Epp Gliders and covering

[Silent flight]

Have made a couple of these now, but the end result is not always as good as hoped for.Once you've taped the wing how does one go about making sure that there are no ridge lines that show through the shrinking solar film(or similar), and therefore get that smooth glass look, that you get on a fully laminated wing(ie one smooth level field to stick the solar film on to).
If any one can help that would be great.

[ZIPPER]

Try Goop

[GWS CHEN]

Hi friends,

EPP could be used combined with foams and balsa as EPP is far
expensive than another materials.

[BMtech]

There's lots of work in making it look good ,Sand the EPP then fill holes with Spackel(light weight filler)a light coat all over then a 2nd heavy coat all over then sand with 250 grit ,wipe down to remove dust then spray with 3m77 contact spray, then tape with straping tape, butt all edges on the tape ,iron tape down on warm to remove any wrinkles & tighten,wipe the tape down with denchered alcohol ,respray with 3m77 then cover with your top coat


Rick.

[Mark in Aus]

I went all out on an S&B ME163 Komet EPP/HD foam. I mixed 50/50 water and Metho
and then mixed that 50/50 with PVA wood glue then added some red die so i could see it on the white foam.
Painted thin wet coats onto the foam then layed sheets of tissue. The Metho just helps the water evaporate to speed up drying time.
Once dry it can be sanded smooth. It takes some doing though and my end result was not to bad but I did another Komet for a friend without the tissue and it was just as good.
If I spent more time with the tissue I guess it would be better but once the wing creases there's still wrinkles that have to be reshrunk or ironed out.
It's probably better in the end just to sand the foam as smooth as you can get it and then just cover it.
0.8mm balsa is a good option for the flat surfaces and pretty quick to do.

I never use tape and film, it's either one or the other.
Tape is quick and easy but for good finishes covering film is the go.

Here's a few pics.

[osmium_192]

2m range??? WOW beats my steraman.....

My stearman has a 80s sci fi look inside the body. ITS TOTALLY covered in Al foil.

Otherwise its a case of forced autocracy by the esc when I move away.
The esc makes noise and the receiver succumbs to orders and starts making the servos dance to the music if i am 1.5m or further from the dance floor....


Anyways, A shame about the chrome, looked so good. But the tiger look is also great.

How do you sand foams like EPP and EPS smooth, ive tried a myriad of techniques and grades of sand paper and i always end up ripping beads out of EPS. Ive even tried just lightly touching the foam and beads still fly out like its comming from the Thunderbolt in an A10 (hehehe the 30mm gatling gun).
Oh well, ill just have to fall back to balsa. Nothing beats the feel of balsa after using 2000 grit.... (just make sure you havent used that paper on metals before)

Just remember when covering to clean the surface with rubbing alcohols or even meths or shellite (DO MELT TESTS FIRST). Its alot harder to fix a peeling covering after you have covered it, since the covering also picks up the ouls and dirt.

Owen

[RussellK]

Rick, Mark - they are some sweet looking aircraft - someday I'll have the patience to try and get that kind of finish.

Owen - I use 400 or so wet and dry and make a 1/4 sheet then cut around the corners to make them round so there's no pointy corners. This seems to avoid picking up beads, but I still get the odd gouged line.

The other thing to try is the "sanding sponges" that you get from auto shops - the stiffness of the sponge stops the edges from catching on the foam.

[olmod]

have you tried wiping on with a credit card a mixture of selleys probond with 15% of acrylic wall paint? you can sand it between coats,paint whatever you like over it and its lightweight.

[osmium_192]

Thanks russelK for the tips. I was actually using all kinds of sanding tools, sand paper, sand paper against a wooden backing, sponge blocks, even old and worn out (smooth) sanding blocks.

Maybe it was just the foam i have. Its your normal light weight eps foam, with large beads with large spacing and large gaps (suggests weak interbead bonding) You can see a pic in my build thread for a vertigo (my fav bipe)
http://www.rcgroups.com/forums/showthread.php?t=463481

And i might have a look at spackle, people have pointed me towards that but i dont know what it is or what it even looks like.

Owen

[RussellK]

I think you're using considerably thinner eps sheet than I've had experience with. The last eps job I did was re-creating the nose of a F-86 Sabre EDF - in that case the walls of the fuse were reasonably thick and I had good results using fairly rough sandpaper (as low as 60 grit for rough shaping) moving up to 400 for finishing before glassing.

With thin sheets I imagine it's easier for the balls to pop loose.

For filling, I use a lightweight filler from Bunnings - comes in something that looks like a huge toothpase tube.

[osmium_192]

tooth paste.... i think thats heavy...
lol sorry.

I was sanding a spinner of eps, i think its because i was using low cost super low density EPS for insulation rather than construction grade. The beads are about 4-5mm diameter.


Owen

[RussellK]

The eps I use comes from the local fibreglass shop - I think it's used for the cores of surfboards and for floatation in boats. It's considerably less dense (bigger balls) than the eps foam used in GWS models, but as I said, with coarse paper it was manageable, although sanded eps makes a hell of a mess...

[osmium_192]

Definately use tools that are non static, or use a water sprayer in the area your sanding. Maybe before you go outside to sand, water the garden for 10 mins or so. The increased humidity will reduce the "stickness" of foam with static charges. Its also a great airconditioner. Just do this in the late afternon to reduce excesive evaporation.

Owen

[Silent flight]

Hey BMtech, sounds good, in the pic you showed , the tape goes to the spar, how did you prevent the edge of the tape showing through the final covering at the edge of the centre section and the leading edge, short of running another layer of goop and xylene over the top(who cares about weight, oh I do),I'm still not quite sure how to get a completely smooth finish before the final shrink covering/paint/what ever.............

[steve wenban]

Selleys rapid is the one to use come in a blue tub looks like a bath tub ,it has an applicator on the lid . With a water mister spray you wings with a light coat of water and apply the spackle straight from the tub ,the mositure makes it easier to spread ,something like thinned honey allow to dry sand smooth with 180 grit
spary a heavy coat of 3M77 over the top apply solar film ,However I prefer to use solartex tend to give a tougher longer lasting finished and can be paint if so desired .
My 2 cents :)
SteveW

P.S you'll know you have the right tub of spackle as soon as you pick it up because it fells like its empty

[mc71]

I have been airbrushing and covering with clear tape. It was just easier to do than buy pretty coloured tape for me. There arent many white combat planes around either.

Here is a link to some pictures I posted ages ago.

http://www.rcgroups.com/forums/showthread.php?t=346629&highlight=airbrush

Matt