Poly C

[andy watson]

In my previous posts I was asking questions about covering using Poly C.  It became clear that very few people have used it, and because people are unfamiliar with it they are shying away from using it.

 

I am planning to use it on my stuka, so I thought I would order the stuff early and do some testing.  Because I am nice, I thought I would share the results and impressions of using the stuff.

 

I took a scrap sheet of 3/32" balsa sheet.  This is the thickness of sheeting used on my stuka, so seemed appropriate.  I then cut a 6"*4" piece of 0.6oz/m2 glass cloth and draped it over the sheet.  The sheet was about 3" wide, so there was a 1/2" overlap- similar to the method given in the instructions.

 

The first coat was painted on.  It's fair to say that this stuff really does go a long way.  The instructions are clear that thin layers should be used, and so I was careful not to lay it on too thick.  In the end I used only the lightest touch of the tips of the bristles to apply the poly C, and it took 2 of these to coat the cloth.  It was dry within the 20 minutes advised, and I have added about another 4/5 coats.  The instructions talk about 8-10 coats, so I will add more tomorrow. 

 

 

The most impressive thing about this stuff is I did the testing in the front room, during a film with the rest of the family.  No smell, no mess, nothing.  It's also incredibly easy to apply, the only area of awkwardness is making sure you don't overload the brush to get the coats thin.  I also think it will be awkward to do larger areas and know where I have done, as the thin layers are difficult to see (a bit like putting a second white coat on a ceiling!).

 

What wasn't so good?  The surface has gone on very smoothly, but there seem to be a small lumps or bits on the surface.  They look like they will easily sand out, but I don't know what caused them as the brush was brand new.  I think this shows the importance of doing this in a clean dust free environment.  Bear in mind I am half way through, but so far it isn't very tough.  Its easy to dent with a thumbnail- although not as easy as balsa.  I think it's fair to put the rest of the coats on before commenting too much. 

 

Just as a final note, it is vitally important to seal the balsa before using the poly C.  If you think it might not be important, or you might not bother, well this was a flat sheet before I put on the cloth and a single coat of poly C. 

 

That kind of warpage will ruin any wing, fuselage anything.  SEAL THE WOOD!

 

More to follow tomorrow when I add the remaining coats and give it a couple of days to really dry well.

 

Anyone else with experience of using poly C please contribute.

[James Mark]

Hello Andy

 

I have just tried out poly c on the ailerons of my airsail chipmunk. I decided to use it after reading the excellent revue in the chipmunk forums, posted by Richard Duvall on this web site .

 

It seems to be as good as they say it is, no smell, easy to apply.lightweigh. I do not have any experiance of glassing at all, but the small bit I did with poly c has really impressed me and I intend to cover all the sheeted surfaces on my chipmunk with it.  You can't use plastic film on a chipmunk!

 

By the way you must seal the wood as it is water based!

[Tim Mackey]

I have extolled the virtues of this stuff several times - I use it on all my foamies with lightweight tissue and it makes a nice tough lightweight skin which takes paint well.

Heres the hawk on todays maiden - 3 coats with one layer of tissue, followed by 2 / 3 coats of acrylic brushed paint.

[iawnski]

and how did she go tell us

[Tim Mackey]

Very well actually kev. I will be doing a short blog on the build and flying in the next day or two, and John Bowman has promised to put a few more of his excellent pictures on his gallery soon.

Right, back on topic.

[Myron Beaumont]

Timbo

I have lost the thread of your thread on your Hawk ! Can you tell me if it is powered or a sloper .The reason I ask is that I am thinking of making my Haoye Hawk into a sloper 'cos I've never tried it ? I suppose I blank off the intakes and then do what you have explained what you've done on yours in this thread to toughen it up for places like the Great Orme  

[Tim Mackey]

The one above is my new EDF version - maidened today.

I will see if I can find the one about the PSS model  that I use on the slope

Here ya go....

Edited By Timbo - Moderator on 01/06/2009 22:46:54

[Erfolg]

I have just finished rebuiding, my flying wing, on which i have used Wickes varnish.

 

I will be posting some pictures shortly, of some aspects of the rebuild. The results appear to be very similar to Poly C, in all aspects. But at a fraction of the cost. You can buy it around the corner. I have also used it on oak flooring, one of the intended purposes. It is worth considering.

 

A fellow club member swears (kindly0 by B&Qs version, looks fine to me.

 

Erffolg

[andy watson]

Bah, flippin' mods are the worst for taking a thread of topic! 

 

Seriously though, RC world say it can be applied directly onto wood (obviously after YOU SEAL THE WOOD).  Presumeably this would be the case for foam models too- so what does the tissue do?  I assume the glass cloth lends a significant amount of structural strength, but I can't see tissue doing the same.  Does it offer a smoother surface for the poly c?

 

One other question is about how to do complex curves- do you cut slits in the tissue, or do you use smaller pieces as patches.

 

The remaining coats are going on tonight.

[Tim Mackey]

I put one coat of POLY-C straight onto lightly sanded foam which was already "painted" (rather poorly ). I then applied the tissue, cutting into pieces for awkward shapes and panel lines etc with another coat of PC. Then sanded it all lightly, which left a nice hard shell like surface. I then applied another coat of PolyC, sanded again and painted with acrylics. The tissue certainly helps to get a slightly smoother and stronger surface.

Its never going to be like glasscloth /resin, but believe me, it does help the dingproofing of what is otherwise a very flimsy and poor foam surface.

[Erfolg]

As promised the equivalent Wickes, the budget system

 

This is a image of the fuz before covering, rubbed down. The canopy has been painted with translucent, yellow ink.

 

A picture painted with the aforesaid ink, gives a finish similar to the old free flighters, tissue covered. If a in your face bling type colour is required, simply use solid pigmented ink

I have now glassed clothed the fus, with the floor varnish

Finally the finished product after trimming and two more coats

The final finish is purely dependant on the intial preparation, I rersonally take the view, that the model needs to be durable,quick in the doing stages and cheap enough that not to many tears are shed when it crashes. The marks from my marking out are still visible, as I am not to concerned with this model, as the Holzflugel 3 spun in perfectly flat from about 80 or so feet, destroying the original body. Versions 1,2, and 3 never sdisplayed this characteristic.

 

Erfolg

[Gemma Jane]

I've also been doing a little experimentation with Poly C on foam. One comment I read on a different thread was that it was not possible to maintain existing panel lines when covering. I found with a very inexpensive  small stiff nylon brush (the throw away sort often used in glassing)  it was quite easy to get lightweight tissue to conform to existing panel lines simply by 'pushing' the tissue into them, also good for smaller curves. I did find the tissue  tended to wrinkle a little, but found that simply stretching the tissue as I worked then reworking with the brush now and again before the Poly C dried was enough to remove them. Pleased with the result so far but also interested in the cheaper alternatives. I would recommend people try it out with a stiff brush, it is much easier to get a difficult surface covered as the tissue softens it can be encouraged to fit quite difficult shapes with a little light pressure that would be lost with a soft brush.

Edited By Gemma Fairchild on 02/06/2009 13:37:08

[Erfolg]

I have used the floor varnish on Blue Foam, there is no more a problem with foam than with wood. Blue foam does require a lttle more preparation though, as if the glass cloth is laid directly onto the sanded foam, I found that it was not as smooth as I thought. It just required an intial coat of varnish, smoothed back to remove the bobbling/puckering, I guess from the water being taken up in the structure. Then cover as usual.

 

It is a comman phenomen for plastics to take up water, some more than others.

 

When Holzflugel-3 went in, the foam remained intact with the cloth. What did break was the balsa and ply. The glass cloth was firmly stuck to the surfaces, taking the wood as a veneer, in some places. Varnish is remarkably tenasious and durable.

 

The down side is that, if deposited in a single thick layer as accumulates at corners, it is rubbery, a little like PVA. Although it does seem to harden with time, 2-3 days. 

 

Totally odour free, 1 hour touch dry, recommends 4 hrs for a recoat. I have recoated after 1 hr does not seem to make any difference.

 

 

[Richard Duvall]

As mentioned by James above, I have used Poly-C on my Chipmunk and found it very user freindly - no smell, no sticky mess, brushes wash out in water. I am a novice builder so have nothing to compare it against.  I used it with the lightest glass cloth I could find and found that it took around 5 coats to achieve a good finish. I also found it possible to cover complex surfaces, like the fuselage, in sections; the joins were quickly lost with a light sanding.  I read somewhere that it has greater adhesion qualities that Wickes (or B&Q) varnish and a half litre bottle (approx £10) did the whole of my Chipmunk.

[Former Member]

[This posting has been removed]

[Erfolg]

Non of these varnishes are solvent based.

 

Wickes is a water based Acrylic, with similar (what ever that realy means) characteristics to polyurethane solvent.

 

Some time ago I rea, possibly in a USA mag, what poly C actual is. I do remember that it is a floor finish, supplied in very large quantaties by the manufacturer to the "Trade". At that time it was repackaged, into smaller containers for the model trade. I think it is at this point it aquires the trade mark, "Poly C". I have looked through back issues to try and locate the mag and artical, to date with no sucess.

 

It was from the artical, that I came to try Wickes stuff, as it was left over from a bespoke quarter turn stairs that I made for a cottage.

 

As for peel strength, it is extremely high, the interface fibres failing, rather than the cloth to substrate, varnish failure. As for abrasion resistance, this is also high, as it is a floor finishing product as well as general varnish.

 

Is it as good as Poly C, I have not got a clue. Yet if it is the difference between say HMG to Pages dope or Resin W to Bowmens PVA, I would guess it matters little.

 

I put Wickes, B&Q forword for consideration on the basis, that some of these may come easier to hand. Will I use Poly C?, if it comes to hand and the price is right why not. I would use "Johnstones WB floor varnish" to, if it comes to hand.

 

I recently bought some Polyurethane Gorrilla adhesive in the local timber yard, guess what, seems to be pretty much the same stuff as Henkel "ELCH".

 

There is one adhesive that does appear to be very different and that is Stablit Express, which i also think is a Henkel product. Most other generic varnishes, glues, etc of a class, seem to be pretty much the same, in my opinion

 

Sorry to upset the apple cart

 

Erfolg.

[Tim Mackey]

http://www.rcworld.co.uk/polyc.htm

[Former Member]

[This posting has been removed]

[andy watson]

Well the testing was finished yesterday.

 

The remaining coats went on as smoothly as the earlier ones.  After a day to dry the final surface is tough, but by no means impervious to knocks.  I guess I would describe it as ding resistant rather than ding proof.  It seemed pretty good against bumps, less resistant against scratches (including fingernails.  Glassing is aparantly tougher.

 

The bond to the wood seems strong.  It can be torn off, but you have to work at it.

 

One thing I noticed was the quality of the finish.  It seemed to be very good after the first 4/5 coats, but I have noticed the final finish isn't so good.  The reason for this isn't down to the poly C, but the brush.  I didn't clean it properly, and just cut the bristles short- unfortunately I think this made the brush a bit stiff.  This means I would suggest a good quality and quite soft brush for best results.  According to the literature I think I could repair this with a light sand and a couple of other coats.  The way the glass cloth weave was covered means I think these claims will be true.  A light, fine sanding should make the surface suitable for painting.  8-10 coats are lighter than a single coat of epoxy.

 

I notice Phil is planning some tests- I would advise caution.  The bottles seem expensive(ish) at a tenner for 500ml.  The poly C does seem to go a very long way.  Richard did a 1750mm span plane with a single bottle.  I bought 2 because I wanted to be on the safe side.  If you are talking about a normal sized plane, how much money would you save on a single bottle equivalent?  Maybe a £5 at absolute best.  The risk is using it on a plane and it failing to meet the standard- maybe over time.

 

For me this is a clear recommendation if you are wary about weight, or if you don't want to risk poor glassing on a newly built model.

[Former Member]

[This posting has been removed]

[Erfolg]

Phil

 

It seems I am wrong in that Wickes and Poly C is essentially the same stuff.

 

I am still unable to find the original artical, that a reference was made to Poly C. Yet a conversation on the telephone with a mate, who is a floor fitter revealed that approx. 2 years ago, I was after a sample of a product made by Ronseal.

 

The product at that time cost approx £55 per 5l plastic container. Apparently it was called "Contractor Quick Cure". At that time he had not used. So there was no left overs available. He says that the range has widened now, For heavy traffic areas you can buy an hardener, or a high traffic version. It is still dear.

 

He has used the other products types as per the one I use. In his opinion, at the user level differences are minimal. But his intrest is along the lines. Short time between coats, minimal coats, good finish without a massive investment in cutting back, both at the prep and recoat and finally the finish coat. As to hardness, wear resistance etc, his view that is really down to the specifier, but thinks from his limited experience thay are all fit for domestic floors and some commercial applications. The added bonus therare no ventillation, dealing with waste issues that the solvent based systems present.

 

As I know little of chemistry, I then got onto a Phd. chemist i know. I asked what is a Alkyld and a Polyurethane. I quickly recognised this was not a question that I should have asked. It seems that Alklyds are from a group reffered to as Alcholoids, which are apparently derived from plants. Apparently chemists recognise something in the structure of these groups, apparently another product developed by the infamous AG Farben, although he then wittered an about BASF doing some inprovements. Urathanes are, well they are rectited with water................................. At this point I had lost the plot, and wondered if it was time for toast

 

Apparently both products can call themselves Resins, for some technical reason. I asked about this, as i wanted something that cut back better, something akin to epoxy. I was told that the properties were not just dependant on the basic chemistry, but how the chemist manipulated the chemistry to enhance particular properties. Not in being a resin, which can be like treakle. From this I deduced that characteristics of the products, have a lot to do with what the manufacturer thinks the user wants, not just the basic chemistry.

 

I then stupidly asked which is the better. The answer is, "Well that depends", "what do yo want","what do you need" "can the the chemistry deliver" Ohhh "of course that all makes the assumption, you have got your wish list right, and can recognise sucess or disappointment"

 

So they are different, apparently Poly C, could well be Ronseal WB.

 

I was finally asked are you happy with the results you get? Well yes, quite entusastic actually. So what is wrong? I want something better for less money. Why better, and what does better mean in a way that you can measure? As for cost, you are just mean Erfolg.

 

Erfolg   

[John Horsfield]

Hi Guys, Ive read this post with great interest as I have an old fuselage in need of recovering.

Im thinking of going down the polyc or wickes varnish route (probably wickes varnish to reduce costs) as I have a large ammount of thin lightweight glass cloth to hand. 

I do have a couple of questions. What do I need to use to seal the wood before applying the polyc? Erflog mentions that the wickes varnish is acrylic based, has anyone tried mixing acrylic paint to it to give a coloured finish? If thats not possible, do you think that after the first few layers of poly c a painted layer could be applied and then finished with a final coat of polyc to make it fuel proof?

Any further advise would be greatly received!

Cheers John

[Former Member]

[This posting has been removed]

[Erfolg]

John

 

The Wickes WB is completly translucent when applied.

 

I just paint, the wood, with a suitable paint, I have used Artists Inks, both with, Varnish and Z-Epoxy laminating resin. When applied to the wood the finish is dead flat, after the resining process the colours become vibrant. I believe a similar or the same approach is taken with car metalic finishes.

 

If pigmenting the varnish, I would be looking for a water compitable  pigment., which is concentrated I doubt if the type used in laying GF are suitable, but they are probably worth a try, as a  test.

 

I believe we must recognise that a lot of our modeling materials are targeted at the mass or manufacturing markets. I can only think of Balsa Cement and some ethanol fuels which are specially formulated for us. The rest, wood glues, electronic components, epoxy, polyester resins, Foams (blue, expanded polystyrene etc) are often re-packaged for us. 

[John Horsfield]

Okay, I think i'll go down the ink route on some scrap wood to see if Im happy with the finish. When you say ink with varnish (what type?) or z-epoxy (which Ive never heard of!), is this to seal the wood before applying the polyc?