Hi.

 I would like to hear opinions of different l.w. epoxy fillers. I was looking at Brodak's website and found out that they have 3 sorts to offer, Aeropoxy Super Fill, Aeropoxy lite and SIG Epoxolite. Can anyone enlighten me about the differences between these products. Which do you recommend?
 I'm planning to make very small fillets and fill some pinholes and other imperfections in molded surfaces of my new plane.

 Regards, Lauri

Lauri,

Neither of the products mentioned are actually epoxy "filler".  "Filler" would be glass or phenolic microballons or the like........which would be added to the epoxy mix.

The products you mentioned are more properly called "filled" epoxy------meaning that a filler is already in the mix.

Of the products mentioned, Sig Epoxolite cures light, but hard as concrete.  I have used the Aeropoxy Lite to make fillets and it sands fairly easily.  I have not used the Superfil from Brodak; it "may" be the same product that is available from another vendor under a similiar product name.

I have used 30 min. epoxy as well as finishing resin with microballoons added to make fillets.  Works OK if you get the right amount of microballons in the mix. Be careful mixing the 30 min. epoxy in mixing cups.  Large volumes of 30 min. epoxy cures very fast.

Jim

Edit:  The product Mark mentioned is the "similiar product" I mentioned-----very good stuff.

I've used Epoxolite, Aerofill and Super-Fil. Although, as Mark says, it smells weird, it's my choice. It's difficult to mix thoroughly, so you have to keep stirring, but it cures fairly quickly and sands easily. Best source appears to be:

http://www.aircraftspruce.com/catalog/cmpages/superfil.php  - - or

http://www.wicksaircraft.com/catalog/product_cat.php/subid=8473/index.html

 Why do you use so fast curing epoxies with micro balloons? I never use faster than Std Araldite which has pot life about an hour. And in general, laminating resins are a lot better to mix with, they dry harder. It's not the hardness that makes the stuff to be difficult to sand but elasticity. Epoxy glues are allmost never completely hard.
 Another thing with mixing with fast-curing epoxies: You have to mix the putty quite fast and there is a risk of breaking the microballoon bubbles. That makes the putty a lot harder. Plus that you can mix more of balloons in the epoxy when you have more time to work. L

 Why do you use so fast curing epoxies with micro balloons?

   Not that i would necessarily recommend it, but when we were rebuilding my airplane right before the 1994 NATs (and I mean, *right before*) we used 5-minute and micro-balloons. When it was about 110 degrees. You'd get about 3 swipes with your finger before it started sticking.

     Brett

I suppose "right before" is the key word. Building new is not same as repairing L

   I don't recommend it.

    The wing folded on a Wednesday at about 2:00 pm, and we were leaving for the NATs Friday morning. The wing was gone, the stab was broken off, and the fuselage was ground down. We had a new wing in the airplane, the tail repaired, and the fuselage repaired by about 3 in the morning. We had the wing covered and the fillets on, and the base and two trim colors on it by about 3 the next day. We put it in the car about 11 in the morning on Friday, and took off for Lubbock. I put the trim colors on the wing in a motel in Albuquerque, and the lettering. I painted the canopy on with a brush in the parking lot at appearance judging, which was OK because it was about 110 degrees and about 3% humidity. Airplane flew fine, test flew it in a 20 mph wind, ended up 15th, tied with Mike Pratt (who also crashed his airplane, at the NATs).

    Other time-savers - the fiberglass over the wing center-section was applied with thin CA, which just about overcame us with fumes. it's still holding last I flew it. We heated the paint (K&B and Hobbypoxy) to get it to zap off as fast as possible to enable 3 colors to be applied in one day, although it was plenty hot enough in David's garage. Like I said, not recommended but it did the job and the airplane was still good enough to come in a close second in the Northwest regionals in 2006.

    Brett

>>It stics better if you moisten the surfaces with resin only before applying the fillet.<<

I didn't have any problem with the fillet sticking. My problems (very minor) were with paint sticking to the fillet. Getting bubbles on the fillets was a sometimes problem. Not a big deal if the fillets were cleaned really well with solvent prior to painting. No such problems with SuperFil. Weirdly, even when I have forgotten to clean the fillets well prior to paint, I've had zero problems with adhesion of paint with this stuff. It's just become a non-issue.