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Building Tips and technical articles. => Paint and finishing => Topic started by: Jerry Rauch on December 15, 2009, 06:27:18 AM
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Has anyone ever tried this? Cover a wing with silkspan, one coat of clear dope, then cover with silk. That way you get the strength of silk, but you don't get the drip thru problems with the silk. The reason I'm asking is I covered 2 wings with silk, one with cap strips looks good with the exception that the silk is stuck down slightly along the inside edge of the wing tips, probably due to slightly sagging there at the edge. The other without cap strips, the silk is stuck down very slightly all around the top edge of the ribs and stringers. It doesn't look real bad, it just looks like the silk is extremely tight, when it's not. Seems like I never had these problems years ago (40) when I was a teen and built planes. I'm covering with 8 mome Chinese silk, and Sig taughtening dope thinned 50%, and I tried putting it on as light as I could. I was wondering if Japanese silk does the same thing, but it doesn't look like Sig is getting any more Jap silk.
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Jerry, the free flight scale bods have been doing that over here for years!!
Check out www.freeflightscale.com then go to the technical tips. The difference is that they use wallpaper paste to adhere the silk to the jap tissue!! Read the article, you'll see what I mean?
Cheers Neville
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Jerry,
I use the very thin mylar that the freeflight boys use. I stick this on using much diluted impact adhesive. I then shrink the mylar using a hot air blow gun. Don't overdo this otherwise you will get holes appearing, guess how I know! Just a gentle shrinking is all that is required. Then cover with favourite silk and spray on diluted dope, a couple of coats is all I use. The resulting covering is lighter than using silk and dope (no blow through) and the mylar seals any air leaking through the silk. Its very tough and very light. I have added pigment to the thinned dope to get colouring, but don't ask what the pigment colours are. I hoarded them from a past life in lighting (Coloured laquer for PAR 64 lamps). OK its not concourse and needs fuel proofing, but its good for a light plane!
Regards,
Andrew.
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I did it on the stab and elevator on my Humongous after I recovered it. Those parts are kind of flimsy, and it was flexing to much and broke my cloth hinges. So I recovered it with med, wt. silkspan, and then with 5mm silk. Worked very well, and it made it much stiffer than with just silk. Bill Heyworth told me that he uses tissue under silk.
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Right now I'm painting (or trying to), an RSM Thunderbird. It's like a comedy of errors...one thing after another...some things I've learned
1. Do almost ALL sanding, fillercoating,etc. of separate parts, fin, rudder,stab, flaps, fuselage, BEFORE assembling
2. DON'T try to sand silk thats over an open bay
3. DON'T wet sand a wood airplane, even if it has 6 coats of clear and 2 coats of color
4. I must be going blind...I thought it was close to ready for paint...not even close...
I'm sure I'll learn a lot more before this thing gets painted, (if it ever does)
I've now broken the fin and rudder off 4 times!
Every time I sand on this plane I either put another hole in it, break something, or in general create more work to do.
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Right now I'm painting (or trying to), an RSM Thunderbird. It's like a comedy of errors...one thing after another...some things I've learned
1. Do almost ALL sanding, fillercoating,etc. of separate parts, fin, rudder,stab, flaps, fuselage, BEFORE assembling
2. DON'T try to sand silk thats over an open bay
3. DON'T wet sand a wood airplane, even if it has 6 coats of clear and 2 coats of color
4. I must be going blind...I thought it was close to ready for paint...not even close...
I'm sure I'll learn a lot more before this thing gets painted, (if it ever does)
I've now broken the fin and rudder off 4 times!
Every time I sand on this plane I either put another hole in it, break something, or in general create more work to do.
Jerry, what's the problem with the wet sanding? I wet sand by the gallon once there is covering and dope on the plane. I wet sand all the primer off and the clear coats.
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It appears where the edges of the fuselage top planking meets the sides is now raised. Maybe the moisture got thru, but with 6 coats of clear I thought it would be sealed.
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George Aldrich clued me in as to how to dope silk. First, use a foam brush. Dip only about a 1/4" of the tip into the dope. Draw the brush LIGHTLY across the panel until the brush runs dry (a remarkably long way!). If you get drip through, turn the wing upside down and brush the area a couple of times. This will draw the dope back OUT!
As in may other things ole' George knew what he was talking about!
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Jerry, the latest stunter that I'm finishing, has been a complete disaster HB~> At one point the masking tape I used pulled everything off down to the bare balsa!! I've had fillets cracking, and various other problems, its nearly been thrown in the bin on three occasions!
I think everything is sealed and stable at the moment, so I might paint it over the Xmas holiday? I'll send photos when its done. It seems to be getting heavier every time I look at it! ;D
Cheers Neville
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I've broken the fin and rudder off so many times, now I have to replace it, it's so screwed up....the patch on the wing where I sanded thru looks like hell...what next???
I know one thing, I'll NEVER brush any color onto anything again. Sig supercoat, thinned 25%, with a new Sig 3/4" brush..brush marks everywhere, lots of sanding to clear up.
"Experience is a cruel teacher"
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I thin most Sig colors for brushing at 60 to 65%. Takes several coats, but leaves no brush marks to speak of. I also brush on the final clear coats thinned the same.
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Jim, can you explain the type of thinner you use? A good quality thinner makes a huge difference to the brushability of dope! A cheap thinner makes it impossible to brush. Here in England, you need a mortgage to purchase decent high gloss thinner, the last gallon I bought was £25.00, about $40.00, and that was supposed to be trade prices!!! As you say, there are no brush marks and you get a super finish.
Cheers Neville
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Right now I'm painting (or trying to), an RSM Thunderbird. It's like a comedy of errors...one thing after another...some things I've learned
3. DON'T wet sand a wood airplane, even if it has 6 coats of clear and 2 coats of color
I got this tip from Windy several years ago and have mostly used it since. Wet sand using a degreaser prep wash and not water. I use Napa #6384. Get it at the NAPA auto store. Put in spray bottle and use as you would water, but you don't have to use very much. Just spray small amount on surface, sand, then wipe up. Only need to wear gloves and do in a ventilated area. But there is no chance of wood swell and is very easy to keep up with sanding progress. Jim
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I have found that "rattle can" Painters Choice sprays well, flows out, and is fuelproof up to about 15%. I have put it over Nitrate, Butyrate and clear water-based (Minwax) polyurethane. You need to sand the base coats to assure adhesion.
As always, I recommend doing test panels for ANY planned finish. Surprises await, sometimes based on the color used. I do my panels on scrap corrugated box cardboard. Very cheap! Mark on the back of the panel what the sequence of paints was, and then stash it away for future reference.