What is the best filler to use when building? Some of the stuff takes forever to set and stays gummy to the point of being almost impossible to sand. And what are the drawbacks of using some of the new auto body fillers that have micro balloons in them just like we've been using in models for years? Any and all opinions welcome.
Max

I use light spackling compound. It is a latex product, It drys fast if laid on in thin coats (1/8" or less) It weighs virtually nothing. It is super fast sanding. I build it up to shape sand to a finish and polyurethene coat it. The poly makes a tougher surface. The only drawback I found is that if you overheat it when covering, it will melt.

I simply use the balsa colored filler that you find at your LHS. It took me 4 years to empty this last container. I try hard to make all my joints fit right and therefore I do not use much.

I use Elmer's Wood Filler (for Light Woods) available at Walmart, or most hardware stores. Works great, easy to sane, easy cleanup.

The filler to avoid is Sig "Epoxolite."

It takes a full day to harden, and when it has set it requires a high speed grinder to shape it.

But it works fine in place of tri-stock for reinforcing the firewall and landing gear blocks.

Bill.

Here is an example of how I try to fit parts.....What you are looking at is the veticle fin from a CAREN AIRCRAFT KIT. The piece that fits around the base is a sheeted foam core that you have to cut a hole in that not only do you have to try to fit the AIRFOIL, but also the TAPER from top to bottom....VERY COMPLEX PIECE TO FIT, but as you see it is a very close fit which means I will have all the strength possible from this joint and will only need a TINY amount of filler.

I spent about a half a day on this piece alone

Thank you all for your input. I believe the pervading message here is that there are other products out there, not necessarily produced for balsa models, that work well. Looks like a trip to our brand new Wal Mart Super Center (which I HATE) is in order. And William Robison, you must have been reading my mind (very difficult when it is as minuscule as mine). Sig "Epoxolite" is the exact product I am struggling with. Think I will trash the remainder of the stuff rather that fight with it further. And your message was a "model" of elucidation rather than obfuscation. Quite rational also. CAPtain232, I am striving to get to the point you are now. I suspect your models are a work of art. I thank MikeSell and MinnFlyer also. I believe I like MinnFlyer's idea the best but perhaps the spackling compound without the poly might work well. It needs to be something that Monokote or Ultracote or whatever will adhere to well. Anyway..................
Max

JP:

Save your Epoxolite, as I said it's great for internal reinforcement.

Just as a side note, small minds have small thoughts - easy to read. Haw!

No one who is truly small minded has enough mental capacity to grasp the idea of flying models.

Bill.

The stuff that Elmer's makes will take covering very well. Those "Superlite" spackling or filler compounds I have found will shrink or mely under the heat of a covering iron.

PS Jeff, you do beautiful work!

Thank you sir, I do appreciate the kindness!

Jeff:

I vote with Minn.

Bill.

I use sheet rock joint compound. It dries nicely and sands extremely well. I had a tub left after some work around the house and gave it a try. It's cheap and works as well as anything else on the market.

John

Use the same thing you build with !!!! Balsa!!!!!!!!! CA and press on balsa with wedge in slot and sand!

Does monokote stick well to the joint compound or spackling material?

Even if used over a fairly large area? Like where the two wing halves meet and always have that nasty fiberglass and epoxy joint?

I have been struggling with HobbyLite filler. It doesn't seem to go on very easy. And it is a bear to sand off.

Fever

Spackling works well as long as you don't overheat it. Thin coats do much better than thick material in fillets. If you make a fillet with spackling, thin some epoxy and give it a couple of coats before covering. If you are painting don't worry about it. It takes paint well.

I use red devil spackle, super light, super easy to sand and when I cover, I cover the joint over the spacle with a pice of covering glued on with thick instant instead of heat, then run the covering down onto that piece from both sides and I have no joint. If on a fuse, you can still glue the monokote to the spackle, and then cover to it or carefully attatch the fuse covering over it so there is no seam. It works really well.

Might have to try Minns idea if it takes covering better. That would be nice in some instances.