Microballoons

[KevinL]

Getting ready to bond in the skylight angle to the upper rear carry through tube on the fuselage. The book says to mix the adhesive with microballoons. I've used microballon powder with resin for composite but not sure why it would be used with the adhesive. Also do not know what ratio to use. Could someone educate me please?

[efwd]

I understand the microballoons to be for nothing more than keeping the two dissimilar metals from contacting one another. You only need very little. Just enough that, in your minds eye, there will be a layer of balloons across the surface so that contact of the two parts is not achievable.

[jrevens]

I agree with Eddie. They're also used as filler to make a light-weight, easy to sand mixture with epoxy or other resins. The fact is that they weaken the strength of a bonded joint. FWIW, I can see no reason to use them for bonding that piece to the fuselage tube because the tube is powder-coated and there is no direct contact between the dissimilar metals.

[n85ae]

Probably the microballons are simply to act as a thickener so the adhesive doesn't run. It's
not a very highly stressed bond I wouldn't think.

Jeff

[jrevens]

If you add enough microballoons to epoxy you can make something similar to Super-Fil. Light and sands very nicely. Flox-filled epoxy, not so nice to sand!

[napierm]

I used it to make the tips of my Rudder/VS (speedster) and Elevator/HS look nicer, blended with the ribs. As you said, mix micro with Hysol. Kept adding balloons until it was more like a fluffy paste. Is pretty tough and weighs very little.

I agree with Eddie. They're also used as filler to make a light-weight, easy to sand mixture with epoxy or other resins. The fact is that they weaken the strength of a bonded joint. FWIW, I can see no reason to use them for bonding that piece to the fuselage tube because the tube is powder-coated and there is no direct contact between the dissimilar metals.

[efwd]

If you are trying to thicken, it's Flox that Kitfox will call for. Having said that, people use balloons to thicken and make workable as John stated.

[taff]

Another good additive for the epoxy resin is West System, Fairing Filler.
They (West System) suggest it for their own epoxy resin. Used to only fill areas. And real nice sanding qualifies.
It's not micro balloons but a very fine powder.

I also used it as an addition to T88 adhesive. T88 is probably the best epoxy adhesive there is for gluing wood together.

[Maverick]

My recollection from building a fiberglass plane is that the micro-balloons are good for thickening the slurry for filling voids and making bonds that were not stressed while cotton flox was called for when it was a bond that needed to be strong. I used flox on that bond only because the slurry with micro-balloons tended to flow and run away from the two surfaces. With flox it was more pasty and didn't run away from the two surfaces but either would work on that joint. And, just in case there is a difference between the glue types, I was using 3-M rather than Hysol.

[KevinL]

Thanks much for the replies. Pretty much confirms what I remember from working with composite. The microballoons would thicken the resin which was maple syrup consistency prior to adding. I'm using the Hysol 2-part adhesive which should be thick enough for this application I think.