Filler for foam

[bodgerep]

Hi All

Am wondering what filler you all use, ie to fill up dents, scratches and sometimes the cracks on joints ?

In the past I have used various but mostly No nonsense lightweight filler.   While its easy to sand it has little hardness and was wondering if I am missing some product that is a bit harder and better?

Best Wishes 

[SIMON CRAGG]

Over the years, I have used various so called lightweight fillers. As yet, I have not found a decent one, and they are VERY expensive. They usually have a rubbery finish, are awkward / hard to sand. I have gone back to purchasing large boxes of cheap filler powder (think Poundland). Easy to apply, and best of all sands well. I picked up a good tip somewhere on how to repair hanger rash, which I always use.

1. Fold a kitchen towel into four.

2. Soak and ring out in water.

 3.Place over damaged area.

4 Carefully apply heat from sealing iron.

Using the above method will either remove the blemish or leave a slight "crocodile" finish, Apply filler and rub down / paint etc.

Works for me anyway.

[Edgeflyer]

Use heat very carefully! The outer layer of closed cell foam bubbles are compressed to give a nice smooth surface. Heat pops them back to spheres! Hence the crocodile surface.

A method worth trying: ,mix  slow set epoxy with micro balloons (glass powder) to quite a stuff mix then apply with a pallette knife. Clean off overlap areas with meths on kitchen roll. Then cover gently with a piece of cellophane wrapping and smooth down as flat as you can with a thumb. When dry lift off the cellophane. Gives a shiny smooth surface that sands very easily. Repeat to fill small imperfections. Paint with acrylic model car body paints. If necessary spray with polyurethane Lacquer(cheap from Lidl or Wilko)  With patience this gives almost perfect results.

[Edgeflyer]

If you can't get glass powder, I have used cornflour as a filler powder. It is just a cellulose material. You can also mix this with clear silicone, squeezed from a cartridge to make a slightly flexible rubbery compound that can be moulded by hand! Check you tube.

I also repair foam models with the better (i.e. more expensive) versions of "no nails." It sticks well, is easy to apply from a cartridge and cleans off with a damp cloth. Dries white and stays flexible.

[bodgerep]

Thanks very much for the replies.

 

A question to Simon. I am not familiar with filler powder, is it basically glass or something else, will need to look at this stuff.

 

Phil, I have a load of glass micro balloons, before getting into rc planes I did quite a bit of glass fibre work on boats, mostly polyester resins not so much epoxy, and I have some materials left over including the micro b. I have tried mixing the glass with epoxy, was a bit worried that glass is heavy and when I tried it, I found it difficult to sand. From what you say, am thinking perhaps I did not put enough glass into the mix, will give it another try although I like the no nails solution. This seems ideal, esp the wiping with a damp cloth. Does it sand or do you have to get it exact before it goes off?

Best Wishes - John

[Edgeflyer]

No the flexible adhesive like "no nails" does not sand. It's for joining breaks not filling imperfections. Use the epoxy and powdered glass for filling as it sands. Clean with meths. Use a fairly slow set epoxy as the filler powder seems to accelerate setting slightly.. I also sometimes use styrene resin based filler which is sold in car parts shops. That is mainly for filling cowls and similar fibreglass pieces. It sands well.

[SIMON CRAGG]

10 hours ago, bodgerep said:

Thanks very much for the replies.

 

A question to Simon. I am not familiar with filler powder, is it basically glass or something else, will need to look at this stuff.

 

Phil, I have a load of glass micro balloons, before getting into rc planes I did quite a bit of glass fibre work on boats, mostly polyester resins not so much epoxy, and I have some materials left over including the micro b. I have tried mixing the glass with epoxy, was a bit worried that glass is heavy and when I tried it, I found it difficult to sand. From what you say, am thinking perhaps I did not put enough glass into the mix, will give it another try although I like the no nails solution. This seems ideal, esp the wiping with a damp cloth. Does it sand or do you have to get it exact before it goes off?

Best Wishes - John

The filler I use is usually used for repairing small holes in walls prior to decorating. Polyfilla or the cheap stuff I get from Poundland in 1KG boxes. No need to spend a fortune on it!.

 

[bodgerep]

Hello again Simon,   I remember now, the dry powder filler I used to get many, many years ago.  I didnt realise it was possible to still get that, will look more closely in future, as the pre mixed stuff tends to harden after a few months.    Am thinking it may be possible to lighten in up with a bit of talcum powder or something if needed.

Phil, you probably know but I will mention it anyway, styrene will defo melt foam, used to use it all the time when working on boats.   Somewhere I still/used to have a container of styrene, used it to make resins more runny.   Trouble is, once you open the container it seems to evaporate v quickly, even with the container top firmly screwed on.   Never knew why, chemistry is/was not my subject  🙂

Once again, thanks to you both   -    John

 

 

[Engine Doctor]

The two pack styrene fillers work well on expanded polypropylene foam  now used under various names for our models, but dont trying on polystyrene foam as it just dissolves it. If assembly instruction say you can use ordinary cyano then the two pack fillers should be OK. As always try a little area first. Car body filler will work but its harder to sand and heavy . I have found that Ronseal WoodFill is a good filler for foam . It lighter and than car filler but heavier and stronger  than the really light diy fillers and sands easier. It comes in white or beige  and sets very quickly. 

Edited November 9, 2022 by Engine Doctor

[Edgeflyer]

22 hours ago, bodgerep said:

Hello again Simon,   I remember now, the dry powder filler I used to get many, many years ago.  I didnt realise it was possible to still get that, will look more closely in future, as the pre mixed stuff tends to harden after a few months.    Am thinking it may be possible to lighten in up with a bit of talcum powder or something if needed.

Phil, you probably know but I will mention it anyway, styrene will defo melt foam, used to use it all the time when working on boats.   Somewhere I still/used to have a container of styrene, used it to make resins more runny.   Trouble is, once you open the container it seems to evaporate v quickly, even with the container top firmly screwed on.   Never knew why, chemistry is/was not my subject  🙂

Once again, thanks to you both   -    John

 

 

Thanks for the warning but styrene doesn't melt modern foams that are not polystyrene based. I mostly use the epoxy and powdered glass mix on foam. But styrene based types sometimes on GRP.