A warning about fillers

In the UK we do not have "spackle" due to the different way we apply joints and finishes to "drywall" or "sheetrock". We call it "plaster board" and the joints are sealed with a mesh net followed by the boards having a complete coat of gypsum plaster applied.

We have many fillers but they are all heavy.

I search the interweb and quite a few forums and found that Polycell "No Sanding" was recommended. I checked with a mate of mine who makes scale planes and he heartily recommended it. So I bought some.

Big mistake. It was heavy and difficult to apply but easy to sand. It went on lumpy and even my wet finger didn't smooth it out. I couldn't believe this and then on one forum there was an outbreak of insults and some very venomous posts (I hate that!).

When I saw him some months later, I told him that he had sold me a pup. He got his Polycell "No Sanding" tub out and demonstrated a perfect fillet completed in seconds. His tub was exactly the same as mine Identical tubs! However, the material in min was grey and his was white. My tub was about 4x heavier.

We went to one of the DIY chain stores and all their tubs were heavy - you could tell straight away. Polycell had changed the formula.

So be warned! What you use and buy today maybe not the same tomorrow!

He went on a tour of DIY places and scooped up all the older versions he could find.

I then found Polycell "One Fill" - lightweight, no or little sanding with no sagging. It is not designed for balsa filling etc... It is designed for filling deep gaps in plasterboard, plaster and masonry... but it works a treat and is cheap.

So, in my opinion, Polycell One Fill is the nearest thing to spackle in the UK.

@rsv1cox - So, in the end, which one do you or would you recommend to use on fillets and such. The 'Fast N' Final, or the DryDex? By reading, I am suspecting the DryDex. I am curious as I am going to be buying something shortly for this application as well as for minnow surface imperfections and want to do it only once if possible. Thank you.

I was under the impression that "micro-balloons" was a good filler for a dope finish. I believe you mix it with dope.. so it's going to be compatible with a dope finish.

Microballoons have made wonderful strong filets for me, mixed with epoxy to peanut butter consistency.

On small planes, I use the Dap light weight... so light the tub feels empty. After it dries I've sanded it to shape and soaked it with thin CA and it becomes shiny rigid cement, can no longer be sanded for shape, but just a buff that paint can adhere to. I've never had one separate from it's balsa base or break in a crash.

The only one that has had any sign of trouble is a wide 1/2" wing root filet on my Yak-9, and it developed a hairline fracture from the LE and back a couple of inches. It was almost invisible but I forced it apart by flexing down on the wing and drew a line of thin CA along it with a hypodermic needle, then closed it. It's been fine since then, a couple of years ago, probably 25 flights. I blamed it on the Fox 35, but I did bonk it in hard grass once while figuring out the tank position.

And the whole faring of the 3/8" thick IB tripler into the fuse on the Yak is made of light Dap and CA. It's never cracked, and the Rustoleum paint is still perfect, one of my better jobs. I used flat white because I think it gets better adhesion and covers better, going on lighter than glossy paint. I lightly wet sanded it and the clear Lustrekote gives it a glassy shine every bit as glassy as if I'd used glossy paint. My buddy Ron can testify to that.

Always use your Rustoleum hot. Shake it 3 times as long as the instructions say. Stop and swirl the ball around on the bottom of the can frequently(In fact, start by doing that) and re shake every minute or less while painting. Keep it hot for the period between coats.
Rusty

NEW222 wrote:@rsv1cox - So, in the end, which one do you or would you recommend to use on fillets and such. The 'Fast N' Final, or the DryDex? By reading, I am suspecting the DryDex. I am curious as I am going to be buying something shortly for this application as well as for minnow surface imperfections and want to do it only once if possible. Thank you.

Hi,  I've sworn off the Fast'N Final for the reasons expressed.  I like the standard DAP spackling but I use it very sparingly due to it's weight. It's been great filing small holes and dents in this beat-up model that I'm working on.

I remember Micro Balloons, it came in a white tub as I remember, but I never bought any.  

Bob

PS - I have never used one of the commercial sprays due to perceived hot fuel issues and weight. I would guess it's more economical, about $4 vs $7 for the Lustrkote. But it seems to be quite popular here so I may in the future give it a try.

I haven't used any filler other than balsa dust and epoxy mix , that's good to know that not all play together well. I did notice on my last build using rusty-olem  over dope/sanding seal the paint peeled were the fuel tank was ONLY 35% nitro out the over flow .. that's weird considering it was all over the plane (but burnt) Those micro balloons are pretty expensive from Sig anyway . getback

Micro balloons from Sig is less than $6. There's enough micro balloons in that container to suffice 6 modellers lifetimes. A benefit of micro ballons is that it's compatible with every finish available. It mixes with epoxy, solvent based adhesives, etc. It's real name is Cab o sill. It's nothing more than a thickening agent.The more your mix, the weaker the strength allowing it to crack. Epoxy in general is problematic with solvent based paints as the surface needs to be cleaned properly. When using micro balloons and epoxy for fillets, it becomes a must to wrap a dowel in sandpaper and sand the entire surface exposing the balloons and thoroughly cleaning the fillets with acetone or lacquer thinner prior to painting for good adhesion. Don't sand this product until the epoxy is cured which is about 2 days. Don't brush dope into an intersection, it will pull back and blister as Bob shows. Sanding sealer will do this the worst. Don't brush dope onto fillets, if need be, lightly spray it on.

Once you learn the techniques, you can apply the modified epoxy onto the fillet areas with a glass like finish. Mask the surrounding areas if needed and clean the residual spill over with a bit of lacquer thinner.