BasinBum

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I have used micro ballons for a while now to make fillets or in areas that I don't want the epoxy to drip. I recently started using chopped glass in the epoxy and it is reputed to make the epoxy stronger. If it makes the epoxy stronger why not use it all the time? Is there a down side to using chopped glass or an application where you would not want to?

J_R

If you mix the microballons to the costistancy of tooth paste, it is lighter than the glass mixture. The glass does have more strength.

bentgear

It can also make the epoxy mixture kick off a little quicker. I like it for putting firewalls in and wing halves together. Does it make a stornger joint, who knows, in my own mind it does.........

Ed M.

CurtD

My Feedback: (1)

Two reasons you might not want to use chopped glass instead of microballoons: 1) It's considerably heavier. 2) It's very difficult to sand.

I only use chopped glass as a filler or additive where I want it to reinforce something such as a firewall to fuselage side joint. 30-min epoxy filled with chopped glass (1/32" fibers) is amazingly strong stuff after it cures. Just don't put it anywhere you're gonna have to sand later.

dr_wogz

My Feedback: (3)

I got a bag of 'milled fiber' with one kit. used most of is as requested in the manual, mixing epoxy, and this 'milled fiber'. Great goopy messy stuff, and yes, stong!! you're adding fibers to it, so you know it's not just the hardened epoxy doing the work. Still have some left, and use it when teh joint is right!

Weren't micro ballons supposed to be hollow, and the idea was to create a honney bcomb of spomge effect? to lighten the joint?

DMyer

My Feedback: (2)

Slow cure epoxy resin and chopped fibers... either fiberglass or carbon... is for structural strength needs only in out of sight places. Resin and ballons are for beauty... filling... fillits... wing saddles etc. They are usually mixed to a very high ratio of resin/ballons to keep it light and sandable.


Dan

CafeenMan

I've mixed chopped glass and microballoons together at the same time to strengthen epoxy/micro-balloon wing fillets. Works pretty well. But chopped glass is used for strength and micro-balloons are used for lightness and filling. They do different things so they aren't interchangeable.

BasinBum

My Feedback: (2)

CurtD answered the question, thanks. Weight and sanding makes sense. I think I'll start using them a lot more on structural joints since I think the weight issue is probably worth the tradeoff on things like firewalls and wing hold downs.

TerrellFlyer

Hi BasinBum,if the joint has a good fit then the filler isn't needed,wood to wood with out a filler is the best joint.

DMyer

My Feedback: (2)

Terrellflyer wrote:

"Hi BasinBum,if the joint has a good fit then the filler isn't needed,wood to wood with out a filler is the best joint."

I think most people use chopped glass/CF resin mix as a substitute for triangle stock under wing holddowns, firewalls or other high stress areas as needed for the purpose of increasing strength instead of filling gaps in joints.

Dan