Brown paper covering?

[Edgeflyer]

I've often read about brown paper covering models. How is it done given the 3D shapes involved?

[Ron Gray]

Slowly and carefully but overlaps can easily be rubbed back.

[Futura57]

Do it in small sections/panels and orient them sympathetic to a largely single curvature direction. Some stretching is possible to accommodate a little double curvature,  but it depends upon how long you let your diluted PVA soak in. I tend to use brown paper like thick tissue. I make it quite wet and delicately stretch and push it down on to the surface. Once thoroughly dry, overlapping areas are easily sanded to disguise joints. I try to tear my brown paper pieces to shape to get a more feathered edge, giving invisible overlap joints with minimal dry sanding with 240 grit paper. I use titebond wood glue, which I find sands better than some cheap rubbery PVA.

 

For example, think about how a boat hull is formed from straight flat planks. For a warbird fuselage consider rings of paper wrapped around, perhaps between where the fuselage formers are positioned. Cowls can be a bit more challenging,  but all doable. 

Edited September 4 by Futura57

[Edgeflyer]

Thanks that's very helpful. I was thinking cellulose wallpaper paste as I would be doing the final covering on top. We used to use wallpaper paste for the initial fix of nylon on combat planes before doping.

[Edgeflyer]

Also that way I can remove it easily if it fails

[MattyB]

This should help from an old post I made, follow the embedded link tin thus post to RCGroups for a detailed guide ! 
 

 

[MattyB]

Hmm, maybe easier if I post that link directly hey!!! 
 

https://www.rcgroups.com/forums/showpost.php?p=17091991&postcount=4

[MattyB]

And also.. 

 

[Mike T]

A word of caution on wallpaper paste.  I bought some cheap patching paste to use on my first attempt at brown-papering over the carved/sanded pink foam nose of a friend's Vulcan.  It went on fine and I left it to dry overnight.  When I picked it up in the morning, it all flaked away (albeit each piece kept its shape, perfectly formed!).  I tried again with the same result.  I gave up and returned the plane to my friend who got it to work using 'Mod Podge' (a thickish PVA-ish concoction used by diorama modellers).

 

So based on my limited experience, I'd advise sticking (lol) with PVA!

[Engine Doctor]

Same applies to PVA . Dont use the cheap stuff like N* non****. Proper Unibond or a decent brand works much better . Apply a wet coat to the paper and while its soaking in , a bit like wallpapering , apply a thin coat to the model .  then when paper is nice and pliable lay it on the model and smooth down and allow to dry . Once dry light sand using a fine paper and a apply a thin coat of PVA to seal the surface . 

[MattyB]

49 minutes ago, Mike T said:

A word of caution on wallpaper paste.  I bought some cheap patching paste to use on my first attempt at brown-papering over the carved/sanded pink foam nose of a friend's Vulcan.  It went on fine and I left it to dry overnight.  When I picked it up in the morning, it all flaked away (albeit each piece kept its shape, perfectly formed!).  I tried again with the same result.  I gave up and returned the plane to my friend who got it to work using 'Mod Podge' (a thickish PVA-ish concoction used by diorama modellers).

 

So based on my limited experience, I'd advise sticking (lol) with PVA!

I agree stick to good quality pva - i this technique is cheap enough compared to shrink films already, so it’s not worth try using wallpaper paste instead in an effort to reduce cost further

[Ron Gray]

36 minutes ago, Engine Doctor said:

Apply a wet coat to the paper and while its soaking in , a bit like wallpapering , apply a thin coat to the model

Sorry ED but I disagree. The brown paper should not get too wet, usually as a result of overthinning the PVA and can result in the paper just falling apart when you try and apply it. Secondly there is no need to apply a thin coat to the model before applying the paper. If you use good quality PVA (although my one of choice is Jewson's as can be seen in my vids) thinned no more than 5% then it will not soak straight through the brown paper and when smoothed out on untreated surfaces can be worked into curves without tearing resulting in a largely bubble free surfaces.

[MattyB]

23 minutes ago, Ron Gray said:

Sorry ED but I disagree. The brown paper should not get too wet, usually as a result of overthinning the PVA and can result in the paper just falling apart when you try and apply it. Secondly there is no need to apply a thin coat to the model before applying the paper. If you use good quality PVA (although my one of choice is Jewson's as can be seen in my vids) thinned no more than 5% then it will not soak straight through the brown paper and when smoothed out on untreated surfaces can be worked into curves without tearing resulting in a largely bubble free surfaces.

The method I was taught and linked above was to soak the paper in water first to ensure good  and even shrinkage as it dries. It's always worked for me:

 

• Cut your brown paper sheets out 1/2 to 1 inch oversize compared to the panels (you're going to do top and bottom together);
• Put the paper panels in the bath to soak for a few minutes;
• Dilute your white (PVA) glue - opinions differ on this, but depending on the use and the weight/toughness balance you want, it can be anywhere between 2:1 (glue:water) and 1:2. Add some food colouring if you want to make it easier to see where you've wetted out;
• Pull the panels out and leave them over the side of the bath to dry a little - 10 mins should do it;
• Paste a good covering of the glue/water mix on one side of your panel (I usually do the top first so the overlap is on the bottom surface) - be generous, most of it's coming off later...;
• Place the first panel onto the wing, ensuring it's accurately positioned - this is the tricky bit which requires roughly eight arms to achieve consistently!  
• Apply plenty more glue/water mix, and work it in with a soft brush (an old shaving brush is ideal!);
• Take a smooth credit card, and gently squeeze out the excess glue towards the LE, TE and tip. How much you do this is up to you - leaving more glue in increases weight, but improves ding resistance;
• Wipe off any excess white glue at the tips and panel edges;
• Now fold the excess paper around the tips and LE (leave it dangling aft of the TE). Snip the paper with scissors as required you need it to go round a compound curve at the tip;
• Re-wet the overlaps with glue mix and scrape off as above (if required);
• Now flip the panel over and do the other side, except you don't need to take the paper round the LE or tip - as long as it has overlaps with the paper from the other side by 1cm or so, you should be fine. Work plenty of glue into that overlap area though!
• Leave it to dry overnight in the vertical position (propped up in the drained out bath is fine, if your other half will allow it!). The paper will shrink dramatically, but won't warp the wing because you did both sides together... didn't you?!!  
• The finished wing can be primed and painted, or just cover with an iron on film - all films work better on this surface than naked foam or wood, since it's deeply impregnated with PVA which is reactivated by the heat of the iron. This effect does fade over time though - I recommend covering your wings within a week of brown papering them.

Photos of my first attempt (on an HP60) are available here... that was somewhat unfortunate, as I later had to remove the paper (it broke our EPP60 racing rules  ). I've done this subsequently though over EPP and blue foam - both were a great success. Weight increase for the 60" HP60 was ~75g (2.6oz), and the torsional strength it gives is amazing considering how low tech the materials are, though it's fairly weak in compression.

Edited September 4 by MattyB

[Futura57]

I think it's fair to say there is the 'wet camp' and the 'dry camp'. The former works for me because I treat the damp brown paper like thick tissue. I handle it with care, use good quality paper and work it while it can stretch a little, but before it gets saturated and starts to fall to pieces. Getting air bubbles out by wiping over with a damp sponge cloth works for me. I may try a credit card next time. The dryer approach with thicker PVA just didn't work for me, especially on double curvature surfaces. I found that small localised areas got wetter, sooner, and I got too many air bubbles. To treat persistent bubbles you have to do an 'H' cut and squeeze in more PVA. Too much hassle for me. And, applying heat with an iron, as some advocate, just made a mess. Horses for courses. Try different approaches and see what works for you.

[Edgeflyer]

I once made a paper mache "shell" by applying strips of paper soaked in wall paper paste to a small balloon. After patiently building up the thickness to about 2 mm all over the top half of the mould and waiting a week or two for it to dry thoroughly in the airing cupboard , it was like wood and could be sanded.

[David Elam]

There's a reason we used to call Matty the 'Paper Boy'

[Piers Bowlan]

The main point I would add is that not all brown paper was born equal, use good quality paper that has a grain. Some is made from recycled paper and tends to fall apart when wet, especially if you try and stretch it. 

Also, personally I dilute the PVA aboutt 20% or when it has the consistency of single cream but it depend on the PVA. Economy PVA is very thin (rubbish) and I wouldn’t use it on anything let alone dilute it!

 

I give the brown paper treatment to reinforced polystyrene (EPS) wings. I wet th brown paper under the tap then apply glue with a brush on a pasting table. If there is an air bubble I push it to the edge with a sponge. I ensure the edges of the paper is stuck down which sometimes might require a little more glue. Ensure both sides are covered before placing in the airing cupboard to dry overnight. I apply another coat of PVA to seal it. which gives a very good surface to take paint when dry.

 

[leccyflyer]

Have only used the technique once, but was very impressed with the ease of use and finished results of the method shown in Ron's videos, using Hobbycraft brown paper and Jewson's PVA. It wasn't anywhere near as messy as I'd expected. Purely in terms of logistics, the wet paper method couldn't work for me -as I don't have a bathtub or any form of plumbed water supply in my workshop, which is where I cover my models.

[Futura57]

I use a 500ml hand water spray, sold for indoor plants, to wet my brown paper a little. I don't soak it as such.

[Engine Doctor]

15 hours ago, Ron Gray said:

Sorry ED but I disagree. The brown paper should not get too wet, usually as a result of overthinning the PVA and can result in the paper just falling apart when you try and apply it. Secondly there is no need to apply a thin coat to the model before applying the paper. If you use good quality PVA (although my one of choice is Jewson's as can be seen in my vids) thinned no more than 5% then it will not soak straight through the brown paper and when smoothed out on untreated surfaces can be worked into curves without tearing resulting in a largely bubble free surfaces.

Hi  Ron we will just have to dissagree on this topic . Defining "too wet " is a bit hard to describe but anyone who has hung wallpaper will know exactly what is right for them . A  completely bubble free surace is what we are after. Pehaps your using a  different type of paper to me ? A good quality PVA thinned 10% ish works for me. If paper is too stiff and dry  it will not adopt a shape or sink into internal compound curves without a lot of rubbing etc . It needs to be wet  and soft  , not wet as in falling apart but wet through enough to take a shape . It can then be moulded around odd shapes like wing rootes and tips. Extreme shapes will need a few pieces to cover as brown paper has its limits. Overstretching can split the paper but is easily fixed with a patch then sanded down when fully dry . When its dries it shrinks tight and sets into these shapes adding  strength / stiffness to the underlying structure.

As Matty says be sure to cover both sides so it doenst warp or distort wings etc as it dries and shrinks.

Piers makes a very important point in that not all brown paper is equal and some is just rubbish. I try to use parcel wrapping paper the type that has a sort of grain running along its length , bought from local post office. One side is a bit shiny . If both sides are completely matt then it likely a recycled  rubbish product that falls apart easily when wet.

One thing not mentioned was priming the surface to be covered. I usually give balsa sheet a light coat or two of thinned dope to lightly seal the surface to help prevent absorbtion of water and warping/buckling of sheeting. 

As always one persons method is not always right for another but we get there.

[Edgeflyer]

Thanks to all for the contributions based on wealths if experience. A couple of questions if I may: 1) Will all of the panel joins tend to show through a doped nylon covering, or how much sanding was required to prevent this? 2) Has anyone tried using white paper? Either the kind sold for lining walls prior to papering (you can get light grades) or the kind chip shops use which they call white newspaper? 3) If I'm doing on nylon afterwards can I dispense with brushing PVA on top of the dried and sanded brown paper?

Thanks 

Edited September 5 by Edgeflyer
Add a detail

[GrumpyGnome]

Ummmmm................. why do you want to cover it twice?

[Edgeflyer]

I'm considering the paper method for my Wots Wot restoration not for an all sheet or foam wing. (There is another somewhat loopy thread on my oil soaked delaminated plywood somewhere).

 

 

 

 

The original ARTF model was fuel soaked and after stripping and rebuilding all the affected areas the resulting airframe looked horribly discoloured but sound. "Why do you want to cover it twice?". Reasonable question! Why did I want to do it at all? I sometimes ask myself. Actually I've already covered it twice, using first light glass cloth and water based pu then removing all the bits of glasscloth where holes should be! Followed by doped nylon. ( Why?  It was an ARTF! I had a brand new ARTF wots wot in the loft! Which I then sold!). I just don't particularly like plastic film although I use it lots and have umpteen models covered this way. But I wasn't happy with the result so shelved it.

Now I'm stripping back my previous coloured dope and some of the nylon where necessary to do a full and hopefully nice recover (maybe with brown paper to give a clean base first). The final attempt will be using 2 colours of home dyed nylon from a parachute sent for repacking in 1969 !

I don't expect anyone to understand or rationalise what I'm doing or care what anyone else thinks of my hobby.

But I do appreciate the help from those who have  given advice on the papering technique. If I don't use it this time I will in future no doubt.

[leccyflyer]

If it's an open structure - which that post implies it is and the picture in the linked thread shows, covering it in brown paper isn't going to work - it needs a solid substrate to be stuck to, with no open structure.

[Ron Gray]

As has already been said, different strokes for different folks. The method I finally settled on is as shown in my videos and is also the one Richard Wills uses, it uses the cheapest brown paper, doesn’t use pre soaking, priming the surface, drying in airing cupboards and guess what, it works really well even on complex curves.

 

Like I say, each to his or her own but I do prefer the KISS principle.

Edited September 5 by Ron Gray