Strongest filler

[rustybronco]

Stud welder...

[John Park]

While possible I guess, I can't see any possible benefit in mixing micro balloons into polyester filler. Weight reduction? Better to straighten the metal and if it is such a beater you can't who cares about weight?

Flox? You have a source for carbon fiber cat hair filler or do you mix your own?

Microballoons keep the surface from glazing and make sanding a lot easier because the tooth of the grit can get in the surface instead of skidding. It's also cheaper per volume than resins. Like Flox which is cotton, polyester minifibers will also increase the strength and also act as a thickener, while micro balloons act like ball bearings to do the opposite.

It isn't about weight or strength but shrinkage and adhesion. Having extra strong filler that falls out is pointless. Polyester resins shrink [3%,?] while epoxy doesn't. I have yet to hear of polyester being used as a glue; epoxy, need I say? There is a special resin formulated to adhere to aluminum which is amazing. Stretch to failure of epoxy is about 10% whereas poly is about 3%.

It seems as though talking about epoxy resins in a polyester automotive bodywork world is hopeless. I did notice that the Flox link talked about using it with epoxy resins, but it is an aircraft site.

Sure, you have to learn some things to work with epoxies, but if you're averse to learning you probably won't last long on a bike.

[metalfab]

While possible I guess, I can't see any possible benefit in mixing micro balloons into polyester filler. Weight reduction? Better to straighten the metal and if it is such a beater you can't who cares about weight?

Flox? You have a source for carbon fiber cat hair filler or do you mix your own?

Carbon fiber cat hair?, never used any, the flox is cotton. Carbon fiber would probably be a waste as it is strong in tension, it really doesnt shine anywhere else.
Someone else covered it on the micro, straight resin is too thin, and very hard to work with sandpaper. The micro aids the working the sanding of the filler. The overall characteristics of the resin are improved by the micro. The flox is a strength thing. I got pulled over one time with a bag of micro, and the cop thought it was drugs, that was a bad few hours. Ironically a good friend of mine that is a fed was at my shop one day and opened a cabinet where I had flox, micro, and epoxy stored and he asked what the hell is this. I think cops are predisposed to alert to bags of white powder.

I think the strongest filler is lead it stays in but applying lead is pretty much a lost art, and it is heavy.