Rusty bits: fiberglass or skin?

Area for General FSJ related chat.
Post Reply
User avatar

Topic author
PlasticMastodon
Posts: 27
Joined: Mon Mar 25, 2019 8:49 am
Location: Memphis, TN

Rusty bits: fiberglass or skin?

Post by PlasticMastodon »

Really not surprised that there is quite a bit of rust on the bottom of the rear quarter panels. The question I have is whether I should use fiberglass or buy some skins to replace.

Looks like it is relatively easy to pick up rear quarter panel skins. That is appealing because it would give me clean straight lines to start with. I can get all the gear and even have a welding buddy help me out. The question is: Has anyone done this that can give advice? And is it worth it versus getting some fiberglass to repair the bad spots?

Thanks!
User avatar

dodgerammit
Posts: 1434
Joined: Wed Jan 11, 2017 11:20 pm
Location: Middle TN

Re: Rusty bits: fiberglass or skin?

Post by dodgerammit »

Skin. Fiberglass will cause a reaction in the metal leading to further rust issues. Even good metal will rust when exposed to the fiberglass resin.
84 Grand Waggy-Radio Flyer (Garnet Red/3M Ebony Metallic woodgrain, with honey interior) AMC 360 :cry: 2004 4.8LS/Advance Adapter/727/242 D44/AMC20 Serehill tailgate and headlight harnesses :fsj: Ongoing thread-viewtopic.php?t=11897

92 Wrangler Islander 4.0/32RH/231 D30/D35 RHD
User avatar

Topic author
PlasticMastodon
Posts: 27
Joined: Mon Mar 25, 2019 8:49 am
Location: Memphis, TN

Re: Rusty bits: fiberglass or skin?

Post by PlasticMastodon »

Skin it is. Thanks.

SJTD
Posts: 1924
Joined: Tue May 21, 2013 12:02 pm
Location: Lompoc, Sunland or somewhere between

Re: Rusty bits: fiberglass or skin?

Post by SJTD »

Howcome fiberglass, presumably set with polyester resin, will cause rust but Bondo and other body fillers, polyester resin with various fillers to thicken them, will not?
Sic friatur crustulum

'84 GW with Nissan SD33T, early Chev NV4500, 300, narrowed Ford reverse 44, narrowed Ford 60, SOA/reversed shackle in fornt, lowered mount/flipped shackle in rear.

letank
Posts: 4010
Joined: Wed Oct 03, 2012 9:16 pm
Location: SF bay area

Re: Rusty bits: fiberglass or skin?

Post by letank »

dodgerammit wrote:Skin. Fiberglass will cause a reaction in the metal leading to further rust issues. Even good metal will rust when exposed to the fiberglass resin.
X2, when I plugged some large patches on the roof, because of the enlarged roof rack slider screw holes... I sanded all the rust, and it took about 2 years for the rust to be a lot larger... the fiberglass mat was lifterd without any effort.

Image

Marine epoxy took care of that emergency repair
Michel
74 wag (349 Kmiles... parked, next step is a rust free body)
85 Gwag (229 Kmiles... the running test lab)
User avatar

tgreese
Posts: 7118
Joined: Fri Jun 08, 2012 6:31 am
Location: Medford MA USA

Re: Rusty bits: fiberglass or skin?

Post by tgreese »

Bondo has to be sealed to not rust. Exposed bondo on bare steel will rust between the bondo and steel.
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination A/Ts, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
Dual Everything: '15 Chryco Jeep Cherokee KL Trailhawk, ECO Green
Blockchain the vote.

SJTD
Posts: 1924
Joined: Tue May 21, 2013 12:02 pm
Location: Lompoc, Sunland or somewhere between

Re: Rusty bits: fiberglass or skin?

Post by SJTD »

True, and so does a fiberglass/polyester resin repair.

My point is that the resin used to lay the fiberglass is the same as what's in most body fillers so it won't "cause" rust. Obviously such a repair needs paint inside and out, just like a weld repair.
Sic friatur crustulum

'84 GW with Nissan SD33T, early Chev NV4500, 300, narrowed Ford reverse 44, narrowed Ford 60, SOA/reversed shackle in fornt, lowered mount/flipped shackle in rear.
User avatar

dodgerammit
Posts: 1434
Joined: Wed Jan 11, 2017 11:20 pm
Location: Middle TN

Re: Rusty bits: fiberglass or skin?

Post by dodgerammit »

SJTD wrote:True, and so does a fiberglass/polyester resin repair.

My point is that the resin used to lay the fiberglass is the same as what's in most body fillers so it won't "cause" rust. Obviously such a repair needs paint inside and out, just like a weld repair.
Painted mine in and out. Rusted. The body filler didn't. I'm not the only one.
84 Grand Waggy-Radio Flyer (Garnet Red/3M Ebony Metallic woodgrain, with honey interior) AMC 360 :cry: 2004 4.8LS/Advance Adapter/727/242 D44/AMC20 Serehill tailgate and headlight harnesses :fsj: Ongoing thread-viewtopic.php?t=11897

92 Wrangler Islander 4.0/32RH/231 D30/D35 RHD
User avatar

tgreese
Posts: 7118
Joined: Fri Jun 08, 2012 6:31 am
Location: Medford MA USA

Re: Rusty bits: fiberglass or skin?

Post by tgreese »

I understood that the filler in bondo - talc - was more problematic than the resin. There are body fillers made with resin and fiberglass, such as ASC Duraglas and Evercoat Kittyhair that are marketed as waterproof and rustproof, and often used for rust repair. Likely the resin formula is different from fiberglass resin, and made for direct contact with steel. I've used Duraglas with good success - no rust so far.

My take - regardless of the materials, existing rust will progress if it's not stabilized _and_ encapsulated from both moisture and oxygen. Any repair is temporary given enough time and the proper conditions, but how temporary depends on the materials and methods used. Steel replacement is considered the longest lasting repair.
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination A/Ts, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
Dual Everything: '15 Chryco Jeep Cherokee KL Trailhawk, ECO Green
Blockchain the vote.

rocklaurence
Vendor
Posts: 2565
Joined: Sat Mar 30, 2013 6:53 am

Re: Rusty bits: fiberglass or skin?

Post by rocklaurence »

Truth is that Fiber Glass, Bondo, fillers etc were designed for perminent repairs on metal without rusting. If its failing, its because of poor prep'/application.
User avatar

dodgerammit
Posts: 1434
Joined: Wed Jan 11, 2017 11:20 pm
Location: Middle TN

Re: Rusty bits: fiberglass or skin?

Post by dodgerammit »

Fiberglass has a different expansion rate than metal, and will fail much quicker than other fillers. Metal to metal is the best way. Cut out all rust. fix it right if the option is there.
84 Grand Waggy-Radio Flyer (Garnet Red/3M Ebony Metallic woodgrain, with honey interior) AMC 360 :cry: 2004 4.8LS/Advance Adapter/727/242 D44/AMC20 Serehill tailgate and headlight harnesses :fsj: Ongoing thread-viewtopic.php?t=11897

92 Wrangler Islander 4.0/32RH/231 D30/D35 RHD
Post Reply