Attach Fiberglass 1/4panel to metal
I have been searching around the web trying to find out how to attach a fiberglass 1/4 panel to metal. Any advise would be great.
Metal 1/4 panels have not been qround for over 10 years and pretty much the ones in the junk yards are worse than mine. (Rust/Bondoed)
Last edited by Shreck; 01-26-2008 at 10:26 PM.
For fastening glass to metal we usually use Dyna-Weld flexible adhesive filler. You prep the bonding surfaces and glue them together. After the DW hardens you can grind the seam and apply more DW and a reinforcing mesh over the seam to fill it. When the seam is close to being right you can switch to Poly-Flex putty to tweak the seam then prime it with flexed primer then paint it with flexed paint. Everything needs to be flexible so that the fiberglass and the metal can expand and contract at different rates without cracking at the seam.
To hold the fiberglass panel in place while the DW hardens we usually use screws then fill the holes with short strand fiberglass paste. You don't want to screw the panel on too tightly or it will squeeze a lot of the DW out and the bond won't be as strong. Be sure to drill screw and test fit before applying adhesive. Press adhesive into the scratches of both prepped panels before you put them together.
Dyna Weld Link
In a cold climate this could this be a severe problem? I am confused about the ability to contract and expand at different rate because of the difference in material will eventualy crack. I dont know this product, could you explain how come it wont crack.
Originally Posted by Len
Sorry for so many questions. :confused:
When Dyna-Weld hardens it remains flexible. All the products that span from one surface to the other need to flex in order to compensate for the different expansion characteristics of the metal and glass. This means the DW, putty, primer, and paint all need to be flexible.
Originally Posted by Shreck
What kind of paint do I use that stays flexable? I guess this paint would be very expensive.
you can use just about any paint, you just need a flex additive. im sure your jobber or len can help you figure out what exactly you need
I would like to thank you guys for your help. But just one more question.
Would mounting a skin of fiberglass on metal be a big problem because of the difference in thickness in material. Do I have to push back the exsisting metal panel to allow for the overlaping of the fiberglass panel on top of the metal. Like creating a lip of 1" or so around the area to be attached to. Also if depth permitted would it be advisable to put in a few pop rivets just below the surface of the fiberglass and then fill over the rivets, or would that cause another problem. This of course would be used in conjunction with the products mentioned above.
One little thing. Anywhere fibreglass is going to contact metal, I would spray or brush with some zinc-oxide primer first. Zinc-oxides are made specifically for places where dissimilar materials will be joined. I'm not an expert, Lord/Fusor makes a couple products that I believe would work beautifully for your projects. My personal opinion would be to join the metal and fiberglass with a butt-joint with a fiberglass or hard-plastic backing-place behind and between them. Your quarter is pretty flat, so I'd say use a woven fiberglass cloth over top of the seam to even it out. You should be able to grind and sand the fiberglass down to where you may not need much/any filler. I did a project similar to this where I had to make the joint between a glass spoiler and deck lid seamless. I took the paint off of where the two would touch and brushed on some zinc-oxide primer, then I Fusor'd the spoiler to the deck, but I had to use fiberglass matte to get a nice sharp joint. It looked nice and the imperfections blocked out with primer. Hope this helped.
The thing to remember is that no matter what materials are used to attach fiberglass to metal these two materials will expand and contract at different rates. Below is a discription of the method that I use to attach a fiberglass hood scoop to a metal hood and I would use the same method on a quarter panel.
Take the scoop and place it in the desired position and draw its outline on the hood.
Cut the metal (for a functional scoop) so that you have a couple of inches under the edge of the scoop.
Drill some 1/8" holes in the scoop through to the hood about every inch and insert a screw to pull the scoop down. (Doing this type of mounting on other areas of the vehicle you may be able to clamp the panels together.)
After the holes are drilled and the screws are in place remove the screws and the scoop.
Grind the metal clean near the point of contact as well as the glass using a 16 or 24 grit disk.
Apply your bonding material (I've been using Dyna-Weld) To both surfaces pushing the material into the scratches then build up a little on the surface and put the two pieces together and screw it down. DON'T screw it down tight because the Dyna-Weld is your glue and if you squeeze it all out your scoop will pop right off. Just pull the scoop down enough so that the paste starts to push out of the crack a little.
After the material gets hard remove the screws and grind off the excess bonding material and do some initial shaping with the grinder.
Countersink the screw holes and cut a strip of fiberglass cloth about an inch wide to cover the seam all the way around the outside of the scoop.
Using more Dyna-Weld apply it to the edge filling the screw holes and giving you some buildup over the seam then push the fiberglass cloth into the soft paste so that it covers the seam and apply more DW on top while everything is still soft. You may need to do about a foot at a time because this could take long enough for the DW to start to harden. So cut the cloth strip into 1 foot lengths and do one at a time until you're all the way around and the cloth is buried in the DW and covering the seam.
Once the DW is hardened over the cloth use the appropriate sanding block to shape the filler. Apply more of the filler (you can now use flexible polyester putty) and continue the shaping but try not to sand so much off that you sand through the cloth reinforcing strip.
The idea here is to use a flexible material (Dyna-Weld and flexible putty) so that the different expanding/contracting characteristics of the materials don't cause cracking.
When you have your shape sanded to where you're happy with 80 grit paper then go over it with some 180 and then spray it with some 2K primer using a flex additive so that the primer is also flexible. After guide coating and sanding the primer with some 400/600 grits sandpaper you can apply paint but be sure that the paint ALSO has flex additive added so that it won't crack.