Spar attach fittings, flox or microballons?

[southwind32]

Getting ready to install the spar attach fittings (doublers) and the strut attach fitting. The instructions say to use a little bit of micro balloons. Is flox ok to use in this case, that's what I've been using in other mixtures, I have that, but don't have any micro balloons.
Thanks
Brian

[efwd]

Should be micro balloons. It maintains dissimilar metal separation. You should have got a small jar of it in the kit. Mine is a white plastic jar.
Eddie

[southwind32]

Don't have any, so flox shouldn't be used? Where can I get micro balloons?

[bumsteer]

ACS,Wicks, Amazon, EBay, some hobby stores. Do a search and many sources should pop up with maybe something local. Just curious, sounds like you have used flox in other mixtures. Flox was called for in these correct and not microballoons?

Rick

[HighWing]

Brian,
I have often used Tap Plastics. The closest I see to you is in Stockton. I suspect, though,, you might find it in most stores selling fiberglass supplies.

[efwd]

As John McBean would certainly say. "we have that here at Kitfox".
It's a simple phone call.

[Mikerv9a]

Getting ready to install the spar attach fittings (doublers) and the strut attach fitting. The instructions say to use a little bit of micro balloons. Is flox ok to use in this case, that's what I've been using in other mixtures, I have that, but don't have any micro balloons.
Thanks
Brian

As a builder of a Long-EZ, I can tell you that microballoons is ONLY used for fill and joining pieces of foam together. It has no structural/tear strength and is subject to cracking . Flox is flocked cotton and is only used to create rigid structural joints. It cures as hard as solid epoxy. I don’t buy that flox is not “compatible” with dissimilar metals, it’s just epoxy that is saturated with the flox to keep it from flowing out of the space where it’s used.
If this is a structural bond you’re making, I would NOT use microballons.

[jrevens]

As a builder of a Long-EZ, I can tell you that microballoons is ONLY used for fill and joining pieces of foam together. It has no structural/tear strength and is subject to cracking . Flox is flocked cotton and is only used to create rigid structural joints. It cures as hard as solid epoxy. I don’t buy that flox is not “compatible” with dissimilar metals, it’s just epoxy that is saturated with the flox to keep it from flowing out of the space where it’s used.
If this is a structural bond you’re making, I would NOT use microballons.

Thanks for confirming what I wrote and thought, Mike. The fittings in question are attached with a lot of rivets, and the epoxy should add additional strength to the joint, so why not make the joint as strong as possible and not decrease the strength with micro, while still sealing the contact area between the dissimilar metals from air and moisture? My original comments were just voicing what have been my thoughts from the beginning of my Kitfox project. The original idea to use micro-balloons might have been advanced by someone with incorrect or incomplete knowledge of the structural issues involved. Obviously, history has shown those joints, assembled that way, have been safe and strong enough. I don't mean to insult or disparage anyone's intelligence, but IF there is a better way to do something, I think we all would like to know about it.

[Guy Buchanan]

Adding microballoons to epoxy weakens it. However, sometimes tiny glass beads are added to epoxy for bond line thickness control. If your perfect assembly squeezes out all the epoxy, you have no adhesive bond, and therefore no strength. The glass beads maintain a .005" thickness minimum bond thickness thereby enabling epoxy adhesion. If your epoxy is being used to simply keep out water and thereby inhibit corrosion then adding microballoons will lighten things a little and maybe help keep the epoxy in place by thickening it a little. Strength is irrelevant.

Regarding corrosion. Most anyone who has worked on ocean racing yachts can attest that aluminum hates stainless and will, over time, turn to powder under the affects of galvanic corrosion. However it's a fair amount of time and requires much more salt water than I hope most of our wings are seeing. Anyone buying an aircraft that's spent a major part of its life on floats on salt water would be well advised to boroscope the wings though, to make sure there's no evidence of corrosion.

[jrevens]

Adding microballoons to epoxy weakens it. However, sometimes tiny glass beads are added to epoxy for bond line thickness control. If your perfect assembly squeezes out all the epoxy, you have no adhesive bond, and therefore no strength. The glass beads maintain a .005" thickness minimum bond thickness thereby enabling epoxy adhesion. If your epoxy is being used to simply keep out water and thereby inhibit corrosion then adding microballoons will lighten things a little and maybe help keep the epoxy in place by thickening it a little. Strength is irrelevant...

Good comments, Guy. My parting thoughts are these... based on several things, including the tiny quantity of micro I got in my kit and the lack of any real accurate guidance as far as mixing ratio with the epoxy, I think that the probability is slim that anything really beneficial, including maintaining separation, weight reduction, or thickening the epoxy, is being accomplished in this instance, and therefore it may be a waste of time and possibly a strength reducing one at that. If the joint has been designed for adequate strength with rivets alone, then strength of the epoxy is irrelevant.