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Old Feb 21, 2008, 05:59 AM
The Revegetator
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Melbourne Australia
Joined Jun 2006
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Mini-HowTo
Covering with Tissue and WBPU

I like foam for many reasons but to me it looks cheap and nasty and spoils the look of a model. Although it is very easy to build a foam kit, the fact is that foam is damaged very easily. If you have built a foam kit you will know how easy it is to mark the surface of your model before you even get to fly it.

So what can we do to protect and give a nice finish to our foam models? One of the answers is to cover them with tissue and WBPU, or Water Based Polyurethane. So what on earth is WBPU? The stuff I use is a floor sealer and it is very easy and quite safe to use compared to some of the epoxy products. I use my fingers to smooth the tissue during application and when it's dry it peels off them like a layer of skin which is kind of fun .

I can't take credit for this method of covering and I would like everyone to know that my inspiration to use the method came from Matt Haltons build thread for his Ultrafly P-51D Mustang here
http://www.rcgroups.com/forums/showthread.php?t=536128
His model is a great example of what can be done with a foamy.

This is what you will need for the job:

1 can of WBPU. A 1 litre can is enough to cover 4 to 5 small to medium size models.

Enough Silkspan (or Japanese tissue. Google it if you want to know more about it) to cover your model. Silkspan comes in different weights. I use the thickest I can get.

A paint brush about 2.5 cm wide.

Around 120 and 320 grit sandpaper.

Lightweight spac filler. I use NHP Micro-Fill Super Light Model Filler available at hobby shops.

A pair of sharp scissors.



So when I get a new foam kit here is what I do.

First I sand all the bumps and raised bits of foam lightly with 120 grit sandpaper until the surface is smooth. I then fill any low areas with the filler and sand it smooth when dry. When you are happy with the surface preparation it is time to start covering.

Cut a piece of Silkspan big enough to cover and overlap the piece you are about to cover. Make it too big so you can trim it back once you start to apply the WBPU.

Wet your brush and start brushing the WBPU on the Silkspan so it soaks through and sticks the Silkspan to the foam. It is possible to remove the tissue from the model if you need to until the tissue is nearly dry. Start from the middle and don't wet the edges yet. Trim around the model part so the Silkspan will overlap when you cover the other side. If you get the Silkspan wet it is almost impossible to cut. When covering compound curves you will need to cut or tear the tissue so it will conform to the surface of the model. You will find that sometimes it is easier to use small patches of tissue than large ones, but I always try to use the largest pieces I can manage. Typically I can do the bottom of a one-piece wing with one piece of tissue and the top with two. The fuselage can usually be done with two pieces, one for each side. If it is too hard use smaller pieces of tissue. You will find that the tissue will stretch a bit once wet and that you can smooth out most of the wrinkles and bubbles with your fingers. If the tissue doesn't conform to panel lines etc, run your finger or fingernail along the lines so they show through the tissue.

When all the covered pieces are dry, sand them lightly with the 120 grit sandpaper until it feels smooth. Concentrate on smoothing down any wrinkles, areas where the tissue overlaps and areas like wingtips where you had to cut or tear the tissue to make it conform. This is usually where the tissue overlaps so you can sand it down until the cut edges of the tissue disappear. Be careful not to sand through the tissue.

Once you are satisfied that you have sanded all the parts so there are no edges of tissue visible and that the surfaces are nice and smooth, brush a very thin coat of WBPU onto the pieces. It will dry very quickly this time. Then sand with the 320 grit sandpaper and then brush another very thin coat of WBPU. Sand and coat until you have a nice smooth surface.
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Last edited by Chris F; Feb 23, 2008 at 04:57 PM.
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Old Feb 21, 2008, 07:50 AM
<- Balsa flies better ->
wolw's Avatar
Gustafs, Sweden
Joined Feb 2006
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Great guide Chris !

It sure looks simple, but like everything else it takes practice to make it look good, you're the master Chris

Can't wait to get something to try it out on. I've thought of taking the tape off the FII. Both to try the tissue and to try using an airbrush

Right now I'm about to clear out the garage and move my work shop over there. It will be larger and I can do more things simultaneously and I'll have running water to clean airbrushes (and make coffee ) etc.

Peter
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Old Feb 21, 2008, 01:52 PM
The Revegetator
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Melbourne Australia
Joined Jun 2006
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Hi Peter,

It is so easy I did a good job on the first model I tried it on, the FW-190. In fact it turned out better than the P-51D but as you know that was crashed badly a number of times before it was painted.

The thing I didn't mention about this method is that it takes a long time, longer than any other covering method I have tried but I think it is worth it.

So you have grown out of your workshop already? It looks big enough in the photos to me but I'm not a coffee drinker .

So what foam model will you get? Most of them are a bit small for your liking aren't they? What about that E-Starter you have?

Did you try out that slope you mentioned a while ago?
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Old Feb 21, 2008, 03:12 PM
<- Balsa flies better ->
wolw's Avatar
Gustafs, Sweden
Joined Feb 2006
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The work shop is fine as long as you're not building or trimming larger gliders like the Svist (2.7m), you have to bend down to go under the wing if you want to walk around it.

The garage is basically unused, its become more of a storage (of junk) than a garage (I put up a couple of pictures in my blog) Helena wanted to put the exercise bike in the old work shop and work out there

The E-starter will be perfect to practise on, it's basically new. Helena refused to try it and I thought it was boring and it's uncovered unlike the FII.

Haven't had time to try the slope yet, weather must cooperate, I have to be off and I have to bring a friend of mine to show me where it is

Peter
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Old Feb 26, 2008, 09:13 AM
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USA, WV, Charles Town
Joined Mar 2005
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Excellent tutorial; thanks for the info!

I will be trying this method when I build the GWS P-51 kit I have sitting in the attic.

So many planes I want to build... so little time... and even less money.
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Old Feb 26, 2008, 01:51 PM
The Revegetator
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Melbourne Australia
Joined Jun 2006
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Hi aeronuts,

Thanks, I'm glad you like it. I find the fuselage on the GWS P-51D a but weak if you intend belly landing like mine. I have reinforced inside the sides of the fuselage with balsa sheet, especially at the LE and TE of the wing which seem to break even if the prop digs into the ground on landing. I only land in long grass now. The battery area also needed a simple mod as it didn't fit any of my 3S packs.

Good luck with yours.

Post some pics here when you have finished.
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Old Feb 26, 2008, 08:35 PM
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Quote:
Originally Posted by Chris F
Hi aeronuts,

Thanks, I'm glad you like it. I find the fuselage on the GWS P-51D a but weak if you intend belly landing like mine. I have reinforced inside the sides of the fuselage with balsa sheet, especially at the LE and TE of the wing which seem to break even if the prop digs into the ground on landing. I only land in long grass now. The battery area also needed a simple mod as it didn't fit any of my 3S packs.

Good luck with yours.

Post some pics here when you have finished.
Thanks for the info. It's good to know this stuff BEFORE you start building. Just for clarification on the balsa reinforcement, are you also recommending reinforcement of the LE and TE of the wing itself, or where the LE and TE of the wing joins the fuselage.
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Old Feb 27, 2008, 12:44 AM
The Revegetator
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Melbourne Australia
Joined Jun 2006
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Quote:
Originally Posted by aeronuts
Thanks for the info. It's good to know this stuff BEFORE you start building. Just for clarification on the balsa reinforcement, are you also recommending reinforcement of the LE and TE of the wing itself, or where the LE and TE of the wing joins the fuselage.
Just the inside of the fuse as shown in the photo.
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Old Jun 13, 2008, 12:46 PM
Fly it like U stole it
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Champaign, Il
Joined Mar 2008
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Great thread! I am trying this for the first time and I was amazed at how easy it was to get a glass like finish!
I have a quick ?, I am getting ready to paint and then seal it with gloss WBPU( I am going for a very shiny glossy finish, non warbird). Will I need to wet sand or dry sand the last coat or do you think it will be ok to just let nature cure it? or should the last coat be some other kind of sealer?
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Old Jun 13, 2008, 02:55 PM
The Revegetator
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Melbourne Australia
Joined Jun 2006
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Thanks Pickle.

I used a can of gloss clear acrylic over the enamel paint I sprayed on my GWS P-51D and it turned out looking good. If you used gloss paints I think you will get a smoother finish. My GWS FW-190 has thinned matt acrylic paint and the texture of the tissue still shows through, but that's OK because it has a satin finish anyway. If you have a glass like finish after painting I think it will be OK to give it a spray with either gloss WBPU or clear acrylic. Maybe test it on another surface first to make sure. Post your results here, it would be great to see.

I'm about to start another foam covering job, this time a GWS P-40.
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Old Jun 13, 2008, 04:01 PM
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Phoenix, AZ
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Chris, if you wouldn't mid posting pics of the P-40, that would be great. I have the GWS P-40 as one of my next projects and would love to see this technique on it. Thanks for sharing.

D-Rock
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Old Jun 13, 2008, 09:47 PM
Fly it like U stole it
Pickle72's Avatar
Champaign, Il
Joined Mar 2008
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I just found the spray can version of WBPU tonight at the store before I read your reply and of course I didn't get it
So next trip in town I will pick some up and try that out.
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Old Jun 13, 2008, 09:51 PM
The Revegetator
Chris F's Avatar
Melbourne Australia
Joined Jun 2006
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Quote:
Originally Posted by D-Rock
Chris, if you wouldn't mid posting pics of the P-40, that would be great. I have the GWS P-40 as one of my next projects and would love to see this technique on it. Thanks for sharing.

D-Rock
I'll do a build thread here in my blog.
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Old Jun 13, 2008, 09:54 PM
The Revegetator
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Melbourne Australia
Joined Jun 2006
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Quote:
Originally Posted by Pickle72
I just found the spray can version of WBPU tonight at the store before I read your reply and of course I didn't get it
So next trip in town I will pick some up and try that out.
I'm sure that or the clear acrylic in a can will work OK.
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Old Jun 13, 2008, 10:17 PM
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Thanks Chris, I'll be sure to look for it
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