Preparing wings for painting

[Michael Little]

Im building my first RC plane and I'm at the stage now where i need to join the wings together and paint them. Its a foam wing with balsa sheet covering (Acro wot) i would like to keep the wing as light as possible but not sure how to prepare the wing. I have purchased model light deluxe filler to fill in some slight gaps in the balsa sheet but thats all so far.

Thanks, Mike

[Stevo]

Save yourself a lot of grief and use Profilm or similar.. as it's your first - unless you have some paint scheme in mind?

[cymaz]

Some 50:50 PVA / water brushed onto the frame and then allowed to dry will aid the film to stick well.

[Michael Little]

I would rather paint now as iv got a simple colour scheme and ive purchased the paints already so just need to know what to put on them that i can just paint over.

[Stevo]

Exactly what paints have you purchased?
Is your model electric or glow?

[Stevo]

I've painted a lot on timber, and I don't mean Dulux - I also build guitars as well. For a faultless finish without the grain showing through, you will either have to glass cloth and epoxy it, or perhaps use PVA and brown paper as some have done on here. That will give you an excellent base for painting over. That's before you've hit it with a primer coat.

Grainfilling (even with a proprietry grainfiller) wont have much effect as the grain is quite tight.

Also bear in mind that the above adds weight, which is not required for an aerobatic model; for a lumbering old beast of a scale model perhaps but not an acrowot!

If your colour scheme is one base colour with designs over the top, again I'd cover with profilm or similar for that colour then mask/spray over that.

Sorry - just gone through your posts and I see that it's a glow model.  Also don't forget to fuel proof the paint if they are not already - more weight

 

Edited By Stevo on 31/07/2017 08:24:41

Edited By Stevo on 31/07/2017 08:25:38

[Michael Little]

Hi Steve, yes its a glow model, I've got Spectra Fuel Proof Paint. Im not after an amazing finish but i just think the profilm would be very hard to apply especially now i have glues the fins in place!

I was just thinking that i could get a light cover of something on the wings before painting them to have the wood soaking up all the paint

[Allan Bennett]

Even though you've already bought the paint, I would strongly recommend you use an iron-on covering such as Solarfilm, Profilm, etc. They will probably end up lighter than paint and, more importantly, they add a lot of ding-resistance to the structure.

An alternative that I sometimes use is to cover the structure with 25g glass cloth and resin, then sand down and paint it.

[TIM Shaw]

Hi Michael.

Conventionally, I would complete all my building work before thinking about covering and painting.

So when you say you are ready to join the wings I think you actually have quite a bit of stuff to do before you get to the paint.

Are you using a single, central aileron servo, or individual ones for each aileron?

I would be cutting out the mounting boxes now before joining the wings in either case, and you will need to form the servo lead tunnels in the second case.

Then I would join the wing panels with epoxy, using the beds to keep them straight and blocking up for any dihedral - can't remember off - hand if the Acrowot has a flat upper surface - if it does, it's easier to join them upside down.

Once set, I would cut a slot right through the wing to take a full depth, 3" long 1/8" balsa sub spar, about 2 " back and parallel to the leading edge - this is not mentioned in the build instructions but will save you a lot of trouble with your wing dowels working loose in the foam in the future.

Once that is glued in and set, complete your servo box lining, then sand smooth and fill any minor imperfections.

Then you need to apply the reinforcement, which can either be epoxy and glass bandage or surgical bandage and PVA (or epoxy - but I wouldn't try PVA on glass myself).

Next step is final sanding, then covering., because you will not get a durable finish painting directly onto the wooden wing skins, probably Obechi, if building from the kit.

For a painted finish you could use doped on Modelspan tissue, or lightweight glass cloth to cover the entire wing with, and only then can you start to think about getting a decent surface finish and going through the various coats..

[Michael Little]

I have 1 sevo in each wing, already lined out and drilled ready to install servos, and the servo lead tunnels are already there i just had to cut a slot in each wing to bring the servo leads out to plug in the plane. Ive got epoxy to connect the wings together with the supplied fibreglass strip to bong the wings together.

By Sub Spar do you mean a tube to put across both wings to give strength during high speed manoeuvre? And i plan to Add a strip of wood for the dowels to strengthen them.

I wanted to try avoiding adding glass and resin for the wings so i think i may try the doped Modelspan Tissue if its any lighter.

Thanks for the advise!

[Brian Spearing]

If the wing cores are polystyrene, you need to be sure the dope cannot the foam through the wood skin.

You mention fins being attached - I guess that's referring to the fus. Wings can be covered in Profilm (easy) and the fus with glass+epoxy for a totally fuelproof and hardwearing finish. And fin and tailplane in either method.

[TIM Shaw]

Posted by Michael Little on 31/07/2017 13:30:03:

By Sub Spar do you mean a tube to put across both wings to give strength during high speed manoeuvre? And i plan to Add a strip of wood for the dowels to strengthen them.

I wanted to try avoiding adding glass and resin for the wings so i think i may try the doped Modelspan Tissue if its any lighter.

Thanks for the advise!

Hi Michael.

The subspar I referred to is just that strip of wood to anchor the rear of the wing dowels to both skins, no need for any tubes..

If you really want to go old school, take the time to look the technique up.

I would apply a light coat of sanding sealer first, rub it down with wet and dry, maybe give it another.

Then a coat of full strength dope.

Tissue has a grain, which needs to be applied spanwise, and a shiney side which should be away from the wood.

Cut it to shape, wet it and wring it out. Lay it over your panel, and then brush 50 /50 thinned dope through it, smoothing it out as you go. Note that coloured tissue was available, which is the lightest way of adding colour.

do one panel at a time abd build up subsequent coats as necessary until ready for painting.

I'd be using a similar technique with nylon on the fuz, just to add a bit of strength to it.