Using microballons

What the heck do I mix these things with to make some balsa filler?

White glue? Sigment?

I just need to do some light fill work and sanding. No fillets at this point.

Never used these suckers before.

I have used them in thinned Pica Glu it, and Ambroid for what you are talking about. I also use balsa dust in Ambroid, mixed into a paste.
Bill <><

I thought Ron B answered this quite well in the last thread where you asked.

His recommendations and techniques are based upon many years of expert modelling.

I'm still not certain.

Maybe I should just grap some "Model Magic" for what I need to do right now...

Actually, glass microspheres are inert. You can mix them with anything. But they seem to work best in our use with epoxy.

THey aren't the best solution for fillets or filling though. Search for the threads on WEST epoxy and 410 microlight fillers.

Aircraft Spruce sells a filler product that is really good also-aeropoxy or some such name.

For small dents I often use ambroid or similar cement mixed with baby talc.

LAST EDITED ON May-17-04 AT 11:38 AM (CDT)
 
>What the heck do I mix these things with to make some balsa
>filler?
>
>White glue? Sigment?
>
>I just need to do some light fill work and sanding. No
>fillets at this point.
>
>Never used these suckers before.

Ron B.
F4Fguy

I'm sorry,I misunderstood your request and addressed fillets instead of fillers.
I would not use microballoons for this application.A much more effective technique is Silkspan,applied with either dope or PC.Follow with more PC or talc and dope to fill any other MINOR discrepancies,then auto or Brodaks primer.whatever you use SAND most of it off.The idea is to fill the grain,not cover it up.Microballoons are far too large to do a good job of getting down into the grain.The PC method(Check elsewhere In SSF)will give the hardest surface for the lowest weight.Unless you're committed to a non-solvent finish,stay away from "Model Tragic".It does work easily ,but it stops about there.It's not resistant to laquers;cellulose,butyrate,or acetate.It feathers nicely,but when hit with any of these laquers, the "feathering" dissolves and leaves a hard edge.It also has a coarser finish than I like.
If dent filling is the problem,there's only one solution in my experience.3M Green Acryl Spot Putty.It goes on easily,dries fast(10-15 min.)and sands to the finest feather you could ask for.Then you can paint over it with anything.

Let me try to better explain exactly what I am up to.

I have the wing built and ready for initial sanding. I'm looking to fill gaps between sheeting, leading/trailing edge and caps, etc. Nothing major in terms of gaps. 1/32 max I would guess.

But as said, maybe I don't have to worry about it too much and just cover and fill then.

Sorry guys, been a LONG time since I built and I didn't build many even before, so I'm still a new builder by any common standard.

use hardware store light spachtling compound(Red Devil, Dap, etc). You can harden it up slightly by thinning it with a small amount of polycrylic varnish.

You can also fill wider cracks with thin slivers of balsa. Press 'em in and put on a bit of polycrylic thinned with alcohol. Balsa is lighter than most any other filler!.

I generally use regular drywall spackle for filling cracks. I find the lightweight stuff shrinks and is to soft. Drywall spackle is heavy, but I use such a small amount the weight is not an issue.

For those small cracks you can sand lightly and put a few drops of cyano before blowing off the sanding dust and repeat as necessary.

Hi!
One of the best uses for microbaloons and epoxy is as an 'inner fillet' at fuse/wing joints and around the corners of the motor crutch/fuselage side joint. I have found that it works as well as using scrap balsa and is stronger. Weight shouldnt be a problem because the Epoxie/microbaloon slurry is almost all microbaloons anyway. Just remember that it dosn't take much to do a good job so mix up a batch and make sure that you throw most of it away.

I have also used it around the inner corners of profile engine cavities where it fills the corners and makes maintenence/cleaning much easier. Remember though, finish adhesion can be a problem unless you sand the epoxie before painting. These days I prefer to fill those corners with a bit of triangular stock and sand that into a fillet. Done right, a profile fuse is a big a hassel as a built-up one and the built up ones give a better motor run anyway.

For dings, model magic will work if you harden it with a shot of CA after sanding and then hit it with fine (320) sandpaper. It works for me anyway!

Green auto body filler is great once the balsa is doped and is my ding filler of choice on silk Spaned surfaces. The green stuff dries very quickly and sands like a dream. One tube will last YEARS if you use it right!

Sanding a gap and shooting the dust with CA is ok. I've done it myself on many occasions but it might be better to pay more attention to your sheeting process and avoid those gaps through better craftsmanship.

A 1/32" gap is pretty big, so try this: Take a piece of scrap 1/16" balsa sheeting about as long as or a bit longer than the crack and sand one edge to a taper. Fiddle with it untill it will just slide into your gap and then CA it into place. Then carefilly sand the the joint to match the rest of the sheeting. You may find it helpful to trim the fill off near flush and then harden the surrounding area with CA before sanding. With care, your repair can be made undetectable.

Many of the dings that I once needed to fill were elinimated when I began treating the unassembled pieces of my models better. Repairing a nicely made stab can take almost as much time and effort as crafting a new part!

These days, I take a finished component and masking tape it down inside of a cardboard box and put the box on a shelf, far out of harms way.

Prehaps these suggestions will help.

Bigs

" What constitutes the dignity of a craft is that it creates a fellowship, that it binds men together and fashions for them a common language. For there is but one problem - the problem of human relations."

On fillets. So I paid lots of $$ for some "great" epoxy called AERO EPOXY. I was convinced it could be sanded. But no, mon amiee! The stuff is no better than SIG EPOXOLITE. What this world really needs is a fillet material that can be sanded! Even when mixed with microballons, it hardens like cement (concrete, that is) and defies any sandpaper known to man or beast.

Hi!

IMHO aeropoxy works just fine! The trick, as with the other, heavier filleting materials like Epoxolite, is to get the fillets right BEFORE THEY CURE.

Before you begin the filleting job make yourself a filleting tool. It can be hard balsa, plywood on a stick, plastic or metal. I once even saw an idea using a ball bearing brazed to a rod.

Anyway, mix up whatever potion you prefer and get it ready to apply. That means mixing it for at leaste TWICE as long as the instructions say!! Also, make sure that you mix more than you think you'll need. You really do not want to interrupt your filleting because you skrimped on the mix!

Then, use your tool to form your fillets. Once you have them just perfect, wet a finger with alcohol and go over them lightly to 'slick' them down. If you've screwed things up, at this point you can easily scrape out the fillets and start over. Take your time and get it right.

If you like what you see, check the filleting carefully several times to make sure that EVERYTHING is JUST RIGHT before you put the plane aside for the night.

Once the fillets have cured (Overnight.) hit them with a little 320 wrapped around a stick to clean them up and give them a little tooth. Finally, paint them with dope or whatever youre using as a fuel proof finishing agent.

If you arn't having good results try practicing on some semi-finished scrap before moving on to your toy airplane. Believe me, I did some crappy filleting jobs as I was learning and nothing looks better done right and nothing looks worse if done wrong. Plus, you'll be looking at the plane for as long as you own it!

I used to HATE doing fillets using Epoxolite but now that I use aeropoxy Lite they are almost an afterthought!

Mayhaps I'll try carved balsa next time. I hear that works pretty good too!

Bigs

" What constitutes the dignity of a craft is that it creates a fellowship, that it binds men together and fashions for them a common language. For there is but one problem - the problem of human relations."

>On fillets. So I paid lots of $$ for some "great" epoxy
>called AERO EPOXY. I was convinced it could be sanded. But
>no, mon amiee! The stuff is no better than SIG EPOXOLITE.
>What this world really needs is a fillet material that can
>be sanded! Even when mixed with microballons, it hardens
>like cement (concrete, that is) and defies any sandpaper
>known to man or beast.
>
>Floyd

Ron B.
F4Fguy

Floyd:

If you have trouble sanding Aeropoxy,it's probably not mixed right.This is a wonder material,but it absolutely MUST be mixed in the proper proportions,BY WEIGHT,or it becomes your worst nightmare.Used right,it sands like balsa(admittedly hard balsa),and weighs about the same.I agree completely on the price though.

SIG Epoxylite is nothing like Aeropoxy,it's hard as a brick,and very heavy.The only similarity is the color.You can make a useable mix if you add at least 1:1 volume of phenolic microballoons to the mixed Epoxylite.

On the other hand,my favorite fillet material is balsa,either carved or molded sheet.

West or other straight epoxy and WEST #310 microlight filler. Sands almost like balsa.

get it from Aerospace composites or local marine supplies dealer.

>For those small cracks you can sand lightly and put a few
>drops of cyano before blowing off the sanding dust and
>repeat as necessary.
>
>Tom

Ron B.
F4Fguy

TOMK:

Be very careful with CA around foam cores.Use only the "Gold",foam friendly variety,and try to avoid kicker.Many kickers will dissolve foam,and even those which don't cause (as they're supposed to),very rapid curing,releasing a lot of heat.The heat can melt the foam locally.

If you are going to use sanding dust and CA, you can also use baking soda and CA. The trouble with ANYTHING and CA, IMHO, is sanding after filling.

How about carbon veil (or mat) and dope?

Thanks for all the input guys. Just what I needed!

Today we begin pre-sanding of the wing and fuse construction