Silkspan, 3 blade prop, Paint ???

I am about ready to cover the wings of my F-Twister with something???
I have an idea to cover the open area of the wing with EconoKote for strength lap it about 1/2" on the balsa then cover over the EconoKote with silkspan so I can paint the airplane. The silkspan will be stuck tight to the balsa all the way around the econokote. I know it won't stick to the plastic film. I am trying to find a way to make the silkspan stronger and still be able to paint the airplane. Has anyone tried this?

I have swapped out the OS 25 engine to an OS 40 engine. I have reduced the airplane weight by about 3 ounces. I would like to paint this airplane but my experence with paint is not good. Balsa soaks up paint like a sponge soaks up water. Water base latex paint works great but show the wood grain real bad. Two part epoxy paint looks nice and stays nice but probably adds a lot of weight to the airplane. Spray laquar car paint from Auto Zone works great but it takes many coats of paint to get a good shin its probably heavy too. Is there a trick to painting balsa? How much weight will paint add to the airplane compaired to EconoKote? If I use dope it will have to be ordered the hobby shop does not have it.

I would also like to try a 3 blade prop. I think a 4 pitch will be about the correct air speed but what about the diameter for an OS 40LA engine?

>I am about ready to cover the wings of my F-Twister with
>something???
>I have an idea to cover the open area of the wing with
>EconoKote for strength then cover over the EconoKote with
>silkspan so I can paint the airplane. Has anyone tried
>this?

No- but it almost certainly won't work. Next to nothing wants to stick to the film, and that includes dope and most other likely adhesives. Plus, Econokote will do nothing at all for the overall strength of the wing, far less than silkspan. It's probably slightly less prone to getting holes poked in it, but not that much.

The other way around (silkspan, then Econokote) would work better, but I think you would be FAR better off just using GM silkspan and dropping the econokote entirely. If you absolutely must, use Polyspan, which is pretty much bulletproof as far as holes go, and is easily paintable, assuming you don't get overly concerned about the fuzzies.

As a follow up to Brett, use the silkspan to cover the entire plane.
The wing will be stronger, and the balsa will take less paint to fill when it's all covered.
A decent job will take about 3 coats of clear on everything to start with. Sand with 320 after the 2nd coat.
Cover everything next. On the balsa areas: 3-4 more coats of clear, sanded when dry after the 2nd coat. On the wing, about the same, but the sanding will not be needed on the open bays. The plane should now have a slight sheen to it. To keep down the weight I would go ahead and color coat the plane then shoot a couple of thinned (50-50 or more thinner) coats of clear when you are done with the color. Using filler on a plane that is already heavy will not do much good.
As to a 3 bld. prop, I have not noticed anyone as of yet using one. If I were to, I would start with a 10 in. diameter.
Bill <><

I'll add my two cents to Brett's and Bill's messages:

I thin the dope big time when I'm sealing and filling silkspan. I use 2 parts thinner and one part dope (67/33). It takes a few more coats, but it's much easier to brush this on. Plus, all the thinner will evaporate.

Use really good quality brushes and keep them clean.

Hey - it's all a "Learning Experience" anyway

I have used silkspan under monocoat. This looks pretty good under transparent monocoat. I Have covered a number of airplanes with Sig Plyspan and find it to be very tough. I have read several articles in Aeromodeller on covering with thin mylar then doping, with one thin coat of dope, tissue over it. This gives, for a rubber model, a lighter coveing than adequately doped tissue. The tissue has to be doped down carefully not to let any air bubbles between the film and the tissure. I have not tried this myself. Someone had an Icarus in Vintage Stunt with the wings covered this way and was DQ'd for nontraditional covering (that's the British way, I suppose.) I'd suggest making a test panel and seeing what happens. From what I have read, it will take less dope to fill the silkspan and the dope will take a long time, relatively, to dry.

I haven't actually tried Silkspan over Econocote. I think it is a different material than Monokote. Try a test panel first to make sure it will stick OK.

Silkspan can go over a polyester covering(CoreHouse SLC, Monocote, Ultracote) if you use water-based polyurethane to stick it down. Works pretty well. The film gives quick , solid base, the silkspan lets you sand it smooth and get a good base for painting. Make sure the film is clean. Use solvent on it and maybe buff it lightly with a green Scotchbright pad.

Quite a few people are simply painting directly over the film. One coat of primer, then color. I think Remi Beringers plane at the WC's was done this way. You would need to take a lot of care with the structure underneath to get a really good finish, since every little flaw in the wood would show through the film.

Several of the Europeans are using polyester film first over the open sections to get a good base for silkspan, reduce the amount of dope needed, and help back it up against hangar rash.

Bret says no and Phil says yes.I agree with Phil.I did this with a product that ANSCO use to make and it worked very well and I got it free as I worked for Ansco in Johnson City NY in the 60's.I still have a large stunt plane from the 60's that was covered that way.
Ed
Well I went back and found a picture that I took a few years ago of my 37 year old Fox 59 powered Jet stunter. I flew this plane in the very first classic contest on the east coast many years ago. When I made a repair on it a few years ago the clear film had turned to white dust and large pieces of it can still be heard rattling around inside the wing. I got it out to fly at Hunterville last month and the guys would not let me fly it until I make some planes for it.It flies very well.
Ed

>Bret says no and Phil says yes.I agree with Phil.I did this
>with a product that ANSCO use to make and it worked very
>well and I got it free as I worked for Ansco in Johnson City
>NY in the 60's.

I know for certain that dope doesn't stick well at all to Econokote, since it all chipped off my Tutor when I did it. Certainly not well enough to count on for structural purposes.

Polyurethane is pretty good, but I don't think that sticking down silkspan with polyurethane will work too well.

Certainly skipping the double-covering and just using polyspan instead is far, far easier.

>I would also like to try a 3 blade prop. I think a 4 pitch will be about correct.

The 10-4 black Grish Tornado might work fairly well if you can find one. Otherwise the 11-4 APC should be good.

I never really understood the reason to cover the $$kote with silkspan. If you are going to $$kote the wing and stab, then $$kote them and forget it.

As to painting the wood surfaces, the wood grain must be filled before painting. I use nitrate dope, cover wood surfaces with silkspan, and fill everything with nitrate, sanding as you go and final color with Rustoleum spray which works very, very well. Rough up the kote with scotchbrite pads where the Rustoleum overlaps the kote.

You can skip the dope and silkspan on the exposed wood surfaces and try filling with Rustoleum gray auto primer sprayed on as you don't have dope available. It will probably take several coats. Wet sand between coats.

As to Econokote, never liked the stuff. Try Towercoat from Tower. Cheaper and easier to work with for a low temp cover. Better still spring for the extra 3 bucks and use Ultracoat. More colors, easier to work around tips than monokote or econokote.
It also takes less heat to shrink than monokote.

The down side of Ultracoat
is that it does not stick to itself as well as monokote so any seams are likely to pull apart just as you are applying enough heat to shrink perfectly.

The LA 40 will turn a 10/4 3 blade prop quite nicely. ~10,500 rpm, with a .262 venturi and OS needle valve assembly.

The Tornado 10/4 works fine. It tends to make a wierd whistling sound, but flies a cardinal well. The Master Airscrew 10/7 depitched to 10/3.5 does a good job also. It seems to be more "efficient" in that the plane needs to launch ~1000 rpm slower, around 9300. Make yourself a simple jig to check the prop pitch. I used a 10.5 deg. wedge set at 3 in. from a short piece of 1/4 in. dowel. Heat the root of the blade for 20 sec. at a time, front and back for a couple of minutes. Give the center of the blade a healthy twist, and put it on the guage. Twist is back if needed to get the bottom of the blade to just kiss the wedge, and let it cool.

I know this depitches the tip to ~ 1-1/2 in. pitch, but it seems to fly fine. You could extend the jig to 10 inches and make a second wedge to repitch the tip up to 3.5 if you want. You can also spend months playing with the prop pitch and pitch distribution.

BTW, Master also makes a nice looking 9/7 3 blade, and an 11/8 that could easily be repitched.