Covering / finishing

[Basil]

Hi, it's me again, I can hear the groans.

I have made two efforts to use the modern temperature sensitive films that are available these days, the last one was very good( For a novice that is) I thought. I have a model that has a slab sided fuse that for effect needs covering in part, in order to look the part,  There are areas, such as the cowl and smaller areas  that would be very difficult the 'Cover'. I am also intending to paint the film with camo colours.

I will summerise my questions.

1) Why dont I see references to using sanding seal under film?. ( Does the Rosin in the sealer melt!!!)

2)Why use film (In some ares only) instead of sealer then colour?( Sinkage may occur)

3 There are areas such as sheet tail/elevator/fin etc that as a novice ,like me wonders why they cant be just sealed then panited instead of filmed  then painted  I know paint adds wieght but where its going to be camo'd why film cover as well.

I could go on but there are obviously a set of rules that I am going to be presented with, so I'll await to hear the correct way. Thanks in advance.

Bas

[Phil McCavity]

You can mix film and paint finishes to your hearts content if that's more suitable for you Basil. Just because you started with one doesn't mean you have to stick with that for the entire model, mix and match to give you the best result to match your desired vision for it and your ability. I have a model that I'm covering with a mixture of polyester dress lining, film and paint (even a few litho strips) because it is my best option, I have also (against the advice of Solarfilm) sealed the wood with sealer or dope before ironing but you need to be careful if you do that as it's easy to get wrinkles on a sheet surface and you don't get a second chance with it.

Edited March 10, 2021 by Phil McCavity

[John Stainforth]

I would test any combinations before trying them on a model. Many plastic paints and plastic films are not very compatible with each other. Epoxy paints, which are excellent in many respects, don't adhere well to many plastic films. (For example, certain plastic films make good separating layers during priming or painting to prevent epoxy sticking!)

[Engine Doctor]

Hi Basil . sanding sealer can affect the bond between film and the wood . A simple way to get a smooth finish is to apply a thinned dope to raise the grain. sand lightly and dust off then apply film . 

[Danny Fenton]

Hi Bas, there are only two ways you are going to know these things, trial and error and asking. I would suggest ask, if you don't agree with the the answer "try" then you will know from experience. There isn't really a short cut.

What the others have said is true, you need to seal the wood before you can paint it. This isn't a single coat of dope in most cases, and requires a bit more effort, okay a lot more effort if you want it to look good.

With film you do not need to do anything to prepare the wood. You may need to help the film to stick really well with something like Balsaloc over ply, but I have usually found the adhesive backing on the film is good enough.

 

Let me show two examples of the same airframe:

 

Monokote

 

Silkspan

 

These two Ringmaster S1's were both made from the same plan. One is film covered, in this case a rather super film called Monokote, the other is covered in Silkspan, which funnily enough isn't silk but tissue paper and applied with dope.

 

The Monokote Ringmaster took about 2 hours to cover.

The tissue and doped Ringmaster took 2 days.

4 coats of thinned dope to seal, sanding between each coat. Then the tissue was applied, with a further 4 coats  heavily thinned. These were also sanded between coats. VERY lightly on the open structure!! A slip here and you go through the tissue on the ribs.

Then it will require a few coats of paint, sanded then lacquered.

 

So it depends what you want, the tissue and dope approach will in my opinion give a stunning finish, if you do all those steps. The film will give an equally glossy finish very quickly.

 

The tissue will impart a lot of strength to the airframe, film adds nothing to speak of.

 

So you have to decide how much effort you want to put in, imo paint takes a lot of preparation or it will look pants. But done right, there will be no joins, overlaps of film and the entire surface smooth as glass. It will also be stronger. Paint will always win in my book.

But for speed, film cannot be beaten.

 

Cheers

Danny

 

[Basil]

Many thanks Danny. Yes cant beat a bit of try and see. In order to try and test you need to know whats available and how to do that task properly. For me I dont know whats out there so by asking stupid/irrattating questions at least get to find out the possiblities, and learn a great deal in the course of a conflab.

Meant to ask , is there a smaller 'Iron' available for those fiddley areas?

Thanks very much for your answers. By the way like the Auster, been following closely.

Bas

Edited March 17, 2021 by Basil

[Danny Fenton]

Hi Bas, I have a normal sized covering iron, I think you can get smaller ones for detail, I have managed so far without. The Prolux iron I have has a digital temp readout, and seems fairly accurate.  

Keep asking the questions, its not a problem at all, most of us are only too happy to pass on information, just remember we nearly all have our own ways of doing stuff, and what works for one may not work for you. e.g. I apply tissue wet, always have done, others prefer to apply it dry, its what you are comfortable with.

Glad you are getting something from the Auster, its an interesting build definitely a 70's design for the most part, and oh, would I do it differently lol

 

And in case you haven't noticed, I am asking loads of irritating questions about I.C. for which I have no idea ? currently staring at a fuel tank thinking er....... okay.

 

Cheers

Danny

[Ron Gray]

@Basil Clover mini iron for which there are different tips, thin and ball. Takes a while to heat up and only 2 settings but works well.

[Basil]

On 17/03/2021 at 11:58, Engine Doctor said:

Hi Basil . sanding sealer can affect the bond between film and the wood . A simple way to get a smooth finish is to apply a thinned dope to raise the grain. sand lightly and dust off then apply film . 

Hi, I know its a long time since you answered but!!!!!

I need to fill areas before covering;

1) what type of filler is reccomended, I've tried the Model lite, but it does not apply easily or evenly, not like fillers used in ordinary wood work applications.I saw in one post that the person was using what looked similar to Polyfilla, Red & white pack,but cant find the post.

2) Surely filler will need to be sealed if film is used. As you suggested diluted Dope, I take its non shrinking , what do you use to thin it and what sort of ratio ?.  I'll have to get it on line, where do you suggest. The last time I used dope was in the 1960's apart from the smell I cant remember anything, apart from which I was a novice then , as I am now.

Any contributions about finishing ,gratefully recieved.

Bas

[FlyinBrian]

If you are filling balsa then a diluted coat of PVA glue is a quick and easy option for sealing.

 

Also if the hollow in balsa is a dent rather than a dig just dampen-ing the area is often effective in swelling the balsa back to size

Edited April 10, 2021 by FlyinBrian
Typo

[Ron Gray]

For lightweight filler, I use this Red Devil

 

[Basil]

Hi Brian, I like the sound of that as it does not require having to get hold of thinners as well as Dope, and wood adhesive I have plenry of.

In the course of my efforts working with timber I use matt/satin  water based varnish. It dries to a hard finish, I am not keen on using it as a finish , but again it eleviates the use of hydro carbon solvents/thinners and sands up OK.

thanks. Because of the dangers of transporting highly flamable liquids carriers tend to charge quite high rates, as every body knows.

Bas

[Basil]

Just come across the name of the filler named in other post, 'Tourpret'.

What do you think.

Bas

[Engine Doctor]

I just use "Light filler" from local model shop if needed, there a quite a few different makes available . If you want a quick filler the "Woodfill" by Ronseal  is very good and not too heavy sands easily and the beige blends in with balsa well.  The filler should be wet enough to adhere to the balsa then allowed to dry overnight. sand and give a coat of thinned dope .  I use any either type of dope to seal wood as long as its well thinned .

 

 Many small dents can easily be removed by wetting the dent and applying you covering iron over the dent.

the steam make the dented balsa swell back to shape .