quick question… fixing fibreglass to metal? without it cracking?
im talking about affixing fibreglass panels (gaurds) onto the rear of a car…
the way we do it and have been told to do it is using black sikaflex and then bogging or using a fibrebog to smooth it into the car…
however we have had a few problems with it (after being filled, smoothed in and painted…) and a few cracks apearing here and there…
is there anything we can do to avoid this?
after trying every method known to man un succesfully id say no! though there are many people buying hood scoops from me that say it works fine for them i ask them to show me one (that is driven daily) after 1 year no body ever comes back :roll: unless thay are there to buy the whole hood
At auto body supply shops they sell an epoxy resin paste that you apply to the metal before adding the fiberglass part and it will allow for the different expansion rates between steel and fiberglass…at lest back maybe 25 to 35 years ago when I last did custom body work…
The only method I have found that actually works, is to glue the part on with sikaflex or equivelant, let it totally cure then go back, grind the edges down with 36 grit. Lay on a 2" wide strip of 1.5 oz mat, saturate and let cure. grind with 36 grit, lay down 2 layers 4" wide 1.5oz mat allow to cure 2 days and finish part. I have had open hood scoops last at least 5 years this way. It is also inportant to finish the inside of the part to keep water from getting under the edges and starting rust.
There is a stuff for it. I read somewhere about this. I’ll try to look for it and post it here.
Thanks…
So this epoxy resin… used so smoothing it in or just bonding it? How does it really work?
bricklin - if i am fibreglassing it to the car, wouldnt it crack when the chassis twisted?
If want to “fix” fiberglas or CF to a body and not have it crack ther better not be much flex or nothing will keep it crack free short of springs and bolts. If there is a small amount of flex and you dont mind the seam showing you can just bond it on with either sikaflex or windshield urethane. That is how we bond the composite door skins to the metal shells on our bricklins, the doors have lots of flex so a flexible adhesive is needed.
so if you have a small seam for it to flex in filled with a flexable sealer is that what you are saying? it makes sense to me just like cutting lines in a side walk cool idea
In prior jobs, I used to work with General Motors in prototyping the corvette body panels and the Camarao/Firebird panels . We produced a fiberglass panel similar in properties to the SMC panels that are used in production. We bonded them with Ashland Pligrip.
http://www.ashchem.com/ascc/specialty/pliogrip.asp
That’s not the stuff gramma uses for her teeth. it is a semi flexible adhesive and it is currently used by many OEM’s and tier ones for bonding fiberlass SMC panels to a steel frame.
Yes, Doug is on to the best method I’ve ever found to be lasting too !
The componets I’ve had luck with are called Duramix 2 part epoxy. It can be picked up at professional paint supplies stores.They actually teach you to use it as the binder layer and the finish/bodywork skim coat ! The metal around it will tear in an accident before it will let go too !
Amazing stuff for sure.The same sensible metal prep goes into it of course, 36/40 grit sanding,no preprime, screw your part down into the epoxy…let it kick remove the screws and use a dab more epoxy to fill the holes…then treat as you would any panel to get it to primer/paint.
Vince… 8)
i did a search on Pligrip but it doesnt seem to be available over here in australia…
bricklin we do worry about the seam, because it has to be a smooth finish else the seam will show up when the car goes for paint…
Maybe this Duramix 2 part epoxy seems the way to go, if it is used to join the peice to the car AND as the finisher i would imagine you could sandwich the peice in between layers of it ( so to speak) and maybe that would avoid the cracking…
Do you have any more information on this product?
All the composite forums seem to be based overseas so its sometimes hard to find suppliers when products and shops are recomended… 
I would imagine all markets offer some form of this epoxy for body work panel adhesives since its so commonly used in manufacturing. So check a search online for adhesives/composite panel construction/ etc…
Duramix is based in Oxnard California. I believe the adhesives are actually Urethane based and come in a variety of cure times. I use the 4700 series of two part in a official gun that shoots both parts at the same instant…sort of a double caulking gun, if you will.
…Vinny 8)
Damn i must be getting old…I meant pliogrip…I try to get finished here too quickly and it shows sometimes.
Come on Doug, you just were thinking of “POLYGRIP” lol!!
This getting old can be a bummer,huh ?
Vinny 8)
Oh Yeah,
bite me…with or without yur dentures!
(toothless grin)
Hahhaha !Very good one ! lol. In my neck of the woods ,no teeth in a hooker , you would ask for a gummer ! Doh ! lol.
:lol:
Oooooh, thats just wrong…
Vinny 8)