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08-22-2013, 09:30 PM #1
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
08-22-2013, 11:24 PM #2
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
08-22-2013, 11:28 PM #3
08-22-2013, 11:42 PM #4
thanks a million and sweet truck man!SCOTTYINWV aka S3
1989 K1500 355/RV CAM HM290 3:73's
1989 K1500 SCOTTSDALE BUILD
08-22-2013, 11:44 PM #5
- Join Date
- Apr 2010
- Auburn, Wa: From Covington, Wa: Albion, Wa: Pullman, Wa: Edgewood, Wa
- Rep Power
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
88 GMC K1500; 9" SAS/D44/14FF Detroit/NV4500/NP241/TBI454
95 Alpenlite Silverton 11'; Full LED
98 "GMChevy" K3500; Crew Dually/454/NV4500
02 GMC K1500; HT pkg/2" lowered/SS 20s
99 Chevy K2500; 6.5L/NV4500 - Sold 3/14 -158,784 miles
08-22-2013, 11:54 PM #6
08-26-2013, 12:08 PM #7
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.
08-26-2013, 12:16 PM #8
thanks for sharing bill... i don't own a step-side bed (yet) but might end up with one some day. good to know!
08-26-2013, 12:41 PM #9
- Join Date
- May 2012
- Vancouver Island, British Columbia.
- Rep Power
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
08-26-2013, 01:58 PM #10
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