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zwibelturm
08-28-2005, 07:57 PM
The beads in the foam don't look scale. How do you smooth out the finish for painting? I'v tried Model balsa fillers and DAP lightweight spakle from straight out of the jar to diluted to watery consistency and I'm still struggling.
John Harper (zwibelturm, spiraling tower)

flypaper 2
08-28-2005, 09:54 PM
Doculam, a clear stickyback film works well. I get it from Staples. Takes paint well. Can be heatshrunk like Monocote. Adds strength but also adds a bit of weight. Have done a few other planes and am about to do a GWS Zero.

zwibelturm
08-29-2005, 11:08 PM
Thanks, off to staples I go!
John

Demon-leather
12-10-2005, 03:08 PM
Nelson Lite film or Solite (same thing) works very well on foam, shrinks and adheres on foam at low temperatures, and makes even blue fan fold foam look great. I peel the plastic "onion skin" off the fan fold. It saves about 25% of the actual weight of the parts. it is replaced with the Litefilm, and that only adds about 5-6% of that weight back. SooOOOoo... You end up with an airframe that's around 20% lighter and very colorful & shiney, and will take paint fairly well if nessasary, yet protect the foam from being eaten by solvents.
Below, is a photo of My "Square Foot" 3-D plane. Even the yellow (which is about the worst to use on balsa due to it's transparency, along with white)Looks great on blue foam, due to it's consistant color. Makes a dollar airframe look like a million! In the background, you see the actual color of the foam sheet the aircraft was built with... pretty good stuff, eh? ;) The cost of a a bit over 6 ft. x 27" roll is about 9 bucks & change at Aero Micro on line. Bob

flyranger
12-10-2005, 06:59 PM
If you would rather use a paint on finish, you could follow what I am doing in the "foamies" section. I am building a watt age Sopwith Camel and finishing it with lightweight spackle thinned with water and whipped with a foam brush to something that looks like pie topping. Sand lightly with 400 grit wet/dry emory paper. Paint with hobby acrylic paint. Spray or brush with minWax water soluble Polyacrilic urethane. I'm using gloss finish. Very little weight added (this is a park flyer, can't handle weight), and the brush marks from the cheap foam brush resemble fabric at about two feet!

Boomerang
12-10-2005, 08:10 PM
I've used brown wrapping paper over foam, applied with thinned PVA glue & it works a treat for what I consider mormal size models. A friend recently built an electric twin Caribou carved from foam & covered it in lightweight tissue from the model shop, again applied with thinned PVA glue, lighter than the wrapping paper but still a good finish. - John.

flyranger
12-10-2005, 09:27 PM
Boomerang, what is PVA? Excuse my ignorance.

Boomerang
12-10-2005, 09:55 PM
Hi flyranger, you're not ignorant, it's probably the language barrier!
PVA (poly vinyl acetate) is just what Aussies call white woodworking glue. Is that Elmers over there? I thin it about 50% with water & use it to apply the paper over balsa or foam. - John.

qban_flyer
12-10-2005, 10:34 PM
Thinned down Elmer's White Glue and/or Titebond will do a beautiful job under Silkspan. :)

TLyttle
12-11-2005, 02:42 AM
Here's an example of tissue-covered foam (if it comes through), GWS P51.

Applied with Polyurethane (water based), but I am now looking at PVA. I haven't tried this yet but I figure that if I coat foam with PVA, let dry to a point where the tissue doesn't wrinkle, then iron on the tissue... We'll see...

qban_flyer
12-11-2005, 05:53 AM
It's hard to believe that P-51 to be a GWS warbird. What a superb finishing job! :)

TLyttle
12-12-2005, 02:56 AM
I blush, Qban, thanks for the compliment.

I ain't sure why I spent so much time on that model, one of very few foamies I have built. I sanded out nearly all the panel lines (all you have to do is look at pics of the real thing to see why), and sanded in some washout in the wing/ailerons. The markings are Canadian except for the ID letters, again taken from full-size pics (lets hear it for inkjet printers!!). I think I added some weight (it is at the top end of recommended limits), even though the coats were very thin. Finish is Humbrol silver, which is too glossy for a service aircraft.

Haven't flown it yet; it will fly with no l/g, stock gear, no rudder grass field). I hope that the clean, stiff surfaces and washout will help it fly okay.

inedesca
12-14-2005, 03:27 AM
Cover it with japan tissue soaked in poliurethane paint.

Later if you want more strength cover it with wide tape in the flat parts and finally with water based varnish to give it a general sheen.

Demon-leather
12-14-2005, 03:44 AM
All these finishes sound really heavy.......Do you all just add the amps & watts untill the thing flies? :eek: I don't pretend to know everything about foam, but i'm figuring from MY experience, I want to keep the covering weight to an absolute minimum. Back in the day of my "slimer" past, if we had to cover foam, we did it with Econokote (the only thing that binded to foam due to it's low temp adhesion) Everything here sounds heavier than econokote ever thought of being! Sorry for the fuss,.. I'll sit by & watch from now on.... Bob

inedesca
12-14-2005, 06:01 AM
Demon Leather:

There was a time when electic models were so critical it was very important to keep the weight to the minimum, but in these times with brushless and lipos, not any more. You can afford all of these coverings and still fly 5 to 6 minutes.

Of course the lighter the better, but also the finish and stength are important.

qban_flyer
12-14-2005, 11:39 AM
We have also to consider the fact that the B/L outrunner motors we are now using stress the airframe much more than the motor/gearboxes these models came with, especially the wing.

Tissue and thinned Titebond glue will not only add to the appearance of the model, but will also add some strength with minimal added weight.

My Zero is done that way. :)

cyclops2
12-16-2005, 04:28 AM
Use the Blue Styrofoam. You can hollow it out if you are that weight concious. It has bubbles so tiny, all you have to do is spray the colors on. Films are a waste on it. VERY light cloth, of any stretchy weavy can be used from a fabric shop. Tape the cloth in position and use the spray paint as color and glue down. Practice on scrap to get the hang of the, too simple way of doing foam planes.
I have used the material that is like a wedding veil.
Keep a open mind.:)

TLyttle
12-17-2005, 02:57 AM
Tissue & either thinned Titebond or polyurethane work wonders for stiffness, I figure I stiffened the wing/stab by a factor of 5 or so: watching a warbird flapping its wings on a pullout just doesn't do it for me...

qban_flyer
12-17-2005, 04:14 AM
Tissue & either thinned Titebond or polyurethane work wonders for stiffness, I figure I stiffened the wing/stab by a factor of 5 or so: watching a warbird flapping its wings on a pullout just doesn't do it for me...

HE, HE, HE.

I saw an overpowered P-51 make a few low passes at the speed of light, then turn away to the left three times. Quite a sight, really impressive.:)

On the fourth left turn after another low pass, the wing snapped in half and the fuselage kept going forward at the speed of light.:eek:

Needless to say, everything was totalled!:o

Some of these models are not designed to be overstressed. One has to reinforce them before flying the pants out of them.:D

TLyttle
12-18-2005, 02:01 AM
Yeah, youi don't even need a lot of power. I have a second-hand BN2 with stock gear, and there are a number of wrinkles on the top of the wing... how close is that to failure?

I am seriously considering going the old Ace foam wing trick, ie, run the wing over the tablesaw on both sides and gluing in a length of 1/8x1/8 balsa; I KNOW that wing won't bust, come what may. I know, I tried.

Okay, speed of light, so what's the speed of dark??

qban_flyer
12-18-2005, 04:36 AM
Yeah, youi don't even need a lot of power. I have a second-hand BN2 with stock gear, and there are a number of wrinkles on the top of the wing... how close is that to failure?

I am seriously considering going the old Ace foam wing trick, ie, run the wing over the tablesaw on both sides and gluing in a length of 1/8x1/8 balsa; I KNOW that wing won't bust, come what may. I know, I tried.

Okay, speed of light, so what's the speed of dark??

Why not use a carbon fiber rod instead of balsa? It'll be as light and quite a bit stronger, costlier too!:D

Interesting thing about the speed of darkness! :confused: :confused: :confused:

TManiaci
12-18-2005, 04:47 AM
Ahhhh... you guys all missed the right answer. Use the Hobbico Hobbylite Filler, see it HERE (http://www.hobbylinc.com/prods/rmc.htm).

This stuff is light as air, and is easy to apply and sand. Fills the little imperfections in the foam beading and makes it smooth as silk, with practically no added weight.

If you want an INCREDIBLE finish, cover it with Ultracote after filling and sanding. Make the bird STRON and still keeps it fairly light. There was an article on this in Model Airplane News this early this year...

Bill G
12-18-2005, 04:49 AM
If you would rather use a paint on finish, you could follow what I am doing in the "foamies" section. I am building a watt age Sopwith Camel and finishing it with lightweight spackle thinned with water and whipped with a foam brush to something that looks like pie topping. Sand lightly with 400 grit wet/dry emory paper. Paint with hobby acrylic paint. Spray or brush with minWax water soluble Polyacrilic urethane. I'm using gloss finish. Very little weight added (this is a park flyer, can't handle weight), and the brush marks from the cheap foam brush resemble fabric at about two feet!

The foam on my Wattage Sopwith is very smooth, with little bead effect. Yours should look very good. The depron wings obviously have no bead effect.
The plane can handle a bit of weight, with the wing area. I glued Williams Bros cyl halves to the cowl, to make a simulated engine and add needed front end weight. With a Himax 2015-4100 swapped into the gearbox and a lipo, it is an excellent flyer.

As for coverings, I used Coverite for the first time, and it would probably be great for foam. The temp at which it applies and shrinks is quite low. Also shrinks extremely well.

cyclops2
12-18-2005, 06:31 PM
Tlyttle. I have done that on every foam wing and tail surface since I started with foam. Walmart foames to biggies, always slot 3/4deep into the bottom and have the slot cut to where the flaps and airleron servos can be glued to it for solid and wiggle free action. Cut 2 slots and you can use them for the landing gear boxes also with some ply doublers. Same for servos in the tail.
Thanks for reminding everyone. :)

TLyttle
12-19-2005, 02:49 AM
Yup, Cyclops, it works fine. When I was learning r/c, I built a trainer with Ace s/c gear and a wing reinforced in that manner. One flight took the model into a thicket, towed by a flat-out Cox 049; I found the model, and the only damage was to the wing up to the spar. A branch had cut into it, and stopped at the spar, plus the fuselage. When I got to it, the engine was still howling away.. Damage or no damage, I flew it again that day, slice and all!

Hey, Qban, C/F is lovely, if you happen to be near a place that sells it; in my case, that isn't the case, so I depend on my balsa supply or the lumberyard for reinforcement like that. Also, the shot about the Speed of Dark comes from a series of philosopher's absurd questions...

zwibelturm
12-19-2005, 09:05 PM
This thread has helped me. I have a SIG Bristol Scout. The "beady" soft fuse responded well to a slurry of light weight balsa filler (light weight spakle also worked). 240, 320, 400, then 600 sanded it smooth in a hurry. I covered just the fuse with very light 3/4 oz fiberglass cloth. I first sprayed the down-side with 3M spray adhesive so that it stayed put, then sprayed it with thinned finish-cure 20 minute Epoxy. Everything else got sprayed with Future floor shine right from the bottle with my airbrush. It dries fast, seals well, and cleans up with soap and water. Then I sprayed on acrylic colors, did a little masking and weathering with that powdery eye shadow (Covergirl cost little and brushes on). Another coat on Future, decals, and a final coat of Future to seal them on.
The wood parts were stained with dark maple polyurethane. Plastic parts got acrylic paint and a coat of Future. The wings needed only acrylic color and a coat of Future. This thing no longer resembles the ARF it is. The instrument panel, cockpit combing, elastic thread rigging and scratch built landing gear helped. I added ailerons and used two little DuBro bellcranks connected to a single hitec HS-55 with skinny carbon fiber rod from Hobby Lobby. Also replaced the rudder and elevator pushrods with CF rod. The wings were reinforced with 1/8" CF spars with 1/16" CF LE's. I used a short 1/16" rod to protect the TE from the rubberbands. Replaced the stock motor with an AXI brushless and powered it with an 830mah LiPo. The Williams Bros Vintage wheels help with the CG.
Guess I got carried away...

TManiaci
12-19-2005, 10:17 PM
Well let's see some pictures! :rolleyes:

zwibelturm
12-20-2005, 02:53 AM
Ahhh, pictures... of course. I'll take some and post 'em.
John

hoppy
12-20-2005, 03:09 AM
How much weight did it add?

cyclops2
12-20-2005, 08:51 PM
I tried out a smear of the Minwax Polyacrylic on Blue Foam in a 40 F garage.
Funny. It softened the surface but did not melt it.
No touch or push ,no appearant dent. Give 2 days in the garage to really dry. Then check.

aethertek
12-21-2005, 04:36 AM
The best filler I've found for foam. Woodland Scenics SUBTERRAIN Foam Putty, you can find it at railroad stores, its usually used for dioramas