Back to U/C modeling after 50 years.  What is available for filling external joints such as wing to fuselage, etc?   I'm really looking for a putty-type material to fare-in joints before final finishing.  Back when I was actively building we used Ambroid glue and just smoothed a bead into joints with fingers.   Can someone recommend a product or two?

there are several options, charles stated he uses microballoons and epoxy, this is the old school way, its heavy and not very user freindly.
I have tried epoxylite and a couple others including epoxy and microballoons, I dont like any of them,
The product He mentioned is called Superfill. It is the cats meow, its light, very strong, and easy to work with.
it is available from Aircraft Spruce and SPecialty company. YOu have to buy a large quantity, but it goes a LONG LONG way

Charles:   What are micro-ballons?

Charles:   What are micro-ballons?

Steve, They are little glass spheres and are used as a fill substance with resin.
I don't recommend the as they are weak. Much better is "Milled" fiber. These items can be purchased at your local surf shop.

Cheers, Jerry

Charles:   What are micro-ballons?

Steve,

That's a good question.

I honestly don't know and I really don't have to know, neither does anyone else.

Let me explain.

Micro-balloons are tiny tiny bits of "something?" almost like a powder, that you mix with Epoxy, or back in the day when we used Polyester resins. That's Old School.

I don't think what is in the container is "Glass." Maybe the answer is at Google.

Anyway, you mix micro-balloons with Epoxy and the ratio gives you a mixture that enables you to do quite a few things with it. That's why I like it.

Mix a bit with Epoxy and hardener and it still remains a strong "glue" or bonding chemicle, which BTW would be difficult to sand but remain extreamly strong. R/C .25" plywood firewalls for example.

Add a greater ratio of the mix and you wind up with a dry "extremely light" material that can be used exactly for the use you inquired about. At the dry but sticky state, it dries quickly and is easy to sand.

SUPERFILL.

I thought about it, but blue isn't my favorite color. 

Superfill is still an Epoxy and requires a two part mix, A and B just like any Epoxy. However, it's consistancy is already in paste form. I'm not sure the consistancy can be controlled.

Never used it, thought about it, I did do a quick study. Works well for those that want to use it.

Choices? Aren't choices great.

My winning game is Micro-balloons made by Top Flite. 5.99 most hobby shops. Been using it on all my R/C models and now my CL models.

I use very little because I don't like the build up or large fillers.

All these following models have micro-balloones used on them in one place or another, especially as a filler at the wings and fuselage.

Oh, and I used no colored dope as paint.

Steve, welcome again. Buckle up and hold on to something!

Charles

contribute nothing to strength when used.

How's that? The user has control of the mix, well explained in my text above.

YOU control the strength by adding whatever percentage of micro-balloons you elect.

I've been there done that a hundred times. Old and new school. Also works well when gluing formers in fiberglass fuselages cut 50%, as an example.

Try that with Superfill.

Someone, in a unrelated Thread, just said they do this 50% mix with it when building. Maybe MM said it?

Here's my personal take. The micro-balloons work for many applications, so why have a couple more containers around that do the same thing, but less things?

And, as I said, that color.

BTW, I mix black artist paint with it to get a shade of gray when I use it. The Gee Bee R-3 is spotted with it.

"Epoxy=Epoxy"

Back to U/C modeling after 50 years.  What is available for filling external joints such as wing to fuselage, etc?   I'm really looking for a putty-type material to fare-in joints before final finishing.  Back when I was actively building we used Ambroid glue and just smoothed a bead into joints with fingers.   Can someone recommend a product or two?

after re reading this, I wonder if you are refering to problems like ill fitting sheeting? or were you talking about places like fillets..
for fillets and that like, then Superfill is the answer.
if you are talking about filling flaws in fitment or dents, thats another issue entirly.. thats where I would use lacquer spot putty like this
https://www.amazon.com/3M-05096-Acryl-Green-Spot-Putty/dp/B004BZOTQQ

be advised, this is an air dry product and it will shrink just like dope , it is intended for very small imperfections, very small, and apply in layers with sufficient dry time.
Some people use catalysed spot putty like evercoat, but on bare balsa its hard to sand it smooth since it is harder than the balsa by a bunch..

Please feel free to contact me for any additional information.. I have a little experience with painting and such,, 

Steve,

That's a good question.

I honestly don't know and I really don't have to know, neither does anyone else.

Let me explain.

Micro-balloons are tiny tiny bits of "something?" almost like a powder, that you mix with Epoxy, or back in the day when we used Polyester resins. That's Old School.

I don't think what is in the container is "Glass." Maybe the answer is at Google.

Anyway, you mix micro-balloons with Epoxy and the ratio gives you a mixture that enables you to do quite a few things with it. That's why I like it.

Mix a bit with Epoxy and hardener and it still remains a strong "glue" or bonding chemicle, which BTW would be difficult to sand but remain extreamly strong. R/C .25" plywood firewalls for example.

Add a greater ratio of the mix and you wind up with a dry "extremely light" material that can be used exactly for the use you inquired about. At the dry but sticky state, it dries quickly and is easy to sand.

SUPERFILL.

I thought about it, but blue isn't my favorite color. 

Superfill is still an Epoxy and requires a two part mix, A and B just like any Epoxy. However, it's consistancy is already in paste form. I'm not sure the consistancy can be controlled.

Never used it, thought about it, I did do a quick study. Works well for those that want to use it.

Choices? Aren't choices great.

My winning game is Micro-balloons made by Top Flite. 5.99 most hobby shops. Been using it on all my R/C models and now my CL models.

I use very little because I don't like the build up or large fillers.

All these following models have micro-balloones used on them in one place or another, especially as a filler at the wings and fuselage.

Oh, and I used no colored dope as paint.

Steve, welcome again. Buckle up and hold on to something!

Charles

Thanks guys, I've learned alot and it's nice to have experienced builders to ask on these subjects.  I'm a silk and dope guy from back when there weren't many options on finishing products so my learning curve is pretty steep right now.

Charles, that 007 plane is beautiful.  Not now, but I need to hear you explain how you composed those graphics.  Do you have a YouTube video by chance on this?

Steve

Mark,

Certainly and I believe everyone knows that microballons mixed with Epoxy will take some of the strength away.

70's and 80's, I remember them well, those were my active R/C days. You didn't enter into this hobby till the early 2000's. About 16 years correct?

Charles

I re-entered the hobby in about 2007, however I worked in the aerospace industry designing, and building parts for aircraft,, the ones people flyin,, and building molds, and parts for glass parts on same aircraft,, whats your point,, I also read magazines while I was raising my family since the early 70s.., I also talk to people who know, and LISTEN to them,, hence i learn,,

so are you implying I dont know history, or that I dont know what I am talking about,, I dont understand your comment

after re reading this, I wonder if you are refering to problems like ill fitting sheeting? or were you talking about places like fillets..
for fillets and that like, then Superfill is the answer.
if you are talking about filling flaws in fitment or dents, thats another issue entirly.. thats where I would use lacquer spot putty like this
https://www.amazon.com/3M-05096-Acryl-Green-Spot-Putty/dp/B004BZOTQQ

be advised, this is an air dry product and it will shrink just like dope , it is intended for very small imperfections, very small, and apply in layers with sufficient dry time.
Some people use catalysed spot putty like evercoat, but on bare balsa its hard to sand it smooth since it is harder than the balsa by a bunch..

Please feel free to contact me for any additional information.. I have a little experience with painting and such,, 

Thanks Mark.  I was talking about both actually......fillets and maybe a ding or two.  I'll try some Superfill and will get some of the spot putty.   I'm assembling my building materials from scratch so experimenting is expected.  I have a 1966 George Aldrich Nobler stunter and two, full-kit Ringmasters.  One is completed and has flown, and one is still in the kit box.  Both are early '60s vintage and belonged to an avid modeler who passed away recently.  I bought the two Ringmasters, a Fox .19, a Redhead McCoy .35 and a Cox .049 last Saturday here in Memphis.  The Nobler has always belonged to me and I built it originally after building two Ringmasters and a couple of slab 1/2A planes.  After 50 years and having traveled in a crate to England for two years (a very long story.....), the Nobler has a little hanger rash that I'm touching up and that has been the genesis of all the questions about dope, fillers and putty.   My own engines are a Fox Stunt 35 for the Nobler, a Fox 36X (non-BB), a McCoy Redhead .35 and a Cox TeeDee .051.  I've gotten some Klotz castor and worked out the math to bring the fuel up to 28% castor for the Fox engines and I'm mostly ready to go this weekend with the Nobler.   I fly by myself, so I've got to build a stooge launch device but that won't be tough.  Thanks again for all the advice and offers of help.