM290 3:73's
    1989 K1500 SCOTTSDALE BUILD

  5. #5
    I'm all 8-Luggy! 88GMCtruck's Avatar
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    Great info.

    The stepside fenders on my 88 are de-laminating and cracking. I was lucky enough to pick up a pair of damn near perfect bedsides to replace them instead of repairing them.

    The driver's dually fender on my 98 has 2 cracks that I will likey repair unless i trip over a new fender somewhere.
    Dave --- "My Trucks either have three letters on the grille, or are dressed in formal attire."



    78 Nomad 19'; 5" lift/LED/Delco HU -Sold 8/14
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    98 "GMChevy" K3500; Crew Dually/454/NV4500
    02 GMC K1500; HT pkg/2" lowered/SS 20s
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  6. #6
    Bill 98nightmare's Avatar
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    Thanks guys! Wish id found this out a few years ago...lol


    ~Bill~



    Quote Originally Posted by dagen_1 View Post

    it's 18ft long and weighs almost 5,000 pounds. nothing miniature about it :/

  7. #7
    I'm Awesome michael hurd's Avatar
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    You can use epoxy to repair fiberglass, but not the other way around, and part of the reason is that polyester resin as it cures, it will shrink 3%. This action will weaken the bond, even if prepped with a coarse grit disc. Fusor T-21 is your friend when it comes to SMC repairs, and it works great on fiberglass as well, but it is pricey.

  8. #8
    OBS 4 Me dagen_1's Avatar
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    thanks for sharing bill... i don't own a step-side bed (yet) but might end up with one some day. good to know!

    DeWayne
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  9. #9
    All out OBS. 94Sierra4x4's Avatar
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    And if anyone is curious - that Marine Tex is fvcking tough .. I had a little crack in the hull of an 18' boat I had a couple years back.. Bilge pump was always having a working out.
    Hit the crack with Marine Tex - let er set - smoothed it out a bit - and never turned the bilge pump on again.
    -Cole
    94 ECRB - 5.0, NV3500 - Rolled - Blown up - Scrapped
    97 ECRB - 5.7, 4l60e, F44, 14B SF, 3.73s - Daily Driver

    My '94 - http://www.gmt400.com/forum/showthre...CRB-Sierra-4x4
    My '97 http://www.gmt400.com/forum/showthre...eradoZ71/page6


  10. #10
    GMT 1600 BHBurban's Avatar
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    Good info to have posted.

    I lost count how many times I've told people that stepside bedsides were SMC, not fiberglass...


    Quote Originally Posted by 88GMCtruck View Post
    The driver's dually fender on my 98 has 2 cracks that I will likey repair unless i trip over a new fender somewhere.
    If you trip over it, you'll crack it!


    Funny how he's repairing 400 dually fenders in the how to!
    Last edited by BHBurban; 08-26-2013 at 02:03 PM.

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