Best FILLER material after repair of fiberglass bumpers

[xboxhaxorz]

I have repaired the insides of a full fiberglass bumper
I now need to fill in the the outside and have learned that bondo filler is not the best to use on a fiberglass bumper
Also i became aware that using fiberglass as a filler is extremely difficult to sand to the shape

[HotRod47]

Look for West Systems and their six-10 epoxy based filler. I use it on all fiberglass repairs. Because of its epoxy base nature it will never sink or settle after curing. It is full cure in 24 hours, and you can sand and shape it. It is a marine product for boats mostly, but it really works well in our industry as well.

http://www.westsystem.com/ss/new-six10-epoxy-adhesive/

[xboxhaxorz]

Thanks i will take a look at that, it kind of makes sense as well to me to use epoxy over bondo fillers

I was shocked when it was such a small amount of filler for the price compared to bondo but then realized its just a filler and not the product for the repair as i had used tons of the fiberglass resin and mat to do that

[jlcustomz]

Bondo BRAND filler is good for ;;;;eh , repairing rotten wood maybe.

After you've got the most of your shape done in the repair, scuff any low spot that needs it & a good traditional filler , such as by evercoat products can be used on top for the final smoothing. I use rage extreme as my general purpose & metal glaze for the smoothest light final results when needed. I have also sprayed g-2 primer surfacer over fiberglass work for the final smoothing. It's a sprayable body filler, non shrinking, but can actually add a little strength to the top of a repair. Need a 2'2 gun tip or larger to spray. Very strong smelling. Sprays textured & sands smooth, so it acts as it's own guidecoat.
As Glenn mentioned to you before, more than 1 method to do things.

[sccacuda]

I only use the marine fillers expressly made for fiberglass. This stuff is pretty damn amazing. Super light and flexible, crazy high build (can be wiped up to 1/2 thick) and is available in spray form or mix. The only down side is cure time. Has an open window time of 4 hours and 12 hour cure. Can't wipe a boat hull in 10 minutes! Here's a pic of what we use:
https://static1.pt-content.com/images/pt/2015/10/IMG_0051_zpsmm1ym2qd-1.jpg (http://s1060.photobucket.com/user/340cuda/media/IMG_0051_zpsmm1ym2qd.jpg.html)
https://static1.pt-content.com/images/pt/2015/10/IMG_0052_zpsihoxrsib-1.jpg (http://s1060.photobucket.com/user/340cuda/media/IMG_0052_zpsihoxrsib.jpg.html)
https://static1.pt-content.com/images/pt/2015/10/IMG_0053_zpsxacnkyry-1.jpg (http://s1060.photobucket.com/user/340cuda/media/IMG_0053_zpsxacnkyry.jpg.html)

[xboxhaxorz]

This is helpful, i may try the different methods on different pieces that i am repairing to find out which works best for me

For bumpers that have cracked, which is the best way to hold them together and aligned to apply the resin and mat, some areas i simply cannot get clamps in or the clamps will be in the way of the repair

[jlcustomz]

For cracks, this is old school repair procedure. Bevel grind half way one side at the crack, secure the other side, Gorilla duct tape is pretty good, fill that side with fabric & resin. Let dry & then grind & fill the other side. Back side can be left thicker.

Poly resin & stranded matt is the easiest method, but epoxy, as mentioned is a better bond & non shrinking. Just can't use stranded matt with epoxy because the binders holding the strand together won't bond to epoxy. Mist use woven material.

Look up some more basic info on fiberglass repair. The main procedures are still pretty old school, but better resins & fabrics are available now old info may not talk about ( higher performance).

[xboxhaxorz]

The areas im working on are where it kind of bends but i will try the duct tape i was thinking of using a heavy staple gun

Prior to posting this reply i had drilled 2 holes and used a very thin piece of sheet metal with rivets to hold it into place and after the resin had dried i drilled out the rivets

Another method was i clamped parts of the bumper and repaired the other area and after it dried i repaired the area that had the clamps, this works but is obviously quite time consuming

[xboxhaxorz]

So finally got to work on the vehicle, and my local marine store has been supplying me with stuff. I have taken care of all the cracks and holes etc; and have been laying the filler. Decided to go with the WS products since i want this to be a high quality project and local reps said i can basically make my own six10 or similar by mixing materials. Got the 105 resin, 206 hardener and 404 high density filler.

For sanding many sites recommend 80, 180 and 320 grit and others also mention to use 240 as well and i use this as a reference http://www.automotivetouchup.com/sandpaperselection.aspx.

I am looking into a primer and am unsure as to the best primer for fiberglass and or metal. Post 4 and other sites talk about the g2 but it seems its a primer and a filler and since i have already used filler im not sure if that is the right product. Then there is talk about primer sealer. My understanding is primer is used to fill any imperfections that a filler may not take care of and to prep the surface to allow the paint to adhere better.

I plan on using plastidip on this project. Not sure if that affects the primer type or not.