DReigard

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What happened to covering models with silk ? I'm building the Spook 96" with parts from Klarich and plan to cover in white silk and paint the trim only. I'd like to see this thread as a tips thread for covering with silk. I'll post pictures and details of my covering job when I get there and hope anyone else who uses silk will post pictures with details of thier model and techniques they used. I'm afraid this is on the verge of being a lost art because you rarely hear about it being used anymore. I hope to learn a few pointers and hopefully someone else will too. When you hear about someone covering with silk does it sound kind of mysterious ? If so, then thats a good reason for this thread.

Question 1 - after getting the silk on around the edges how many coats can be applied over the open areas before sprayed coats go on so as to not see brush marks ? Or, do all the coats get sprayed on ?

Thanks for taking the time here folks !

pd1

Here's a couple of things I've found out about silk and dope.

Nitrate can't be applied over butyrate. It will react and ruin your finish.
Nitrate is very flammable compared to butyrate.
Nitrate has a little better adhesive qualities compared to butyrate.
Nitrate requires additional fuel proofing.
Nitrate stops shrinking after a couple of days.
Butyrate shrinks for a long, long time.

Covering. I don't use nitrate anymore, personal preference, so to increase the adhesiveness of the butyrate I coat the bare structure with butyrate until the wood picks up a shine.

Then apply my silk. Spray the silk with water and get the wrinkles out.
I use a lot of thinner with just a little dope to stick the silk.
The thinner passes through the silk and softens the dope underneath sticking the silk down.

If you accidentally get some of the thinned dope on the silk, there is not enough dope to curl the silk.
Thick dope will curl the silk as it drys.

Using dope while the silk is still wet will cause the dope to blush. It will actually turn white.
Let all the water dry off the silk before doping too much.

If it is a day with high humidity, the dope may blush again. A couple of drops of retarder will stop that.
Sig sells retarder in small bottles.

If you hold a wing horizontal while doping, especially with dope that hasn't been thinned a lot, the dope will drip through and make an ugly ''ring'' on the other side of the wing.

To avoid that when doing wing panels, just use very thin dope and hold the surface vertical.
The thinned dope will not leave a ring, and if the panel is vertical the dope will stay on the side you are doping.
On the last couple of coats of clear I add a couple of drops of Castor oil to the clear dope. It will act as a plasticizer and will slow dope from drying out over a long time.

Silk. I've found that there are at least two different silks that shrink different from each other.
The silk from Thai silk seems to be pre shrunk and doesn't shrink much if at all after covering.
This is good for delicate structures.

http://www.thaisilks.com/product_inf...22fba3399425a4

The silk I like from there is the 5mm 021F-000 Habotai.

If you want silk that shrinks more, the silk from Dharma Trading is for you.
It's great for stronger structures.

http://www.dharmatrading.com/html/eng/3374-AA.shtml

I use the 5mm. HS536 or the HS545 same but 45 inches wide.

I've found the 5mm silk is lighter than any other covering, including tissue and the weave is so tight that it doesn't take much clear to fill.

Before you ask,mm is not milimeters. ''MM is Momme.
Momme (pronounced ''mommy'' and abbreviated ''mm'') expresses the weight in pounds of a piece of material of size 45 inches by 100 yards. So, for example, a 50 yd. bolt of our 5mm 45'' Habotai Silk fabric (#HS545) would weigh 2.5 lbs. (plus the weight of the cardboard tube it is wrapped around, of course).
The higher the momme, the heavier and stronger the fabric. Anything above 28 momme is considered heavy-weight and generally used for curtains or heavier outer-garments. Silk under 20 momme is considered lightweight, and generally used for light blouses with a chiffon feel. Medium-weight silk (20 to 28 momme) is excellent for silk scarves, furnishings, wedding dresses and the ultimate luxury of silk sheets.'' Dharma Trading.


5 mm silk is extremely light.
A sheet 45 inches wide by 300 feet long would only weigh 5 pounds.

Drying out and rot. Unless you leave the silk in direct sunlight, the silk won't rot.
What actually happens over time the dope becomes hard and brittle. The silk is saturated with the dope and when the dope cracks, so does the silk.
I just started removing silk that was applied 40 years ago. The silk is fine, the dope isn't.

Silk has a "grain" to it. It usually has a finished edge on one side of the piece. The grain is parallel to that edge.
Run the grain spanwise on a wing across the ribs.
If you run the grain chordwise, with the ribs, the silk will pull down between the ribs and look odd.
Silk shrinks more with the grain than across it.


If you thin dope sufficiently, and use a good brush, it will not leave brushmarks.
I use a camels hair brush, most hobby shops carry them.

Michaelj2k

What Paul said. Randolph/Brodak market a retarter that you use with pigmented dope. It slows the drying, making the dope finish nice and glossy.

OT: Paul, there's a package in the mail for you.

buzzard bait

Nice post. I used Thai Silks on two planes because of the nice colors they have, but I got very frustrated trying to get it tight enough. I applied it wet, pulled it tight as I could while I doped it down, used tautening nitrate for the first coats, and after about four coats it got tight enough. I am eager to try Dharma silk instead because I will never use pre-shrunk again.

But how did you get that nice red color? I thought the Dharma only came in white. Did you dye it?

Regarding old silk and dope, I have had a bit different experience. It seems fine after 40 years if you keep it out of the light or use silver dope. Without silver, a few seasons of UV exposure destroy it, even with color dope and even if the dope is still pliable.

Jim

Doc.316

Ok, I am a newby at this dope business, but have been asking a LOT of questions. Here is a tip I got yesterday from one of the local guys that I have yet to try but will shortly. (and he build absolutly beautiful models). He said to take a permanent marker, pull out the er soggy roll thing in the middle, soak it in a jar of thinner untill the thinner is dyed, Mix that with your clear dope to create any color you want. The color on his models is a very beautiful translucent covering job.

Oh, btw I like this thread since I am now trying to cover with dope.

Steve

pd1

Leaving a silk covered plane in direct sunlight will rot the silk.
You can give a couple of coats of silver to the plane before the color.
This will help in blocking the UV rays.
I just keep my planes in a room with the shades drawn.

Dyeing silk
When I first started building you had only two choices for covering, paper of sorts, or cloth of sorts.
Both needed to be applied and shrunk.

Today there are a lot of plastic films that look great, and shrink with heat.
But the "look" is different.

I always like the look of a plane with silk and doped finish.
I like colored silk with clear dope with maybe some trim with silk or colored dope.

The silk that's available today is different from the silk of old.
1. Colored silk is harder to find, and costs more.
The worst part is, the colored silk I have found was heavier and refused to shrink like the lighter white silk.

I've been using 5 mm Habotai silk from Thai Silk, recently I ordered some from Dharma as well.
It works well, but only comes in white.


Now to the color part.

I've been told ,"you can't dye silk without a special process".
Once way back when I tried with the little packages of Rit dye.
I made a mess and the silk was all streaky and not colored evenly.

I read the process at Dharma and it basically told of a long and involved procedure to color silk.
http://www.dharmatrading.com/html/en...l#instructions

My wife said,"try this". She handed me some new Rit liquid dye, and an old pot.
When I finally got up the courage to try it, I was amazed.
I didn't make a mess and the silk took the dye evenly through out.
All I did was follow the instructions on the back of the package.

Basically add the liquid to hot water and let simmer on the stove.
Add the wet silk and stir for thirty minutes.
Rinse with cold water and wash with some detergent, let dry.

That's it. Here's a few pictures of the colored silk.

I used to add tints to the clear dope to make a deeper color without using colored dope.

Maybe the maker pen might do the same.

My Minimaster is died silk with just clear over it. If you do dye silk, be extra careful, you have to wash the silk and extra time to get the excess dye out.
If you don't you will see the dye come off onto the brush and contaminate the clear.

Not a problem until you try to paint color over it.

If you look close at the wingtip in the first picture you can see the dope shine on the balsa. Now it's ready for silk.
I cover the wing and trim to a rough size dry.
Spray water and soak the silk.
Dope the edges and let it dry.
The red I used bled right through the colored dope.

N1EDM

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PD1,

Nice jobs on all of those planes. I'm jealous!

One question... when you put the silk into the hot water and dye, doesn't that make the silk pre-shrink? As you can tell from the naivity of my question, I've never tried this either though I've been dying to.

Thanks,

Bob

pd1

I think it does shrink when it is put in the hot water.
When the silk is re wet during application, I think it stretches out again.
It shrank fine after it was put on.

Paul

DReigard

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PD1 - Thank you for the help ! This is exactly what I was hoping for on this thread !
I bought the sample pack from Darhma, I want to try the flat crepe part # FR45, the details on this one say it readily accepts dyes and paints. It also has a nice gloss to it and I think it would look really good. The Spook with a 96" span I'd feel more comfortable using the 8 MM.
http://www.dharmatrading.com/html/eng/3413-AA.shtml

When thinning butyrate does one have to use butyrate thinner or can acetone or denatured alcohol work ? I'm guessing you'd have to use butyrate thinner huh. If so does butyrate thinner work with nitrate dope too ? I'm also thinking a very large brush would benefit too.

Good looking planes PD1, I bet silk looks awesome in person !

big max 1935

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I have dyed both silk & silk span paper over the years & after it drys & you wet it again it goes back to the size you started with.
You guys are going to think I am nuts but the BEST way I have found to fill the weave on the silk is to use the dope with out thinning (or very little thinner) & a piece of a T shirt. Lay the cloth at the wing center section & saturate the cloth with dope & then pull it down the wing while you keep putting more dope on the cloth . This really works & you will not get drips inside the wing . Take your time & you will fill the silk in one coat . I have never sprayed clear as the brush marks leave after it drys good . Have fun , Max H.

Jim Thomerson

Sig markets one thinner for both their nitrate and butyerate dope. Randolph, etc. markets different thinners. If you want to experiment make a test piece to see if things work rather than messing up a model. I use the old Esaki type silk. (I have some packages which sold for $1.95. Guess how old they are.) You can get Esaki type silk, in colors, from free flight suppliers like Aerodyne, Campbell's Custom Kits, Peck Polymers, FAI Supply, etc. It is expensive, near $20/yard, but I'm worth it!.

pd1

There are a lot of thinners that will reduce the viscosity of dope.
I will use lacquer thinner for clean up because it costs less and it's available locally.

Years ago I ran into compatibility problems between Testors dope and Aero Gloss.
Since then I've tried to stay with dope and thinners that I know won't react with each other.
That's one of the reasons I don't keep Nitrate around anymore.

That's the main reason I use butyrate thinner only with the dope.
Your experience might vary.


Using dope full strength. 40+ years ago I built a plane for Lou Andrews. He lost orientation on it and it went through the trees wrecking one wing.

When he fixed it he found the wing I did was much heavier than the repaired wing.

When the wrecked wing was looked at closely, we found the dope I had used hadn't penetrated the silk very well.
You could peel the dope off of the silk quite easily.

I had used the dope nearly full strength. It was noticeably heavier than the thinned dope for the same finish.
Don't know what other problems this might had led to, maybe cracking over time , since then I've thinned all my dope.

Paul

DReigard

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Hi Jim, a fellow Texan, nice ! However, we all know Houston is the capital of Texas right ?   I picked out the dopes I'll be using from Aircraft Spruce here - http://www.aircraftspruce.com/catalo...nrsolvents.php
If you have silk bought for a buk 95 I'd say it's been around your place a while ! Are you a builder of Old Timer types ? I'm excited about getting started on this Spook, I'll be building it with a straight wing as I'm looking for flight performance rather than the kool gull wing look. I know alot of the Old Timer guys are kringing right now but I'd rather have a good thermal ship too. If you havent built a Spook yet order the parts and plans from Klarich, it's an impressive looking model on the plans and built like a tank. I hope to pass this one on to my grandson one day. It certainly is strong enough an airframe to stick around a while !

DReigard

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Paul, I'll bet if that model was covered with an iron on product the damage would have been alot more extensive. I've been handling this sample patch of silk and man this stuff is strong ! I'm taking your advice and will spend the extra few buks to get the thinner too. I'm also guessing I wont be using iron on's very much anymore.

pd1

Silk is really strong but years ago we used nylon because it was cheaper and stronger.
When the planes crashed the nylon didn't rip.
All the balsa was broken, and you had a nifty nylon bag to carry the scraps in too.

There are a lot of people around here that have a lot more experience at this than I have.
Hopefully they'll add to the thread too.
I can only report on what I've done and the mistakes I've made.

I tried the 8mm silk and I like the 5mm better. It seems strong enough.
I have it on an Aeromaster and it is holding up just fine.
I'm not gentle with the plane and it's still in one piece.

Paul

frequent flyer

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I used to use nothing but silk and dope until the day that they became brittle and my beautiful planes began to puncture. Never again will I use silk. I have been using Sig Koverall and stik it to secure it to the frame work for decades now and is much stronger. Plus you can heat shrink it and then apply your dope just like silk. Live and Learn.[8D]

TCraft Lover

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Man what a great thread!! I have one question though. I'm going to begin constructuion of a Sig Smith Miniplane. I think I'm going to cover it using theStix It andKoverall method. I want to use Butyrate dope to shrink and fill but how much will I need andwhat thinning ratio is appropriate?The wings are 650 sq. inches and the fuse is proabably about the same area or a little more.

Jim Thomerson

DReigard, I'm flying control line Old Time Stunt Airplanes; designs from before the end of 1952. I haven't used an iron on in some years. Silk, slikspan and tissue depending on the airplane.

frequent flyer

My Feedback: (6)

If you use the koverall and stik it you brush a coat of stik it on the all the wood,let it dry. After it has dryed you lay the koverall over the area , lets say you're doing a wing, lay it over the wing and with a covering iron you iron it on the edges and it will stik to the stik it, it is heat activated glue. I pull it gently just to get it to lay wrinkle free. After the area is covered and sealed around the edges I proceed to iron the rest of the wood areas. Now it's really stuck down. Then you can use your iron or a heat gun and shrink all the rest of the open areas. It shrinks just like iron on coverings even better. You'll love this stuff. Then I coat it with a couple of coats of Nitrate Dope. Now at this point you can do anything you want to finish it. You can use butyrate Dope or auto primer and automotive paints , spray cans or whatever you want for a finish. I use PPG paints and sometimes Butyrate Dope. The auto paints sometimes will crack if you wing is not fully sheeted. On those type of wings I still use Dope.

TCraft Lover

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Hello FF,
Does nitrate dope have any advantages over butyrate? It seems to me that I would be better off just using butyrate to fill the weave.

Doc.316

Hey, I gotta question....Can vinal stickers be used over silk/silkspan covering? If so will the thinners in the dope clearcoat eat them up? I was looking to make some up on my inkjet printer to replace some waterslide decals in an old kit....the old ones aren't useable as is.

Thanks
Steve

pd1

Nitrate has slightly better adhesive qualities.
It is a little easier to stick silk or paper onto an open framework with nitrate.

Nitrate stops shrinking in a couple of days to a couple of weeks.
Butyrate shrinks." like forever".

My personal preference, a lot of people will disagree, is I only use Butyrate.

Fabric or paper doped in only nitrate will burn a lot faster and intense than butyrate.

pd1

I have vinal stickers on some of my planes. I haven't tried to clear coat over them though.

I have clear coated over decals though. Try a test piece first. For the most part no trouble, but I have had some wrinkle up.

Doc.316

Thanks PD1! I was going to try it before I put them on the plane. I guess I wouldn't have to clearcoat over them I could clearcoat before I put them on. My main concern was that the dope finish could shrink/expand with time but the vinal probably won't. I can find some waterslide decals for the inkjet but I have to order them off the net...and office depot is closer.
Steve

WEDJ

I believe that vynal over silk/dope is fine - look at this photo of the AMA numbers...