Silk and dope - How do I know I have enough coats?

[Unclebuck21228]

I am recovering and converting to electric a Sig Kadet Seniorita I built 20ish years ago. I removed the monokote and have recovered the wings (so far) with habotai 5mm silk and Sig nitrate dope. I am fine with a semi gloss fabric finish but how do I know when the weave is filled enough for flight? I lost track of how many coats are on it.

[CHELLIE]

Originally Posted by Unclebuck21228

I am recovering and converting to electric a Sig Kadet Seniorita I built 20ish years ago. I removed the monokote and have recovered the wings (so far) with habotai 5mm silk and Sig nitrate dope. I am fine with a semi gloss fabric finish but how do I know when the weave is filled enough for flight? I lost track of how many coats are on it.

If the weave is sealed enough to where water cant go through it, its sealed enough and if it looks good and your happy with it, then go fly it balsa, tissue paper and dope builder here for over 48 years here, Take care and have fun, Chellie

[fhhuber]

For electric power... 2nd coat its ready to fly. You don't have to fill the weave watertight.

Glow or gasoline... or if it has to deal with water... then you have to fill the weave watertight.

So when you are happy with the looks its good. No need for adding weight with extra paint.
But the Seniorita can handle a lot of weight if you want to go for a glassy finish.

[soarrich]

I keep shooting clear coats on until:
I don't have any blush, retarder helps.
I want a smooth finish, if you have a pronounced fabric look it will get dirty looking quickly.

[pd1]

As said before, enough coats to fill the weave and the covering is ready for flight.

My personal preference is for a shiny smooth finish.
After the weave is filled I use more coats of dope, thinned about 50-50. Wet sanding with 400 grit paper in between every other coat of dope. Be careful, it is easy to cut through the silk at the juncture of open ares to wood.

When the area sands to an even dull look, a couple of finish coats of very thinned dope will give a shiny finish. One or two drops of castor oil in the dope will act as a plasticizer and increase the shine.
I've only used the castor oil with butyrate, try a test if you're using nitrate.

I've seen a few planes that used Krylon Crystal clear in the rattle can for a high shine too. Problem is you can't go back to dope afterwards.

[fhhuber]

I have done rubber power Free Flight with silk and dope... Weight matters there. Fewer coats means less weight but it does mean a bit more difficulty cleaning. (but not much cleaning without an oily fuel)

I have also done a 50 coat mirror finish, progressing from sanding sealer coats to silver then color, then clear... with sanding progressively finer grit paper (4000) and automotive rubbing compound. (probably sanded and rubbed off 3/4 of paint applied)

That's the extremes possible.

The end result just has to please you... The builder and owner of the model.

[fhhuber]

BTW... the purpose of 2 coats of silver under the color is to protect the silk from UV which will destroy the silk.

[Unclebuck21228]

Thank you all for sharing your knowledge. Right now for this model Im after air worthy with a traditional finish. I did a terrible job on color selection before and had to repair many years of hangar and moving rash. It dosnt have to be perfect, more of an experiment.

Pd1 you initially inspired me to try silk and dope. Thank you because I find it a very satisfying way to cover. Next project I plan on dyeing the silk. I'll get to the shinny finishes later.

Dan

[fhhuber]

thaisilks.com... get it pre-dyed.
Give them a hint of the color you want and have em send samples. They send a bunch of appx 2 inch squares.

Dying silk is a pain in the neck. It loves to come out uneven. The factory process is consistent every time.

[pd1]

Unclebuck, thanks for the comments, glad you project is coming out the way you want it.

The silk from Thai silk and the silk from Dharma Trading work differently.
Thai silk is great for over solid surfaces like sheet or foam. Thai silk is preshrunk so it doesn't always shrink up tight over open areas.
I started with Thai silk and switched to Dharma Trading brand and have had great results.

I too like a couple coats of silver as a base color before adding final color.
The silver gives an even color for the base and less of the final color is needed. Also the UV protection is a big plus as mention by fhhuber.

I've also been dying silk and have had no problems with the color coming out rich and even. I haven't tried dying Thai silks and that might be the difference in outcomes.

[soarrich]

Originally Posted by Unclebuck21228

Next project I plan on dyeing the silk. I'll get to the shinny finishes later.

Dan

This is interesting:
http://www.airfieldmodels.com/inform...wing/index.htm