andrew b

Sorry to ask but I read in a post here about tissue/PVA for covering SWR. I assume that you water down the PVA a good bit and use colored tissue as the "base" for any subsequent paint, like polyurethene (house) paint airbrushed on later?

Thanks in advance

combatpigg

My Feedback: (3)

I haven't heard about that one, I thought PVA was used because nothing sticks to it as a mold release? I would think that tissue and dope is still the best way to go, as far as laying down tissue is concerned. The SWR wings rely on the shrinkage of the iron on film to add torsional rigidity, something that you don't get with a low shrink covering technique. I've noticed that the SWRs I covered with
high temp film hold there trim better than the ones covered with light weight cellophane [for example].

BMatthews

PVA remains water soluble. Also the alchohal in the fuel will also reactivate it. All in all not a great idea. I'd stick to dope for use with the tissue. But for diesels it may be OK. Also the stuff I've seen contains a green die so that you can see how much is being applied in the mold.

There's not many alternatives to dope I'm afraid. The polyurethane seems good at first but it's heavier per coat. You may be able to get away with less coats but that would need to be tested before I'd trust it.

If I found that I could not get dope or had some allergic reactions to it that forced me to look at alternatives I'd probably try using shellac as a base with a polyurethane topcoat for fuel proofing. But here again shellac will dissove from the glow fuel. But for diesels it would probably be fine. The advantages of shellac are that it dries very quickly, builds up decently fast and can be easily sanded (dry sanding only). It is still activly sold in the hardware stores around here as a sealer for house painting. It used to be widely available as a wood finishing but that's died off other than for woodworking hobbyists that still like to experment with shellac finishing and French Polishing.

vega

I have used thinned pva to stick down tissue on open frame structures, I always found it to be a bit heavy and likely to warp or raise the grain on sheeted areas. thinned dope is my weapon of choice for tissuing sheeted areas, light coat of dope on the surface and then just lay on the tissue and brush through with some more dope - non-shrinking dope if it's thin balsa and I don't want it to warp too much

cheers

Jon

scudrunner77

I'm glad I read this thread. I was experimenting with tissue and water base poly and it seemed to work pretty good but if dope is lighter maybe I will go that route on my SWR.

combatpigg

My Feedback: (3)

Dope will get you through times of no money better than money will get you through times of no dope........oops, wrong forum Dope will melt your blue foam before you have a chance to say OOPS!

andrew b

Thats them there freak brothers varmits


Thanks everyone, point taken regarding PVA. Its not a 1/2A machine, its an "A" machine, PAW 1.49 diesel powered all sheet machine. I figured with the tailfeathers on twin booms and a "pod" type fuselage, forced air cooled servo's that covering with heat shrink would be a trial, so I am going with colored tissue and dope as the foundation, followed by thinned airbrushed enamel coz with enamel it's easy to wipe off diesel "lifeblood"

KidEpoxy

Well, with the Melt-o-rama in mind, I got a lot of great ideas for finishing a plane in reply to a fuelprooffing thread I started. Maybe some info in there will help.
[link=http://www.rcuniverse.com/forum/m_4010132/tm.htm]Finishing Balsa, Cheap Fuelproofing[/link]

Jim Thomerson

I've used thinned down titebond glue and silkspan over wood and open areas. If I were going to do a foam wing, I think I would do the same initially.

indoorff

My Feedback: (2)

For attaching tissue to my tissue covered models, I ALWAYS use thinned down white glue (I think that is PVA) to attach it to the structure. After it has dried, I spray the tissue on the open structures with water to shrink it (if the model is large enough to not warp), then I dope the whole thing. I have never had anything come loose using this method, no matter how fuel soaked, and for me, it is really easy to do.

scudrunner77

Yikes... I should have know that. Thanks again!

mclintock

My Feedback: (3)

Not fuel proof, at least I asssume it cant be, but a fun cheap thing I've been experimenting with is Future floor polish as dope.
On foam, so far it's working nice, and sands great.. I was looking for a truly clear alternative to shellac for use on foam, and I think Future may be it. So far I've only tried it on cheap gift box tissue over styrofoam to try to get a texture free surface for painting, works well so far.

Nitrate dope, lacquer, and shellac all have the cool ability to be totally re-desolved by their respective solvents no matter how long they have been solid, and I was looking for something foam safe and water clear with that same quality. There's a word for that, but I don't remember it.
Future is soluble in household ammonia, so it can be completely removed without harming foam at all, , unlike something like Polycrylic. PVA works too, but you gotta mix it with water- misery!, and I've never really liked to sand anything with PVA or aliphatic resin on it..
Future works straight out of the bottle.. and sanding the tissue with 600 works fine.
Static modelers have been exploiting Future for years.

Again, usless for this thread because of the not-fuel proof assumption. Maybe on a diesel it would be ok?

eroc144

My Feedback: (1)

Glad to see that I'm not the only one who remembers the Freaks Bros...

EG

Andrew

Clint -

I've been reading a bit about using Future, but more for dipping canopies to give a clearcoat and hide scratches. Does it add much weight? If it's applied with tissue over foam, does it seal well enough so you can use paint that might dissolve foam? Since it's a wax, has your paint stuck pretty well? The world wants to know (well, at least I do).

KidEpoxy

I thought Future/Mop&Glow spray floor stuff was Acrylic ergo fuel proof.... IIR, read that somewheres

dunno, haven't tried it

mclintock

My Feedback: (3)

I futured some tissue to a big block of styrofoam, to run some tests..

The coveted grail of having a sealer to protect the foam from the solvents of lacquer and dope is still out of reach- well as far as the Future goes.. I suppose epoxy or real polyurethane may work..
I put two coats of future on the tissue, let that dry then sprayed some lacquer on it. Munch -ola, the solvents in the lacquer still get to the foam and reduce it.[:@] But that was only two coats, with real dope it takes way more than two coats to seal, so probably not a fair test.

I tried last night some krylon h2o, which is just latex paint in a spray can, and it went on fine and sticks as good as it does on anything else. Also brushed on some kiltz 2 latex primer, that works great, and some latex interior gloss trim paint.

My fave for this one test is the kiltz 2 primer, it dried fast and flat with no brush strokes and hid all foam bead artifacts with one light coat.

The latex paints stick perfectly, the Future seems to help adhesion if anything. I don't think the stuff is a wax, rather it's more like a clear acrylic paint, whatever that means.

I covered a wing on a foam free flight cox electric toy with some 1/2 oz silk, and it was light, and the silk stayed put.. My scale is not good enough for such a small area to figure out the weight gain of just each coat of future, but it was not much, it did turn out to weigh less than the other wing that I covered with the same silk and polycrylic. To be fair, polycrylic fills better, so that means there are probably more solids there; by the time the same degree of filling was done with coats of future, the weights would probably be the same.
I figure any clear solid, be it nitrocellulose, lacquer, acrylic or epoxy is going to weigh close to the same thing for a given volume of cured material.

Using that cheap box tissue does not seem to be the way to go, however; it has less than zero wet strength, so it must be put on with denatured alchohol, and after the future and painting, it's still way way too easy to ding the surface of the foam.

My next test is to see if dings in the future/tissue can be brought out with a covering iron.. like the old ace wing/econocote days.

It's worth buying some future, because if nothing else, it's also a floor wax! I like how it reminds me of real dope, the way I can use my fingers as the future starts to dry to pull and smooth the material, just like 'real' dope. I also found it mixes fine with denatured alcohol, for sticking it down on solid areas. Smells better than thinnning it with ammonia! Sands just fine.
Like nitrate dope, you dont have to clean your paintbrush between coats, the hardened brush will come back to life once it's stirred around in more liquid future.

It is water proof.

I put some 25 percent nitro fuel on a box I had brushed future onto, and it did mar the sheen, but I may have not let the future dry long enough to be a real test.

andrew b

Well I went with heavyweight tissue and nitrate dope, so far I have covered the full length hatch and the strip ailerons. It all seems to go on nice and easy, overlaps just dissapear with a few brush strokes, gonna leave them a couple of days and then try some fine paper to get a smooth finish before the enamel. I also bought a tin of poly varnish from the 99 cent store and slopped some of that into the tank bay and the firewall, thats getting the fan blowing over it all night to send it off and I can start covering the fuse in the morning.

Getting the tissue was quite difficult and I could only get white, the LHS had to ORDER IT!! They had dope in stock but no fuel proofer hence the yacht varnish.

mclintock

My Feedback: (3)

I love nitrate dope. I wonder if there is a source of good tissue, it seems so expensive- silk sometimes costs less if you get it from silk connection or thai silks. So far the best source I've seen so far is is easybuilt-
http://easybuiltmodels.com/ebl.htm

be sure to paint some of the dope you have on a scrap so you can test the compatibility of the enamel topcoat.

Blast, only now did I notice you were in the UK!
In that case, forget easybuilt-
http://www.freeflightsupplies.co.uk/

eroc144

My Feedback: (1)

Clint - Have you tried Sig's silkspan? Comes in 3 different weights and seems to be light and strong. I've used it on all of my planes this past year (couple of DNUs, a glider, my Zero) and have been very happy with the results. Think I paid $1/sheet for a 3'x4' sheet at RC Country Hobbies in Sacramento, CA.

EG

Andrew

I buy my silkspan from [link=http://www.brodak.com/shop.php?CategoryID=151]Brodak.[/link]

fritzke

My Feedback: (1)

Clint,
I used to "topcoat" my plastic model cars with Future when they were all done, sure made them look nice.
Water can make the stuff blush, just like dope does. It is some sort of acrylic. My mom always had it around
for the linolieum kitchen floor. I think she STILL uses it on that linolieum kitchen floor!
Never thought to use it on a model plane though. Who needs dope/Monokote/silk/Lusterkote when we have
Water based poly, Doculam, Krylon, polyester dress lining, etc etc?
(I refuse to use craft store tissue paper though, that is generally awful stuff for covering planes).
Dave

mclintock

My Feedback: (3)

I've used silkspan, and it's good stuff, it's kinda thirsty for dope though,
no problem on a .15 control line or the like.. I wonder if my LHS has any?
I wish there was a wal-mart around, so I could seek dress liner material, i may just have to order a roll of polyspan to play with..
from fai..

I stuck a piece of 3/4 oz glass cloth to my test foam block, and it sticks fine, just pour the future on and squegee it around with a credit card.. Way easier than the tissue to get flat. Also still dents the foam easily, but I tried to jab my fingernail through the glass, and it aint gonna happen! Also, the future does not mind the heat of an iron that is hot enough to re-expand the foam for dent pulling. When I cranked the iron up more than that, it did stick some.

Just another thing to play with I guess.

hogflyer

I've used Future on plastic models for years. It works great as a primer for plastics besides being a great topcote for paint and windows (but when polishing it does wear down rather quickly) - while I also take my time building and let it cure for at least one, if not two weeks before painting over, I have overcoated it in 24 hours with the new Tamyia lacquer based paints with no problems. The Tamyia lacquer paints appear to have a very mild lacquer that doesn't seem to attack the plastic like other lacquer paints. I spray it with a Badger 150 airbrush straight from the bottle at about 10 to 15 psi.

Andrew

Clint -

That's certainly true for open areas when brushed on -- if not careful, you can end up with a drop on the bottom side of the silkspan. You can avoid that aggrevation by spraying a couple of light coats -- it seems to seal the surface and block any bleedthru from following heavier coats.

When I first started using dope years ago (sounds a little strange doesn't it?), I didn't know that I needed to thin it for brushing. Most of my early planes ended up with a thick hairy hide with ridges and my fuselage sides were sometimes bowed from the shrinkage.

eroc144

My Feedback: (1)

Yeah, I always get a chuckle when talking to "non RCrs" about dope for the first time. Kinda like when I was a 10 year old and told my somewhat "stuffy" neighbor once that I'd caught a bunch of crappies while fishing. Had to pull out the encyclopedia and show her that was the real name!

... but back to the topic at hand.

I still haven't found a "great" system for the first few coats of dope over silkspan. With a brush I invariably end up using too much and it either bleeds through or gunks up and is a lot of work. With a spray gun, I have a hard time getting even coverage b/c it's hard to see where I've sprayed. Maybe using Randolphs "tinted" clear dope would solve that problem?

EG